Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1997-12-15
2001-07-17
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S059000, C528S061000, C528S063000, C528S067000, C528S075000, C528S085000, C528S905000
Reexamination Certificate
active
06262217
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polyurethane compositions and more particularly to two-component polyurethane compositions.
BACKGROUND OF THE INVENTION
Resorcinol-formaldehyde-latex (RFL) based adhesives are widely used to adhere textile substrates, such as fabrics and multifilament cords, to an elastomer, particularly in the tire, belt, and similar industries. RFL adhesives can be formulated to adhere to a variety of textile substrates and elastomers. RFL adhesives also can exhibit low glass transition temperature (low T
g
), high thermal resistance, flexibility, and other properties desirable in belt structures and in similar applications. Despite these and other advantages of RFL adhesives, there can be environmental concerns associated with RFL adhesives.
Polyurethane compositions can be useful in rubber-to-fabric adhesive applications. See I. Skiest, “Handbook of Adhesives” (Chapman & Hall 1990), page 366. For example, Skiest discusses liquid isocyanate-terminated prepolymers prepared from diisocyanates and a polybutadiene glycol useful as a rubber-fabric adhesive. Other patents and articles discuss polyurethane compositions prepared from hydroxyl-terminated polybutadienes for various applications, such as elastomers, molded products, and the like. See U.S. Pat. No. 3,055,952 to Goldberg; U.S. Pat. No. 3,175,997 to Hsieh; U.S. Pat. No. 3,674,743 to Verdol, et al.; U.S. Pat. No. 4,507,430 to Shimada, et al.; U.S. Pat. No. 5,486,570 to St. Clair; Japanese Patent Application No. 59/210928; see also B. B. Idage et al., J.App.Poly.Sci. 28, 3559-3563 (1983); M. Zachariasiewicz, “Poly BD Resins: High Performance Materials for Encapsulants and Sealants,” ASE Proceedings 1985; Arco Chemical Co. General Bulletin titled “Poly BD Resins: Functional Liquid Polymers” (1978); N. S. Schneider et al., Advances in Urethane Science & Technology 8:49-74 (1981); and P. W. Ryan, J. Elastoplastics 3:57-71 (1971).
Typically, however, such compositions can exhibit certain properties to the exclusion of other desired characteristics. For example, a particular composition can have good dynamic mechanical properties, such as low heat generation, but suffer poor adhesion properties, or other desired properties.
SUMMARY OF THE INVENTION
The present invention provides polyurethane compositions which exhibit several desirable properties. The compositions can exhibit a flat (stable) modulus response over a broad range of temperatures. The compositions also can have desirably low glass transition temperature (T
g
) and high temperature stability. Thus the compositions can be useful over a broad range of temperatures. The compositions also can exhibit good flexibility and good dynamic mechanical properties, such as low G″ (low heat generation). In addition, the compositions of the present invention are formaldehyde-free, and thus can be environmentally acceptable. Still further, the composition can have low viscosity at room and elevated temperature, which can be useful in various applications.
The polyurethane compositions of the invention are particularly useful as an impregnating bonding agent for textile substrates, such as fabrics and multifilament cords. The composition preferably has a sufficiently low viscosity upon application so that it can readily penetrate into and achieve good bonding of individual filaments of a textile substrate to one another to provide a coherent structure. Good inter-ply adhesion can be achieved without adversely affecting the desired flexibility of the cord, due to the flexible nature of the composition. The resultant bonded cord can in turn can be adhered to vulcanizable elastomeric rubbers to provide a composite structure useful in tires, belts, and the like. The polyurethane compositions are also useful in other applications, such as cast polyurethane products, flexible composites, elastomeric/metal constructions, and the like.
The polyurethane compositions of the invention include a polyurethane prepolymer formed of a mixture of isocyanate-terminated (or capped) polyalkadienes of varying molecular weights. The majority component of the polyurethane prepolymer is an isocyanate-terminated polyalkadiene prepared by capping a hydroxy-terminated polyalkadiene with isocyanate. The isocyanate caps the hydroxyl groups of the polyalkadiene to form urethane linkages. The majority component is characterized as having a molecular weight sufficient to impart the desirable properties of the polyalkadiene component thereof to the polyurethane composition, such as low T
g
, flexibility, and the like. The minority component has a molecular weight suitable to increase isocyanate levels sufficient to impart the desired degree of adhesion.
The majority component of the polyurethane prepolymer is preferably an isocyanate-terminated polyalkadiene prepared by capping a hydroxy-terminated polyalkadiene having a molecular weight from about 1500 to about 5000, preferably at least about 2000, grams per mol (g/mol) with isocyanate. The polyurethane prepolymer also includes at least one additional isocyanate-terminated polyalkadiene prepared by capping hydroxy-terminated polyalkadiene having a molecular weight from about 500 to about 1500, preferably at least about 1000, g/mol with isocyanate.
The polyurethane compositions of the invention also include a curative component, such as an aromatic diamine compound. Typically, the polyurethane prepolymer component and the curative component are stored separately and combined prior to use.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethane compositions of the invention include the reaction product of a polyurethane prepolymer component and a curative component. The polyurethane prepolymer component includes a blend of isocyanate-terminated polyalkadienes. As used herein, the term “hydroxy-terminated polyalkadiene” refers to hydroxy-terminated homopolymers of conjugated dienes, such as butadiene, isoprene, and copolymers thereof. The hydroxy-terminated polyalkadiene can be saturated or unsaturated. The saturated versions of hydroxy-terminated polyalkadienes can provide improved oxidation resistance.
The prepolymer component includes about 50 to about 99 percent by weight, preferably about 75 to about 95 percent by weight, based on the total weight percent of the prepolymer component, of an isocyanate-terminated polyalkadiene prepared by capping a hydroxy-terminated polyalkadiene having a number average molecular weight from about 1500 to about 5000, preferably at least about 2500, grams per mol (g/mol) with isocyanate. The prepolymer also includes about 1 to about 50 percent by weight, preferably about 5 to about 25 percent by weight, based on the total weight of the prepolymer, of at least one other isocyanate-terminated polyalkadiene prepared by capping a hydroxy-terminated polyalkadiene having a molecular weight number average from about 500 to about 1500, preferably at least about 1000, g/mol with isocyanate.
Generally, the polyalkadienes are terminated with hydroxyl groups and can have a hydroxyl functionality of about 1.5 to about 3. The hydroxy-terminated polyalkadienes can be non-hydrogenated (i.e., have a hydrogen saturation degree of carbon to carbon double bonds in the hydroxy-terminated polyalkadiene of less than about 50%). Saturated polyalkadienes having a hydrogen saturation degree of at least about 80%, and higher, and mixtures of saturated and unsaturated compounds can also be used. The saturated polyalkadienes can impart additional advantageous properties, such as increased UV and oxidation resistance. The polyalkadienes can be saturated using techniques known in the art, for example, by subjecting the polyalkadiene to hydrogenation reaction in the presence of a catalyst such as nickel, vanadium, or Raney nickel.
The hydroxyl groups of the hydroxy-terminated polyalkadienes are capped with isocyanate functional groups using suitable diisocyanate compounds known in the art, including aliphatic, cycloaliphatic and aromatic diisocyanates. Preferably, the diisocyanate is a symmetric diisocyanate. Exemplar
Diwanji Ashish P.
Tallmadge Jack N.
Weih Mark A.
Wilhem Walter C.
Dearth Miles B.
Lord Corporation
Rupert Wayne W.
Sergent Rabon
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