| Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics -> Monitor Keywords |
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Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplasticsRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Natural Rubber Compositions Having Nonreactive Materials (dnrm) Other Than: Carbon, Silicon Dioxide, Glass Titanium Dioxide, Water, Hydrocarbon, Halohydrocarbon, Ethylenically Unsaturated Reactant Admixed With A Preformed Reaction Product Derived From: (a) At Least One Polycarboxylic Acid, Ester, Or Anhydride; (b) At Least One Polyhydroxy Compound; And (c) At Least One Fatty Acid Glycerol Ester, Or A Fatty Acid Or Salt Derived From A Naturally Occurring Glyceride, Tall Oil, Or A Tall Oil Fatty Acid, At Least One Solid Polymer Derived From Ethylenic Reactants Only, With Saturated -n=c=x (x Is Chalcogen) Reactant Or Polymer Thereof; Or With Solid Copolymer Derived From At Least One -n=c=x Reactant Wherein At Least One Of The Reactants Forming The Solid Copolymer Is Saturated; Or With Spfi Wherein At Least One Of The Necessary Ingredients Contains A -n=c=x Group Or With A Reaction Product Thereof; Or With Sicp Containing A -n=c=x Group, Contacting With A -n=c=x-containing Reactant Which Has Been Previously Reacted With An Organic Compound Containing A Hydroxyl, Amine, Or -c(=o)-o- GroupDynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070060707, Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10/463,801 filed on Jun. 17, 2003, the disclosure of which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to thermoprocessable compositions containing cured polyurethane elastomers. It also relates to seal and gasket type material made from the compositions and methods for their production by dynamic vulcanization techniques. BACKGROUND OF THE INVENTION [0003] Cured elastomeric materials have a desirable set of physical properties typical of the elastomeric state. They show a high tendency to return to their original sized and shape following removal of a deforming force, and they retain physical properties after repeated cycles of stretching, including strain levels up to 1000%. Based on these properties, the materials are generally useful for making shaped articles such as seals and gaskets. [0004] Because they are thermoset materials, cured elastomeric materials can not generally be processed by conventional thermoplastic techniques such as injection molding, extrusion, or blow molding. Rather, articles must be fashioned from elastomeric materials by high temperature curing and compression molding. Although these and other rubber compounding operations are conventional and known, they nevertheless tend to be more expensive and require higher capital investment than the relatively simpler thermoplastic processing techniques. Another drawback is that scrap generated in the manufacturing process is difficult to recycle and reuse, which further adds to the cost of manufacturing such articles. [0005] Articles made from elastomeric materials, such as seals and gaskets, may be subject to a wide variety of challenging environmental conditions, including exposure to high temperature, contact with corrosive chemicals, and high wear conditions during normal use. For example, bearing seals for automotive applications see high temperature in normal use and are exposed to lubricating fluids containing basic compounds and other corrosive materials. They are also subject to wear and abrasion from the moving parts they act to seal. Accordingly, it is desirable to make such articles from materials that combine elastomeric properties and stability or resistance to the environmental conditions. [0006] Crosslinked polyurethane materials have excellent physical properties, such as high tensile strength and wear resistance, compared with other cross linked elastomeric materials. However, they are usually limited to a continuous service temperature of only up to about 100.degree. C. In some applications, the relatively low heat resistance of the polyurethane materials is a drawback that narrows the potential use of the materials. For example, they are generally unsuitable for use in some automotive applications, where the in service use can be 150.degree. C. or higher. [0007] It would therefore be desirable to provide materials having excellent physical properties in combination a high level of heat resistance. In addition, it would be desirable to provide such materials that are readily recyclable and that can be processed by conventional thermoplastic processing techniques. SUMMARY OF THE INVENTION [0008] A thermoplastically processable cured rubber composition comprises a crosslinked or cured urethane polymer dispersed in a matrix. The matrix is made of a thermoplastic polymeric material, and the composition may be processed into an article with a tensile strength that exceeds the tensile strength of the thermoplastic polymeric material. In one aspect, the matrix forms a continuous phase and the crosslinked urethane polymer is in the form of particles forming a non-continuous phase. [0009] The processable rubber compositions can be made by a process of dynamic vulcanization of a urethane prepolymer material in the presence of the thermoplastic matrix material. In one aspect, the method involves combining a urethane prepolymer, a curing agent capable of reacting with the urethane prepolymer, and a thermoplastic material to form a mixture, and heating the mixture at a temperature and for a time sufficient to effect reaction between the curing agent and the prepolymer. Mechanical energy is supplied to the mixture during the heating step so that the crosslinking or curing of the urethane prepolymer occurs while the prepolymer and thermoplastic are undergoing a mixing. [0010] In a preferred embodiment, the method involves mixing the prepolymer and thermoplastic material for a time and at a shear rate sufficient to form a dispersion of the prepolymer in a continuous thermoplastic phase. A dispersion of prepolymer in thermoplastic is formed, wherein the prepolymer particles are preferably about 50 micrometers in diameter or less. When a proper dispersion is formed, a curing agent is added to the dispersion while continuing the mixing, and the mixture is heated while continuing the mixing. [0011] The processable compositions may be formed into cured elastomeric materials useful for example as gaskets, seals, O-rings, and hoses. Advantageously, the compositions may be processed by standard thermoplastic techniques such as blow molding and compression molding, avoiding the use of slow thermoset and possibly high temperature rubber processing conditions. Scrap material generated during the manufacture of the shaped articles may be readily recycled and reused, because the material can be processed as a conventional thermoplastic. [0012] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0013] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. [0014] The invention provides a thermoplastically processable rubber composition, shaped articles made from the rubber composition, and methods for compounding the rubber composition and forming the shaped article. The processable rubber composition contains a crosslinked urethane polymer dispersed in a matrix, wherein the matrix comprises a thermoplastic polymeric material. The rubber compositions of the invention can be formed into articles that exhibit desirable elastomeric properties, yet can also be processed by standard thermoplastic methods such as injection molding, blow molding, and extrusion. [0015] According to one aspect of the invention, the matrix forms a continuous phase in which the crosslinked urethane polymer is in the form of particles forming a non-continuous or discrete phase. In another aspect, the matrix thermoplastic polymeric material and the crosslinked urethane polymer form co-continuous phases. [0016] The rubber compositions of the invention are prepared by reacting a urethane prepolymer (also called a "polyurethane prepolymer") with a curing agent while stirring or otherwise mechanically mixing the prepolymer and curing agent in the presence of a thermoplastic polymeric material. The thermoplastic material comprises a polymeric material that softens and flows upon heating. The prepolymer reacts with the curing agent to form the crosslinked urethane polymer of the invention. The prepolymer is generally a polymer of a polyisocyanate and a polyol and/or polyamine. It may be isocyanate-functional or hydroxyl-functional, and can have a wide variety of molecular weights and chemical structure, according to the desired properties of the rubber composition, as discussed below. [0017] A preferred method for making rubber compositions comprises the steps of combining a urethane prepolymer, a curing agent capable of reacting with the urethane prepolymer, and a thermoplastic material to form a mixture, and heating the mixture at a temperature and for a time sufficient to effect a reaction between the curing agent and the prepolymer, while supplying mechanical energy to mix the mixture during the heating step. [0018] In another aspect, the preparation of the rubber compositions is carried out by mixing the prepolymer and the thermoplastic material in the presence of the curing agent, and heating during the mixing to effect cure of the prepolymer in the presence of the thermoplastic material. In yet another aspect, the method comprises mixing the prepolymer and the thermoplastic material for a time and at a shear rate sufficient to form a dispersion of the prepolymer in a continuous thermoplastic phase. When a proper dispersion is formed, the curing agent may be added to the dispersion while continuing the mixing. The combination of the prepolymer, curing agent, and thermoplastic material is then heated during mixing. During the mixing and heating, the prepolymer and curing agent react to form a crosslinked urethane polymer. [0019] Shaped elastomeric articles may be readily prepared from the rubber compositions of the invention by conventional thermoplastic processing methods. The shaped elastomeric materials contain a crosslinked urethane polymer dispersed in a matrix made of a thermoplastic polymeric material. The shaped elastomeric articles exhibit a desirable combination of properties such as flexibility, softness, and compression set. In one embodiment, the shaped articles are especially suitable for such application as seals, gaskets, and O-rings, as well as extruded articles such as hoses. Continue reading about Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics... Full patent description for Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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