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
2000-11-20
2002-09-17
Cain, Edward J. (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...
C524S221000, C524S227000, C524S228000, C524S802000, C524S803000
Reexamination Certificate
active
06451899
ABSTRACT:
The present invention relates to aqueous formulations comprising at least two different particulate polymers P1 and P2 as aqueous dispersions.
Aqueous formulations based on aqueous polymer dispersions find diverse application owing to the film-forming properties of the polymers they comprise; for example, as binders in pigmented formulations, such as emulsion paints, sealing compounds, coating compositions or asphalt compositions, in pigment-free formulations, such as varnishes and polishes, as adhesives and base materials for adhesives, and in compositions for coating paper, fibers or leather.
Formulations based on aqueous polymer dispersions frequently include two different polymers in order to adjust the properties of the polymer films which result when the polymer dispersions are dried.
U.S. Pat. No. 5,208,285 discloses an improvement to the wet adhesion of polymer films based on polyvinyl acetate dispersions by adding small amounts of a polymer dispersion whose polymer has cyclic urea groups.
EP-A 716 131 describes pigmented coating compositions comprising a very fine polymer dispersion and a coarser polymer dispersion as binders. The combination of fine and coarser dispersions improves the gloss of the coatings.
EP-A 466 409 describes a blend of two aqueous polymer dispersions whose polymers differ in their glass transition temperatures. The combination of a polymer having a glass transition temperature—<20° C. and a polymer having a glass transition temperature<20° C. produces a combination of improved film formation with higher blocking resistance of the resulting coatings.
For preparing aqueous polymer dispersions and for their further processing to appropriate aqueous formulations, it is advantageous for the polymer dispersions to be of low viscosity. The ready-to-use aqueous formulations based on the aqueous polymer dispersions, however, are frequently required to have a viscosity that lies well above the inherent viscosity of the aqueous polymer dispersions present in the formulations. Adjusting the viscosity of aqueous formulations is generally accomplished by adding a thickener. By thickeners are meant substances of high molecular mass, usually organic polymers, which swell in the liquid to be thickened and, in doing so, undergo transition to viscous, colloidal or true solutions (see Römpp, Chemielexikon, 9th edition, Thieme Verlag, Stuttgart, p.4488). Thickeners for aqueous solvents have polar functional groups, such as OH, COOH or carboxamide groups, which form hydrogen bonds with the water molecules and so bring about thickening.
The prior art aqueous formulations based on aqueous polymer dispersions always require relatively large amounts of thickeners in order to establish an appropriate processing viscosity. The use of relatively large amounts of thickeners in aqueous formulations based on polymer dispersions, however, is undesirable. Firstly, there are regularly instances of incompatibility of the polymeric thickener with the film-forming polymers of the aqueous formulations, so impairing the mechanical properties of the polymer films that result from the dispersed polymers. Secondly, thickeners frequently also act as flocculants on the dispersed polymers. Thirdly, thickeners for aqueous formulations are in many cases soluble in water, or hygroscopic, and so make the polymer films more sensitive to water.
It is an object of the present invention to provide formulations based on aqueous polymer dispersions which require smaller amounts of thickeners in order to establish an appropriate processing viscosity than do the prior art formulations.
We have found that this object is achieved and, surprisingly, that aqueous formulations based on a blend of at least two different polymer dispersions have the desired properties, if the dispersed polymers present in them differ in their hydro phobicity.
The hydrophobicity of a polymer, which is fundamentally difficult to determine experimentally (see Wu, J. Macromol. Sci-Revs. Macromol. Chem. C10 (1), 1974, 1-73), is given indirectly by the water-solubility of the monomers of which the polymer is composed. Polymers composed of at least 20% by weight of monomers having a water-solubility in the range from 10 to 100 g/l (at 25° C.) and of less than 80% by weight of monomers having a water-solubility below 10 g/l (at 25° C.) can be classed as hydrophilic polymers. Polymers composed of at least 80% by weight of monomers having a water-solubility<10 g/l (at 25° C.) and of less than 20% by weight of monomers having a water-solubility in the range from 10 to 100 g/l (at 25° C.) can be classed as hydrophobic polymers.
The present invention therefore provides aqueous formulations comprising:
i. at least one hydrophilic particulate polymer P1, as an aqueous dispersion, which is composed of ethylenically unsaturated monomers M comprising:
from 20 to 100% by weight of at least one monoethylenically unsaturated monomer M1 having a water-solubility in the range
from 10 to 100 g/l (at 25° C. and 1 bar),
from 0 to 80% by weight of one or more monoethylenically unsaturated monomers M2 having a water-solubility below 10 g/l (at 25° C. and 1 bar), and
from 0 to 20% by weight of one or more monomers M3 which are different from the monomers M1 and M2, and
ii. at least one hydrophobic particulate polymer P2, as an aqueous dispersion, which is composed of ethylenically unsaturated monomers M′ comprising:
from 0 to 20% by weight of one or more monoethylenically unsaturated monomers M1′ having a water-solubility in the range from 10 to 100 g/l (at 25° C. and 1 bar),
from 80 to 100% by weight of at least one monoethylenically unsaturated monomer M2′ having a water-solubility below 10 g/l (at 25° C. and 1 bar), and
from 0 to 20% by weight of one or more monomers M3′ which are different from the monomers M1′ and M2′, and
where the glass transition temperature T
g
1 of the polymer P1 is less than 10 K different from the glass transition temperature T
g
2 of the polymer P2 and where the proportions by weight of the monomers M1, M2 and M3 and of the monomers M1′, M2′ and M3′ respectively add up in each case to 100% by weight. Values for the water-solubility of ethylenically unsaturated monomers are tabulated for example in Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. Vol. 21 A, VCH Publishers 1992, p. 159-161.
Examples of preferred monomers M1 and M1′ are methyl methacrylate, methyl acrylate, ethyl acrylate, n- and iso-propyl acrylate, vinyl acetate, acrylonitrile, methacrylonitrile and N-vinylcaprolactam, especially methyl methacrylate, acrylonitrile and vinyl acetate.
Preferred monomers M2 and M2′ include C
2
-C
18
-alkyl methacrylates, such as ethyl methacrylate, n- and isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate and 2-ethylhexyl methacrylate, C
4
-C
18
-alkyl acrylates, such as n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and stearyl acrylate, vinylaromatic monomers such as styrene, &agr;-methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl esters of aliphatic C
3
-C
18
monocarboxylic acids, such as vinyl propionate, vinyl butyrate, vinyl valerate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl decanoate, vinyl pivalate, vinyl laurate, vinyl stearate and also commercial monomers VEOVA® 5-11 (VEOVA® X is a tradename of Shell and stands for vinyl esters of &agr;-branched aliphatic carboxylic acids having X carbon atoms, also referred to as Versatic® X acids), C
2
-C
6
olefins, such as ethylene and isobutene, conjugated dienes, such as butadiene and isoprene, vinyl chloride and vinylidene chloride.
The hydrophilic polymers P1 of the invention preferably contain from 20 to 90% by weight and especially from 30 to 85% by weight of monomers M1 and from 10 to 80% by weight and especially from 15 to 70% by weight of monomers M2 in copolymerized form.
The hydrophobic polymers P2 of the invention preferably contain not more than 15% by weight an
Dittrich Uwe
Pakusch Joachim
Röckel Harald
Roser Joachim
Zhao Cheng-Le
BASF - Aktiengesellschaft
Cain Edward J.
Yeh James T.
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