Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1998-09-21
2001-01-23
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C427S385500, C522S090000, C522S174000, C528S059000, C528S067000, C528S075000, C528S090000, C528S174000, C560S330000, C560S335000, C560S355000
Reexamination Certificate
active
06177535
ABSTRACT:
Preparing radiation-curable, urethane-functional prepolymers
The present invention relates to a process for preparing radiation-curable, urethane-functional prepolymers, in which an isocyanate-functional component A is reacted with an OH-containing component B. The present invention also relates to the radiation-curable, urethane-functional prepolymers obtainable by this process.
Radiation-curable, urethane-functional prepolymers are employed widely in the art, examples of their applications as photoresists and as components in high-grade coating materials. They generally include at least two ethylenically unsaturated double bonds per molecule, which polymerize under the action of high-energy radiation, such as UV light or electron beams, and so form a network of high molecular mass. Coatings based on radiation-curable, urethane-functional prepolymers generally feature high mechanical and chemical resistance.
An overview of ethylenically unsaturated, urethane-functional prepolymers is given, for example, in P. K. T. Oldring (ed.), Chemistry and Technology of UV- and EB-Formulations for Coatings, Inks and Paints, Vol. II, SITA Technology, London, 1991, pp. 73-123.
DE-A-4 007 146 discloses, for example, urethane acrylate compounds which are obtainable by reacting polyisocyanates with hydroxyalkyl acrylates and then reacting the products with primary or secondary amines. The coatings obtainable using these compounds are notable for high elasticity and high surface hardness. The reaction of isocyanates with polyols and hydroxy-alkyl acrylates is described, for example, in DE 2726041 A, U.S. Pat. No. 4,260,703 and U.S. Pat. No. 4,481,093 and the reaction of isocyanates with hydroxyalkyl acrylates in JP 63297369 and JP 59157112.
The urethane acrylates of the prior art are often problematic in terms of their stability on storage. Especially when stored at low temperatures, they agglomerate and become cloudy. This problem can be remedied in principle by diluting the urethane acrylates with appropriate solvents. Inert solvents, however, must generally be removed before curing. This additional operation is undesirable on the ground not least of cost. Dilution with reactive diluents—by which are meant ethylenically unsaturated compounds of low molecular mass which polymerize on curing with the ethylenically unsaturated prepolymers and so are incorporated into the coating—is naturally limited by the desired profile of properties of the coatings. In general, even formulations comprising urethane-functional prepolymers and reactive diluents turn cloudy after just a few days.
It is an object of the present invention to provide radiation-curable, urethane-functional prepolymers having improved stability on storage. Moreover, coatings based on such prepolymers should possess little propensity to yellowing, a high level of hardness and a fairly high flexibility.
We have found that this object is achieved, and that urethane-functional prepolymers having the desired profile of properties are obtained, if an isocyanate-functional component A, which comprises at least one trifunctional isocyanate A1 with or without a difunctional isocyanate A2, is reacted with an OH-containing component B, which comprises at least one ethylenically unsaturated, OH-containing compound.
The present invention accordingly provides a process for preparing radiation-curable, urethane-functional prepolymers by reacting an isocyanate-functional component A with an OH-containing component B, wherein the component A comprises at least one trifunctional isocyanate compound A1 with or without one or more difunctional isocyanate compounds A2 and the OH-containing component B comprises at least one ethylenically unsaturated compound B1 having at least one reactive OH group with or without different OH-containing compounds B2, where either component A embraces two different isocyanate compounds A1 or one isocyanate compound A1 and at least one isocyanate compound A2 or component B embraces at least two different compounds B1. The present invention also provides the radiation-curable, urethane-functional prepolymers obtainable by the process of the invention.
In one embodiment of the process of the invention therefore component B comprises at least two different compounds B1 if component A contains no difunctional isocyanate compound A2.
In a further embodiment, component A comprises a mixture of at least two different isocyanate compounds A1a and A1b and, if desired, at least one isocyanate compound A2, but preferably no compound A2. The prepolymers thus obtainable are also accessible by mixing a prepolymer of an isocyanate compound A1a and component B with a prepolymer of an isocyanate A1b and component B. In this embodiment of the process, particularly storage-stable prepolymers are obtained.
Suitable trifunctional isocyanate compounds A1 include both compounds having a defined empirical formula, having 3 NCO groups per molecule, and low molecular mass oligomers having a number-average molecular weight Mn<1000, and containing on average about 3.0 isocyanate groups per oligomer molecule.
The compounds A1 are preferably selected from the biurets and cyanurates of diisocyanates and from the adducts of diisocyanates with trifunctional aliphatic alcohols. Suitable diisocyanates are generally of 4 to 22 carbons. The diisocyanates are normally selected from aliphatic, cycloaliphatic and aromatic diisocyanates, examples being 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, 1,2-, 1,3- and 1,4-diisocyanatocyclohexane, 2,4- and 2,6-diisocyanato-1-methylcyclohexane, 4,4′-bis(isocyanatocyclohexyl)methane, isophoronediisocyanate (=1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane), 2,4- and 2,6-tolylene diisocyanate, tetramethylene-p-xylylene diisocyanate (=1,4-bis(2-isocyanatoprop-2-yl)benzene), 4,4′-diisocyanatodiphenylmethane, preferably 1,6-diisocyanatohexane and isophorone diisocyanate, and mixtures thereof. Preferred compounds A1 embrace the cyanurates and biurets of aliphatic diisocyanates, especially the cyanurates. Particularly preferred compounds A1 are the isocyanurate and the biuret of isophorone diisocyanate and the isocyanurate and the biuret of 1,6-diisocyanatohexane. Examples of adducts of diisocyanates with trifunctional alcohols are the adducts of the abovementioned diisocyanates with glycerol, trimethylolethane and trimethylolpropane, examples being the adduct of tolylene diisocyanates with trimethylolpropane or the adducts of 1,6-diisocyanatohexane or isophorone diisocyanate with trimethylpropane and/or glycerol.
If component A comprises a mixture of two different isocyanate compounds A1a and A1b, this is preferably a mixture of a biuret and an isocyanurate of one of the abovementioned aliphatic diisocyanates, or a mixture of such a biuret or isocyanurate with an adduct of one of the abovementioned aliphatic diisocyanates with a trifunctional aliphatic alcohol. In this context, it is particularly preferred to use the same diisocyanate both for the biuret and for the isocyanate and the adduct. With very particular preference, use is made of a mixture of the biuret and the cyanurate of 1,6-diisocyanatohexane (hexamethylene diisocyanate) or isophorone diisocyanate.
Examples of suitable difunctional isocyanate compounds A2 are the abovementioned diisocyanates, preferably 2,4- and 2,6-tolylene diisocyanate, tetramethyl-p-xylylene diisocyanate, diphenylmethane 4,4′-diisocyanate and, in particular, isophorone diisocyanate.
The compounds B1 of component B are generally selected from the esters of ethylenically unsaturated carboxylic acids, such as acrylic, methacrylic, crotonic, acrylamidoglycolic, methacrylamidoglycolic and vinylacetic acid with a di- or polyol having preferably 2 to 20 carbons, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, 1,5-pentan
Beck Erich
Koniger Rainer
Lokai Matthias
Menzel Klaus
Paulus Wolfgang
BASF Aktiengesellchaft
Cooney Jr. John M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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