IMPACT MODIFIED STYRENE COPOLYMER COMPOSITION COMPRISING POLYSILOXANE ADDITIVE HAVING IMPROVED ABRASION CHARACTERISTICS

Abstract

Thermoplastic polymer compositions (P) comprising at least one styrene-based polymer composition (A) comprising at least one graft copolymer (A-1), at least one organopolysiloxane compound, and optionally at least one colorant, dye or pigment, and/or at least one further additive show improved properties with respect to residual gloss after abrasion combined with improved melt flow characteristics while heat resistance is not affected.

Claims

1-15. (canceled)

16. A thermoplastic polymer composition (P) comprising: (A) up to 99.75 wt.-% of at least one styrene-based polymer composition (A) comprising at least one graft copolymer (A-1); (B) 0.25 to 5 wt.-% of at least one organopolysiloxane compound; (C) 0 to 10 wt.-% of at least one colorant, dye or pigment; and (D) 0 to 3 wt.-% of at least one further additive, wherein the constituents (A) to (D) sum up to 100 wt.-% of the thermoplastic polymer composition (P); and wherein the styrene-based polymer composition (A) comprises 20 to 60 wt.-% of at least one styrene-based graft copolymer (A-1) and 40 to 80 wt.-% of at least one thermoplastic polymer (A-2) selected from poly(styrene-acrylonitrile) (SAN), poly(-methyl styrene-acrylonitrile) (AMSAN), and mixtures thereof; the at least one organopolysiloxane compound (B) has a weight average molecular weight Mw of 20,000 g/mol to 100,000 g/mol, determined by gel permeation chromatography (GPC) relative to polystyrene as standard and THF as solvent; wherein the at least one organopolysiloxane compound (B) is a block copolymer comprising blocks of polysiloxane moieties comprising repeating units having the following formula (Ia): ##STR00006## wherein each R.sup.1 is independently selected from a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and blocks of polyester and/or polyolefin moieties; and the at least one graft copolymer (A-1) is selected from a poly(acrylonitrile-butadiene-styrene) (ABS) having an average particle size D.sub.50 of the rubber particles in the ABS copolymer from 50 to 750 nm, a poly(acrylonitrile-styrene-acrylic ester) (ASA) having an average particle size D50 of the rubber particles in the ASA copolymer from 50 to 1000 nm, and mixtures thereof, wherein the average particle size is determined using an ultracentrifuge.

17. A thermoplastic polymer composition (P) according to claim 16, wherein the styrene-based polymer composition (A) comprises 30 to 40 wt.-% of at least one styrene-based graft copolymer (A-1) and 60 to 70 wt.-% of at least one thermoplastic polymer (A-2) selected from poly(styrene-acrylonitrile) (SAN), poly(-methyl styrene-acrylonitrile) (AMSAN), and mixtures thereof; and the at least one organopolysiloxane compound (B) is a block copolymer comprising blocks of polysiloxane moieties comprising repeating units having the following formula (Ia): ##STR00007## wherein each R.sup.1 is independently selected from a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, and blocks of polyester and/or polyolefin moieties.

18. The thermoplastic polymer composition (P) according to claim 16, wherein the at least one organopolysiloxane compound (B) is a block copolymer having a tri-block structure or a brush structure.

19. The thermoplastic polymer composition (P) according to claim 16, wherein the surface of the thermoplastic polymer composition (P) has a residual gloss of more than 25% after abrasion was effected according to norm PV3975 compared to the surface of the non-abraded thermoplastic polymer composition (P).

20. The thermoplastic polymer composition (P) according to claim 16, wherein the surface of the thermoplastic polymer composition (P) has a relative gloss change of less than 45% after abrasion was effected according to norm PV3987 compared to the surface of the non-abraded thermoplastic polymer composition (P).

21. The thermoplastic polymer composition (P) according to claim 16, wherein the melt volume-flow rate (MVR, 220 ml/10 min according to ISO 1133) of the thermoplastic polymer composition (P) is increased by a factor of at least 1.15 compared to the melt volume-flow rate of a thermoplastic polymer composition which does not comprise the at least one organopolysiloxane compound (B).

22. The thermoplastic polymer composition (P) according to claim 16, wherein the Vicat softening temperature (VST B50, according to DIN EN ISO 306) of the thermoplastic polymer composition (P) is reduced by less than 5 C. compared to the Vicat softening temperature of a thermoplastic polymer composition which does not comprise the at least one organopolysiloxane compound (B).

23. The thermoplastic polymer composition (P) according to claim 16, wherein the Charpy notched impact strength of the thermoplastic polymer composition (P) is reduced by less than 4 kJ/m.sup.2, compared to the Charpy notched impact strength of a thermoplastic polymer composition which does not comprise the at least one organopolysiloxane compound (B).

24. A process for preparing the thermoplastic polymer composition (P) according to claim 16, wherein the process comprises at least the following steps: a) providing the components (A) to (D) in the predetermined amounts to an optionally heatable mixing device; and b) blending the components (A) to (D) in the optionally heatable mixing device at temperatures above the glass transition point of the components (A) to (D) to obtain the thermoplastic polymer composition (P).

25. A molded article, prepared from the thermoplastic polymer composition (P) according to claim 16.

26. A method of making components or articles for electronic devices, household goods, and automotive parts, comprising the thermoplastic polymer composition (P) according to claim 16.

27. A method of making components or articles for electronic devices, household goods, and automotive parts, comprising the molded article according to claim 25.

Description

EXAMPLES

Materials

Constituents A, C and D

[0174] The styrene-based polymer constituent (A) was provided in form of a blend comprising the following polymer composition A*: [0175] 26.6 wt.-% AMSAN having an acrylonitrile content of 30 wt.-%; [0176] 37.3 wt.-% SAN having an acrylonitrile content of 35 wt.-%; [0177] 21.75 wt.-% ASA graft rubber having a mean particle diameter D.sub.50 of about 90 nm; and [0178] 14.35 wt.-% ASA graft rubber having a mean particle diameter D.sub.50 of about 550 nm.

[0179] The constituent (A) consisted to 88.85 wt.-% of the above described polymer composition A* and further comprised 9.70 wt.-% of a colorant constituent (C) in form of a colorant master batch comprising 20 wt.-% carbon black in a SAN copolymer matrix. Furthermore, 1.45 wt.-% of additive constituents (D) were present in constituent (A) in form of lubricants (polyethylene wax), plasticizers (DPHP IBC), light stabilizers (Tinuvin 770) and further stabilizers (Cyasorb 3853). Constituent (A) is commercial available from INEOS Styrolution Group GmbH, Germany).

Constituent B

[0180] The polysiloxane constituent (B) was provided in form of a liquid component having a viscosity (25 C.) of 950 to 2000 mPas. It is commercially available from Evonik Nutrition & Care GmbH (Tegomer Antiscratch L). The molecular weight (weight average, Mw) was determined with GPC (solvent: THF) to be 39311 g/mol (relative to a polystyrene standard).

Sample Preparation

[0181] The sample according to Example 1 was prepared by compounding constituents A and B using a twin screw extruder (model ZSK26MC, Coperion GmbH, length: 1035 mm) at T.sub.m=240 C. according to the specific ratios given in Table 1 below. DIN A5 size samples have been prepared via injection molding (T.sub.m: 242 C.).

[0182] Comparative Example 1 was prepared by producing DIN A5 size samples of the constituent A prior to the addition of with constituent B via injection molding (T.sub.m: 242 C.).

[0183] Comparative Example 2 was prepared by producing DIN A5 size samples of poly(methyl methacrylate) (Plexiglas 8N black, available from Evonik Performance Materials GmbH, Germany) via injection molding (T.sub.m: 242 C.).

[0184] The composition of the samples according to Example 1 to 3 and Comparative Example 1 are given in Table 1.

TABLE-US-00001 TABLE 1 Ex. 1 Comp. Ex. 1 Comp. Ex. 2 Constituent (wt.-%) (wt.-%) (wt.-%) Constituent A 98.0 100 Constituent B 2 Plexiglas 8N 100

Testing Methods

[0185] The properties of the thermoplastic polymer compositions (P) were evaluated by the following testing methods. The same methods were applied to determine the properties of the constituents (A) to (D), where necessary.

Residual Gloss

[0186] Abrasion was effected according to PV3975. A Martindale abrasion tester was used with 281Q WOD abrasive paper (9 mic, 215.9 mm*279 mm, 3M). All samples have been conditioned at 18-28 C./50% relative humidity for 7 days.

[0187] The number of cycles during testing was 10 with a load of 12 kPa. After abrasion, gloss was measured at 20 using a Multigloss 268 (Konica Minolta). Gloss retention (residual gloss) is calculated as follows:

[00001]$\mathrm{residual}.Math..Math.\mathrm{gloss}=\frac{\mathrm{gloss}.Math..Math.\mathrm{after}.Math..Math.\mathrm{testing}}{\mathrm{initial}.Math..Math.\mathrm{gloss}}$

Relative Gloss Change

[0188] Abrasion was effected according to PV3987. An Erichsen Lineartester 249 was used with Rub Head Type C and 261 (5 pm) abrasive paper from 3M. Prior to measurement, samples have been pre-conditioned at 18 to 27 C. and 50% r.h. for 7 days. Using a normal load of 9 N, 5 test cycles have been applied to the sample (linear scratch path). Gloss was measured using a Multigloss 268 (Konica Minolta). Relative gloss change is calculated as follows:

[00002]$\mathrm{relative}.Math..Math.\mathrm{gloss}.Math..Math.\mathrm{change}=\frac{\mathrm{initial}.Math..Math.\mathrm{gloss}-\mathrm{gloss}.Math..Math.\mathrm{after}.Math..Math.\mathrm{testing}}{\mathrm{initial}.Math..Math.\mathrm{gloss}}$

[0189] Melt volume-flow rate (MVR 220 C./10 kg) was measured according to ISO 1133.

[0190] Charpy notched impact strength was measured according to DIN EN ISO 179-1/1eA.

[0191] Heat resistance (VST B50) was measured according to DIN EN ISO 306.

[0192] The mean particle diameter D.sub.50 may be determined by ultracentrifuge measurements (see W. Scholtan, H. Lange: Kolloid Z. & Z. Polymere 250, p. 782 to 796 (1972)).

[0193] The weight average molecular weight Mw was determined by gel permeation chromatography using UV-detection. Polystyrene was used as standard. Typically, tetrahydrofuran was used as solvent. The test results are summarized in Table 2.

TABLE-US-00002 TABLE 2 Charpy Relative MVR notched Vicat soften- Residual gloss 220/10 impact ing point gloss change [ml/10 strength (VST B50) Example [%] [%] min] [kJ/m.sup.2] [ C.] Ex. 1 18.2 32.9 6.09 13.01 101 Comp. 6.8 78.7 4.73 12.97 102 Ex. 1 Comp. 19 30.9 Ex. 2

[0194] The experimental data summarized in Table 2 show that the thermoplastic polymer composition (P) according to the present invention comprising only small amounts of the at least one organopolysiloxane compound (B) as defined herein is characterized by having dramatically improved properties with respect to residual gloss (determined according to PV3975) compared to the respective styrene-based polymer composition without the addition of the organopolysiloxane compound (B) (cf. Ex. 1 and Comp. Ex. 1). In the absence of the organopolysiloxane compound (B), the styrene-based polymer composition shows only gloss retention of 6.8% after testing according to PV3975 (cf. Comp. Ex. 1).

[0195] By contrast, the addition of only 2 wt.-% of organopolysiloxane results in a residual gloss after testing according to PV3975 of 18.2%. This value is similar to the value achieved by PMMA materials, which are, however, more difficult to prepare and more expensive (cf. Comp. Ex. 2).

[0196] Furthermore, as can be seen from the experimental data in Table 2, Ex. 1 shows a low relative gloss change after testing according to PV3987, similar to the PMMA sample (Comp. Ex. 2) usually having high scratch resistance. On the contrary, without the addition of the organopolysiloxane compound (B), the styrene-based polymer composition shows very high relative gloss change of 78.7% after testing (cf. Comp. Ex. 1).

[0197] Furthermore, it is demonstrated by Ex. 1, that the addition of the organopolysiloxane compound (B) is able to improve the melt flow characteristic (MVR) compared the base material (Comp. Ex. 1), while impact strength (Charpy notched impact strength) and heat resistance (Vicat Softening Point) are not adversely affected.

[0198] The thus obtained improved characteristics of the thermoplastic polymer composition (P) according to the present invention turn the copolymer composition to a convenient and inexpensive alternative to poly(methyl-methacrylate) compositions and/or UV-cured surfaces in applications such as housings of household goods and electronic devices as well as interior parts in the automotive industry.