STYRENE COPOLYMER MOLDING COMPOSITIONS WITH REDUCED MOLD DEPOSIT FORMATION FOR HIGH GLOSS APPLICATIONS

Abstract

The invention relates to a thermoplastic molding composition (P) comprising: (A) 81.1 to 99.7 wt. -% of at thermoplastic polymer composition (A) comprising: (A-1) graft copolymer (A-1), and (A-2) thermoplastic matrix (A-2) based on vinylaromatic copolymers; (B) at least one hindered amine light stabilizing composition (B) comprising: (B-1) 0.2 to 0.9 wt.-%, of at least one hindered amine light stabilizer having a dipiperidine structure with at least one alkyl group at each of the 2 and 6 positions of the dipiperidine structure and (B-2) 0.1 to 0.9 wt.-%, of a hindered amine light stabilizer mixture having a monopiperidine structure with at least one alkyl group at each of the 2 and 6 positions of the monopiperidine structure and (B-3) 0 to 2 wt.-%, of at least one hindered amine light stabilizer having a polymeric structure comprising piperidine groups with at least one alkyl group at each of the 2 and 6 positions of the piperidine groups, (C) 0 to 10 wt.-%, of colorants, dyes and/or pigments (C); and (D) 0 to 5 wt.-%, of further additives (D) different from (B) and (C); provided that the thermoplastic molding composition (P) further comprises 0.001 wt.-% to 0.1 wt.-%, based on the total weight of the molding composition (P), of oligomers and/or polymers comprising ethylene and/or propylene repeating units or provided that the thermoplastic molding composition (P) further comprises 0 wt.-%, based on the total weight of the molding composition (P), of oligomers and/or polymers comprising ethylene and/or propylene repeating units (as component E), wherein the constituents (A) to (E) sum up to 100 wt.-% of the molding composition (P).

Claims

1-14. (canceled)

15. A thermoplastic molding composition (P) comprising: (A) 81.1 to 99.7 wt.-%, based on the total weight of the molding composition (P), of at least one thermoplastic polymer composition (A) comprising: (A-1) 5 to 50 wt.-%, based on the total weight of thermoplastic polymer composition (A), of at least one styrene-based graft copolymer (A-1), and (A-2) 40 to 80 wt.-%, based on the total weight of thermoplastic polymer composition (A), of a thermoplastic matrix (A-2) comprising 40 to 60 wt.-% of poly(styrene-acrylonitrile) (SAN) and 60 to 40 wt.-% of poly(alpha-methyl styrene/acrylonitrile) (AMSAN), based on the total weight of the thermoplastic matrix (A-2); (B) at least one hindered amine light stabilizing composition (B) comprising: (B-1) 0.2 to 0.9 wt.-%, based on the total weight of the molding composition (P), of at least one hindered amine light stabilizer having a dipiperidine structure with at least one alkyl group at each of the 2 and 6 positions of the dipiperidine structure and not containing any saturated or unsaturated C12-C21 ester moieties at one of the 3, 4, or 5 positions of the piperidine structures, wherein the at least one hindered amine light stabilizer having a dipiperidine structure has a molecular weight of 200-550 g/mol, (B-2) 0.1 to 0.9 wt.-%, based on the total weight of the molding composition (P), of a hindered amine light stabilizer mixture having a monopiperidine structure with at least one alkyl group at each of the 2 and 6 positions of the monopiperidine structure and saturated or unsaturated C12-C21 ester moieties at at least one of the 3, 4, or 5 positions of the monopiperidine structures, and (B-3) 0 to 2 wt.-%, based on the total weight of the molding composition (P), of at least one hindered amine light stabilizer having a polymeric structure comprising piperidine groups with at least one alkyl group at each of the 2 and 6 positions of the piperidine groups and not containing any saturated or unsaturated C12-C21 ester moieties at one of the 3, 4, or 5 positions of the piperidine groups, wherein the at least one hindered amine light stabilizer having a polymeric structure has a molecular weight of 1000-4000 g/mol; (C) 0 to 10 wt.-%, based on the total weight of the molding composition (P), of one or more colorants, dyes, and/or pigments (C); and (D) 0 to 5 wt.-%, based on the total weight of the molding composition (P), of one or more further additives (D) different from (B) and (C); provided that the thermoplastic molding composition (P) further comprises 0.001 to 0.1 wt.-%, based on the total weight of the molding composition (P), of oligomers and/or polymers comprising ethylene repeating units and/or propylene repeating units (as component E), or provided that the thermoplastic molding composition (P) further comprises 0 wt.-%, based on the total weight of the molding composition (P), of oligomers and/or polymers comprising ethylene repeating units and/or propylene repeating units (as component E), wherein the constituents (A) to (E) sum up to 100 wt.-% of the molding composition (P).

16. The molding composition (P) according to claim 15, wherein the hindered amine light stabilizing composition (B) comprises: (B-1) 0.2 to 0.9 wt.-%, based on the total weight of the molding composition (P), of a compound represented by the chemical formula (I): ##STR00013## (B-2) 0.1 to 0.9 wt.-%, based on the total weight of the molding composition (P), of a composition comprising at least one compound represented by the chemical formula (II): ##STR00014## and (B-3) 0 to 2 wt.-%, based on the total weight of the molding composition (P), of a compound represented by the chemical formula (Ill): ##STR00015##

17. The molding composition (P) according to claim 15, comprising as component (E): 0.001 to less than 0.1 wt.-%, based on the total weight of the molding composition (P), of one or more oligomeric or polymeric components (E) comprising repeating units derived from ethylene monomers or propylene monomers, and wherein the constituents (A) to (E) sum up to 100 wt.-% of the molding composition (P).

18. The molding composition (P) according to claim 15, comprising essentially no oligomeric or polymeric components (E) comprising repeating units derived from ethylene monomers or propylene monomers, and wherein the constituents (A) to (E) sum up to 100 wt.-% of the molding composition (P).

19. The molding composition (P) according to claim 15, wherein the at least one graft copolymer (A-1) comprises or consists of an acrylonitrile styrene acrylate (ASA) copolymer having comprising rubber particles having an average particle size d.sub.50 of the rubber particles in the acrylonitrile styrene acrylate (ASA) copolymer from 50 to 1000 nm, wherein the average particle size is determined by scattered light measurement.

20. The molding composition (P) according to claim 15, wherein the at least one thermoplastic polymer composition (A) comprises at least one copolymer (A-2) comprising: 18 to 45 wt.-% of at least one type of vinyl cyanide repeating units; and 55 to 82 wt.-% of at least one type of vinylaromatic repeating units.

21. The molding composition (P) according to claim 15, wherein the at least one thermoplastic polymer composition (A) comprises: (A-1) 5 to 50 wt.-%, based on the thermoplastic polymer composition (A), of at least one graft copolymer (A-1) comprising or consisting of an acrylonitrile styrene acrylate (ASA) copolymer having an average particle size d.sub.50 of the rubber particles in the acrylonitrile styrene acrylate (ASA) copolymer from 50 to 1000 nm, wherein the average particle size is determined by scattered light measurement; (A-2) 40 to 80 wt.-%, based on the thermoplastic polymer composition (A), of at least one thermoplastic matrix (A-2) comprising 18 to 45 wt.-%, based on the total weight of the thermoplastic matrix (A-2), of at least one type of vinyl cyanide repeating units and 55 to 82 wt.-%, based on the total weight of the thermoplastic matrix (A-2), of at least one type of vinylaromatic repeating units; and (A-3) 0 to 75 wt.-%, based on the thermoplastic polymer composition (A), of one or more additional thermoplastic polymers (A-3) that is substantially free of ethylene repeating units and/or propylene repeating units.

22. The molding composition (P) according to claim 15, wherein the graft copolymer (A-1) comprises a bimodal or trimodal size distribution of the rubber particles comprising: (A-1a) at least one graft copolymer (A-1a) having an average particle size d.sub.50 of the rubber particles in the ASA copolymer from 50 to 150 nm; and (A-1b) at least one graft copolymer (A-1b) having an average particle size d.sub.50 of the rubber particles in the ASA copolymer from 200 to 750 nm.

23. The molding composition (P) according to claim 15, wherein a high gloss surface area on a molded article (T) produced from the molding composition (P) that exhibits a gloss level above 75 gloss units before any weathering exposure, keeps a gloss level of above 75% of the gloss level before weathering after being subjected to artificial weathering according to ISO 4892-2A for 2400 h, wherein the gloss level is determined according to DIN EN ISO 2813 at a measuring angle of 60? .

24. The molding composition (P) according to claim 15, wherein a high gloss surface area on a molded article (T) produced from the molding composition (P) that exhibits a gloss level above 75 gloss units before any weathering exposure exhibits a color shift dE as measured in reference to the unexposed surface of below dE=6 after being subjected to artificial weathering according to ISO 4892-2A for 2400 hours, wherein the gloss level is determined according to DIN EN ISO 2813 at a measuring angle of 60?.

25. A method for producing the thermoplastic molding composition (P) according to claim 15, the method comprising at least the following steps: (i) providing the components (A) to (E) in the predetermined amounts to a mixing device; and (ii) blending the components (A) to (E) in the mixing device at temperatures above the glass transition point of the components (A) to obtain the molding composition (P).

26. A method for reducing mold deposit formation upon the molding of high gloss surface molded articles (T) with gloss levels above 75 gloss units on at least a part of the surface area of the molded article (T), wherein the gloss level is determined according to DIN EN ISO 2813 at a measuring angle of 60?, wherein the method comprises the step of compounding the constituents (A) to (E) according to claim 15, and wherein the reduction of mold deposit formation is observed as followed: reduction of the extent of formation of mold deposit during production of molded high gloss parts as assessed by visual inspection of the deposit formation on the mold in the vicinity of a weld line after production of 500 injection molded test specimens produced from the molding composition (P) in comparison to the extent of mold deposit formation from a comparative molding composition (P) molded and assessed with same conditions, wherein the comparative molding composition (P) is obtained by compounding the components (A) to (E) contained in the molding composition (P) and additionally at least 0.1 wt.-%, based on the total weight of the molding composition (P), of at least one oligomeric and/or polymeric components comprising ethylene repeating units and/or propylene repeating units.

27. A molded article (T) comprising high gloss surface areas with gloss levels above 75 gloss units prepared from a thermoplastic molding composition (P) according to claim 15, wherein the gloss level is determined according to DIN EN ISO 2813 at a measuring angle of 60?.

28. The molded article (T) according to claim 27, wherein the molded article (T) is an unpainted molded article for exterior applications.

29. The molded article (T) according to claim 28, wherein the unpainted molded article is for automotive applications.

Description

EXAMPLES AND COMPONENTS

[0234] Component A: The thermoplastic polymer composition (A) is an acrylonitrile styrene acrylate (ASA), i.e., an impact modified poly(styrene-acrylonitrile) (SAN) comprising SAN grafted on a butyl acrylate (BA) core (BA-g-SAN) (A-1a) and (A-1b) with the below-specified properties. [0235] Thermoplastic matrix polymer component A-2a: AMSAN (30 wt.-% ACN, 70 wt.-% alpha-methylstyrene, VN 57 ml/g) [0236] Thermoplastic matrix polymer component A-2b: SAN (35% ACN, VN 80 ml/g)

[0237] Component B-1: hindered amine light stabilizer (HALS) Tinuvin? 770 from BASF

[0238] Component B-2: hindered amine light stabilizer (HALS) Cyasorb? UV-3853 from Solvay as 50 wt.-% master batch in AMSAM (30 wt.-% acrylonitrite, 70 wt.-% alpha-methylstyrene, viscosity number 57 ml/g)

[0239] Component B-3: hindered amine light stabilizer (HALS) Chimassorb? 944 from BASF

[0240] Component C-1: Carbon black Black Pearls? 880 from Cabot as 30 wt.-% master batch in SAN with 24% acrylonitrile and viscosity number 64 ml/g.

[0241] Component D-1: Bis(2-propylheptyl)phthalate (DPHP) is a plasticizer

[0242] Component E-1: Polyethylene wax Licocene? PE 4201 available from Clariant

[0243] Component E-2: hindered amine light stabilizer (HALS) Cyasorb? UV-3853 from Solvay as 50 wt.-% master batch in polypropylene: Cyasorb? UV3853PP5 from Solvay

[0244] Component E-3: Eupolen? PE Black from BASF SE, master batch with 40% carbon black in polyethylene.

Preparation of Basic Rubber Latex L1

[0245] The reaction vessel was charged with 90.2 parts by weight of demineralized water, 0.61 parts by weight of the sodium salt of a C12- to C18- paraffin sulfonic acid and 0.23 parts by weight sodium bicarbonate. When the temperature in the reaction vessel reached 59? C., 0.16 parts by weight of sodium persulfate, dissolved in 5 parts by weight of demineralized water, were added. A mixture of 59.51 parts by weight butyl acrylate and 1.21 parts by weight tricyclodecenyl acrylate were added within a period of 210 min. Afterwards the reaction was continued for 60 min. Finally, the polymer dispersion had a total solid content of 39.6% and the latex particles had a particle diameter of 75 nm (determined by turbidity).

Preparation of Graft Rubber Latex (Component A-1a)

[0246] An amount of 151.9 parts by weight of the basic latex were added to the reaction vessel together with 92.2 parts by weight of demineralized water and 0.14 parts by weight of sodium persulfate, dissolved in 3.22 parts by weight of demineralized water. Within a period of 190 min a mixture of 31.18 parts by weight of styrene and 9.31 parts by weight of acrylonitrile were added at a temperature of 61? C., followed by a post polymerization time of 60 min at 65? C. A polymer dispersion with a total solid content of 35.5% was obtained. The latex particles had a diameter 87 nm (determined by turbidity). After synthesis, the latex was coagulated with magnesium sulfate solution at a temperature of approximately 60? C., followed by a sintering step at approximately 90? C. The resulting slurry was centrifuged yielding a wet rubber powder which was further processed.

Preparation of Basic Rubber Latex L2

[0247] The reaction vessel was charged with 70.66 parts by weight of demineralized water, 0.3 parts by weight of latex L1 and 0.23 parts by weight of sodium bicarbonate. After heating the reaction vessel to 60? C., 0.16 parts by weight of sodium persulfate, dissolved in 5 parts by weight demineralized water, were added to the reaction mixture. A mixture of 59.51 parts by weight butyl acrylate and 1.21 parts by weight tricyclodecenyl acrylate were added within a period of 210 min. In parallel to the first feed a solution of 0.36 parts by weight of the sodium salt of a C12- to C18-paraffin sulfonic acid in 16.6 parts by weight demineralized water were also added over a period of 210 min. After 200 min, from starting the feed, the temperature is ramped to 65? C.

[0248] Afterwards the reaction was continued for 60 min at 65? C. Finally, the polymer dispersion had a total solid content of 39.4% and the latex particles have a particle diameter of 440 nm (determined by turbidity).

Preparation of Graft Rubber Latex (Component A-1b)

[0249] An amount of 154 parts by weight of the basic latex were added to the reaction vessel together with 88.29 parts by weight of demineralized water, 0.11 parts by weight of the sodium salt of a C12- to C18-paraffin sulfonic acid and 0.14 parts by weight of sodium persulfate, dissolved in 5.61 parts by weight of demineralized water.

[0250] The reaction mixture was heated to 61? C. Within a period of 60 min 13.16 parts by weight are added at a temperature of 61? C., followed by a post polymerization time of 90 min, where the temperature was increased from 61 to 65? C. Then a mixture of 20.5 parts by weight of styrene and 6.83 parts by weight of acrylonitrile were added to the reaction over a period of 150 min. The reaction was continued at 65? C. for another 60 min. A polymer dispersion with a total solid content of 35.2% was obtained. The latex particles had a diameter 500 nm (determined by turbidity). After synthesis the latex was coagulated with magnesium sulfate solution at a temperature of approximately 88? C., followed by a sintering step at approximately 130? C.

[0251] The resulting slurry was centrifuged yielding a wet rubber powder which was further processed

Preparation of Molding Composition (P)

[0252] Examples and Comparative Examples of molding compositions were prepared by compounding all constituents using a twin screw extruder (model ZSK26MC, Coperion GmbH, length: 1035 mm) at Tm=240? C. according to the specific ratios given in Table 1. Sample plaques (approximately 7,5 x 5 cm) and other samples have been prepared via injection molding (Tm: 260? C.).

TABLE-US-00001 TABLE 1 Compounding Recipes Comp Comp Comp Comp in wt.-% Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 A-1a: (90 nm, BA-g-SAN) 19.8 19.8 19.5 19.2 19.6 19.5 A-1b: (500 nm, BA-g-SAN) 13.1 13.0 12.9 12.7 12.9 12.9 A-2a: AMSAN (30 wt.-% ACN, 70 29.2 29.1 28.8 31.2 28.9 28.8 wt.-% alpha-methylstyrene, VN 57 ml/g) A-2b: SAN (35% ACN, VN 80 33.9 33.9 33.5 32.9 33.6 33.5 ml/g) B-1: Tinuvin 770 0.20 0.49 0.48 0.49 0.49 B-2: Cyasorb 3853 as 50% MB in 0.59 0.59 AMSAN (30 wt.-% ACN, 70 wt.-% (0.29) (0.29) alpha-methylstyrene, VN 57 ml/g) (Cyasorb content) B-3: Chimassorb 944 0.29 C-1: Carbon black (as 30 wt.-% MB 3.96 3.95 3.90 3.92 3.90 in SAN 24% ACN, VN 64 ml/g) (1.19) (1.19) (1.17) (1.18) (1.17) (carbon black content) D-1: Plasticizer DPHP 0.05 0.05 0.05 0.05 0.05 0.05 E-1: Polyethylene Wax 0.34 0.34 0.34 0.34 E-2: Cyasorb 3853 as 50% MB in 0.59 0.58 polypropylene (Cyasorb content) (0.29) (0.29) E-3: Eupolen? PE Black (carbon 2.59 black content) (1.04) Examples and molding compounds with prefix comp- are for comparison

[0253] Herein, each BA-g-SAN (i.e., components A-1a and A-1b) comprises approximately 60 parts n-butyl acrylate (BA) containing a cross-linking agent, approximately 40 parts SAN (mass ratio styrene : acrylonitrile 1:3 to 1:4), and approximately 1 part of a further monomer such as, e.g., dihydrodicyclopentadienyl acrylate (DCPA) or tricyclodecenyl acrylate.

Weathering Conditions

[0254] The properties of the sample plaques were tested with respect to weathering conditions according to the following proceedings.

[0255] Simulation of moist warm climate was made according to ISO 4892-2A with the following parameter: [0256] black standard 65?2? C. (dry phase: 35-45? C.), relative humidity: 70?10%; [0257] irradiation: 0.51 W/m.sup.2 at 340 nm (or 60 W/m.sup.2 at a wavelength of 300-400 nm);

[0258] The test results were evaluated by color measurements according to DIN 6174 as well as gloss measurements according to DIN EN ISO 2813 at a measuring angle of 60?. All references to gloss levels and gloss measurements in this invention are understood to be measured according to these conditions.

[0259] Gloss retention in this invention is defined as the ratio in % between the measured gloss after weathering and the gloss before weathering. The results of the evaluation are given in Table 2.

[0260] To determine the extent of formation of deposit during production of the moldings, the abovementioned molding compositions and comparative molding compositions in the form of pellets were metered under identical conditions into an injection molding machine, and melted, and injection-molded in a mold for producing tensile specimens with a weld line and having no vents. Injection of the tensile specimen in this mold took place from the two ends, the result being that the two melt fronts met in the center of the mold and produced a weld line.

[0261] After every 500 shots, i.e. injection-molded test specimens, the mold was dismantled and the mold deposits occurring in the vicinity of the weld line were assessed visually and graded by a panel of persons skilled in the art on a scale from 1 (very good, no mold deposits) to 6 (unsatisfactory, high level of mold deposits).

[0262] The results of the evaluation are given in Table 2.

TABLE-US-00002 TABLE 2 Mold deposit formation and weathering results for high gloss surfaces Comp Comp Comp Comp in wt.-% Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 B1: Tinuvin 770 0.20 0.49 0.48 0.49 0.49 B2: Cyasorb 3853 as 50% MB in 0.59 0.59 AMSAN (30 wt.-% ACN, 70 wt.-% (0.29) (0.29) alpha-methylstyrene, VN 57 ml/g) (Cyasorb content) B3: Chimassorb 944 0.29 E1: Polyethylene Wax 0.34 0.34 0.34 0.34 E2: Cyasorb 3853 as 50% MB in 0.59 0.58 polypropylene (Cyasorb content) (0.29) (0.29) E3: Eupolen? PE Black (carbon 2.59 black content) (1.04) Results for high gloss plaques Grade for mold deposit formation 2 2-3 5-6 6 4 4 Gloss 60? before weathering 93.7 94.2 94.8 91.5 94.2 95.0 Color Shift dE after ISO 4892-2A weathering 1600 h 17.1 2.3 2.0 1.8 2.2 2400 h 18.0 14.5 4.6 3.2 1.6 3200 h 16.8 18.7 17.7 17.3 15.1 Gloss 60? retention in % after ISO 4892-2A weathering 1600 h 5.7 87.9 90.7 91.3 90.3 2400 h 3.0 26.0 78.6 83.0 90.8 3200 h 1.6 5.7 33.8 28.8 42.8

[0263] The results of mold deposit formation of Comp. Ex. 2 and Comp. Ex. 3 in Table 2 in comparison to Comp Ex. 1 show that the components B-1 and especially E-2 lead to increased deposits during the molding process. Comp Ex. 3 combining the use of components B-1 and E-2 shows significantly improved weathering performance with dE<5 and gloss retention above 75% after 2400 h weathering according to ISO 4892-2A compared to Comp. Ex. 1 and Comp. Ex. 2 showing that the components B-1 and E-2 are effective to improve weathering for 2400 h exposure but also lead to unacceptable mold deposit formation on high gloss surfaces.

[0264] The result of mold deposit formation in table 2 for Comp. Ex. 4 shows that the use of polyethylene as carrier material in a carbon black masterbatch even increases mold deposit formation in comparison to Comp. Ex. 3.

[0265] The inventive examples 1 and 2 in table 2 both show weathering performance similar to Comp. Ex. 3 with dE<5 and gloss retention above 75% after 2400 h exposure according to ISO 4892-2A but at the same time also show significantly reduced mold deposit formation when compared to Comp. Ex. 3 which is achieved by elimination of all components E containing polyolefins.

[0266] With the high gloss weathering stability after 2400 h and the same time low mold deposit formation of the examples of the inventive ASA formulation the technical demand outlined in this invention for high gloss surfaces can be answered.