Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-08-08
2003-04-15
Rotman, Al (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S129000, C560S132000, C560S201000
Reexamination Certificate
active
06548696
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to low monomer 1:1-monoadducts from hydroxy(meth)-acrylates and diisocyanates and a process for their manufacture.
2. Discussion of the Background
Because of their heterofunctionality, monoadducts from hydroxy(meth)acrylates and diisocyanates are valuable, versatile synthesis building blocks. Application fields are, for example, the preparation of acryl functionalized derivatives containing urethane groups formed by a reaction of the isocyanate group with monofunctional reagents or the manufacture of the respective acryl functionalized UV-curable resins by converting the isocyanate group with polyfunctional reaction partners. Further, it is possible to prepare polyisocyanates, for example through radically initiated homopolymerization or copolymerization of the (meth)acryl group. The reactivity of the NCO groups of these polymerizates allows easy access to customized polymers with unique properties under mild conditions.
The patent literature describes the use of olefinic unsaturated urethanes with an isocyanate function, for example, for the manufacture of crosslinkers (DE 35 01 493, U.S. Pat. No. 4,861,853) and self-crosslinking systems (U.S. Pat. No. 4,861,853), also on an aqueous basis (EP 0519 513).
Adducts from diisocyanates and hydroxy(meth)acrylates are traditionally obtained by converting the starting material in a molar ratio of 1:2. In this process the product has to be a mixture of heterofunctional monoadduct, bisadduct (1:2-adduct) and residual monomer in a ratio of approximately 1:1:1. By using an excess quantity of diisocyanate, the bisadduct content in the mixture can be suppressed. On the other hand, the residual monomer proportion rises. Employing an excess quantity of hydroxy(meth)acrylate causes an inverse effect to set in. The bisadducts no longer fulfill the desired heterofunctionality criterion, as opposed to the respective monoadducts. Bisadducts reduce the quality of the monoadduct and also have an effect on the quality and properties of the desired end products. The same considerations also apply to the excess starting diisocyanate that remains in the adduct. In addition, diisocyanates are very reactive compounds. Because of this, representatives of this substance class are to be classified as toxic. Therefore, a high residue of monomer diisocyanate in the product should be avoided at all costs.
It would be advantageous and desirable if the heterofuntionalized monoadduct formed by the conversion of hydroxy(meth)acrylates and diisocyanates did not exhibit the above disadvantages.
EP 0 623 591 describes the manufacture of olefinic unsaturated isocyanates, obtained by the conversion of diisocyanates with olefinic unsaturated alcohols (NCO/OH ratio of 4:1 to 40:1) and the subsequent removal of the excess starting isocyanate by short-path evaporation. The obtained products are low monomer, heterofunctional monoadducts, which, depending on the dimension of the isocyanate excess quantity, exhibit a more or less reduced bisadduct content. An attempt to transfer the manufacturing conditions of EP 0 623 591 to the products that are the subject of the present invention was unsuccessful. At the latest during the short-path evaporation process there was a gelling of the product mixture. Even when stabilizers such as hydroquinone, triphenyl phosphite or 2,2,6,6-tetramethyl-1-oxyl-piperidine were employed, gelling of the product mixture could not be stopped.
SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to provide a process for the manufacture of low monomer 1:1-monoadducts from hydroxy(meth)acrylates and diisocyanates in which premature gelling of the product mixture is prevented.
It is another object of the present invention to provide low monomer 1:1-monoadducts from diisocyanates and hydroxy(meth)acrylates with a free diisocyanate content of less than 0.7% by weight and a free NCO content of 10.4-16.4% by weight.
This and other objects of the present invention have been achieved by providing a low monomer 1:1-monoadduct from a diisocyanate and a hydroxy(meth)acrylate, obtained by converting 5-20 mol diisocyanate with 1 mol hydroxy(meth)acrylate at a temperature of 40-120° C. in the presence of at least one inhibitor until said hydroxy (meth)acrylate is fully converted;
subsequently separating a non-converted diisocyanate from a reaction product by short-path distillation at 80-220° C./0.1-10 mbar;
feeding air, nitrogen monoxide or oxygen or a mixture containing (a) air, oxygen or nitrogen monoxide and (b) a proportion of 1-90% by volume of carbon dioxide, nitrogen, an inert gas or a mixture thereof through a reaction apparatus as an inhibitor gas;
wherein said monoadduct has a free diisocyanate content of less than 0.7% by weight and a free NCO content of 10.4-16.4% by weight.
Further, the above objects have been achieved by providing a process for the manufacture of the low monomer 1:1-monoadduct from diisocyanate and hydroxy(meth)acrylate.
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, it has been found that it was possible to prevent premature gelling of the product mixture when the conversion of the diisocyanate and the hydroxy(meth)acrylate and the short-path evaporation are carried out in the presence of a combination of suitable inhibitors and inhibitive gases. The term “conversion” within the context of the present invention means “reaction” and “converting” means “reacting”.
The present invention relates therefore to low monomer 1:1 monoadducts obtained from diisocyanates and hydroxy(meth)acrylates with a free diisocyanate content of less than 0.7% by weight and a free NCO content of 10.4-16.4% by weight, obtained by converting 5-20 mol diisocyanate with 1 mol hydroxy(meth)acrylate at a temperature range of 40-120° C. in the presence of inhibitors. The monoadducts of the present invention have a content of free diisocyanate of below 0.7% by weight. They are difunctional monomers containing urethane groups with a reactive isocyanate group and a polymerizable double bond. Both functional groups can enter chemical reactions independent of one another. The respective other function remains unaffected and is available for further conversions.
The reaction of diisocyanate with hydroxy(meth)acrylate to obtain the monoadducts of the present invention is carried out until the acrylate components are fully converted. Subsequently the non-converted diisocyanate is separated from the reaction product by short-path distillation at 80-220° C./0.1-10 mbar. The temperature during the distillation includes all values and subvalues therebetween, especially including 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 and 210° C. The pressure during the distillation includes all values and subvalues therebetween, especially including 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 and 9.5 mbar. Air, nitrogen monoxide, oxygen or a mixture of (a) air, oxygen or nitrogen monoxide, and (b) 1-90% by volume of carbon dioxide, nitrogen or inert gases or mixtures of these gases are fed through the reaction apparatus as an inhibitor gas.
Preferred isocyanates are aliphatic, cycloaliphatic and araliphatic, i.e. aryl substituted aliphatic diisocyanates, such as those described in Houben-Weyl, Methoden der Organischen Chemie, Volume 14/2, pp. 61-70 and in an article by W. Siefken, Justus Liebig's Annalen der Chemie 562, pp. 75-136, the relevant portions each of which are herein incorporated by reference. Preferred examples are 1,2-ethylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 2,2,4-(2,4,4)-tri-methyl-1,6-hexamethylene diisocyanate (TMDI), 1,9-diisocyanato-5-methylnonan, 1,8-diisocyanato-2,4-dimethyloctane, 1,12-dodecandiisocyanate, &ohgr;,&ohgr;′-diisocyanatodipropyl-ether, cyclobuten-1,3-diisocyanate, cyclohexan-1,3- and 1,4-diisocyanate, 3-isocyanato-methyl-3,5,5-trimethyl-cyclohexylisocyanate (isophorone diisocyanate, IPDI), 1,4-diisocyanatomethyl-2,3,5,6-tetramethyl-cyclohexane, decahydro
Hayen Lothar
Kohlstruk Stephan
Spyrou Emmanouil
Degussa - AG
Reyes Hector M.
Rotman Al
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