Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
  • C08K5/51—Phosphorus bound to oxygen
  • C08K5/52—Phosphorus bound to oxygen only
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
  • C08L71/08—Polyethers derived from hydroxy compounds or from their metallic derivatives
  • C08L71/10—Polyethers derived from hydroxy compounds or from their metallic derivatives from phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L73/00—Compositions of macromolecular compounds obtained by reactions forming a linkage containing oxygen or oxygen and carbon in the main chain, not provided for in groups C08L59/00 - C08L71/00; Compositions of derivatives of such polymers
  • C08L73/02—Polyanhydrides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes

Definitions

• plastic articles may be used as a reflector for a light source.
• the reflector may be designed to reflect light in a certain direction or in all directions.
• Highly reflective articles may also have usefulness to produce signs.
• the reflective material may be used to accentuate a word, phrase or symbol appearing on the sign.
• the sign may include a light source that is
• Highly reflective polymer materials may also be well suited for use in labels to accentuate the printed matter on the label or design appearing on the label.
• Molded polymer articles having highly reflective properties may also be desirable in applications where the reflective properties may improve the aesthetic appeal of the product.
• trim pieces having highly reflective properties may be well suited for use in consumer appliance products, in trim pieces and bezels for automobile interiors and for trim pieces for various other consumer products.
• Molded polymer articles having good reflective properties may also be used as reflectors for light-emitting diodes.
• Light-emitting diodes commonly called LEDs
• LEDs continue to increase in popularity as a light source for use in many and diverse applications. LEDs, for example, are displacing incandescent and other light sources in many uses and have found applications, for instance, as traffic signals, large area displays, interior and exterior lighting, cellular telephone displays, digital clock displays, displays for consumer appliances, flashlights, and the like.
• the reflector for the LED can also serve as the housing for the LED and is typically made from a molded polymeric resin.
• the polymeric resin can be injection molded to form the housing and reflector.
• the polymeric resin is injection molded over a lead frame for integrating the lead frame into the LED assembly.
• the LED element located within the reflector can be sealed by a translucent or transparent resin.
• the transparent or translucent resin may serve as a lens for further enhancing the light that is emitted.
• PCT composition
• the present disclosure is generally directed to further improvements in formulating polymer compositions that have a desirable combination of properties, such as reflectance and strength, when molded into various different articles.
• the present disclosure is directed to a polymer composition and to molded articles made from the composition.
• the polymer composition generally contains a thermoplastic polymer combined with one or more
• the different components can include a pigment, such as a white pigment, a reactive modifier, a reinforcing agent such as glass fibers, an optical brightener, an impact modifier, a lubricant, a thermal stabilizer, an oxidative stabilizer, and/or an ultraviolet light stabilizer.
• a pigment such as a white pigment
• a reactive modifier such as glass fibers
• a reinforcing agent such as glass fibers
• an optical brightener such as glass fibers
• an impact modifier such as glass fibers
• a lubricant such as glass fibers
• thermal stabilizer such as an optical brightener
• an lubricant such as glass fibers
• thermal stabilizer such as glass fibers
• an oxidative stabilizer such as a thermal stabilizer
• an oxidative stabilizer such as an ultraviolet light stabilizer.
• the different components can be blended with the thermoplastic polymer in a manner to produce molded articles having desired characteristics.
• the composition can be formulated such that the resulting molded article may have
• composition can also be formulated so as to be well suited for bonding with silicone polymers.
• the polymer composition may have excellent reflectance properties.
• the polymer composition can have an initial reflectance at 460 nm of greater than about 90%, such as greater than about 93%, such as greater than about 95%.
• the initial reflectance at 460 nm is generally less than 100%.
• the polymeric material can also have an initial whiteness index of greater than about 84, such as greater than about 92, such as greater than about 95.
• the polymeric material can have a whiteness index after aging at 200°C for four hours of greater than about 50, such as greater than about 60, such as greater than about 62, such as greater than about 65, such as greater than about 68, such as even greater than about 70.
• the whiteness index after aging at 200°C is less than the initial whiteness index of the material and is generally less than about 95.
• the polymer composition can also have a whiteness index retention after aging at 200°C for four hours of greater than about 60%, such as greater than about 65%, such as greater than about 70%, such as even greater than about 75%.
• the polymer composition may be formulated so as to have excellent mechanical properties.
• the polymer composition can have a notched Charpy impact strength of greater than about 2 kJ/m 2 , such as greater than about 2.5 kJ/m 2 .
• the polymer composition can also be formulated so as to have good silicone bond strength.
• the polymer composition can have a silicone bond strength according to a Lap- Shear Test of greater than about 25 Ibf.
• the polymer composition contains a thermoplastic polymer, such as a thermoplastic polymer having a melting point greater than about 260°C.
• the thermoplastic polymer may comprise a polyester polymer including liquid crystal polymers, a fluorocarbon polymer, a polyamide polymer, and the like.
• the thermoplastic polymer comprises poly(1 ,4- cyclohexanedimenthanol terephthalate).
• the polymer composition may optionally contain various other components.
• the polymer composition may contain a pigment, such as a white pigment.
• the white pigment may be present in an amount greater than about 10% by weight, especially in applications where reflectance properties are important.
• the reinforcing agent may comprise fibers or an inorganic filler.
• the composition contains glass fibers in an amount from about 10% to about 30% by weight.
• Another optional component that may be present in the polymer composition is a reactive modifier. The reactive modifier reacts with the
• the reactive modifier may serve as a chain extender that may stabilize the polymer during melt processing or may improve the light stable characteristics of the polymer.
• the polymer composition may also optionally contain one or more impact modifiers.
• the impact modifiers may react with the thermoplastic polymer or be non-reactive.
• the polymeric material contains a terpolymer of ethylene, methyl acrylate and glycidyl (meth) acrylate.
• the polymeric material contains an ethylene-(methyl)acrylate copolymer.
• the polymeric material may include a combination of the terpolymer of ethylene, methyl acrylate and glycidyl (meth) acrylate and an ethylene-(methyl)acrylate copolymer.
• the polymer composition may contain a stabilizer.
• the stabilizer may comprise an
• organophosphorus compound such as a phosphonate stabilizer or a phosphate stabilizer.
• Figure 1 is a perspective view of one embodiment of an LED assembly made in accordance with the present disclosure
• Figure 2 is a plan view of the LED assembly illustrated in Figure 1 ;
• FIG. 3 is a perspective view of another embodiment of an LED assembly made in accordance with the present disclosure.
• Figure 4 is a perspective view of one-half of a mold used for measuring spiral flow length.
• Figure 5 is a perspective view of a sample constructed in order to measure silicone bond strength according to a Lap-Shear Test.
• the present disclosure is directed to a polymer composition and to articles made from the composition that can exhibit various properties that relate to reflectance, whiteness, flow properties during melt processing and/or mechanical properties such as impact strength.
• the composition of the present disclosure can be used in numerous and different end use applications.
• the composition can be used as a reflector for light.
• the polymer composition may be used to produce a reflector for LED assemblies, may be used as a component in a sign, such as a lighted sign, may be used as a label, or in any other suitable application where excellent reflectance properties may be desired.
• the polymer composition can be used to mold various other polymer articles.
• Such polymer articles may include parts for consumer products, such as consumer appliances, automobile parts, including trim pieces and bezels for the interior of an automobile or for the exterior of an automobile, and the like.
• the polymer composition of the present disclosure has excellent reflective properties, the polymer composition may be selected for use in various applications where reflective properties are not needed. In these applications, the polymer composition may be selected due to its melt flow properties, strength properties, impact resistant properties, or the like.
• the polymer composition of the present disclosure can contain different ingredients and components in different amounts in order to produce a formulation that is well suited for a particular end use application.
• the polymer composition contains a thermoplastic polymer in combination with various optional components.
• One or more of the optional components can be combined together in a manner that optimizes certain desired properties. For example, where reflectance properties are needed, one or more pigments may be combined with the polymer composition. If reflectance properties, however, are not important in a particular application, the one or more pigments may be eliminated from the formulation and/or used in minor amounts.
• the polymer composition contains at least one thermoplastic polymer, and particularly at least one high temperature thermoplastic polymer.
• the thermoplastic polymer can have a melt temperature of greater than about 260°C, such as greater than about 270°C, such as greater than about 280°C, such as greater than about 290°C.
• the thermoplastic polymer can have a melt temperature of less than about 500°C, such as less than about 400°C, such as less than about 350°C.
• the thermoplastic polymer comprises a polyester polymer, such as a poly(1 ,4-cyclohexanedimethanol terephthalate) polymer, a liquid crystal polymer, a polyamide polymer, a fluorocarbon polymer, or mixtures thereof.
• a polyester polymer such as a poly(1 ,4-cyclohexanedimethanol terephthalate) polymer, a liquid crystal polymer, a polyamide polymer, a fluorocarbon polymer, or mixtures thereof.
• the polymer composition may contain a pigment, such as a white pigment.
• the composition can also contain a reinforcing agent, such as a filler or reinforcing fibers.
• the composition may further contain one or more reactive modifiers.
• the one or more reactive modifiers may comprise polymers that react with a thermoplastic polymer in order to provide one or more benefits. Of particular advantage, reactive modifiers may be selected that do not cause unwanted yellowing of the
• composition during later use, especially when the composition is used as a reflector for a light source.
• the composition may also be formulated so as to exclude additives and stabilizers that may cause yellowing to occur.
• the composition is free from some or all of any aromatic epoxy resins, and is especially free of a novolac epoxy resin.
• the polymer composition of the present disclosure can be formulated so as to have excellent melt flow properties.
• the polymer composition can have a spiral flow length of at least five inches, such as at least six inches, such as even at least seven inches.
• the spiral flow length is less than about fifteen inches, such as less than about twelve inches.
• the spiral flow length is determined at a temperature of 305°C and at a mold temperature of 120°C. Spiral flow length is measured by injecting the polymer composition into a mold as shown in Fig. 4 (one-half of mold shown). The mold cavity is 1/32 inches thick (high) and 1/2 inches wide.
• the polymer composition is injected into the mold using a 32 mm extruder at an injection speed of 4 inches per second and a shot size of 1.8 inches.
• Spiral flow length generally indicates the flow characteristics of the polymer composition when being melt processed.
• Higher spiral flow lengths indicate the ability of the material to uniformly and evenly flow into a mold, which also indicates the ability of the material to fill any interstices of the mold that may exist.
• a higher spiral flow length is particularly preferred when molding small parts that may have complex three-dimensional configurations, such as reflectors and housings for LED assemblies.
• polymer compositions made according to the present disclosure can also be formulated so as to have a stable viscosity.
• the melt viscosity of the composition during processing may not fluctuate by more than about 5%, such as no more than about 3%.
• the polymer composition of the present disclosure also has a relatively high initial reflectance, and excellent reflectance stability. For instance, once molded into an article, the polymer composition of the present disclosure can have an initial reflectance at 460 nm of greater than about 90%, such as greater than about 93%, such as greater than about 95%. Reflectance is measured according to ASTM Test Method 1331 using a spectracolormeter. During testing, a CIE D65 daylight illuminant is used at an angle of 10°.
• polymer articles made according to the present disclosure can also have a relatively high initial whiteness index.
• Whiteness index can be measured according to Wl E313.
• Articles made according to the present disclosure can have an initial whiteness index of greater than about 80, such as greater than about 90, such as greater than about 92, such as greater than about 95.
• articles made according to the present disclosure also have great reflectance stability properties.
• the whiteness index of articles made according to the present disclosure can be at least about 50, such as at least about 60, such as at least about 70, such as at least about 72, such as at least about 74, such as even greater than about 75.
• the whiteness index after aging is lower than the initial whiteness index.
• the reflectance stability properties of articles made according to the present disclosure can also be measured by percent retention of its whiteness index after aging at 200°C for four hours.
• a percent whiteness index retention after thermal aging of greater than about 60%, such as greater than about 65%, such as greater than about 70%, such as even greater than about 75%.
• the percent retention is generally less than about 95%.
• the polymer composition can be formulated such that polymer articles made from the composition absorb light in the ultraviolet and violet region of the electromagnetic spectrum, which may be between about 300 nanometers ("nm") and about 400 nm, and re-emit light in the blue region, which may be between about 410 nm and about 470 nm.
• nm nanometers
• blue region which may be between about 410 nm and about 470 nm.
• the polymer composition of the present disclosure also has good reflow resistance properties at relatively high temperatures, such as at temperatures around 260°C.
• the polymer material has good silicone adhesion properties, which may be important in applications where an adhesive is used to either attach components in an LED assembly to the reflector or to attach the reflector to a substrate.
• Articles made according to the present disclosure also have good mechanical properties, such as good impact resistance.
• the material of the present disclosure can also display low moisture absorption.
• the polymer composition of the present disclosure may be used in numerous applications.
• the polymer composition is formulated to have good reflective properties, for instance, the polymer
• the polymer composition can be used to produce reflectors for a light source.
• the polymer composition can be used to produce a reflector for an LED assembly.
• the LED assembly 10 is considered a side view LED.
• the LED assembly 10 includes a light-emitting diode 12 that is configured to emit light when a current is fed through the device.
• the light- emitting diode 12 may be comprised of a semiconductor chip including multiple layers of materials.
• the LED 12 generally includes an n-type material layer and a p-type material layer, which form a p-n junction that can be connected to a voltage source.
• the p-type layer may comprise doped gallium aluminum arsenide
• the n-type layer may comprise doped gallium arsenide.
• the LED 12 is connected to a first bonding wire 14 and to a second bonding wire 16.
• the bonding wires 14 and 16 are connected to a lead frame 18.
• the lead frame 18 includes a first lead frame portion 20 and a second lead frame portion 22.
• the lead frame 18 may include or be connected to an anode 24 and a cathode 26 which may also be considered a first terminal 24 and a second terminal 26.
• the LED assembly 10 further includes a reflector 28 which can also serve as the housing for the LED assembly.
• the reflector 28 in accordance with the present disclosure, is made from a polymer composition having excellent reflectance properties.
• the reflector 28 defines a cavity 30 in which the LED 12 is located.
• the walls of the cavity 30 generally surround the LED 12 and, in the embodiment illustrated, have a depth sufficient for the LED 12 to be recessed within the cavity.
• the cavity 30 of the reflector 28 surrounds the LED 12 and serves to reflect light being emitted by the LED in an outward direction.
• the cavity 30 may have any suitable shape.
• the cavity 30 may be cylindrical, conical, parabolic, or any other suitable curved form.
• the walls of the cavity 30 may be parallel, substantially parallel, or tapered with respect to the diode 12.
• the cavity 30 has a smooth surface and is comprised of side walls 32 and 34 and end walls 36 and 38.
• the side walls 32 and 34 taper in an outward direction from the LED 12.
• the end walls 36 and 38 can be substantially parallel or may also taper outwardly from the LED source.
• the cavity 30 of the reflector 28 may be filled with a clear material, such as a transparent material or a translucent material.
• the cavity 30 may be filled with an epoxy or a silicone material.
• the material used to fill the cavity 30 may act as a lens for the light being emitted by the LED 12.
• FIG. 3 another embodiment of an LED assembly 50 that may be made in accordance with the present disclosure is shown.
• a top view LED assembly is shown.
• the top view LED assembly 50 is similar in construction to the side view LED assembly 10 illustrated in Figs. 1 and 2.
• the top view LED assembly 50 includes an LED 52 that is positioned towards the bottom of a cavity 54 of a reflector 56.
• the LED 52 is also connected to a lead frame 58.
• the cavity 54 of the reflector 56 is filled with a clear material 60.
• LED assemblies as shown in Figs. 1-3 generally have relatively small dimensions.
• the LED assemblies typically have a greatest dimension (such as height, width, depth or diameter) that is generally less than about 10 mm, such as typically less than about 8 mm.
• the LED assemblies typically include at least one dimension, such as depth, that is less than 5 mm, such as less than 2 mm, such as even less than 1 mm.
• the polymer composition of the present disclosure is capable of forming reflectors for LED assemblies using melt flow processing techniques.
• the polymer composition of the present disclosure is blow molded in forming the reflectors.
• the composition of the present disclosure is formulated so as to have melt flow properties capable of forming hundreds of reflectors simultaneously.
• the polymer composition of the present disclosure contains a high temperature thermoplastic polymer.
• the thermoplastic polymer for instance, can have a melting point of at least 260°C.
• Various different thermoplastic polymers may be used in accordance with the present disclosure including mixtures of thermoplastic polymers.
• the thermoplastic polymer comprises a poly(1 ,4-cyclohexanedimethanol terephthalate) polymer, which is typically referred to as a "PCT" polymer.
• Poly(1 ,4- cyclohexanedimethanol terephthalate) is a polyester that contains repeat units from a dicarboxylic acid component and a glycol component. At least about 80 mol percent, more preferably at least about 90 mol percent, and especially preferably all of the diol repeat units are derived from 1 ,4-cyclohexanedimethanol and are of formula (I).
• At least about 80 mol percent, more preferably at least about 90 mol percent, and especially preferably all of the dicarboxylic acid repeat units are derived from terephthalic acid and are of formula (II).
• the PCT polymer contains 100 mol percent of terephthalic acid or diesters.
• the glycol component on the other hand, can contain a total of 100 mol percent 1 ,4-cyclohexanedimethanol.
• the dicarboxylic acid component may contain up to 10 mol percent of other aromatic, aliphatic, or alicyclic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid,
• cyclohexanedicarboxylic acid succinic acid, subacic acid, adipic acid, glutaric acid, azelaic acid, and the like.
• the glycol component may also contain up to about 10 mol percent of other aliphatic or alicyclic glycols, such as diethylene glycol, triethylene glycol, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and the like.
• the PCT polymer can have an inherent viscosity (I.V.) of from about 0.3 to about 1 .5 and a melting point of at least 260°C.
• the PCT polymer can comprise a blend of two or more different grades of PCT polymers.
• a blend such as a 1 :1 blend, of high I.V. PCT polymer with a low I.V. PCT polymer may be used.
• a blend such as a 2:1 blend, may be used that includes a PCT polymer wherein the dicarboxylic acid component is 100 mol percent terephthalic acid and a PCT polymer in which the dicarboxylic acid component is 90 mol percent terephthalic acid and 10 mol percent isophthalic acid.
• the PCT polymer is present in the composition in an amount of at least about 20% by weight, such as in an amount of at least 30% by weight, such as in an amount of at least 40% by weight, such as in an amount of at least about 50% by weight, such as in an amount of at least about 60% by weight.
• the PCT polymer is generally present in an amount less than about 80% by weight, such as in an amount less than about 70% by weight. In one embodiment, the PCT polymer is present in an amount from about 20% by weight to about 60% by weight.
• the thermoplastic polymer may comprise various other polymers.
• any suitable thermoplastic polymer may be used in accordance with the present disclosure.
• the melting point of the polymer for instance, can be greater than about 260°C, such as greater than about 270°C, such as greater than about 280°C, such as even greater than about 290°C.
• the melting point of the thermoplastic polymer can generally be less than about 500°C, such as less than about 400°C, such as less than about 350°C.
• Thermoplastic polymers that may be used in accordance with the present disclosure in addition to PCT polymers include polyether ether ketone polymers, other polyester polymers such as polybutylene terephthalate and polyethylene terephthalate.
• a polybutylene terephthalate polymer and/or a polyethylene terephthalate polymer are used that have a high degree of crystallinity.
• Other thermoplastic polymers that may be used include polytrimethylene terephthalate and liquid crystal polymers, such as liquid crystal polyester polymers.
• Still other thermoplastic polymers that may be used include high temperature polyamide polymers. Such polymers may include, for instance, nylon 66, nylon 3, nylon 4, nylon 5, nylon 46, and the like.
• Polytetrafluoroethylene polymers and fluorinated ethylene polymers are also well suited for use in the present disclosure.
• Further thermoplastic polymers that may be used include ethylene-carbon monoxide polymers, styrene acrylonitrile polymers, and styrene maleic anhydride polymers.
• the composition may also contain one or more of various other components.
• the composition may contain at least one pigment, such as a white pigment.
• the at least one white pigment may be present in amounts greater than about 10% by weight, such as in amounts of at least about 15% by weight.
• the white pigment is present in the composition in an amount sufficient to increase the reflectance of articles molded from the composition.
• White pigments that may be included in the composition include titanium dioxide, zinc oxide, white lead, aluminum oxide, barium sulfate, and the like.
• the white pigment comprises titanium dioxide.
• the titanium dioxide may be any sort, such as a rutile titanium dioxide.
• the titanium dioxide particles can have any suitable shape, such as spherical particles or elliptic particles.
• the titanium dioxide powder can be comprised of particles having a diameter of from about 10 nm to about 20,000 nm, such as from about 150 nm to about 500 nm.
• the titanium dioxide particles can be coated.
• the titanium dioxide particles can be first coated with an inorganic coating and then optionally with an organic coating that is applied over the inorganic coating.
• Inorganic coatings that may be used include metal oxides.
• Organic coatings may include carboxylic acids, polyols, alkanolamines, and/or silicon compounds.
• Examples of carboxylic acids suitable for use as an organic coating include adipic acid, terephthalic acid, lauric acid, myristic acid, palmitic acid, stearic acid, polyhydroxystearic acid, oleic acid, salicylic acid, malic acid, and maleic acid.
• the term "carboxylic acid” includes the esters and salts of the carboxylic acids.
• Examples of silicon compounds suitable for an organic coating include, but are not limited to, silicates, organic silanes, and organic siloxanes, including organoalkoxysilanes, aminosilanes, epoxysilanes, mercaptosilanes, and
• Suitable silanes can have the formula R x Si(R')4 -x wherein R is a nonhydrolyzable aliphatic, cycloaliphatic, or aromatic group having from 1 to about 20 carbon atoms, and R' is one or more hydrolyzable groups such as an alkoxy, halogen, acetoxy, or hydroxy group, and X is 1 , 2, or 3.
• Useful suitable silanes suitable for an organic coating include one or more of hexyltrimethoxysilane, octyltriethoxysilane, nonyltriethoxysilane, decyitriethoxysilane, dodecyltriethoxysilane, tridecyltriethoxysilane,
• R has between 8 and 18 carbon atoms and R' is one or more of chloro, methoxy, ethoxy, or hydroxy groups.
• the white pigment comprises Type II chalk resistance particles as classified according to AST Test D476.
• the white pigment comprises particles, such as metal oxide particles, that include a surface treatment that produces the chalk resistance properties.
• the particles for instance, may comprise rutile titanium dioxide.
• the above white pigment particles may maximize the increase in initial reflectance of the resulting polymeric material while minimizing the impact the particles have on the melt viscosity of the material.
• the surface treatment on the white pigment can vary as long as the particles have the required chalk resistance characteristics.
• the white pigment comprises titanium dioxide particles that include a surface treatment containing alumina.
• the surface treatment may comprise alumina alone or in combination with other components.
• the surface treatment comprises a combination of alumina and a polysiloxane.
• the white pigment may, overall, have a neutral tint or have a blue tint.
• the particles are slightly basic when combined with distilled water and measured for pH.
• the white pigment particles may exhibit a pH of greater than about 7, such as greater than about 7.5.
• the pH of the particles is generally less than about 9, such as less than about 8.5.
• the polymer composition of the present disclosure can also optionally contain one or more reinforcing agents, such as fillers and fibers.
• reinforcing agents such as fillers and fibers.
• Such materials can include, for instance, glass fibers, wollastonite, potassium titanate, calcium carbonate, talc, mica, silica, kaolin, and the like.
• inorganic fillers may be present in the composition in an amount from about 1 % to about 40% by weight, such as in an amount from about 10% to about 30% by weight.
• the composition may further optionally contain one or more reactive modifiers, which may serve as stabilizers.
• the reactive modifiers may comprise a material, such as a polymer, that is capable of reacting with the thermoplastic polymer, such as the PCT polymer.
• the reactive modifier may provide one or more benefits.
• the reactive modifier may compatabilize the thermoplastic polymer with any other components present, especially during melt processing.
• the reactive modifier comprises a material that can react with carboxyl or hydroxyl end groups on the thermoplastic polymer. In this manner, the reactive modifier may act as a chain extender.
• the reactive modifier comprises a compound, oligomer, or polymer with one or more functional groups.
• the one or more functional groups are available for reaction with the thermoplastic polymer contained in the composition.
• Functional groups that may be present on the reactive modifier include epoxy groups, carboxylic anhydride groups, hydroxyl groups, carboxyl groups, and/or isocyanate groups.
• the reactive modifier comprises a chain extender that attaches to the thermoplastic polymer.
• Reactive modifiers that may be used in accordance with the present disclosure generally include phenoxy resins and/or epoxy resins, such as non- aromatic epoxy resins.
• the reactive modifier comprises a modified phenoxy resin that is capable of reacting with the thermoplastic polymer.
• the phenoxy resin for instance, may include hydroxyl functionality.
• the phenoxy resin for instance, may have a glass transition temperature of less than about 120°C, such as less than about 1 10°C, such as less than about 100°C.
• the phenoxy resin may have a viscosity when tested in cyclohexanone at 25% NV of less than about 2500 cP, such as less than about 2300 cP.
• Non-aromatic epoxy resins that may be used as the reactive modifier include 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexene carboxylate, 1 ,4- cyclohexane dimethanoldigrycicdyl ether, hydrogenated bis-phenol-A type epoxy resin and/or tris(2,3-epoxypropyl) isocyanurate.
• any suitable alicyclic epoxy resin may be used.
• the composition may contain an epoxy-functional copolymer as the reactive modifier.
• exemplary copolymers having multiple epoxy pendant groups include the reaction products of one or more ethylenically unsaturated monomers (e.g. styrene, ethylene, and the like) with an epoxy-containing ethylenically unsaturated monomer (e.g. glycidyl C1 -4 (alkyl) acrylate, ally glycidyl ethacryalte, and glycidyl itoconate).
• the epoxy- functional copolymer is a styrene-acrylic copolymer (including an oligomer) containing glycidyl groups incorporated as side chains.
• the reactive modifier may comprise an anhydride.
• examples may include pyromellitic dianhydride, trimellitic anhydride, 3- (triethoxysilyl) propylsuccinic anhydride, and the like.
• Other reactive modifiers can include various oxazolines and/or silanes.
• Such reactive modifiers can include phenylenebisoxazoline and 3-aminopropyltriethoxysilane.
• the one or more reactive modifiers may be present in the composition in an amount sufficient to stabilize the viscosity of the composition during melt processing without causing viscosity fluctuations. In other embodiments, the one or more reactive modifiers may be present in the composition in an amount sufficient such that the composition displays desired whiteness properties, such as desired whiteness properties after being thermally aged. In general, the reactive modifiers are present in the composition in an amount from about 0.2% to about 8% by weight, such as from about 0.5% to about 5% by weight. [0074] Of particular advantage, reactive modifiers may be selected that do not significantly increase yellowing of the composition over time.
• the polymer composition can be formulated so as to be substantially or completely free of various aromatic epoxy resins. In one embodiment, for instance, the
• composition is free of any epoxy novolac resins, such as an epoxy cresol novolac resin.
• Reactive modifiers that may be used that do not significantly increase yellowing of a molded article made from the composition can include reactive modifiers that do not have a deep color.
• the reactive modifier may have a color b* value according to the CIELAB Test Method of less than about 2.
• the CIELAB methodology is described in Pocket Guide to Digital Printing by F. Cost, Delmar Publishers, Albany, N.Y. ISBN 0-8273-7592-1 at pages 144 and 145 and "Photoelectric color difference meter", Journal of Optical Society of America, volume 48, page numbers 985-995, S. Hunter, (1958), both of which are incorporated herein by reference in their entirety. More specifically, the CIELAB test method defines three "Hunter" scale values, L*, a*, and b*, which correspond to three characteristics of a perceived color based on the opponent theory of color perception and are defined as follows:
• a* Red/green axis, ranging from -100 to 100; positive values are reddish and negative values are greenish; and
• b* Yellow/blue axis, ranging from -100 to 100; positive values are yellowish and negative values are bluish.
• Color measurement can be performed using a DataColor 650
• Color coordinates can likewise be calculated according to ASTM D2244-1 1 under an illuminant D65/10°C, A/10°, or F2/10° observer, using CIELAB units.
• the polymer composition of the present disclosure can further contain one or more impact modifiers.
• the impact modifiers can be reactive with the thermoplastic polymer, such as the PCT polymer, or non-reactive.
• the composition contains at least one reactive impact modifier and at least one non-reactive impact modifier.
• Reactive impact modifiers that may be used include ethylene-maleic anhydride copolymers, ethylene-alkyl (meth)acrylate-maleic anhydride copolymers, ethylene-alkyl (meth)acrylate-glycidyl (meth)acrylate copolymers, and the like.
• a reactive impact modifier is used that comprises a random terpolymer of ethylene, methylacrylate, and glycidyl methacrylate.
• the terpolymer can have a glycidyl methacrylate content of from about 5% to about 20%, such as from about 6% to about 10%.
• the terpolymer may have a
• methylacrylate content of from about 20% to about 30%, such as about 24%.
• the present inventors have discovered that the combination of a reactive impact modifier with a reactive modifier, may, in some embodiments, further improve the whiteness index of articles made according to the present disclosure after heat aging.
• a reactive impact modifier may be present in the composition in an amount from about 0.05% to about 20% by weight, such as in an amount from about 0.1 % to about 5% by weight.
• Non-reactive impact modifiers that may be blended into the polymer composition of the present disclosure generally include various rubber materials, such as acrylic rubbers, ASA rubbers, diene rubbers, organosiloxane rubbers, EPDM rubbers, SBS or SEBS rubbers, ABS rubbers, NBS rubbers, and the like.
• an ethylene acrylic rubber is present such as an ethylene acrylic ester copolymer.
• Particular examples of non-reactive impact modifiers include ethylene butylacrylate, ethylene (methyl)acrylate, or 2 ethyl hexyl acrylate copolymers.
• copolymer is present in the composition that contains (methyl)acrylate in an amount of from about 20% to about 30% by weight, such as in an amount of about 24% by weight.
• the composition of the present disclosure includes a combination of an ethylene ( methyl )acry late copolymer combined with a terpolymer of ethylene, methylacrylate and glycidyl methacrylate.
• non-reactive impact modifiers can be included in amounts of from about 0.05% to about 15% by weight, such as in an amount from about 0.1 % to about 8% by weight.
• the polymer composition of the present disclosure may contain a mixture of thermoplastic polymers.
• a mixture of thermoplastic polymers for instance, in one
• the composition may contain a PCT polymer in combination with one or more thermoplastic polymers.
• the other thermoplastic polymers can be present in an amount from about 1 % to about 15% by weight.
• Other thermoplastic polymers that may be included include other polyester polymers, a liquid crystal polymer, or mixtures thereof.
• Other thermoplastic polyester polymers that may be included in the composition include poly(ethylene terephthalate), poly(propylene terephthalate), poly(butylene terephthalate), acid-modified PCT copolyesters, poly(ethylene naphthalate), poly(butylene naphthalate), aliphatic polyesters such as polyester glutarate, and the like.
• the inclusion of small amounts of other polyester polymers or a liquid crystal polymer may, in some embodiments, improve the processability of the composition.
• the composition may contain an aromatic liquid crystal polyester polymer in an amount of from about 2% to about 5% by weight.
• Another additive that may be present in the polymer composition is a polytetrafluoroethylene polymer.
• a polytetrafluoroethylene polymer may enhance the reflectance and the whiteness index of articles made from the polymer composition.
• the polytetrafluoroethylene polymer may be added to the composition in the form of a fine powder having an average particle size of less than about 50 microns, such as less than about 10 microns. In one embodiment, for instance, the polytetrafluoroethylene powder may have an average particle size of from about 1 micron to about 8 microns.
• the polytetrafluoroethylene polymer may be present in the composition in an amount from about 0.05% to about 0% by weight, such as from about 0.1 % to about 6% by weight.
• the polymer composition can also include a lubricant.
• the lubricant may comprise, for instance, a polyethylene wax, an amide wax, a montanic ester wax, a polyol ester, or the like.
• a lubricant in certain embodiments, for instance, may comprise a polyethylene glycol-dilaurate and/or a neopentyl glycol dibenzoate.
• the lubricant may comprise an oxidized polyethylene wax.
• the polyethylene wax may have a density of from about 0.94 g/cm 3 to about 0.96 g/cm 3 .
• the lubricant may be included in the composition in an amount from about 0.05% to about 6% by weight, such as from about 0.1 % to about 4% by weight.
• the composition may contain various other additives and ingredients.
• the composition may contain various thermal and oxidative stabilizers, ultraviolet light stabilizers, brighteners, and the like.
• the composition may include a suitable optical brightener, such as a benzoxazole.
• the composition may include benzoxazole, 2,2'-(1 ,2-ethenediyldi-4,1 -phenyiene)bis-, which has CAS Registry Number 1533-45-5, or another suitable benzoxazole.
• the optical brightener may further enhance the reflectance.
• the polymer composition may contain a sterically hindered amine light stabilizer.
• hindered amine light stabilizers When present in the composition, hindered amine light stabilizers have been found to provide various advantages and benefits. For instance, sterically hindered amine light stabilizers have been found to further improve the reflectance properties of the material, especially after long term aging.
• Light stabilizers may be present in the composition in an amount from about 0.05% to about 3% by weight, such as in an amount from about 0.05% to about 1 % by weight.
• a hindered amine light stabilizer may be used in conjunction with a hindered phenolic antioxidant and a phosphorous- containing stabilizer.
• the phosphorous-containing stabilizer may comprise an organophosphorus compound containing at least one phosphorus having a +5 valence state.
• the organophosphorus compound for instance, may comprise a phosphonate or a phosphate.
• a phosphorus stabilizer as described above has been found to significantly improve whiteness stability while preserving the ability of the polymer composition to adhere to silicone resins.
• the phosphonate stabilizer provides the above benefits while being contained in the polymer composition at relatively minor amounts.
• the organophosphorus compound may be present in the polymer composition in an amount of less than about 5% by weight, such as in an amount of less than about 3% by weight, such as in an amount of less than about 2% by weight, such as even in an amount less than about 1 % by weight.
• the organophosphorus compound may be present in the polymer composition in an amount of less than about 5% by weight, such as in an amount of less than about 3% by weight, such as in an amount of less than about 2% by weight, such as even in an amount less than about 1 % by weight.
• the organophosphorus compound may be present in the polymer composition in an amount of less than about 5% by weight, such as in an amount of less than about 3% by weight, such as in an amount of less than about 2% by weight, such as even in an amount less than about 1 % by weight.
• the organophosphorus compound may be present in the polymer composition in
• organophosphorus compound may be present in the polymer composition in an amount from about 0.01 % to about 3% by weight, such as from about 0.01 % to about 2% by weight.
• the stabilizer may comprise an organophosphorus compound having the following phosphorus group:
• a phosphonate stabilizer may be used having the following formula:
• R1 is H, C1 -C20 alkyl, unsubstituted or C1-C4 alkyl-substituted phenyl or naphthyl
• R2 is H, C1 -C20 alkyl, unsubstituted or C1 -C4 alkyl-substituted phenyl or naphthyl, or Mr+r wherein Mr+ is an r-valent metal cation or ammonium ion;
• n is an integer from 0 to 6, and r is an integer from 1 to 4;
• A is hydrogen, -X-C(O)-OR8, or a radical of
• R3 or R4 is H, C1 to C18 alkyl, OH, halogen or C3-C7 cycloalkyl;
• R5 or R6 is hydrogen, C1-C4 alkyl, cyclohexyl, or cyclohexyl which is substituted by 1-3 C1 -C4 alkyl groups;
• R7 is hydrogen, methyl, trimethylsilyl, benzyl, phenyl, sulfonyl or C1-C18 alkyl
• R8 is hydrogen, C1-C10 alkyl or C3-C7 cycloalkyl
• X is phenylene, C1-C4 alkyl group-substituted phenylene or cyclohexylene.
• Particular examples of phosphonates that may be used according to the present disclosure include phenyl phosphonates and benzyl phosphonates, such as diethyl 1 -phenyl ethyl phosphonate, diethyl 2-phenyl ethyl phosphonate, diethyl benzyl phosphonate, or mixtures thereof.
• Particular phosphonate compounds include, for instance:
• a phosphate stabilizer that has the following formula:
• the phosphate stabilizer may comprise an organophosphorus compound that has the same phosphorus group as described above.
• the phosphate stabilizer may have the following formula:
• Ri, R2, R3, and R4 are H, C1-C20 alkyl, unsubstituted or C1 -C10 alkyl substituted phenyl or naphthyl;
• n is an integer of 1 to 10;
• p is an integer of 1 to 4.
• phosphates that may be used according to the present disclosure include triphenyl phosphate, tributyl phosphate, tricresyl phosphate, 2-ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, oligomeric ethyl ethylene phosphate, bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), or mixtures thereof.
• the polymer composition in one embodiment, can comprise a melt-mixed blend, wherein all of the polymeric components are well-dispersed within each other and all of the non-polymeric ingredients are well-dispersed in and bound by the polymer matrix, such that the blend forms a unified whole.
• any melt-mixing method may be used to combine the polymeric components and non-polymeric ingredients.
• the polymeric components and the non-polymeric components may be added to a melt mixer, such as for example a single or twin-screw extruder, a blender, a kneader, or a Banbury mixer, either all at once through a single step addition, or in a stepwise fashion and then melt-mixed.
• a melt mixer such as for example a single or twin-screw extruder, a blender, a kneader, or a Banbury mixer, either all at once through a single step addition, or in a stepwise fashion and then melt-mixed.
• the blended composition can then be molded into any desired shape through any suitable molding process.
• articles are formed through injection molding.
• the temperature of the composition may be from about 280°C to about 350°C.
• the temperature of the molds may be in a range of from about 80°C to about 150°C.
• the melt viscosity of the polymer composition when measured by a capillary rheometer at 305°C under 1000 sec -1 shear rate can be less than about 200 Pa.s, such as less than about 150 Pa.s, such as less than about 00 Pa.s, such as less than about 80 Pa.s, such as less than about 70 Pa.s, such as less than about 60 Pa.s.
• the melt viscosity of the polymer under the above conditions is greater than about 10 Pa.s, such as greater than about 20 Pa.s. In one particular embodiment, the melt viscosity is from about 40 Pa.s, to about 80 Pa.s.
• the polymer composition of the present disclosure is particularly well suited for producing reflectors for LED assemblies.
• the reflectance properties of the polymer are particularly well suited for use with white LEDs.
• the LED reflector may be in the form of a single piece or may be formed from two or more subparts.
• the polymer composition is injection molded over the lead frame as shown in Figs. 1 and 2. In this manner, the lead frame and the reflector become integrated together.
• the semiconductor light-emitting diode chip can then be mounted within the cavity of the reflector and connected to the lead frame.
• the LED can be bonded to the lead frame using the bonding wires.
• the entire assembly can be encased or the cavity defined by the reflector can be filled with a core material such as a solid epoxy that can form a lens for focusing the light in a single direction.
• Molded articles made in accordance with the present disclosure not only exhibit good adhesion properties to resins, such as silicone and epoxy polymers, but also exhibit excellent light reflective and light stable properties.
• the polymeric composition may exhibit silicone bond strengths according to the Lap-Shear Test of greater than about 25 Ibf, such as greater than about 40 Ibf, such as greater than about 50 Ibf, such as even greater than about 60 Ibf.
• the Lap-Shear Test is described in greater detail in the examples below.
• LED assemblies made in accordance with the present disclosure can be used in numerous and different applications.
• the LED assemblies can be used in traffic signal lights, LCD displays, backlights, cellular telephones, automotive display lights, automotive headlamps, flashlights, interior lighting, streetlights, and in exterior lighting applications.
• the polymer composition of the present disclosure can also be used to make various other articles.
• the polymer composition can be used to produce any article where good light reflectance properties are desired.
• molded articles made according to the present disclosure can be used in signs and labels in order to improve the visual appearance of the item.
• a molded article made in accordance with the present disclosure may be used in a lighted sign, such as an exit sign.
• polymer composition examples include use as a roofing material or used as a component in a solar cell.
• the polymer composition may also be used to produce trim pieces and bezels for consumer products, such as consumer appliances.
• the polymer composition may be used to mold interior trim pieces for vehicles, such as automobiles.
• Table 1 lists various compositions that were prepared by melt compounding the components shown in the table using a 32 mm twin-extruder operating at 300°C, using a screw speed of about 350 rpm and a melt temperature of from about 320°C to about 330°C. Upon exiting the extruder, the compositions were cooled and pelletized.
• compositions were molded into ISO tensile bars according to ISO Method 527-1/2 using a mold temperature of about 120°C. Tensile properties of the samples were determined using the test method above. Charpy impact strengths and Notched Charpy impact strengths were determined following ISO Test 179.
• the initial whiteness index and the whiteness index after aging were determined using the same reflectance scan based on Wl E313. Higher whiteness index numbers indicate better whiteness.
• compositions made according to the present disclosure displayed excellent initial reflectance, excellent initial whiteness index and displayed excellent whiteness index properties after aging.
• Table 2 below lists various compositions that were prepared by melt compounding the components shown in the table using a 32 mm twin-extruder operating at about 300°C, using a screw speed of about 300 rpm and a melt temperature of from about 320°C to about 330°C. Upon exiting the extruder, the compositions were cooled and pelletized.
• compositions were molded into ISO tensile bars according to ISO method 527-1/2 using a mold temperature of about 120°C.
• the phosphonate stabilizer used was calcium
• the phosphate stabilizer used was triphenyl phosphate.
• Table 3 depicts the properties of the compositions shown in Table 2. Tensile properties were determined using the test method above. Charpy impact strengths and Notched Charpy impact strengths were determined following ISO Test 179.
• Wl Whiteness Index
• Silicone adhesion was tested according to a peel test and according to a Lap-Shear Test. According to the peel test, a silicone resin is mixed and cast as a layer on the tensile bars described above.
• the silicone resin used is Dow Corning SYLGARD 577A/B (in a 10:1 ratio).
• the above silicone resin is a silicone elastomer. Once the silicone resin is applied to the tensile bar, the part is cured at 180°C for 15 minutes in an oven and then removed from the oven and cooled to room temperature. The silicone layer is peeled by hand to check for adhesion. If the silicone layer peels easily, the test is a failure. If the silicone cannot be peeled off by hand, however, the adhesion to silicone passes.
• the second silicone adhesion test method is a Lap-Shear Test.
• the PCT composition is molded into ISO tensile bars.
• the bar is then cut into half sections.
• the two pieces of half sections are placed on a 2" copper strip with a silicone adhesive layer adhering the copper strip to the test pieces.
• the silicone adhesive used is a LED encapsulate silicone, which is Dow Corning OE 6630A/B silicone resin.
• the two parts of the silicone resin are mixed in a 1 :4 ratio.
• the half bars and copper strip are cured at 150°C for 2 hours, and then allowed to cool down.
• the bonded tensile bars are tested by a tensile machine to obtain the peak load for breaking the bond at speed of 1 inch/min at room temperature (23°C).
• each half section of the tensile bar is placed in the jaws of the tensile machine.
• the peak load is recorded when one of the half sections releases from the copper strip.
• Figure 5 illustrates the two
• compositions made with the phosphonate or phosphate stabilizer displayed improved reflectance stability and silicone adhesion.

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