Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-09-11
2002-10-15
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S096000, C522S097000, C522S151000, C522S152000, C522S173000, C522S174000, C528S044000, C528S065000, C524S091000, C524S507000, C428S423100, C428S423400, C428S423700, C428S423900, C428S425800, C428S424200
Reexamination Certificate
active
06465539
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The invention relates to an elastic coating system with which dry surfaces can be formed by UV curing of constituents containing (meth)acryloyl groups and by subsequent crosslinking of constituents containing NCO groups with constituents containing active hydrogen. The invention also relates to their use of this coating system for coating, inter alia, components of plastic.
2. Description of the prior art
DE-A-19 800 528 describes coating systems comprising:
a) a urethane (meth)acrylate which contains (meth)acryloyl groups and free isocyanate groups,
b) optionally a further polyisocyanate,
c) a UV initiator which initiates free radical polymerization,
d) one or more compounds which are reactive with isocyanates.
DE-A-19 800 528 furthermore claims a process which is wherein surfaces which can be handled are formed by UV-initiated free radical polymerization and the final properties are formed by a subsequent NCO reaction.
If the coating system described above is applied to a flexible sheet of plastic, the resulting lacquer films indeed have very good optical properties, hardness and resistance to solvents and chemicals, but the films are not elastic enough for use on flexible plastic: If the sheet of plastic is bent by up to 180° at room temperature, the lacquer tears (flexural elasticity test). Similar coatings are described in DE-A 2 809 715.
Accordingly one object of the invention was to provide a coating system which gives elastic coatings which pass the flexural test even at temperatures of −10° C.
It has been found that the incorporation of particular polyester diols into component a) of a coating system according to DE-A-19 800 528 results in very elastic coatings.
SUMMARY OF THE INVENTION
The invention relates to coating systems containing:
a) a urethane (meth)acrylate which contains (meth)acryloyl groups and free isocyanate groups, (NCO),
b) optionally a further polyisocyanate,
c) a UV initiator which initiates free radical polymerization,
d) one or more compounds which are reactive with isocyanates,
wherein the urethane (meth)acrylate contains as a constituent a diol which contains ester groups and has an average number-average molecular weight of 176 to 2,000 in an amount of 1 to 65 wt.%, based on the amount of other constituents of the urethane (meth)acrylate.
DETAILED DESCRIPTION OF THE INVENTION
The present coating system is preferably prepared in two components, component I preferably comprising constituents a) and b) and component II comprising constituents c) and d).
In order to achieve stability to weathering, it is possible to add to component II:
e) a UV absorber with an absorption range up to max. 390 nm and
f) an HALS stabilizer;
furthermore:
g) conventional lacquer additives, such as flow or deaerating agents,
h) catalysts to accelerate the NCO reaction.
Components I and II can each contain , for dilution, a solvent which is inert in the sense of crosslinking.
Component I and component II are combined such that a ratio between the NCO groups and groups which are reactive with NCO of 2:1 to 0.8:1, preferably 1.2:1 to 0.8:1, is established.
The invention furthermore provides the use of the coating systems for lacquering of substrates such as e.g. plastic, metal, wood, textiles, leather or films and of substrates which have already been coated.
Compounds according to a) are prepared from alcohols containing (meth)acryloyl groups and di- or polyisocyanates. The diol according to the invention containing ester groups can be here both a constituent of the alcohols containing (meth)acryloyl groups, a constituent of the polyisocyanates, and a further constituent. Preparation processes for urethane (meth)acrylates are known and are described e.g. in DE-A-1 644 798, DE-A-2 115 373 or DE-A-2 737 406. For the urethane methacrylates according to the invention containing free isocyanate groups, the molar ratio of NCO groups of the di- or polyisocyanates to hydroxyl (OH) groups of the alcohols containing (meth)acryloyl groups and the OH groups of the diol containing ester groups is from 1:0.2 to 1:0.8, preferably 1:0.3 to 1:0.6. It is also possible to use a mixture of a urethane (meth)acrylate which contains no free NCO groups with a urethane (meth)acrylate containing free isocyanate groups as long as this mixture corresponds to the abovementioned ratio of NCO groups to OH groups of its building units. Alcohols containing (meth)acryloyl groups are to be understood as including both esters, containing a free hydroxyl group, of acrylic acid or methacrylic acid with di-hydric alcohols, such as, 2-hydroxyethyl, 2- or 3-hydroxypropyl or 2-, 3- or 4-hydroxybutyl (meth)acrylate, and mixtures of such compounds. Monohydric alcohols containing (meth)acryloyl groups or reaction products which comprise such alcohols and are obtained by esterification of n-hydric alcohols with (meth)acrylic acid are also possible. The variable n represents an integer or a statistically average fraction of greater than 2 to 4, preferably 3, and from (n-0.6) to (n-2.2), preferably from (n-0.8) to (n-1.2), particularly preferably (n-1) mol (meth)acrylic acid being employed per mol of the alcohols mentioned. These compounds and product mixtures include, for example, the reaction products of i) glycerol, trimethylolpropane or pentaerythritol, or low number-average molecular weight alkoxylation products of such alcohols, such as, ethoxylated or propoxylated trimethylolpropane, such as, the addition product of ethylene oxide on trimethylolpropane of OH number 550, or mixtures of such at least trihyric alcohols with dihydric alcohols, such as, ethylene glycol or propylene glycol, with ii) (meth)acrylic acid in the molar ratio mentioned.
These compounds have a number-average molecular weight of 116 to 1,000, preferably 116 to 750, and particularly preferably 116 to 158.
The reaction products of these monohydric alcohols containing (meth)acryloyl groups with &egr;-caprolactone can furthermore be employed. These products then contain the diol according to the invention containing ester groups. The reaction products of hydroxyalkyl (meth)acrylates, such as, 2-hydroxyethyl, 2- or 3-hydroxypropyl or 2-, 3- or 4-hydroxybutyl (meth)acrylate, with &egr;-caprolactone are preferred. Such products are obtainable, for example, as Tone® Monomer 100 from Union Carbide.
These compounds have a number-average molecular weight of 230 to 3,000, preferably 230 to 1,206, and particularly preferably 344 to 572.
Suitable di- or polyisocyanates include (cyclo)aliphatic araliphatic and aromatic compounds. The (cyclo)aliphatic compounds are preferred, including butylene-diisocyanate, hexamethylene-diisocyanate (HDI), isophorone-diisocyanate (IPDI), trimethylhexamethylene-diisocyanate (=2,2,4- and/or 2,4,4-trimethylhexamethylene-diisocyanate), di(isocyanatocyclohexyl)methane, isocyanatomethyl-1,8-octane-diisocyanate or derivatives thereof with a urethane, isocyanurate, allophanate, biuret, uretdione or iminooxadiazinedione structure and mixtures thereof.
Polyisocyanates containing urethane groups which have isocyanurate structural units and are prepared from diisocyanates and diols containing ester groups, the preparation of which is described e.g. in EP-A-336 205, are preferred.
These products then contain the diol according to the invention containing ester groups. 1,6-Diisocyanatohexane and polyester diols of average number-average molecular weight from 176 to 2,000, preferably 350 to 950, particularly preferably 500 to 800 are preferred as starting products. These known polyester diols are built up from diols and dicarboxylic acids. Suitable diols for the preparation of the polyester diols include dimethylolcyclohexane, ethanediol, 1,2- and 1,3-propanediol, 1,2-, 1,3 and 1,4-butanediol and neopentylglycol. Mixtures thereof with 1,6-hexanediol are preferred, and 1,6-hexanediol is particularly preferred as the sole diol component.
Suitable dicarboxylic acids include aromatic dicarboxylic acids, such as phthalic acid, isophthalic acid and terephthalic acid; cycloalip
Fischer Wolfgang
Kobusch Claus
Küttner Wolfram
Weikard Jan
McClendon Sanza L
Roy Thomas W.
Seidleck James J.
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