PVC foam processing aid, method for preparing the same and polyvinyl chloride resin composition comprising the same

Abstract

Disclosed are a PVC foam processing aid, a method for preparing the same, and a polyvinyl chloride resin composition comprising the same. More specifically, provided are a PVC foam processing aid and a polyvinyl chloride resin composition exhibiting superior aggregation property and improving foam moldability of polyvinyl chloride (PVC) resins, prepared therefrom.

Claims

1. A polyvinylchloride (PVC) foam processing aid comprising: 50 to 90% by weight of a styrene-acrylonitrile copolymer; and 50 to 10% by weight of an alkyl methacrylate-alkyl acrylate copolymer, wherein the styrene-acrylonitrile copolymer has a weight average molecular weight (Mw) of 2,000,000 to 5,000,000 g/mol, and the alkyl methacrylate-alkyl acrylate copolymer has a weight average molecular weight (Mw) of 200,000 to 1,000,000 g/mol, wherein the alkyl methacrylate-alkyl acrylate copolymer surrounds the styrene-acrylonitrile copolymer, and wherein the amount of an acrylonitrile monomer and a styrene monomer in the styrene-acrylonitrile copolymer is 13 to 28% by weight and 38 to 66% by weight, respectively, based on 100% by weight of the total monomer content of the PVC foam processing aid, and wherein the amount of an alkyl acrylate monomer and an alkyl methacrylate monomer in the alkyl methacrylate-alkyl acrylate copolymer is 2.5 to 10% by weight and 7.5 to 40% by weight, respectively, based on 100% by weight of the total monomer content of the PVC foam processing aid.

2. The PVC foam processing aid according to claim 1, wherein the styrene-acrylonitrile copolymer comprises a styrene monomer and an acrylonitrile monomer at a weight ratio of 50 to 80:50 to 20.

3. The PVC foam processing aid according to claim 1, wherein the styrene-acrylonitrile copolymer is obtained by polymerizing the styrene and acrylonitrile monomers with the alkyl methacrylate monomer.

4. The PVC foam processing aid according to claim 3, wherein the styrene-acrylonitrile copolymer comprises 50 to 70% by weight of the styrene monomer, 15 to 25% by weight of the acrylonitrile monomer and 15 to 25% by weight of the alkyl methacrylate monomer, based on 100% by weight of the styrene-acrylonitrile copolymer and is obtained by polymerizing the contents of the monomers.

5. The PVC foam processing aid according to claim 1, wherein the alkyl methacrylate-alkyl acrylate copolymer comprises 60 to 90% by weight of the alkyl methacrylate monomer and 10 to 40% by weight of the alkyl acrylate monomer, based on 100% by weight of the alkyl methacrylate-alkyl acrylate copolymer and is obtained by polymerizing the contents of the monomers.

6. The PVC foam processing aid according to claim 5, wherein the alkyl acrylate monomer comprises at least one selected from the group consisting of methyl acrylate, ethyl acrylate, n-butyl acrylate, lauryl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate.

7. The PVC foam processing aid according to claim 3, wherein the alkyl methacrylate monomer comprises at least one selected from the group consisting of methyl methacrylate, n-butyl methacrylate, lauryl methacrylate, stearyl methacrylate, tridecyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate and cyclohexyl methacrylate.

8. The PVC foam processing aid according to claim 2, wherein the styrene monomer comprises at least one selected from the group consisting of styrene, -methyl styrene, t-butyl styrene, chlorostyrene, and p-methyl styrene.

9. The PVC foam processing aid according to claim 2, wherein the acrylonitrile monomer comprises at least one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, -chloronitrile, and -cyanoethyl acrylonitrile.

10. A method for preparing a polyvinylchloride (PVC) foam processing aid comprising: polymerizing a styrene monomer with an acrylonitrile monomer in the presence of a polymerization initiator to obtain a styrene-acrylonitrile copolymer having a weight average molecular weight (Mw) of 2,000,000 to 5,000,000 g/mol; and adding 7.5 to 40% by weight of an alkyl methacrylate monomer and 2.5 to 10% by weight of an alkyl acrylate monomer to 50 to 90% by weight of the styrene-acrylonitrile copolymer and performing polymerization in the presence of a polymerization initiator to obtain a polymer having a structure in which an alkyl methacrylate-alkyl acrylate copolymer having a weight average molecular weight (Mw) of 200,000 to 1,000,000 g/mol surrounds the styrene-acrylonitrile copolymer.

11. The method according to claim 10, wherein the polymerizing the styrene monomer with the acrylonitrile monomer comprises polymerizing 50 to 70% by weight of the styrene monomer, 15 to 25% by weight of the acrylonitrile monomer and 15 to 25% by weight of the alkyl methacrylate monomer, based on 100% by weight in total of the styrene-acrylonitrile copolymer.

12. The method according to claim 10, further comprising aggregating the polymer to obtain a powder.

13. A polyvinyl chloride resin composition comprising: a polyvinyl chloride resin; and the PVC foam processing aid according to claim 1.

14. The polyvinyl chloride resin composition according to claim 13, wherein the composition comprises 100 parts by weight of the polyvinyl chloride resin and 1 to 20 parts by weight of the PVC foam processing aid.

15. The PVC foam processing aid according to claim 5, wherein the alkyl methacrylate monomer comprises at least one selected from the group consisting of methyl methacrylate, n-butyl methacrylate, lauryl methacrylate, stearyl methacrylate, tridecyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate and cyclohexyl methacrylate.

16. The PVC foam processing aid according to claim 3, wherein the styrene monomer comprises at least one selected from the group consisting of styrene, -methyl styrene, t-butyl styrene, chlorostyrene, and p-methyl styrene.

17. The PVC foam processing aid according to claim 4, wherein the styrene monomer comprises at least one selected from the group consisting of styrene, -methyl styrene, t-butyl styrene, chlorostyrene, and p-methyl styrene.

18. The PVC foam processing aid according to claim 3, wherein the acrylonitrile monomer comprises at least one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, -chloronitrile, and -cyanoethyl acrylonitrile.

19. The PVC foam processing aid according to claim 4, wherein the acrylonitrile monomer comprises at least one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, -chloronitrile, and -cyanoethyl acrylonitrile.

Description

BEST MODE

(1) Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples are not to be construed as limiting the scope of the invention.

Examples 1 to 5 and Comparative Examples 1 to 4

Example 1

(2) 160 parts by weight of deionized water, 0.8 parts by weight of an emulsifier (KAO Cooperation, Latemul ASK), 0.01 parts by weight of sodium ethylenediaminetetraacetate and 0.001 parts by weight of ferrous sulfate were added to a 5 L polymerization reactor equipped with a stirrer, a nitrogen gas was sufficiently charged in the reactor and the temperature was elevated to 40 C.

(3) Then, 52.5 parts by weight of styrene and 22.5 parts by weight of acrylonitrile were added to the reactor, 0.05 parts by weight of sodium formaldehyde sulfoxylate and 0.005 parts by weight of tert-butyl hydroperoxide were then added thereto and polymerization was performed for 6 hours to obtain a first step copolymer latex having an average particle diameter of 120 nm (polymerization conversion ratio: 96%, Mw of first step copolymer: 3,500,000 g/mol).

(4) The average particle diameter was measured using a submicron particle sizer (NICOMP 380, Particle Sizing Systems (PSS) Inc.).

(5) In a second step, 0.2 parts by weight of an emulsifier (KAO COOPERATION, Latemul ASK), 0.002 parts by weight of sodium ethylenediaminetetraacetate and 0.0002 parts by weight of ferrous sulfate were added to the reactor, 20 parts by weight of methyl methacrylate and 5 parts by weight of butyl acrylate were added thereto as second step monomers, 0.01 parts by weight of sodium formaldehyde sulfoxylate and 0.005 parts by weight of tert-butyl hydroperoxide were added thereto and polymerization was performed at 40 C. for 4 hours to obtain a second step copolymer latex having an average particle diameter of 140 nm (polymerization conversion ratio: 98%, Mw of second step copolymer: 600,000 g/mol).

(6) The obtained latex was aggregated with calcium chloride, washed with water and dried to obtain a powder.

Example 2

(7) The same process as in Example 1 was repeated, except that 17 parts by weight of methyl methacrylate and 8 parts by weight of butyl acrylate were added as the second step monomers. In this case, the second step copolymer had a Mw of 600,000 g/mol.

Example 3

(8) The same process as in Example 1 was repeated, except that 59.5 parts by weight of styrene and 25.5 parts by weight of acrylonitrile were added as the first step monomers and 12 parts by weight of methyl methacrylate and 3 parts by weight of butyl acrylate were added as the second step monomers.

(9) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 500,000 g/mol.

Example 4

(10) The same process as in Example 1 was repeated, except that 42 parts by weight of styrene and 18 parts by weight of acrylonitrile were added as the first step monomers and 32 parts by weight of methyl methacrylate and 8 parts by weight of butyl acrylate were added as the second step monomers.

(11) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 700,000 g/mol.

Example 5

(12) The same process as in Example 1 was repeated, except that 42 parts by weight of styrene, 18 parts by weight of acrylonitrile and 15 parts by weight of methyl methacrylate were added as the first step monomers.

(13) In this case, the first step copolymer had a Mw of 3,200,000 g/mol and the second step copolymer had a Mw of 500,000 g/mol.

Comparative Example 1

(14) The same process as in Example 1 was repeated, except that 70 parts by weight of styrene and 30 parts by weight of acrylonitrile were added as the first step monomers and the obtained first step copolymer latex was aggregated with calcium chloride, washed with water and dried to obtain a powder, without polymerization of the second step.

(15) In this case, the first step copolymer had a Mw of 3,500,000 g/mol.

Comparative Example 2

(16) The same process as in Example 1 was repeated, except that 80 parts by weight of methyl methacrylate and 20 parts by weight of butyl acrylate were added as the first step monomers and the obtained first step copolymer latex was aggregated with calcium chloride, washed with water and dried to obtain a powder, without polymerization of the second step.

(17) In this case, the first step copolymer had a Mw of 700,000 g/mol.

Comparative Example 3

(18) The same process as in Example 1 was repeated, except that 0.04 parts by weight of tert-butyl hydroperoxide was added as an initiator and polymerization was performed at 60 C. for 3 hours during polymerization of the second step.

(19) In this case, the second step copolymer had a Mw of 100,000 g/mol.

Comparative Example 4

(20) The same process as in Example 1 was repeated, except that 0.01 parts by weight of tert-butyl hydroperoxide was added as an initiator and polymerization was performed at 60 C. for 4 hours during polymerization of the first step.

(21) In this case, the first step copolymer had a Mw of 1,800,000 g/mol and the second step copolymer had a Mw of 700,000 g/mol.

Comparative Example 5

(22) The same process as in Example 1 was repeated, except that 0.002 parts by weight of tert-butyl hydroperoxide was added as an initiator and polymerization was performed at 35 C. for 6 hours during polymerization of the second step.

(23) In this case, the second step copolymer had a Mw of 1,200,000 g/mol.

(24) 4 parts by weight of each polymer powder obtained in Examples 1 to 5 and Comparative Examples 1 to 5 was mixed with 100 parts by weight of a polyvinyl chloride resin (LG080, produced by LG Chem. LTD.), 4 parts by weight of a thermal stabilizer (OTL-9, produced by Sunkyung Chemical Co., Ltd.), 7 parts by weight of calcium carbonate, 2 parts by weight of a lubricant, 2 parts by weight of TiO.sub.2, and 0.7 parts by weight of a foaming agent (azodicarbonamide) using a Hensel mixer while heating to 115 C., and was foam-molded using a Haake twin extruder equipped with a rectangular slit die to produce a test specimen having a thickness of 5 mm and an area of 30 mm.

(25) Physical values measured in accordance with the test items are shown in the following Table 1.

(26) <Test Items>

(27) Aggregation temperature ( C.): a temperature at which a powder content of a copolymer latex passing through a 200-mesh sieve (size: 0.075 mm), after aggregation and drying, reached 20% or less was measured (powdery polymer having a suitable size cannot be produced when aggregation temperature is excessively high or low).

(28) Torque upon foaming extrusion (%), melt pressure (bar), melt temperature ( C.): a value measured in a Hakke foaming extruder (extrusion temperature: C1/C2/A/D=170/178/180/178 C., screw rate: 25 rpm).

(29) Amount of extruded product upon foaming extrusion (g/min): a weight of molded product obtained from the extruder for one minute upon foam molding.

(30) Specific gravity of foams upon foaming extrusion (g/cc): a value measured using a specific gravity meter.

(31) Size of foam cells upon foaming extrusion (mm): an average of 50 cell size values measured using an optical microscope.

(32) TABLE-US-00001 TABLE 1 Aggrega- Amount of Specific Size of tion tem- Melt extruded gravity foam perature Torque pressure product of foams cells Items ( C.) (%) (Bar) (g/min) (g/cc) (mm) Ex. 1 71 79 124.2 68.3 0.427 101 Ex. 2 66 84 125.0 68.7 0.466 97 Ex. 3 80 80 121.8 67.7 0.489 91 Ex. 4 70 84 125.8 68.8 0.471 99 Ex. 5 72 87 135.7 68.5 0.409 111 Comp. 72 112 62.5 0.713 69 Ex. 1 Comp. 64 70 104.7 66.1 0.719 62 Ex. 2 Comp. 68 70 115.5 67.0 0.612 83 Ex. 3 Comp. 69 76 114.0 64.0 0.580 74 Ex. 4 Comp. 76 75 114.7 61.1 0.655 72 Ex. 5

(33) As can be seen from Table 1 above, Examples 1 to 5 enabled easy formation of powders at temperatures of 90 C. or less and facilitated foaming extrusion, thus providing a high amount of extruded product, improved foaming properties and low specific gravity of foams.

(34) Comparative Example 1 wherein a second step copolymer with a suitable molecular weight was not used exhibited high foam specific gravity and a low extruded product amount. In addition, powder size was disadvantageously excessively small due to high Tg.

(35) Comparative Example 2 wherein a styrene-acrylonitrile copolymer with a high-molecular weight was not used in the first step, Comparative Example 4 wherein a molecular weight of the copolymer of the first step was low exhibited deterioration in foaming properties, and Comparative Examples 3 and 5 wherein the molecular weight of the second step was excessively high or low exhibited deterioration in foaming properties.

(36) An additional test was performed in the same manner as in Example 1 in order to confirm variation in physical properties according to variations in monomer contents and molecular weights and results are shown in the following Table 2.

Comparative Example 6

(37) The same process as in Example 1 was repeated, except that 66.5 parts by weight of styrene and 28.5 parts by weight of acrylonitrile were added as first step monomers and 4 parts by weight of methyl methacrylate and 1 part by weight of butyl acrylate were added as second step monomers.

(38) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 300,000 g/mol.

Comparative Example 7

(39) The same process as in Example 1 was repeated, except that 28 parts by weight of styrene and 12 parts by weight of acrylonitrile were added as first step monomers and 48 parts by weight of methyl methacrylate and 12 parts by weight of butyl acrylate were added as second step monomers.

(40) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 900,000 g/mol.

Comparative Example 8

(41) The same process as in Example 1 was repeated, except that 23 parts by weight of methyl methacrylate and 2 parts by weight of butyl acrylate were added as second step monomers.

(42) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 500,000 g/mol.

Comparative Example 9

(43) The same process as in Example 1 was repeated, except that 12.5 parts by weight of methyl methacrylate and 12.5 parts by weight of butyl acrylate were added as second step monomers.

(44) In this case, the first step copolymer had a Mw of 3,500,000 g/mol and the second step copolymer had a Mw of 700,000 g/mol.

Comparative Example 10

(45) The same process as in Example 1 was repeated, except that 67.5 parts by weight of styrene and 7.5 parts by weight of acrylonitrile were added as first step monomers.

(46) In this case, the first step copolymer had a Mw of 3,700,000 g/mol and the second step copolymer had a Mw of 600,000 g/mol.

Comparative Example 11

(47) The same process as in Example 1 was repeated, except that 37.5 parts by weight of styrene and 37.5 parts by weight of acrylonitrile were added as first step monomers.

(48) In this case, the first step copolymer had a Mw of 2,500,000 g/mol and the second step copolymer had a Mw of 600,000 g/mol.

(49) TABLE-US-00002 TABLE 2 Aggrega- Amount of Specific Size of tion tem- Melt extruded gravity foam perature Torque pressure product of foams cells Items ( C.) (%) (Bar) (g/min) (g/cc) (mm) Comp. 98 76 113.8 62.3 0.627 77 Ex. 6 Comp. 68 76 114.2 61.5 0.604 78 Ex. 7 Comp. 79 120.7 66.0 0.487 95 Ex. 8 Comp. 57 76 113.4 61.8 0.599 74 Ex. 9 Comp. 72 72 107.1 61.2 0.724 66 Ex. 10 Comp. 69 76 114.2 61.0 0.609 84 Ex. 11

(50) As can be seen from Table 2 above, Comparative Examples 6 and 7 wherein the content of the copolymer of the second step was excessively high or low had problems of high foam specific gravity and low extruded product amount. In addition, Comparative Example 6 wherein the content of the copolymer of the second step was insufficient and Comparative Example 8 wherein the content of butyl acrylate among the monomers of the second step was low had a problem of excessively small powder size due to high Tg.

(51) In addition, Comparative Example 9 wherein the content of butyl acrylate among the monomers of the second step was high enabled easy aggregation, but had a problem of deteriorated foaming properties.

(52) Furthermore, Comparative Examples 10 and 11 wherein the content of acrylonitrile in the copolymer of the first step was high or low exhibited deterioration in foaming properties due to low compatibility with PVC.