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...
Reexamination Certificate
1999-03-09
2001-05-08
Szekely, Peter A. (Department: 1714)
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...
C524S507000, C524S508000, C524S509000, C524S510000, C524S513000, C524S522000, C524S523000
Reexamination Certificate
active
06228931
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to externally emulsified low-solvent aqueous binders, processes for their preparation and use, as well as to coating compositions, adhesives, and the like comprising such binders.
2. Description of Related Art
Water-dilutable binders obtained by mixing or partial condensation of a polycarboxyl component which is soluble in water following neutralization of the carboxyl groups with a resinous polyhydroxyl component which per se is not dilutable in water and featuring favorable viscosity characteristics on dilution with water are described in a series of patents; for example in Austrian Patent B 328 587, Austrian Patent B 379 607, Austrian Patent B 388 738 and Austrian Patent B 388 382.
Austrian Patent B 328 587 specifies acrylate copolymers as a usable polycarboxyl component; however, on the basis of the customary monomer composition described therein, it is impossible to formulate any coating materials which would be useful in practice, since these coating materials have disadvantages in their application properties, such as the tendency toward blistering and toward running during stoving operations, even at low film thicknesses. German Patent DE-C 43 15 593 describes externally emulsified two-component coating compositions comprising a water-insoluble, hydroxyl-containing polyester or polyacrylate resin which is emulsified by adding anionic, cationic or nonionic emulsifiers in a proportion of from 0.1 to 1% relative to the mass of the resin dissolved in an organic solvent, and comprising a liquid organic polyisocyanate.
In general, externally emulsified aqueous binder systems, including the system described in DE-C 43 15 593, exhibit considerable disadvantages which considerably restrict the scope for their application. For example, they possess inadequate shear stability; the preparation of stable pigment pastes is difficult if not impossible; the resistance of the coating films produced with them is inadequate, especially to water; and, finally, their stability on storage is inadequate. “Externally emulsified” means that a substance which itself is not water-emulsifiable has been carried into an aqueous emulsion by virtue of addition of an emulsifying agent. In contrast to that, “internally emulsified” means that a substance which in itself is not water-soluble or water-dispersible has been modified by chemical incorporation of moieties that have hydrophilic character, thereby rendering the (modified) substance water-dispersible or water-emulsifiable.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an externally emulsified low-solvent aqueous binder comprising: a water-insoluble synthetic resin component A; and an emulsifier resin B. The resin B has functional groups comprising carboxyl groups and hydroxyl groups. The resin B is a reaction product of a water-insoluble synthetic resin B1 comprising hydroxyl groups as functional groups, a synthetic resin B2 comprising carboxyl groups as functional groups, and a neutralizing agent for the carboxyl groups of B. The amount of the neutralizing agent is such that said neutralizing agent is able to neutralize from 5 to 200% of the carboxyl groups of B. In further accordance with the present invention, there is provided a process for preparing an externally emulsified low-solvent aqueous binder comprising: (i) mixing components a water-insoluble synthetic resin containing hydroxyl functional groups B1 and a synthetic resin containing carboxyl functional groups B2 in bulk or dissolved in organic solvents, (ii) removing the solvent by applying subatmospheric pressure and heating until the solids content is at least 85% by mass, (iii) maintaining the mixture at a temperature from 90° to 150° C. until the reaction product is homogeneously emulsifiable in a mass ratio of 3 parts of resin to 7 parts of water, (iv) neutralizing the reaction product by adding a neutralizing agent in an amount sufficient to neutralize from 5 to 200% of the carboxyl groups that have remained following the reaction, (v) adding a water-insoluble synthetic resin A, and (vi) emulsifying the mixture in water. In the context of this invention, the term “low solvent” means a composition that has a mass fraction of 25% or less of solvents, preferably less than 20 %. Preferably, the components B1 and B2 are used in such amounts that the mass fraction of the hydroxyl-containing synthetic resin B1 is from 85 to 55% of the sum of the masses of the resins B1 and B2 and the mass fraction of the carboxyl-containing synthetic resin B2 is from 15 to 45%, the sum of the mass fractions adding to 100%.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention relates accordingly to externally emulsified, low-solvent aqueous binders which possess the aforementioned disadvantages to a reduced extent if at all, comprising a water-insoluble synthetic resin component A and an emulsifier resin B, whose functional groups include carboxyl groups and hydroxyl groups and which is an esterification-prepared product of reaction of a water-insoluble synthetic resin B1 comprising hydroxyl groups as functional groups and of a synthetic resin B2 comprising carboxyl groups as functional groups, and a neutralizing agent for the carboxyl groups of B, the amount of the neutralizing agent being such that it is able to neutralize from 5 to 200%, preferably from 25 to 150%, of the carboxyl groups of B. Preferably, the synthetic resin B2 is chosen such that following at least partial neutralization, it can be emulsified homogeneously in water.
The present binders are preferably externally emulsified, low-solvent film-forming binders comprising a water-insoluble resin component and as emulsifier resin, a carboxyl- and hydroxy-functional reaction product of a hydroxy-functional polymer (polyhydroxy component) which is preferably essentially insoluble in water and a carboxyl-functional polymer (polycarboxyl component) which is preferably soluble in water following at least partial neutralization. The water-insoluble resin component to be emulsified is preferably added to the emulsifier resin prior to its emulsification in water and then, following at least partial neutralization of the carboxyl groups with amines or alkalis, the mixture obtained is advantageously transformed into an aqueous emulsion by adding water to it or by stirring it into water.
In particular, the emulsifier resin B suitably has an acid number of from 25 to 100 mg/g, preferably from 30 to 80 mg/g.
The emulsifier resin B can be prepared in any way desired and is preferably prepared such that in a first step, a carboxyl-functional polymer B2 (polycarboxyl component), which preferably has an acid number of from 40 to 350 mg/g, in particular from 100 to 250 mg/g, is mixed with an essentially water-insoluble, hydroxy-functional polymer B1 (polyhydroxy component) preferably having a hydroxyl number of from 40 to 250 mg/g and, if desired, an epoxy group content, based on the mass of the solid, of from 35 to 260 mmol/kg.
It may be possible to employ the polymers B1 and B2 without solvent or dissolved in an organic solvent, with the preferred proviso that the mixture has an acid number of at least 25 mg/g. Subsequently, in a second step, the solvent is removed by applying a subatmospheric pressure and heating until the mass fraction of solids is at least 85% by mass. In a third step the mixture is reacted at a temperature of from 90° to 150° C. until a sample neutralized with a base can be emulsified homogeneously with water in a mass ratio of resin B to water of 3:7.
The externally emulsified low-solvent aqueous binders can then b
Gossak Kurt
Kreissmann Ingo
Luttenberger Johann
Wilfinger Werner
Foley & Lardner
Szekely Peter A.
Vianova Resins AG
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