Alkyl resin emulsions and utilization of the same

Details Alkyl resin emulsions and utilization of the same Alkyl resin emulsions and utilization of the same

2001-01-22

2004-09-07

Niland, Patrick D. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S589000, C524S590000, C524S839000, C524S840000, C525S440030

Reexamination Certificate

active

06787599

ABSTRACT:

The present invention relates to a two-component water paint system and a process for its production.
In conventional aqueous two-component polyurethane paints, CO
2
is formed in the side reaction of the isocyanate with water which leads to the undesired formation of bubbles in the paint film. According to the presently known prior art, such systems allow the reliable production of layer thicknesses of at most 60-80 &mgr;m, depending on the degree of pigmentation and the drying conditions. The two-component water paint system of the present invention on the other hand is especially characterized by low degree of bubble formation. This allows the production of layers having a thickness of at least 120 &mgr;m, often at least 150 &mgr;m without any undesired bubble formation.
Due to ecological problems and the resulting necessity of reducing solvent emissions, water-dilutable paints have been widely used and in many fields of application replaced solvent-containing paints and coatings.
For years, aqueous two-component polyurethane systems have proved to be worthwhile in those fields of application which require a high degree to weathering resistance, corrosion control and chemical resistance. These two-component systems comprise a polyol component and an isocyanate component which are mixed shortly before processing. Usually, oligomeric polyisocyanates, e.g., on the basis of hexamethylene diisocyanate and isophorone diisocyanate, are used as isocyanate components. Hydroxy-functional polyacrylate primary and secondary dispersions, water-soluble or water-emulsifiable polyester and hydroxy-functional polyurethane dispersions are primarily used as polyol components.
These paint systems are increasingly used, e.g., as automotive paints and as lacquers for plastics and furniture. In many cases, the problem of unreliability of the process prevented a more widespread application. In particular, in the case of high layer thicknesses and unfavorable climatic conditions such as, e.g., high humidity, a strong formation of bubbles takes place due to the CO
2
formed in the side reaction of the isocyanate with water during drying.
The object underlying the present invention is to provide a two-component water paint system showing only a low tendency to form bubbles and suitable for producing bubble-free paint layers having a thickness of at least 120 &mgr;m, preferably at least 150 &mgr;m.
This object is achieved by a two-component water paint system comprising an isocyanate component and an aqueous emulsion of a hydroxy-functional alkyd resin. The hydroxy-functional alkyd resin can be obtained from an oleic or fatty acid component, a polyvalent alcohol, a polyether polyol having a molecular weight of 400 to 8,000, a monobasic carboxylic acid and a polycarboxylic acid or the anhydride thereof.
The water paints of the present invention are suitable to be applied to different substrates such as, e.g., plastic materials, metal and wood.
Furthermore, the invention provides a process for the production of the inventive two-component water paint system, comprising:
1) providing an isocyanate component,
2) preparing an aqueous emulsion of a hydroxy-functional alkyd resin comprising:
a) reacting an oleic or fatty acid component, a polyvalent alcohol, a polyether polyol having a molecular weight of 400 to 8,000, a monobasic carboxylic acid and a polycarboxylic acid or the anhydride thereof to obtain a hydroxy-functional alkyd resin,
b) neutralizing the alkyd resin with ammonia or amnine,
c) emulsifying the alkyd resin in water.
Similar alkyd resin emulsions are, in principle, already described, e.g., in U.S. Pat. No. 3,442,835; however, they have been exclusively employed as binding agents in air-drying or baking single-component paints. Single-component paints essentially differ from two-component paints in their level of quality. Two-component polyurethane paints are clearly superior to alkyd-based air-drying single-component paints in terms of mechanical properties such as flexibility and hardness but also with respect to weathering resistance, and resistance to solvents and environmental exposure (cf.
Farbe
&
Lack
, 2/98, page 85).
The alkyd resin of the present invention can be prepared from an oleic or fatty acid component, a polyvalent alcohol, a polyether polyol having a molecular weight of 400 to 8,000, a monobasic carboxylic acid and a polycarboxylic acid or the anhydride thereof.
Preferably, the alkyd resin comprises, 10 to 70 wt.-%, particularly preferred 15 to 40 wt.-%, of an oleic or fatty acid component, 10 to 35 wt.-%, particularly preferred 10 to 30 wt.-%, of a polyvalent alcohol having 2 to 6 hydroxyl groups, 3 to 15 wt.-%, particularly preferred 3 to 8 wt.-%, of a polyether polyol having a molecular weight of 400 to 8,000, in particular 1,000 to 6,000, 0 to 25 wt.-%, particularly preferred 10 to 20 wt.-%, of a monobasic carboxylic acid having 6 to 18 carbon atoms, and 10 to 35 wt.-%, particularly preferred 15 to 30 wt.-%, of a polycarboxylic (e.g., a dicarboxylic) acid having 4 to 10 carbon atoms or the anhydride thereof. Optionally, up to 10 wt.-% of a polybasic carboxylic acid such as, e.g., trimellitic acid or the anhydride thereof can be present in the production of the hydroxy-functional alkyd resin.
Preferably, natural oils or their fatty acids, in particular non-drying oils or their fatty acids, which are characterized by good weathering resistance and a low tendency to yellowing, are used as oleic or fatty acid components. The non-drying oils used in the present invention include all natural oils which are usually employed in the production of alkyd resins. The term ‘non-drying oil’ in this connection refers to a triglyceride of fatty acids which usually have 10 to 24 carbon atoms per molecule and an iodine number of <110. Mixtures are also encompassed by the present invention.
Suitable oils include vegetable oils such as apricot kernel oil, peanut oil, kapok oil, coconut oil, almond oil, olive oil, palm oil and castor oil. Peanut oil, coconut oil and castor oil are preferred.
Preferably the amount of oil used in the present invention can vary from 10 to 70 wt.-%, more preferably 15 to 40 wt.-%, of the final product.
The term ‘oils’ also includes esters of fatty acids with 10 to 24 carbon atoms with triols, such as trimethylolethane and trimethylolpropane, wherein the molar ratio of fatty acid to triol is 3:1. According to the present invention, the oils can be employed as such or as ester-forming precursors such as fatty acids and triols, wherein the ester is formed in situ. Furthermore, mixtures of different oils can be used as oleic or fatty acid components.
Preferably the monobasic carboxylic acid used in the present invention has 6 to 18 carbon atoms per molecule and includes saturated aliphatic acids, saturated cycloaliphatic acids and aromatic acids. Typical examples include isodecanoic acid, isooctanoic acid, cyclohexanoic acid, cyclopentanoic acid, benzoic acid, p-tert.-butylbenzoic acid and long-chain fatty acids derived from substances like coconut oil, palm kernel oil, babassu oil and other fats and oils known in the technical field. Mixtures of these acids can be used as well. Preferably, benzoic acid and p-tert.-butylbenzoic acid are used. Preferably the amount of the monobasic carboxylic acid used in the present invention is about 0 to about 25 wt.-%, more preferably about 10 to about 20 wt.-%, of the alkyd resin. Mixtures of the monobasic carboxylic acids are also encompassed by the present invention.
Preferably the polycarboxylic acids used in the present invention and their anhydrides have 4 to 10 carbon atoms per molecule and include aliphatic, cycloaliphatic and aromatic polycarboxylic acids and their anhydrides. Examples of these acids or anhydrides include maleic acid, fumaric acid, terephthalic acid, isophthalic acid, adipic acid, glutaric acid, azelaic acid and phthalic acid or the anhydrides of these compounds. Preferably the amounts thereof used in the present invention are about 10 to about 35 wt.-%, more preferably about 15 to about 30 wt.-

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