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
1997-05-05
2000-02-29
Reddick, Judy M.
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...
523201, 524458, 524521, 428500, 428515, 428520, 428522, 428523, C08F 216
Patent
active
060310383
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an aqueous polymer emulsion containing composition 1 of compounds (monomers) having at least one ethylenically unsaturated group by the free radical aqueous emulsion polymerization method to a conversion of at least 90% by weight, based on the monomer composition 1 to be polymerized, (polymerization stage 1) and then polymerizing, in the presence of the product mixture of polymerization stage 1, a composition 2 of compounds (monomers) having at least one ethylenically unsaturated group by the free radical aqueous emulsion polymerization method (polymerization stage 2), with the proviso that composition 1 alone would give a polymer 1 whose glass transition temperature tends to the limit Tg.sup.1 with increasing molecular weight, composition 2 alone would give a polymer 2 whose glass transition temperature tends to the limit Tg.sup.2 with increasing molecular weight, Tg.sup.i is from 40 to 90% by weight, based on the total amount of the compositions 1 and 2, and adhesion-promoting monomer which differs from these monomers and has at least one ethylenically unsaturated group and at least one group of the general ##STR1## where X is O or S and together form a bridging C.sub.2 -C.sub.4 -alkylene group which may be monosubstituted or disubstituted by C.sub.1 -C.sub.4 -alkoxy and/or hydroxyl, preferably from 1 to 5, very particular from 1 to 3, % by weight, based on the total amount of the monomers to be polymerized, reversibly protected aldehyde groups, with the proviso that the molar ratio R of all the groups I contained in the aqueous polymer emulsion to the total molar amount of unprotected and/or reversibly protected aldehyde groups contained in the aqueous polymer emulsion in the form of compounds B is from 0.1:1 to 10:1, and
The present invention furthermore relates to processes for the preparation of novel aqueous polymer emulsions and their use for coating, adhesive bonding, sealing and impregnating, their use as binders for coating materials and in particular glazes being preferred.
Aqueous polymer emulsions are fluid systems which contain polymer particles distributed in stable disperse form as the disperse phase in the aqueous dispersing medium. The diameter of the polymer particles is in general mainly from 0.01 to 5 .mu.m, frequently mainly from 0.01 to 1 .mu.m.
As in the case of polymer solutions on evaporation of the solvent, aqueous polymer emulsions have the ability to form transparent polymer films on evaporation of the aqueous dispersing medium, and it is for this reason that said emulsions are widely used as binders, for example for surface coatings or materials for coating leather.
In contrast to the polymer solution, however, the type of dispersed polymer and the temperature at which film formation takes place determine whether an aqueous polymer emulsion forms a cohesive transparent film or a brittle, opaque pulverizable layer after evaporation of the water. The lowest temperature at which a transparent film without cracks is just formed is to be referred to below as the minimum film formation temperature (MFT) of the relevant aqueous polymer emulsion. No film formation takes place below the MFT (cf. Ullmanns Encyklopadie der technischen Chemie, Vol. 19, 4th edition, Verlag Chemie, Weinheim (1980), page 17).
It is generally known that aqueous emulsions of polymers which essentially contain only polymerized monomers whose homopolymers have low glass transition temperatures Tg (in this publication, Tg is the limit of the glass transition temperature to which, according to G. Kanig, Kolloid-Zeitschrift & Zeitschrift fur Polymere, Vol. 190, page 1, equation 1, the glass transition temperature tends with increasing molecular weight, determined by the DSC method (Differential Scanning Calorimetry, 20.degree. C./min, midpoint); the Tg values for the homopolymers of most monomers are known and are stated, for example, in Ullmann's Encyclopedia of Industrial Chemistry, VCH Weinheim, 1992, fifth edition, Vol. A21, page 169; other sources of glass transition temperatu
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Baumstark Roland
Portugall Michael
BASF - Aktiengesellschaft
Reddick Judy M.
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