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
1982-09-27
1984-03-27
Marquis, Melvyn I.
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...
523333, 523334, 524480, 524475, 524487, 524423, 524436, 524598, C08L 9108
Patent
active
044395752
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for preparing aqueous varnishes containing mineral fillers and/or pigments. Virtually no sedimentation occurs in these varnishes.
It is common practice in the coatings industry to prepare varnishes, in particular also aqueous varnishes, which contain mineral fillers and/or pigments. However, their disadvantage is that, on storing the varnishes, not only fillers but also pigments settle out. Depending on the hardness of the deposit, it is difficult or even impossible to stir up and evenly disperse the solids in the varnish. Inorganic fillers, in addition to wax types, are used in practice as flatting agents for delustering the applied varnish film.
SUMMARY OF THE INVENTION
The present object of the invention was to eliminate the disadvantages listed above.
This object is achieved by a process for preparing aqueous varnishes containing mineral fillers and/or pigments, which comprises allowing a hot wax emulsion in water between 80.degree. C. and 100.degree. C., preferably between 95.degree. C. and 100.degree. C., to flow with vigorous stirring into the aqueous varnish containing mineral fillers and/or pigments and to cover at least some of the filler and/or pigment particles with a wax coating.
The amount of wax added to the aqueous varnish should be at least sufficient to be able to coat with wax all the mineral filler and/or pigment particles present in the finish.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Particularly good results are obtained when 0.5-5 parts by weight of wax are used per 0.1-15 parts by weight of mineral fillers and/or pigments.
Waxes are customary for use as paint additives, namely chiefly to deluster the varnish films. Possible waxes for this purpose are above all those which have a relatively high melting range. Incorporation into the aqueous varnishes is effected by stirring in pulverulent hard wax or from a wax solution or wax pastes.
It was surprising and could not be predicted that a very specific way of incorporating wax into an aqueous varnish would lead to a completely new unexpected property of the finished material, namely a marked lowering of the sedimentation tendency of the solid constituents.
Only when a hot or heated-up wax emulsion at 80.degree. C. to 100.degree. C., preferably 95.degree. C. to 100.degree. C., in water at this temperature is added to an aqueous varnish, is there no sedimentation.
It is important that the aqueous varnish containing mineral fillers and/or pigments is vigorously stirred. As a result, a cone is formed about the stirrer shaft, which cone widens from the bottom to the top and is free of varnish. The most favorable method is to guide the inflowing hot wax emulsion deep into the cone, whereupon the emulsion is most rapidly and most thoroughly dispersed in the varnish.
It has been found that the most favorable result is obtained when the liquid varnish has a temperature of 20.degree. C. If the temperature is lower, the wax in the aqueous varnish becomes more coarse-grained, and if the temperature is higher, the wax becomes too finely dispersed and the surface of the applied film looks spotty and greasy.
If the hot wax emulsion in water is allowed to cool down to a temperature below 80.degree., the emulsified or dissolved wax starts to reprecipitate at the cloud point. If such a cooled-down wax mixture, which in many cases is present as a gel, is incorporated into the aqueous varnish, no sign of any sedimentation-preventing action can be found.
No patent protection is sought for the preparation of a wax emulsion in water. The preparation is effected by stirring wax flakes or wax powder into hot water initially introduced. This is followed by a short period of boiling at 100.degree. C. until a uniform emulsion is obtained. Generally, a 10-20% by weight emulsion is prepared, which can be diluted with more hot water.
Suitable waxes have a melting point above 60.degree. C. and a cloud point on toluene between 35.degree. C. and 45.degree. C. Particularly suitable waxes of this type
REFERENCES:
patent: 3232898 (1966-02-01), Van Loo et al.
patent: 3965058 (1976-06-01), Yurchechen
BASF Farben & Fasern AG
Marquis Melvyn I.
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