Polyester polymer composition

Abstract

Fiber reinforced polyester polymer compositions containing at least one friction modifier are disclosed. The friction modifier may comprise an ultra-high molecular weight silicone alone or in combination with polytetrafluoroethylene particles. The composition not only has excellent tensile properties, but also can produce a low friction surface.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 62 / 469,874, filed on March 10, 2017, the entire contents of which are incorporated by reference. Background Art

[0003] Engineering thermoplastics and elastomeric materials are commonly used in a wide variety of applications to produce molded parts and products. For example, polyester polymers and polyester elastomers are used to produce all different types of molded products, such as injection molded products, blow molded products, and the like. Polyester polymers, for example, can be formulated to have chemical resistance, thereby having excellent strength properties, and when a composition containing a polyester elastomer is formulated, it can be formulated to have flexibility. It is particularly advantageous that polyester polymers can be melt processed due to their thermoplastic properties. In addition, polyester polymers can be recycled and reprocessed.

[0004] In certain applications, thermoplastic polymers, such as polyester polymers, are combined with fiber fillers to increase the modulus and / or tensile strength of parts and products made from the reinforced composition. However, in the past, problems have been experienced in incorporating reinforcing fibers into a polyester polymer matrix with a desired balance of properties. For example, a polyester polymer composite containing reinforcing fibers may have sufficient strength properties, but may experience increased surface friction when moving over adjacent surfaces. Increased friction may, for example, result in abrasive wear after prolonged use. These problems are exacerbated when a first component made from a polyester polymer matrix is ​​designed to slide or scrape relative to an adjacent component made from the same reinforced polyester matrix.

[0005] In view of the above, there exists a need for reinforced polyester polymer compositions that can be formulated to have a desired balance of physical properties and characteristics. More specifically, there exists a need for fiber reinforced polyester polymer compositions that also have reduced friction properties. Summary of the invention

[0006] The present disclosure generally relates to polyester polymer compositions containing reinforcing fibers for improving tensile strength, combined with a friction additive package that has been found to significantly reduce the coefficient of friction properties of articles molded from the composition. Components and articles can be made in accordance with the present disclosure that not only have excellent strength properties and performance, but are also well suited for applications where the component or article is intended to slide relative to an opposing surface. For example, the articles and products can be formulated to not produce audible noise when sliding relative to an opposing component or component, particularly when the opposing component or component is also made from the same or similar polymer composition.

[0007] In one embodiment, for example, polymer compositions of the present disclosure include polyester polymers containing polybutylene terephthalate polymers. The polybutylene terephthalate polymers can exist alone or in combination with other polymers in the composition. Other polymers can include, for example, different polyester polymers, such as polyethylene terephthalate, polycarbonate polymers, etc. The polymer composition also contains reinforcing fibers, such as glass fibers. The amount of reinforcing fibers that can be present in the composition is generally greater than about 5 weight %, such as an amount greater than about 10 weight %, such as an amount greater than about 15 weight %. The amount of reinforcing fibers that exist is generally lower than about 55 weight %, such as an amount lower than about 45 weight %, such as an amount lower than about 35 weight %.

[0008] According to the present disclosure, the polymer composition further contains at least one friction modifier. In one embodiment, the friction modifier may include an ultra-high molecular weight silicone. The ultra-high molecular weight silicone may have a molecular weight greater than about 100,000 mm 2 s -1 For example, the ultra-high molecular weight silicone may be present in the polymer composition in an amount of about 0.1 wt % to about 10 wt %, such as about 0.5 wt % to about 3 wt %. In one embodiment, the ultra-high molecular weight silicone comprises polydimethylsiloxane.

[0009] In an alternative embodiment, the friction modifier contained in the polymer composition may include a polytetrafluoroethylene polymer. The polytetrafluoroethylene polymer may be present alone or in combination with an ultra-high molecular weight silicone.

[0010] In a specific embodiment, the polymer composition comprises a polybutylene terephthalate polymer in an amount of about 50% to about 90% by weight, reinforcing fibers such as glass fibers are present in the composition in an amount of about 5% to about 30% by weight, ultra-high molecular weight silicone is present in the composition in an amount of about 0.5% to about 4% by weight, and a polytetrafluoroethylene polymer is present in the composition in an amount of about 1% to about 20% by weight.

[0011] As described above, the polymer composition can be formulated to have low friction properties. For example, the polymer composition can exhibit a dynamic friction coefficient of less than about 0.08 according to VDA 230-206 at a speed of 8 mm / s, a load of 30 N and 1,000 cycles when tested relative to polycarbonate containing 15 wt% polytetrafluoroethylene and 20 wt% glass fibers or when tested relative to polybutylene terephthalate containing 15 wt% polytetrafluoroethylene and 20 wt% glass fibers, or when tested relative to itself. In one embodiment, the polymer composition can exhibit a dynamic friction coefficient of less than about 0.07, such as less than about 0.05, when tested relative to the above materials.

[0012] When an ultra-high molecular weight silicone is present in the composition, the silicone can be added with a carrier. In one embodiment, for example, the ultra-high molecular weight silicone can be grafted to silica and added to the composition. Alternatively, the ultra-high molecular weight silicone can be combined with a carrier polymer and then blended with the other components. The carrier polymer, for example, can include a polycarbonate polymer or a polyester polymer. The polyester polymer, for example, can include polyethylene terephthalate, a copolyester, and / or a polyester elastomer.

[0013] In one embodiment, the polymer composition of the present disclosure is formulated for use in the production of a medical product. When producing a medical product, for example, the polymer composition can be formulated to be isocyanate-free.

[0014] In one embodiment, the polymer composition can be used to produce medical inhalers, syringes, and the like. The medical product, for example, can include a first sliding member operatively associated with a second sliding member. The first sliding member and the second sliding member can be positioned to maintain contact and move relative to each other. At least one of the sliding members can be made of a polymer composition of the present disclosure. In one embodiment, for example, both sliding members are made of a polymer composition of the present disclosure.

[0015] Other features and aspects of the present disclosure are discussed in greater detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A full and enabling disclosure of the present disclosure is more particularly set forth in the remainder of the specification, including with reference to the accompanying drawings, in which:

[0018] Figure 1 is a perspective view of a medical inhaler made in accordance with the present disclosure; and

[0019] Figure 2 is a side view of a medical syringe that can be made according to the present disclosure.

[0020] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention. Detailed description

[0022] Those of ordinary skill in the art will appreciate that the present discussion is merely illustrative of exemplary embodiments and is not intended to be limiting of the broader aspects of the present disclosure.

[0023] The present disclosure generally relates to polyester polymer compositions and polymer articles made from the compositions, which not only have improved strength properties, but also have improved friction properties, such as low friction properties. The polyester polymer composition contains reinforcing fibers for increasing the strength of the composition. However, the reinforcing fibers can increase the friction characteristics of the composition and cause abrasive wear when placed in use. To counteract the presence of the reinforcing fibers, the polymer composition contains a friction stabilizer package. The friction additive package can include the presence of at least one friction modifier, such as an ultra-high molecular weight silicone, a polytetrafluoroethylene polymer, or a combination thereof.

[0024] Compositions of the present disclosure can be formulated for medical applications. For example, when used for medical applications, the polymer composition can be free of isocyanates, epoxy resins, carbodiimides or other similar compounds. In some applications, such medical equipment is needed, wherein the parts are not only made of high-strength materials, but also can provide ultra-low friction and reduced wear for the parts intended to slide relative to adjacent surfaces. As will be described in more detail below, the polymer composition prepared according to the present disclosure has not only excellent strength properties, but can also show extremely low friction properties without the need to apply an external lubricant.

[0025] When two opposing surfaces slide relative to each other, the surfaces react in a manner known as stick-slip. Stick-slip refers to the manner in which two opposing surfaces or articles react to frictional forces to slide over each other. Static friction refers to the friction between two or more objects that are not moving relative to each other. On the other hand, dynamic friction occurs when two objects move relative to each other while remaining in contact. In order for one object to slide relative to another, sufficient force must be applied to one object to overcome the static friction force. When movement occurs between the two objects, the reduction in friction between the two surfaces can cause the movement speed to suddenly increase. In other words, once one object moves relative to the other, in some applications, less force is required to keep the movement going. During the movement, the friction between the two surfaces can increase or decrease depending on many factors, including the speed at which the movement continues. Stick-slip describes how the surfaces alternate between sticking to each other and sliding over each other as movement occurs between the two surfaces and as the state of movement changes.

[0026] Polymer articles with relatively high coefficients of friction not only require more force to slide one material over another, but can also be susceptible to wear. Over time, for example, these materials can begin to degrade due to friction.

[0027] As two surfaces move relative to each other and the stick-slip phenomenon occurs, noise is also generated from both surfaces. Depending on the stick-slip properties of the material, the noise generation can be highly audible or very quiet. In many applications, noise generation caused by the stick-slip phenomenon when two components slide relative to each other is highly undesirable. For example, when designing and manufacturing medical devices and consumer products, manufacturers and engineers try to design products that do not generate noise when the product is in use. Noise generation during use of a product, for example, can give consumers the impression that the product is of low quality and made with cheap materials.

[0028] The present disclosure is particularly directed to polymer compositions that can be used to prepare molded parts so as to inhibit and even eliminate excessive wear and / or noise generation when the parts slide relative to each other.

[0029] For example, in one embodiment, the present disclosure relates to a low friction assembly comprising a first sliding member operatively associated with a second sliding member. The first sliding member and the second sliding member can both be made of a polymer composition formulated in accordance with the present disclosure. When tested relative to each other, the composition can be formulated to exhibit a dynamic friction coefficient of less than about 0.08, such as less than about 0.07, such as less than about 0.06, such as less than about 0.05. The composition or molded parts can be tested relative to each other according to the stick-slip test of test number VDA 230-206.

[0030] The samples tested using the above method can also be analyzed to measure the wear track width, i.e., the wear width. According to the present disclosure, when tested at a force of 30 N and a speed of 8 mm / s after 1,000 cycles, the compositions and molded articles can exhibit a wear track width of less than 0.3 mm, such as less than about 0.25 mm, such as even less than about 0.2 mm.

[0031] Polyester polymer

[0032] The polymer compositions of the present disclosure generally contain a polyester polymer in combination with reinforcing fibers and a friction additive package. The polyester polymer generally comprises a polyalkylene terephthalate polymer.

[0033] The polyalkylene terephthalate polymers suitable for use herein are derived from an aliphatic or cycloaliphatic diol containing from 2 to about 10 carbon atoms, or mixtures thereof, and an aromatic dicarboxylic acid.

[0034] Polyesters derived from cycloaliphatic diols and aromatic dicarboxylic acids are prepared by condensing, for example, the cis or trans isomers of 1,4-cyclohexanedimethanol (or mixtures thereof) with an aromatic dicarboxylic acid.

[0035] Examples of aromatic dicarboxylic acids include isophthalic or terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, and the like, and mixtures of these. All of these acids contain at least one aromatic nucleus. Fused rings may also be present, such as in 1,4- or 1,5- or 2,6-naphthalene dicarboxylic acids. In one embodiment, the dicarboxylic acid is terephthalic acid or a mixture of terephthalic and isophthalic acids.

[0036] In one embodiment, the polyalkylene terephthalate polymer present in the polymer composition comprises a polybutylene terephthalate polymer. For example, the polymer composition may contain a polybutylene terephthalate polymer in an amount greater than about 30 weight %, such as an amount greater than about 40 weight %, such as an amount greater than about 50 weight %, such as an amount greater than about 60 weight %, such as an amount greater than about 70 weight %. The polybutylene terephthalate polymer is typically present in an amount less than about 90 weight %, such as an amount less than about 80 weight %.

[0037] The polymer composition may contain a single polybutylene terephthalate polymer or a polybutylene terephthalate polymer in combination with other thermoplastic polymers. For example, the polybutylene terephthalate polymer may be combined with other polyester polymers and / or polycarbonate polymers. Other polyester polymers that may be present in the composition include polyethylene terephthalate polymers or polyethylene terephthalate copolymers. For example, polyethylene terephthalate copolymers or modified polyethylene terephthalate polymers may be produced with modified acids or modified glycols.

[0038] As used herein, the terms "modifying acid" and "modifying diol" are meant to define compounds that can form part of the acid and diol repeating units of the polyester, respectively, and can modify the polyester to reduce its crystallinity or render the polyester amorphous. However, in one embodiment, the polyester present in the polymer composition of the present disclosure is unmodified and does not contain a modifying acid or a modifying diol.

[0039] The example of modified acid component can include, but not limited to, isophthalic acid, phthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, 1,12-dodecane dicarboxylic acid and the like. In practice, it is often preferred to use its functional acid derivatives, such as dimethyl ester, diethyl ester or dipropyl ester of dicarboxylic acid. When practical, the anhydride or acyl halide of these acids can also be adopted. Preferred is isophthalic acid.

[0040] Examples of the modifying diol component may include, but are not limited to, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, Z,8-bis(hydroxymethyltricyclo-[5.2.1.0]-decane, wherein Z represents 3, 4 or 5; 1,4-bis(2-hydroxyethoxy)benzene, 4,4′-bis(2-hydroxyethoxy)diphenyl ether [bishydroxyethylbisphenol A], 4,4′-bis(2-hydroxyethoxy)diphenyl sulfide [bishydroxyethylbisphenol S], and diols containing one or more oxygen atoms in the chain, such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, etc. Typically, these diols contain 2 to 18, preferably 2 to 8, carbon atoms. Cycloaliphatic diols can be used in their cis or trans configuration, or as a mixture of the two forms.

[0041] When present, the polyester polymer or polycarbonate polymer in combination with the polybutylene terephthalate can be added to the polymer composition in an amount generally greater than about 5 weight %, such as an amount greater than about 10 weight %, such as an amount greater than about 15 weight %, such as an amount greater than about 20 weight %. The polyester polymer or polycarbonate polymer is generally present in an amount less than about 40 weight %, such as an amount less than about 30 weight %, such as an amount less than about 20 weight %, such as an amount less than about 15 weight %.

[0042] Reinforcement Fiber

[0043] The polymer composition contains reinforcing fibers in addition to a thermoplastic polymer matrix.

[0044] Reinforcing fibers that may advantageously be used are mineral fibers, such as glass fibers, polymer fibers, in particular organic high-modulus fibers, such as aramid fibers, or metal fibers, such as steel fibers, or carbon or natural fibers, fibers from renewable sources.

[0045] These fibers may be in modified or unmodified form, for example provided with a sizing agent, or chemically treated to improve adhesion to the plastic. Glass fibers are particularly preferred.

[0046] Glass fibers are provided with a sizing agent to protect the glass fibers, make the fibers smooth, and also improve the adhesion between the fibers and the matrix material. The sizing agent typically includes a silane, a film former, a lubricant, a wetting agent, a binder, optionally an antistatic agent and a plasticizer, an emulsifier, and optionally further additives.

[0047] Specific examples of silanes are aminosilanes, such as 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxy-silane, N-(3-trimethoxysilylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

[0048] Film formers are, for example, polyvinyl acetates, polyesters and polyurethanes. Polyurethane-based sizing agents can advantageously be used.

[0049] The reinforcing fibers can be compounded into the polymer matrix, for example, in an extruder or a kneader.

[0050] According to one embodiment, the molding composition of the present disclosure comprises at least one reinforcing fiber, which is a mineral fiber, preferably a glass fiber, more preferably a coated or impregnated glass fiber. Glass fibers suitable for the molding composition of the present disclosure are commercially available, for example, Johns Manville, Chopped Strand 753, OCV Chopped Strand 408A, Nippon Electric Glass Co. (NEG) Chopped Strand T-651.

[0051] The fiber diameter can vary depending on the specific fiber used and whether the fiber is chopped or continuous. The fiber, for example, can have a diameter of about 5 μm to about 100 μm, such as about 5 μm to about 50 μm, such as about 5 μm to about 15 μm. The length of the fiber can vary depending on a specific application. For example, the fiber can have a length greater than about 100 microns, such as greater than about 200 microns, such as greater than about 300 microns, such as greater than about 350 microns. The length of the fiber can be generally less than about 1,000 microns, such as less than about 800 microns, such as less than about 600 microns, such as less than about 500 microns. Once the polymer composition is incorporated and molded into an article, the fiber length can be reduced. For example, the average fiber length in the final product can be about 100 microns to about 400 microns, such as about 100 microns to about 300 microns.

[0052] Usually, the amount that fortifying fiber is present in this polymer composition is enough to improve the tensile strength of said composition.Fortifying fiber, for example, can be present in the amount of this polymer composition to be greater than about 5 wt %, such as amount to be greater than about 10 wt %, such as amount to be greater than about 15 wt %, such as amount to be greater than about 20 wt %, such as amount to be greater than about 25 wt %, such as amount to be greater than about 30 wt %.The amount that fortifying fiber exists usually is to be lower than about 55 wt %, such as amount to be lower than about 50 wt %, such as amount to be lower than about 45 wt %, such as amount to be lower than about 40 wt %, such as amount to be lower than about 35 wt %, such as amount to be lower than about 30 wt %.

[0053] Friction modifiers

[0054] According to the present disclosure, the polymer compositions and polymer articles comprising the reinforced polyester polymer compositions may include at least one friction modifier.

[0055] In one embodiment, ultra high molecular weight silicone (UHMW-Si) can be used to modify the polyester polymer. Typically, the UHMW-Si can have an average molecular weight greater than 100,000 g / mol, such as greater than about 200,000 g / mol, such as greater than about 300,000 g / mol, such as greater than about 500,000 g / mol and less than about 3,000,000 g / mol, such as less than about 2,000,000 g / mol, such as less than about 1,000,000 g / mol, such as less than about 500,000 g / mol, such as less than about 300,000 g / mol. Typically, the UHMW-Si can have an average molecular weight greater than 100,000 mm2 measured at 40°C according to DIN 51562. 2 s -1 , such as greater than about 200,000 mm 2 s -1 , for example greater than about 1,000,000 mm 2 s -1 , such as greater than about 5,000,000 mm 2 s -1 , such as greater than about 10,000,000 mm 2 s -1 , such as greater than about 15,000,000 mm 2 s -1 and less than about 50,000,000mm 2 s -1 , for example, less than about 25,000,000 mm 2 s -1 , for example, less than about 10,000,000 mm 2 s -1, for example, less than about 1,000,000mm 2 s -1 , for example, less than about 500,000mm 2 s -1 , for example, less than about 200,000mm 2 s -1 The dynamic viscosity.

[0056] UHMW-organic silicon can include siloxanes, such as polysiloxanes or polyorganosiloxanes. In one embodiment, the UHMW-Si can include dialkyl polysiloxanes, such as dimethyl siloxanes, alkyl aryl siloxanes, such as phenyl methyl siloxanes, polysilsesquioxanes, or diaryl siloxanes, such as diphenyl siloxanes, or homopolymers thereof, such as polydimethyl siloxanes or polymethyl phenyl siloxanes, or copolymers thereof, with the above-mentioned molecular weight and / or dynamic viscosity requirements. Polysiloxanes or polyorganosiloxanes can also be modified with substituents, such as epoxy groups, hydroxyl groups, carboxyl groups, amino groups or substituted amino groups, ether groups or methyl (acryloyl) groups at the molecular ends or on the main chain. UHMW-Si compounds can be used alone or in combination. Any of the above-mentioned UHMW-Si compounds with the above-mentioned molecular weight and / or dynamic viscosity requirements can be used.

[0057] UHMW-silicon can be added to the polymer composition as a masterbatch, wherein the UHMW-Si is dispersed in a carrier polymer, and then the masterbatch is added to the composition. The masterbatch can contain about 10 wt.% to about 60 wt.%, such as about 35 wt.% to about 55 wt.%, such as about 50 wt.% UHMW-Si.

[0058] The carrier polymer can vary depending on the specific application and the desired results. The carrier polymer for the ultra-high molecular weight silicone can include any thermoplastic polymer compatible with polybutylene terephthalate. In one embodiment, for example, the carrier polymer can include a polyester polymer. Using a polyester polymer, for example, will help blend the ultra-high molecular weight silicone polymer with a polybutylene terephthalate polymer. The polyester carrier polymer, for example, can include polybutylene terephthalate, polyethylene terephthalate, copolyesters, and / or polyester elastomers. The polyester elastomer can include a copolyester, such as a segmented thermoplastic copolyester. The polyester elastomer, for example, can include a multi-block copolymer. In an alternative embodiment, the carrier polymer can include a polycarbonate polymer.

[0059] In alternative embodiments, instead of using a carrier polymer, the ultra-high molecular weight organosilicon polymer can be grafted onto particles, which are then incorporated into the polymer composition. For example, in one embodiment, the ultra-high molecular weight organosilicon polymer can be grafted onto metal oxide particles, such as silica particles. The ultra-high molecular weight organosilicon grafted to the silica can then be present in the composition in an amount greater than about 1% by weight, such as an amount greater than about 2% by weight, such as an amount greater than about 3% by weight, such as an amount greater than about 4% by weight. The ultra-high molecular weight organosilicon grafted to the silica is typically present in the composition in an amount less than about 20% by weight, such as an amount less than about 15% by weight, such as an amount less than about 10% by weight, such as an amount less than about 6% by weight.

[0060] UHMW-silicones may be present in the polymer composition in an amount greater than about 0.005 wt.%, such as greater than about 0.1 wt.%, such as greater than about 0.5 wt.%, such as greater than about 0.75 wt.%, such as greater than about 1 wt.%, such as greater than about 2 wt.%, such as greater than about 2.5 wt.% and typically less than about 10 wt.%, such as less than about 6 wt.%, such as less than about 5 wt.%, such as less than about 4 wt.%, such as less than about 3.5 wt.%, such as less than about 3 wt.%, wherein the weight is based on the total weight of the polymer composition.

[0061] In alternative embodiments, the at least one friction additive may include a fluoropolymer, such as polytetrafluoroethylene powder. In one application, the fluoropolymer may be combined with an ultra-high molecular weight silicone. The polytetrafluoroethylene particles, for example, may have an average particle size of less than about 15 microns, such as less than about 12 microns, such as less than about 10 microns, such as less than about 8 microns. The average particle size of the polytetrafluoroethylene particles is typically greater than about 0.5 microns, such as greater than about 1 micron, such as greater than about 2 microns, such as greater than about 3 microns, such as greater than about 4 microns, such as greater than about 5 microns. The average particle size can be measured according to ISO test 13321.

[0062] In one embodiment, the polytetrafluoroethylene particles can have a relatively low molecular weight. The polytetrafluoroethylene polymer can have a density of about 300 g / l to about 450 g / l, such as about 325 g / l to about 375 g / l, when tested according to ASTM test D4895. The polytetrafluoroethylene particles can have a specific surface area of ​​about 5 m 2 / g to about 15m 2 / g, for example, about 8m 2 / g to about 12m 2 / g when tested according to test DIN 66132. The melt flow rate of the polytetrafluoroethylene polymer may be lower than about 3 g / 10 min, such as lower than about 2 g / 10 min, when tested according to ISO test 1133 at 372°C with a load of 10 kg.

[0063] The polytetrafluoroethylene particles can be present in the polymer composition in an amount greater than about 1 wt %, such as an amount greater than about 2 wt %, such as an amount greater than about 3 wt %, such as an amount greater than about 4 wt %. The polytetrafluoroethylene polymer is typically present in the polymer composition in an amount less than about 20 wt %, such as an amount less than about 15 wt %, such as an amount less than about 10 wt %, such as an amount less than about 8 wt %.

[0064] According to the present disclosure, the friction additive improves the friction properties of the polymer composition and the polymer articles produced therefrom, but without the need for an external lubricant, such as a water-based external lubricant, when used in friction applications. An external lubricant can be a lubricant applied to a polymer article. In one embodiment, the external lubricant may not be associated with the polymer composition or polymer article, so that the external lubricant is not present on the surface of the polymer composition or polymer article. In another embodiment, an external lubricant can be used in the polymer composition and polymer article of the present disclosure.

[0065] In addition to the ultra-high molecular weight silicone and / or polytetrafluoroethylene polymer, the polymer composition may contain other friction modifiers. Other friction modifiers that may be present include, for example, boron nitride, ultra-high molecular weight polyethylene particles, stearyl stearate particles, waxes, etc. The other friction modifiers may typically be present in an amount of about 0.5% to about 5% by weight, such as about 1% to about 3% by weight.

[0066] Other additives

[0067] The polymer composition of the present disclosure may contain various other additives. For example, the composition may further include a nucleating agent, present in a concentration of about 0.1-2% by weight, preferably about 0.001% to 0.5%, based on the total weight of the composition. The nucleating agent may be selected from an alkali metal salt with an anion, i.e., an oxide of an element of Group IV of the periodic table; barium sulfate; and talc.

[0068] The polymer composition may also contain at least one stabilizer. The stabilizer may include an antioxidant, a light stabilizer, such as an ultraviolet light stabilizer, a heat stabilizer, and the like.

[0069] One or more sterically hindered phenolic antioxidants may be used in the composition. Examples of such phenolic antioxidants include, for example, calcium bis(ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate) ( 1425); terephthalic acid, 1,4-dithio-, S,S-bis(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) ester ( 1729); triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylhydrocinnamate); hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate ( 259); 1,2-bis(3,5,di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine( 1024); 4,4′-di-tert-octyl diphenylamine ( 438R); Phosphonic acid, (3,5-di-tert-butyl-4-hydroxybenzyl) dioctadecyl ester ( 1093); 1,3,5-trimethyl-2,4,6-tri(3′,5′-di-tert-butyl-4′hydroxybenzyl)benzene ( 1330); 2,4-bis(octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine ( 565); isooctyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate ( 1135); Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate ( 1076); 3,7-bis(1,1,3,3-tetramethylbutyl)-10H-phenothiazine ( LO 3); 2,2′-methylenebis(4-methyl-6-tert-butylphenol) monoacrylate ( 3052); 2-tert-butyl-6-[1-(3-tert-butyl-2-hydroxy-5-methylphenyl)ethyl]-4-methylphenyl acrylate ( TM 4039); 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate ( GS); 1,3-dihydro-2H-benzimidazole ( MB); 2-methyl-4,6-bis[(octylthio)methyl]phenol ( 1520); N, N'-trimethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide( 1019); 4-n-octadecyloxy-2,6-diphenylphenol ( 1063); 2,2′-ethylenebis[4,6-di-tert-butylphenol]( 129); NN′-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid amide)( 1098); (3,5-di-tert-butyl-4-hydroxybenzyl)phosphonic acid diethyl ester ( 1222); 4,4′-di-tert-octyldiphenylamine ( 5057); N-phenyl-1-naphthylamine ( L 05); tris[2-tert-butyl-4-(3-tert-butyl-4-hydroxy-6-methylphenylthio)-5-methylphenyl]phosphite ( OSP 1); Zinc dinonyl dithiocarbamate ( VP-ZNCS1); 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane ( AG80); Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]( 1010); Ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)-propionate( 245); 3,5-di-tert-butyl-4-hydroxytoluene (Lowinox BHT, Chemtura), etc.

[0070] Some examples of suitable sterically hindered phenolic antioxidants for use in the compositions of the present invention are triazine antioxidants having the following general formula:

[0071]

[0072] Wherein, each R is independently a phenolic group, which can be 1 -C 5 The alkyl or ester substituent is attached to the triazine ring. Preferably, each R is one of the following formulae (I)-(III):

[0073] (I)

[0074]

[0075] (II)

[0076]

[0077] (III)

[0078]

[0079] Commercially available examples of such triazine-based antioxidants may be found under the names 1790 (wherein each R group is represented by formula III) is available from American Cyanamid and under the name 3114 (wherein each R group is represented by formula I) and 3125 (wherein each R group is represented by Formula II) was obtained from Ciba Specialty Chemicals.

[0080] The sterically hindered phenolic antioxidant may comprise from about 0.01 wt.% to about 3 wt.%, in some embodiments from about 0.05 wt.% to about 1 wt.%, and in some embodiments from about 0.05 wt.% to about 0.1 wt.% of the total stabilized polymer composition. In one embodiment, for example, the antioxidant comprises pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0081] Hindered amine light stabilizers ("HALS") may be used in the composition to inhibit degradation of the polyester composition and thereby extend its durability. Suitable HALS compounds may be derived from substituted piperidines, such as alkyl-substituted piperidyls, piperidinyls, piperazinones, alkoxypiperidinyls, and the like. For example, the hindered amine may be derived from 2,2,6,6-tetraalkylpiperidinyls. Regardless of the compound from which it is derived, the hindered amine is typically an oligomeric or polymeric compound having a number average molecular weight of about 1,000 or more, in some embodiments about 1000 to about 20,000, in some embodiments about 1500 to about 15,000, and in some embodiments about 2000 to about 5000. Such compounds typically contain at least one 2,2,6,6-tetraalkylpiperidinyl group (e.g., 1 to 4) per polymer repeating unit.

[0082] Without intending to be limited by theory, it is believed that high molecular weight hindered amines are relatively thermally stable and thus are able to resist photodegradation even after being subjected to extrusion conditions. A particularly suitable high molecular weight hindered amine has the following general structure:

[0083]

[0084] wherein p is 4 to 30, in some embodiments 4 to 20, and in some embodiments 4 to 10. The oligomer compound is named N30 is commercially available from Clariant and has a number average molecular weight of 1200.

[0085] Another suitable high molecular weight hindered amine has the following structure:

[0086]

[0087] Where n is 1 to 4 and R 30 are independently hydrogen or CH 3Such oligomer compounds can be named ADK LA-63(R 30 CH 3 ) and ADK LA-68(R 30 Hydrogen) was commercially available from Adeka Palmarole SAS (a joint venture between Adeka Corp. and Palmarole Group).

[0088] Other examples of suitable high molecular weight hindered amines include, for example, oligomers of N-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and succinic acid ( 622, from Ciba Specialty Chemicals, MW = 4000); oligomers of cyanuric acid and N, N-bis (2,2,6,6-tetramethyl-4-piperidinyl) -hexamethylenediamine; poly ((6-morpholine-S-triazine-2,4-diyl) (2,2,6,6-tetramethyl-4-piperidinyl) -iminohexamethylene- (2,2,6,6-tetramethyl-4-piperidinyl) -imino) ( UV 3346, from Cytec, MW = 1600); polymethylpropyl-3-oxy-[4 (2,2,6,6-tetramethyl)-piperidinylsiloxane ( 299, from Great Lakes Chemical, MW = 1100 to 2500); copolymer of alpha-methylstyrene-N-(2,2,6,6-tetramethyl-4-piperidinyl)maleimide and N-stearylmaleimide; 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanoltetramethyl-polymer with 1,2,3,4-butanetetracarboxylic acid; etc. Still other suitable high molecular weight hindered amines are described in U.S. Pat. No. 5,679,733 to Malik et al. and U.S. Pat. No. 6,414,155 to Sassi et al., the entire contents of which are incorporated herein by reference for all purposes.

[0089] In addition to high molecular weight hindered amines, low molecular weight hindered amines can also be used in the composition. Such hindered amines are generally monomeric in nature and have a molecular weight of about 1000 or less, in some embodiments from about 155 to about 800, and in some embodiments from about 300 to about 800.

[0090] Specific examples of such low molecular weight hindered amines may include, for example, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate ( 770 from Ciba Specialty Chemicals, MW = 481); bis (1,2,2,6,6-pentamethyl-4-piperidinyl) - (3,5-di-tert-butyl-4-hydroxybenzyl) butyl-malonate; bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate; 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro-(4,5)-decane-2,4-dione, butane dioic acid-bis (2,2,6,6-tetramethyl-4-piperidinyl) ester; tetrakis-(2,2,6,6-tetramethyl-4-piperidinyl) -1,2,3,4-butane tetracarboxylate; 7-oxa-3,20-diazadispiro (5.1.11.2) heneicosane-20-propionic acid, 2,2,4,4-tetramethyl-21-oxododecyl ester ; N-(2,2,6,6-tetramethyl-4-piperidinyl)-N′-amino-oxalamide; ot-pentyl-o-(1,2,2,6,6-pentamethyl-4-piperidinyl)-monoperoxycarbonate; β-alanine N-(2,2,6,6-tetramethyl-4-piperidinyl) dodecyl ester; ethanediamide N-(1-acetyl-2,2,6,6-tetramethylpiperidinyl)-N′-dodecyl; 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidinyl)-pyrrolidine-2,5-dione; 3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidinyl)-pyrrolidine-2,5-dione; 3-dodecyl-1-(1-acetyl, 2,2,6,6-tetramethyl-4-piperidinyl)-pyrrolidine-2,5-dione, ( 3058, from Clariant, MW = 448.7); 4-benzoyloxy-2,2,6,6-tetramethylpiperidine; 1-[2-(3,5-di-tert-butyl-4-hydroxyphenylpropionyloxy)ethyl]-4-(3,5-di-tert-butyl-4-hydroxyphenylpropionyloxy)-2,2,6,6-tetramethyl-piperidine; 2-methyl-2-(2",2",6",6",6"-tetramethyl-4"-piperidinylamino)-N-(2',2',6',6'-tetra-methyl-4'-piperidinyl)propionylamide; 1,2-bis(3,3,5,5-tetramethyl-2-oxo-piperazinyl)ethane; 4-oleoyloxy-2,2,6,6-tetramethylpiperidine; and combinations thereof. Other suitable low molecular weight hindered amines are described in U.S. Pat. No. 5,679,733 to Malik et al.

[0091] Hindered amines may be used alone or in combination in any amount to achieve the desired properties, but typically comprise from about 0.01 wt. % to about 4 wt. % of the polymer composition.

[0092] UV absorbers, such as benzotriazoles or benzophenones, may be used in the composition to absorb ultraviolet light energy. Suitable benzotriazoles may include, for example, 2-(2-hydroxyphenyl)benzotriazoles, such as 2-(2-hydroxy-5-methylphenyl)benzotriazole; 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole ( UV 5411 from Cytec); 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzo-triazole; 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole; 2-(2-hydroxy-3,5-dicumylphenyl)benzotriazole; 2,2′-methylenebis(4-tert-octyl-6-benzo-triazolylphenol); 2-(2-hydroxy-3-tert-butyl-5-carboxylic acid 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-butylphenyl]benzotriazole; 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-octylphenyl]benzotriazole; 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-octylphenyl]benzotriazole; 2-[2-hydroxy-3-(2-methylacryloyloxyethyl)-5-tert-butylphenyl]benzotriazole; 2-[2-hydroxy-3-tert-butyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-butyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-amyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-butyl-5-(3-methacryloyloxypropyl)phenyl]-5-chlorobenzotriazole; 2-[2-hydroxy-4-(2-methacryloyloxymethyl)phenyl]benzotriazole; 2-[2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropyl)phenyl]benzotriazole; 2-[2-hydroxy-4-(3-methacryloyloxypropyl)phenyl]benzotriazole; and combinations thereof.

[0093] Exemplary benzophenone light stabilizers may similarly include 2-hydroxy-4-dodecyloxybenzophenone; 2,4-dihydroxybenzophenone; 2-(4-benzoyl-3-hydroxyphenoxy)ethyl acrylate ( UV 209 from Cytec); 2-hydroxy-4-n-octyloxy)benzophenone ( 531, from Cytec); 2,2′-dihydroxy-4-(octyloxy)benzophenone ( UV 314, from Cytec); hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate ( UV 2908, from Cytec); 2,2′-thiobis(4-tert-octylphenol)-n-butylamine nickel(II) ( UV 1084, from Cytec); 3,5-di-tert-butyl-4-hydroxybenzoic acid (2, -di-tert-butylphenyl) ester ( 712, from Cytec); 4,4′-dimethoxy-2,2′-dihydroxybenzophenone ( UV 12, from Cytec); and combinations thereof.

[0094] When employed, UV absorbers may comprise from about 0.01 wt. % to about 4 wt. % of the entire polymer composition.

[0095] In one embodiment, the polymer composition may contain a blend of stabilizers that produce UV resistance and color stability. The combination of stabilizers can allow the resulting product to have bright and fluorescent colors. In addition, brightly colored products can be produced without experiencing significant color decay over time. In one embodiment, for example, the polymer composition may contain a combination of a benzotriazole light stabilizer and a hindered amine light stabilizer such as an oligomeric hindered amine.

[0096] If desired, fatty acid esters may be present as lubricants. Fatty acid esters may be obtained by oxidative bleaching of crude natural wax and then esterifying the fatty acid with an alcohol. Alcohol typically has 1 to 4 hydroxyl groups and 2 to 20 carbon atoms. When alcohol is multifunctional (e.g., 2 to 4 hydroxyl groups), 2 to 8 carbon atoms are particularly desirable. Particularly suitable multifunctional alcohols may include diols (e.g., glycol, propylene glycol, butylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol and 1,4-cyclohexanediol), triols (e.g., glycerol and trimethylolpropane), tetraols (e.g., pentaerythritol and erythritol), etc. Aromatic alcohols may also be suitable, such as o-, m- and p-tolyl alcohol, chlorobenzyl alcohol, bromobenzyl alcohol, 2,4-dimethylbenzyl alcohol, 3,5-dimethylbenzyl alcohol, 2,3,5-trimethylbenzyl alcohol (cumobenzyl), 3,4,5-trimethylbenzyl alcohol, p-cuminyl alcohol, 1,2-o-phthalic alcohol, 1,3-bis(hydroxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, 1,2,4-trimethylbenzenediol, tritolyl glycol and tritolylglycerol. Particularly suitable fatty acid esters for use in the present invention are derived from montan wax. OP (Clariant), for example, contains montanic acid partially esterified with butanediol and montanic acid partially saponified with calcium hydroxide. OP contains a mixture of montanic acid esters and calcium montanic acid. Other montanic acid esters that may be used include E, OP, and WE 4 (both from Clariant), for example, montan esters obtained as by-products of oxidative refining of the raw material montan wax. E and WE 4 contains glycol or glycerol esterified montanic acid.

[0097] Other known waxes can also be used in lubricants. For example, amide waxes can be used, which are formed by reacting fatty acids with monoamines or diamines (e.g., ethylenediamine) having 2 to 18, particularly 2 to 8, carbon atoms. For example, oxalylamide waxes can be formed by the amidation reaction of ethylenediamine and fatty acids. The fatty acid can range from C 2 to C 1. 12 To C 30 , such as stearic acid (C 18 Fatty acids) to form ethylene distearate amide wax. C is commercially available from Lonza, Inc., having a discrete melt temperature of 142°C. Other oxalic acid amides include diamides formed from lauric acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, oleostearic acid, myristic acid, and undecylenic acid. Still other suitable amide waxes are N-(2-hydroxyethyl) 12-hydroxystearamide and N,N′-(ethylenebis) 12-hydroxystearamide.

[0098] In addition to the above components, the polymer composition may include various other ingredients. Operable coloring agents include any desired inorganic pigments, such as titanium dioxide, ultramarine, cobalt blue, and other organic pigments and dyes, such as phthalocyanine, anthraquinone, etc. Other coloring agents include carbon black or various other polymer soluble dyes. The amount of coloring agent that may be present in the composition is generally about 2% by weight at most.

[0099] Polymer products

[0100] The compositions of the present disclosure can be compounded and formed into polymer articles using any technology known in the art. For example, each composition can be deeply mixed to form a substantially uniform blend. The blend can be melt-kneaded at an elevated temperature, such as at a temperature higher than the melting point of the polymer used for the polymer composition but lower than the degradation temperature. Alternatively, each composition can be melted and mixed together in a conventional single or twin screw extruder. Preferably, melt mixing is carried out at a temperature ranging from 150 to 300°C, such as 200 to 280°C, such as 220 to 270°C or 240 to 260°C. However, such processing should be carried out at a desired temperature for each respective composition to minimize any polymer degradation.

[0101] After extrusion, the composition can be formed into pellets. The pellets can be molded into polymer articles by techniques known in the art, such as injection molding, thermoforming, blow molding, rotational molding, etc. According to the present disclosure, the polymer article shows excellent friction behavior and mechanical properties. Thus, the polymer article can be used for several applications of expecting low wear and excellent sliding properties.

[0102] Polymer articles include any moving article or molded article that contacts another surface and may require high friction requirements. For example, polymer articles include articles used in the automotive industry, particularly housings, latches, such as rotary latches, window winding systems, wiper systems, pulleys, sunroof systems, seat adjustment systems, levers, bushings, gears, gear boxes, claws, pivot housings, wiper arms, brackets or seat track bearings, zippers, switches, cams, rollers or rolling guides, sliding elements or slides, such as sliding plates, conveyor belt components, such as chain elements and links, casters, fasteners, levers, conveyor system wear strips and guardrails, medical equipment, such as medical inhalers and syringes. Almost unlimited types of polymer articles can be formed from the polymer compositions of the present disclosure.

[0103] In one embodiment, the composition of the present disclosure is used to produce a first sliding member and a second sliding member. The first and second sliding members can both be formed by compositions according to the present disclosure. In particular, the first sliding member and the second sliding member can be made of a composition comprising a combination of a reinforced polyester polymer and an ultra-high molecular weight organosilicon and an optional fluoropolymer. In each composition, the relative amounts of the components can be the same or can be different.

[0104] The first sliding member and the second sliding member can be included in the device and placed in operative association with each other so that the sliding members move relative to each other. For example, in one embodiment, the first sliding member can be stationary while the second sliding member moves on the first sliding member. Alternatively, the two sliding members can move while in contact with each other.

[0105] In one embodiment, the sliding member of the present disclosure can be used to produce a medical product. For example, referring to Figure 1 , shows an inhaler 20. Inhaler 20 comprises a shell 22 attached to a mouthpiece 24. Operationally associated with the shell 22 is a plunger 26 for receiving a tank containing a composition to be inhaled. The composition may include sprays or powders. Inhaler 20 may include a first sliding member operationally associated with a second sliding member. For example, in certain embodiments, the shell 22 may include the first sliding member, and the plunger 26 may include the second sliding member simultaneously. Alternatively, the first sliding member may include the shell 22 and the second sliding member may include the mouthpiece 24. In another embodiment again, an internal sliding member may be contained in the shell 22, sliding relative to the shell.

[0106] In use, the inhaler 20 applies a metered dose of a drug, such as an asthma drug, to a patient. The asthma drug may be suspended or dissolved in a propellant, or may be contained in a powder. When the patient activates the inhaler to breathe the drug, the valve opens to allow the drug to leave the mouthpiece.

[0107] In another embodiment of the present disclosure, the first sliding member and the second sliding member are included in a medical syringe 30, such as Figure 2 . The medical syringe 30 includes a housing 32 operatively associated with a plunger 34. The housing 32 or a first sliding member can slide relative to the plunger 34 or a second sliding member. The medical syringe 30 can be spring loaded. The medical syringe 30 is used to inject medication into a patient, typically into the thigh or buttocks. The medical syringe can be needle-free or can contain a needle. When a needle is contained, the needle tip is typically shielded within the housing before injection. On the other hand, a needle-free syringe can contain a pressurized gas cartridge that pushes the medication into the skin without the use of a needle.

[0108] performance

[0109] The polyester polymer compositions and polymer articles produced therefrom according to the present disclosure have improved friction properties. According to the present disclosure, friction properties are generally measured by the coefficient of friction.

[0110] Generally, static friction is the friction between two or more surfaces that are not moving relative to each other (i.e., both objects are stationary). Generally, dynamic friction occurs when two objects are moving relative to each other (i.e., at least one object is in motion or reciprocating motion). In addition, stick-slip is generally known as a phenomenon that results from a continuous alternation between static friction and dynamic friction.

[0111] According to the present disclosure, the compositions and polymeric articles can exhibit a kinetic coefficient of friction relative to another surface measured according to VDA 230-206 of less than about 0.08, such as less than about 0.07, such as less than about 0.06, such as less than about 0.05.

[0112] In one embodiment, the above values ​​of the coefficient of kinetic friction and the effect of sliding speed on the coefficient of kinetic friction are shown between the composition or polymeric article and various counter materials. For example, the above values ​​can be shown between the composition or polymeric article and the same composition or article.

[0113] The counter material may also include a polycarbonate polymer composition containing 20 weight percent glass fibers and 15 weight percent polytetrafluoroethylene particles. In another embodiment, the counter material includes a polybutylene terephthalate composition containing 20 weight percent glass fibers and 15 weight percent polytetrafluoroethylene particles.

[0114] While the polymer compositions of the present disclosure and polymer articles produced therefrom provide improved frictional properties, the compositions and articles may also exhibit improved mechanical properties. For example, the tensile modulus of the composition or polymer article, as measured according to ISO Test No. 527, may be greater than about 7000 MPa, such as greater than about 7200 MPa, such as greater than about 7500 MPa, and generally less than about 15,000 MPa, such as less than about 10,000 MPa.

[0115] The composition may have a stress at break of generally greater than about 100 MPa, such as greater than about 110 MPa, such as greater than about 115 MPa, such as greater than about 120 MPa and generally less than about 180 MPa. The strain at break may generally be greater than about 2.0%, such as greater than about 2.5%, and generally less than about 4%. The composition may exhibit a notched impact strength of greater than about 6 kJ / m when tested at 23°C. 2 , for example, greater than about 8 kJ / m 2 , for example, greater than about 9 kJ / m 2 and usually less than about 20 kJ / m 2 , for example, less than about 15 kJ / m 2 .

[0116] The present disclosure may be better understood with reference to the following examples. Example

[0117] The following examples are given by way of illustration and not by way of limitation.The following experiments were performed to demonstrate some of the benefits and advantages of the present invention.

[0118] Various polymer compositions containing glass fibers and friction modifiers were formulated and tested for friction characteristics and physical properties. Each composition contained glass fibers and polybutylene terephthalate polymer in an amount of 22% by weight. Ultrahigh molecular weight silicone was then added to the composition along with different carriers. In one embodiment, for example, the carrier is silica particles. However, in other embodiments, the carrier is a polycarbonate polymer or a thermoplastic polyester elastomer. Some compositions also contained 5% by weight polytetrafluoroethylene particles. One formulation contained only polytetrafluoroethylene particles as a friction modifier.

[0119] The components of each respective composition were mixed together and compounded using a ZSK 25MC (Werner & Pfleiderer, Germany) twin-screw extruder. The screw configuration with kneading elements was selected to allow for effective and thorough mixing of the components. The composition was extruded and pelletized. The pellets were dried at 120°C for 8 hours and then injection molded.

[0120] The compositions / moldings were tested for various friction and physical properties.

[0121] In this example, the friction properties of various compositions were measured.

[0122] A stick-slip test was carried out to determine the dynamic friction coefficient. The stick-slip test was carried out in accordance with VDA 230-206. A ball-on-plate configuration was used with a load of 30 N, a sliding speed of 8 mm / s and a test duration of 1000 cycles.

[0123] The composition formulated according to the present disclosure was formed into a plate for dynamic friction coefficient testing. In the first set of experiments, the composition was tested against a ball made of a polycarbonate polymer containing 20% ​​by weight glass fibers and 15% by weight polytetrafluoroethylene particles. The following results were obtained:

[0124] Table 1

[0125]

[0126] In a second set of experiments, balls were made from a polymer composition containing a polybutylene terephthalate polymer in combination with 20% by weight of glass fibers and 15% by weight of polytetrafluoroethylene particles. The following results were obtained:

[0127] Table 2

[0128]

[0129] In a third set of experiments, the balls were made from the same polymer composition. The following results were obtained:

[0130] Table 3

[0131]

[0132]

[0133] The composition was also tested for physical properties. Tensile properties were tested according to ISO test 527:2012. Charpy notched impact strength was tested according to ISO test 179-1:2010. The test was run using a Type A notch (0.25 mm base radius) and Type 1 specimen dimensions (80 mm long, 10 mm wide, 4 mm thick). The test was conducted at a temperature of 23°C. The following results were obtained:

[0134] Table 4

[0135]

[0136] These and other modifications and variations of the present invention may be implemented by those of ordinary skill in the art without departing from the spirit and scope of the present invention, which are set forth in the appended claims. In addition, it should be understood that the aspects of the various embodiments may be interchangeable in whole or in part. In addition, it will be appreciated by those of ordinary skill in the art that the foregoing description is by way of example only, and not for the purpose of limiting the present invention as further described in the appended claims.

Claims

1. A medical device comprising a first sliding member operatively associated with a second sliding member, the first sliding member and the second sliding member being configured to remain in contact and move relative to each other, at least one of the sliding members comprising a molded polymer article made of a polymer composition comprising: a polyester polymer comprising a polybutylene terephthalate polymer alone or in combination with a polyethylene terephthalate polymer, the polybutylene terephthalate polymer being present in the polymer composition in an amount greater than 60% by weight; optional reinforcing fibers present in the polymer composition in an amount of 5% to 35% by weight; and A masterbatch comprising a first friction modifier dispersed in a carrier polymer, the first friction modifier comprising a dynamic viscosity greater than 100,000 mm 2 s- 1 The ultra-high molecular weight silicone is present in the polymer composition in an amount of 0.5 wt % to 6 wt %, and the ultra-high molecular weight silicone is present in the masterbatch in an amount of 35 wt % to 60 wt %, wherein the carrier polymer comprises a polyester elastomer.

2. The medical device of claim 1, wherein the medical device is an inhaler. 3 . The medical device of claim 2 , wherein the first sliding member is a housing and the second sliding member is a plunger.

4. The medical device of claim 1, wherein the medical device is a syringe.

5. The medical device of claim 4, wherein the first sliding member is a housing and the second sliding member is a plunger.

6. A polymer composition comprising: A polyester polymer comprising a polybutylene terephthalate polymer alone or in combination with a polyethylene terephthalate polymer or a polycarbonate polymer; reinforcing fibers present in the polymer composition in an amount of 5 wt % to 55 wt %; and A masterbatch comprising a first friction modifier, wherein the first friction modifier comprises a dynamic viscosity greater than 100,000 mm 2 s- 1 An ultra-high molecular weight silicone, the ultra-high molecular weight silicone is dispersed in a carrier polymer, the carrier polymer comprises a polyester elastomer, and wherein the ultra-high molecular weight silicone is present in the polymer composition in an amount of 0.1 wt.% to 3 wt.%, and wherein the polymer composition exhibits a dynamic friction coefficient of less than 0.06 according to VDA 230-206 at a speed of 8 mm / s and a load of 30 N when tested against itself. The polymer composition according to claim 6 , wherein the ultra-high molecular weight silicone is polydimethylsiloxane.

8. The polymer composition of claim 6, wherein the composition comprises a second friction modifier.

9. The polymer composition of claim 8, wherein the second friction modifier comprises polytetrafluoroethylene.

10. The polymer composition of claim 9, wherein the polyester polymer is present in the composition in an amount of 50 to 90 weight percent, the reinforcing fibers comprise glass fibers and are present in the polymer composition in an amount of 5 to 30 weight percent, the ultra-high molecular weight silicone is present in the composition in an amount of 0.5 to 3 weight percent, and the polytetrafluoroethylene is present in the polymer composition in an amount of 1 to 20 weight percent.

11. The polymer composition of claim 6, wherein the composition is isocyanate-free.

12. The polymer composition according to claim 6, wherein the polymer composition exhibits a dynamic friction coefficient according to VDA 230-206 of less than 0.08 at a speed of 8 mm / s, under a load of 30 N and after 1,000 cycles when tested against a polycarbonate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers, or when tested against a polybutylene terephthalate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers.

13. The polymer composition of claim 6, wherein the polymer composition exhibits a dynamic coefficient of friction according to VDA 230-206 of less than 0.07 at a speed of 8 mm / s, under a load of 30 N and after 1,000 cycles when tested against a polycarbonate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers, when tested against a polybutylene terephthalate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers, or when tested against itself.

14. The polymer composition of claim 6, wherein the polymer composition exhibits a dynamic coefficient of friction according to VDA 230-206 of less than 0.05 at a speed of 8 mm / s, under a load of 30 N and after 1,000 cycles when tested against a polycarbonate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers, when tested against a polybutylene terephthalate containing 15 wt. % polytetrafluoroethylene and 20 wt. % glass fibers, or when tested against itself.

15. The polymer composition of claim 6, wherein the reinforcing fibers comprise glass fibers, the glass fibers being present in the polymer composition in an amount of 10 to 30 weight percent.

16. The polymer composition of claim 6, wherein the composition exhibits a Charpy notched impact strength at 23°C greater than 9 kJ / m 2 .

17. A molded article made from the polymer composition according to claim 6.

18. The molded article of claim 17, wherein the molded article comprises a medical device.

19. An apparatus comprising: A first sliding member operatively associated with a second sliding member, the first sliding member and the second sliding member being configured to maintain contact and move relative to each other, at least one of the sliding members comprising a molded polymer article made from the polymer composition according to any one of claims 6-16.

20. The device according to claim 19, wherein the first sliding member and the second sliding member are both made of the polymer composition according to any one of claims 6-16.

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