Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-06-07
2001-08-21
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C522S093000, C522S107000, C522S137000, C525S036000, C525S038000, C525S039000, C526S347000
Reexamination Certificate
active
06277939
ABSTRACT:
BACKGROUND OF THE INVENTION
Unsaturated polyester resins are polycondensation products of a dicarboxylic acid with dihydroxy alcohols. Such polyester resins catalyze to cure or harden, generally at room temperatures, to make a wide variety of products. Unsaturated polyester resins are widely used today to make products for use in the marine, transportation and building industries, and in particular, fiber or particulate reinforced products, such as glass fiber reinforced laminate-type products. Unsaturated polyester resins generally contain ethylenic unsaturation introduced by the employment of unsaturated diacids, thus comprising thermosetting-type resins. As such, unsaturated resins generally employ maleic and fumaric unsaturated acids, although saturated acids, phthalic and adipic acid may also be included to control or reduce the amount of unsaturation in the final unsaturated polyester resin and to control the physical properties. Dihydroxy alcohols most generally used are typically ethylene, propylene, diethylene and dipropylene glycols. Cross-linking agents may be employed with the unsaturated polyester resins. Generally, styrene monomers and diallyl phthalate are the most common crosslinking agents. The styrene monomers are used to reduce the viscosity of the polyester resin and to act also as a cross-linker in the polyester resins.
It is desirable, particularly in view of the toxicity of the styrene monomer and government regulations, to reduce the concentration levels of the styrene monomer from the usual 40% to 50% by weight of the polyester resin to below 35% or 30% by weight. However, reductions in styrene monomer concentrations present problems in the polyester resins with the increased viscosity of the resin, causing difficulties in applying the resins, such as causing spray problems and glass roll-out when the resin is sprayed or used in conjunction with glass fibers. The reduced styrene monomer polyester resin does not wet the glass in preparing glass fiber laminates, and therefore, the surface of the sprayed glass fiber polyester resin typically must be contacted with a roller to prevent glass fibers from sticking out of the surface. In addition, the physical properties of the styrene monomer-reduced polyester resins are also greatly reduced without the use of additional, supplemental cross-linkers in the polyester resin. The aromatic nature of styrene monomers in the unsaturated polyols improves the hydrolytic stability and increases the chemical resistance to water, detergents and corrosion in the final, cured polyester resin product.
Acrylic monomers, such as methyl methacrylate (MMA) have been added to low or reduced styrene monomer polyester resins for marine grade gel coats and for outdoor applications. However, and unfortunately, MMA has a strong odor, is a skin and eye irritant and results in a slowing of the cure rate of a polyester resin. However, such acrylic monomers usually improve UV, water and chemical resistance. Therefore, it is not desirable to substitute MMA monomer for the styrene monomer or to add it with the styrene monomer, since MMA is also a hazardous material.
It is therefore desirable to provide new and improved, photoinitiated, cross-linkable resin compositions to replace or reduce styrene monomer in unsaturated resins, to provide unsaturated, cured resins with better physical and chemical properties and to provide an unsaturated polyester resin composition having reduced styrene monomer therein.
SUMMARY OF THE INVENTION
The invention relates to a modified acrylic urethane prepolymer concentrate for use and admixture with radiation curable, unsaturated polyester resin compositions and to the unsaturated resin compositions containing the concentrate as a diluent and a cross-linking composition and to the photocured unsaturated polyester resin compositions and their uses in and the method of preparing laminates and resin products.
The invention concerns an improved, liquid modified, acrylic urethane prepolymer concentrate adapted for addition to unsaturated resin compositions to provide improved cured resin properties and to provide unsaturated polyester resin compositions of reduced styrene monomer content. The liquid concentration comprises a modified acrylic urethane prepolymer or oligomer prepared by the reaction of a polyisocyanate, such as an aromatic isocyanate, like MDI (methylene di-p-phenylene isocyanate) or an aliphatic isocyanate, usually in a stoichiometric amount or in a slight excess, with a hydroxyl-containing acrylate monomer with or without the presence of a catalyst and a diluent monomer, like a styrene monomer, generally in an amount of less than 40% by weight of the unsaturated polyester resin composition to which the concentrate is added, and an inhibitor, such as a quinone compound, such as benzoquinone, to retard any prereaction of the prepolymer and the styrene monomer in the concentrate.
The invention is also concerned with unsaturated resin compositions subject to curing in the presence of a catalyst, typically a peroxide alone or with a metal promoter, like a metal carboxylate, such as a cobalt or copper salt, alone or in combination with various accelerators, which are amine or amide accelerators. The catalytic amount of the peroxide compound added just prior to use with the resin composition contains a promoting amount of a metal promoter salt at room temperatures in order to provide sufficient exothermic heat to cure the unsaturated polyester resin composition containing the concentrate. An unsaturated polyester resin composition is usually employed either alone or typically in conjunction with filler material, such as particles or fiber materials, like clay, quartz, sand, limestone, mica, pigments or fibers, like glass fibers, and in some cases flame retardants like aluminum trihydrate, viscosity control agents and modifiers like formed silica and flow control agents, or combinations in amounts of about 0% to 30% by weight of the resin in order to prepare cured laminates of the unsaturated polyester resin, such as a spray laminate, containing glass fibers admixed with the polyester resin.
It has been found further that the resin composition of the invention may be cured either alone by photoinitiation or in combination with a peroxide promoter where a dual curing reaction is desired. The employment of radiation compounds by the use of one or more photoinitiators added to the prepolymer used with an unsaturated resin or to the prepolymer (oligomer) concentrate-unsaturated resin composition provides many advantages in the shelf life, storage, handling and processing of the composition and in the resultant radiation cured resin and resin products produced thereby.
The photoinitiators employed may vary, depending on the intensity and type of radiation to be used, and typically are selected to promote or initiate the curing-polymerization reaction of the composition, such as by the generation of free radicals. The radiant energy employed may include high energy radiation beams, but more particularly include visible light (sunlight) or UV light. The selection of the photoinitiator is usually based on the optimum absorption surges, e.g, 250 to 450 nm or to which the curable composition either as centering or molded product is to be exposed. The photoinitiator should be compatible with and admix with the prepolymer-oligomer concentrate and the resin composition.
The photoinitiators are used in a sufficient amount to initiate and promote polymerization, which amount may vary depending on the number and type of photoinitiators and whether the composition also contains chemical curing agents and promotion and the material used in the composition, the thickness of the composition and the radiant energy to be used.
For example, the photoinitiator may be used in amounts of from about 0.01 to 5.0 percent by weight of the unstructured resin composition, such as 1.5 to 3.0 percent by weight.
The photoinitiators may be used alone or in various combinations and generally are organic compounds like, but not limited to be
Hehr International Inc.
Meyer-Leon Esq. Leslie
Richard P. Crowley, Counselor at Law, PC
Wu David W.
Zalukaeva Tanya
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