Copolymerizable oxime ethers and copolymers containing them

Details Copolymerizable oxime ethers and copolymers containing them Copolymerizable oxime ethers and copolymers containing them

1994-12-09

1995-10-17

Schofer, Joseph L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

564256, C08F 2034

Patent

active

054592160

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to oxime ethers of the general formula ##STR2## where A is a divalent link, R.sup.1 may be hydrogen or C.sub.1 -C.sub.4 -alkyl and R.sup.2 and R.sup.3 independently of one another are each C.sub.1 -C.sub.10 -alkyl, C.sub.1 -C.sub.10 -alkoxy, C.sub.5 -C.sub.10 -cycloalkyl or C.sub.5 -C.sub.10 -aryl, each of which may furthermore contain 1-3 nonadjacent nitrogen, oxygen or sulfur atoms as hereto atoms in the carbon chain or in the carbon ring and may be substituted by from one to three C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -alkoxy groups, R.sup.2 or R.sup.3 may be hydrogen or R.sup.2 and R.sup.3 together form a bridge of 3 to 14 carbon atoms, where some of the carbon atoms may also be part of an aromatic ring.
Copolymers which are used in coating materials or adhesives are often crosslinkable copolymers. By means of crosslinking, for example, protective coatings or adhesive coatings having good elastic properties, high cohesion and high resistance to chemicals and to solvents can be obtained.
For crosslinking, a crosslinking agent which reacts with functional groups in the copolymer is generally added to the copolymers. Examples of possible crosslinking agents are polyisocyanates, which react with hydroxyl or amino groups.
DE-A-35 21 618 discloses corresponding aqueous adhesive formulations in which polyisocyanates dispersed in water are added, as crosslinking agents, to aqueous dispersions of copolymers obtained by free radical copolymerization. Similar coating formulations are also described in U.S. Pat. No. 43 96 738 and DE-A-31 12 117.
However, the disadvantage of these aqueous formulations is the poor shelf-life. The polyisocyanate therefore must not be dispersed in water and mixed with the copolymer until shortly before it is used as a crosslinking agent.
A longer shelf-life can be achieved by reacting the isocyanates groups with blocking agents, for example oximes, caprolactam, phenols or dialkyl maleates. The resulting blocked polyisocyanates undergo hydrolysis in aqueous dispersion only to a minor extent.
DE-A-38 07 555 relates to such a diisocyanate which is blocked with oximes, is dispersed in water and is suitable as an additive for polymers dispersed in water.
However, crosslinking reactions occur only after elimination of the blocking agent at above about 130.degree. C.
Conventional aqueous adhesive formulations containing polyisocyanates as crosslinking agents are therefore either unstable during storage and can hence be used only as 2-component systems or undergo crosslinking only at high temperatures.
Aqueous dispersions which have a long shelf-life and crosslink at room temperature after removal of the solvent are disclosed in EP-A-3516. These dispersions contain polyhydrazides which react with carbonyl-containing monomers polymerized in the copolymer.
It is in principle desirable to develop further dispersions having a long shelf-life and crosslinking at room temperature, in order to provide alternatives to polyhydrazide crosslinking.
It is an object of the present invention to provide crosslinkable copolymers which have a long shelf-life in dispersion or solution, even in the presence of a crosslinking agent, and can be crosslinked at room temperature.
We have found that this object is achieved by the copolymerizable oxime ethers defined above and a process for their preparation.
We have also found copolymers which contain the copolymerizable oxime ethers, and the use of the copolymers as coating materials or adhesives.
The copolymers which contain the copolymerizable oxime ethers crosslink with crosslinking agents containing aldehyde or keto groups probably by the following mechanism: ##STR3##
A in the general formula I is preferably a linear or branched hydrocarbon chain of 2 to 12, in particular 2 to 8, carbon atoms which may be interrupted by 1 to 3, in particular 1 or 2, nonadjacent oxygen atoms or a C.sub.5 -C.sub.10 -cycloalkylene or C.sub.5 -C.sub.10 -arylene ring. It is particularly preferably a linear or branched hydrocarbon chain of 2 to 8 ca

REFERENCES:
patent: 4350801 (1982-09-01), Grasshof
patent: 4396738 (1983-08-01), Powell et al.
P 120:299510 pp. 20-22.

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