Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-10-30
2003-11-25
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S416000, C428S480000, C428S520000, C428S522000, C525S327300
Reexamination Certificate
active
06652971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to hydroxy-functional (meth)acrylic copolymers and solvent-based, one-component and two-component coating compositions containing them. The invention finds application in automotive and industrial coatings.
2. Description of Related Art
In automotive coatings in particular, there is a need for coating compositions which produce flexible, scratch resistant and chemical and acid resistant coatings. It is already known from the prior art that scratch resistant coatings can be obtained by using hydroxy-functional (meth)acrylic copolymers whose hydroxyl groups are modified with lactones.
For example, coating compositions for automotive coatings that are based on epsilon caprolactone-modified (meth)acrylic copolymers and aminoplastic cross-linking agents are described in U. S. Pat. No. 4,546,046. The (meth)acrylic copolymers are prepared from carboxy-functional or hydroxy-functional unsaturated monomers, unsaturated monomers without further functionality, and epsilon caprolactone. The modification with epsilon caprolactone may be carried out in various ways: epsilon caprolactone may be added directly to the unsaturated monomers, or the addition is made only after polymerization of the unsaturated monomers. Similarly, pre-adducts of epsilon caprolactone and hydroxy-or carboxy-functional unsaturated monomers may be formed and then polymerized with further unsaturated-monomers;
Coating compositions of the binders thus prepared produce flexible coatings with good scratch resistance but insufficient acid resistance. Also, when the above-mentioned coating compositions are applied as clear coats, particularly to solvent-based base coats, the base coat is partially dissolved by the clear coat.
This invention provides hydroxy-functional binders based on (meth)acrylic copolymers which, when used in one-component and two-component coating compositions, produce flexible scratch resistant coatings with very good chemical and acid resistance. When applied as a clear coat to solvent-based base coats in particular, there is no or only a slight dissolution of the base coat.
SUMMARY OF THE INVENTION
The invention is directed to hydroxy-functional (meth)acrylic copolymers having an OH value from 40 to 260 mg KOH/g, a number average molecular mass (Mn) from 1500 to 20000 g/mole and a glass transition temperature Tg from −40° C. to 80° C., comprising
polymerized monomers of at least one epoxy-functional, olefinically unsaturated monomer (component A),
at least one compound having a carboxyl group and at least one hydroxyl group in the molecule that is reacted with the epoxy-functional group of the polymerized olefinically unsaturated monomers (component B),
at least one additional polymerized olefinically unsaturated monomer capable of radical polymerization (component C) which is different from component A, and
optionally, at least one lactone (component D) reacted with the polymer.
The invention also is directed to a process for the preparation of the hydroxy-functional (meth)acrylic copolymers, wherein the copolymer is formed by radical polymerization of epoxy functional, olefinically unsaturated monomers (component A) and at least on additional polymerizable olefinically unsaturated monomer (component C) and at least a part of the hydroxyl groups are introduced into the copolymer by reaction of the epoxy group of the epoxy-functional, olefinically unsaturated monomer (component A) with compounds having a carboxyl group and at least one hydroxyl group (component B). The hydroxyl groups introduced in this way are situated in the copolymer side chain and result from the hydroxyl groups originating from component B and the secondary hydroxyl groups obtained during the ring-opening reaction of the epoxy groups of component A) with the carboxyl groups of component B).
DETAILED DESCRIPTION OF THE EMBODIMENTS
The term (meth)acrylic as used here and hereinafter should be taken to mean methacrylic and/or acrylic.
Surprisingly, it was found that hydroxy-functional (meth)acrylic copolymers prepared in this way, when used in coating compositions, form coatings having, in particular, a balanced ratio between good acid resistance and good scratch resistance.
The hydroxy-functional (meth)acrylic copolymers contain at least one further olefinically unsaturated monomer capable of radical polymerization (component C) which is different from component A).
Preferred hydroxy-functional (meth)acrylic copolymers have an OH value from 80 to 220 mg KOH/g, a number average molecular mass Mn from 2000 to 15000 g/mole, especially preferred from 4000 to 12000 g/mole and a glass transition temperature Tg from −40° C. to 60° C. Component A) is contained preferably in an amount from 1 to 90 wt-%, component B) from 1 to 80 wt-% and component C) from 5 to 80 wt-% in the hydroxy-functional (meth)acrylic copolymers, the proportions by weight of components A), B) and C) totaling 100 wt-%.
Further preferred hydroxy-functional (meth)acrylic copolymers also contain at least one lactone (component D). The at least one lactone may be present preferably in an amount from 2 to 50 wt-%, particularly preferably 5 to 30 wt-%, based on the total amount of components A), B), C) and D), the proportions by weight of components A), B), C) and D) totaling 100 wt-%.
Examples of suitable epoxy-functional, olefinically unsaturated monomers (component A) capable of radical polymerization, hereinafter abbreviated to epoxy-functional monomers, include (meth)allyl glycidyl ether, 3,4-epoxy-1-vinylcyclohexane, epoxycyclohexyl(meth)acrylate, vinyl glycidyl ether, 2-methyl glycidyl(meth)acrylate and glycidyl (meth)acrylate. Glycidyl (meth)acrylate is used in preference.
The compounds having a carboxyl group and at least one hydroxyl group (component B) are, for example, hydroxymonocarboxylic acids having at least one hydroxyl group, preferably hydroxymonocarboxylic acids having 1 to 3 hydroxyl groups. The hydroxyl groups may be primary or secondary hydroxyl groups. The hydroxymonocarboxylic acids may be linear or branched, saturated or unsaturated. They may for example be hydroxymonocarboxylic acids having 2 to 20 carbon atoms in the molecule.
Examples of hydroxymonocarboxylic acids having one hydroxyl group are 2-hydroxyacetic acid, 2-hydroxypropionic acid, 3-hydroxypropionic acid, 2-hydroxy-2-methylpropionic acid, hydroxy-2,2-dimethylpropionic acid (hydroxypivalic acid), hydroxy-2,2-diethylpropionic acid, 2-, 3-, and 4-hydroxybutyric acid, 2-hydroxyvaleric acid, 2-hydroxycaproic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 12-hydroxystearic acid and ricinoleic acid. Examples of hydroxycarboxylic acids having two hydroxyl groups are dimethylol propionic acid, dimethylol butyric acid and glyceric acid. Tris-hydroxymethylacetic acid is an example of an hydroxycarboxylic acid having 3 hydroxyl groups.
Further suitable compounds having a carboxyl group and at least one hydroxyl group are reaction products of hydroxymonocarboxylic acids and lactones. The lactones undergo an addition reaction with the hydroxyl group. Suitable hydroxycarboxylic acids are those already mentioned above. Examples of suitable lactones are those containing 3 to 15 carbon atoms in the ring and where the rings may also have various substituents. Preferred lactones are gamma butyrolactone, delta valerolactone, epsilon caprolactone, beta hydroxy-beta-methyl-delta valerolactone, lambda laurinlactone or mixtures thereof. Epsilon caprolactone is particularly preferred.
Further compounds having a carboxyl group and at least one hydroxyl group are compounds which contain ester groups in addition to the carboxyl group and the at least one hydroxyl group. Such compounds C) may be obtained, for example, by reaction of the above-mentioned hydroxymonocarboxylic acids with acid anhydrides and further reaction of the compounds thus obtained with epoxy-functional compounds, e.g., olefinically unsaturated epoxy-functional compounds. Examples of suitable olefinically unsaturated epoxy-functional compounds are t
Delmotte Ann
Huybrechts Josef
Kerber Hermann
Ley Olaf
Paulussen Harold
E. I. du Pont de Nemours and Company
Fricke Hilmar L.
Tarazano D. Lawrence
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