Scratch-resistant styrene copolymer composition containing inorganic metal compound nanoparticles

Abstract

A scratch-resistant thermoplastic polymer composition (P) comprising 40 to 99.9 wt.-% of at least one styrene-based copolymer, 0.1 to 20 wt.-% of at least one inorganic metal compound nanoparticle, and optionally at least one polymeric compatibilizing agent, at least one modified polysiloxane compound, at least one colorant, dye or pigment, and/or at least one further additive has improved scratch properties.

Claims

1. A thermoplastic polymer composition (P) comprising: (A) 40 to 98.9 wt.-% of at least one styrene-based copolymer; (B) 0.1 to 10 wt.-% of at least one inorganic metal compound nanoparticle; (C) 1 to 35 wt.-% of at least one polymeric compatibilizing agent; (D) 0 to 2 wt.-% of at least one modified polysiloxane compound; (E) 0 to 10 wt.-% of at least one colorant, dye, or pigment; and (F) 0 to 3 wt.-% of at least one further additive, wherein the constituents (A) to (F) sum up to 100 wt.-% of the thermoplastic polymer composition (P).sub.1 and wherein the at least one styrene-based copolymer (A) is selected from poly(styrene-co-acrylonitrile) (SAN), poly(α-methyl styrene-co-acrylonitrile) (AMSAN), poly(styrene-co-methyl methacrylate) (SMMA), and mixtures thereof.

2. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one inorganic metal compound nanoparticle (B) is selected from ZnO, SnO.sub.2, ZrO.sub.2, WC, SiC, and Al.sub.2O.sub.3 nanoparticles.

3. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one inorganic metal compound nanoparticle (B) is selected from ZnO, SnO.sub.2, and ZrO.sub.2 nanoparticles having an average particle diameter of between 10 and 120 nm.

4. The thermoplastic polymer composition (P) according to claim 1 comprising: (A) 42 to 98.5 wt.-% of at least one styrene-based copolymer; (B) 0.5 to 8 wt.-% of at least one inorganic metal compound nanoparticle; (C) 1 to 35 wt.-% of at least one polymeric compatibilizing agent; (D) 0 to 2 wt.-% of at least one modified polysiloxane compound; (E) 0 to 10 wt.-% of at least one colorant, dye, or pigment; and (F) 0 to 3 wt.-% of at least one further additive, wherein the constituents (A) to (F) sum up to 100 wt.-% of the thermoplastic polymer composition (P).

5. A thermoplastic polymer composition (P) comprising: (A) 40 to 99.8 wt.-% of at least one styrene-based copolymer; (B) 0.1 to 10 wt.-% of at least one inorganic metal compound nanoparticle; (C) 0 to 35 wt.-% of at least one polymeric compatibilizing agent; (D) 0.1 to 2 wt.-% of at least one modified polysiloxane compound; (E) 0 to 10 wt.-% of at least one colorant, dye, or pigment; and (F) 0 to 3 wt.-% of at least one further additive, wherein the constituents (A) to (F) sum up to 100 wt.-% of the thermoplastic polymer composition (P); and wherein the at least one styrene-based copolymer (A) is selected from poly(styrene-co-acrylonitrile) (SAN), poly(α-methyl styrene-co-acrylonitrile) (AMSAN), poly(styrene-co-methyl methacrylate) (SMMA), and mixtures thereof.

6. The thermoplastic polymer composition (P) according to claim 1 comprising: (A) 42 to 88.5 wt.-% of at least one styrene-based copolymer; (B) 1 to 8 wt.-% of at least one inorganic metal compound nanoparticle; (C) 10 to 35 wt.-% of at least one polymeric compatibilizing agent; (D) 0.5 to 2 wt.-% of at least one modified polysiloxane compound; (E) 0 to 10 wt.-% of at least one colorant, dye, or pigment; and (F) 0 to 3 wt.-% of at least one further additive, wherein the constituents (A) to (F) sum up to 100 wt.-% of the thermoplastic polymer composition (P).

7. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one modified polysiloxane compound (D) is a polyester modified polysiloxane.

8. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one modified polysiloxane compound (D) is a polyester modified polysiloxane having a melting point between 40° C. and 70° C.

9. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one modified polysiloxane compound (D) is a polyester-polysiloxane-block copolymer.

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

11. The thermoplastic polymer composition (P) according to claim 1, wherein the at least one polymeric compatibilizing agent (C) is a copolymer obtained by copolymerizing a monomer mixture comprising styrene, acrylonitrile, and maleic acid anhydride and/or maleic acid.

12. 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.

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 (F) in the predetermined amounts to an optionally heatable mixing device; and b) blending the components (A) to (F) in the optionally heatable mixing device at temperatures above the glass transition point of the components (A) to (F) to obtain the thermoplastic polymer composition (P).

Description

EXAMPLES

(1) Materials

(2) Constituent A: A-1: A SAN copolymer comprising 75 wt.-% styrene and 25 wt.-% acrylonitrile. The SAN copolymer has a viscosity number of 80 cm.sup.3/g, (DIN 53726, 25° C., 0.5% in DMF) A*: As a comparative material, a commercial poly(methyl methacrylate) (PMMA) having a MVR (230/3.8) of about 6 cm.sup.3/10 min was used (Plexiglas® 7N, available from Evonik Performance Materials GmbH, Germany) Constituent B:

(3) Four different inorganic metal compound nanoparticles (B) were employed:

(4) B-1: ZnO nanoparticles having an average particle size of 5 nm were prepared according to the following preparation method: a) Zinc oleate synthesis: 200 g (2 eq.) sodium oleate is dissolved in 1 l pre-warmed water. 55 g (1 eq.) zinc chloride are dissolved in a separate vessel in 0.5 l water and added to the zinc oleate solution. Solid zinc oleate is filtered off after 1 to 2 hours of stirring. The solid is dried. The product is obtained in quantitative yield. b) ZnO nanoparticle synthesis: (B-1) Tetrahydrofuran (THF) is heated to 60° C. (1 l THF per 100 g zinc oleate) followed by addition of zinc oleate, equimolar amount of KOH (1 M in methanol) is added and solution is stirred overnight, at room temperature, not reacted starting material and potassium oleate are separated by centrifugation, nanoparticles are precipitated with methanol and separated by centrifugation and redissolved in THF for further storage.

(5) The size distribution of the ZnO nanoparticles B-1 was determined by dynamic light scattering in THF as a solvent with a Malvern® Zetasizer® Nano SZ. B-2: ZnO nanoparticles, having an average particle size of 20 nm (purity: 99.5%, commercially available from loLiTec Ionic Liquids Technologies GmbH, Heilbronn, Germany) B-3: ZrO.sub.2 nanoparticles, having an average particle size of 100 nm (purity: 99.5%, commercially available from loLiTec Ionic Liquids Technologies GmbH, Heilbronn, Germany) B-4: SnO.sub.2 nanoparticles, having an average particle size of 20-30 nm (purity:

(6) 99.5%, commercially available from loLiTec Ionic Liquids Technologies GmbH, Heilbronn, Germany).

(7) Constituent C:

(8) Three different poly(styrene-acrylonitrile-maleic acid) terpolymers were prepared and used as polymeric compatibilizing agent C. The compatibilizers are obtained from monomer mixtures having the following compositions:

(9) TABLE-US-00001 Styrene Acrylonitrile Maleic acid anhydride C-1 75.0 wt.-% 23.5 wt.-% 1.5 wt.-% C-2 73.4 wt.-% 25.1 wt.-% 1.5 wt.-% C-3 73.4 wt.-% 25.1 wt.-% 1.5 wt.-%

(10) The precise preparation of each poly(styrene-acrylonitrile-maleic acid) terpolymer is described in the following:

(11) Preparation of Polymeric Compatibilizing Agent C-1:

(12) A reaction vessel is charged with 1938.8 g demineralized water, 170.4 g of 7.4 wt.-% Dresinate®-3 solution (rosin soap), 56.3 g of styrene and 17.6 g of acrylonitrile. The mixture is stirred at 200 rpm and heated to 80° C. After reaching 80° C., the initiator system is added to reaction mixture: 240 g demineralized water, 2.9 g potassium peroxodisulfate, 18 g sodium hydroxide, 18 g sodium bicarbonate. Monomer and emulsifier feed are started 0.5 h later. 1068.8 g styrene, 334.9 g acrylonitrile, 22.5 g maleic acid anhydride and 3.15 g tert-dodecylmercaptane (monomer feed) are added over a time period of 5 h. In parallel a 7.4 wt.-% Dresinate®-3 solution (341 g) (emulsifier feed) is also added over a time period of 5 h. After 3 h another initiator shot is added, consisting of 74.8 g demineralized water, 1.6 g potassium peroxodisulfate, 0.23 g sodium hydroxide, 0.23 g sodium bicarbonate. After 4.5 h 240 g demineralized water, 18 g sodium hydroxide and 18 g sodium bicarbonate are added. After 5.5 h 32.6 g demineralized water, 0.7 g potassium peroxodisulfate, 0.15 g sodium hydroxide, 0.15 g sodium bicarbonate are added to the reaction mixture. After the monomer and emulsifier feed is finished the reaction mixture is polymerized for another 4 h at 80° C. The resulting latex has a pH of 10.1 and a total solid content of 35.38 wt.-%. To obtain the polymer the latex is coagulated with magnesium sulfate solution and dried in a lab oven for two days at 70° C. The polymeric compatibilizing agent C-1 had a weight average molecular weight Mw of 260,000 g/mol.

(13) Preparation of Polymeric Compatibilizing Agent C-2:

(14) A reaction vessel is charged with 2200 g demineralized water, 227.4 g of 7.4 wt.-% Dresinate®-3 Solution, 43.8 g of styrene and 15 g of acrylonitrile. The mixture is stirred at 180 rpm and heated to 80° C. After reaching 80° C. the initiator system is added to reaction mixture: 185.4 g demineralized water, 6 g potassium peroxodisulfate, 0.4 g sodium hydroxide, 0.4 g sodium bicarbonate. After 30 min 1416.2 g styrene, 485 g acrylonitrile, 30 g maleic acid anhydride and 2.8 g tert-dodecylmercaptane are added over a time period of 300 min. In parallel 500 g of 7.4 wt.-% Dresinate®-3 solution, 1000 g demineralized water and 41.2 g potassium hydroxide are added over a time period of 300 min. After 180 min 99.8 g demineralized water, 4 g potassium peroxodisulfate, 0.2 g sodium hydroxide, 0.2 g sodium bicarbonate are added to the reaction mixture. After 330 min 43.6 g demineralized water, 1.6 g potassium peroxodisulfate, 0.1 g sodium hydroxide, 0.1 g sodium bicarbonate are added to the reaction mixture. Afterwards the reaction mixture is polymerized for another 240 min at 80° C. The resulting latex has a total solid content of 33.1 wt.-% and a pH of 8.58. The polymeric compatibilizing agent C-2 had a weight average molecular weight Mw of 280,000 g/mol.

(15) Preparation of Polymeric Compatibilizing Agent C-3:

(16) A reaction vessel is charged with 2000 g demineralized water, 227.4 g of 7.4 wt.-% Dresinate®-3 Solution, 43.8 g of styrene and 15 g of acrylonitrile. The mixture is stirred at 180 rpm and heated to 80° C. After reaching 80° C. the initiator system is added to reaction mixture: 185.4 g demineralized water, 6 g potassium peroxodisulfate, 0.4 g sodium hydroxide, 0.4 g sodium bicarbonate. After 30 min 1416.2 g styrene, 485 g acrylonitrile, 30 g maleic acid anhydride and 2.8 g tert-dodecylmercaptane are added over a time period of 300 min. In parallel 200 g demineralized water and 11 g Mersolat H95 (sodium salt of C12 to C18 sec-alkyl sulfonic acid) are added over a time period of 300 min. A third feed is also added in parallel over a time period of 300 min: 1500 g demineralized water and 41.2 g potassium hydroxide. After 180 min 99.8 g demineralized water, 4 g potassium peroxodisulfate, 0.2 g sodium hydroxide, 0.2 g sodium bicarbonate are added to the reaction mixture. After 330 min 43.6 g demineralized water, 1.6 g potassium peroxodisulfate, 0.1 g sodium hydroxide, 0.1 g sodium bicarbonate are added to the reaction mixture. Afterwards the reaction mixture is polymerized for another 240 min at 80° C. The resulting latex has a total solid content of 33.1 wt.-% and a pH of 8.58. The polymeric compatibilizing agent C-3 had a weight average molecular weight Mw of 340,000 g/mol.

(17) The weight average molecular weight Mw of the polymeric compatibilizing agents C-1, C-2 or C-3 was determined by gel permeation chromatography using UV-detection.

(18) Polystyrene was used as standard. Tetrahydrofuran with 0.25 wt.-% tetrabutylammoniurn bromide was used as solvent.

(19) Compatibilized Nanoparticles

(20) In several examples, the inorganic metal compound nanoparticles B-1 were reacted with the polymeric compatibilizing agents C-1, C-2 or C-3 in order to obtain compatibilizer nanoparticles, which are then used in the preparation of the thermoplastic polymer composition (P) according to the invention. The reaction was carried out as follows: The total solid content of nanoparticle dispersion in THF was determined. The nanoparticle dispersion was added to a THF solution of the polymeric compatibilizing agent (C) in a mass ratio of 1:10. The mixture was stirred for several hours. Then, compatibilized nanoparticles were precipitated with cold methanol, the resulting solid was filtered (or centrifuged) off and dried.

(21) The mass ratio of constituent B to constituent C was determined by thermogravimetric analysis using a Mettler-Toledo® TGA/SDTA 851e with a heating rate of 10 K/min for a temperature range of 30-500° C. followed by an isothermal process at 500° C. for 5 min under nitrogen atmosphere. The resultant residue corresponds to the pure ZnO in the compatibilizer nanoparticles.

(22) The residue resulting from the compatibilizer nanoparticles B-1/C-1 was 10.5 wt.-%.

(23) The ratio of constituent B-1 to constituent C-1 was therefore about 1:9.

(24) The residue resulting from the compatibilizer nanoparticles B-1/C-2 was 12.4 wt.-%.

(25) The ratio of constituent B-2 to constituent C-1 was therefore about 1:7.

(26) The residue resulting from the compatibilizer nanoparticles B-1/C-3 was 11.1 wt.-%.

(27) The ratio of constituent B-1 to constituent C-3 was therefore about 1:8.

(28) Constituent D: D-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).

(29) Sample Preparation

(30) All samples have been prepared via kneading using a Haake™ Rheomix 600p (residence time 30 min, Volume 58 ml, rotational speed 30 rpm). The temperature for the kneading was 200° C. for Examples 1 to 3, respectively 230° C. for Example 4 to 7 and Comparative Example 1. The test specimens have been produced using a DSM Xplore® Micro Injection Molder (melt temperature: 230° C., mold temperature: 80° C., preheating time for polymer melt 2.5 min (for Examples 1 to 3) respectively 4 min (for Example 4 to 7 and Comparative Example 1). After injection molding the samples have been pressed using a Carver® 25-12-2HC hot press between Nowofol® PFA foils with a metal spacer (1.0 mm thickness); Temperature: 230° C., 2 min preheating, 1 min pressing with 6 t, cooling in water cooled press.

(31) The composition of the samples according to Example 1 to 7 and Comparative Examples 1 and 2 are given in Table 1.

(32) TABLE-US-00002 TABLE 1 Styrene-based Polymer compati- Modified poly- Example copolymer Nanoparticles bilizing agent siloxane compound No. (Constituent A) (Constituent B) (Constituent C) (Constituent D) Ex. 1 97 wt.-% A-1 3 wt.-% B-2 — — (SAN) (ZnO) Ex. 2 97 wt.-% A-1 3 wt.-% B-3 — — (SAN) (SnO.sub.2) Ex. 3 97 wt.-% A-1 3 wt.-% B-4 — — (SAN) (ZrO.sub.2) Ex. 4 82.4 wt.-% A-1 2 wt.-% B-1 15.6 wt.-% C-1 — (SAN) (ZnO) (S-AN-MSA) Ex. 5 65.7 wt.-% A-1 4 wt.-% B-1 30.3 wt.-% C-2 — (SAN) (ZnO) (S-AN-MSA) Ex. 6 63.1 wt.-% A-1 4 wt.-% B-1 32.9 wt.-% C-3 — (SAN) (ZnO) (S-AN-MSA) Ex. 7 96 wt.-% A-1 3 wt.-% B-4 — 1 wt.-% D-1 (SAN) (ZrO.sub.2) Comp. 100 wt.-% A-1 — — — Ex. 1 (SAN) Comp. 100 wt.-% A* — — — Ex. 2 (PMMA)

(33) Testing Methods

(34) 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 (F), where necessary.

(35) Scratch Resistance

(36) 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.

(37) Optical properties were evaluated according to ASTM Standard D 1003 using BYK Gardner Hazemeter.

(38) The test results are summarized in Table 2.

(39) TABLE-US-00003 TABLE 2 min. load for full Transmission Haze Example No. scratch [g] [%] [%] Ex. 1 300 — — Ex. 2 500 — — Ex. 3 600 — — Ex. 4 700 82 9.7 Ex. 5 700 71.7 3.6 Ex. 6 700 74.9 4.8 Ex. 7 800 — — Comp. Ex. 1 100 93 0.9 Comp. Ex. 2 600 — —

(40) Comparative Example 1 (pure SAN copolymer) shows only very limited scratch resistance. Already at 100 g normal load a full scratch mark is visible. On the other side Comparative Example 2 (pure PMMA, Plexiglas® 7N) shows significantly higher scratch resistance and required a minimum normal load of 600 g to achieve a full scratch mark. It was surprisingly found by the present inventors, that only small amounts of inorganic metal compound nanoparticles (B) are sufficient to significantly improve the scratch resistance of styrene-based copolymers.

(41) As can be seen from the above samples containing inorganic metal compound nanoparticles (B) (Examples 1 to 7), these polymer compositions require significantly higher normal loads to form a visible scratch mark of up to 800 g. Further improvements, may be obtained by the addition of polymeric compatibilizing agents (Example 4 to 6) or modified polysiloxane compounds (Example 7). Example 7 shows even higher scratch resistance compared to the otherwise identical Example 3.

Most of the Examples Exceed Comparative Example 2 (PMMA) Serving as a Benchmark

(42) Also in terms of scratch visibility the claimed samples are highly advantageous. Examples 4 to 6, comprising inorganic metal compound nanoparticles (B) in combination with a polymeric compatibilizing agent (C) in accordance with the invention, show good optical properties and are still transparent, despite the high inorganic metal compound nanoparticle (B) concentration.