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
1998-11-11
2001-05-08
Sellers, Robert E.L. (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...
C525S934000
Reexamination Certificate
active
06228941
ABSTRACT:
The invention is relating to curable powder coating compositions, and to copolymers of ethylenically unsaturated monomers to be used therein.
More in particular the invention is relating to curable powder coating compositions, comprising an epoxy groups containing copolymer and an acid polyester.
Curable powder compositions are known from e.g. EP-A-0773268; EP-A-0728163; U.S. Pat. No. 5,625,028, and Technical Bulletin of Shell Chemicals “VEOVA mass polymer for outdoor durable powder coatings” August 1991, VM 5.1.
EP-A-0773268 describes acid epoxy curing type powder coating compositions, which comprised
A) an epoxy group containing acrylic resin prepared by polymerizing the monomer mixture, comprising
(a) from 35 to 65 wt % of an epoxy group containing ethylenically unsaturated monomer, and
(b) remainder amount of an ethylenically unsaturated monomer which is different from the monomer (a),
(B) a polycarboxylic acid, and
(C) an antioxidant having a melting point of from 50 to 140° C.
As monomers (b) were exemplified inter alia alkyl methacrylate, wherein alkyl represented methyl, butyl, ethyl, isobutyl, 2-ethylhexyl, lauryl, stearyl, and/or styrene and/or dialkyl esters of unsaturated dibasic acid. The polymerization was actually carried out in an organic solvent like xylene and in the presence of a peroxide radical polymerization catalyst. A component (B) decanedicarboxylic acid was mentioned.
EP-A-0728163 discloses powder coating compositions comprising a solid, particulate mixture of
(a) 60 to 90 wt %, based on the weight of (a) and (b) of an epoxy functional copolymer having a Tg of from 25° C. to 70° C., formed by polymerizing under free radical initiated polymerization conditions:
(i) from 50 to 75 wt %, based on the weight of (i) and (ii) of a glycidyl functional ethylenically unsaturated monomer,
(ii) from 25 to 50 wt %, based on the weight of (i) and (ii) of a copolymerizable ethylenically unsaturated monomer or mixture of monomers free of glycidyl functionality;
said epoxy functional copolymer containing from 3.0 to 5.9 moles of glycidyl groups per kilogram of epoxy functional copolymer;
(b) from 10 to 40 wt %, based on the weight of (a) and (b) of a polycarboxylic acid cross-linking agent;
wherein the ratio of epoxy functionality is 1:0.8 to 1, and wherein the powder coating composition has a melt viscosity of less than 5 Pa.s.
Preferably the copolymerizable ethylenically monomer (ii) is selected from the group consisting of alkyl acrylates, alkyl methacrylates containing from 1 to 20 carbon atoms in the alkyl group, vinyl aromatic compounds and vinyl aliphatic compounds. The comonomer (ii) is preferably isobornyl methacrylate.
In addition as (co)monomer component (iii) can be used a copolymerizable ethylenically unsaturated monomer different from (i) and (ii) and which is more preferably &agr;-methylstyrene dimer.
From U.S. Pat. No. 5,625,028 thermosetting resin compositions are known, which provide coatings that allegedly possessed attractive weathering properties. The compositions comprised a semicrystalline polyester, consisting essentially of diol and/or triol residues and dicarboxylic acid residues. The diol residues had been selected from the group consisting of residues of 1,4-butanediol and 1,6-hexanediol, and the carboxylic acid residues were consisting essentially of residues of 1,4-cyclohexanedicarboxylic acid wherein at least 70% of said residues of 1,4-cyclohexanedicarboxylic acid are in trans form. The polyesters had an acid number of from 30 to 100 and an inherent viscosity of from 0.1 to 0.5 dl/g measured at 25° C. in a 60/40% by weight mixture of phenol/tetrachloroethane at a concentration of 0.5 g/dl.
In Technical Bulletin of Shell Chemicals “VEOVA mass polymer for outdoor durable powder coatings”, reprinted August 1991, VM 5.1 a mass copolymer LR-259 was prepared from inter alia VEOVA 10 vinyl ester monomer, styrene, methyl methacrylate, dimethyl maleate, and glycidyl methacrylate with Trigonox B (di-tert-butyl peroxide).
These copolymers were combined with a carboxyl-functional polyester as curing agent, prepared from hexanediol and decane dicarboxylic acid in a molar ratio of 1 mole of hexanediol per 2 moles decane dicarboxylic acid, under nitrogen purge and in reflux/azeotropic distillation equipment, using toluene as solvent, at a temperature in the range from 130 to 200° C., in the presence of stannous octoate as catalyst and distillation of water and toluene. The polyester resin showed an acid content of 207 mg KOH/g.
It will be appreciated that the present and near future requirements of the industrial coating industry were not met by the curable coating compositions according to the hereinbefore discussed prior publications.
Therefore, due to increasing environmental and economic pressures, there is a strong need for further improved curable resin compositions, which provide an improved combination of physical properties of the cured coating films derived therefrom and meet the requirements from the industrial coating industry in the near future. In particular, it will be more desirable to meet the requirements to be put on automotive top coating compositions and coil coating compositions.
Moreover, it is aimed at to develop coating compositions which preferably can be cured at low temperatures, i.e. in the range of from 120 to 140° C.
Physical properties of the cured coating films, which have to be improved and/or better balanced in the final combination, are inter alia: acid resistance, transparency, colouring resistance during baking, weathering resistance, mar resistance and sealer cracking resistance.
Therefore it is an object of the present invention to provide curable resin compositions, providing cured coating films having improved individual properties and/or improved combinations, as specified hereinbefore.
Another object of the present invention is to provide a process for the preparation of a copolymer component to be incorporated into said curable resin compositions.
Accordingly, as one aspect of the present invention a curable powder coating composition is provided, comprising at least:
(a) a copolymer produced from
ai) from 5 to 10 wt % of an alkyl diester of an ethylenically unsaturated dicarboxylic acid, comprising an alkyl group, having from 1 to 4 carbon atoms and preferably 1 or 2;
aii) from 15 to 55 wt % of a glycidylester of ethylenically unsaturated carboxylic acid;
aiii) from 10 to 45 wt % of a phenylalkylene monomer having from 8 to 12 carbon atoms and preferably 8 carbon atoms;
aiv) from 10 to 35 wti of an alkenyl ester of a branched tertiary carboxylic acid the acid moiety of which contains 9 carbon atoms;
av) from 0 to 45 wtoi of an alkyl ester of an ethylenically unsaturated carboxylic acid, having from 3 to 4 and preferably 3 carbon atoms in the acid moiety, and wherein the alkyl group contains from 1 to 12 carbon atoms;
the respective percentages of the components ai) through av) are relative to the total weight of the copolymer, while the sum of all actual percentages =100%.
b) a blend of a bi) aliphatic or cycloaliphatic di-carboxylic acid comprising from 4 to 16 carbon atoms, preferably from 4 to 14 carbon atoms, and (bii) a polyester resin, derivable from a branched polyhydroxy alkane, having from 5 to 12 carbon atoms and an aliphatic or cycloaliphatic dicarboxylic acid, having from 4 to 16 carbon atoms and preferably from 4 to 14, or an anhydride thereof, in a molar ratio of from 0.2 to 0.4 mole of polyhydroxy alkane per mole of aliphatic or cycloaliphatic dicarboxylic acid, the polyester (bii) having an acid value of from 4500 to 4900 mmol/kg and the blend having an acid value from 5000 to 10,000, while the molar ratio between the acid groups and epoxy groups is in the range of from 0.70:1 to 1.10:1. Preferably the molar ratio between the acid groups and epoxy groups is in the range of from 0.75:1 to 1.00:1 and more preferably from 0.75:1 to 0.85:1.
Suitable monomers to be used as component ai) can be selected from e.g. dimethyl maleate, diethyl maleate, di-n-propyl maleate, di-n-butyl maleate,
De Cock Christian Jean Charles
Gerets Carine Helena Paula
Sellers Robert E.L.
Shell Oil Company
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