Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-11-04
2001-02-20
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, C522S090000, C522S167000, C522S169000, C522S173000, C528S048000, C528S059000, C528S067000, C540S200000, C540S202000, C540S356000, C540S364000, C544S067000, C544S221000
Reexamination Certificate
active
06191181
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new urethane acrylates and to their use as a binder component in coating compositions that are curable with high-energy radiation.
2. Description of the Prior Art
Urethane acrylates are known as coating binders that are curable with high-energy radiation. A review is given in P. K. T. Oldring (Ed.), Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints, Vol. 2, 1991, SITA Technology, London, pages 73-123. Urethane acrylates constitute high-grade coating binders for substrates, such as wood, metal and plastics and for mineral substrates.
Very different polyisocyanates can be used for the production of urethane acrylates. (Cyclo)aliphatic polyisocyanates are used for the production of urethane acrylates when it is necessary for the resulting coatings to be resistant to yellowing and weathering. Although hexamethylene diisocyanate is also disclosed as a suitable diisocyanate, e.g., in DE-A 2,115,373, it can be stated that this is a purely hypothetical disclosure. This diisocyanate cannot be used in the formulations described in this reference due to the tendency of the resulting urethane acrylates to crystallize. To be useful the lacquer binders have to be liquid under normal conditions.
DE-A 4,027,743 describes urethane acrylates prepared from hexamethylene diisocyanate, which are modified with ester alcohols such that they are liquid at room temperature. However, at temperatures below 10° C., these high- to medium viscosity products become turbid.
It is known from DE-A 4,232,013 that the following methods have been used to suppress the crystallization of urethane acrylates based on hexamethylene diisocyanate: the use of mixtures with other diisocyanates e.g. isophorone diisocyanate, the incorporation of alcohol components containing ester groups, and the incorporation of sterically-hindered mono- or dihydric alcohols that have a branched molecular structure. All of these measures restrict the options for production, and thus restrict the possibility of varying other properties, and generally result in high raw material costs.
Higher functionality polyisocyanates prepared from hexamethylene diisocyanate may also be used to prepare urethane acrylates. Thus, DE-A 3,737,244 describes urethane acrylates which are prepared from polyisocyanates containing isocyanurate groups. The higher functionality of these products results in coatings having better resistance properties. However, the tendency of these products to crystallize is even greater than for urethane acrylates prepared from hexamethylene diisocyanate.
An object of the present invention is to provide new, low-viscosity urethane acrylates which are resistant to yellowing, do not crystallize even at temperatures below 10° C. and are prepared from polyisocyanates having a functionality greater than 2.
Surprisingly, this object may be achieved in accordance with the present invention by using polyisocyanates containing iminooxadiazine dione groups to prepare urethane acrylates that exhibit a considerably reduced tendency to crystallize.
SUMMARY OF THE INVENTION
The present invention relates to urethane acrylates, which may be cured with high-energy radiation, in which the urethane acrylates are the reaction product of
a) a polyisocyanate component containing 20 to 100 mole %, based on the moles of the polyisocyanate component a), of iminooxadiazine dione group-containing polyisocyanate trimers corresponding to formula A
wherein
R
1
, R
2
and R
3
are the same or different and represent linear or branched, C
4
-C
20
(cyclo)alkyl groups and
X is the same or different and represents isocyanate groups or isocyanate group-containing radicals that also contain iminooxadiazine dione, isocyanurate, uretdione, urethane, allophanate, biuret or oxadiazine trione groups, wherein R
1
, R
2
and R
3
are attached to a nitrogen atom, with
b) an alcohol component containing at least one monobasic, hydroxy-functional, linear or branched C
1
-C
12
alkyl ester of (meth)acrylic acid.
The present invention further relates to the use of the urethane acrylates as binder components for coating compositions that are curable with high-energy radiation.
DETAILED DESCRIPTION OF THE INVENTION
The isocyanate trimers of formula A, which are used for the production of the urethane acrylates according to the invention are known from EP-A 798,299 (U.S. Pat. No. 5,914,383, herein incorporated by reference) or German Patent Application DE-A 19 734 048.2 (copending application U.S. Ser. No. 09/126,303, herein incorporated by reference). The isocyanate trimers which are preferably used are those produced by the partial oligomerization of hexamethylene diisocyanate (HDI), 1,3-bis(isocyanatomethyl)-cyclohexane (H
6
XDI) or isophorone diisocyanate (IPDI). It is immaterial whether or not the diisocyanate starting material to be oligomerized is completely separated from the reaction products after partial oligomerization.
The isocyanate trimers of formula, which are preferably used for the production of the urethane acrylates according to the invention, are those having a viscosity at 23° C. of 300 to 3000 mPa·s, preferably 500 to 2000 mPa·s, more preferably 500 to 1500 mPa·s and most preferably 1000 to 1500 mPa·s; an NCO content of preferably 15 to 30% by weight, more preferably 20 to 25% by weight; and a content of unreacted starting diisocyanates, of less than 5.0% by weight, preferably less than 1.0% by weight and more preferably less than 0.5% by weight.
Alcohol component b) is selected from one or more monobasic hydroxy-functional esters of (meth)acrylic acid. The latter is to be understood to include both esters of acrylic acid and esters of methacrylic acid. Examples include the hydroxy-group containing esters obtained by reacting acrylic acid or methacrylic acid with dihydric alcohols, such as 2-hydroxyethyl, 2- or 3-hydroxy-propyl or 2-, 3- or 4-hydroxybutyl (meth)acrylates.
Also suitable are monohydric alcohols containing (meth)acryloyl groups and reaction products substantially containing monohydric alcohols which are obtained by the esterification of n-hydric alcohols with (meth)acrylic acid, wherein “n” preferably represents a whole number, or a fractional number ranging from greater than 2 to 4, preferably 3, and wherein (n−0.8) to (n−1.2), preferably (n−1) moles of (meth)acrylic acid are used per mole of alcohols. Mixtures of different alcohols can also be used as the alcohols.
Examples of these compounds include the reaction products of i) glycerol, trimethylolpropane and/or pentaerythritol, or low molecular weight alkoxylation products of these alcohols (such as ethoxylated or propoxylated trimethylolpropane, e.g. the addition product of ethylene oxide and trimethylolpropane, OH number 550). Also suitable are mixtures of at least trihydric alcohols of this type with dihydric alcohols such as ethylene glycol or propylene glycol for example, with (ii) (meth)acrylic acid in the preceding molar ratio.
These compounds have a number average molecular weight of 116 to 1000, preferably 116 to 750 and more preferably 116 to 158.
Mono- or dihydric alcohols which have a molecular weight of 100 to 300, preferably 130 to 200, contain ether and/or ester groups and have a branched structure can optionally be used as a further constituent of the alcohol component. Examples include 2,2-diethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, (3-hydroxy-2,2-dimethyl-propyl)-3-hydroxy-2,2-dimethyl propionate and trimethylolpropane formal.
The reaction of starting components a) and b) can be carried out in the absence of solvents or in solvents which are inert to isocyanates and hydroxyacrylates. Example include acetone, 2-butanone, ethyl acetate, n-butyl acetate and low molecular weight esters of (meth)acrylic acid, which are known by the generic term “reactive thinners” for curing under the effect of high-energy radiation (e.g., those described in P. K.
Fischer Wolfgang
Richter Frank
Weikard Jan
Zwiener Christian
Bayer Aktiengesellschaft
Gil Joseph C.
McClendon Sanza L.
Roy Thomas W.
Seidleck James J.
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