Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1998-09-09
2002-10-01
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S411100, C428S425800, C428S458000, C427S487000, C427S496000, C427S500000, C427S508000, C427S514000, C522S090000, C522S096000
Reexamination Certificate
active
06458459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to radiation-curable formulations which comprise at least one aliphatic, urethane-functional prepolymer having at least two ethylenically unsaturated double bonds and at least one monofunctional ester of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid with a monofunctional alkanol, said prepolymer having as a structural element at least one saturated 5- or 6-membered carbocycle or one or 6-membered heterocycle with one or two oxygens in the ring.
Radiation-curable compositions have acquired widespread importance in the art, especially as high-grade surface coating materials. By radiation-curable compositions are meant formulations which include ethylenically unsaturated polymers or prepolymers and which, directly or after a physical drying step, are cured by the action of high-energy radiation, for example by irradiation with UV light or by irradiation with high-energy electrons (electron beams).
2. Description of the Related Art
Particularly high-grade coatings are obtained if the radiation-curable composition employed comprises formulations that contain an ethylenically unsaturated, urethane-functional polymer or prepolymer. Ethylenically unsaturated urethane-functional polymers and prepolymers are known, for example, from 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. Because of the high viscosity of ethylenically unsaturated, urethane-functional polymers and prepolymers, such compositions are often admixed with ethylenically unsaturated compounds of low molecular mass in order to reduce the viscosity. These compounds, like the ethylenically unsaturated polymers and prepolymers, are polymerized in the course of curing and so incorporated into the coating. They are therefore referred to as reactive diluents. Hence the properties of the resulting coatings are determined both by the ethylenically unsaturated polymer or prepolymer employed and by the reactive diluent. For optimum coating properties, furthermore, it is necessary to harmonize the ethylenically unsaturated polymers or prepolymers with the reactive diluents.
DE-A-27 260 41 discloses radiation-curable compositions comprising at least one polyetherurethane which is modified at the ends with acrylate and/or methacrylate groups, a low molecular mass polyfunctional acrylate with ether groups, and hydroxyalkyl acrylates. Radiation-curable compositions of this kind lead to coatings having increased flexibility.
EP-A-508 409 discloses radiation-curable compositions which comprise at least one ethylenically unsaturated polyesterurethane and at least one nonaromatic, low molecular mass substance having at least one, preferably at least two, (meth)acryloyl groups, as crosslinker (=reactive diluent). Radiation-curable compositions of this kind lead to coatings having improved weathering stability.
A fundamental problem with the radiation-curable compositions of the prior art is that, although it is possible by selecting and harmonizing the components (prepolymer and reactive diluent) to improve individual in-use properties such as coating hardness, flexibility and weathering resistance, this is always at the expense of other properties.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide radiation-curable compositions which lead to coatings having balanced profiles of properties, with great hardness, high flexibility and high weathering resistance, and which at the same time feature low application viscosity and a high curing rate.
We have found that this object is achieved, surprisingly, by a radiation-curable composition which comprises at least one aliphatic, urethane-functional prepolymer and at least one monofunctional ester of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid with a monofunctional alkanol which has as a structural element at least one saturated 5- or 6-membered carbocycle or one corresponding heterocycle having one or two oxygens in the ring.
DETAILED DESCRIPTION OF THE INVENTION
The present invention consequently provides radiation-curable formulations which comprise
i) at least one aliphatic, urethane-functional prepolymer which on average has at least two ethylenically unsaturated double bonds per molecule (=component A),
ii) at least one monofunctional ester of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid with a monofunctional alcohol which has as a structural element at least one saturated 5- or 6-membered carbocycle or one saturated 5- or 6-membered heterocycle with one or two oxygens in the ring (=component B), and
iii) if desired, di- or polyfunctional esters of an &agr;,&bgr;-ethylenically unsaturated carboxylic acid with an aliphatic di- or polyol (=component C).
In accordance with the invention, the aliphatic, urethane-functional prepolymer is free from aromatic structural elements such as phenylene or naphthylene or substituted derivatives thereof. Component B contains no nitrogens.
In general, the compositions of the invention contain from 20 to 90% by weight, preferably from 30 to 80% by weight, and in particular from 40 to 70% by weight, of component A, from 10 to 80% by weight, preferably from 20 to 60% by weight, and in particular from 30 to 50% by weight, of component B, from 0 to 40% by weight and, preferably, from 0 to 30% by weight, of component C and up to 20% by weight, based on the overall weight of components A, B and C, of customary auxiliaries, with the proviso that the amounts by weight of components A, B and C add up to 100% by weight. In general, the weight of components B and C is in the range from 10 to 80% by weight, preferably from 20 to 70% by weight and, in particular, from 30 to 60% by weight, based in each case on the overall weight A+B+C.
Depending on the desired profile of properties the compositions of the invention comprise component B and component C or exclusively component B. Where high coating hardness is desired the formulation of the invention preferably comprises component B and component C. If instead greater value is placed on high flexibility, component C may be omitted. In addition, as the amount of component C increases, the viscosity of the formulations of the invention is improved. In the first case the ratio of component B to component C is preferably in the range from 20:1 to 1:1 and, in particular, in the range 10:1 to 1.5:1.
In general, component A is composed essentially of one or more aliphatic structural elements, urethane groups and at least two ethylenically unsaturated structural units. Aliphatic structural elements include both alkylene groups, preferably with 4 to 10 carbons, and cycloalkylene groups, preferably with 6 to 20 carbons. Both the alkylene and cycloalkylene groups can be substituted one or more times by C
1
-C
4
-alkyl, especially by methyl, and may include one or more nonadjacent oxygens. The aliphatic structural elements may be connected to one another by way of quaternary or tertiary carbons, by way of urea groups, biuret, uretdione, allophanate, cyanurate, urethane, ester or amide groups or by way of ether oxygen or amine nitrogen. Component A is preferably free from uretdione or allophanate groups and from amine nitrogen. Furthermore, component A in accordance with the invention has at least two ethylenically unsaturated structural elements. These are preferably vinyl or allyl groups, which can also be substituted by C
1
-C
4
-alkyl, especially methyl, and which are derived in particular from &agr;,&bgr;-ethylenically unsaturated carboxylic acids and/or their amides. Particularly preferred ethylenically unsaturated structural units are acryloyl and methacryloyl groups, such as acrylamido and methacrylamido and, in particular, acryloxy and methacryloxy. With particular preference, component A has at least three ethylenically unsaturated structural elements per molecule.
Very particular preference is given to components A in which the
Beck Erich
Menzel Klaus
Schwalm Reinhold
Völlinger Frank
BASF - Aktiengesellschaft
Jackson Monique R.
Thibodeau Paul
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