Two-component lamination adhesive of renewable origin

Abstract

Two-component lamination adhesive, having a NCO component obtained by reacting a polyisocyanate with a composition of diols, a multilayer film comprising an adhesive layer composed of said lamination adhesive, a process for the preparation of said film, and use of said film in the manufacture of flexible packagings.

Claims

1. A two-component lamination adhesive comprising an NCO component and an OH component, wherein the NCO component is obtained by reacting, according to a polyaddition reaction, a stoichiometric excess of an aromatic or aliphatic polyisocyanate (A) with a composition (B) formed of diols comprising, on the basis of the total weight of said composition: from 60 to 100% by weight of a composition (B1) comprising one or more di(polyricinoleate) diols having a hydroxyl number N.sub.OH of between 30 and 70 mg KOH/g and formula (I): ##STR00006## in which: A represents a divalent hydrocarbon radical optionally interrupted by one or more oxygen or sulfur heteroatoms; m and n, which are identical or different, represent 0 or an integer ranging from 1 to 11 and are such that m+n varies from 0 to 11; and from 0 to 40% by weight of a composition (B2) comprising diols having an N.sub.OH of between 72 and 360 mg KOH/g and which are: dimerized fatty alcohols comprising from 20 to 44 carbon atoms, or di(polyricinoleate) diols having formula (II): ##STR00007## in which: B represents a radical as defined above for A which is identical to or different from the radical represented by A; p and q, which are identical or different, represent 0 or an integer ranging from 1 to 3 and are such that p+q varies from 0 to 3.

2. The two-component lamination adhesive as claimed in claim 1, wherein the Brookfield viscosity at 40 C. of the NCO component after mixing (A) and (B) is within the range extending from 500 to 2000 mPa.Math.s.

3. The two-component lamination adhesive as claimed in claim 1, wherein the Brookfield viscosity at 40 C. of the NCO component after mixing (A) and (B) is within the range extending from 500 to 1500 mPa.Math.s.

4. The two-component lamination adhesive as claimed in claim 1, wherein the divalent hydrocarbon radical A corresponds to a diol of formula:
HO-A-OH(VI) each of the 2 OH functional groups of which is replaced with a single bond and the hydroxyl number N.sub.OH of which is within the range extending from 110 to 1808 mg KOH/g.

5. The two-component lamination adhesive as claimed in claim 1, wherein the divalent radical A corresponds to a diol of formula HO-A-OH (VI) chosen from: (a) ethylene glycol; (b) 1,4-butanediol; (c) diethylene glycol; (d) 1,4-cyclohexanedimethanol; (e) a polypropylene glycol with a molar mass ranging from 400 g/mol to 1000 g/mol; or (f) an aliphatic dimerized fatty alcohol comprising from 20 to 44 carbon atoms.

6. The two-component lamination adhesive as claimed in claim 1, wherein the divalent radical A corresponds to a diol of formula HO-A-OH (VI) chosen from an aliphatic dimerized fatty alcohol comprising from 35 to 37 carbon atoms or a polypropylene glycol with a molar mass of 400 g/mol.

7. The two-component lamination adhesive as claimed in claim 1, wherein the di(polyricinoleate) diols constituting the composition (B1) have a hydroxyl number N.sub.OH of between 35 and 65 mg KOH/g.

8. The two-component lamination adhesive as claimed in claim 1, wherein the composition formed of diols (B) comprises from 70 to 100% by weight of (B1) and from 0 to 30% weight/weight of (B2).

9. The two-component lamination adhesive as claimed in claim 1, wherein the polyisocyanate (A) is 2,4- or 4,4-diphenylmethane diisocyanate (MDI).

10. The two-component lamination adhesive as claimed in claim 1, wherein the OH component is a composition comprising at least approximately 80% by weight of ricinoleic acid triglyceride.

11. The two-component lamination adhesive as claimed in claim 1, wherein the NCO and OH components are present in an amount corresponding to an NCO/OH molar ratio of approximately 2.

12. The two-component lamination adhesive as claimed in claim 1, wherein the di(polyricinoleate) diol of formula I is prepared by transesterifying a triglyceride of ricinoleic acid of formula III ##STR00008## with an alcohol of formula R.sup.1 OH, in which R.sup.1 is C.sub.1-4-alkyl, to produce a ricinoleic acid monoester of formula IV ##STR00009## transesterfying IV to obtain a polyricinoleate of formula V ##STR00010## and transesterfying V with a compound of formula VI
HO-A-OH(VI).

13. A multilayer film comprising 2 thin layers bonded to one another by a continuous layer, wherein the continuous layer is composed of the two-component lamination adhesive as defined in claim 1 in the crosslinked state and in an amount of less than 10 g/m.sup.2.

14. A process for the continuous preparation of the multilayer film as defined in claim 13, comprising the sequential stages of: (i) combining the NCO and OH components in the form of an adhesive mixture rendered flowable by heating, (ii) coating a first thin layer with said adhesive mixture to form a substantially continuous layer, (iii) laminating a second thin layer over the first thin layer with the coating formed in stage (ii), then (iv) crosslinking the adhesive mixture.

15. The process according to claim 14, wherein heating in (i) is to a temperature of 40-80 C.

16. A flexible packaging material comprising the multilayer film as claimed in claim 13.

17. A two-component lamination adhesive comprising an NCO component and an OH component, wherein the NCO component is obtained by reacting, according to a polyaddition reaction, a stoichiometric excess of an aromatic or aliphatic polyisocyanate (A) with a composition (B) formed of diols comprising, on the basis of the total weight of said composition: from 60 to 100% by weight of a composition (B1) comprising one or more di(polyricinoleate) diols having a hydroxyl number N.sub.OH of between 30 and 70 mg KOH/g and formula (I): ##STR00011## in which: A represents a divalent hydrocarbon radical optionally interrupted by one or more oxygen or sulfur heteroatoms; m and n, which are identical or different, represent 0 or an integer ranging from 1 to 11 and are such that m+n varies from 0 to 11; and from 0 to 40% by weight of a composition (B2) comprising diols having an N.sub.OH of between 72 and 360 mg KOH/g and which are: dimerized fatty alcohols comprising from 20 to 44 carbon atoms, or di(polyricinoleate) diols having formula (II): ##STR00012## in which: B represents a radical as defined above for A which is identical to or different from the radical represented by A; p and q, which are identical or different, represent 0 or an integer ranging from 1 to 3 and are such that p+q varies from 0 to 3, wherein the NCO component is obtained by reacting, according to a polyaddition reaction, an aromatic or aliphatic polyisocyanate (A) with a composition formed of diols (B), in an amount of (A) and (B) corresponding to a NCO/OH equivalent ratio of between 2 and 10.

Description

EXAMPLE A (REFERENCE)

Preparation of a Composition (B1) Comprising Di(Polyricinoleate) Diols of Dimerized Fatty Alcohols with 35 to 37 Carbon Atoms, of Formula (I)

(1) A description is given below of the preparation of a composition (B1) which comprises diols of formula (I) in which the divalent radical A corresponds to a dimerized fatty alcohol (diol) comprising 35 to 37 carbon atoms in which each of the 2 OH functional groups is replaced by a free valence.

(2) 1st Stage: Preparation of the Methyl Ricinoleate (Formula (IV) in which R.sup.1 is a Methyl Radical):

(3) 16 980 g of castor oil (content of ricinoleic acid triglyceride of approximately 89% by weight, average molar mass of 928 g/mol, water content equal to 0.35% by weight) with 4393 g of methanol and 454.12 g of MeONa are introduced into a 30-liter jacketed reactor. The combination is heated to 75 C. and maintained at this temperature for 2 hours, and then the reaction medium is cooled to 40 C.

(4) The resulting reaction mixture is subsequently left to separate by settling and then several washing operations are carried out with water in order to remove the glycerol.

(5) 15 990 g of a composition comprising approximately 89% by weight of methyl ricinoleate are obtained.

(6) 2nd Stage: Reaction with a Composition Formed of Dimerized Fatty Alcohols Comprising from 35 to 37 Carbon Atoms:

(7) Use is made, as composition formed of dimerized fatty alcohols which comprise from 35 to 37 carbon atoms, of a sample of the Pripol 2033 product sold by Croda, which exhibits an N.sub.OH, determined by titrimetry, of 207 mg KOH/g and which is of 100% renewable origin.

(8) 1875 g (6 mol) of the composition obtained in the 1st stage, 542 g (1 mol) of Pripol 2033 and 24 g of Ti(OBu).sub.4 (1% by weight of the mixture of the reactants) are introduced into a 5-liter reactor and heated up to 90 C. over 30 minutes with slight bubbling of nitrogen. The reaction medium is subsequently brought up to 200 C. under a nitrogen blanket, with mechanical stirring and under a partial vacuum of 10 mbar in order to remove the methanol generated. The condensation (transesterification) reaction is continued for approximately 6 hours until a composition exhibiting a hydroxyl number of 50.5 mg KOH/g is obtained.

(9) Once the reaction is complete, the reaction medium is cooled to approximately 85 C. and the medium is filtered in order to remove the residual catalyst Ti(OBu).sub.4.

(10) 2180 g of a composition which comprises at least approximately 80% of compounds of formula (I) are obtained in the form of a yellow liquid which is viscous at ambient temperature and which is of 100% renewable origin.

EXAMPLE B (REFERENCE)

Preparation of a Composition (B1) Comprising Di(Polyricinoleate) Diols of a Polypropylene Glycol with a Molar Mass of 400 g/Mol, of Formula (I)

(11) A description is given below of the preparation of a composition (B1) comprising diols of formula (I) in which A is a poly(oxypropylene) radical which corresponds to a polypropylene glycol with a molar mass of 400 g/mol without the end OH functional groups, of 100% fossil origin.

(12) 1st Stage: Preparation of the Methyl Ricinoleate (Formula (IV) in which R.sup.1 is a Methyl Radical):

(13) The 1st stage of example A is repeated.

(14) 2nd stage: Reaction with a polypropylene glycol with a molar mass of 400 g/mol:

(15) 1562 g (5 mol) of methyl ricinoleate, 400 g (1 mol) of a polypropylene glycol with a molar mass of 400 g/mol and 21 g of Ti(OBu).sub.4 (1% by weight of the mixture of the reactants) are introduced into a 5-liter jacketed reactor and heated up to 90 C. over 30 minutes with slight bubbling of nitrogen. The reaction medium is subsequently brought up to 200 C. under a nitrogen blanket, with mechanical stirring and under a partial vacuum of 10 mbar in order to remove the methanol generated. The condensation reaction is continued for approximately 6 hours until a hydroxyl number of 59.7 mg KOH/g is obtained.

(16) Once the reaction is complete, the reaction medium is cooled to approximately 85 C. and the medium is filtered in order to remove the residual catalyst Ti(OBu).sub.4.

(17) 1766 g of a composition which comprises at least approximately 80% of compounds of formula (I) are obtained in the form of a yellow liquid which is viscous at ambient temperature and which is thus of 80% renewable origin.

EXAMPLE 1

Two-component Lamination Adhesive Having, as NCO Component, the Reaction Product of Diphenylmethane Diisocyanate (Hereinafter MDI) with a Composition (B) Consisting of the Composition (B1) of Example A

(18) 1.1. Preparation of the NCO Component:

(19) Use is made of a sample of a mixture of 4,4 and 2,4 isomers of MDI (in a proportion respectively of approximately 50%/50% by weight) which titrates 33.5% weight/weight of NCO group, which has a molar mass of 250 g/mol and which is 100% a product of petroleum origin and thus of fossil origin.

(20) 100 g of the composition of example A (corresponding to an equivalent number of OH functional group equal to 0.90 mmol/g) are introduced, under a stream of nitrogen and at ambient temperature, into a closed 250 ml reactor equipped with a stirrer, heating means and a thermometer and connected to a vacuum pump. The combination is heated to 80 C. and maintained at a reduced pressure of 20 mbar for 1 hour in order to dehydrate the diols.

(21) 71.8 g of MDI (corresponding to a number of NCO functional groups equal to 7.98 mmol/g) are then introduced under a stream of nitrogen.

(22) The amounts introduced by weight thus correspond to an NCO/OH equivalent molar ratio equal to 6.4 (cf. table 1). The combination is maintained at reduced pressure of 20 mbar and at 70 C. for 3 hours until the hydroxyl functional groups of the diols of the composition of example A have been completely consumed, corresponding to an NCO content (monitored by potentiometric titration) of 11.8% weight/weight (cf. table 1).

(23) 171.8 g of polyurethane are obtained, the content of NCO group of 11.8% weight/weight of which corresponds to a content of 2.81 mmol/g.

(24) 1.2. Preparation of the Two-Component Lamination Adhesive:

(25) Use is made, as OH component, of a castor oil having a mean N.sub.OH of 162 mg KOH/g.

(26) The NCO component prepared in 1.1. is mixed with the OH component in a proportion of an NCO/OH molar equivalent ratio equal to 2.1, which corresponds by weight to a mixture of 100 g of NCO compound per 46.3 g of OH component (in view of the content by weight of NCO group of the NCO component prepared in 1.1.).

(27) The mixing is carried out at a temperature of 40 C. in the feed tank of the laminating machine described in point 1.4. below. The Brookfield viscosity at 40 C. of the composition obtained is measured: the value obtained is shown in table 1.

(28) 1.3. Calculation of the Content of Renewable Starting Materials:

(29) The content of renewable starting materials is defined as being the total weight of ingredients of renewable origin participating in the preparation of the two-component lamination adhesive, with respect to 100 g of said adhesive.

(30) In order to calculate this content, the reasoning is based on 100 g of composition (B) consisting in the case in point of the composition (B1) of example A (which is of 100% renewable origin). 71.8 g of MDI, which is an ingredient of 100% fossil origin and the weight of which is calculated by using the N.sub.OH of said composition A and the NCO/OH equivalent molar ratio shown in table 1, are added to these 100 g. 171.8 g of NCO component are thus formed.

(31) It is necessary to also add an amount, as OH component, of castor oil (ingredient of 100% renewable origin) equal to 79.5 g to this 171.8 g of NCO component, so as to observe the NCO/OH molar equivalent ratio of 2.1.

(32) There is thus obtained 171.8+79.5 g of NCO and OH two-component product, which comprises a weight of ingredient of renewable origin equal to 100 g of composition (B) and 79.5 g of OH component, hence the ratio of 71% shown in table 1.

(33) 1.4. Preparation of 2 Complex Bilayer Films A and B:

(34) The two-component mixture obtained in 1.2. is used in the manufacture: of a bilayer A, the 1st layer of which is composed of an oriented polypropylene film with a thickness of 20 m and the 2nd layer of which is composed of a metalized oriented polypropylene film with a thickness of 18 m; and of a bilayer B, the 1st layer of which is composed of a PET (PolyEthylene Terephthalate) film with a thickness of 12 m and the 2nd layer of which is composed of a PET film with a thickness of 50 m.

(35) Use is made, for this, of a laminating machine of Nordmeccanica type provided with a coating device of roll type with an open tank operating at a temperature of 40 C. and at a rate of forward progression of 50 m/minute; the adhesive layer binding the 2 films of the bilayers A and B exhibits a thickness of approximately 2 m and the adhesive layer of the bilayer A is in contact with the metalized face of the corresponding polypropylene film.

(36) 1.5. Measurement of the Cohesion of the Bilayer Film A at Ambient Temperature:

(37) In order to complete the crosslinking reaction between the NCO and OH components of the two-component adhesive, the bilayer film A obtained in 1.4. is placed for 10 days in a climate-controlled chamber maintained at a temperature of 23 C. and a relative humidity of 50%.

(38) Said bilayer is subsequently brought back to ambient temperature and then subjected to the 180 peel test in accordance with 1.7.

(39) The result obtained is shown in table 1.

(40) 1.6. Measurement of the Cohesion of the Bilayer Film B Before and after the Pasteurization Test:

(41) The protocol of 1.5. is repeated on the bilayer film B: the result of the 180 C. peel test, carried out on a sample of said film, is shown in table 1 under the designation before pasteurization.

(42) The same bilayer B is subsequently placed in an oven at 90 C. for 1 hour (test representative of a pasteurization treatment) and a 180 C. peel test is again carried out on a fresh sample of said film, the result of which is shown in table 1 under the designation after pasteurization.

(43) 1.7. Description of the 180 Peel Test:

(44) The cohesion of the bilayer film is evaluated by the 180 peel test as described in the French standard NF T 54-122. The principle of this test consists of the determination of the force necessary for the separation (or peeling) of 2 individual layers of films bonded by the two-component adhesive.

(45) A test specimen of rectangular shape with a width of 15 mm and a length of approximately 10 cm is cut out from the bilayer film. The two individual layers of film included in this strip are manually detached from the end of this test specimen and over approximately 2 cm, and the 2 free ends thus obtained are attached to two fastening devices respectively connected to a stationary portion and a movable portion of a tensile testing device which are located on a vertical axis.

(46) While a drive mechanism imparts, to the movable portion, a uniform rate of 100 mm/minute, resulting in the detachment of the 2 layers, the detached ends of which move gradually along a vertical axis with a formation of an angle of 180, the stationary portion, connected to a dynamometer, measures the force endured by the test specimen thus held, which force is measured in newtons.

EXAMPLES 2-5 (ACCORDING TO THE INVENTION) AND 6-7 (COMPARATIVE)

Preparation of the NCO Component

(47) The protocol of 1.1. is repeated for each composition (B) of table 1, the amounts of reactants being adjusted so as to obtain the NCO/OH equivalent molar ratio shown in table 1. In the case of a composition (B) composed of 2 compositions ((B1) and (B2)), the hydroxyl number N.sub.OH of (B) is obtained by calculating the mean of the N.sub.OH of (B1) and (B2), weighted by the contents by weight of (B1) and (B2) in (B).

(48) The content by weight of NCO group of the NCO component obtained is shown in table 1.

(49) Preparation of the Two-component Lamination Adhesive, of the Bilayer Films A and B and their Characterization:

(50) The protocol of 1.2. for the preparation of the two-component lamination adhesive is repeated, an NCO component/OH component molar equivalent ratio which is fixed and equal to 2.1 being maintained and the corresponding amounts by weight being calculated by taking into account the content by weight of NCO group of the NCO component shown in table 1.

(51) As concerns the calculation of the content of renewable starting materials, the mass balance carried out in 1.3. is adapted to the (B1) and (B2) contents of the composition (B), taking into account the fact that the composition of example B is of 80% renewable origin and that the Pripol 2033 is of 100% renewable origin.

(52) The protocols of 1.4. to 1.7. are also repeated.

(53) The results obtained are collated in table 1.

EXAMPLE 8 (REFERENCE)

NCO Component

(54) Use is made of the NCO component of a two-component lamination adhesive manufactured from starting materials of petroleum origin and sold by Bostik under the name MP830. The content by weight of NCO group of said component is 14%.

(55) Preparation of the Two-component Lamination Adhesive, the Bilayer Films A and B and their Characterization:

(56) The protocols of 1.2. to 1.7. are repeated.

(57) A Brookfield viscosity at 40 C. of 640 mPa.Math.s is measured for the mixture of the NCO and OH components.

(58) The content of renewable starting materials is: 35.5%.

(59) The value obtained in the 180 peel test on the bilayer A is 0.93 N.

(60) The value obtained in the 180 peel test on the bilayer B before pasteurization is 4.7 N.

(61) The value obtained in the 180 peel test on the bilayer B after pasteurization is 2.8 N.

(62) The lamination adhesives of examples 1 to 5 according to the invention exhibit a content of renewable starting materials which is advantageously much greater than that of reference example 8, while making possible the preparation of bilayer films which exhibit a comparable cohesion.

(63) The mixture of the NCO and OH components corresponding to comparative examples 6 and 7 is not suitable, due to its viscosity at 40 C., for use as lamination adhesive.

(64) TABLE-US-00001 TABLE 1 Ex. 6 Ex. 7 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 (comp.) (comp) Composition (B1): Composition Example A 100% 80% 50% (B) Example B 80% (content as Polycin XP D-2000 80% weight %) Polycin GR-35 80% Composition (B2): Pripol 2033 20% 20% 20% 20% 100% 50% NCO NCO/OH equivalent 6.4 4.2 4.2 4.2 4.2 2.7 3.3 Component molar ratio Content of NCO 11.8% 11.7% 13.9% 11.7% 12.0% 11.6% 11.4% group (weight %) Mixture of Viscosity at 40 C. 930 1000 400 1100 1000 3300 2300 the NCO and (mPa .Math. s) OH Content of 71% 69% 61% 69% 69% 61% 65% components renewable starting materials 180 Peeling Film A 0.94 0.93 1.2 0.78 0.77 NC** NC** on bilayer Film B before 3.7 4.1 ND* 4.0 4.1 NC** NC** (in N/15 mm) pasteurization Film B after 3.9 3.7 ND* 3.1 3.6 NC** NC** pasteurization *ND = not determined **NC = not concerned (mixture too viscous to prepare the bilayer)