TWI589638B - Heat and light resistant polymer composition - Google Patents

Description

Heat resistant and light resistant polymer composition

The present invention relates to a polymer composition comprising at least one polyester, at least one hindered amine compound, and at least one phosphorus compound selected from the group consisting of phosphites, sub- Phosphonates and mixtures thereof.

The invention further provides a portion of a filter article, such as a light emitting diode (LED) device, comprising the composition of the invention.

LEDs are increasingly used as light sources in a large number of applications due to their many advantages over conventional light sources. LEDs generally consume significantly less power than incandescent sources and other sources, require low operating voltages, and are resistant to mechanical shock. As such, they are replacing incandescent sources and other sources in many applications and have been used in such diverse fields as traffic signals, interior and exterior lighting, cell phone displays, car displays, and flashlights.

LED components, such as housings, reflectors, and reflector plates, require a particularly demanding combination of superior color and improved physical properties. Ceramics can advantageously be used in such applications, but ceramics are still extremely expensive and require highly demanding processing techniques. Therefore, the polymer composition has been extensively researched and developed to replace ceramics as a lower cost material. A significant benefit of polymers is that they can be injection molded and thus provide considerable design flexibility. LED applications require good opacity and excellent performance A polymer composition having reflective properties. One problem noted with regard to polymer compositions used in the manufacture of LED components is that they tend to yellow when exposed to light and high temperatures. For example, during the manufacturing process, the LED components are heated to about 180 ° C to cure the epoxy or enamel encapsulant. The LED components are also exposed to temperatures above 260 ° C during the soldering operation. Furthermore, in use, LED components, such as automotive components, have conventionally been subjected to temperatures above 80 °C. This exposure at elevated temperatures causes yellowing of the polymer composition used to form the LED components.

It is desirable that the reflector plates of LEDs and, finally, the polymer composition from which they are made, should meet a variety of requirements, notably including high light reflectivity (generally visible reflectance), high whiteness, Good processability (for example, good moldability), high dimensional stability (notably low linear expansion coefficient), high mechanical strength, high heat deflection temperature, and high heat resistance ( Low fading and low reflection loss when exposed to high temperatures).

Unfortunately, the various prior art polymer compositions used in LED applications are prone to yellowing when exposed to light and heat.

WO 2007/033129 discloses light-emitting diode element housings comprising a poly(1,4-cyclohexanedimethanol terephthalate) (PCT) composition. More specifically, WO 2007/033129 relates to a light-emitting diode element shell composition comprising from 40% to 95% by weight of PCT, from 5% by weight to 60% by weight of titanium dioxide, from 0 to 40% by weight At least one inorganic reinforcing agent or filler, and from 0 to 3% by weight of at least one oxidative stabilizer, wherein the weight percentages are based on the total weight of the composition.

Those skilled in the art will recognize that further improvements in thermal stability, molding performance, and reflectivity are advantageous for the development of LED devices.

The inventors have discovered that the presence of two particular additives greatly enhances the behavior of the polyester composition when subjected to simultaneous heat and light exposure in a synergistic manner.

The polyester composition according to the invention satisfies the above requirements and is explained in detail below.

In a first aspect, the present invention relates to a polymer composition comprising: at least one polyester; at least one hindered amine compound; and at least one phosphorus compound selected from the group consisting of Groups: phosphites, phosphonites, and mixtures thereof.

In a second aspect, the invention relates to articles comprising at least one portion comprising a polymer composition of the invention, and in particular to a portion of an LED device made from such a composition.

Detailed description of the invention

The polymer composition according to the invention comprises three essential ingredients which will be described in detail below:

Polyester

The term "polyester" is intended to mean a repeating unit comprising at least one ester moiety comprising at least 50 mole %, preferably at least 85 mole % (usually using the formula R-(C=O)-OR Described) a polymer. The polyester may be subjected to ring-opening polymerization of a cyclic monomer (M _A ) comprising at least one ester moiety, by polycondensation of a monomer (M _B ) comprising at least one hydroxyl group and at least one carboxylic acid group, or by The at least one monomer (M _C ) (a diol) comprising at least two hydroxyl groups is obtained by polycondensation of at least one monomer (M _D ) comprising at least two carboxylic acid groups (a dicarboxylic acid).

Non-limiting examples of the monomer (M _A ) include lactide and caprolactone.

Non-limiting examples of the monomer (M _B ) include glycolic acid, 4-hydroxybenzoic acid, and 6-hydroxynaphthalene-2-carboxylic acid.

Non-limiting examples of the monomer (M _C ) include 1,4-cyclohexane dimethanol; ethylene glycol; 1,4-butanediol; 1,3-propanediol; 1,5-pentanediol; 6-hexanediol; and neopentyl glycol, and 1,4-cyclohexanedimethanol and neopentyl glycol are preferred.

Non-limiting examples of the monomer (M _D ) include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, succinic acid, sebacic acid, and adipic acid, and terephthalic acid Preferred is cyclohexane dicarboxylic acid.

The polyester may be fully aliphatic, semi-aromatic or wholly aromatic depending on the choice of monomer.

The polyester of the composition of the invention may be a copolymer or a homopolymer.

When the polyester-based copolymer of the composition of the present invention is preferably at least 50 mol%, more preferably at least 60 mol%, still more preferably at least 70 mol%, even more preferably At least 80 mol%, and most preferably at least 90 mol% of the repeating units are obtained by polycondensation of terephthalic acid. Better At least 50 mole%, still more preferably at least 60 mole%, even more preferably at least 70 mole%, and most preferably at least 80 mole% of the repeat unit is by benzoquinone Obtained by the polycondensation of formic acid with 1,4-cyclohexane dimethanol.

When the polyester of the composition of the present invention is a homopolymer, it may be selected from the group consisting of polyethylene glycol or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone. (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PPT), polypair Trimethyl phthalate (PTT), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), poly(1,4-cyclohexyldimethylterephthalate) Acid ester) (PCT), and liquid crystal polyester (LCP). It is preferably selected from the group consisting of PBT, PTT, PEN, PET, PCT and LCP. More preferably, it is selected from the group consisting of PBT, PCT and LCP. More preferably, it is PCT (i.e., a homopolymer obtained by polycondensation of terephthalic acid with 1,4-cyclohexane dimethanol).

The polymer composition according to the invention may also comprise at least two polyesters. In such cases, the polyester is preferably selected from the group consisting of PCT and LCP or a blend of PBT and PCT.

The polyester used herein advantageously has an intrinsic viscosity of from about 0.6 to about 2.0 dl/g as measured in a 60:40 phenol/tetrachloroethane mixture or the like at about 30 °C. Polyesters which are particularly suitable for the present invention have an intrinsic viscosity of from 0.6 to about 1.4 dl/g.

The polyester used herein has a DSC test according to ISO-11357-3 The melting point of the amount is advantageously at least 250 ° C, preferably at least 260 ° C, more preferably at least 270 ° C and most preferably 280 ° C. Further, the melting point is at most 350 ° C, preferably at most 340 ° C, more preferably at most 330 ° C and most preferably at most 320 ° C.

Polyesters which are particularly suitable for the present invention have a melting point ranging from 280 °C to 320 °C.

The polyester is preferably present in an amount of at least 48% by weight, more preferably at least 50% by weight, still more preferably at least 52% by weight and most preferably at least 54% by weight, based on the total weight of the composition.

The polyester is also advantageously present in an amount of up to 90% by weight, preferably up to 85% by weight, more preferably up to 80% by weight, still more preferably up to 75% by weight, based on the total weight of the composition, And the best is up to 70% by weight.

Excellent when the polyester is present in the composition in an amount of from about 48% by weight to about 90% by weight, based on the total weight of the composition, preferably from about 50% by weight to about 70% by weight. result.

Hindered amine compound

The polymer composition according to the invention comprises, in addition to the polyester, at least one hindered amine compound.

The term "hindered amine compound" is intended to mean a derivative of 2,2,6,6-tetramethylacridine which is well known in the art (see, for example, Handbook of Plastic Additives , 5th Edition, Hanse, 2001 ( Plastics Additives Handbook , 5th ed., Hanser, 2001)). The hindered amine compound of the composition according to the invention may have a low molecular weight or a high molecular weight.

The low molecular weight hindered amine compound typically has a molecular weight of at most 900, preferably at most 800, more preferably at most 700, still more preferably at most 600 and most preferably at most 500 g/mol.

Examples of low molecular weight hindered amine compounds are listed in Table 1 below:

Among the low molecular weight compounds, the hindered amine is preferably selected from the group consisting of the following: corresponding to the chemical formulas (a1), (a2), (a11) and (a12). More preferably, the hindered amine is selected from the group consisting of: those corresponding to the chemical formulas (a1), (a2), and (a12). Still more preferably, the hindered amine corresponds to a hindered amine of formula (a2).

High molecular weight hindered amine compounds are typically polymeric and typically have a molecular weight of at least 1000, preferably at least 1100, more preferably at least 1200, still more preferably at least 1300 and most preferably at least 1400 g. /mol.

Examples of high molecular weight hindered amine compounds are listed in Table 2 below:

"n" in the chemical formulas (b1) to (b6) of Table 2 represents the number of repeating units in the polymer and is usually an integer equal to or greater than 4.

Among the high molecular weight compounds, the hindered amine is preferably selected from the group consisting of: those corresponding to the chemical formulas (b2) and (b5). More preferably, the hindered amine corresponds to a hindered amine of formula (b2).

The hindered amine compound is typically present in an amount of at least 0.05% by weight, more preferably at least 0.1% by weight, still more preferably at least 0.15% by weight and most preferably at least 0.2%, based on the total weight of the composition. %.

The hindered amine compound is typically present in an amount of advantageously up to 3.5% by weight, preferably up to 3% by weight, more preferably up to 2.5% by weight, still more preferably up to 2.0, based on the total weight of the composition. % by weight, even more preferably up to 0.8% by weight and most preferably up to 0.6% by weight.

When the hindered amine compound is present in the composition in an amount of from about 0.05% by weight to about 2% by weight, based on the total weight of the composition, preferably from about Excellent results are obtained from 0.1% by weight to about 0.8% by weight, and more preferably from about 0.2% by weight to about 0.6% by weight.

Phosphorus compound

The polymer composition according to the present invention comprises, in addition to the polyester and the at least one hindered amine compound, at least one phosphorus compound selected from the group consisting of phosphites, phosphonites. Classes and mixtures thereof.

The phosphite may be represented by the chemical formula P(OR) ₃ , and the phosphonite may be represented by the chemical formula P(OR) ₂ R, wherein each R may be the same or different and is typically independently selected from the group consisting of Group: C _1-20 alkyl, C _3-22 alkenyl, C _6-40 cycloalkyl, C _7-40 cycloalkylene, aryl, alkaryl or aralkyl moiety.

Phosphorus compounds present in the compositions according to the invention are well known in the art and are listed and detailed, for example, in the Plastic Additives Handbook , 5th Edition, Hanse, 2001.

Examples of phosphites are listed in Table 3 below:

Among the phosphites, the phosphorus compound is preferably selected from the group consisting of the following: corresponding to the chemical formulas (α1), (α9) and (α12). More preferably, the phosphorus compound is selected from the group consisting of: Corresponding to the chemical formulas (α5) and (α9). Still more preferably, the phosphite corresponds to a phosphite of the formula (?5).

Examples of phosphonites are listed in Table 4 below:

Preferably, the phosphonite corresponds to a phosphonite of the formula (β1).

The phosphorus compound is preferably a phosphite and most preferably a phosphite corresponding to the formula (?5) as described above.

The phosphorus compound is preferably present in an amount of at least 0.3% by weight, more preferably at least 0.5% by weight, still more preferably at least 0.7% by weight and most preferably at least 0.8% by weight, based on the total weight of the composition.

The phosphorus compound is preferably present in an amount of up to 5% by weight, more preferably up to 3% by weight, still more preferably up to 2.5% by weight, even more preferably up to 2% by weight based on the total weight of the composition. %, and the best is Up to 1.8% by weight.

When the phosphorus compound is present in the composition in an amount of from about 0.3% by weight to about 5% by weight, based on the total weight of the composition, preferably from about 0.5% by weight to about 2% by weight, and more preferably Excellent results were obtained from about 0.7% by weight to about 1.8% by weight.

Freely available ingredients

The composition of the present invention may contain other ingredients than those listed above. In particular, the polymer composition may further comprise at least one reinforcing filler.

Reinforcing fillers are well known to those skilled in the art and can be incorporated into the compositions according to the invention. They are preferably selected from fibrous fillers and particulate fillers. More preferably, the reinforcing filler is selected from the group consisting of mineral fillers (such as talc, mica, kaolin, calcium carbonate, calcium citrate, magnesium carbonate), glass fibers, carbon fibers, synthetic polymer fibers, and aromatic polyamide fibers. , aluminum fiber, titanium fiber, magnesium fiber, boron carbide fiber, rock wool fiber, steel fiber, ash stone, and the like. Still more preferably, it is selected from the group consisting of talc, mica, kaolin, calcium silicate, magnesium carbonate, glass fiber, carbon fiber and apatite. Even more preferably, the reinforcing filler is selected from the group consisting of glass fibers, limestone, carbon fibers, talc, mica and kaolin.

A particular type of fibrous filler consists of whiskers, i.e., single crystal fibers made of different raw materials such as Al ₂ O ₃ , SiC, BC, Fe, and Ni. Among the fibrous fillers, glass fibers are preferred; they include chopped strands of A-, E-, C-, D-, S- and R-fibers, as in the Handbook of Plastic Additives by John Murphy. The second edition ( Additives for Plastics Handbook , 2nd ed., John Murph) is described in Chapter 5.2.3, pp. 43-48. Preferably, the filler is selected from the group consisting of fibrous fillers.

In a preferred embodiment of the invention, the reinforcing filler is selected from the group consisting of limestone and glass fibers. Excellent structure is obtained when using limestone and/or glass fibers. Glass fibers have a circular or elliptical cross section (also known as flat fibers).

If present, the reinforcing filler is preferably present in an amount of at least 2% by weight, more preferably at least 4% by weight, still more preferably at least 5% by weight and most preferably based on the total weight of the composition according to the invention. Preferably, it is at least 10% by weight. When present, the reinforcing filler is preferably present in an amount of up to 40% by weight, more preferably up to 30% by weight, still more preferably up to 25% by weight, based on the total weight of the composition according to the invention. The best is up to 20% by weight.

When the reinforcing filler is present in the composition in an amount of from about 5% by weight to about 40% by weight, based on the total weight of the composition, preferably from about 5% by weight to about 25% by weight, and more preferably Excellent results were obtained from about 10% by weight to about 20% by weight.

The polymer composition according to the invention may also comprise at least one white pigment different from the reinforcing fillers defined above.

The white pigment is preferably selected from the group consisting of TiO ₂ , ZnS ₂ , ZnO, and BaSO ₄ .

The white pigment is advantageously in the form of particles preferably having a weight average size (equivalent diameter) of less than 5 μm. Larger size can adversely affect this The characteristics of the composition. Preferably, the particles have a weight average size of less than 1 μm. Further, it is preferably higher than 0.1 μm.

The shape of the particles is not particularly limited; they may notably be round, flake, flat, and the like.

The white pigment is preferably titanium dioxide (TiO ₂ ). The form of titanium dioxide is not particularly limited and a wide variety of crystalline forms such as anatase form, rutile form, and monoclinic type may be used. However, the rutile form is preferred because of its higher refractive index and superior light stability. Titanium dioxide can be treated with or without a surface treatment agent. Preferably, the titanium oxide has an average particle diameter in the range of 0.15 μm to 0.35 μm.

The surface of the titanium dioxide particles is preferably coated. Titanium dioxide will preferably be first coated with an inorganic coating and then coated with an organic coating which is applied to the inorganic coating. The titanium dioxide particles can be coated using any method known in the art. Preferred inorganic coatings include metal oxides. The organic coating may include one or more of a carboxylic acid, a polyol, an alkanolamine, and/or a hydrazine compound.

If present, the white pigment is preferably present in an amount of at least 1% by weight, preferably at least 6% by weight, more preferably at least 8% by weight, even more preferably at least, based on the total weight of the composition. 10% by weight, and most preferably at least 15% by weight. Further, when present, the white pigment is preferably present in an amount of up to 50% by weight, preferably up to 40% by weight, more preferably up to 35% by weight, based on the total weight of the composition according to the invention. Even better, up to 30% by weight, and optimally up to 25 weight%.

Excellent results are obtained when the amount of titanium dioxide is from 10% by weight to 30% by weight, based on the total weight of the composition, preferably from 15% by weight to 25% by weight.

The compositions may also optionally contain up to about 15% by weight of one or more polymeric toughening agents. The toughening agent is typically a lower melting point (generally less than 200 ° C, preferably less than 150 ° C) and attached to a functional group that can react with the polyester (and other polymers that may optionally be present) An elastomer. Since the carboxyl group and the hydroxyl group are usually present in the polyester, the toughening agent is generally selected from those containing a functional group capable of reacting with a carboxyl group and/or a hydroxyl group. Examples of such functional groups include epoxy, carboxylic anhydride, hydroxy (alcohol), carboxyl, and isocyanate. Preferred functional groups are epoxys and carboxylic anhydrides; epoxy systems are especially preferred. Such functional groups are usually obtained by grafting a small molecule onto an already existing polymer or by copolymerizing a monomer having a desired functional group when the molecular system of the polymer toughening agent is formed by copolymerization. Attached to the polymeric toughening agent. As an example of grafting, maleic anhydride can be grafted onto the hydrocarbon rubber using a free radical grafting technique. The resulting graft polymer has a carboxylic anhydride and/or a carboxyl group attached thereto.

The compositions according to the invention may also optionally contain up to about 5% of at least one nucleating agent. Non-limiting examples of nucleating agents include sodium benzoate and structures derived therefrom, linear alcohols having from 30 to 50 carbon atoms, talc, boron nitride, and LCP.

The compositions may optionally further comprise up to about 3% by weight UV stabilizer or UV blocker. Examples include triazoles and triazines, oxalic anilides, hydroxybenzophenones, benzoates, and alpha-cyanoacrylates. When present, the UV stabilizer is preferably present in an amount of from about 0.1% to about 3% by weight, or preferably from about 0.1% to about 1% by weight, or more preferably, based on the total weight of the composition. It is from about 0.1% by weight to about 0.6% by weight. The composition according to the invention is a melt-blended blend in which all of the polymeric components are well dispersed in each other and all of the non-polymeric components are well dispersed in the polymer matrix and Delimited so that the blend forms a uniform whole.

The composition according to the invention may also comprise other polymers than the abovementioned polyesters, such as polycarbonate, polyethylene glycol, polyfluorene, PEEK and polyphthalamide.

The compositions according to the invention may also comprise other optional ingredients such as mold release agents, plasticizers, lubricants, and other stabilizers other than those described above.

Any of the melt mixing methods can be used to combine the polymeric component of the present invention with the non-polymeric component. For example, the polymeric component and the non-polymeric component may be added to a melt mixer, such as a single screw or twin screw extruder, a blender, a kneader, or an internal mixer, by a single addition step. Add all at once, or in a batchwise manner, and then melt mix. When the polymeric component and the non-polymeric component are added in a batchwise manner, a part of the polymeric component and/or the non-polymeric component is first added and melt-mixed with the remaining polymeric component. And then the non-polymeric ingredients are added and further melt mixed until a well mixed group is obtained Compound.

Another aspect of the invention relates to an article comprising the above polymer composition and in particular to a portion of an LED device.

As used herein, the terms "light emitting diode device" and "LED device" are intended to mean an electrical connector comprising at least one light emitting diode, capable of connecting the diode to an electrical circuit, and partially surrounding the A device for the outer casing of a diode. The LED device can optionally have a lens that completely or partially covers the LED.

Articles made from the compositions according to the present invention may be formed from the compositions of the present invention by any suitable melt processing method known to those skilled in the art, such as injection molding or the like.

The article of the invention is preferably part of an LED device, such as a housing, a reflector and a reflector plate.

The articles can be overmolded onto a metal (e.g., copper or silver coated copper) leadframe that can be used to electrically connect the LEDs that are inserted into the housing. Preferably, the article has a cavity in the portion of the outer casing surrounding the LED for reflecting the LED light in an outward direction and toward the lens (if a lens is present). The cavity is formed into a cylindrical, conical, parabolic or other curved form and preferably has a smooth surface. Alternatively, the walls of the cavity may be parallel or substantially parallel to the diode. A lens can be formed over the cavity of the diode and can include an epoxy or tantalum material.

The articles of the present invention can be incorporated into LED devices for use in a variety of applications, such as traffic signals, large-area display screens (including shadows) Like display screens, image screens, interior and exterior lighting, cell phone display back lights, car display screens, vehicle brake lights, vehicle headlights, laptop display back lights, sidewalk lighting, and flash.

Instance

The disclosure is now presented by way of example, and is not intended to limit the scope of the disclosure.

Use the following commercially available materials:

Polyester: PCT polyester glass fiber from Eastman ^TM Chemical Products :

Fiberglass-1: OCV 995 from OCV ^TM Reinforcements

Fiberglass-2: OCV 952A from Owens Corning Composites

Glass fiber-3: T-127H from NEG (Nippon Electric Glass Co., Ltd.)

Titanium dioxide:

TiO ₂ -1: Ti-Pure ^® R-350 available from DuPont Titanium Technologies - rutile TiO ₂ produced by the chloride process, treated with vermiculite and alumina.

TiO ₂ -2: Tipaque ^® PC-3- available from Ishihara Sangyo Kaisha, Ltd. - rutile TiO ₂ produced by the chloride process, treated with vermiculite and alumina.

Stabilizers and additives:

Phosphorus compound 1 (PC-1): ULTRANOX ^® 626 phosphite stabilizer - (2,4-ditributylphenyl) pentaerythritol diphosphite, the chemical formula is as detailed above (α5), from the family Chemtura is commercially available.

Phosphorus Compound 2 (PC-2): IRGAFOS ^® P-EPQ phosphite stabilizer - tetrakis(2,4-indolyl butylphenyl)[1,1-biphenyl]-4,4' Dikisodisphosphite, which has the chemical formula (β1) as detailed above, is commercially available from Ciba.

Hindered amines: NYLOSTAB ^® S-EED stabilizers correspond to hindered amines of formula (α2) and are commercially available from Clariant Corp.

Talc: available from a company by ratio-meter (Imi Fabi LLC) Imi-Fabi TM HTP-4.

LLDPE: Linear low density polyethylene GRSN-9820 NT 7 commercially available from Dow Corporation (DOW).

General procedure for preparing such compositions

The polyester resin described above was charged into a first barrel of a ZSK-26 twin-screw extruder containing 12 zones via a weight loss feeder. The set point temperature of the barrel is in the range of 240 ° C - 300 ° C and the resin is melted before the 5th zone. In the 5th zone, the other components are fed to the filler via a side by a weight loss feeder. Screw speed is 175 Rpm. The extrudate was allowed to cool and granulated using conventional equipment.

The nature and amount of the respective ingredients used are summarized in Table 5, and the amount of each ingredient is indicated by weight percentage.

Reflectance measurement

An analogy to the behavior of a component made from the composition of the present invention in an LED device is by exposing the sample to light at 180 ° C for 12 days. Thus, each of the compositions of Example E4 and Comparative Examples CE1-CE3 was used to prepare discs having a diameter of about 50 mm and a thickness of about 1.6 mm.

The disks on an oven at 180 ℃ equipped with a lamp for 12 days, the lamp comprises a lamp 400W UV F / 2 and Optivex ^TM UV filter. The reflectance was measured with a BKY-Gardner spectrometer. The reflectance results on the as-received disc and on the disc after 12 days of exposure to light and high heat (180 ° C) are summarized in Table 6, as well as the percent retention of reflectance at 460 nm. .

result

The compositions of E6 and E7 according to the present invention unexpectedly show higher reflectance retention rates after molding as well as after 12 days of exposure to light and high heat compared to Comparative Examples CE1 to CE5.

The data summarized in Table 6 is a good demonstration of the synergistic effect observed between phosphite compounds such as Ultranox ^® 626 or Irgafos ^® P-EPQ and hindered amine compounds such as Nylostab ^® S-EED. The composition according to the present invention achieves excellent optical properties on the as-molded article and on the same article that has been subjected to light and heat treatment, which is intended to simulate that the material may be exposed during the manufacture of the LED device. The conditions therein.

Comparative Examples CE1 and CE3 provide evidence that the individual phosphorus compounds are insufficient to provide excellent optical properties obtained with the examples according to the present invention.

Comparative Examples CE2 and CE5 clearly show that the presence of only hindered amine compounds is not effective in providing the composition with sufficient stability over long-term (12 days) exposure to light and high heat (180 °C).

Examples E6 and E7 combine a phosphorus compound (ULTRANOX ^® 626 stabilizer or IRGAFOS ^® P-EPQ) and a hindered amine compound (Nylostab ^® S-EED) to achieve reflectance retention after light and high heat exposure. Unexpected results. This result will be obtained even if the total amount of additive is used compared to the amount used in CE1 and CE3.

Examples E6 and E7 according to the present invention meet the various requirements previously set forth (notably good processability, high dimensional stability, high mechanical strength) and also unexpectedly have the following characteristics: in light and heat treatment The post-reflectance is greater than 62%. These compositions are therefore excellent candidates for the manufacture of LED components.

Claims (10)

A polymer composition comprising: at least one polyester; at least one hindered amine compound; and at least one phosphorus compound selected from the group consisting of phosphites, phosphonites ( Phosphonites) and mixtures thereof, wherein the at least one phosphorus compound is present in an amount from 0.7% to 5% by weight, based on the total weight of the composition. The polymer composition of claim 1, wherein at least 50 mole % of the repeating unit of the polyester is obtained by polycondensation of terephthalic acid with 1,4-cyclohexane dimethanol. The polymer composition of claim 2, wherein the polyester is poly(1,4-cyclohexyldimethyl terephthalate). The polymer composition of claim 1, wherein the at least one hindered amine compound is present in an amount of from 0.05% by weight to 2% by weight based on the total weight of the composition. The polymer composition of claim 1, wherein it further comprises at least one white pigment. The polymer composition of claim 5, wherein the white pigment is selected from the group consisting of TiO ₂ , ZnS ₂ , ZnO, and BaSO ₄ . The polymer composition of claim 1, wherein it further comprises at least one reinforcing filler. Such as the polymer composition of claim 7 of the patent scope, wherein the increase The strong filler is selected from the group consisting of glass fiber, ash stone, carbon fiber, talc, mica and kaolin. An article comprising the polymer composition of claim 1 of the patent application. An article of claim 9, wherein the article is part of an LED device.