1~ 292 - O.~. ooso/3s267 Aqueous polymer dispersions having a long shelf life The present invention relates to aqueouS polymer dispersions ~hich have a long shelf life and ar~ obtain-able by dispersing a mixture of t~o copolymers, one or both of which contain a copolymerizable carbonyl compound as a component, in the presence of a polyhydrazide as a crosslinking agent, a process for the preparation of such dispersions and their use for the preparation of finishes and coating materials.
Aqueous polymer dispersions which contain car-bonyl groups and can be crosslinked by means of poly-hydrazides are known and are descr;bed in, for example, EP 0,003,516. These dispersions are prepared by the process of emulsion polymerization (primary dispersions are formed in this process), ;n wh;ch hydroPhilic assis-tants (emulsifiers) are used, resulting in relatively high water absorption of the films producecd from the dispersions.
German Laid-Open Application DOS 3,536,261 des-cribes polymeric compositions ~hich have a long shelflife in aqueous solutions or dispersions, are obtainable by reacting polymeric organic compounds contain;ng car-boxyl and carbonyl groups ~ith polyhydrazides in ~he presence of monoketones and/or monoaldehydes and are soluble or dispersible in water after neutralization of some or all of the carbonyl groups. The dispersions pre-pared in this manner are referred to as secondary dis-persions. In order to achieve an adequate shelf life, substantial a~ounts of volatile monoketones and/or mono-aldehydes are required, ~hich evaporate on drying. Thisis undesirable because of the odour and for toxicological reasons. Furthermore, because of the content of organic solvents, thick coatings dry out very slowly.
It is an object of the present invention to pre-pare aqueous polymer dispersions which have a long shelflife, are free of emulsifiers and of volatile monoketones and/or monoaldehydes and, on drying, give crosslinked, 13~ 2 non-blocking films which cannot be completely dissolved again with organic solvents.
It has been found that this object is achieved by an aqueous polymer dispersion essentially Eree of emulsi-fiers and having a long shelE life, which is obtainable by:
(a) polymerizing a mixture of:
. 15 to 50% by weight of a copolymer (A) containing (I) 1.5 to 15% by weight of copolymerizable compounds of 3 to 10 carbon atoms which contain a carboxyl or carboxylic anhydride group, (II) 30 to 98-5% by weight of Cl-~20-alkyl acrylates or methacrylates, (III) 0 to 60% by weight of vinylaromatics, (IV) 0 to 20% by weight of copolymerizable carbonyl compounds and (V) 0 to 20% by weight of further copolymerizable organic compounds not stated under (I) to (IV) and . 50 to 85% weight of a copolymer (s) containing 40 to 100% by weight of the monomers (II) and 0 to 60% by weight of one or more of the monomers (III) to (V), wherein the copolymers ~A) and (B) together contain, as components, up to 65% by weight of alkyl (meth)acrylates (II) whose homopolymers have glass transition temperatures of less then 0C, and wherein at least one of the copolymers (A) and (B) contains the monomers (IV) as components, 1301~92 - 2a - s in an organic solvent in a manner such that, first, one of the two copolymers (A) and (B) is prepared by poly-merization of the components, the other copolymer is produced in the resulting polymer solution, (b) then dispersing the polymer mixture in water by adding ammonia, (c) distilling off the solvent; and (e) adding at least one polyhydrazide (C) to the dispersion.
The present invention furthermore relates to a process for the preparation of the a~ueous polymer dispersions and their use for the preparation of finishes and coating materials.
Regarding the components of the copolymers (A) and (B), the following may be stated:
Suitable components (I) are copolymerizable olefinically unsaturated organic compounds of 3 to 10 carbon ,~,;
~ 3 - O.Z. 0050/39267 anhydr;de groups, such as acryl;c acid, methacrylic ac;d, male;c acid, ;tacon;c acid and the anhydrides and half-esters of the dicarboxyl;c acids. The anhydride groups of the copolymers can be converted, pr;or to neutral;zation w;th ammonia, into the corresponding half-ester groups, for e~ample by heating with glycol ethers or alcohols of 1 to 8 carbon atoms. Examples of such alcohols and glycol ethers are ethanol, ;sopropanol, butanol and butyl glycol. Preferred components (I) are acrylic acid, methacrylic ac;d and itaconic acid. Com-ponent (I) ;s present in copolymer (A) as copolymeri~ed units ;n amounts of from 1.5 to 15, preferably from S to 12, % by we;ght.
Examples of suitable esters of acryl;c acid or methacrylic acid (II) ~ith straight-chain or branched monoalkanols of 1 to 20 carbon atoms are methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acryl-ate, isobutyl methacrylate, tert-butyl acrylate, 2-ethyl-hexyl acrylate, 2-ethylhexyl methacrylate, lauryl acryl-ate and m;xtures of these. n-3utyl acrylats and methyl methacrylate are preferred. Component tII) ;s present in copolymer (A) in an amount of from 3û to 98.5, preferably from 45 to 95, ~ by ~eight.
Vinylaromatics of 8 to 12 carbon atoms, such as styrene, methylstyrene~ vinyltoluenes, tert-butylstyrene and halostyrenes, are used as componen~ (III). Styrene is preferred. Component (III) can be present in copoly-mer (A) in an amount of up to 60~ by weight. ~here ;t is present, amounts ~f from 20 to 45~ by weight have ~roven useful.
Su;table copolymer;zable carbonyl-containing com-pounds (IV) are, for example, ~ monoolefinically un-saturated aldehydes and/or ketones, such as acrolein, methacrolein, vinyl alkyl ketones where alkyl is of 1 to 20 carbon atoms, formylstyrene (meth)acrylo~yalkanals and -alkanones, whose preparat;on is descr;bed ;n, for 2~
- 4 - ~ o.Z. 0050/39267 example, German Laid-Open Application DOS 2,722,097, N-oxoal~yl (meth)acrylamides, as described in, inter alia, U.S. Patent 4,226,007 and German Laid-Open Applications DOS 2,061,213 and DOS 2,207,209, for example N-3-oxo-butylacrylamide and -methacrylam;de, N-1,1-dimethyl-3-oxobutyl(meth)acrylamide, diacetone(meth)acrylamide and N-3-oxo-1,1-dibutyl-2-propylhexylacrylamide, and acetonyl and diacetone (meth)acrylate and acrylamidopivalaldehyde and mixtures of these comonomers. 3-Oxoalkyl (me~h~-acrylates and N-3-oxoalkyl(meth)acrylamides are prefer-red. Component (IV) can be present in copolymer (A) in an amount of up to 20% by weight. Where it ;s used, an amount of from 2 to 15~ by weight is preferred.
Components (V) are further copolymerizable ole-finically unsaturated compounds ~hich are not stated under (I) to (IV). These are, for example, mono(meth)-acrylates of alkanediols, such as hydroxyethyl and hydroxypropyl (meth)acrylate and butanediol mono(meth)-acrylate, (meth)acrylamide and/or (meth)acrylonitrile.
These monomers can, if required, be used for obtaining specific properties. Other components (V) which may be present are: vinyl ethers, v;nyl esters, diesters of maleic acid, itaconic acid, citraconic acid or mesaconic acid with monoalcohols of 1 to 20 carbon atoms which may or may not contain ether or thioether groups. Other suitable components (Y) are monoolefins of 3 to 20 carbon atoms, such as propene, butene, pentene, hexene or iso-butene, and diolefins, such as butadiene or isoprene.
It is kno~n that polar functional groups, such as those which may be present in component (V), for example hy-droxyl or ether groups, additionally stabilize polymer dispersions. However, the novel dispersions do not require such additional stabilization. Polar groups present in component (V) may, ho~ever, have an adverse effect on the water resistance of the films obtained from the novel dispersions. In the preferred embodiment of the invention, component (V) is therefore not present.
02!92 - 5 - O.Z. OOS~/39267 Copol~mer (~) does not contain component (I).
Component (II) is present in copolymer ~) in an amount of from 40 to 100, preferably from 45 to 98, ~ by weight, while the remaining components (III) to (V) are present S in an amount of from 0 to 60% by weight, preferably from 2 to 55~ by weight where they are used.
The m;xture of the copolymers consists of from 15 to 50, preferably from 25 to 50, ~ by weight of copolymer (A) and from 50 to 85, preferably from S0 to 75, ~ by weight of copolymer (8). In order that the polymer dis-persions give non-tacky coatings after film formation, up to 65% by weight, based on the total amount of the com-ponents (I) to (V) used for the preparation of the co-polymers (A) and (8), of alkyl (meth)acrylates (II) whose homopolymers have glass transition temperatures of less than 0C are used. The glass transition temperatures of homopolymers are stated in, for example, J. ~randrup and E.H. Immergut, Polymer Handbook, Wiley-Interscience, 2nd Edition, 1975, III-139 et seq.
Furthermore, either copolymer (A) or copolymer (~) or both copolymers contains or contain compcnent (IV) to permit crosslinking by the polyhydrazides.
Copolymers (A) and (B) of the novel dispersions are advantageously prepared by polymerization in organic 25 solution. The process of solution polymerizaticn is in principle familiar to the skilled worker so that there is no need to describe here the conditions which are suit-able for the particular components. The polymerizatisn is advantageously carried out in ~he presence of from 0.3 to 5, preferably from 0.5 to 3, ~ by ~eight, based on the sum of the monomers, of free radical initiators, such as azobiscarboxamides, azobiscarbonitriles or pero~ides, in general at from Sû to 150C, preferably from 80 to 130C, in the presence or absence of regulators, such as mer-35 captoethanol, tert-dodecyl mercaPtan or diisopropylxan-thogen disulfide, ~hich may be present in amounts of from 0 to 3~ by weight, based on the sum of the monomers.
~00292 - 6 - O.Z. 0050/39267 Suitable organic solvents are in principle all conventional solvents ~hich dissolve the copolymer according to the invention. The presence of a solvent is not essential for stabilization and for achieving advantageous proper-ties of the novel dispersions, and, for environmentalprotection reasons, it is therefore appropriate to choose a very low solvent content. Advantageously used solvents are those which, because of their boiling po;nt and/or azeotrope formation with water, can readily be distilled off from the novel dispersions. Butanol, isobutanol, propanol, ethanol and toluene are particularly preferred.
It is not important per se whether component (A) is polymerized first, followed by component (B), or whether the converse procedure is adopted. In a prefer-red embodiment of the invention, however, component (A)is first polymerized and then component (8)~ ~oth com-ponents give a homogeneous mixture. The component pre-pared first is substantially, ie. more than 95~, prefer-ably 99~, polymerized before polymerization of the second Z0 component is begun. Residual monomers from the first component, in particular monomers containing acidic groups, could cause a change in the composition of the second component, leading to a deterioration in the per-formance characteristics. Dispersions prepared similarly according to the invention frsm t~o copolymers (A) and (B) ~hich are prepared separately and then mixed gener-ally have less advantageous performance characteristics, for example poorer s~ability and less favorable flow behavior. Furthermore, mixing would entail an additional operation~
The solutions of the polymerized copolymers (A) and (8) are converted into dispersions by admixing am-monia and diluting with water, or the polymerized copoly-mer solution is slowly stirred into an aqueous ammonia solution and a dispersion obtained in this manner. The organic solvent is removed by distillation from the dis-persions thus obtained, the resulting concentr2tion being - 7 - O.Z. 0050/39267 <5~ by weight; the solvent can be recovered. The degree of neutralization of the novel dispersions is from 10 to 150g, preferably from 15 to 100~, particularly preferably from 40 to 70%. The pH of the dispersions can then be from about 6.a to 10, preferably from 7.0 to 9. In order to achieve certain effects, a small proportion, advan-tageously not more than 25, preferably not more than 10, mol ~ of the ammonia required for neutralization can be replaced by organic amines, in particular triethylamine.
Such additives may adversely affect the water resistance of the dispersion films. The degree of polymerization of the novel dispersion is expediently chosen so that the resulting viscosity is advantageous for the processor.
The polymer content is therefore from 35 to 6~, prefer-ably from 40 to 55, ~ by ~eight.
Examples of suitable polyhydrazides ~C) are di-hydrazides of organic di- or oligocarboxylic acids. Ex-amples are malonic, succinic, glutaric, adipic, pivalic, suberic, azelaic, sebacic, decanedioic, dodecanedioic, tridecanedioic, tetradecanedioic, pentadecanedioic, hexa-decanedioic and 2-methyltetradecanedioic dihydrazide, methyl-, ethyl-, propyl-, butyl-, hexyl-, heptyl-, octyl-, 2-ethylhexyl-, nonyl-, decyl-, undecyl- and dodecyl-malonic dihydrazide, methyl-, ethyl-, propyl-, butyl-, hexyl-, heptyl- and octylsuccinic dihydrazide, 2-ethyl-3-propylsuccinic and -glu~aric dihydrazide, cyclohexanedi-carboxylic and cyclohexylmethylmalonic dihydrazide, tere-phthalic, phenylsuccinic~ cinnamylmalonic and benzyl-malonic dihydrazide, pentane-1,3,5-tricarboxylic tri-hydrazide, hex-4-ene-1,2,6-tricarboxylic trihydrazide, 3-cyanopentane-1,3,5-tricarboxylic trihydrazide, dicyano-fumaric dihydrazide and the di- and oligohydrazides of dimerized or oligomeri2ed unsaturated fatty acids.
Adipic dihydrazide is preferred.
The polyhydrazide is added to and stirred into the novel polymer dispersions advan~ageously after the excess organic solvent has been distilled off, in solid form or ~L3~0292 ..~ .
- 8 - o.Z. 0050/39267 as an aqueous solut;on or suspension.
Despite the possible reaction between hydrazide and carbonyl groups, ~hich leads to crosslinking, the novel dispersions surprisingly have a long shelf life, ie. they do not tend to form two phases even on prolonged storage, nor is there a significant change in the vis-cosity and film-forming behavior during storage.
However, after application to a substrate and drying, crosslinked films which are no longer completely soluble in solvents are obtained at as low as room tem-perature~ Drying and crosslinking are accelerated by elevated temperatures. The water resistance of the dis-persion filns decreases slightly with increasing hydraz-ide content, based on the carbonyl component, but is sub-stantially h;gher than that of a normal soap dispersion or - protective colloid dispersion even when the ratio of the number of equivalents is 1, based on the carbonyl com-ponent. The dispers;ons can be processed using a conven-tional coating unit, and the viscos;ty can be adapted to the particular coating system by thickening ~ith commer-cial thickeners or dilution ~;th water.
They are suitable as protect;ve and/or decorat;ve coatings on hard and soft substrates, for example metal, leather, paper and/or plastics.
a) Preparation of copoly~er (A) 440 9 of ethanol and one third of a mixture of ~80 g o~ styrene, 1,100 9 of n-butyl acrylate, 220 9 of acrylic acid, 66 9 of tert-butyl peroctoate and 330 9 of ethanol ~ere ;nitially taken in a reaction vessel and heated to the reflux temperature, and the remainder of the mixture ~as added uniformly in the course of 2.5 hours at th;s temperature. Polymerization was then car-ried out for a further 4 hours at the reflux temperature.
b) Preparation of the ~ixture of copolymers ~A) and (~) 50 9 of ethanol and 486 9 of the solution des-cribed under a) were initially taken and hea~ed to the ~3~iD292 - 9 - O.Z. 0050/39267 reflux temperature. Thereafter, a mixture of 189 g of styrene, 275 9 of n-butyl acrylate, 72 9 of diacetone-acrylamide, 9.7 9 of tert-butyl peroctoate and 49 9 of ethanol ~as added uniformly in the course of 3 hours.
Polymerization was then carried out for a further S hours at the reflux temperature, 2.2 9 of tert-butyl peroctoate being added twice after intervals of 1 hour. The result-ing polymer solution had a K value (according to DIN
53,726) of 31 and an acid number (according to DIN 53,402) of 30.4 mg of KOH/g of solid substance.
c) Preparation of the dispersions 32.8 9 of 25~ strength by weight aqueous ammonia solution were added to the mixture of copolymers (A) and (B) which was described under b). 650 9 of water ~ere then added ~ith vigorous stirring. 370 9 of an ethanol/
~ater mixture were then distilled off under reduced pressure from the resulting d;spersion, 320 9 of water being added during the distillation. ~hen the distilla-tion ~as complete, 35.2 9 of adipic dihydrazide were added at room temperature and stirred in over 4 hours. The dis-persion had the follo~ing data:
Solids content: 47.3~ by ~eight pH: 8.4 Ethanol content: 1.3% by weight Viscosity (rotational viscometer), 23C): 250 mPa.s.
A sa~ple of the dispersiom was applied to a glass plate and dried for 60 hours at room temperature. A
54 ~m thick transparent film having a pendulum hardness (according to DI~ 53,157) of 180 s was obtained; the film could not be completely dissolved again with acetone.
a) Preparation of copolymer (A) 231 g of isobutanol and half of a mixture of 165 9 of ~ethyl me~hacrylate, 120 9 of n-butyl acrylate, 28 9 of acrylic acid, 23 9 of diacetoneacryla~ide, 1.2 g of tert-butyl peroctoate, 1.2 9 of tert-butyl perbenzoate o~2~32 - 10 - O.Z. 0050/39267 and 25 9 of isobutanol were initially taken in a reac-tion vessel and heated to the reflux temperature and the remainder of the mixture was added uniformly in the course of 1 hour at the reflux temperature. Polymeriza-tion was then carried out for a further 2 hours at thereflux temperature.
b) Preparation of a mixture of copolymers (A) and (B) A mixture of 231 9 of rnethyl methacrylate 200 9 of n-butyl acrylate 33 9 of diacetoneacrylamide 5.6 9 of tert-butyl peroctoate and 8; 9 of isobutanol was added uniformly to the solution described under a) in the course of 2 hours at the reflux temperature. Polymeriza-tion was then carried out for a further 3 hours at the reflux temperature.
c) Preparation of the dispersion 25 9 of 25% strength by weight aqueous ammonia solution were added to the mixture of copolymers (A) and - (B) ~hich was described under b). 1 300 g of water were then added ~ith vigorous stirring. An isobutanol/water mixture was then distilled off under reduced pressure from the dispersion thus formed until the content of non-volatile components ~as 40% by weight. ~hen the distil-lation was complete 25.9 9 of adipic dihydrazide were added at room temperature and stirred in over 2 hours.
The dispersion had the following characteristic data:
Solids content: 40.3~ by weight pH: 7.~
Isobutanol content: 1.3% by weight Viscosity (rotational viscometer 23C): 350 mPa.s.
A sampl2 of the dispersion was applied to a glass plate by means of a knife coater and was dried for 60 hours at room temperature. A 60 ~m thick transparent film having a pendulum hardness (according to DlN 53 157) of 128 s was obtained; the film could not be completely dissolved again with acetone.
~0;292 -- 11 - o.Z. 0050/39267 a) Preparation of the copolymer ~A) 440 9 of ethanol and 944 9 of a mixture of 836 g of styrene, 264 9 of acrylic acid, 1,100 9 of n-butyl 5 acrylate, 66 9 of tert-butyl peroctoate and 330 9 of ethanol were initially taken in a reaction vessel and heated to the reflux temperature, and the remainder of the mixture was added uniformly in the course of 2.5 hours. Polymerization was then carried out for a further 4 hours at the reflux temperature.
b) Preparation of the mixture of copolymers (A) and (~) 714 9 of the solution described under a) were heated to the rsflux temperature. A mixture of 200 9 of styrene, 240 9 of n-butyl acrylate, 60 9 of diacetone-15 acrylamide, 200 9 of ethanol and 10 9 of tert-butyl per-octoate was added drop~ise in the course of 3 hours.
Polymer;zation was then carried out for a further 3 hours at the reflux temperature.
c) Preparation of the dispersion 56.6 9 of 25X strength by weight aqueous ammonia solution were added to the mixture of copolymers (A) and (B) ~hich was described under b). 980 9 of water were then added with v;gorous stirring. A dispersion was formed, fro~ which 540 9 of an ethanol/water mixture were distilled off under reduced pressure. When the distil-lation ~as complete, 15.4 9 of adipic dihydrazide were st;rred in, and the content of nonvola~ile components ~as brought to 41.3% by weight ~ith water. Further data of the dispersion:
pH: 8.4 Ethanol content: 0.8% by ~eight Viscosity (rotational visco~eter, 23C): 360 mPa.s.
A sample of the dispersion ~as applied to a glass plate by means of a knife coater and ~as dried for 60 hours at roon temperature. The resulting film had a pendulum hardness (according to DIN 53,157) of 76 s and could not be completely dissolved ~ith acetone.