Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1995-02-10
2001-12-11
Gulakowski, Randy (Department: 1742)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S529000, C525S530000, C525S533000, C525S922000, C523S442000
Reexamination Certificate
active
06329475
ABSTRACT:
The invention relates to a curable epoxy vinylester or polyester composition which cures with a low peak exotherm within commercially acceptable processing times. The invention further relates to a method of curing an epoxy vinylester resin or polyester resin composition under conditions such that the resin cures with a low peak exotherm in a few hours or less.
Epoxy vinylester resins and polyester resins are well-known in the art. Such resins are useful as the continuous matrix in composite applications, and in the fabrication of molded parts. The resins suffer from the problem that during cure an exothermic reaction occurs leading to a high peak exotherm. When used to make thick or large parts or laminates the high peak exotherm can cause serious problems in that thermal stress induced in the structure causes it to crack.
Japanese Patent Application 5 2051,489 discloses curing of unsaturated polyester resins with an organic peroxide in the presence of an organo metallic compound, alicyclic beta diketones and an amine. It is disclosed that the composition improves the curing speed and that the products are hardly discolored with good workability.
U.S. Pat. No. 4,309,511 discloses curing an unsaturated polyester resin composition which contains an unsaturated comonomer. The claimed improvement is the use of a cure promoter comprising a cobalt salt, a copper salt and a heterocyclic amine. It is disclosed that the cure promoter provides a very fast accelerator system when used in conjunction with peroxide to give cure times of 5 to 15 minutes and that in the uncatalyzed state the resin has a shelf life of 80 to 150 days. It is further disclosed that little or no color is imparted to the resin.
What is needed is a curable epoxy vinylester resin or polyester resin composition that cures within reasonable times at low peak exotherms. What is further needed is a method of curing epoxy vinylester compositions and polyester compositions wherein the peak exotherm of the cure cycle is low and the time period for cure is short enough to facilitate reasonable productivity but not so short as to render the composition unhandleable, for example between 0.5 to 2.0 hours.
In a first aspect, the invention provides a curable resin composition comprising
A. an epoxy vinylester resin or a polyester resin;
B. a polymerizable monomer;
C. a chelating agent;
D. a copper salt or complex of copper with an alcohol, aldehyde or ketone; and
E. an inhibitor which is an alkylated phenolic compound or polyhydroxy aromatic compound.
In another aspect the invention is a two part curable composition comprising
I. A resin composition comprising
A. an epoxy vinylester resin or a polyester resin;
B. a polymerizable monomer;
C. a chelating agent comprising a compound containing a polar function or an aromatic ring;
D. a copper salt or a complex of copper with an alcohol, ketone or aldehyde; and
E. an inhibitor comprising an alkylated phenolic compound or polyhydroxy aromatic hydrocarbon; and
II. A catalyst system which comprises
E. optionally, an additional amount of the inhibitor;
F. optionally an aliphatic amine, a heterocyclic amine or an aromatic amine;
G. a peroxide or persulphate initiator; and
H. a transition metal accelerator.
In another aspect the invention is a method of curing the resin composition which comprises contacting the resin composition (I) with a catalytic amount of catalyst system (II); optionally contacting the mixture with a reinforcing structure, and allowing the mixture to cure under condition such that the peak exotherm is from 40° C. to 120° C. and the cure time is from 30 to 120 minutes.
In another aspect the invention is the use of a copper salt or copper complex with an alcohol, aldehyde or ketone; combined with a chelating agent and an inhibitor comprising an alkylated phenolic compound or polyhydroxy aromatic hydrocarbon to cure an epoxy vinylester resin or a polyester resin composition.
The curable composition and method for curing such curable composition claimed herein allows for the preparation of thick structures and large parts using polyester or epoxy vinylester resins without damage due to overheating of the reaction mass. The composition and method of invention allows controllable curing of large or thick parts such that good quality products are made.
The epoxy vinylester resins that can be employed in the composition of the present invention may be prepared (1) by reacting a polyepoxide with an ethylenically unsaturated carboxylic acid to produce a reaction product which contains, in part, the functional group
produced by the interaction of an epoxide group with a carboxylic acid group, or (2) by further condensation of the secondary hydroxyl groups contained in the above reaction product with a dicarboxylic acid anhydride to produce pendant half ester groups. The resulting epoxy vinylester resins can then be admixed with a polymerizable monomer containing a >C═CH
2
group. In the first stage of the resin preparation, the polyepoxide is preferably added in an amount sufficient to provide from 0.8 to 1.2 equivalents of epoxide per equivalent of carboxylic acid. If desired, the further condensation of the secondary hydroxyl groups is completed by the addition of a dicarboxylic acid anhydride to form pendant half ester groups with the secondary alcohol group generated from the epoxide-carboxylic acid reaction. The proportion of this added dicarboxylic acid anhydride can be varied to convert any or all of the secondary hydroxyl groups to pendant half ester groups.
Ethylenically unsaturated carboxylic acids that are preferable for reaction with the polyepoxide include the &agr;,&bgr;-unsaturated monocarboxylic acids and the hydroxyalkyl acrylate or methacrylate half esters of dicarboxylic acids. The &agr;,&bgr;-unsaturated monocarboxylic acids include such acids as acrylic acid, methacrylic acid, crotonic acid and cinnamic acid. The hydroxyalkyl group of the acrylate or methacrylate half esters preferably contains from two to six carbon atoms and may be, for example, hydroxyethyl, beta-hydroxy-propyl or beta-hydroxybutyl. The hydroxyalkyl group may also include an ether oxygen. The dicarboxylic acids can be either saturated or unsaturated in nature. Saturated acids include phthalic acid, chlorendic acid, tetrabromophthalic acid, adipic acid, succinic acid and glutaric acid. Unsaturated dicarboxylic acids include maleic acid, fumaric acid, citraconic acids, itaconic acid, halogenated maleic or fumaric acids and mesaconic acid. Mixtures of saturated and ethylenically unsaturated dicarboxylic acids can be employed.
The half esters preferably employed are prepared by reacting substantially equal molar proportions of a hydroxyalkyl acrylate or methacrylate with a dicarboxylic acid anhydride. Other unsaturated anhydrides that can be employed include maleic anhydride, citraconic anhydride and itaconic anhydride; preferred saturated anhydrides that can be employed include phthalic anhydride, tetrabromophthalic anhydride and chlorendic anhydride. Advantageously, a polymerization inhibitor, such as the methyl ether of hydroquinone or hydroquinone, may be added inasmuch as elevated temperatures are useful in preparing the half esters.
Any of the known polyepoxides can be employed in the preparation of the epoxy vinylester resins. Preferred polyepoxides are glycidyl polyethers of polyhydric alcohols, polyhydric phenols, epoxy novoiacs, elastomer modified epoxides, halogenated epoxides, epoxidized fatty acids or drying oil acids, epoxidized diolefins, epoxidized di-unsaturated acid esters, epoxidized unsaturated polyesters and mixtures thereof, as long as they contain more than one epoxide group per molecule. The polyepoxides may be monomeric or polymeric in nature. Preferred polyepoxides include glycidyl polyethers of polyhydric alcohols or polyhydric phenols, having weights per epoxide group (EEW) of 150 to 2,000. These polyepoxides are usually made by reacting at least two moles of an epihalohydrin or glycerol dihalohydrin with one mole of the polyhydric phenol and a sufficie
Gulakowski Randy
The Dow Chemical Company
LandOfFree
Curable epoxy vinylester composition having a low peak... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Curable epoxy vinylester composition having a low peak..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Curable epoxy vinylester composition having a low peak... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579705