Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-02-23
2002-01-29
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S524000, C428S531000, C525S476000, C525S481000
Reexamination Certificate
active
06342303
ABSTRACT:
FIELD OF THE INVENTION
The preparation of epoxy-functional polysiloxane modified phenolic resole resins and use thereof in composites.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,864,000 to Lightbody is directed to hybrid phenolic/polysiloxane resins derived from (A) reacting a phenolic compound with (a) a siloxane polymer or (b) and aldehyde and (B) reacting the reaction product of(A)(a) with an aldehyde, or (A)(b) with a siloxane polymer to form the hybrid phenolic/polysiloxane resin. The siloxane polymer is defined as compounds having —Si—O—Si— groups in their structure. Suitable siloxane polymers were described as alkoxy and/or silanol functional siloxane polymers having a molecular weight of 1000 to 6000.
U.S. Pat. No. 5,319,005 to Hagiwara et al. relates to epoxy resin molding materials used for sealing electronic components such as transistors and integrated circuits. The composition comprises an epoxy resin having at least two epoxy groups per molecule and a phenolic compound having at least two phenolic hydroxyl groups per molecule such as phenol-formaldehyde resin condensates. To the epoxy resin containing phenolic compound are added a vinyl group-containing organopolysiloxane and a ≡SiH group-containing organopolysiloxane as well as inorganic filler. The two types of organopolysiloxanes are permitted to react with one another to effect curing of the epoxy resin. The polysiloxanes form a particulate which is dispersed throughout the resin.
U.S. Pat. No. 4,853,434 to Block teaches a modified thermosetting resin comprising a reaction resin or reaction resin mixture and one or more three-dimensional crosslinked polyorganosiloxane rubbers. Suitable reaction resins include epoxy resins and condensation products of aldehydes, including formaldehyde, with aliphatic and aromatic compounds containing amine groups including urea or melamine as well as aromatic compounds such as phenol, resorcinol, xylene and the like. The compositions are prepared by dispersing polyorganosiloxane rubber particles in the thermosetting resin or mixture of thermosetting resins in the presence of a crosslinking catalyst at temperatures of from 18 to 120° C.
U.S. Pat. No. 4,022,753 to Lohse et al. discloses the reaction products of a polysiloxane and polyphenols such as resorcinol, bisphenol A etc. (novolac resins) The resulting product is utilized as a curing agent or modifying agent for epoxy resins.
U.S. Pat. No. 5,530,063 to Nagai et al. shows organopolysiloxane compositions which are room temperature-curable and which comprise an organopolysiloxane, a polymer of a monomer having an ethylenically unsaturated double bond and an epoxy compound. Suitable curing agents and catalysts are also present in the formulation.
It is desirable to improve the toughness of phenolic resins without decreasing fire-resistance properties of composites.
SUMMARY OF THE INVENTION
Phenolic resole resins are modified with epoxy-functional polysiloxane by one of these methods: (1) reacting phenol with the epoxy-functional polysiloxane as the first step of preparation of the phenolic resole; (2) adding the epoxy-functional polysiloxane to the phenolic resole after the phenolic resole has been prepared (i.e. a blend procedure) or (3) reacting the epoxy-functional polysiloxane with resorcinol, bisphenol-A, or bisphenol-F, and then blending this phenolic functionalized silicone with a resole or reacting it with formaldehyde to make a resole.
DETAILED DESCRIPTION OF THE INVENTION
Phenolic resole resin compositions are modified with epoxy-functional polysiloxanes. The compositions may be produced by several methods including (1) reacting epoxy-functional polysiloxane with phenol and then reacting the polysiloxane grafted phenol with formaldehyde to form a phenolic resole resin; (2) blending a pre-existing phenolic resin with the epoxy-functional polysiloxane and permitting the grafting reaction to proceed coincident with the curing/hardening of the phenolic resin and (3) reacting an epoxy-functional polysiloxane with a polyhydroxy phenolic monomer, such as resorcinol or a bisphenol, and either combining the reacted material with a pre-existing phenolic resin for curing/hardening or further treating the reacted material with formaldehyde or phenol and formaldehyde to make a silicon-modified phenolic resin.
The resulting compositions may be used to impregnate a variety of substrates, such as, but not limited to paper, glass roving or mat, carbon fiber, aramid fibers, kevlar, and nomex honeycomb.
Different types of epoxy-functional polysiloxanes may be used. The preferred epoxy-functional polysiloxane (epoxy silicone) is depicted by the right-hand formula below. The left-hand formula provides a shorthand definition. However, these formulas are illustrative only. The epoxy-functional polysiloxane may be any suitable epoxy-functional polysiloxane that provides the desired epoxy-functional polysiloxane-modified phenolic resin.
The terms epoxy-functional polysiloxane and epoxy-functional silicone may be used interchangeably. In the definition of epoxy-functional polysiloxane, x is 1 to 100 and y is 0 to 10,000, and the ratio of x:y is typically from 1:0.5 to 1:100, preferably 1:1 to 1:10, and most preferably 1:1 to 1:5. One epoxy-functional polysiloxane available commercially is silicone Y-12940 from OSI Witco.
As stated above, any suitable epoxy-functional polysiloxane may be used. The polysiloxane may include branching points, and the epoxy-functional repeat units need not be adjacent to one another. Thus, the copolymer may be a random, alternating, or block copolymer. Other epoxy-functional polysiloxanes include, but are not limited to, the following epoxy-functional polysiloxane, where x is 0 to 1000, preferably 0 to 100, and most preferably 5 to 30.
This polysiloxane is available commercially as OSI Witco Silicone Y-14362.
The epoxy-functional polysiloxane-modified phenolic resin may be made by several different procedures identified below as procedures #1, #2, and #3.
Procedure #1
First, phenol is reacted with the epoxy-functional polysiloxane to open the epoxy ring and form a C—O—C ether linkage between the phenol and the silicone molecule. Then, formaldehyde is added to form a phenolic resole resin with excess phenol and with epoxy-functional polysilxane-modified phenol.
More specifically, an epoxy-functional polysiloxane is mixed with excess phenol and a basic catalyst, such as sodium hydroxide, and heated to between about 120° C. and about 180° C., preferably about 140° C., for between about 30 minutes and about 90 minutes. Subsequently, the reaction mixture is cooled to between about 45° C. and about 75° C., preferably about 55° C., and formaldehyde is added. The reaction mixture is then heated to between about 65° C. and about 90° C., preferably about 75° C., and held at that temperature until a desired free formaldehyde is achieved. Suitable free formaldehyde levels are generally between about 0.5 wt % and about 4 wt %.
Generally, the weight range of epoxy-functional polysiloxane to phenol is from about 100:0.1 to about 0.1:100, and the preferred range is about 5:100 to about 15:100. However, both ranges will be affected by the epoxy equivalent weight of the epoxy-functional polysiloxane.
The weight range of catalyst to phenol in the first step of the process is about 0.01 to about 10 parts of catalyst per 100 parts of phenol, preferably about 0.1 to about 2.5 parts of catalyst per 100 parts of phenol.
The mole ratio of formaldehyde to phenol is about 0.8:1 to about 3:1, preferably about 1.2:1 to about 1.9:1. A suitable catalyst, such as sodium hydroxide, may be added during the addition of the formaldehyde to promote the reaction between the phenol and formaldehyde.
The reaction scheme is illustrated below.
1. Reaction of phenol with epoxy silicone to open the epoxy ring and form a C—O—C ether linkage between phenol and the silicone.
2. Addition of formaldehyde to form a phenolic resin.
Procedure #2
An epoxy-functional polysiloxane is blended with a phenolic resole. The blend may be used
Dopico Pablo G.
Nagy Ellen V.
Qureshi Shahid P.
Banner & Witcoff Ltd
Georgia-Pacific Resins Inc.
Moore Margaret G.
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