Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1994-12-13
1997-04-22
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524589, 524601, 5253286, 5253287, 525377, 525437, 525452, 525460, C08F 830
Patent
active
056230141
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a dispersion or solution of a free radical polymer, polycondensate or polyadduct which consists of from 0.001 to 20% by weight of aldehyde groups --CHO or keto groups --CO-- and contains, as a crosslinking agent, a compound having at least two H.sub.2 N--O--groups or oxime ether groups derived therefrom.
Copolymers which are used in coating materials or adhesives are often crosslinkable copolymers. For example, protective coatings or adhesive coatings having good elastic properties, high cohesion, ie. internal strength, and high resistance to chemicals and solvents can be obtained by crosslinking.
For crosslinking, a crosslinking agent which reacts with functional groups of a copolymer is generally added to the copolymer.
Possible crosslinking agents are, for example, 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 polymerization. Similar adhesive formulations are also described in U.S. Pat. No. 4,396,738 and DE-A-31 12 117.
However, the disadvantage of these aqueous formulations is the poor shelf life. The polyisocyanate must therefore be dispersed in water shortly before its use as a crosslinking agent and mixed with the copolymer.
A longer shelf life can be achieved by reacting the isocyanate groups with blocking agents, for example oximes, caprolactams, phenols or dialkyl maleates. The resulting block 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 above about 130.degree. C.
Conventional aqueous adhesive formulations containing polyisocyanates as crosslinking agents therefore either have a short shelf life and hence can be used only as the two-component system or undergo crosslinking only at high temperatures.
Aqueous dispersions which have a long shelf life and undergo crosslinking at room temperature after removal of the solvent are disclosed in EP-A-3516. These dispersions contain polyhydrazides which react with carbonyl-containing monomers present as polymerized units in the copolymer.
There is in principle a need for further dispersions which undergo crosslinking at room temperature, in order to be able to provide alternatives to the polyhydrazide crosslinking. Furthermore, these dispersions have good performance characteristics, for example good adhesion, in particular wet adhesion to a very wide range of substrates.
It is an object of the present invention to provide dispersions or solutions of crosslinkable copolymers, which dispersions or solutions have a long shelf life, contain a crosslinking agent and are crosslinkable at room temperature.
We have found that this object is achieved by the dispersion or solution defined above and its use as a coating material or adhesive.
The crosslinking of the keto- or aldehyde-containing free radical polymers, polycondensates or polyadducts with the crosslinking agents which contain at least two H.sub.2 N--O-- groups of oxime ether groups derived therefrom occurs on removal of the liquid phase of the dispersion or solution and probably takes place according to the following schemes:
with hydroxylamine derivatives ##STR1##
with oxime ethers ##STR2##
When crosslinking agents having H.sub.2 N--O-- groups or oxime ether groups derived therefrom are used, the same, crosslinked end product is therefore obtained. The crosslinking reaction is an oximation in the first case and a transoximation in the second case.
Further embodiments relate to the components of the novel dispersion or solution and their preparation and their use.
The novel dispersion or solution contains a polymer, polycondensate or polyadduct which consists of from 0.001 to
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Aydin Oral
Bauer Gerhard
Bott Kaspar
Harreus Albrecht
Ley Gregor
BASF - Aktiengesellschaft
Lipman Bernard
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