Scratch-resistant styrene copolymer composition containing modified organopolysiloxane compounds

Abstract

A scratch-resistant thermoplastic polymer composition (P) comprising 88 to 99.9 wt.-% of at least one styrene-based copolymer, 0.1 to 5 wt.-% of at least one modified organopolysiloxane compound, and optionally at least one colorant, dye or pigment, and/or at least one further additive, provides with improved properties.

Claims

1. A thermoplastic polymer composition (P) comprising: (A) 88 to 99.9 wt.-% of at least one styrene-based copolymer, wherein the at least one styrene-based copolymer is selected from poly(a-methylstyrene-co-acrylonitrile) (AMSAN), poly(styrene-co-methyl methacrylate) (SMMA), and mixtures thereof; (B) 0.1 to 5 wt.-% of at least one modified 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), wherein the at least one modified organopolysiloxane compound is a polyester-polysiloxane-block copolymer.

2. The thermoplastic polymer composition (P) according to claim 1, wherein the thermoplastic polymer composition (P) comprises as constituent (A) 93 to 99.9 wt.-% of at least one styrene-based copolymer, wherein the at least one styrene-based copolymer is selected from poly(α-methylstyrene-co-acrylonitrile) (AMSAN), poly(styrene-co-methyl methacrylate) (SMMA), and mixtures thereof.

3. The thermoplastic polymer composition (P) according to claim 1, wherein the thermoplastic polymer composition (P) comprises as constituent (B) 0.1 to 4 wt.-% of at least one modified organopolysiloxane compound.

4. The thermoplastic polymer composition (P) according to claim 1, wherein the thermoplastic polymer composition (P) comprises as constituent (C) 0.1 to 6.9 wt.-% of at least one colorant, dye, or pigment.

5. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one modified organopolysiloxane compound has a weight average molecular weight Mw of 20,000 g/mol to 1,000,000 g/mol, determined by gel permeation chromatography (GPC) relative to polystyrene as standard.

6. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one modified organopolysiloxane compound is a [polyester-b-polysiloxane-b-polyester] triblock copolymer or a [polysiloxane-b-polyester] brush copolymer.

7. The thermoplastic polymer composition (P) according to claim 6, wherein the at least one modified organopolysiloxane compound is a [polyester-b-polysiloxane-b-polyester] triblock copolymer represented by the following formula (III): ##STR00005## wherein each R.sup.1 is independently selected from a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms; R.sup.2 is independently selected from a hydrogen atom and a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms; R.sup.3 is selected from a hydrogen atom and a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms; m is an integer from 1 to 10; and k and n are integers from 1 to 500.

8. The thermoplastic polymer composition (P) according to claim 6, wherein the at least one modified organopolysiloxane compound is a [polysiloxane-b-polyester] brush copolymer comprising polysiloxane moieties derived from repeating units having the following formula (Ia) and from repeating units having the following formula (Ib): ##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; R.sup.4 represents a polyester moiety of the polyester modified organopolysiloxane compound (B) is derived from repeating units having the following formula (II): ##STR00007## wherein R.sup.2 is independently selected from a hydrogen atom and a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms; and m is an integer from 1 to 10, wherein each chain and side chain of the polymer is terminated by a hydrogen atom or a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms; and wherein the repeating units of formula (Ib) are statistically distributed within the polysiloxane moieties and amount to 1 to 50 wt.-%, based on the entire weight of the polysiloxane moieties.

9. The thermoplastic polymer composition (P) according to claim 1, wherein an article prepared from the thermoplastic polymer composition (P) requires a minimum normal load of at least 300 g in a scratch resistance test following ISO 1518-1 to achieve a full scratch mark on the surface of the article.

10. The thermoplastic polymer composition (P) according to claim 1, wherein the surface of the thermoplastic polymer composition (P) has a residual gloss of more than 15% after abrasion was effected according to norm PV3975 compared to the surface of the non-abraded thermoplastic polymer composition (P).

11. The thermoplastic polymer composition (P) according to claim 1, 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 1.2 compared to the melt volume-flow rate of a thermoplastic polymer composition which does not comprise the at least one modified organopolysiloxane compound (B).

12. The thermoplastic polymer composition (P) according to claim 1, 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 modified organopolysiloxane compound (B).

13. A process for the preparation of the thermoplastic polymer composition (P) according to claim 1, 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 temperature of the components (A) to (D) to obtain the thermoplastic polymer composition (P).

14. A molded article, prepared from the thermoplastic polymer composition (P) according to claim 1.

15. The molded article according to claim 14, wherein the molded article is a component of or article for electronic devices, household goods, and automotive parts.

16. The molded article according to claim 14, where the molded article is a component of or article for A/B/C pillars of automobiles.

Description

EXAMPLES

(1) Materials

(2) Constituent A: A-1 AMSAN copolymer with an acrylonitrile content of 30 wt.-%, having a viscosity number VN of 57 ml/g and a Vicat softening temperature (VST B50) of 120° C. (commercially available as Luran® HH-120 from INEOS Styrolution, Germany). A-2 SMMA copolymer having a melt volume-flow rate (MVR 220/10) of 30 ml/10 min, and Vicat softening temperature (VST B50) of 98° C. (commercially available as NAS® 30 from INEOS Styrolution, Germany). A-3 PMMA having a melt volume-flow rate (MVR 230° C./3.8 kg) of 6 ml/10 min, a Vicat softening temperature (VST B50) of 103° C., a refractive index of 1.49, a density of 1.19 g/ml (commercially available as Plexiglas® 7N from Evonik Industries AG, Germany).

(3) Constituent B: B-1: A polyester modified polysiloxane having a melting point of approximately 54° C. and a water content of <0.1% was used (commercially available as Tegomer® H-Si 6441P from Evonik Industries GmbH, Essen, Germany).

(4) Constituent C C-1: Carbon Black 08 (20 wt.-% in a SAN copolymer based on the total weight of C-1). C-2: Colorant composition comprising 21.6 wt.-% Pyrazolone Yellow, 62.4 wt.-% Allizarin Blue, 8 wt.-% Alizarin Violet and 8 wt.-% Carbon Black, based on the total weight of C-2. C-3 Carbon Black 08

(5) Constituent D D-1 Additive composition comprising 26.23 wt.-% UV Stabilizer Tinuvin 770, 15.48 UV Stabilizer Chimasorb 944, 31.69 wt.-% UV Stabilizer Cyasorb 3853 (50 wt.-% in polypropylene), and 26.23 wt.-% stearyl alcohol bag, based on the total weight of D-1.

(6) Sample Preparation of Polymer Composition

(7) Example 1 was prepared by compounding the constituents A and B in the amounts given in Table 1 using a Coperion® ZSK25 twin-screw extruder (Tm: 215 to 235° C., die temperature: 240° C.). Sample plaques (size: 200*140*4 mm) have been prepared via injection molding at 240° C.

(8) Comparative Example 1 was prepared by compounding the constituents A and C in the amounts given in Table 1 using a Coperion® ZSK25 twin-screw extruder (Tm 210° C.). Sample plaques (size: 200*140*4 mm) have been prepared via injection molding at 240° C.

(9) Example 2 was prepared by compounding the constituents A and B in the amounts given in Table 1 using a Coperion® ZSK25 twin-screw extruder (Tm: 215 to 235° C., die temperature: 240° C.). Sample plaques (size: 200*140*4 mm) have been prepared via injection molding at 240° C.

(10) Comparative Example 2 has been prepared from constituent A-2. Sample plaques (size: 200*140*4 mm) were prepared via injection molding at 240° C.

(11) Example 3 and Comparative Example 3 were prepared by compounding the constituents A to D in the amounts given in Table 1 using a Coperion® ZSK26MC twin-screw extruder (length: 1035 mm, Tm=240° C.). Sample plaques (size: Din A5) have been prepared via injection molding at 242° C.

(12) Comparative Example 4 was prepared from constituents A-3 and C-3 in amounts of Table 1 using a Coperion ZSK-25 twin screw extruder. Sample plagues (200*140*4 mm) were prepared via injection molding under the following injection molding conditions: pre-drying (2-3 h, max. 93° C.), mass temperature Tm 220 to 260° C., mold temperature 60° C. to 90° C.

(13) Comparative Example 5 was prepared from constituent A-3 via injection molding of A5 plaques (Tm 242° C., max injection pressure 580 bar).

(14) TABLE-US-00001 TABLE 1 Amount Amount Amount Const. A Const. B Const. C Const. D Ex. No. Const. A [wt.-%] Const. B [wt.-%] Const. C [wt.-%] Const. D [wt.-%] Ex. 1 A-1 99.75 B-1 0.25 — — — — Comp. Ex. 1 A-1 97.45 — — C-1 2.55 — — Ex. 2 A-2 99 B-1 1   — — — — Comp. Ex. 2 A-2 100 — — — — — — Ex. 3 A-1 95.47 B-1 1.5  C-2 1.23 D-1 1.80 Comp. Ex. 3 A-1 96.92 — — C-2 1.25 D-1 1.83 Comp. Ex. 4 A-3 99.5 — — C-3 0.5  — — Comp. Ex. 5 A-3 100 — — — — — —

(15) Testing Methods

(16) 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.

(17) Scratch Resistance

(18) Scratch resistance was tested using an Erichsen Linear Tester (Model 249) equipped with an indenter according to ISO 1518-1 (hard metal coating). Prior to testing all samples have been conditioned at 23° C./50% r.h. for 48 h. The indenter was moved with a speed of 100 mm/s over the surface of the sample (35 or 55 mm scratch path length). The normal load (force of the indenter) is adjusted by using a balance in the following steps 50 g, 100 g, 150 g, 200 g, 300 g, 400 g, 500 g, 600 g, 700 g, 800 g, 900 g, 1000 g for performing scratches beside the previous tested loads. After scratching the surface is evaluated in direct visual examination in reflection of diffuse daylight and/or fluorescent tube light in a geometry of 0° to 85° to the perpendicular line of the surface. The minimum loads (in g) to first achieve a scratch mark on the surface are recorded. A full scratch is identified by color changes, reflections by the formed hollows or surface roughness in parts of the scratch area respectively shown in the complete scratched area. Additionally the scratch appearance as well as the minimum loads are compared to the base material.

(19) Residual Gloss

(20) 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. 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 according to the following formula:

(21) $\mathrm{residual}\mathrm{gloss}=\frac{\mathrm{gloss}\mathrm{after}\mathrm{testing}}{\mathrm{initial}\mathrm{gloss}}$

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

(23) Viscosity number was measured according to DIN 53727 at 25° C. as 0.5 wt.-% solution in dimethylformamide (DMF).

(24) Refractive Index was measured according to ASTM D 542 (sodium line).

(25) Density was measured according to DIN EN ISO 1183.

(26) Vicat softening temperature (VST B50) was measured according to DIN EN ISO 306.

(27) 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.

(28) The test results are summarized in Tables 2 and 3.

(29) TABLE-US-00002 TABLE 2 Ex. No. min. load for full scratch [g] Ex. 1 600 Comp. Ex. 1 50 Ex. 2 600 Comp. Ex. 2 150 Comp. Ex. 4 600

(30) The examples clearly show that the addition of the polyester modified polysiloxane according to the present invention to different styrene-based copolymers has significant effects on the improvement of scratch resistance determined using test plaques prepared from the inventive thermoplastic polymer composition (P) with an Erichsen Linear Tester 249 compared to the pure base resin. Comp. Ex. 1 and 2 show a full scratch already at very low normal loads of 50 to 150 g. On the other hand Comp. Ex. 4, prepared from PMMA instead of styrene-based copolymer, represents a comparative compound which is typically used as a polymer with excellent scratch resistance. Full scratch is observed only at 600 g. However, PMMA is more expensive than the styrene-based copolymers.

(31) It was surprisingly found that by adding 0.1 to 5 wt.-% of the polyester modified polysiloxane to the styrene-based copolymer the normal load necessary to achieve a full scratch on the surface of the test sample can be significantly increased.

(32) Example 1 shows that the addition of small amounts of a polyester modified polysiloxane results in an increase of scratch resistance of an AMSAN copolymer composition compared to the respective pure AMSAN copolymer (Comp. Ex. 1) by a factor of 12. The normal load to achieve full scratch is increased from 50 g (Comp. Ex. 1) to 600 g (Ex. 1).

(33) Similar results are observed for the addition of small amounts of a polyester modified polysiloxane to an SMMA copolymer composition (Ex. 2). Compared to the respective pure AMSAN copolymer (Comp. Ex. 1) an increase of scratch resistance by a factor of 4 is observed. The normal load to achieve full scratch is increased from 150 g (Comp. Ex. 2) to 600 g (Ex. 2).

(34) TABLE-US-00003 TABLE 3 Vicat softening MVR temperature Residual 220/10 (VST B50) No. gloss [%] [ml/10 min] [° C.] Ex. 3 22.3 17.6 114.3 Comp. Ex. 3 16.5 11.5 114.3 Comp. Ex. 5 35.9 — —

(35) As can be seen from Table 3, it was surprisingly found that the addition of the polyester modified polysiloxane also results in an increased melt volume-flow rate, while Vicat softening temperature remains unaltered.

(36) In particular, the comparison of Ex. 3 and Comp. Ex. 3 shows an increase in melt volume-flow rate, which is a very important property for the injection molding process, by a factor of 1.5. The Vicat softening temperature, which is very important for final application, remains unchanged.

(37) Moreover, it was found that the residual gloss of the surface of the test specimen is considerably higher after abrasion, if the thermoplastic polymer composition (P) according to the invention is used. The residual gloss is increased from 16.5% for the pure base resin (Comp. Ex. 3) to 22.3% for the inventive thermoplastic polymer composition (Ex. 3). Comp. Ex. 5 gives the respective value of a PMMA sample.

(38) The obtained improved characteristics of the thermoplastic polymer composition (P) according to the present invention turn the 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.