NON-STICKY, SOFT AND TRANSPARENT STYRENIC THERMOPLASTIC ELASTOMERS

Abstract

Thermoplastic elastomer compositions can be use for medical applications, Comprising: a) 97.1 to 90.9 wt.-% star-shaped block copolymer A with identical arms of the structure [S.sub.1-(S/B).sub.k-(S/B).sub.l-(S/B).sub.m-S2].sub.n-X, where S.sub.1 and S.sub.2 are vinylaromatic hard polymer and S/B are soft random vinylaromatic/diene copolymer blocks; X is a coupling center; and b) 2.9 to 9.1 wt.-% plasticizer B.

Claims

1-17. (canceled)

18. A thermoplastic elastomer composition comprising components a), b), and c): a) 97.1 to 90.9 wt.-% of at least one star-shaped block copolymer A of the structure
[S.sub.1-(S/B).sub.k-(S/B).sub.l-(S/B).sub.m-S.sub.2].sub.n-X  (I), where S.sub.1 and S.sub.2 are polymer blocks made from at least one vinylaromatic monomer and S/B are random copolymer blocks made from at least one vinylaromatic monomer and at least one diene forming a soft phase; X is a coupling center derived from a polyfunctional coupling agent; b) 2.9 to 9.1 wt.-% of at least one plasticizer B; and c) 0 to 2 wt.-% of further additives C; wherein the sum of components a), b) and c) is 100 wt-%; the arms S.sub.1-(S/B).sub.k-(S/B).sub.l-(S/B).sub.m-S.sub.2 are identical; the proportion of the blocks S.sub.1 and S.sub.2 (forming a hard phase), based on the entire block copolymer A, is from 24 to 40 wt-%; the vinylaromatic monomer/diene (=S/B) ratio of all of the blocks (S/B) is from 1/0.45 to 1/2.5; the S/B-ratio of the blocks (S/B).sub.k, (S/B).sub.l and (S/B).sub.m is different from each other; the S/B-ratio of the blocks (S/B).sub.k and (S/B).sub.m is lower than the S/B-ratio of the block(s) (S/B).sub.l; the weight ratio of blocks S2/S1 is from 0.1 to 0.8; the weight average molar mass M.sub.w of the block copolymer A is from 200.000 to 350.000 g/mol; n is a natural number from 1 to 8; k and m are each 1; and l is a natural number of at least 1.

19. The thermoplastic elastomer composition according to claim 18 comprising components a), b), and c) in the following amounts: a) 96.2 to 91.7 wt.-%; b) 3.8 to 8.3 wt.-%; and c) 0 to 2 wt.-%.

20. The thermoplastic elastomer composition according to claim 18, wherein the plasticizer B is mineral oil.

21. The thermoplastic elastomer composition according to claim 18 which melt mass flow index (measured on a polymer melt at 200° C. and 5 kg load according to ISO 1133-1:2011) is in the range of from 8 to 16 cm.sup.3/10 min.

22. The thermoplastic elastomer composition according to claim 18, wherein n is a natural number from 3 to 5.

23. The thermoplastic elastomer composition according to claim 18, wherein X is a coupling center derived from epoxidized linseed oil or epoxidized soybean oil.

24. Thermoplastic elastomer composition according to claim 18, wherein M.sub.w of the block copolymer A is from 210.000 to 320.000 g/mol.

25. The thermoplastic elastomer composition according to claim 18, wherein Mw of the polymer block S.sub.1 is in the range of from 18.000 to 36.000 g/mol; and Mw of the polymer block S.sub.2 is in the range of from 4000 to 8100 g/mol.

26. The thermoplastic elastomer composition according to claim 18, wherein the weight ratio of blocks S.sub.2/S.sub.1 of block copolymer A is from 0.1 to 0.6.

27. The thermoplastic elastomer composition according to claim 18, wherein the S/B-ratio of the copolymer block (S/B).sub.k is from 0.5 to 1.0; the S/B-ratio of the copolymer block(s) (S/B).sub.l is from 0.5 to 1.2; and the S/B-ratio of the copolymer block (S/B).sub.m is from 0.3 to 0.8.

28. The thermoplastic elastomer composition according to claim 18, wherein the weight average molar mass M.sub.w of the copolymer blocks (S/B).sub.k, (S/B).sub.l and (S/B).sub.m is different from each other; Mw (S/B).sub.k is in the range of from 13.800 to 26.900 g/mol; Mw (S/B).sub.l is in the range of from 21.200 to 41.000 g/mol; and Mw (S/B).sub.m is in the range of from 11.500 to 23.000 g/mol.

29. A process for the preparation of a thermoplastic elastomer composition according to claim 18, wherein component a) is introduced continuously into an extruder and then component b) and optionally further components c) are metered in.

30. A process for the preparation of a thermoplastic elastomer composition according to claim 18, wherein component b) and optional component c)—as such or in solution—are added into a solution of block copolymer A, then to homogenize the liquids, and subsequently to free the product from the solvent.

31. Shaped articles produced from the thermoplastic elastomer composition according to claim 18.

32. A method of using a thermoplastic elastomer composition according to claim 18 for medical applications.

33. A star-shaped block copolymer A according to claim 18.

34. A process for the preparation of block copolymer A of formula (I) according to claim 18 characterized by i) a single initiation, ii) first addition and polymerization of vinyl aromatic monomer, iii) at least 3 times addition and polymerization of a vinyl aromatic monomer and diene mixture, iv) second addition and polymerization of vinyl aromatic monomer, and v) a coupling step after the addition and polymerization of the vinylaromatic monomers of the last polymer block.

Description

EXAMPLES

Block Copolymer A

[0131] A star-shaped block copolymer A of the structure [S.sub.1-(S/B).sub.k-(S/B).sub.l-(S/B).sub.m-S.sub.2].sub.n-X was prepared by sequential anionic polymerization of styrene (monomers 51 to S5) and butadiene (monomers B1 to B3) (cp. Table 1), and subsequent coupling using epoxidized soybean oil. 25670 ml of cyclohexane were used as initial charge (ic) and titrated to the end point with 2 ml of 1.4M sec-butyllithium (BuLi ic), and heated to 45° C. before adding 46.38 ml of a 1.4 M sec-butyllithium solution for initiation, and 5.61 ml of a 0.553 M potassium tert-amyl alcoholate (PTA) solution, as randomizer. Next, the initiator mixture was then admixed. In a next step, 1350 gram styrene (51) was added and the polymerization reaction was allowed to run to complete monomer consumption (identified by a decrease in temperature of the reaction mixture). In a next step, 570 gram butadiene (B1) and 415 gram styrene (S2) were added simultaneously and the polymerization reaction was allowed to run to complete monomer consumption (identified by a decrease in temperature of the reaction mixture).

[0132] In a next step, again 800 gram butadiene (B2) and 720 gram styrene (S3) were added simultaneously and the polymerization reaction was allowed to run to complete monomer consumption (identified by a decrease in temperature of the reaction mixture). In a next step, again 535 gram butadiene (B3) and 310 gram styrene (S4) were added simultaneously and the polymerization reaction was allowed to run to complete monomer consumption (identified by a decrease in temperature of the reaction mixture). In a next step, 300 gram styrene (S5) was added and the polymerization reaction was allowed to run to complete monomer consumption (identified by a decrease in temperature of the reaction mixture).

[0133] Finally, 7.21 mL of Edenol® D82 dissolved in 30 mL cyclohexane was added as coupling agent and allowed to react for 10 minutes. Finally, the reaction was terminated using 0.5 ml of isopropanol and acidified with a CO.sub.2 gas stream at 0.1 kg/h for 5 min and 10 mL water and a stabilizer solution (0.135 wt.-% phm* Sumilizer GS, 0.135 wt.-% phm Irganox® 1010 and 0.18 wt.-% Irgaphos 168) was added. *phm=‘per hundred parts by weight of monomer’ (wt.-% of component (initiator, coupling agent etc.) is calculated on the total mass of the monomers)

TABLE-US-00001 TABLE 1 Block copolymer A (composition and sequence of addition) 1st 2nd block 3rd block 4th block 5.sup.th block block S.sub.1 (S/B).sub.k (S/B).sub.I (S/B).sub.m S.sub.2 S1 B1 S2 B2 S3 B3 S4 S5 SBC wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% A 27.0 11.4 8.3 16.0 14.4 10.7 6.2 6.0

Preparation of the Thermoplastic Elastomer Composition

[0134] 4 to 9 phm of mineral oil (cp. Table 2) as a plasticizer B were each added to 100 parts by weight (pbw) of the total weight of monomers used to synthesize block-copolymer A as hereinbefore described. For this purpose the plasticizer B was added to the polymer solution of block copolymer A in cyclohexane after polymerization and stabilization and before degassing, followed by 30 min of decent mixing with a propeller mixer in a vessel.

[0135] Tensile bars according to ISO 527 (1A) were produced from the obtained thermoplastic elastomer compositions for mechanical evaluation (ISO 527, cp. Table 2).

[0136] The hysteresis is measured on a tensile bar according to ISO 527 (1A). The procedure to measure hysteresis is: Stretch at 50 mm/min to 100% strain, maintain for 1 sec under constant elongation, return at 50 mm/min to zero stress, stretch at 50 mm/min to 200% strain, maintain for 1 sec under constant elongation, return at 50 mm/min to zero stress, stretch at 50 mm/min to 300% strain, maintain for 1 sec under constant elongation, return at 50 mm/min to zero stress. At this point, the elongation at zero stress is measured.

[0137] Transparency, haze and clarity were measured on a BYK Haze-gard I according to ASTM D1003 on 2mm compression molded plates which were produced at 200° C. under 40 bar during 10 min.

TABLE-US-00002 TABLE 2 Amount plasticizer B (phm) on top of 100 pbw** block copolymer A 4 phm 5 phm 6 phm 7 phm 8 phm 9 phm M.sub.W before coupling g/mol 96486 97060 98054 93142 92539 96810 M.sub.W after coupling g/mol 258040 264570 261010 251770 246800 250750 MFI.sub.(200/5) cm.sup.3/10 min 5.88 6.47 6.22 10.07 11.17 9.42 Shore A 77.4 76.5 74.5 73.5 73.1 72.2 Stress at break MPa 9.73 10.1 10.1 10.5 11.1 10.9 Strain at break % 460 470 470 510 520 529 E Modulus MPa 33.0 27.3 28.8 23.2 25.9 24.5 Hysteresis 300% % 58.9 71.5 62.0 53.4 57.9 60.2 Transparency % 90.9 91.2 91.2 90.3 90.8 90.8 Haze % 8.7 5 6.7 8.9 10 10.8 Clarity % 83.8 86.2 84.9 81.3 81.6 80.6 **pbw = parts by weight

[0138] The obtained S-TPE compositions according to the invention have an improved recovery from bending which can be shown e.g. by their low hysteresis (residual strain of less than 75% at zero stress after elongation of 300% strain (cp. examples, Table 2) and the packaging test described below.

[0139] Tubes of 140 cm length produced from S-TPE compositions with 9 phm of plasticizer B were folded into length of 20 cm and stored bundled together for 1, 3 and 7 days at 20° C. The tubes were then unfolded, stretched to 150 cm for 1 second, and hung up vertically on the wall so that they could drop gravimetrically. After 30 minutes the vertically described length of each tube was measured.

[0140] The value is a measure of the recovery of the creases. The greater the value the better the recovery to the original linear shape without creases.

[0141] After hanging for 3 days, S-TPE compositions according to the invention with 9 phm of plasticizer B had a vertically described length of 127 cm whereas commercial PVC tubes taken from an intravenous set with the same outer and inner diameter had a described vertical length of 124 cm. This means that the ‘bends’ in the material according to the invention recover much better after unwrapping.

[0142] Furthermore, the tensile strength of the S-TPE compositions according to the invention is high as shown by a stress at break higher than 9 MPa, measured on a tensile bar according to ISO 527 (1A).

[0143] Moreover, the obtained compositions are soft, having a shore A hardness in the range of from 72.4 to 77.4.

[0144] The data as shown in Table 2 prove that the compositions according to the invention have a high transparency. Moreover, the MFI values of the inventive samples obtained are such as to allow good processing, even when increasing amounts (cp. 40, 45 phm) of plasticizer are added.