Degradable EVOH high-barrier composite film

Abstract

A degradable EVOH high-barrier composite film, characterized in that the materials of various layers in the composite film all obtain approximately-consistent biodegradability by introducing biomass, and the additive amount of the additive master batch in the materials of each layer is controlled within the range of 0.3-15% of the total mass of the materials of the corresponding layer; the hydrophilic activity of the hydrophilic groups in the additive master batch should be greater than or equal to that of the hydrophilic groups in the materials of each layer; by adding the additive master batch, the mole ratios of the hydrophilic groups to carbon atoms of the materials of various layers tend to be consistent, namely, the bioactivities tend to be consistent, so that the degradation rates of the materials of various layers in the composite film tend to be consistent. The present invention makes contribution to obtaining approximately-consistent bioactivities and approximately-consistent biodegradation rates by balancing the mole ratios of the hydrophilic groups to carbon atoms in the materials of various layers, and the appearance, the functions and the physical and mechanical properties of a product remain unchanged.

Claims

1. A degradable EVOH high-barrier composite film comprising: (A) an outer layer comprising a polyester containing a hydrophilic ester group, the polyester comprising at least one of polyethylene terephthalate or poly(ethylene terephthalate-co-1,4-cyclohexylenedimethylene terephthalate); (B) a first adhesive layer comprising a maleic anhydride-grafted ethylene acrylic copolymer containing at least one hydrophilic group comprising at least one of a carboxyl and anhydride; (C) an intermediate layer which functions as a barrier layer, the intermediate layer comprising an ethylene-vinyl alcohol copolymer containing a hydrophilic group comprising hydroxyl; (D) a second adhesive layer comprising a maleic anhydride-grafted polyethylene copolymer containing a hydrophilic group comprising anhydride; and (E) an inner layer comprising polyethylene; (F) characterized in that the materials of the layers each have added thereto an additive master batch for the respective layer, the additive master batch for the respective layer comprising a carrier and an active agent, wherein the active agent comprises a polymer containing a hydrophilic group, wherein an effective component of the active agent is the hydrophilic group, wherein the hydrophilic group is at least one of carboxylate, carboxyl, hydroxyl, aldehyde group, acylamino, anhydride and ester group, wherein the carrier is dependent on the material of the respective layer, and wherein the mole ratio of the hydrophilic groups to carbon atoms within each layer is the same across all layers of the film by the additive amount of the additive master batch for each layer.

2. The film of claim 1 wherein an additive amount of the additive master batch in the materials of each layer is controlled within the range of 0.3-15% of the total mass of the materials of the corresponding layer; the hydrophilic activity of the hydrophilic groups in the additive master batch is greater than or equal to that of the hydrophilic groups in the materials of each layer of the film.

3. A degradable EVOH high-barrier composite film comprising: (A) an outer layer comprising a polyester containing a hydrophilic ester group, the polyester comprising at least one of polyethylene terephthalate or poly(ethylene terephthalate-co-1,4-cyclohexylenedimethylene terephthalate); (B) a first adhesive layer comprising a maleic anhydride-grafted ethylene acrylic copolymer containing at least one hydrophilic group comprising at least one of a carboxyl and anhydride; (C) an intermediate layer which functions as a barrier layer, the intermediate layer comprising an ethylene-vinyl alcohol copolymer containing a hydrophilic group comprising hydroxyl; (D) a second adhesive layer comprising a maleic anhydride-grafted polypropylene copolymer containing a hydrophilic group comprising anhydride; and (E) an inner layer comprising polypropylene; (F) characterized in that the materials of the layers each have added thereto an additive master batch for the respective layer, the additive master batch for the respective layer comprising a carrier and an active agent, wherein the active agent comprises a polymer containing a hydrophilic group, wherein an effective component of the active agent is the hydrophilic group, wherein the hydrophilic group is at least one of carboxylate, carboxyl, hydroxyl, aldehyde group, acylamino, anhydride and ester group, wherein the carrier is dependent on the material of the respective layer, and wherein the mole ratio of the hydrophilic groups to carbon atoms within each layer is the same across all layers of the film by the additive amount of the additive master batch for each layer.

4. The film of claim 3 wherein an additive amount of the additive master batch in the materials of each layer is controlled within the range of 0.3-15% of the total mass of the materials of the corresponding layer; the hydrophilic activity of the hydrophilic groups in the additive master batch is greater than or equal to that of the hydrophilic groups in the materials of each layer in the film.

Description

DETAILED DESCRIPTION

(1) The present invention is further described in combination with embodiments.

Embodiment 1

(2) (Examples of the First Technical Solution)

(3) A degradable EVOH high-barrier composite film has a structure as follows:
PET/EAA-TIE/EVOH/PE-TIE/PE Formula (1)
in formula (1), the meanings in a sequence from left to right are as follows: PET is an outer layer which has a function of a protective layer or presentation layer, a material of the PET is polyester, a monomer molecular formula is [OCH2-CH2OCOC6H4CO], and a hydrophilic group that the polyester contains per se is ester group —COO—;
EAA-TIE is a first adhesive layer, a material of the EAA-TIE is maleic anhydride-grafted ethylene acrylic copolymer which is formed by mixing 95 wt % of ethylene acrylic acid and 5 wt % of maleic anhydride, and a monomer molecular formula of the EAA-TIE is {[CH2-CH2]15.5[CH2-CH(COOH)]1}3.7[C4H2O3]1. Hydrophilic groups that the maleic anhydride-grafted ethylene acrylic copolymer per se contains are carboxyl —COOH and anhydride OC—O—CO;
EVOH is an intermediate layer which has a function of a barrier layer, a material of the EVOH is EVOH indicating ethylene-vinyl alcohol copolymer. Ethylene-vinyl alcohol copolymer is formed by 32 wt % of ethylene PE and 68 wt % of vinyl alcohol PVA, and its monomer molecular formula is [CH.sub.2CH.sub.2].sub.1[CH.sub.2CHOH].sub.1.4. A hydrophilic group that the ethylene-vinyl alcohol copolymer contains is hydroxyl —OH;
PE-TIE is a second adhesive layer, a material of the PE-TIE is maleic anhydride-grafted polyethylene copolymer. Maleic anhydride-grafted polyethylene copolymer is formed by mixing 95 wt % of polyethylene and 5 wt % of maleic anhydride and A monomer molecular formula of the PE-TIE is —[CH.sub.2—CH.sub.2].sub.n—[C.sub.4H.sub.2O.sub.3].sub.m. A hydrophilic group that the maleic anhydride-grafted polyethylene copolymer contains is anhydride —OC—O—CO—;
PE is an inner layer which has a function of a heat sealing layer, a material of the PE is polyethylene, a monomer molecular formula of the PE is —[CH.sub.2—CH.sub.2].sub.n—, and the polyethylene contains no hydrophilic group per se.

(4) In the outer layer, the polyester is amorphous polyethylene terephthalate. In actual use, if poly(ethylene terephthalateco-1,4-cylclohexylenedimethylene terephthalate) is adopted, the same effect can also be achieved; in the present embodiment, a density of the polyester is 1.360 g/cm.sup.3; in actual use, if the density of the polyester is 1.300 g/cm.sup.3, 1.400 g/cm.sup.3 or other values between 1.300-1.400 g/cm.sup.3, the same effect can also be achieved.

(5) In the first adhesive layer, a density of the maleic anhydride-grafted ethylene acrylic copolymer is 0.940 g/cm.sup.3.

(6) In actual use, if the density of the maleic anhydride-grafted ethylene acrylic copolymer is 0.920 g/cm.sup.3, 0.930 g/cm.sup.3 or other values between and 0.920-0.940 g/cm.sup.3, the same effect can also be achieved; in the present embodiment, a mass percent of the grating ratio of maleic anhydride is 5 wt %, and in actual use, if 0.3 wt %, 8 wt %, 10 wt % or other values between 0.3-10 wt % is adopted, the same effect can also be achieved. A mole content of acrylic acid in the ethylene acrylic copolymer is 14%, and in actual use, if 28%, 20% or other values between 8-28% is adopted, the same effect can also be achieved.

(7) In the barrier layer, a density of the ethylene-vinyl alcohol copolymer is 1.170/cm.sup.3, and in actual use, if the density is 1.190 g/cm.sup.3, 1.18 g/cm.sup.3 and other values between 1.170-1.190 g/cm.sup.3, the same effect can also be achieved, and a mole content of ethylene in the ethylene-vinyl alcohol copolymer is 32%; in actual use, if a mole content of ethylene of 26%, 30%, 48% or other value between 26-48% is adopted, the same effect can also be achieved.

(8) In the second adhesive layer, a density of the maleic anhydride-grafted polyethylene copolymer is 0.910 g/cm.sup.3. In actual use, if the density is 0.950 g/cm.sup.3, 0.0300.950 g/cm.sup.3 or other values between 0.910-0.950 g/cm.sup.3, the same effect can also be achieved, and a mass percent of a grating ratio of maleic anhydride is 5 wt %. In actual use, if 0.3 wt %, 8 wt %, 10 wt % or other values between 0.3-10 wt % is adopted, the same effect can also be achieved.

(9) In the heat sealing layer, the polyethylene has a density of 0.900-0.935 g/cm.sup.3, and the same effect can also be achieved if the density is 0.900 g/cm.sup.3, 0.940 g/cm.sup.3 or other values between 0.900-0.935 g/cm.sup.3; the polyethylene contains a polyethylene copolymer, the polyethylene copolymer has a density of 0.910-0.925 g/cm.sup.3, and the same effect can also be achieved if 0.910 g/cm.sup.3, 0.925 g/cm.sup.3, 0.920 g/cm.sup.3 or other values between 0.910-0.925 g/cm.sup.3 is adopted; the polyethylene copolymer consists of 50-99 wt % of polyethylene and 1-50 wt % of vinyl homopolymer, and the same effect can also be achieved if 50 wt % of polyethylene and 50 wt % of vinyl homopolymer, or 99 wt % of polyethylene and 1 wt % of vinyl homopolymer or 75 wt % of polyethylene and 25 wt % of vinyl homopolymer is adopted; the vinyl copolymer consists of ethylene and at least one of C4-C12 α-olefin, cycloolefin, vinyl arene and polar vinyl monomer, and a density of the vinyl copolymer is 0.880-0.915 g/cm.sup.3; the same effect can also be achieved if 0.910 g/cm.sup.3, 0.915 g/cm.sup.3, 0.900 g/cm.sup.3 or other values between 0.880-0.915 g/cm.sup.3 is adopted.

(10) The materials of various layers in the composite film all obtain approximately-consistent biodegradability by being introduced a biomass. The biomass is a type of additive master batch having biodegradable activity under a condition of a refuse disposal plant or composting. The additive master batch is uniformly added into the materials of various layers in proportion, and then the composite film is prepared through a melting co-extrusion method.

(11) The additive master batch consists of a carrier and an active agent, the active agent is a polymer containing a hydrophilic group, wherein an effective component of the active agent is the hydrophilic group, and the hydrophilic group is at least one of carboxylate —COO.sup.−, carboxyl —COOH, hydroxyl —OH, aldehyde group —CHO, acylamino —CONH.sub.2, anhydride —OC—O—CO— and ester group —COOR.

(12) In the materials of various layers in formula (1) and the additive master batch, the hydrophilic groups are arrayed in a sequence of carboxylate —COO.sup.−, carboxyl —COOH, hydroxyl —OH, aldehyde group —CHO, acylamino —CONH.sub.2, anhydride —OC—O—CO— and ester group —COOR according to the hydrophilic activity from high to low.

(13) The carriers are selected according to the principle of similarity and intermiscibility specific to the materials of various layers;

(14) for the polyester material of the outer layer, the carrier in the additive master batch is polyester;

(15) for the maleic anhydride-grafted ethylene acrylic copolymer material of the first adhesive layer, the carrier in the additive master batch is ethylene acrylic copolymer; for the ethylene-vinyl alcohol copolymer material of the intermediate layer, the carrier in the additive master batch is polyethylene;
for the maleic anhydride-grafted polyethylene copolymer material of the second adhesive layer, the carrier in the additive master batch is polyethylene; for the polyethylene material of the inner layer, the carrier in the additive master batch is polyethylene;

(16) The additive amount of the additive master batch in the materials of each layer is controlled within the range of 0.3-15% of the total mass of the materials of the corresponding layer; the hydrophilic activity of the hydrophilic groups in the additive master batch should be greater than or equal to that of the hydrophilic groups in the materials of each layer in formula (1); by adding the additive master batch, the mole ratios of the hydrophilic groups to carbon atoms of the materials of various layers in formula (1) tend to be consistent, namely, the bioactivities tend to be consistent, so that the degradation rates of the materials of various layers in the composite film tend to be consistent.

(17) The hydrophilic groups contained in the various materials in the composite film structure according to embodiment 1 are arrayed in a sequence of carboxyl>hydroxyl>anhydride>ester group according to the hydrophilic activity from high to low, that is, the materials of various layers in formula (1) are arrayed in a sequence of maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride)>ethylene-vinyl alcohol copolymer EVOH (32% PE+68% PVA)>PE-TIE (95% PE+5%maleic anhydride)>polyester PET>polyethylene PE according to the hydrophilic activity from high to low.

(18) Sodium alginate of which the hydrophilic activity is larger than that of EAA-TIE(carboxyl) in the composite film material is selected as the additive active agent and the hydrophilic activity of the original hydrophilic groups in the composite film material is weakened.

(19) 1. A monomer molecular formula of the sodium alginate is known as (C.sub.5H.sub.7O.sub.4COONa).sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), and the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). Therefore, in the present embodiment, the polymer sodium alginate is selected as the active agent to be added to the materials of various layers.

(20) 2. Since the hydrophilic activity of the carboxylic sodium in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, the sodium alginate plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PE-TIE and that of the ester group in PET in the composite film material are weakened. For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PE-TIE and PET are 0.

(21) 3. Through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate is 2/3.

(22) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PE-TIE, PET and PE are 0.

(23) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(24) Mass percents of the sodium alginate added to the materials of various layers are respectively calculated by taking 1 mol % and 2.2 mol % of sodium alginate additive amounts as reference values.

(25) A. 1 Mol % of Sodium Alginate Additive Amount

(26) The materials of various layers in formula (1) and the sodium alginate are respectively mixed at a mole ratio of 99:1, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate is added to the materials of various layers is calculated:
99/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)99/100*0+1/100*2/3=0.0067;
99/100*ethylene-vinyl alcohol copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*maleic anhydride-grafted polyethylene copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*polyethylene.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;

(27) It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PE-TIE/PE structure, the materials of various layers and the sodium alginate are respectively mixed at a mole ratio of 99:1, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate in the materials of various layers is calculated as follows:

(28) The PET to which the sodium alginate is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*99%*1=190.25 g;
m.sub.2-1=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;

(29) The EAA-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*99%*1=39.39 g;
m.sub.2-2=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;

(30) The EVOH to which the sodium alginate is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*99%*1=88.83 g;
m.sub.2-3=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The PE-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the PE-TIE is m.sub.1-4 and the mass of the sodium alginate is m.sub.2-4;
m.sub.1-4=molecular weight of PE-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=32.67*99%*1=32.34 g;
m.sub.2-4=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The PE to which the sodium alginate is added is set to be 1 mol, the mass of the PE is m.sub.1-5 and the mass of the sodium alginate is m.sub.2-5;
m.sub.1-5=molecular weight of PE (g/mol)*PE content (%)*mole weight (mol)=28.05*99%*1=27.77 g;
m.sub.2-5=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate accounting for the mass of the PET is 1.98/(190.25+1.98)*100%=1.03%; and the mass percent of the added sodium alginate in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate of PET/EAA-TIE/EVOH/PE-TIE/PE from left to right is 1.03/4.79/2.18/5.77/6.66.
B. 2.2 Mol % of Sodium Alginate Additive Amount

(31) The materials of various layers in formula (1) and the sodium alginate are respectively mixed at a mole ratio of 97.8:2.2, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate is added to the materials of various layers is calculated:
97.8/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*ethylene-vinyl alcohol copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*maleic anhydride-grafted polyethylene copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*polyethylene.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;

(32) It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PE-TIE/PE structure, the materials of various layers and the sodium alginate are respectively mixed at a mole ratio of 97.8:2.2, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate in the materials of various layers is calculated as follows:

(33) The PET to which the sodium alginate is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*97.8%*1=187.94 g;
m.sub.2-1=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The EAA-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*97.8%*1=36.59 g;
m.sub.2-2=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The EVOH to which the sodium alginate is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*97.8%*1=87.76 g;
m.sub.2-3=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;

(34) The PE-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the PE-TIE is m.sub.1-4 and the mass of the sodium alginate is m.sub.2-4;
m.sub.1-4=molecular weight of PE-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=32.67*97.8%*1=31.59 g;
m.sub.2-4=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The PE to which the sodium alginate is added is set to be 1 mol, the mass of the PE is m.sub.1-5 and the mass of the sodium alginate is m.sub.2-5;
m.sub.1-5=molecular weight of PE (g/mol)*PE content (%)*mole weight (mol)=28.05*97.8%*1=27.43 g;
m.sub.2-5=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate accounting for the mass of the PET is 4.36/(187.94+4.36)*100%=2.27%; and the mass percent of the added sodium alginate in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate of PET/EAA-TIE/EVOH/PE-TIE/PE from left to right is 2.27/10.65/4.73/12.01/13.72.

(35) When the additive amount of the sodium alginate accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the material of such layer

(36) In order to improve the processing suitability and dispersity of the hydrophilic groups, polymers with very excellent intermiscibility can be selected for copolymerization, for example, a copolymer copolymerized by polycaprolactone (PCL) and sodium alginate and a copolymer copolymerized by polylactic acid (PLA) and sodium alginate.

(37) A. copolymer copolymerized by polycaprolactone (PCL) and sodium alginate.

(38) 1. A monomer molecular formula of the sodium alginate is known as (C.sub.5H.sub.7O.sub.4COONa).sub.n, and a monomer molecular formula of the polycaprolactone is known as [CH.sub.2—CH.sub.2).sub.4—COO].sub.m. A monomer molecular formula of sodium alginate-grafted polycaprolactone copolymer with a grafting ratio being 50-80 mass % is [CH.sub.2—(CH.sub.2).sub.4—COO].sub.m(C.sub.5H.sub.7O.sub.4COONa).sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), and the hydrophilic group contained in the polycaprolactone is ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), and the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). In the present embodiment, the sodium alginate-grafted polycaprolactone copolymer is selected as the active agent to be added to the materials of various layers, wherein a mass percent of a grafting ratio of the sodium alginate is 60%.

(39) 2. Since the hydrophilic activity of the carboxylic sodium in the copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, the copolymer plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PE-TIE and that of the ester group in PET in the composite film material are weakened. For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PE-TIE and PET are 0.

(40) 3. A mole ratio of the hydrophilic groups to carbon atoms in the sodium alginate in the sodium alginate-grafted polycaprolactone copolymer is 2/3; a mole ratio of the hydrophilic groups to carbon atoms in the polycaprolactone is 1/7; through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate-grafted polycaprolactone copolymer is 2/3*60%+1/7*40%=0.4571.

(41) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PE-TIE, PET and PE are 0.

(42) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(43) Mass percents of the sodium alginate-grafted polycaprolactone copolymer added to the materials of various layers are respectively calculated by taking 2 mol % of sodium alginate-grafted polycaprolactone copolymer additive amount as a reference value.

(44) The materials of various layers in formula (1) and the sodium alginate-grafted polycaprolactone copolymer are respectively mixed at a mole ratio of 98:2, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate-grafted polycaprolactone copolymer is added to the materials of various layers is calculated:
98/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafted polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PE-TIE/PE structure, the materials of various layers and the sodium alginate-grafted polycaprolactone copolymer are respectively mixed at a mole ratio of 98:2, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate-grafted polycaprolactone copolymer in the materials of various layers is calculated as follows:
The PET to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*98%*1=188.33 g;
m.sub.2-1=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The EAA-TIE to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*98%*1=36.66 g;
m.sub.2-2=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The EVOH to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*98%*1=87.94 g;
m.sub.2-3=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The PE-TIE to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PE-TIE is m.sub.1-4 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-4;
m.sub.1-4=molecular weight of PE-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=32.67*98%*1=32.02 g;
m.sub.2-4=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The PE to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PE is m.sub.1-5 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-5;
m.sub.1-5=molecular weight of PE (g/mol)*PE content (%)*mole weight (mol)=28.05*98%*1=27.49 g;
m.sub.2-5=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate-grafted polycaprolactone copolymer accounting for the mass of the PET is 3.29/(188.33+3.29)*100%=1.72%; and the mass percent of the added sodium alginate-grafted polycaprolactone copolymer in the materials of various layers is calculated in the same manner;
a ratio of the additive mass percents of the sodium alginate-grafted polycaprolactone copolymer of PET/EAA-TIE/EVOH/PE-TIE/PE from left to right is 1.72/8.24/3.61/9.32/10.69.

(45) When the additive amount of the sodium alginate-grafted polycaprolactone copolymer accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the materials of such layer

(46) B. Copolymer Copolymerized by Polylactic Acid (PLA) and Sodium Alginate

(47) 1. A monomer molecular formula of the sodium alginate is known as [H—(OCH(CH3)CO).sub.2—OH].sub.m, and a monomer molecular formula of the polycaprolactone is known as [CH.sub.2—(CH.sub.2).sub.4—COO].sub.m. A monomer molecular formula of sodium alginate-grafted polylactic acid copolymer with a grafting ratio of 5-20 mass % is [H—(OCH(CH3)CO).sub.2—OH].sub.m[C.sub.5H.sub.7O.sub.4COONa].sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), the hydrophilic groups contained in the polylactic acid are carboxyl (—COOH), hydroxyl (—OH) and ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), the content of the carboxyl (—COOH) in the polylactic acid is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), and the hydrophilic activity of the carboxyl (—COOH) in the polylactic acid is larger than that of the anhydride(—OC—O—CO—) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). In the present embodiment, the sodium alginate-grafted polylactic acid copolymer with a grafting ratio being 10 wt % is selected as the active agent to be added to the materials of various layers.

(48) 2. Since the hydrophilic activity of the carboxylic sodium in the sodium alginate-grafted polylactic acid copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, and the content of the carboxyl (—COOH) in the sodium alginate-grafted polylactic acid copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), the copolymer plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PE-TIE and that of the ester group in PET in the composite film material are weakenedI For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PE-TIE and PET are 0.

(49) 3. A mole ratio of the hydrophilic groups to carbon atoms in the sodium alginate in the sodium alginate-grafted polylactic acid copolymer is 2/3; a mole ratio of the hydrophilic groups to carbon atoms in the polylactic acid is 2/3; through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate-grafted polylactic acid copolymer is 2/3*10%+2/3*90%=2/3.

(50) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PE-TIE, PET and PE are 0.

(51) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(52) Mass percents of the sodium alginate-grafted polylactic acid copolymer added to the materials of various layers are respectively calculated by taking 1.5 mol % of sodium alginate-grafted polylactic acid copolymer additive amount as a reference value.

(53) The materials of various layers in formula (1) and the sodium alginate-grafted polylactic acid copolymer are mixed at a mole ratio of 98.5:1.5, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate-grafted polylactic acid copolymer is added to the materials of various layers is calculated:
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*polyethylene.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafted polylactic acid copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PE-TIE/PE structure, the materials of various layers and the sodium alginate-grafted polylactic acid copolymer are respectively mixed at a mole ratio of 98.5:1.5, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate-grafted polylactic acid copolymer in the materials of various layers is calculated as follows:
The PET to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*98.5%*1=189.29 g;
m.sub.2-1=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The EAA-TIE to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*98.5%*1=36.85 g;
m.sub.2-2=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The EVOH to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*98.5%*1=88.38 g;
m.sub.2-3=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The PE-TIE to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PE-TIE is m.sub.1-4 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-4;
m.sub.1-4=molecular weight of PE-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=32.67*98.5%*1=32.18 g;
m.sub.2-4=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The PE to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PE is m.sub.1-5 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-5;
m.sub.1-5=molecular weight of PE (g/mol)*PE content (%)*mole weight (mol)=28.05*98.5%*1=27.63 g;
m.sub.2-5=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate-grafted polylactic acid copolymer accounting for the mass of the PET is 2.49/(189.29+2.49)*100%=1.30%; and the mass percent of the added sodium alginate-grafted polylactic acid copolymer in the materials of various layers is calculated in the same manner;
a ratio of the additive mass percents of the sodium alginate-grafted polylactic acid copolymer of PET/EAA-TIE/EVOH/PE-TIE/PE from left to right is 1.30/6.33/2.74/7.18/8.27.

(54) When the additive amount of the sodium alginate-grafted polylactic acid copolymer accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the material of such layer

Embodiment 2

(55) (Examples of the Second Technical Solution)
PET/EAA-TIE/EVOH/PP-TIE/PP  Formula (2)
in formula (2), the meanings in a sequence from left to right are as follows: PET is an outer layer which has a function of a protective layer or presentation layer, a material of the PET is polyester; a monomer molecular formula of the PET is [OCH2-CH2OCOC6H4CO], and a hydrophilic group that the polyester contains per se is ester group —COO—;
EAA-TIE is a first adhesive layer; a material of the EAA-TIE is maleic anhydride-grafted ethylene acrylic copolymer and a monomer molecular formula of the EAA-TIE is {[CH.sub.2—CH.sub.2].sub.15.5[CH.sub.2—CH(COOH)].sub.1}.sub.3.7[C.sub.4H.sub.2O.sub.3].sub.1. Hydrophilic groups that the maleic anhydride-grafted ethylene acrylic copolymer per se contains are carboxyl —COOH and anhydride OC—O—CO;
EVOH is an intermediate layer which has a function of a barrier layer; a material of the EVOH is EVOH indicating ethylene-vinyl alcohol copolymer which is formed by 32 wt % of ethylene PE and 68 wt % of vinyl alcohol PVA; a monomer molecular formula of the EVOH is [CH.sub.2CH.sub.2].sub.1[CH.sub.2CHOH].sub.1.4. A hydrophilic group that the ethylene-vinyl alcohol copolymer contains is hydroxyl —OH;
PP-TIE is a second adhesive layer; a material of the PP-TIE is maleic anhydride-grafted polypropylene copolymer which is formed by mixing 95 wt % of polypropylene and 5 wt % of maleic anhydride, and a monomer molecular formula of the PP-TIE is —[CH.sub.2—CH(CH.sub.3)].sub.n—[C.sub.4H.sub.2O.sub.3].sub.m. A hydrophilic group that the maleic anhydride-grafted polypropylene copolymer contains is anhydride —OC—O—CO—;
PP is an inner layer which has a function of a heat sealing layer; a material of the PP is polypropylene and a monomer molecular formula of the PP is —[CH.sub.2—CH(CH.sub.3)].sub.n—, and the polypropylene contains no hydrophilic group per se.

(56) In the outer layer, the polyester is amorphous polyethylene terephthalate, in actual use, if poly(ethylene terephthalateco-1,4-cylclohexylenedimethylene terephthalate), the same effect can also be achieved; in the present embodiment, a density of the polyester is 1.360 g/cm.sup.3, in actual use, if the density of the polyester is 1.300 g/cm.sup.3, 1.400 g/cm.sup.3, other values between 1.300-1.400 g/cm.sup.3, the same effect can also be achieved.

(57) In the first adhesive layer, a density of the maleic anhydride-grafted ethylene acrylic copolymer is 0.940 g/cm.sup.3.

(58) In actual use, if the density of the maleic anhydride-grafted ethylene acrylic copolymer is 0.920 g/cm.sup.3, 0.930 g/cm.sup.3 or other values between and 0.920-0.940 g/cm.sup.3, the same effect can also be achieved; in the present embodiment, a mass percent of the grating ratio of maleic anhydride is 5 wt %, and in actual use, if 0.3 wt %, 8 wt %, l0 wt % or other values between 0.3-10 wt % is adopted, the same effect can also be achieved. A mole content of acrylic acid in the ethylene acrylic copolymer is 14%, and in actual use, if 28%, 20% or other values between 8-28% is adopted, the same effect can also be achieved.

(59) In the barrier layer, a density of the ethylene-vinyl alcohol copolymer is 1.170/cm.sup.3, and in actual use, if the density is 1.190 g/cm.sup.3, 1.18 g/cm.sup.3 or other values between 1.170-1.190 g/cm.sup.3, the same effect can also be achieved. A mole content of ethylene in the ethylene-vinyl alcohol copolymer is 32%, and in actual use, if 26%, 30%, 48% or other value between 26-48% is adopted, the same effect can also be achieved.

(60) In the second adhesive layer, a density of the maleic anhydride-grafted polyethylene copolymer is 0.910 g/cm.sup.3, and in actual use, if the density is 0.950 g/cm.sup.3, 0.0300.950 g/cm.sup.3 and other values between 0.910-0.950 g/cm.sup.3, the same effect can also be achieved. A mass percent of a grating ratio of maleic anhydride is 5 wt %, and in actual use, if 0.3 wt %, 8 wt %, 10 wt % and other values between 0.3-10 wt % is adopted, the same effect can also be achieved.

(61) In the heat sealing layer, the polyethylene has a density of 0.900-0.935 g/cm.sup.3, and the same effect can also be achieved if the density is 0.900 g/cm.sup.3, 0.935 g/cm.sup.3, 0.940 g/cm.sup.3 or other values between 0.900-0.935 g/cm.sup.3; the polyethylene contains a polyethylene copolymer, the polyethylene copolymer has a density of 0.910-0.925 g/cm.sup.3, and the same effect can also be achieved if 0.910 g/cm.sup.3, 0.925 g/cm.sup.3, 0.920 g/cm.sup.3 or other values between 0.910-0.925 g/cm.sup.3 is adopted; the polyethylene copolymer consists of 50-99 wt % of polyethylene and 1-50 wt % of vinyl homopolymer, and the same effect can also be achieved if 50 wt % of polyethylene and 50 wt % of vinyl homopolymer, 99 wt % of polyethylene and 1 wt % of vinyl homopolymer or 75 wt % of polyethylene and 25 wt % of vinyl homopolymer, etc. is adopted; the vinyl copolymer consists of ethylene and at least one of C4-C12 α-olefin, cycloolefin, vinyl arene and polar vinyl monomer, and a density of the vinyl copolymer is 0.880-0.915 g/cm.sup.3, and the same effect can also be achieved if 0.910 g/cm.sup.3, 0.915 g/cm.sup.3, 0.900 g/cm.sup.3 or other values between 0.880-0.915 g/cm.sup.3 is adopted.

(62) The materials of various layers in the composite film all obtain approximately-consistent biodegradability by introducing biomass. The biomass is a type of additive master batch having biodegradable activity under a condition of a refuse disposal plant or composting, the additive master batch is uniformly added into the materials of various layers in proportion, and then the composite film is prepared through a melting co-extrusion method.

(63) The additive master batch consists of a carrier and an active agent. The active agent is a polymer containing a hydrophilic group, wherein an effective component of the active agent is the hydrophilic group, and the hydrophilic group is at least one of carboxylate —COO.sup.−, —COOH, carboxyl —COOH, hydroxyl —OH, aldehyde group —CHO, acylamino —CONH.sub.2, anhydride —OC—O—CO— and ester group —COOR.

(64) In the materials of various layers and additive master batch in formula (2), the hydrophilic groups are arrayed in a sequence of carboxylate —COO.sup.−, carboxyl —COOH, hydroxyl —OH, aldehyde group —CHO, acylamino —CONH.sub.2, anhydride —OC—O—CO— and ester group —COOR according to the hydrophilic activity from high to low.

(65) The carriers are selected according to the principle of similarity and intermiscibility specific to the materials of various layers;

(66) for the polyester material of the outer layer, the carrier in the additive master batch is polyester;

(67) for the maleic anhydride-grafted ethylene acrylic copolymer material of the first adhesive layer, the carrier in the additive master batch is ethylene acrylic copolymer;

(68) for the ethylene-vinyl alcohol copolymer material of the intermediate layer, the carrier in the additive master batch is polyethylene;

(69) for the maleic anhydride-grafted polyethylene copolymer material of the second adhesive layer, the carrier in the additive master batch is polyethylene;

(70) for the polyethylene material of the inner layer, the carrier in the additive master batch is polyethylene;

(71) The additive amount of the additive master batch in the materials of each layer is controlled within the range of 0.3-15% of the total mass of the materials of the corresponding layer; the hydrophilic activity of the hydrophilic groups in the additive master batch should be greater than or equal to that of the hydrophilic groups in the materials of each layer in formula (2); by adding the additive master batch, the mole ratios of the hydrophilic groups to carbon atoms of the materials of various layers in formula (2) tend to be consistent, namely, the bioactivities tend to be consistent, so that the degradation rates of the materials of various layers in the composite film tend to be consistent.

(72) The hydrophilic groups contained in the various materials in the composite film structure according to embodiment 2 are arrayed in a sequence of carboxyl>hydroxyl>anhydride>ester group according to the hydrophilic activity from high to low, that is, the materials of various layers in formula (2) are arrayed in a sequence of maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride)>ethylene-vinyl alcohol copolymer EVOH (32% PE+68% PVA)>PP-TIE (95% PE+5%maleic anhydride)>polyester PET>polypropylene PP according to the hydrophilic activity from high to low.

(73) Sodium alginate of which the hydrophilic activity is larger than that of EAA-TIE(carboxyl) in the composite film material is selected as the additive active agent and the hydrophilic activity of the original hydrophilic groups in the composite film material is weakened.

(74) 1. A monomer molecular formula of the sodium alginate is known as (C.sub.5H.sub.7O.sub.4COONa).sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). Therefore, in the present embodiment, the polymer sodium alginate is selected as the active agent to be added to the materials of various layers.

(75) 2. Since the hydrophilic activity of the carboxylic sodium in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, the sodium alginate plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PP-TIE and that of the ester group in PET in the composite film material are weakened. For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PP-TIE and PET are 0.

(76) 3. Through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate is 2/3.

(77) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PP-TIE, PET and PP are 0.

(78) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(79) Mass percents of the sodium alginate added to the materials of various layers are respectively calculated by taking 1 mol % and 2.2 mol % of sodium alginate additive amounts as reference values.

(80) A. 1 Mol % of Sodium Alginate Additive Amount

(81) The materials of various layers in formula (2) and the sodium alginate are respectively mixed at a mole ratio of 99:1, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate is added to the materials of various layers is calculated:
99/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)99/100*0+1/100*2/3=0.0067;
99/100*ethylene-vinyl alcohol copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*maleic anhydride-grafted polyethylene copolymer.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;
99/100*polypropylene.sub.(n hydrophilic groups: n carbon atoms)+1/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=99/100*0+1/100*2/3=0.0067;

(82) It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PP-TIE/PP structure, the materials of various layers and the sodium alginate are respectively mixed at a mole ratio of 99:1, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate in the materials of various layers is calculated as follows:

(83) The PET to which the sodium alginate is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*99%*1=190.25 g;
m.sub.2-1=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The EAA-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*99%*1=37.04 g;
m.sub.2-2=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The EVOH to which the sodium alginate is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*99%*1=88.83 g;
m.sub.2-3=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The PP-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the PP-TIE is m.sub.1-4 and the mass of the sodium alginate is m.sub.2-4;
m.sub.1-4=molecular weight of PP-TIE (g/mol)*PP-TIE content (%)*mole weight (mol)=45.56*99%*1=45.10 g;
m.sub.2-4=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
The PP to which the sodium alginate is added is set to be 1 mol, the mass of the PP is m.sub.1-5 and the mass of the sodium alginate is m.sub.2-5;
m.sub.1-5=molecular weight of PP (g/mol)*PP content (%)*mole weight (mol)=41.07*99%*1=40.66 g;
m.sub.2-5=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*1%*1=1.98 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate accounting for the mass of the PET is 1.98/(190.25+1.98)*100%=1.03%; and the mass percent of the added sodium alginate in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate of PET/EAA-TIE/EVOH/PP-TIE/PP from left to right is 1.03/5.07/2.18/4.21/4.64.
B. 2.2 Mol % of Sodium Alginate Additive Amount

(84) The materials of various layers in formula (2) and the sodium alginate are mixed at a mole ratio of 97.8:2.2, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate is added to the materials of various layers is calculated:
97.8/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*ethylene-vinyl alcohol copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*maleic anhydride-grafted polyethylene copolymer.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;
97.8/100*polyethylene.sub.(n hydrophilic groups: n carbon atoms)+2.2/100*sodium alginate.sub.(n hydrophilic groups: n carbon atoms)=97.8/100*0+2.2/100*2/3=0.0147;

(85) It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PP-TIE/PP structure, the materials of various layers and the sodium alginate are respectively mixed at a mole ratio of 97.8:2.2, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate in the materials of various layers is calculated as follows:

(86) The PET to which the sodium alginate is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*97.8%*1=187.94 g;
m.sub.2-1=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The EAA-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*97.8%*1=36.59 g;
m.sub.2-2=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The EVOH to which the sodium alginate is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*97.8%*1=87.76 g;
m.sub.2-3=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
The PP-TIE to which the sodium alginate is added is set to be 1 mol, the mass of the PP-TIE is m.sub.1-4 and the mass of the sodium alginate is m.sub.2-4;
m.sub.1-4=molecular weight of PP-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=45.56*97.8%*1=44.56 g;
m.sub.2-4=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;

(87) The PP to which the sodium alginate is added is set to be 1 mol, the mass of the PP is m.sub.1-5 and the mass of the sodium alginate is m.sub.2-5;
m.sub.1-5=molecular weight of PP (g/mol)*PP content (%)*mole weight (mol)=41.07*97.8%*1=40.17 g;
m.sub.2-5=molecular weight of sodium alginate (g/mol)*sodium alginate content (%)*mole weight (mol)=198.12*2.2%*1=4.36 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate accounting for the mass of the PET is 4.36/(187.94+4.36)*100%=2.27%; and the mass percent of the added sodium alginate in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate of PET/EAA-TIE/EVOH/PP-TIE/PP from left to right is 2.27/10.65/4.73/8.91/9.79.

(88) When the additive amount of the sodium alginate accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the material of such layer.

(89) In order to improve the processing suitability and dispersity of the hydrophilic groups, polymers with very excellent intermiscibility can be selected for copolymerization, for example, a copolymer copolymerized by polycaprolactone (PCL) and sodium alginate and a copolymer copolymerized by polylactic acid (PLA) and sodium alginate.

(90) A. copolymer copolymerized by polycaprolactone (PCL) and sodium alginate

(91) 1. A monomer molecular formula of the sodium alginate is known as (C.sub.5H.sub.7O.sub.4COONa).sub.n, and a monomer molecular formula of the polycaprolactone is known as [CH.sub.2—(CH.sub.2).sub.4—COO].sub.m. A monomer molecular formula of sodium alginate-grafted polycaprolactone copolymer with a grafting ratio being 50-80 wt % is [CH.sub.2—(CH.sub.2).sub.4—COO].sub.m(C.sub.5H.sub.7O.sub.4COONa).sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), the hydrophilic group contained in the polycaprolactone is ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). In the present embodiment, the sodium alginate-grafted polycaprolactone copolymer is selected as the active agent to be added to the materials of various layers, wherein a mass percent of a grafting ratio of the sodium alginate is 60%.

(92) 2. Since the hydrophilic activity of the carboxylic sodium in the copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, the copolymer plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PE-TIE and that of the ester group in PET in the composite film material are weakened. For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PE-TIE and PET are 0.

(93) 3. A mole ratio of the hydrophilic groups to carbon atoms in the sodium alginate in the sodium alginate-grafted polycaprolactone copolymer is 2/3; a mole ratio of the hydrophilic groups to carbon atoms in the polycaprolactone is 1/7; through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate-grafted polycaprolactone copolymer is 2/3*60%+1/7*40%=0.4571.

(94) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PP-TIE, PET and PP are 0.

(95) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(96) Mass percents of the sodium alginate-grafted polycaprolactone copolymer added to the materials of various layers are respectively calculated by taking 2 mol % of sodium alginate-grafted polycaprolactone copolymer additive amount as a reference value.

(97) The materials of various layers in formula (2) and the sodium alginate-grafted polycaprolactone copolymer are respectively mixed at a mole ratio of 98:2, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate-grafted polycaprolactone copolymer is added to the materials of various layers is calculated:
98/100*polyester.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafted polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
98/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+2/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98/100*0+2/100*45.71/100=0.0091;
It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PP-TIE/PP structure, the materials of various layers and the sodium alginate-grafted polycaprolactone copolymer are respectively mixed at a mole ratio of 98:2, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate-grafted polycaprolactone copolymer in the materials of various layers is calculated as follows:
The PET to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*98%*1=188.33 g;
m.sub.2-1=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The EAA-TIE to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*98%*1=36.66 g;
m.sub.2-2=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The EVOH to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*98%*1=87.94 g;
m.sub.2-3=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The PP-TIE to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PP-TIE is m.sub.1-4 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-4;
m.sub.1-4=molecular weight of PP-TIE (g/mol)*PE-TIE content (%)*mole weight (mol)=45.56*98%*1=44.65 g;
m.sub.2-4=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
The PP to which the sodium alginate-grafted polycaprolactone copolymer is added is set to be 1 mol, the mass of the PP is m.sub.1-5 and the mass of the sodium alginate-grafted polycaprolactone copolymer is m.sub.2-5;
m.sub.1-5=molecular weight of PP (g/mol)*PP content (%)*mole weight (mol)=41.07*98%*1=40.25 g;
m.sub.2-5=molecular weight of sodium alginate-grafted polycaprolactone copolymer (g/mol)*sodium alginate-grafted polycaprolactone copolymer content (%)*mole weight (mol)=164.52*2%*1=3.29 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate-grafted polycaprolactone copolymer accounting for the mass of the PET is 3.29/(188.33+3.29)*100%=1.72%; and the mass percent of the added sodium alginate-grafted polycaprolactone copolymer in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate-grafted polycaprolactone copolymer of PET/EAA-TIE/EVOH/PP-TIE/PP from left to right is 1.72/8.24/3.61/6.86/7.56.

(98) When the additive amount of the sodium alginate-grafted polycaprolactone copolymer accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the material of such layer

(99) B. Copolymer Copolymerized by Polylactic Acid (PLA) and Sodium Alginate

(100) 1. A monomer molecular formula of the sodium alginate is known as [H—(OCH(CH3)CO).sub.2—OH].sub.m, and a monomer molecular formula of the polycaprolactone is known as [CH.sub.2—(CH.sub.2).sub.4—COO].sub.m. A monomer molecular formula of sodium alginate-grafted polylactic acid copolymer with a grafting ratio of 5-20 mass % is [H—(OCH(CH3)CO).sub.2—OH].sub.m[C.sub.5H.sub.7O.sub.4COONa].sub.n. It can be known from the monomer molecular formula that the hydrophilic groups contained in the sodium alginate are carboxylic sodium (—COONa), hydroxyl (—OH) and ester group (—COOR), the hydrophilic groups contained in the polylactic acid are carboxyl (—COOH), hydroxyl (—OH) and ester group (—COOR), wherein the hydrophilic activity of the carboxylic sodium (—COONa) is larger than that of the carboxyl (—COOH), the hydrophilic activity of the carboxylic sodium (—COONa) in sodium alginate is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), the content of the carboxyl (—COOH) in the polylactic acid is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), and the hydrophilic activity of the carboxyl (—COOH) in the polylactic acid is larger than that of the anhydride(—OC—O—CO—) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride). In the present embodiment, the sodium alginate-grafted polylactic acid copolymer with a grafting ratio being 10 wt % is selected as the active agent to be added to the materials of various layers.

(101) 2. Since the hydrophilic activity of the carboxylic sodium in the sodium alginate-grafted polylactic acid copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride) having the highest hydrophilic activity in the composite film material, and the content of the carboxyl (—COOH) in the sodium alginate-grafted polylactic acid copolymer is larger than that of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), the copolymer plays a main role in a biodegradation process, while the action of the hydrophilic activity of the carboxyl (—COOH) in the maleic anhydride-grafted ethylene acrylic copolymer EAA-TIE (95% EAA+5%maleic anhydride), that of the hydroxyl in EVOH, that of the anhydride in PE-TIE and that of the ester group in PET in the composite film material are weakened. For simplifying expression, it is assumed in the following calculation that mole ratios of the hydrophilic groups to carbon atoms of the EAA-TIE, EVOH, PP-TIE and PET are 0.

(102) 3. A mole ratio of the hydrophilic groups to carbon atoms in the sodium alginate in the sodium alginate-grafted polylactic acid copolymer is 2/3; a mole ratio of the hydrophilic groups to carbon atoms in the polylactic acid is 2/3; through calculation, it can be obtained that a mole ratio of the hydrophilic groups to the carbon atoms in sodium alginate-grafted polylactic acid copolymer is 2/3*10%+2/3*90%=2/3.

(103) 4. The mole ratios of the hydrophilic groups to the carbon atoms in EAA-TIE, EVOH, PP-TIE, PET and PP are 0.

(104) 5. Since an additive amount of the additive master batch is less and the carrier in the additive master batch is the same as or similar to the added polymer, the mass of the carrier in the additive maser batch in the following calculation is omitted in order to simplify expression.

(105) Mass percents of the sodium alginate-grafted polylactic acid copolymer added to the materials of various layers are respectively calculated by taking 1.5 mol % of sodium alginate-grafted polylactic acid copolymer additive amount as a reference value.

(106) The materials of various layers in formula (1) and the sodium alginate-grafted polylactic acid copolymer are mixed at a mole ratio of 98.5:1.5, and a mole ratio of the hydrophilic groups to the carbon atoms after the sodium alginate-grafted polylactic acid copolymer is added to the materials of various layers is calculated:
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*maleic anhydride-grafted ethylene acrylic copolymer.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafter polycaprolactone copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;
98.5/100*polyethylene.sub.(n hydrophilic groups: n carbon atoms)+1.5/100*sodium alginate-grafted polylactic acid copolymer.sub.(n hydrophilic groups: n carbon atoms)=98.5/100*0+1.5/100*2/3=0.0010;

(107) It can be obtained from above calculation that in the PET/EAA-TIE/EVOH/PP-TIE/PP structure, the materials of various layers and the sodium alginate-grafted polylactic acid copolymer are respectively mixed at a mole ratio of 98.5:1.5, the mole ratios of the hydrophilic groups to the carbon atoms after mixing are calculated to be the same, that is, the hydrophilic activities of the materials of various layers tend to be consistent, and degradation rates tend to be consistent. An additive mass of the sodium alginate-grafted polylactic acid copolymer in the materials of various layers is calculated as follows:

(108) The PET to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PET is m.sub.1-1 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-1;
m.sub.1-1=molecular weight of PET (g/mol)*PET content (%)*mole weight (mol)=192.17*98.5%*1=189.29 g;
m.sub.2-1=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The EAA-TIE to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the EAA-TIE is m.sub.1-2 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-2;
m.sub.1-2=molecular weight of EAA-TIE (g/mol)*EAA-TIE content (%)*mole weight (mol)=37.41*98.5%*1=36.85 g;
m.sub.2-2=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The EVOH to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the EVOH is m.sub.1-3 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-3;
m.sub.1-3=molecular weight of EVOH (g/mol)*EVOH content (%)*mole weight (mol)=89.73*98.5%*1=88.38 g;
m.sub.2-3=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The PP-TIE to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PP-TIE is m.sub.1-4 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-4;
m.sub.1-4=molecular weight of PP-TIE (g/mol)*PP-TIE content (%)*mole weight (mol)=45.56*98.5%*1=44.88 g;
m.sub.2-4=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
The PP to which the sodium alginate-grafted polylactic acid copolymer is added is set to be 1 mol, the mass of the PPE is m.sub.1-5 and the mass of the sodium alginate-grafted polylactic acid copolymer is m.sub.2-5;
m.sub.1-5=molecular weight of PP (g/mol)*PP content (%)*mole weight (mol)=41.07*98.5%*1=40.45 g;
m.sub.2-5=molecular weight of sodium alginate-grafted polylactic acid copolymer (g/mol)*sodium alginate-grafted polylactic acid copolymer content (%)*mole weight (mol)=165.74*1.5%*1=2.49 g;
By taking the outer layer PET as an example, the mass percent of the added sodium alginate-grafted polylactic acid copolymer accounting for the mass of the PET is 2.49/(189.29+2.49)*100%=1.30%; and the mass percent of the added sodium alginate-grafted polylactic acid copolymer in the materials of various layers is calculated in the same manner;
A ratio of the additive mass percents of the sodium alginate-grafted polylactic acid copolymer of PET/EAA-TIE/EVOH/PP-TIE/PP from left to right is 1.30/6.33/2.74/5.26/5.80.

(109) When the additive amount of the sodium alginate-grafted polylactic acid copolymer accounting for the total mass of the material of the corresponding layer is in a range of 0.3-15%, there is no influence on the mechanical properties and barrier performance of the material of such layer

(110) In the embodiments above, the sodium alginate and sodium alginate-grafted copolymers are selected as the active agent, which are directly supported by the embodiments above; however, in the present invention, except for the active agents as shown in the above, other polymers, such as polycaprolactone, polylactic acid, polycaprolactone polyhydric alcohols, polysaccharide polymer, algae group polymer, etc., which contain the hydrophilic groups: carboxylate, carboxyl, hydroxyl, aldehyde group, acylamino, anhydride and ester group and the like can also be selected, and those skilled in the art can understand and predict specific polymers containing these groups under the inspiration of the embodiments of the present invention; therefore, the additive master batch according to the present invention is not limited to these polymers given in the embodiments.

(111) In the embodiments above, some examples about values of the additive amount of the additive master batch are given, and under the inspiration of the examples, those skilled in the art can easily conceive that the objective and effect of the present can be realized if the additive master batch is in a range of 0.3-15%.

(112) In the above embodiments, in order to facilitate implementation (suitable for melting extrusion), a range is set for a density, a copolymerization proportion and a blending proportion of the materials of various layers and is explained in the examples. However these requirements are not necessary for the present invention, and cannot serve as a basis limiting a protection scope of the present invention, in other words, various indexes suitable for the melting extrusion outside the range above can be used for implementing the present invention and obtaining corresponding technical effects.

(113) In the present invention, structural formulas of the composite film are given, but in the structural formulas, the same material in the same position can be combined by one or multiple layers, for example, in the structural formula PET/EAA-TIE/EVOH/PE-TIE/PE; such structural formula expresses a 5-layer structure seemingly, but the material in any position can be combined by two or more layers, for example, PE can be combined by two layers such that the composite film is combined by 6 layers, and so on.

(114) The embodiments above are merely intended to explain a technical concept and characteristics of the present invention, aim to cause those skilled in the art to learn about and accordingly implement content of the present invention, and cannot limit the protective scope of the present invention. All equivalent changes or modifications made according to a spiritual essence of the present invention should fall within the protective scope of the present invention.