Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2000-12-21
2002-11-05
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S364000, C525S350000, C524S599000, C524S609000, C524S845000, C524S846000, C428S419000
Reexamination Certificate
active
06476183
ABSTRACT:
This application claims priority of European Patent Application No. 99204467.7, filed on Dec. 22, 1999.
The present invention relates to a coating composition comprising a polyunsaturated polymer, a polythiol, and a siccative.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,571,420 discloses a composition comprising a polythiol, a polyene, and a vanadium compound used as a siccative. This composition is an acrylate based coating composition designed to remain flexible after curing and is suitable for use as, e.g., roof mastics. Pendant unsaturation is low, which leads to limited cross-linking. The equivalence ratio of thiol-functional groups to olefinically unsaturated groups in this known composition is high, so the thiol induced drying mechanism is dominant and there is no oxidative drying. Another acrylate based coating composition comprising acrylic polyenes, thiols, and a vanadium based siccative is known from U.S. Pat. No. 4,698,385. A drawback to such acrylic based coating compositions is their instability. When mixed, the components react instantaneously. The reaction is exothermal and releases a lot of thermal energy. The pot life is limited.
In order to prevent problems with, e.g., toxicity, tackiness, and viscostability and for economic reasons, in many cases alkyd based coating compositions are preferable. However, these alkyd based coating compositions are slow drying in comparison with acrylate based coating compositions.
Japanese patent application JP-A 2075669 discloses such an alkyd based coating composition comprising a metal drier and, optionally, a thio-functional silane coupling agent. The thio-functional coupling agent is a mono-thiol which is added to enhance the adhesive properties. Since the coupling agent is a mono-thiol, it cannot serve as a cross-linker.
SUMMARY OF THE INVENTION
The object of the invention is to provide a stable alkyd based coating composition showing fast curing at low temperatures on the one hand and a sufficiently long shelf life, especially for one-pot systems, on the other.
The object of the invention is achieved by means of a coating composition according to the opening paragraph, comprising:
a. an oxidatively drying polyunsaturated condensation product having pendant groups in an amount of more than 20% by weight of the condensation product, the pendant groups comprising unsaturated CC bonds;
b. a polythiol having two or more SH-groups;
c. a siccative;
the equivalence ratio of thiol-functional groups to unsaturated CC bonds being less than 0.3.
DETAILED DESCRIPTION OF THE INVENTION
It has surprisingly been found that the addition of thiol compounds to oxidatively drying polyunsaturated condensation products in the presence of siccatives leads to better curing at low temperatures in comparison with the usual alkyd coating compositions. Though the composition according to the invention shows fast curing, a good shelf life is obtained, even in one-pot systems.
Suitable oxidatively drying polyunsaturated condensation products are alkyd resins. At least a part of the alkyd resin is oxidatively drying as a result of the incorporation of a large number of unsaturated, aliphatic compounds, at least a portion of which is polyunsaturated. The unsaturated aliphatic compounds preferably are unsaturated fatty acids, more particularly polyunsaturated fatty acids. Examples of fatty acids comprising one equivalent of unsaturated CC bonds are myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, and ricinoleic acid and mixtures thereof. Examples of fatty acids comprising two or more equivalents of unsaturated CC bonds include linoleic fatty acid, linolenic fatty acid, elaeostearic fatty acid, licanic fatty acid, arachidonic fatty acid, clupoanodonic fatty acid, nisinic fatty acid, and mixtures thereof. Fatty acids containing conjugated double bonds, such as dehydrated castor oil fatty acid, wood oil fatty acid and/or calendula oil fatty acid can be used as well. Fatty acids derived from soya oil are especially suitable.
Examples of suitable divalent polyol compounds are ethylene glycol, 1,3-propane diol, 1,6-hexane diol, 1,12-dodecane diol, 3-methyl-1,5-pentane diol, 2,2,4-trimethyl-1,6-hexane diol, 2,2-dimethyl-1,3-propane diol, and 2-methyl-2-cyclohexyl-1,3-propane diol. Examples of suitable triols are glycerol, trimethylol ethane, and trimethylol propane. Suitable polyols having more than 3 hydroxyl groups are pentaerythritol, sorbitol, and etherification products of the compounds in question, such as ditrimethylol propane and di-, tri-, and tetrapentaerythritol. Preferably, use is made of compounds having 3-12 carbon atoms, e.g., glycerol, pentaerythritol and/or dipentaerythritol.
Alternatively or additionally, polycarboxylic acids can be used as building blocks for the oxidatively drying polyunsaturated condensation products. Examples of suitable polycarboxylic acids include phthalic acid, citric acid, fumaric acid, mesaconic acid, maleic acid, citraconic acid, isophthalic acid, terephthalic acid, 5-tert. butyl isophthalic acid, trimellitic acid, pyromellitic acid, succinic acid, adipic acid, 2,2,4-trimethyl adipic acid, azelaic acid, sebacic acid, dimerised fatty acids, cyclopentane-1,2-dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, 4-methylcyclohexane-1,2-dicarboxylic acid, tetrahydrophthalic acid, endomethylene-cyclohexane-1,2-dicarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, endoisopropylidene-cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, and butane-1,2,3,4-tetracarboxylic acid. If so desired, the carboxylic acids in question may be used as anhydrides or in the form of an ester, e.g., an ester of an alcohol having 1-4 carbon atoms.
Optionally, the oxidatively drying polyunsaturated condensation product may comprise other building blocks, which may for example be derived from monocarboxylic acids such as pivalic acid, 2-ethylhexanoic acid, lauric acid, palmitic acid, stearic acid, 4-tert.butyl-benzoic acid, cyclopentane carboxylic acid, naphthenic acid, cyclohexane carboxylic acid, 2,4-dimethyl benzoic acid, 2-methyl benzoic acid, benzoic acid, 2,2-dimethylol propionic acid, tetrahydrobenzoic acid, and hydrogenated or non-hydrogenated abietic acid or its isomer. If so desired, the monocarboxylic acids in question may be used wholly or in part as triglyceride, e.g., as vegetable oil, in the preparation of the alkyd resin. If so desired, mixtures of two or more of such monocarboxylic acids or triglycerides may be employed.
Optionally, isocyanates can also be used as building blocks for the oxidatively drying polyunsaturated condensation product. Suitable isocyanates are for example diisocyanates, such as 1,6-hexane diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenyl diisocyanate, and dicyclohexylmethane diisocyanate. Triisocyanates can also be used.
The unsaturated groups in the oxidatively drying polyunsaturated condensation product are preferably introduced by the fatty acids, but may, alternatively or additionally, be introduced by one or more of the polyols, carboxylic acids or anhydrides or other building blocks used, such as fatty mono-alcohols.
The oxidatively drying polyunsaturated condensation product has pendant groups in an amount of more than 20%, preferably more than 50%, by weight of the condensation product. An amount of more than 65% is even more preferred.
A specific example of a suitable alkyd is the condensation product of soya oil, phthalic anhydride, and pentaerythritol.
The alkyd resins can be obtained by direct esterification of the constituent components, with the option of a portion of these components having been converted already into ester diols or polyester diols. Alternatively, the unsaturated fatty acids can be added in the form of a drying oil, such as sunflower oil, linseed oil, tuna fish oil, dehydrated castor oil, coconut oil, and dehydrated coconut oil. Transesterification with the polyols and, optionally, other building blocks will then give the final alkyd resin. This transesterification generally takes place at a tempe
Bakkeren Frank Johannes A. D.
Klaasen Robert Paul
Akzo Nobel N.V.
McGillycuddy Joan M.
Truong Duc
LandOfFree
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