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
1992-10-30
2002-12-03
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S007000, C525S064000, C528S295500, C524S504000, C524S513000
Reexamination Certificate
active
06489398
ABSTRACT:
FIELD OF INVENTION
This invention relates to water-dilutable paints. More particularly, the invention relates to water-dilutable brushing paints based on water-soluble alkyd resins rendered water-soluble through neutralization of carboxy groups contained thereon derived from methacrylic acid.
BACKGROUND OF INVENTION
U.S. Pat. No. 4,333,865 discloses a method for preparing aqueous alkyd resin emulsions whereby the carboxy groups necessary for the stabilization of the emulsion are introduced through graft polymerization of methacrylic acid and other vinyl and acrylic monomers to a part of the unsaturated oil fatty acids used in the alkyd resin formation. All of the disclosed products contain polyethylene glycols or intermediates containing polyethylene glycols as an essential constituent. The polyethylene glycol is not introduced through an ester linkage which may be saponifiable in an aqueous medium, but rather is introduced through intermediate products. The products are used as such or in combination with urethane-modified alkyd resins. With these products air-drying, water-dilutable paints can be produced which excel in applicational properties and have outstanding storage stability. The products of the aforementioned patent containing polyethylene glycol have as another essential characteristic a maximum acid value of 35, and preferably an acid value below 25 mg KOH/g. Higher acid values invariably lead to paint films with insufficient water resistance. Although neutralization of the acid groups can be accomplished with alkali hydroxides or ammonia, paints with good gloss are obtained only when neutralization is with the use of organic amines.
According to AT-PS 375,667, emulsifier resins obtained through graft copolymerization of (meth)acrylic acid and other monomers based on polyethylene glycol-modified fatty acid polyolesters are used to prepare aqueous emulsions in combination with urethane-modified alkyd resins. Emulsions of this type are particularly suited for use in paints for wood; however, on aging, the paints yellow.
DE-OS 24 16 658 discloses that the reaction of acrylic acid or methacrylic acid with polyunsaturated fatty acids at from 250° C. to 300° C. provides adducts which can be processed to water-dilutable alkyd resins through esterification, preferably with polyglycols. The products have a relatively poor drying speed, since a major part of the fatty acids is lost for film formation through adduct formation at the time of dimerization which takes place at the necessarily high reaction temperature. Furthermore, pigment wetting is substantially reduced through the adduct formation without use of polyglycols in the subsequent alkyd resin formation.
Alkyd resins, free of polyethylene glycol, having an acid value of from 35 to 70 mg KOH/g, substantially based on methacrylic acid units which are used as “emulsifier resins” in the emulsion polymerization of vinyl and/or (meth)acrylic copolymers are described in commonly assigned European Application No. 87116502.3 filed Nov. 11, 1987, laid open May 18, 1988 under EU-OS 0267562. The methacrylic acid units are introduced into the alkyd resin as graft polymers. Emulsions are obtained according to the invention permitting the formulation of excellent air-drying, water-based paints. However, one disadvantage of such emulsions is with respect to aqueous brushing paints. Thus, the so-called wet-edge time which is the time within which the next part of a surface can be brushed without leading to leveling defects, or sticking of the brush when brushing the bordering areas, is very short. Although this time lag can be up to sixty minutes for a good brushing paint based on solvents, for dispersion paints it is often only two to three minutes. With the best alkyd copolymer dispersions, wet-edge time is at best about ten minutes. Accordingly, brushing of larger areas, such as doors, etc., can be accomplished only with difficulty by less experienced painters.
GENERAL DESCRIPTION OF INVENTION
Surprisingly it has now been found that air-drying brushing paints can be formulated having good wet-edge time based on alkyd resins, water-soluble upon partial or total neutralization of the carboxy groups, which are substantially graft copolymers of unsaturated fatty acids with blends of methacrylic acid and acryl-methacryl-vinyl monomers which carry no functional groups other than a double bond, and which preferably form benzene-dilutable homopolymers.
The present invention, therefore, is concerned with water-dilutable brushing paints based on alkyd resin binders, water-soluble upon partial or total neutralization, containing the normal pigments, extenders, and auxiliary solvents. The binder of the invention is an alkyd resin with a content of unsaturated fatty acids of from about 30% to 70%, preferably 40% to 60%. The free carboxy groups of the resin, corresponding to an acid value of from about 25 to 70 mg KOH/g, are derived up to at least 80% from methacrylic acid units. The methacrylic acid is graft polymerized prior to alkyd resin formation, together with 30% to 55% by weight, calculated on the resulting graft copolymer, of other vinyl and/or (meth)acrylic monomers carrying no reactive functional groups other than the —C═C— bond, to a part of the unsaturated fatty acids content of the alkyd resin. The conditions of the polymerization are controlled in order that the comonomers used together with methacrylic acid are such that up to at least 80% of the monomers when separately polymerized form benzene-soluble homopolymers.
The brushing paints of the present invention have a wet-edge time of twenty to forty minutes and are similar to alkyd resin paints based on solvents with regard to brushability, i.e., ease of brushing, leveling, radiance, and build. Also, the paints of this invention are at least equal to known alkyd resin emulsions with regard to storage stability and drying characteristics, two properties essential for brushing paints. Surprisingly, the products show good pigment wetting and gloss without the polyethylene glycols normally used in the production of alkyd resin emulsions. However, the use of polyethylene glycols is not precluded by this invention. In special cases they may help in paint formulation, for example when using some special pigments.
Another advantage of the alkyd resins of this invention is that the products can be neutralized with ammonia instead of organic amines to provide good wetting and radiance characteristics. The organic amines are not favored from the ecological standpoint.
The alkyd resins used for the brushing paints of the present invention are water-soluble through at least partial salt formation at their carboxylic groups with ammonia, alkali hydroxides, or organic amines. It is noted that the water-solubility does not necessarily lead to clear solutions. As known to one skilled in the art, the resins in these solutions have large resin micelles, so that the solutions may be opaque or even turbid.
As an essential feature, the alkyd resins of this invention have an acid value of 25 to 70 mg KOH/g, at least 80% of the acid groups being derived from methacrylic acid units, which, together with 30% to 55% by weight, calculated on the weight of the resulting graft copolymer, of other vinyl and/or (meth)acrylic monomers which carry no functional groups other than the —C═C— double bond, are graft polymerized in a separate reaction step to a part of the unsaturated fatty acids used in the alkyd preparation. The selection of the ethylenically unsaturated monomers, in addition to methacrylic acid, is made under the condition that at least 80% of the monomers will form benzene-soluble homopolymers when separately polymerized. The alkyd resins are prepared using conventional processes.
The content of drying and/or semi-drying fatty acids of the alkyd resins of this invention is from about 30% to 70% by weight, preferably between 40% and 60% by weight of the alkyd resin. Of these fatty acids, from about 10% to 40% by weight, calculated on the resin weight, is introduced in the form of fatt
Awad Rami-Raimund
Weger Walter
Zückert Bertram
Foley & Lardner
Short Patricia A.
Solutia Austria GmbH
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