Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
1999-10-18
2002-07-02
Short, Patricia A. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyester
C428S413000, C428S418000, C525S438000, C525S440030, C525S443000, C525S444000
Reexamination Certificate
active
06413648
ABSTRACT:
The invention relates to resins which can be used in can and coil coating compositions.
As is evident from the articles ‘Pulver-Bandbeschichten bei 60 m/min’ by Dr Graziano (JOT 1996/8, pp. 34-39) and ‘Polyester based Powder Coatings with reference to Coil Coating’ by P. Binda (ECCA, Autumn Congress, Brussels, Nov. 18-19, 1996), there is a need for powder paint systems that can be used in coil coating processes at application rates of, for example, 120 m/min. The reactivity of a powder paint composition is too slow for achieving such high rates. The powder paint application techniques (spraying) are also too slow in comparison with the roll application techniques used in can and coil coating processes. Another drawback is that powder paint layers are applied as relatively thick layers. Powder paint resins do moreover generally not comply with foodstuffs legislation. Furthermore, the solid resins having a high glass transition temperature (Tg) used in powder paint compositions are not soluble in organic solvents as used in the coil coating industry.
It is the object of the invention to provide a resin system that can be processed with the aid of the application techniques currently used on an industrial scale in the coil coating industry.
The resin system according to the invention is characterised in that the system comprises a mixture of at least two polymers wherein at least one polymer has a glass transition temperature greater than about 45° C. and wherein the polymers are soluble in organic solvents.
Suitable polymers include for example polyesters and polyacrylates.
Preferably the polymers are polyesters.
Preferably, the glass transition temperatures (Tg) of the polymers are different. This difference is generally greater than 5° C.
The molecular weights (M
n
) of the polymers are usually between about 2000 and about 15000 and preferably they range between about 3000 and about 8000.
Preferably, the resin having a Tg greater than 45° C. is amorphous.
Examples of suitable organic solvents which are used for can and coil coating applications include aromatic hydrocarbon resins (for example the ‘Solvesso’ types), N-methylpyrolidone, xylene, propylene glycol monomethylether, methylpropylene glycol acetate, dibasic ester, isophoron, ethyl ethoxypropionate, ethylene-propylene glycol acetate and/or butyl glycol.
Generally, the second polymer has a dry solids content between about 30% and about 100%. The Tg of the second polymer is generally lower than about 40° C.
However it is also possible to apply a second polymer having a Tg higher than about 40° C.
Preferably, the second polymer has a dry solids content of at least 50% and a Tg of less than 10° C.
The resins may be linear or branched.
The resin system according to the invention can be applied with the present application techniques in can and coil coating processing, because the solid high Tg resins dissolve during the preparation of the paint or varnish and can be applied as solvent borne coating paints. The use of these systems implies also low transport costs and less storage volume before the preparation of the paint.
Coatings with specifically desired properties in the wide application range of both can coatings and coil coatings can be obtained by selecting the appropriate choice of the starting resins in the mixture.
To replace a very wide range of different prior art solvent-bearing resins it is only necessary to make a selection from only a few systems according to the invention because the coating properties can be adjusted by changing the mixing ratio between the resins in the mixture.
Another advantage is the possibility of a flexible choice of solvents because the high Tg resins are soluble in a wide range of solvents.
The weight proportion of the polymer having a Tg higher than 45° C. is generally at least 25% and preferably at least 50% (relative to the polymers).
Preferably, the resin system is amorphous because of the desired solubility characteristics.
The polymers are soluble in the organic solvents so that they remain homogeneous and that they show no crystallisation for a period of at least 7 days.
Depending on the desired use, the acid numbers of the polyesters range between about 0 and about 100 mg of KOH/gram of resin and the hydroxyl numbers of the polyesters range between 0 and about 150 mg of KOH/gram of resin.
Systems according to the invention can be used in existing coil coating application lines at rates of up to, for example, 150 m/min and dry layer thicknesses between, for example, 1 and 60 &mgr;m.
The polymer mixture according to the invention has to be cured with a crosslinker.
Examples of suitable crosslinkers include compounds containing epoxy groups, compounds containing amino groups and compounds containing isocyanate groups. The crosslinker can be selected depending on the desired use.
Examples of suitable compounds containing epoxy groups are bisphenol A epoxy resins (for example Epikote 828™, Epikote 1001™ and Epikote 1004™ from Shell), hydrogenated bisphenol A epoxy compounds, aliphatic epoxy compounds, epoxidised alkyd resins, epoxidised oils (for example epoxidised linseed oil or soybean oil), epoxidised borates and triglycidyl isocyanurate. Preferably a bisphenol A epoxy resin is used as an epoxy group containing crosslinker.
The carboxyl:epoxy equivalent ratio is generally between 0.85:1 and 1:0.85, preferably between 0.9:1 and 1:0.9.
Examples of suitable amino resin crosslinkers are benzoguanamine, melamine and urea-formaldehyde resins. The polyester:amino resin weight ratio is generally between 95:5 and 60:40 (based on solid resin).
Examples of suitable crosslinkers containing (blocked) isocyanate groups are hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophoron diisocyanate (IPDI), tetramethylxylene diisoycanate (TMXDI), 3,4 isocyanatomethyl-1methyl-cyclohexylisocyanate (IMCI) and their dimers and trimers. Preferably these crosslinkers are blocked.
It is possible to combine the polymers with the same crosslinker. If desired, it is also possible to apply different crosslinkers or mixtures of crosslinkers.
The resins may contain a solid catalyst fused in it. It is also possible to mix a liquid catalyst or a catalyst solution into the paint formulation comprising the resin mixture.
Suitable catalysts for acid-epoxy curing are described by Madec et al. in ‘Kinetics and Mechanisms of Polyesterifications’, Advances in Polymer Science, 182-198 (1985). Examples of suitable classes include N-dialkylamine pyridines, tertiary amines, imidazoles, guanidines, cyclic amines and latent amine catalysts. The catalysts can be blocked if so desired.
Examples of suitable catalysts for curing an OH-functional polyester and an amino resin as a crosslinker include strong acids such as sulphonic acids, mono and dialkyl acid phosphate, butyl phosphate and butyl maleate.
Suitable sulphonic acids include for example paratoluene sulphonic acid, methane sulphonic acid, nonyl benzene sulphonic acid, dinonyl naphthalene disulphonic acid and dodecyl sulphonic acid.
Suitable catalysts for curing an OH-functional polyester and an isocyanate based crosslinker include, for example, dibutyl tin dilaureate and zinc octoate.
If catalysts are present, they are generally present in amounts of between about 0.1 and about 5 wt. % (relative to the polyester).
Suitable polyalcohols for preparing the polyesters include ethylene glycol, diethylene glycol, butanediol (1,4), hexanediol (1,6), neopentyl glycol,
2-
methyl-1,3-propanediol, 1,3-butanediol, 1,3-propanediol, 1,2-propanediol, 2-ethyl-2-butyl-1,3-propanediol, trimethylpentanediol, hydroxypivalic neopentyl glycol ester, tricyclodecane dimethanol, cyclohexane dimethanol, bisphenol A bishydroxyethyl ether, trimethylolpropane and/or pentaerythritol.
Suitable examples of acids for preparing the polyesters include isophthalic acid, terephthalic acid (dimethyl terephthalate ester), adipic acid, sebacic acid, hexahydroterephthalic acid (CHDA), decane dicarboxylic acid, 5-6-butylisophthalic acid and/or dimerised fatty acids or acid anhydrides such as pht
Besamusca Johannes Wilhelmus
Heyenk Albert
DSM NV
Short Patricia A.
LandOfFree
Can and coil coating resins does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Can and coil coating resins, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Can and coil coating resins will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2882051