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  Toughened polyester compositionsUSPTO Application #: 20060157350Title: Toughened polyester compositions Abstract: Toughened polyester compositions containing specified amounts of certain reinforcing fillers, a polymeric toughening agent, and sepiolite-type clay, in which the sepiolite is added before or during polymerization to form the polyester, are especially useful for parts which have appearance surfaces and/or are painted. Such compositions are useful for items such as appliance parts, automotive body panels, power tool housing, and electronics housings. Processes for coating such compositions are also described. (end of abstract) Agent: E I Du Pont De Nemours And Company Legal Patent Records Center - Wilmington, DE, US Inventors: David T. Williamson, Gregory R. Alms, Michael T. Pottiger, Alan D. English USPTO Applicaton #: 20060157350 - Class: 204471000 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Electrophoresis Or Electro-osmosis Processes And Electrolyte Compositions Therefor When Not Provided For Elsewhere, Coating Or Forming Of Object The Patent Description & Claims data below is from USPTO Patent Application 20060157350. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of piority of U.S. Provisional Application No. 60/638,225, filed Dec. 22, 2004, U.S. Provisional Application No. 60/686,675, filed Jun. 2, 2005, U.S. Provisional Application No. 60/686,728, filed Jun. 2, 2005, U.S. Provisional Application No. 60/686,847, filed Jun. 2, 2005, U.S. Provisional Application No. 60/686,689, filed Jun. 2, 2005, U.S. Provisional Application No. 60/686,707, filed Jun. 2, 2005, U.S. Provisional Application No. 60/686,708, filed Jun. 2, 2005. FIELD OF THE INVENTION [0002] A polyester composition comprising specified amounts of certain reinforcing agents, sepiolite-type clay, and a toughening agent is useful for making parts requiring a smooth surface, for instance, for automotive body panels and appliance parts such as handles and housings. The sepiolite-type clay is added to the polyester forming ingredients before or during the polymerization. TECHNICAL BACKGROUND [0003] One of the challenges in replacing metal parts with plastics is producing plastic parts with good looking (smooth) surfaces, and/or whose surfaces can be coated (painted) to have a glossy smooth appearance. This, often coupled with the need for certain minimum levels of toughness and/or heat resistance, has presented a challenge, especially in using polymers and other ingredients that are relatively inexpensive. Thermoplastics of various types have been tried in such applications, and have been successfully used in some instances, and have the advantage of being reusable (for example scrap) and often are tougher than thermoset polymers. However in uses where high resistance to two or more environmental stresses are needed, improved compositions are still needed. [0004] For instance, a particularly challenging type of part is an automotive body panel, such as fenders, hoods, doors, lift-up tailgates, trunk lids, tank caps, bumpers, protective moldings, side panels, body sills, mirror housings, handles, spoilers, gas tank flap covers, and hub caps. These parts must be precisely molded to close dimensional tolerances so they will fit properly on the automobile, they must be tough enough to resist mechanical/impact damage, and they must have a very smooth surface so (usually) when they are painted they have a good surface appearance (sometimes called a "Class A" surface). In addition it is preferred that they have enough heat resistance so that they can withstand the temperatures (sometimes as high as 200.degree. C., and for as long as 30 minutes) in an automotive paint bake oven without excessively sagging, warping, or otherwise deforming. While these parts can be painted separately at lower temperatures and then later attached to the body after painting (so called off line painting) such a process adds significant cost to the vehicle assembly process, and it is preferred from an economic standpoint to paint these parts on the regular paint line. Color matching of parts painted in two different processes may be difficult. These parts also need to have a minimum level of stiffness and fatigue resistance to stresses that are repeatedly encountered in normal use. [0005] Other appearance parts may not require this extreme temperature resistance, but often require the other attributes mentioned above. [0006] More particularly for automotive vehicles [passenger cars, trucks, snowmobiles, construction vehicle, farm equipment vehicle (such as a tractor or combine), etc.] external appearance, for example with respect to color tone, gloss and/or short-wave and long-wave structure, the surfaces of the coated plastic parts for the observer should not differ, or should differ only slightly from the coated metal surfaces of a car body. This applies, in particular, to plastic parts, such as fenders, bonnets, boot lids, doors or body sills which are constructed with as small a joint width as possible to and in particular also in the same plane as adjacent metal parts, since visual differences are particularly striking there. [0007] There are three different approaches to the production of coated car bodies assembled from metal and plastic parts in a mixed construction: [0008] 1. The method known as the off-line process, in which the metal car body and the plastic parts are coated separately and then assembled. [0009] The drawback of the off-line process is its susceptibility to lack of visual harmonization of the coated metal and plastic surfaces, at least in cases where coated plastic parts and coated metal parts are subjected to direct visual comparison for reasons of construction, for example, owing to the virtually seamless proximity of the coated parts and/or arrangement of the coated parts in one plane. [0010] A further drawback is the necessity of operating two coating lines. [0011] 2. The method known as the in-line process in which the metal body already provided with an electrodeposition coating as a primer and the uncoated plastic parts or the plastic parts optionally only provided with a plastic primer are assembled and provided with one or more further coating layers in a subsequent common coating process. [0012] The drawback of the in-line process is the assembly step inserted into the coating process as an interruptive intermediate step which also involves the risk of introducing dirt into the further coating process. [0013] 3. The method known as the on-line process, in which the uncoated body parts made of metal and the uncoated plastic parts or the plastic parts optionally only provided with a plastic primer are assembled into a body constructed in a mixed construction and then passed through a common coating process including electrodeposition coating, wherein naturally only the electrically conductive metal parts are provided with an electrodeposition coating, while all the coating layers to be applied subsequently are applied both to the electrodeposition coated metal parts and to the plastic parts. [0014] The on-line process is particularly preferred as it clearly separates the body base shell construction and the coating process and allows an undisturbed coating sequence. [0015] Basically only adequately heat-resistant and simultaneously heat deformation-resistant plastics materials are suitable for the particularly preferred on-line process, since high temperatures are used in the drying of the electrodeposition coating. [0016] Plastic parts made of previously available fiber-reinforced thermoplastics, for example, are at best conditionally suitable, since the coated surfaces do not have an adequate high visual harmonization with the coated metal surfaces and, in particular, are not up to the high standards required by car manufacturers. [0017] Polymer-layered silicate nanocomposites incorporate a layered clay mineral filler in a polymer matrix. In other words these are compositions in which nanosized particles are dispersed in a polymeric matrix. Layered silicates are made up of several hundred thin platelet layers stacked into an orderly packet known as a tactoid. Each of these platelets is characterized by large aspect ratio (diameter/thickness on the order of 100-1000). Accordingly, when the clay is dispersed homogeneously and exfoliated as individual platelets throughout the polymer matrix, dramatic increases in strength, flexural and Young's modulus, and heat distortion temperature are observed at very low filler loadings (<10% by weight) because of the large surface area contact between polymer and filler. [0018] Nanocomposites have enjoyed increased interest since the initial development of nylon-based material at Toyota Motor Corporation in the later 1980's and early 1990's; see, e.g., Usuki, A., et al., Journal of Materials Research, 8(5), 1179-1184, (1993) and M. Kawasumi, Journal of Polymer Science: Part A: Polymer Chemistry, 42, 819-824 (2004). Attempts to generate nanocomposites in a thermoplastic polyester matrix, however, have been only marginally successful. [0019] U.S. Pat. No. 5,965,655 describes compositions containing thermoplastics such as polyalkylene terephthalates and fillers such as wollastonite having specified particles size ranges which can have "Class A" surfaces. Specific compositions also containing exfoliated sepiolite-type clay, and/or toughening agents are not disclosed. [0020] U.S. Pat. No. 4,753,980 describes polyester compositions containing certain toughening agents. The use of exfoliated sepiolite-type clay is not mentioned in the patent. [0021] Published U.S. Patent Application 20050260361 describes certain polyester compositions suitable for appearance parts and methods for making the compositions. Sepiolite is not mentioned. Continue reading... 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