Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-06-22
2001-04-24
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S300000, C528S301000, C528S302000, C528S306000, C528S308000, C528S308600
Reexamination Certificate
active
06222005
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to a process for preg polyester resins. According to the process a carboxylic acid or corresponding anydride containing ethylenic unsaturation is first reacted with a saturated, monobydric alcohol to form the half ester of the acid or anhydride. The half ester is then reacted with a polyol to form the polyester. It has also been found that an oil containing unsaturation such as soybean oil can be added in the reaction step of the half ester and the polyol. The addition of oils such as soybean oil permits the reduced use of petroleum derived components.
In general unsaturated polyesters are prepared from dicarboxylic functional monomers, or mixture of di- or greater carboxyl functional monomers where at least one of which contains ethylenic unsaturation. These polyesters are obtained by the condensation of the carboxylic acid monomers with polyhydric alcohols. Commercially, the polyester is dissolved in a monomer such as styrene to obtain a solution that may then be crosslinked.
U.S. Pat. No. 2,478,015 discloses a process for the preparation of unsaturated polyesters by reacting the moynoester of a beta-unsaturated monohydric alcohol and polyearboxylic acid with a polyhydric alcohol. Examples of the unsaturated alcohols include allyl alcohol, methallyl alcohol, crotyl alcohol, etc. Beta-unsaturated alcohols such as allyl alcohol are toxic and esters prepared using such alcohols have a tendency to gel. U.S. Pat. No. 3,547,898 discloses a process for the production of resins containing maleic half esters. In this process maleic acid or anhydride is reacted with a tnonoalkyl or alkaryl ethoxylate having from 4 to 15 carbon atoms in the alkyl or aralkyl group, An alcohol such as methanol may also be added to is reaction mixture. The reaction product is then dissolved in a monomer with a free radical initiator present. U.S. Pat. No. 3,979,443 discloses the preparation of monohydric alcohol esters of maleic acid. U.S. Pat. No. 5,118,783 discloses a process for preparing low molecular weight unsaturated polyesters by adding a monofunctional alcohol to the condensation reaction of dicarboxylic acids and polyhydric alcohol. Japanese Patent No. 2,863,896 discloses a process for the preparation of an ester derivative useful as a cross linking improver for polymers. The abstract of the '896 patent discloses reacting maleic anhydride with isopropanol, isomeriziag the reaction product to give monoisopropyl fiumarate and reacting that fuirnarate with a bisphenol A derivative at a temperature of 120°.
Styrene, a solvent used to prepare solutions of unsaturated polyesters is considered a hazardous pollutant. Much work has been done in an effort to prepare low volatile organic compound (VOC) unsaturated polyester resin systems. One area of focus has been the use of waxes as a means of reducing emissions. During cure waxes which are initially dissolved or dispersed in a resin, form a thin film on the surface of the fabricated article. The film acts as a physical barrier preventing styrene from evaporating from the surfce of the cring part. This film reduces styrene emissions. Unfortunately the waxy film substantially diminishes interlaminar adhesion thus reducing the strength of molded articles made using a multilarninate construction. An alternative to the use of waxes is the use of low molecular weight unsaturated polyester resins. The lower molecular weight permits the use of less styrene because of increased solubility of the resin in the styrene. Typically the molecular weight of unsaturated polyester resins is manipulated by altering the ratios of components. The highest molecular weight is achieved when a 1:1 ratio of acid to polyol is used. Increasing the ratio of one component in relation to the other lowers the molecular weight However, these synthesis techniques significantly change the performance characteristics of the resulting products. For example, using more polyol than acid can significantly reduce the reactivity and/or thermal resistance of a product. Using more acid than polyol will increase the reactivity but the acid value (AV) of the product also increases. High AV resins are not very soluble in styrene and tend to precipitate in styrene. Articles molded from these resins are susceptible to attack by water. Simply changing molecular weight without modifying the nature of the end groups diminishes the suitability of the resins for many applications.
Unlike standard methods for the preparation of unsaturated polyester resins the invention provides a method of preparation yielding resins having both a low viscosity and acid value. Resins prepared according to the invention are more soluble in styrene while still retaining good performance characteristics. Because the resins are more soluble less styrene is necessary to prepare a styrene resin solution. Reducing the styrene content allows manufacturers to continue to use conventional open mold techniques while reducing styrene emissions. When unsaturated oils are used less petroleum based materials are required.
BRIEF SUMMARY OF THE INVENTION
The invention relates to a process for preparing unsaturated polyester resins. According to the process at least one carboxylic acid or its corresponding anhydride containing ethylenic unsaturation is first reacted with at least one low molecular weight, saturated monohydric alcohol to fonn the half ester. The half ester is then reacted with at least one polyhydric alcohol in a condensation reaction. The oil containing unsaturation is added to the process at this point The process of the present invention yields a final product having a low acid value. Resins prepare according to the invention have acid values below 50 mg KOH/g and preferably below 30 mg KOH/g. When an oil containing unsaturation such as soybean is present, the resins will have acid values below 50 mg KOH/g and preferably below 50 mg KOH/g. The resins prepared according to the invention having low acid values are more soluble in styrene than comparable resins prepared using a standard ester resin synthesis process where a carboxylic acid and polyol are reacted without first reacting the acid with a saturated monohydric alcohol. Polyester resins prepared according to the invention have performance characteristics as good or better than polyester resins prepared by traditional methods.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Not Applicable
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for preparing polyester resins. According to the process a carboxylic acid having at least two carboxyl functional groups or its corresponding anhydride containing ethylenic unsaturation is first reacted with a saturated, monohydric alcohol having a boiling point of less than about 150° C. to form the half ester of the carboxylic acid or corresponding anhydride. The half ester is then reacted with polyol in a condensation reaction. In addition to the potyol, the oil containing unsaturation, such as soybean oil, can be added at this point. The polyol can be added all at once or incrementally over a period of time. Optionally catalysts can be added to promote the condensation reaction. After the polyol addition has begun the polyol/half ester mixture is allowed to react with heating. Distillate composed of water and the saturated monohydric alcohol used to prepare the half ester is removed from the reaction. Heating is continued until the desired viscosity is reached. If polyol is added incrementally, the addition should be completed before the target viscosity is attained in order to minimize the amount of imreacted polyol in the final product. In each case the carboxylic acid or its corresponding anhydride, the saturated monohydxic alcohol and the polyol can be mixture. For example, the saturated monohydric alcohol can be a mixture of ethanol and methanoL
Examples of carboxylic acids and corresponding anhydrides useful in the invention include maleic acid fimiaric
Loza Roman
McDaniel Patricia
Acquah Samuel A.
Ashland Inc.
Connaughton Martin
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