STYRENE BUTADIENE BLOCK COPOLYMERS WITH LOW CROSSLINKING

Abstract

A thermoplastic polymer composition (I) comprising: (A) block copolymer A comprising A1: 60 to 95 wt.-% vinyl aromatic monomer, and A2: 5 to 40 wt.-% conjugated diene; (B) a stabilizer combination consisting of: B1: 200 to 2500 ppm 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino) phenol, B2: 500 to 2500 ppm 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate and/or 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and B3: 500 to 2000 ppm tris(2,4-di-tert.-butylphenyl)phosphite; (C) 0 to 5000 ppm stabilizers different from (B1), (B2) and (B3); (D) optionally additives and/or processing aids other than (B) and (C), (E) optionally thermoplastic polymer TP other than block copolymer A, a process for its preparation, and its use for the preparation of shrink films is described.

Claims

1-24. (canceled)

25. A thermoplastic polymer composition (I) comprising components (A), (B), and optionally (C), (D), and/or (E): (A) at least one block copolymer A comprising: A1: 60 to 95 wt.-%, based on block copolymer A, polymerized units of at least one vinyl aromatic monomer; and A2: 5 to 40 wt.-%, based on block copolymer A, polymerized units of at least one conjugated diene; (B) a stabilizer combination consisting of stabilizer components (B1), (B2), and (B3): B1: 1500 to 2100 ppm (0.150 to 0.210 wt.-%), based on the entire thermoplastic polymer composition (I), 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino) phenol; B2: 1000 to 1600 ppm (0.100 to 0.160 wt.-%), based on the entire thermoplastic polymer composition (I), 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methyl phenyl acrylate, or mixtures thereof; and B3: 1000 to 1600 ppm (0.100 to 0.160 wt.-%), based on the entire thermoplastic polymer composition (I), tris(2,4-di-tert.-butylphenyl)phosphite; (C) 0 to 5000 ppm (0 to 0.500 wt.-%), based on the entire thermoplastic polymer composition (I), of one or more stabilizers different from (B1), (B2), and (B3); (D) optionally, one or more additives and/or processing aids other than (B) and (C); and (E) optionally, at least one thermoplastic polymer TP other than block copolymer A.

26. The thermoplastic polymer composition (I) of claim 25, wherein stabilizer combination (B) consists of stabilizer components (B1), (B2), and (B3) in the following amounts: B1: 1900 to 2100 ppm (0.190 to 0.210 wt.-%); B2: 1400 to 1600 ppm (0.140 to 0.160 wt.-%); and B3: 1400 to 1600 ppm (0.140 to 0.160 wt.-%).

27. The thermoplastic polymer composition (I) of claim 25, wherein component B2 is 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

28. The thermoplastic polymer composition (I) of claim 25, wherein component C is pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]-propionate.

29. The thermoplastic polymer composition (I) of claim 25, wherein component C is not present.

30. The thermoplastic polymer composition (I) of claim 25, wherein block copolymer A comprises: A1: 60 to 80 wt.-%, based on block copolymer A, polymerized units of at least one vinyl aromatic monomer; and A2: 20 to 40 wt.-%, based on block copolymer A, polymerized units of at least one conjugated diene.

31. The thermoplastic polymer composition (I) of claim 25, wherein block copolymer A comprises: at least one hard polymer block S composed of from 95 to 100 wt.-% of vinylaromatic monomers and from 0 to 5 wt.-% of conjugated dienes, optionally, one or more hard copolymer blocks (B/S), each composed of conjugated dienes and vinylaromatic monomers having a B/S-ratio (diene:vinylaromatic monomer) less than 0.25, and a glass transition temperature Tg (ISO 11357-2) greater than 37° C., and optionally, one or more soft blocks B composed of 100 wt.-% conjugated diene, and optionally, one or more soft copolymer blocks (S/B), each composed of vinylaromatic monomers and of conjugated dienes having an S/B-ratio (vinylaromatic monomer:diene) less than 0.5, and having a glass transition temperature Tg (ISO 11357-2) less than 37° C.

32. The thermoplastic polymer composition (I) of claim 31, wherein the hard and soft copolymer blocks (B/S) and (S/B) are random copolymer blocks.

33. The thermoplastic polymer composition (I) of claim 31, wherein block copolymer A comprises: at least one hard block S composed of from 95 to 100 wt.-% of vinylaromatic monomers, and from 0 to 5 wt.-% of conjugated dienes, one or more copolymer blocks (B/S).sub.A, each composed of from 65 to 95 wt.-% of vinylaromatic monomers and from 35 to 5 wt.-% of conjugated dienes, and having a glass transition temperature Tg.sub.A (ISO 11357-2) of from 40 to 90° C., and one or more copolymer blocks (B/S).sub.B, each composed of from 1 to 60 wt.-% of vinylaromatic monomers and from 99 to 40 wt.-% of conjugated dienes, and having a glass transition temperature Tg.sub.B (ISO 11357-2) of from −90 to −40° C.

34. The thermoplastic polymer composition (I) of claim 25, wherein block copolymer A is a star-shaped block copolymer.

35. The thermoplastic polymer composition (I) of claim 34, wherein the stars of block copolymer A are characterized by: short branches of structure S.sub.e-(B/S).sub.B˜ and long branches of structure (B/S).sub.A-Si-(B/S).sub.B˜, linked to one another via a coupling agent by way of (B/S).sub.B; short branches of structure S.sub.e-(B/S).sub.B˜ and long branches of structure S.sub.e′-(B/S).sub.A-S.sub.i-(B/S).sub.B˜, linked to one another via a coupling agent by way of (B/S).sub.B; short branches of structure S.sub.e-(B/S).sub.B-S.sub.f˜ and long branches of structure (B/S)A-S.sub.i-(B/S).sub.B-S.sub.f˜, linked to one another via a coupling agent by way of S.sub.f; or short branches of structure S.sub.e-(B/S).sub.B-S.sub.f˜ and long branches of structure S.sub.e′-(B/S).sub.A-S.sub.i-(B/S).sub.B-S.sub.f˜, linked to one another via a coupling agent by way of S.sub.f, wherein, S.sub.e and S.sub.i are blocks S having a number-average molar mass M.sub.n (determined by gel permeation chromatography in THF, using polystyrene as standard) of 5000 to 30000 g/mol, S.sub.f and S.sub.e′ are blocks S having M.sub.n of less than 4000 g/mol, (B/S).sub.A is a copolymer block composed of from 65 to 95 wt.-% of vinylaromatic monomers and from 35 to 5 wt.-% of conjugated dienes, and a glass transition temperature Tg.sub.A (ISO 11357-2) of from 40 to 90° C., and (B/S).sub.B is a copolymer block composed of from 1 to 60 wt.-% of vinylaromatic monomers and from 99 to 40 wt.-% of conjugated dienes, and a glass transition temperature Tg.sub.B (ISO 11357-2) of from −90 to −40° C., M.sub.n of copolymer block (B/S).sub.A is 30000 to 300000, and M.sub.n of copolymer block (B/S).sub.B is 5000 to 50000 g/mol.

36. The thermoplastic polymer composition (I) of claim 25, wherein thermoplastic polymer TP is at least one polymer selected from: styrene polymers, polymethacrylates, polyesters, polyolefins, polyvinyl chloride (PVC), semicrystalline materials, polyacrylates, or thermoplastic elastomers (TPE).

37. A process for the preparation of the thermoplastic polymer composition (I) of claim 25, the process comprising: i) sequential anionic polymerization of a monomer composition comprising A1 and A2, to obtain a plurality of living anionic polymer chains; then ii) chain termination or coupling of the living anionic polymer chains produced in step i) to obtain block copolymer A; then iii) optionally, addition of alcohol, CO.sub.2, and water; and after step ii) or iii) iv) addition of stabilizer components (B1), (B2), and (B3), and, if present, addition of stabilizers (C), additives and/or processing aids (D), and/or component (E), to obtain the thermoplastic polymer composition (I).

38. A process for the preparation of shrink films, wherein the thermoplastic polymer composition (I) of claim 25 is formed to films by thermoforming, extrusion, injection molding, calendaring, blow molding, or compression molding.

39. A shrink film produced from the thermoplastic polymer composition (I) of claim 25.

40. A shrink film comprising the thermoplastic polymer composition (I) of claim 25.

41. The thermoplastic polymer composition (I) of claim 25, wherein the at least one vinyl aromatic monomer of A1 is styrene, and the at least one conjugated diene of A2 is butadiene or isoprene.

42. The thermoplastic polymer composition (I) of claim 30, wherein A1 is 60 to 76 wt.-%, based on block copolymer A, polymerized units of at least one vinyl aromatic monomer, and A2 is 24 to 40 wt.-%, based on block copolymer A, polymerized units of at least one conjugated diene.

43. The thermoplastic polymer composition (I) of claim 31, wherein the B/S-ratio is 0.1 to 0.2, and the S/B-ratio is 0.15 to 0.45.

44. The thermoplastic polymer composition (I) of claim 33, wherein copolymer blocks (B/S).sub.B are each composed of from 1 to 30 wt.-% of vinylaromatic monomers and of from 99 to 70 wt.-% of conjugated dienes, and have a glass transition temperature Tg.sub.B of −80 to −65° C.

Description

EXAMPLES

[0181] Styrene-Butadiene Block-Copolymer A

[0182] In a batch reactor (stainless steel reactor, stirred, 50 m.sup.3) 21300 L of cyclohexane at 40° C. was used as initial charge and 165 L styrene (S1) was added at 20 m.sup.3/h. When 16 L of S1 had been dosed, 30.00 L of a 1.4 M sec-butyllithium solution (BuLi 1) for initiation and 3.88 L of a 5 wt % potassium tert-amylate solution in cyclohexane as randomizer had been dosed at once. The reaction was allowed to proceed under continuous stirring to complete monomer consumption (identified by no further temperature increase of the reaction mixture).

[0183] In a next step, 3139 L styrene (S2) and 538 L butadiene (B1) were added together and the polymerization reaction, under continuous stirring, was allowed to run to complete monomer consumption (identified by no further temperature increase of the reaction mixture). After complete monomer consumption, the polymerization mixture was cooled by means of reflux cooling to a temperature below 70° C.

[0184] In a next step, 65.26 L of a 1.4 M sec-butyllithium solution (BuLi 2) for initiation and 8.73 L of a 5 wt % potassium tert-amylate solution in cyclohexane as randomizer had been dosed at once.

[0185] In a next step, 1758 L styrene (S3) was added and the polymerization reaction, under continuous stirring, was allowed to run to complete monomer consumption (identified by no further temperature increase of the reaction mixture). After complete monomer consumption, the polymerization mixture was cooled by means of reflux cooling to a temperature below 56° C.

[0186] In a next step, 677 L styrene (S4) and 2956 L butadiene (B2) were added together and the polymerization reaction, under continuous stirring, was allowed to run to complete monomer consumption (identified by no further temperature increase of the reaction mixture). After complete monomer consumption, the polymerization mixture was cooled by means of reflux cooling to a temperature below 90° C.

[0187] In a next step, 121 L styrene (S5) was added and the polymerization reaction, under continuous stirring, was allowed to run to complete monomer consumption (identified by no further temperature increase of the reaction mixture).

[0188] Then, 10 minutes after the last complete monomer consumption, 12.7 L Edenol® D82 (epoxydized soybean oil) was added to the block copolymer polymer solution and allowed to react for 10 minutes while stirring.

[0189] Then, the reaction mixture was stabilized by acidification with 0.06 phm (=parts (g) per 100 g monomers) demineralized water and a 0.43 phm CO.sub.2 gas stream.

[0190] In a next step, samples of this block copolymer solution were taken. Then to each polymer sample stabilizers were added in amounts (based on the polymer content in the solution) as shown in Table 1 and each sample was homogenized by means of stirring to obtain a block copolymer composition as defined in Table 1. Thereafter, the cyclohexane solvent was removed from the block copolymer composition in a co-rotating degassing twin screw extruder.

[0191] Irganox® 1010, Sumilizer® GS, Irgafos® 168, Irganox® 1141 and Irganox® 565 were received from BASF SE, Germany. Hostanox® O3 and Hostanox SE10 were received from Clariant International Ltd, Switzerland. CPD-650 was received from Guangdong Xinhuayue Petrochemical Incorporated Company.

TABLE-US-00001 TABLE 1 Final Final pressure pressure Irganox ® Sumilizer ® Irgafos ® Irganox ® Irganox ® Hostanox ® Hostanox ® CPD- Total at 250° at 270° Polymer 1010 GS 168 1141 565 O3 SE10 650 Sum C. C. Sample ppm ppm ppm ppm ppm ppm ppm ppm ppm MPa MPa Inventive A 0 1500 1500 0 2000 0 0 0 5000 2.1  9.9 example Inventive B 0 1500 1500 0 2000 0 0 0 5000 2.1 10.3 example Inventive C 1000 1500 1500 0 1000 0 0 0 5000 2.3 / example Comparative D 2000 1500 1500 0 0 0 0 0 5000 2.6 11.2 example Comparative E 750 1500 1500 0 0 1250 0 0 5000 2.6 / example Comparative F 0 1500 1500 2000 0 0 0 0 5000 3.0 / example Comparative G 1000 1500 1500 0 0 0 0 1000 5000 3.1 / example Comparative H 750 1500 1500 0 0 0 1250 0 5000 3.4 / example Inventive X 1750 1500 1500 0 250 0 0 0 5000 10.3 example ppm = parts per million (mg/kg) based on entire thermoplastic polymer composition (I)

[0192] In a next step, the stabilized block copolymer samples were subjected to a capillary rheology experiment to evaluate the resistance of the product against crosslinking upon energy input. The material was loaded to the barrel of the capillary rheometer at 250° C. and preheated for 3 minutes (Inventive examples A, B, C and comparative examples D to H). Next, a force was applied at ram (piston) to push the material through a die of 16 mm length and 1 mm diameter (L/D=16) at a constant shear rate of 100 s.sup.−1 over a time of 63 min. During this experiment, the pressure at the die is measured to maintain this shear rate. The more crosslinking appears in the sample during the experiment, the more difficult it becomes to press the material through the die at a constant shear rate. This is reflected as a pressure increase at the die. Therefore, the pressure at the die is a direct correlation for the degree of crosslinking in the sample. The higher the final pressure, the higher is the degree of crosslinking.

[0193] Furthermore, a sample of inventive examples A, B, comparative example D and of inventive example X, respectively, was loaded to the barrel of the capillary rheometer at 270° C. and preheated for 3 minutes and then a force was applied to each sample as hereinbefore described.

[0194] The final pressure per sample can be found in Table 1 and FIGS. 1 and 2.

[0195] FIG. 1: The Y-axis of the graph shows the pressure in MPa and the X-axis shows the time in minutes. The measured values (at 250° C.) obtained for polymer samples A to H are shown by different continuous, dashed and dotted lines.

[0196] FIG. 2: The Y-axis of the graph shows the pressure in MPa and the X-axis shows the time in minutes. The measured values (at 270° C.) obtained for polymer samples A; B, D and X are shown by different continuous, dashed and dotted lines.

[0197] Samples A and B have the same composition and give an indication of the consistency of the experiment. Table 1 and FIGS. 1 and 2 show that the final pressure of the inventive examples according to samples A, B,C and X is significantly lower than the final pressure obtained for comparative examples (samples D to H).

[0198] Thus, it has been proven that by use of the stabilizer combination as used in the block copolymer composition according to the invention (samples A, B, C, and X) the cross-linking of the block copolymers can be reduced.