Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-05-13
2001-06-26
Pianalto, Bernard (Department: 1762)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C427S393600, C427S407100, C427S419700, C427S518000, C427S558000, C427S559000, C428S413000, C428S418000, C428S423100, C428S425800, C428S446000, C428S457000, C428S698000, C428S704000
Reexamination Certificate
active
06251520
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a non-aqueous sizing for ceramic fibers. The sizing makes the fiber easier to handle, wind, and weave. This invention also relates to a method for producing a sized, coated ceramic fiber.
BACKGROUND OF THE INVENTION
Ceramic composite materials used in high temperature applications require the use of a ceramic fiber for reinforcement. Commercially available ceramic fibers are typically provided with a sizing on the fiber. Generally, any sizing is removed before coating the ceramic fiber with an interfacial coating. The resulting fiber is difficult to handle, filament wind, or weave into a 2-dimensional fabric or 3-dimensional pre-form. Additionally, an unsized fiber is prone to mechanical damage.
U.S. Pat. No. 5,093,155 issued to Miyazaki et al. on Mar. 3, 1992, discloses sizing liquid containing a sulfone compound and a solvent such as water or an organic solvent. The sizing is applied to fibers, including carbon, boron, ceramic, and metal fibers. The fibers are incorporated in a matrix resin to make a composite. The sizing enhances adhesion between the fibers and the matrix. U.S. Pat. No. 5,130,194 issued to Baker et al. on Jul. 14, 1992, discloses a coating for ceramic fibers used in composites. The fibers are generally coated with a silanol and a difunctional organic coupling agent in a water or alcohol solvent. The silanol provides hydroxyl groups on the fiber, and the coupling agent connects the hydroxyl binding sites to a resin to form a composite. However, aqueous sizing materials can damage coated fibers if the coating is moisture sensitive, resulting in deteriorated composite properties.
U.S. Pat. No. 5,173,367 issued to Liimatta et al. on Dec. 22, 1992, discloses a fiber reinforced ceramic composite. The fiber has a 2 layer size obtained by sizing the fibers with a solution of an organic solvent, a metal oxide, and a titanium compound. The fibers are then sized with an organic solvent solution of a polycarbosilane or polysilazane. The sizing protects the fibers from oxidative deterioration.
One object of the present invention is to provide a non-aqueous sizing for ceramic fibers that makes the fibers easier to handle, wind, and weave. Another object of the present invention is to provide a sizing that is easily removed by heat treatment at low temperature and leaves little or no residue when decomposed in an inert atmosphere. Another object of the present invention is to produce a sized fiber that is less prone to moisture and mechanical damage.
SUMMARY OF THE INVENTION
The present invention relates to a non-aqueous sizing composition that can be applied to small diameter ceramic fibers, such as silicon carbide and silicon oxycarbide fibers. The fibers may be coated with interfacial coatings. Some interfacial coatings are moisture-reactive. The sizing protects the fiber and interfacial coatings from moisture and mechanical damage during winding and weaving. The sizing can be removed in an inert environment at low temperature. A method for producing sized fibers is also disclosed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a non-aqueous sizing composition for materials such as fibers, preferably ceramic fibers having interfacial coatings. The sizing composition comprises a sizing compound and a curing agent.
Suitable sizing compounds for the present invention are multifunctional acrylates or multifunctional methacrylates. Multifunctional acrylates have at least two acrylate groups per molecule. Multifunctional methacrylates have at least two methacrylate groups per molecule. The sizing compound can be a monomer or a polymer. The amount of the sizing compound in the non-aqueous sizing composition is typically 1 to 98%, preferably 12 to 38% by weight of the non-aqueous sizing composition.
Suitable multifunctional acrylates and multifunctional methacrylates for the sizing compound are exemplified by those disclosed in U.S. Pat. No. 5,626,964, which is hereby incorporated by reference for the purpose of providing examples of multifunctional acrylates and multifunctional methacrylates only.
Suitable multifunctional acrylate monomers include diacrylates, triacrylates, tetraacrylates, and pentaacrylates. Suitable diacrylates include:
1,6 hexanediol diacrylate,
1,4-butanediol diacrylate,
ethylene glycol diacrylate,
diethylene glycol diacrylate,
tetraethylene glycol diacrylate,
tripropylene glycol diacrylate,
neopentyl glycol diacrylate,
poly(butanediol) diacrylate,
1,3-butylene glycol diacrylate,
triethylene glycol diacrylate,
triisopryopylene glycol diacrylate, and
polyethylene glycol diacrylate.
Examples of suitable triacrylates include trimethylolpropane triacrylate, trimethylolpropane triethoxy triacrylate, and pentaerythritol monohydroxy triacrylate. Trimethylol propane triacrylate is preferred when the sizing compound is a multifunctional acrylate monomer.
Examples of suitable tetraacrylates include pentaerythritol tetraacrylate, and di-trimethylolpropane tetraacrylate. Suitable pentaacrylates include dipentaerythritol (monohydroxy) pentacrylate.
Suitable multifunctional methacrylate monomers include dimethacrylates, trimethacrylates, tetramethacrylates, and pentamethacrylates. Examples of suitable dimethacrylates include 1,4-butanediol dimethacrylate, tetraethylene glycol dimethacrylate, and Bisphenol A dimethacrylate. Examples of suitable trimethacrylates include trimethylolpropane trimethacrylate.
The sizing compound can also be a multifunctional acrylate polymer. Multifunctional acrylate polymers are selected from the group consisting of: epoxy acrylate polymers, urethane acrylate polymers, polyester acrylate polymers, and mixtures thereof.
Suitable epoxy acrylate polymers include Bisphenol A epoxy diacrylate, available from Sartomer Company, Inc. of Exton, Pa. Bisphenol A epoxy diacrylate is sold under the designation CN104. CN104 has a viscosity of 3,500 mPa s at 65° C. and a specific gravity of 1.15.
Suitable urethane acrylate polymers include hexafunctional aromatic urethane acrylate with an acrylated polyol diluent, which is available under the designation Ebecryl-220™. Ebecryl-220™ has a molecular weight of 1,000 and a viscosity of 28,000 mPa s at 25° C. Another suitable urethane acrylate is aliphatic urethane diacrylate, which is available under the designation Ebecryl-230™. Ebecryl-230™ has a molecular weight of 5,000 and a viscosity of 40,000 mPa s at 25° C. Both of these urethane acrylates are available from UCB Radcure, Inc. of Louisville, Ky.
Suitable polyester acrylate polymers include tetrafunctional polyester acrylate, which is available under the designation Ebecryl-80™ by UCB Radcure, Inc. of Louisville, Ky. Ebecryl-80™ has a molecular weight of 1,000 and a viscosity of 3,500 mPa s at 25° C.
Urethane acrylate polymers are preferred for the sizing compound of this invention. Ebecryl-220™ is particularly preferred.
The curing agent in the non-aqueous sizing composition is selected from the group consisting of ultra-violet photoinitiators and free radical initiators. Preferably, the curing agent is an ultra-violet photoinitiator.
When the curing agent is an ultra-violet photoinitiator, the amount present is 1 to 20%, preferably 2 to 8%, by weight of the non-aqueous sizing composition. The ultra-violet photoinitiator can be any compound that will start a reaction with the sizing compound when exposed to ultra-violet radiation. The ultra-violet photoinitiator must be compatible with the other ingredients of the composition. Compatibility can be determined by mixing about 1 weight percent of the ultra-violet photoinitiator with the other ingredients of the composition at room temperature. The photoinitiator is compatible if no precipitate forms. Another requirement for the photoinitiator is that it may not cause the composition to react in the absence of ultra-violet radiation.
Suitable compounds for the ultra-violet photoinitiator include benzophenone, acetonaphthone, acetophenone, benzoin methyl ether, benzoin isobutyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxyc
Blizzard John Donald
Szweda Andrew
Wieber Gary Michael
Dow Corning Corporation
Pianalto Bernard
Severance Sharon K.
LandOfFree
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