UV-STABILIZED POLYMER COMPOSITIONS AND METHODS FOR THEIR PRODUCTION

Abstract: Polymer compositions resistant to UV-induced color changes and methods for their production are provided. These compositions comprise an organic dye or pigment that fades upon exposure to UV-light thereby compensating for ("masking") UV-induced color changes.

Description: UV-STABILIZED POLYMER COMPOSITIONS AND METHODS FOR THEIR PRODUCTION FIELD OF THE INVENTION The invention provides novel polymer compositions which are resistant to color changes induced by exposure to UV light . The invention further provides a method of producing polymers which are resistant to color change upon exposure to UV light. BACKGROUND OF THE INVENTION The adverse effects of sunlight on polymeric materials have been well reported in the literature. These effects include color changes (fading) , surface cracking, and dete- rioration of other physical as well as electrical properties . The deleterious effects of sunlight have been attributed to a complex set of reactions in which both the absorption of ultraviolet (UV) light and the presence of oxygen are participating events. Consequently, these phenomena have been termed "oxidative photodegradation" and are the subject of many technical articles (see, e.g., Chem . Abst . , 54:25970 (a) and 26004(d) (1960); and Chem . Abst . , 55:4037 (1961) ) . Photooxidation in its early stages is quite difficult to detect. However, the almost imperceptible chemical changes that occur slowly accumulate and often lead to visible physical effects such as discoloration, surface cracking and/or deterioration of mechanical and electrical properties of the polymer. The visible effects of oxidative photooxidation are naturally of prime concern to many end users of plastics. For example, this is a significant concern with plastics used in the computer or business electronics industry which are subject to discoloration "yellowing" after long term exposure to UV light. In order to alleviate the deleterious effects of UV radiation, various methods have been developed. For example, the use of protective coatings and incorporation of pigments such as carbon black which function as light screens and thereby block UV-radiation has been reported. Also, the removal of impurities that may facilitate the photooxidation process such as metals and metal compounds has been reported. Still further, the use of photostabilizers and antioxi- dants to prevent photooxidation has been reported. However, all of these methods suffer from disadvantages, e.g., they are not totally effective, are costly, and/or may adversely affect the desired properties of the particular polymer, e.g., physical properties such as rigidity, elasticity, etc. OBJECTS OF THE INVENTION Thus, it is an object of the invention to solve the problems of the prior art . More specifically, it is an object of the invention to provide novel and improved polymeric compositions which exhibit enhanced resistance to color changes induced by UV light . It is an even more specific object of the invention to provide novel and improved polymeric compositions which comprise at least one "fading dye" or "fading pigment" which fades upon exposure to UV light and thereby compensates for or "masks" a color change that the polymer would otherwise undergo upon exposure to UV light. It is a more specific object of the invention to pro- duce novel and improved polymeric compositions wherein UV light induced color changes are masked or offset by the addition of at least one "fading dye" or "fading pigment" which compensates for or masks such color change in combination with a thermal stabilizer. It is still another object of the invention to select fading dye or fading pigment combinations and concentrations appropriate for offsetting or masking UV light induced color changes in polymer compositions based on their performance when used in polymer compositions which are subjected to accelerated weathering conditions. It is a specific object of the invention to produce flame retardant high impact polystyrene (HIPS) and PC/ABS and ABS compositions wherein light induced color changes are offset or masked by the addition of one or more "fading dyes" or "fading pigments". DETAILED DESCRIPTION OF THE INVENTION The subject invention provides novel polymer compositions, such as high impact polystyrene (HIPS) compositions, wherein UV induced color changes, are effectively masked by the addition of one or more fading dyes or fading pigments, alone or in combination with conventional UV stabilizers and/or in combination with one or more thermal stabilizers. The present invention is suitable for any polymer which is subject to UV-induced color change. However, in the pre- ferred embodiments, the polymers will comprise those typically used in the manufacture of computers and other office equipment, such as high impact polystyrene, ABS, ASA, PC/ABS, PPO/PS blends, PVC and PVC blends. The present invention was conceived after an observa- tion by the inventor that polymer compositions, even those containing conventional UV stabilizers, often discolor when subjected to accelerated weathering conditions. More specifically, it was observed that high impact polystyrene compositions, even those containing conventional UV stabi- lizers, were subject to UV-induced discoloration when subjected to accelerated weathering conditions. As is well known in the polymer art, accelerated weathering conditions comprise test environments which have been designed to aid in predicting the color fastness of polymer compositions when exposed to workplace or outdoor illumination conditions. These test environments include illumina- tion from fluorescent, incandescent or window-filtered sunlight sources and thermal radiation. A well-known example thereof comprises the Xenon arc exposure procedure of ASTM D4459-86 (which can be carried out in a eatherometer or Xenotest type equipment) , or in other Xenon arc type equipments (such as Suntest device) . Other accelerated UV- exposure procedures exist and are used as well, for example, ASTM D4476-89. Based on these observations, the present inventor conceived that the color changes typically observed upon exposure of polymer compositions to UV light could be offset or potentially even totally masked by the addition of a "fading dye" or "fading pigment." More specifically, it was conceived that an organic dye or pigment that is UV-light instable and subject to color change when exposed to UV light, if used as an additive in polymer compositions, could effectively "mask" or "off-set" the color changes attributable to UV degradation in the polymer. Thus, the present invention exploits the UV-instability of specific compounds, i.e., organic dyes or pigments which fade when exposed to UV-light, by using these compounds as additives in order to produce polymer compositions which exhibit less color change when exposed to UV light . Therefore, in the context of the present invention, a "fading dye" or "fading pigment" refers to an organic dye or organic pigment, or a combination thereof, the initial color of which changes (fades) upon exposure to UV light in such a way that it masks or offsets a color change the polymer normally undergoes when subjected to accelerated weathering conditions. Ideally, the fading dye or fading pigment will mask any color change of the polymer composition when subjected to accelerated weathering conditions. However, in the present invention such fading dyes or pigments will embrace any organic dye or pigment, or combination thereof, which exhibits a color change upon exposure to UV light that significantly offsets and ideally totally masks the color change that the polymer would normally undergo upon exposure to accelerated weathering conditions. Exemplary fading dyes and pigments according to the invention include organic dyes and pigments such as anthra- quinones, quinophthalones, azo dyes/pigments, (phthalo) peri- nones, styryl compounds, cumulin, pyrazolon, naphthazin dyes, quinolines, as well as others. Further information on dyes can be found for example in Ullmann's Encyclopedia of Industrial Chemistry, 9:73-124 (1987); Kirk-Othmer' s Ency- clopedia of Chemical Technology, 8:159-212 (1979); and SRI International's Chemical Economic Handbook, "Dyes", 1996, pages 520.5000A-5005G. Similar chapters about (organic) pigments are found in these sources as well. Naturally, the fading dye must be stable (i.e., not degrade chemically) under the particular processing conditions used to convert the polymer formulation to its final form (e.g., injection molded article, blown film, etc) . The amount of the fading dye may be varied over wide concentrations. The concentration will vary dependent upon factors including the particular polymer, the nature of the UV environment that the polymer will be exposed to (e.g., workplace or outdoor illumination conditions) , the susceptibility of the polymer to UV-induced color changes, whether other UV stabilizers or thermal stabilizers are present, among other factors. In general, polymers which are to be used in laboratory environments will require the addition of lesser amounts of the fading dye or pigment than polymers which are to be used in outdoor environments where UV exposure is substantially higher. Based on the results obtained with several exemplary polymer compositions, the concentration of fading dye or pigment in a polymer for indoor usage will vary from about 1 to 5,000 ppm, more preferably from about 5 to 1000 ppm and most preferably from 10 to 500 ppm. The amount of fading dye or pigment in a polymer for outdoor usage will typically be significantly higher. Based on the results disclosed infra, it is anticipated that suitable amounts will range from about 1 to 10,000 parts per million, more preferably 5 to 2000 parts per million, and most preferably from about 10 to 1000 parts per million. In addition to the fading dye or pigment, or combinations thereof, other pigments such as inorganic pigments as exemplified by titanium dioxide, carbon black, iron oxide (red) , Cr/Sb or Ni/Sb titanates (yellow) , ultramarine blue (blue) , Cr oxide (green) , and the like may be present in the polymer composition. As noted, the particular fading dye or fading pigment will depend largely on the nature of the base polymer. Thus, for a given polymer formulation, the type and amount of dye or pigment is selected with a view toward compensating as much as possible the color change the formulation will undergo during a UV stability test such as the aforementioned ASTM D-4454-86 procedure. The amount and types of fading dye or fading pigment contained in a specific polymer composition will be determined in general by (i) exposing a desired polymer composition lacking fading dye or fading pigments to accelerated weathering conditions; (ii) evaluating the color change (s) by standard methods known in the polymer art; and (iii) based on the degree and nature of the color change (s) selecting a fading dye or pigment, or combination thereof, and an appropriate concentration, which effectively offsets and potentially totally masks such color change (s) . Standardized methods for quantifying color changes are well known in the art. For example, color changes may be quantified according to the Hunterlab system which expresses color change based on the delta E value, or according to the Cielab system which quantifies color changes based on the delta E* value. In the exemplified polymer compositions, color changes were, in general, determined according to the Cielab system which is conventionally used in Europe. However, the particular manner that color change is expressed is not essen- tial to the invention. All that is essential is that the color change be offset and ideally totally masked as a result of the addition of the fading dye or fading pigment . Thus, if the Hunterlab or Cielab system is used to express color change, it is desirable that the ΔE or ΔE* value be as low as possible, ideally zero. The Cielab system expresses ΔE* according to the following equation: ΔE* = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 In this formula, ΔL refers to the change in darkness or lightness (positive ΔL* means that the polymer has become darker (after the exposure) ; (negative) ΔL* means that the polymer has become lighter; Δ a* refers to the change of color in the red-green axis (positive means color change towards red range, nega- tive towards green range) ; and Δb* refers to color changes in the blue-yellow axis (positive color change means towards yellow range, negative toward blue range) . In the present invention, a fading dye or fading pig- ment will preferably reduce the ΔE* or ΔE value which is observed in the absence of the fading dye or pigment by at least 10%, more preferably by at least 50% and ideally up to 100%. The subject invention should be suitable for use in compensating for all types of color changes induced by UV- light, e.g. those on the yellow-blue axis (e.g. yellowing) and also shifts on the red-green axis. For example, in the case of polymers which are subject to yellowing, it is advantageous to add a yellow fading dye to compensate for the color change. Examples thereof include Oracet Yellow GHS ® (Ciba) , (Color Number Solvent Yellow 163, CI 58890) which is an anthraquinone type fading dye and Makrolex Gelb G ® (Bayer) (Disperse Yellow 54, CI 47020), which is a quinophthalone dye. In terms of measurement parameters used in ASTM E-308- 85 (Standard Method for Computing the Colors of Objects by Using the CIE System) , an internationally recognized standard for color stimulus evaluation, the fading dye should aid in minimizing "delta E*", the total color difference, following performance of the UV-stability test for the application of interest. In the case of business electronics applications, this test is typically the ASTM D-4439-86 300 hours xenon-arc lamp weatherometer exposure test. However, the particular test will depend upon the particular polymer and the UV-light conditions that it is to be ex- posed. Thus, where a polymer material manifests yellowing following a UV exposure test, as is quite often the case for styrenic polymers, a fading dye should be selected so as to minimize or neutralize this effect. This can be done, e.g., by using a yellow dye which will fade away to a colorless species due, it is believed, to destruction of its conjugated bond system under the influence of the UV light. As noted previously, the concept of using a fading dye to neutralize and/or minimize the UV-induced color change of a polymer formulation should have generic applicability. In particular, it should be broadly applicable to both flame retardant and non-flame retardant compositions; to compositions based not only on styrene polymers such as HIPS, but any organic polymer; and not only for color shifts toward the yellow axis (i.e., the "b*" axis according to ASTM E 308-85) but other color shifts as well (e.g., shifts on the red-green or "a*" axis) . By way of example, formulations based on HIPS and Saytex ® 8010 (proprietary structure; decabromodiphenylethane or 1, 2-ethylene-bis (pentabromophenyl) ) were observed to show a (slightly) negative delta a* and a (significantly) posi- tive b*, indicating a shift towards green (somewhat) and towards yellow (significantly) . These color changes were effectively minimized by adding the appropriate amount of a yellow fading dye to counter the respective changes on the "a*" and "b*" axes. In business electronics applications, the grey colored formulations commonly used do not require the high coloring strength of organic dyes; however, in accordance with the present invention, organic dyes are used because of their poorer UV-light stability relative to inorganic pigments and this provides the desired "fading" effect. The key is, of course, to judiciously select the particular type and concentration of fading dye to be used in the polymer formulation so as to maximize the reduction in ΔE or ΔE* . As discussed above, polymer formulations according to the invention also may comprise conventional UV-stabilizers, e.g., UV-absorbers, in order to further compensate for the other adverse effects of UV-radiation, including color changes. UV-stabilizers are well known in the art, and include hindered amine light stabilizers (HALS) and UV- absorbers like 2- (2 ' -hydroxypheny1) benzotriazoles, 2- hydroxybenzophenones, esters of substituted benzoic acids (like, for example, 3 , 5-di (t-butyl) , 4-hydroxybenzoic acid, n-hexyl ester), 2- (2 -hydroxypheny1) -1, 3 , 5-triazines, acryl- ates, nickel phenolates, oxalic acid diamides and benzoxazi- nones . Such UV-stabilizers are widely known and are commercially available. In the exemplified polymer compositions, Tinuvin ® 770 (bis (2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate) (HALS), Tinuvin P (benzotriazole light stabilizer (2- (2H-benzotria- zol-2-yl) -p-cresol) , Tinuvin ® 328 (benzotriazole light stabilizer (2-2H-benzotriazol-2-yl) -4, 6-ditertpentylphenol) , and Chimassorb ® 119 FL (hindered amine light stabilizer (HALS) ) were used. However, the present invention is not limited to the usage of any specific UV-stabilizer . Also, it is further advantageous that the subject polymer compositions comprise a thermal stabilizer as this has been discovered to result in a further reduction in UV- induced color changes of polymer subjected to accelerated weathering conditions. The selected thermal stabilizer should, of course, be stable under the particular polymer processing conditions and not adversely affect the properties of the particular polymer. Thermal stabilizers suitable for use in the invention include by way of example zeolite A, TSPP (tetrasodium pyrophosphate) , hydrotalcite type stabilizers (e.g., basic magnesium aluminum hydroxy carbonate) , epoxidized fatty acids such as epoxidized soybean oil (ESBO) , as well as other typical thermal stabilizers having known usage in other areas such as are used for the stabilization of PVC or thermally sensitive (cyclo) aliphatic brominated flame retardants (e.g., hexabromocyclodo- decane (HBCD) ) , etc. Also, antioxidants have a beneficial effect; examples are primary antioxidants (hindered phenols) and secondary antioxidants (phosphites, phosphonites and thioesters) ; other types are known from the literature. Also, the subject polymeric compositions will comprise other additives conventionally used therein such as impact modifiers, lubricants, processing aids, other colorants, primary and secondary antioxidants, metal deactivators, nucleating agents, fillers and reinforcing agents (like glass fibers), plasticizers, antistatic additives, etc. As discussed above, the subject invention is generic to any polymer wherein UV-induced color changes are a signifi- cant concern. This includes thermoplastic or thermoset polymers, such as styrenics (homopolymers and copolymers) , like HIPS, ABS and ASA; styrenic blends and alloys, such as PC/ABS; polyolefins, including by way of example PE and PP; PVC and PVC blends; engineering thermoplastics, including by way of example polyamides, polycarbonates, and polyesters; polyphenyleneoxide and polyphenyleneoxide blends, such as PPO/PS; syndiotactic polystyrene and polyketone . This list is only representative of suitable polymers which may be used in the present invention. Examples of such styrenic homopolymers include polysty- rene, poly (alphamethylstyrene) and poly (p-methylstyrene) . Examples of copolymers include copolymers of styrene or alpha-methylstyrene with dienes or acryl derivatives, such as styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene-alkylacrylate and -methacryl- ate, styrene-alkylmethacrylate, and styrene-acrylonitrile- methacrylate . Impact modified versions are typically used in applications like business electronics housings. Copolymers (statistical, block or graft copolymers or mixtures thereof) are often used. Examples of mixtures of higher impact resistance are, for example, above-mentioned styrenic homo- or copolymers with other polymers like, for example, a diene-polymer, an ethylene-propylene-diene terpolymer or a polyacrylate, or block copolymers like styrene- butadiene-styrene, styrene-isoprene-styrene, styrene-ethyl- ene/butylene-styrene or styrene-ethylene/propylene-styrene . Examples of graft copolymers are copolymers of styrene or alpha-methylstyrene like, for example, styrene on polybutadiene, styrene on polybutadiene-styrene or polybutadiene- acrylonitrile-copolymers, styrene and acrylonitrile or methylacrylonitrile on polybutadiene; styrene, acrylonitrile and methylmethacrylate on polybutadiene; styrene and maleic anhydride on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleic imide on polybutadiene; styrene and maleic imide on polybutadiene, styrene and alkylacryl- ates or alkylmethacrylates on polybutadiene; styrene and acrylonitrile on ethylene-propylene-diene terpolymers; styrene and acrylonitrile on polyalkylacrylates or polyalkylmethacrylates; styrene and acrylonitrile on acry- late-butadiene-copolymers; as well as mixtures of these with above-mentioned copolymers; examples are the well-known ABS, ASA, MBS, AES and other polymers. However, the invention is not limited thereto. In an especially preferred embodiment, the polymer will comprise a high impact polystyrene (HIPS) polymer composition. The concept of fading dyes to reduce color change after UV-exposure is applicable to both flame retarded as well as non-flame retarded polymers. Examples of flame retardants used in flame retarded polymer formulations that can benefit from the present invention can be found for example in Gachter/Muller "Polymer Additives" Handbook, publisher Carl Hanser, 1990, pages 717-721. However this is of course an incomplete list of flame retardants, as many new flame retardants have appeared on the market since the time of publication. Examples of brominated flame retardants include: ethylene-bis (pentabromophenyl) and alkylene-bis (pentabromophenyl) ethylene-bis (tetrabromophthalimide) , bis (tetrabromo- phthalimide) , and alkylene-bis (tetrabromo phthalimide) deca-, octa- and pentabromodiphenyloxide bis (tribromophenoxy) ethane octabromotrimethylphenylindane hexabromocyclododecane - tetrabromobisphenol-A and derivatives of tetrabromobis- phenol-A, like for example tetrabromobisphenol-A-bis (2- hydroxyethyl ether) and tetrabromobisphenol-A- bis (2,3- dibromopropyl ether) tetrabromobisphenol-A carbonate oligomers - tetrabromobisphenol-A based epoxy resins or "brominated epoxy oligomers" (low and high molecular weight) decabromobiphenyl brominated polystyrene poly (dibromostyrene) - poly (tribromostyrene) poly (pentabromobenzyl acrylate) tris (tribromophenoxy) triazine tetradecabromodiphenoxybenzene ethylene bis (dibromonorbornanedicarboximide) dibromoneopentylglycol and derivatives - tribromoneopentyl alcohol and derivatives tribromophenol derivatives tetrabromophthalic anhydride and derivatives poly (dibromophenylene oxide) pentabromotoluene - tetrabromodipentaerythritol tribromophenyl maleimide Examples of chlorinated flame retardants include: "Dechlorane Plus ® " "HET-acid" - chlorinated paraffins These flame retardants can be used in the typical concentrations, for example from 0.5 to 30 weight %, more typically from 5 to 20 weight %. It is known from the literature that metal oxides like Sb oxides or Na antimonate, or Sb-free synergists can be used in subject polymer formulations. Examples of other flame retardant systems are also known from literature. Examples include phosphorus-based FR's, such as triphenylphosphate, resorcinoldiphenylphosphate and other phosphates; red phosphorus; P/halogen systems; P/N systems; intumescent systems; inorganic systems, such as Mg hydroxide, aluminum trihydrate, boron-containing compounds and melamine-containing compounds; etc. In order that the concept of the invention may be further understood, the following examples are provided to further illustrate the subject invention. These examples are illustrative and the specific enumeration of detail therein should not be interpreted as limitations. EXAMPLE 1 In order to illustrate the advantages obtained according to the invention different high impact polystyrene formulations containing fading dyes were formulated and compared for their UV-stability under accelerated weathering conditions which comprised 300 hours of weatherometer exposure. After UV exposure, color change was quantified for the various polymer compositions using Hunterlab (ΔE values) and Cielab (ΔE* values) . These results are set forth below in Table 1. These results indicate that the addition of a fading dye or a pigment provides for significant masking of color changes induced by UV-exposure under accelerated weathering conditions. (The specific compounds contained in the exemplified compositions are identified in the Glossary provided after Example 3. ) Table 1 EXAMPLE 2 In this example, the effects of the addition of fading dyes to another polymer formulation, FR PC/ABS, were evaluated. Typically, about 50% to 90% of PC is used in PC/ABS blends. It is also known that varying the blend ratio (as well as other formulation ingredients of course) allows for fine tuning the property profile of the blend so that it is suitable for the intended application. For example, when the typical blend ratio of PC to ABS is used, generally increasing the weight % PC increases heat resistance (e.g. Vicat softening point and HDT (heat deflection temperature)) values, impact strength (e.g. Izod impact strength), and lowers flow (e.g. MFI (Melt Flow Index)). The FR PC/ABS used in this example contains ethylenebis (tetrabromophthalimide and antimony trioxide as the flame retardant system. Some key properties of this FR PC/ABS are as follows : Vicat 5 kg : 108 °C; Izod impact strength : 49 kJ/m2; MFI (260°C/5 kg) : 17 g/10 min.; UL-94 flammability rating at 1.6 mm specimen thickness : V-0. Color was evaluated before UV-exposure and after 100 hours in the Heraeus Suntest. These results are set forth in Table 2 below. It can be seen from the ΔE values obtained that the addition of the fading dye resulted in a significant reduction in color change (lower ΔE value) , even for a polymer composition lacking a conventional UV stabilizer. Table 2 UV-stabilitv of FR PC/ABS: Delta E color change after 100 hours Suntest exposure EXAMPLE 3 The UV-stability of other HIPS polymer compositions not containing a fading dye or thermal stabilizer were also compared after 300 hour Weatherometer exposure. These results are contained in Table 3 below. These results similarly indicate that the addition of a fading dye is an effective means for offsetting UV-induced color changes. Table 3 UV-stabilit of FR HIPS: Color change after 300 hours Weatherometer exposure (ASTM D4459-86) Glossary Compounds Contained in Exemplified Polymer Formulations The following is a list of the specific terms and compounds referred to in the Examples. Chi assorb 119FL ® Hindered Amine Light Stabilizer (HALS) . ΔE* The CIE L* , a*, b* , total color difference Δ£*=[ (ΔL*) 2 +(Δa*) 2 +(Δb*) 2 ] 12 . HIPS High Impact Polystyrene. Irgacolor 10408 ® Chrome Antimony Titanium Buff Rutile (Pigment Brown 24, Color Index 77310) . Irgacolor ® 10401 Nickel Antimony Titanium Yellow Rutile (pigment Yellow 53, Color Index 77788). Irganox 168 ® Irganophosphite : Phenol, 2 , 4 -bis (1 , 1-dimethyl ethyl) - , phosphite . Irganox 245 ® Hindered phenol. Irgaplastol CM50 ® 1/1 Mix of Carbon Black (Pigment Black 7 Colour Index 77266) and Calcium Carbonate. Kronos 2220 ® Titanium Dioxide white pigment. Oracet Yellow GHS® Anthraquinonoid dye (Solvent Yellow 163) . Rheoplast 39 ® Epoxidised triglyceride (Ciba) . S-8010 SAYTEX 8010 ® Flame Retardant (decabromodiphenyl ethane) . Sb 2 0 3 Antimony trioxide, Campine (Blue Star RG ® ) Tinuvin 770 ® Hindered Amines Light Stabilizer (Bis (2 , 2 , 6 , 6- tetramethyl-4-piperidyl) sebacate) . Tinuvin P® Benzotriazol Light Stabilizer (2- (2H-benzotriazol- 2-yl) -p-cresol. Vector 8508® D Styrene-Butadiene block copolymer. Zeoli te A ® Hydrated Sodium Aluminosilicate. Ceasi t PC ® (Calcium Stearate) Bayferrox 13OM: Fe203 , containing some Si02 + A1203 ; Pigment Red 101; Color Index 77491. Light yellow 6R (Lichtgelb 6R) : Chromrutilgelb; (Ti, Cr, Sb)02; Pigment Brown 24; Color Index 77310. Monarch 800: carbon black; Pigment Black 7; Color Index 77266. Makrolex Gelb G: quinophtalone dye; Disperse Yellow 54; Color Index 47020. As is apparent from the foregoing, the present invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto-appended claims.

Claims: HAT IS CLAIMED IS: 1. A polymeric composition having enhanced resistance to color change (s) induced by exposure to UV light which comprises : (i) a polymer composition which is subject to UV- induced color change (s); and (ii) an amount of at least one fading dye or fading pigment sufficient to significantly mask or offset the UV- induced color change (s) that would otherwise occur in the absence of said fading dye or pigment when said polymer composition is subjected to accelerated weathering conditions . 2. The polymer composition of Claim 1, wherein the polymer is selected from the group consisting of polypropyl- enes, polyethylenes and other polyolefins; styrenics, homo- polymerics and copolymerics selected from the group consisting of HIPS (high impact polystyrene) , ABS and ASA; styrenic blends and alloys like PC/ABS; polyvinylchloride and polyvinylchloride blends; engineering thermoplastics selected from the group consisting of polyamides, polycarbonates, polyesters, polyphenyleneoxide and polyphenyleneoxide blends; syndiotactic polystyrene; and polyketone. 3. The polymer composition of Claim 2, wherein the polymer is a styrenic homopolymer or copolymer, styrenic blend or styrenic alloy. 4. The polymer composition of Claim 3, wherein the styrenic polymer is selected from the group consisting of polystyrene, poly (alphamethylstyrene) and poly (p-methylstyrene) , styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene-alkyl- acrylate, styrene-butadiene-methacrylate, styrene-alkylmeth- acrylate, styrene-acrylonitrile-methacrylate, acrylonitrile- butadiene-styrene and polycarbonate/acrylonitrile-butadiene- styrene . 5. The polymer composition of Claim 1, wherein the polymer is a high impact polystyrene or ABS or PC/ABS. 6. The polymer composition of Claim 1, wherein the polymer is selected from the group consisting of: styrene- butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene-alkylacrylate and -methacrylate, styrene- alkylmethacrylate, and styrene-acrylonitrile-methacrylate, styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene/butylene-styrene, or styrene-ethylene/propyl- ene-styrene, styrene on polybutadiene, styrene on polybuta- diene-styrene, polybutadiene-acrylonitrile-copolymers, styrene and acrylonitrile or methylacrylonitrile on polybutadiene; styrene, acrylonitrile and methylmethacrylate on polybutadiene; styrene and maleic anhydride on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleic imide on polybutadiene; styrene and maleic imide on polybutadiene, styrene and alkylacrylates or alkylmethacrylates on polybutadiene; styrene and acrylonitrile on ethylene- propylene-diene terpolymers; styrene and acrylonitrile on polyalkylacrylates or polyalkylmethacrylates; styrene and acrylonitrile on acrylate-butadiene-copolymers; and mixtures thereof; or mixed with the styrenic polymers recited in Claim 4. 7. The polymer composition of Claim 1, wherein the fading dye or pigment is a anthraquinone or quinophthalone . 8. The polymer composition of Claim 1, wherein the fading dye or pigment provides for a masking of UV-induced color change as evidenced by a reduction of ΔE or ΔE* of at least 10% when color change is determined according to the Hunterlab or Cielab system. 9. The polymer composition of Claim 7, wherein the fading dye or pigment provides for at least a 50% reduction in the ΔE or ΔE* value. 10. The polymer composition of Claim 1, which additionally comprises at least one UV-stabilizer . 11. The polymer composition of Claim 1, which additionally comprises at least one thermal stabilizer. 12. The polymer composition of Claim 1, wherein the reduction in color change is measured after exposure of the polymer composition in a weatherometer. 13. The polymer composition of Claim 12, wherein the exposure is effected for about 300 hours. 14. The polymer composition of Claim 1, which further comprises a flame retardant. 15. The polymer composition of Claim 14 wherein said flame retardant is selected from the group consisting of : ethylene-bis (pentabromophenyl) and alkylene-bis (pentabromophenyl) , ethylene-bis (tetrabromophthalimide) , bis (tetra- bromophthalimide), and alkylene-bis (tetrabromo phthalimide), deca-, octa- and pentabromodiphenyloxide, bis (tribromophen- oxy) ethane, octabromotrimethylphenylindane, hexabromocyclo- dodecane, tetrabromobisphenol-A and derivatives, tetrabromo- bisphenol-A-bis (2-hydroxyethyl ether), tetrabromobisphenol- A- bis (2, 3-dibromopropyl ether), tetrabromobisphenol-A carbonate oligomers, tetrabromobisphenol-A based epoxy resins, "brominated epoxy oligomers" (low and high molecular weight) , decabromobiphenyl , brominated polystyrene, poly (dibromostyrene) , poly (tribromostyrene) , poly (pentabromobenzyl acrylate), tris (tribromophenoxy) triazine, tetradecabromodiphenoxybenzene, ethylene bis (dibromonorbornanedicarboximide) , dibromoneopentylglycol and derivatives, tribromoneopentyl alcohol and derivatives, tribromophenol derivatives, tetrabromophthalic anhydride and derivatives, poly (dibromophenylene oxide), pentabromotolu- ene, tetrabromodipentaerythritol, tribromophenyl maleimide, "Dechlorane Plus ® ", "HET-acid" , and chlorinated paraffins. 16. A method for producing a polymer composition wherein color change (s) induced by UV-light under accelerat- ed weathering conditions are substantially masked or offset, comprising: (i) providing a polymer composition lacking any fading dye or pigment; (ii) exposing said polymer composition to accelerated weathering conditions; (iii) evaluating the color change (s) according to known methods ; and (iv) selecting based on the color change observed in (iii) , a fading dye or pigment or combination thereof which effectively offsets or masks said color change (s) . 17. The method according to Claim 16, which further comprises : (v) providing a polymer composition containing said selected fading dye or pigment or combination thereof; (vi) evaluating the color change (s), if any, of said polymer composition after exposure to accelerating weathering conditions. 18. The method of Claim 17, which further comprises comparing the color change (s) obtained with different fading dye or pigment combinations in order to identify the fading dye or pigment combination which results in maximal masking of UV-induced color change (s) . 19. The method of Claim 16, wherein accelerated weathering conditions comprise exposure of the polymer to about 300 hours in a weatherometer. 20. The method of Claim 16, wherein the polymer is selected from the group consisting of polypropylenes, poly- ethylenes and other polyolefins, styrenics, homopolymers or copolymers selected from the group consisting of HIPS, ABS and ASA; styrenic blends and alloys like PC/ABS; polyvinyl- chloride and polyvinylchloride blends; engineering thermoplastics, selected from the group consisting of polyamides, polycarbonates and polyesters; polyphenyleneoxide and polyphenyleneoxide blends; syndiotactic polystyrene and polyke- tone . 21. The polymer composition of Claim 20, wherein the polymer is a styrenic homopolymer or copolymer, styrenic blend or styrenic alloy. 22. The polymer composition of Claim 21, wherein the styrenic polymer is selected from the group consisting of polystyrene, poly (alphamethylstyrene) and poly (p-methylstyrene) , styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene-alkyl- acrylate, styrene-butadiene-methacrylate, styrene-alkylmeth- acrylate, styrene-acrylonitrile-methacrylate, acrylonitrile- butadiene-styrene and polycarbonate/acrylonitrile-butadiene- styrene . 23. The method of Claim 13, wherein the polymer is selected from the group consisting of styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene- butadiene-alkylacrylate and -methacrylate, styrene-alkyl- methacrylate, and styrene-acrylonitrile-methacrylate, sty- rene-butadiene-styrene, styrene-isoprene-styrene, styrene- ethylene/butylene-styrene, or styrene-ethylene/propylene- styrene, styrene on polybutadiene, styrene on polybutadiene- styrene or polybutadiene-acrylonitrile-copolymers, styrene and acrylonitrile or methylacrylonitrile on polybutadiene; styrene, acrylonitrile and methylmethacrylate on polybutadi- ene; styrene and maleic anhydride on polybutadiene; styrene, acrylonitrile and maleic anhydride or maleic imide on polybutadiene; styrene and maleic imide on polybutadiene, styrene and alkylacrylates or alkylmethacrylates on polybutadiene; styrene and acrylonitrile on ethylene-propylene-diene terpolymers; styrene and acrylonitrile on polyalkylacrylates or polyalkylmethacrylates; styrene and acrylonitrile on acrylate-butadiene-copolymers; and mixtures thereof, or mixed with the styrenic polymers recited in Claim 4. 24. The method of Claim 13 , wherein the polymer composition comprises at least one flame retardant. 25. The method of Claim 24, wherein said flame retardant is selected from the group consisting of: ethyl- ene-bis (pentabromophenyl) and alkylene-bis (pentabromophenyl) , ethylene-bis (tetrabromophthalimide) , bis (tetrabromophthalimide) , and alkylene-bis (tetrabromo phthalimide) , deca-, octa- and pentabromodiphenyloxide, bis (tribromophen- oxy) ethane, octabromotrimethylphenylindane, hexabromocyclo- dodecane, tetrabromobisphenol-A and derivatives, tetrabromo- bisphenol-A-bis (2-hydroxyethyl ether), tetrabromobisphenol- A- bis (2, 3-dibromopropyl ether), tetrabromobisphenol-A carbonate oligomers, tetrabromobisphenol-A based epoxy resins, "brominated epoxy oligomers" (low and high molecular weight), decabromobiphenyl , brominated polystyrene, poly (dibromostyrene) , poly (tribromostyrene) , poly (pentabromobenzyl acrylate), tris (tribromophenoxy) triazine, tetradecabromodiphenoxybenzene, ethylene bis (dibromonorbornanedicarboximide) , dibromoneopentylglycol and derivatives, tribromoneopentyl alcohol and derivatives, tribromophenol derivatives, tetrabromophthalic anhydride and derivatives, poly (dibromophenylene oxide), pentabromotolu- ene, tetrabromodipentaerythritol, tribromophenyl maleimide, "Dechlorane Plus ® ", "HET-acid" , and chlorinated paraffins. 26. The polymer composition of Claim 22, which is mixed with a styrenic polymer selected from the group consisting of polystyrene, poly (alphamethylstyrene) and poly (p-methylstyrene) , styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene-alkyl- acrylate, styrene-butadiene-methacrylate, styrene-alkylmeth- acrylate, styrene-acrylonitrile-methacrylate, acrylonitrile- butadiene-styrene and polycarbonate/acrylonitrile-butadiene- styrene . 27. The method of Claim 23, wherein the composition is further mixed with a styrenic polymer selected from the group consisting of polystyrene, poly (alphamethylstyrene) and poly (p-methylstyrene) , styrene-butadiene, styrene-acrylonitrile, styrene-maleic anhydride, styrene-butadiene- alkylacrylate, styrene-butadiene-methacrylate, styrene- alkylmethacrylate, styrene-acrylonitrile-methacrylate , acrylonitrile-butadiene-styrene and polycarbonate/acrylo- nitrile-butadiene-styrene .

Inventors: DESCHRYVER DANIEL, DESCHRYVER, DANIEL
Applicants: ALBEMARLE CORP, DESCHRYVER DANIEL, ALBEMARLE CORPORATION, DESCHRYVER, DANIEL
Application year: 1997
Main classification: D06P5
IPC codes: C08K5