Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-05-14
2004-01-13
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S106000, C528S405000, C528S408000
Reexamination Certificate
active
06677426
ABSTRACT:
1. TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to a solvent-free epoxy resin composition which has a low viscosity and excellent low-temperature curability; gives a cured product having excellent physical properties; and is suitable for such applications as coatings, civil engineering and adhesives, and to a production process for the same and a solvent-free coating comprising the same.
2. BACKGROUND OF THE INVENTION
An epoxy resin has been widely used in such fields as coatings, civil engineering and adhesives because it has superior corrosion resistance, adhesion, chemical resistance and flexibility. Since the epoxy resin is used on the site in many cases in these fields, an ambient-temperature curable material which includes a bisphenol type epoxy resin and an organic polyamine-based curing agent as essential ingredients is generally used in most cases to meet strict requirements including costs. In recent years, use of a low-boiling-point solvent in synthetic resin materials is restricted in consideration of its harmfulness to the human body and the global environment, thereby promoting development and use of a solvent-free material. However, a solvent-free ambient-temperature curable material involves such problems to be solved as poor workability due to a high viscosity of resin, low curing speed at a low temperature in winter and unsatisfactory physical properties of a cured product.
Japanese Patent Application Laid-open No. Sho 48-25099 proposes an epoxy resin modified by an acetoacetic acid ester group. This is aimed to increase the curing speed by introducing an acetoacetic acid ester group to increase the number of functional groups. However, an epoxy resin having a small molecular weight must be used to obtain a modified resin having a low viscosity required to achieve high workability at a low temperature, such a resin inevitably has a small number of hydroxyl groups in the molecule, and therefore a large number of acetoacetic acid ester groups which are functional groups cannot be introduced. As a result, the resin is unsatisfactory in terms of curability at a low temperature as well as viscosity.
U.S. Pat. No. 5,021,537 proposes a resin prepared by mixing a compound obtained by acetoacetylating the hydroxyl groups of a polyhydric alcohol as a reactive diluent with an epoxy resin to reduce viscosity and improve low-temperature curability. However, compared with the reactivity of epoxy groups contained in the epoxy resin, the reactivity of an acetoacetylated diluent component is fast, whereby the cured product becomes non-uniform in structure and therefore inferior in mechanical properties.
It is an object of the present invention to provide a solvent-free epoxy resin composition which has solved the above problems of an epoxy resin; has a low viscosity and excellent low-temperature curability; gives a cured product having excellent physical properties; and is suitable for use in coatings, civil engineering and adhesives as well as a production process for the same.
3. SUMMARY OF THE INVENTION
In view of the above situation, the present inventor has conducted intensive studies and has found that a resin composition having satisfactory curability at a viscosity suitable for use at a low temperature range and excellent mechanical properties, and solving problems hitherto, is obtained by using together a modified epoxy resin prepared by reacting an epoxy resin with an alkyl-substituted acetoacetate to substitute hydroxyl groups contained in the epoxy resin with acetoacetyl groups, and a compound prepared by reacting a polyhydric alcohol with an alkyl-substituted acetoacetate to substitute hydroxyl groups contained in the polyhydric alcohol with acetoacetyl groups. The present inventor has further found that the above object can be attained by a modified epoxy resin composition obtained by reacting an alkyl-substituted acetoacetate with a mixture of an epoxy resin and an alcohol having at least one hydroxyl group in one molecule to acetoacetylate hydroxyl groups contained in the epoxy resin and in the alcohol, and moreover that the resin composition can be produced efficiently in a short period of time. The present invention has been accomplished based on these findings.
Thus, the present invention relates to a modified epoxy resin composition comprising a reaction product of an epoxy resin and an alkyl-substituted acetoacetate and a reaction product of an alcohol having at least one hydroxyl group in one molecule and an alkyl-substituted acetoacetate. Preferably the modified epoxy resin composition has a number average molecular weight of 300 to 1,000, and the melting point of the alcohol is 0° C. or lower, and the viscosity of the alcohol is {fraction (1/10)} or less of the viscosity of the epoxy resin at 25° C. The alkyl-substituted acetoacetate is preferably tert-butyl acetoacetate.
There is also provided a process for producing a modified epoxy resin composition, by adding an alkyl-substituted acetoacetate to a mixture of an epoxy resin and an alcohol having at least one hydroxyl group in one molecule to carry out a reaction so as to acetoacetylate hydroxyl groups contained in the epoxy resin and hydroxyl groups contained in the alcohol.
4. DETAILED DESCRIPTION OF THE INVENTION
Examples of the epoxy resin used in the present invention include: bisphenol type epoxy resins such as bisphenol A, halogenated bisphenol A, bisphenol F and bisphenol S; biphenyl type epoxy resin; ester type epoxy resins such as dibasic acid; alicyclic epoxy resins; and terpene diphenol type epoxy resins. Alkyl phenol novolak epoxy resins such as phenol novolak epoxy resin and cresol novolak epoxy resin, and epoxy resin of bisphenol A novolak may also be used. These epoxy resins may be used alone or in combination of two or more thereof. As for processes for producing the above epoxy resins, the epoxy resins are obtained by a direct or indirect process for synthesizing bisphenol A type epoxy resin and bisphenol F type epoxy resin, and the epoxy resins having hydroxyl groups are obtained by reacting an epoxy resin with an aliphatic monocarboxylic acid or by reacting an epoxy resin with a monophenol. The aliphatic monocarboxylic acid is not particularly limited but it is preferably an aliphatic, or animal or vegetable oil fatty acid having 4 to 30 carbon atoms. Illustrative examples of the aliphatic monocarboxylic acid include castor oil fatty acid, tall oil fatty acid, lauric acid, palmitic acid, stearic acid, oleic acid, versatic acid, propionic acid, butanoic acid and pentanoic acid. Tall oil fatty acid and lauric acid which are inexpensive and can be acquired stably are particularly preferred. The monophenol is not particularly limited but it is preferably an alkylphenol having 4 to 20 carbon atoms. Illustrative examples of the monophenol include nonylphenol, p-tert-butylphenol and dodecylphenol. Dialkanolamines such as dimethanolamine and diethanolamine may also be used. These aliphatic monocarboxylic acids and monophenols may be used alone or in combination of two or more thereof. The epoxy resin used in the present invention is preferably an epoxy resin having a number average molecular weight of 300 to 1,000, more preferably a liquid epoxy resin having a number average molecular weight of 300 to 500. Use of an epoxy resin having a number average molecular weight of 1,000 or more makes it difficult to obtain a solvent-free epoxy resin composition having a low viscosity.
Examples of the alcohol having at least one hydroxyl group in one molecule used in the present invention include: linear or branched alcohols such as methanol, ethanol, propanol, neopentyl alcohol, octanol and decanol, as well as ethylene oxide and propylene oxide adducts therewith; and linear or branched low-molecular polyols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, decanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol and neopentyl glycol, and ethylene oxide and propylene oxide adducts therew
Kobayashi Yoshikazu
Noro Yukio
Aylward D.
Dawson Robert
Jones Lisa Kimas
Resolution Performance Products LLC
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