AU644535B2

AU644535B2 - Aqueous polymer dispersions

Info

Publication number: AU644535B2
Application number: AU20531/92A
Authority: AU
Inventors: Rolf Dersch; Heinrich Grubert; Rainer Hummerich; Josef Neutzner
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1991-07-26
Filing date: 1992-07-23
Publication date: 1993-12-09
Anticipated expiration: 2012-07-23
Also published as: ES2077304T3; CA2074034A1; AU5757494A; DE59203809D1; AU656290B2; AU2053192A; JPH05202107A; DE4124817A1; EP0524497A1; EP0524497B1

Description

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P/00/ 01 1 281519, Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE

SPECIFICATION

STANDARD

PATENT

Application Number: Lodged: invention Title: AQUEOUS POLYMER

DISPERSIONS

The following statement IS a fuli description of this Invention, Including the best method of performing it known to

:-US

BASF.KTIENGESELLSCHAFT 0050ooo/42570 Aqueous Polymer Dispersions The present invention relates to aqueous polymer dispersions obtainable by polymerizing, in aqueous medium by the free radical emulsion polymerization method, a mixture of monomers which contains from 10 to 100 w/w of halogencontaining monomers, adjusting the pH of the aqueous phase of the resulting s aqueous polymer dispersion to a value of from 5 to 10 by the addition of ammonia and of primary and secondary amines of different basic agents and adding, based on the mixture of monomers, from 0.005 to 1 and preferably from 0.05 to w/w of at least one active ingredient selected from the group consisting of benzaldehyde, derivatives of benzaldehyde having one or two c01-4 alkyl radicals on the aromatic nucleus, benzyl alcohol, camphor, esters derived from formic acid and c3-eC alkanols, C 1 o-C 22 -unsaturated fatty acids, tetraalkyl orthosilicates containing alkyl radicals of from 1 to 4 carbon atoms, bis(4-hydroxyphenyl)-sulfone, citric acid and the salts thereof as well as salts of guanidine with organic or inorganic acids, both the addition of the basic agents and that of at least one active ingredient being possible prior to, during, and/or subsequently to the emulsion polymerization.

Aqueous polymer dispersions of which the polymeric portion contains polymerized units of halogen-containing monomers are variously suitable for use as binding 2o agents, particularly when importance is attached to increased fire security, since films produced therefrom have reduced flammability.

It is known that the aqueous phase of aqueous polymer dispersions produced without the use of basic auxiliaries usually has a pH below 5, which has a negative effect in numerous applications. For this reason, the pH is generally raised by the addition of basic agents.

DE-A 2 246 499 discloses that originally white dispersions containing polymerized units of vinyl chloride and/or vinylidene chloride in the polymeric phase show a brown discoloration on the addition of basic substances, and that this discoloration can be substantially reduced by the addition of small quantities of at least one epoxide compound. A disadvantage arising from the addition of epoxides is, however, that epoxides have, as side-effect, a cross-lining action on the polymeric portion of the aqueous dispersion.

The prior German Patent Application P 40 24 154.8 relates to essentially non-

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14 I. 1 T A I BASFAKTIENGESELLSCHAFT o.z.ooso/42570 yellowing aqueous polymer dispersions obtainable by polymerizing, in aqueous medium by the free radical emulsion polymerization method, a mixture of monomers which contains from 10 to 100 w/w of halogen-containing monomers, in the presence of from 0.5 to 6 based on the mixture of monomers, of s exclusively anionic and/or 'on-ionic interfacially active substances, and adjusting the pH of the aqueous phase of the resulting aqueous polymer dispersion to a value of from 5 to 10 by the addition of ammonia and primary and secondary amines of different basic agents. A disadvantage of these dispersions and films produced therefrom is that their discoloration characteristics with reference to time are not o entirely satisfactory.

The prior German Patent Application P 40 24 150.5 relates to non-yellowing aqueous polymer dispersions obtainable by polymerizing, in aqueous medium by the free radical emulsion polymerization method, a mixture of monomers which is contains from 10 to 100 %w/w of halogen-containing monomers, adjusting the pH of the aqueous phase of the resulting aqueous polymer dispersion to a value of from 5 to 10 by the addition of ammonia and primary and secondary amines of different basic agents and adding, based on the mixture of monomers, from 0.005 to 1 w/w of at least one active ingredient selected from the group consisting of glycerol, pivalic acid, paraldehyde, 2,6-di-tert-butyl-p-cresol, benzophenone, alkylsubstituted benzophenones, thiosulfuric acid and salts thereof as well as oxalic acid and salts thereof, thiosulfuric acid and salts thereof being highly recommended for use as active ingredients.

It is thus an object of the present invention to provide an aqueous polymer dispersion containing polymerized units of halogen-containing monomers in the polymeric phase, whose pH is adjusted to a value of from 5 to 10 by the addition of basic agents and which, as also film formed therefrom, shows a very satisfactory low level of discoloration even after prolonged storage, as a result of the addition of an active ingredient other than epoxides and other than the active ingredients cited in the prior German application P 40 24 150.5 Accordingly, we have found the aqueous polymer dispersion defined above. The efficacy of the aforementioned active substanceisis at least equivalent to that of thiosulfuric acid and salts thereof. It is particularly advantageous to use, as active ingredient, benzaldehyde, camphor, benzyl alcohol, the ester derived from formic acid and n-butanol ic, oleic acid, tetraethyl orthosilicate and bis(4-hydroxyphenyl)sulfone, and especially citric acid and salts thereof, eg the alkali metal salts, as well as the salts of guanidine with inorganic mineral acids. Especially the last two classes of compounds are more effective than thiosulfuric acid and its derivatives, whilst within these classes pure citric acid and the salts of guanidine with 7 -Aj BASFAKTIENGESELLSCHAFT O.Z.0050/42570 hydrochloric acid, sulfuric acid, phosphoric acid, carbonic acid and water are of particular significance, particularly the salt of guanidine with hydrochloric acid.

Preferred halogen-containing monomers are vinyl bromide, vinyl chloride and s vinylidene chloride, of which vinyl chloride and vinylidene chloride are particularly preferred. Suitable comonomers are, for example, esters of acrylic or methacrylic acid with aliphatic alcohols containing from 1 to 10 carbon atoms, the methyl, ethyl, isopropyl, n-butyl, isobuty-, tert-butyl, n-hexyl, and 2-ethylhexyl esters being preferred. Other suitable comonomers are a,3-monoethylenically unsaturated o1 carboxylic acids such as acrylic and methacrylic acids, vinyl esters of lower alkanecarboxylic acids such as vinyl acetate and vinyl propionate, nitriles of lower ,-monoethylenically unsaturated carboxylic acids such as acrylonitrile and methacrylonitrile as well as the amides of these carboxylic acids, acrylates and methacrylates with lower polyhydric alcohols, and unsaturated sulfonic and is phosphonic acids, further examples being lower mono-unsaturated or polyunsaturated hydrocarbons such as ethylene, propene and butadiene. Preferably, the monomer mixture to be polymerized contains, based on the total amount of monomers, from 20 to 90 w/w of halogen-containing monomers.

Suitable polymerization initiators are primarily inorganic peroxides such as sodium, potassium, and ammonium peroxydisulfates, and hydrogen peroxide. Other suitable compounds comprise azo compounds such as 2,2'-azobisisobutyronitrile as well as organic peroxides such as dibenzoyl peroxide, tert-butyl perpivalate or hydroperoxides such as tert-butyl hydroperoxide and, if desired, combined systems composed of at least one organic reducing agent and at least one peroxide and/or hydroperoxide, eg tert-butyl hydroperoxide and the Na salt of hydroxymethanesulfinic acid, as well as combined systems which additionally contain a small amount of a metal compound which is soluble in the polymerisation medium and whose metallic component can occur in more than one valence stage, eg ascorbic acid/iron(II) sulfate/sodium peroxydisulfate, whilst instead of ascorbic acid the Na salt of hydroxymethanesulfinic acid, sodium sulfite, sodium bisulfite or sodium metabisulfite are also frequently used.

The amount of polymerization initiators used in the emulsion polymerization is preferably kept at a low level and is usually from 0.05 to 1 based on the monomers. The content thereof is preferably from 0.1 to 0.3 w/w. Amounts of up to 10 w/w are less preferred.

Emulsifiers used may be anionic, cationic, and non-ionic emulsifiers as well as compatible mixtures thereof. The content thereof, by weight, is usually from 0.05 to 10 %w/w based on the total weight of the monomers to be polymerized. It is ~U BASFAKTIENGESELLSCHAFT O.Z.0050/42570 particularly advantageous to use exclusively non-ionic and anionic emulsifiers and mixtures thereof.

Preferably used non-ionic emulsifiers are ethoxylated alkanols (degree of ethoxylation: from 2 to 100, alkyl radical: c8-c36), ethoxylated alcohols containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 2 to 100, chain length: c0-c36), ethoxylated mono-, di- oder tri-alkylphenols and mono-, di- oder tri-alkylnaphthols (degree of ethoxylation: from 2 to 100, alkyl radical: c4-c36), ethoxylated aliphatic monocarboxylic acids (degree of ethoxylation: from 6 to o1 alkyl radical: c8-c24) and ethoxylated monocarboxylic acids containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 6 to 50, alkyl radical: c0-c24).

Anionic emulsifiers which may be used to advantage are the alkali metal and ammonium salts of the sulfated derivatives of alkanols containing from 6 to 18 carbon atoms, alcohols containing from 6 to 18 carbon atoms and from 1 to 4 olefinic double bonds, ethoxylated alkanols (degree of ethoxylation: from 4 to alkyl radical: C12-C18), ethoxylated alcohols containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 4 to 30, alkyl radical: c12-c01) and of ethoxylated alkyl phenols (degree of ethoxylation: from 4 to 30, alkyl radical: C8-C14), the alkali metal and ammonium salts of saturated and unsaturated carboxylic acids (chain length: c0-c24), the alkali metal and ammonium salts of alkylsulfonic acids containing from 12 to 18 carbon atoms as well as the corresponding salts of alkylarylsulfonic acids (alkyl radical: co-c18) and of esters of sulfosuccinic acid with alcohols containing from 4 to 18 carbon atoms.

Protective colloids may also be used along with emulsifiers as interfacially active substances for the emulsion polymerization. Examples of suitable protective colloids are high molecular weight compounds such as poly(vinyl alcohol)s, poly(vinyl pyrrolidone)s, cellulose derivatives, polyacrylamides, polymethacrylamides, poly(carboxylic acid)s or the alkali metal or ammonium salts thereof.

Furthermore, chain-stoppage modifiers may be used in the emulsion polymerization process.

It is preferred to use initiators and surface-active substances such as do not contain any ammonium ions.

The emulsion polymerization temperature is usually from 300 to 90 OC. However, dispersions of the invention which are particularly free from discoloration are obtained when the emulsion polymerization temperature is from 300 to 70 The polymerization medium may consist either of water only or of a mixture of water and one or more liquids miscible therewith, such as methanol. We prefer to use

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C~ U- BASFAKTIENGESELLSCHAFT O.Z.0050/42570 water only. The emulsion polymerization can be carried out as a batch process or in the form of a continuous-feed process using both cascade and gradient methods. We prefer to use a continuous-feed process, in which there is initially placed in the reaction vessel a portion of the polymerization ingredients, which are heated to the polymerization temperature, after which the remainder is fed in continuously, in stages, or by a method employing an overall concentration gradient, via separate feeds, one or more of which contains the monomers as pure substance or in the form of an emulsion. The solids content of the resulting aqueous polymer dispersion is generally from 5 to 60 w/w.

Primarily suitable basic agents for raising the pH are metal salts of weak acids, eg acetates, formates, or carbonates of alkali metals, tertiary amines such as triethylamine, and especially hydroxides and oxides of alkali metals and alkalineearth metals such as KOH, NaOH and Ca8OH9 2 of which Ca80H9 2 is particularly is preferred Surprisingly, both the aqueous polymer dispersions of the invention and films produced theref.om show even after prolonged storage substantially no discoloration.

Examples a) Manufacture of starting dispersions D 1 to D 8 D 1: a mixture of 25 kg of water, 0.02 kg of emulsifier I, 0.03 kg of sodium peroxydisulfate 8Na2S0, 8 9 and 0.0005kg of iron(II)sulfate heptahydrate 8FeSO 4 -7H 2 09 was heated to the polymerization temperature, ie °C and intermixed with 5 of a feed 1 as well as 5 of a feed 2 and kept at 50 °C for 15 minutes. The remaining amount of feed 1 as well as the remaining amount of feed 2 and a feed 3 were then added continuously and concurrently over a period of 3.5 hours while keeping the mixture at the polymerization temperature. A feed 4 was then added continuously over a period of 30 minutes at 50 OC and likewise a feed 5 over a period of 1 hour. Polymerization was then continued at room temperature with the addition of a mixture of 0.12 kg of a 70 %w/w strength aqueous-alcoholic solution of tertbutyl hydroperoxide and 0.05 kg of emulsifier I in 0.35 kg of water followed by the addition of 0.17 kg of the Na salt of hydroxymethanesulfinic acid in 0.35 kg of water.

BASFAKTIENGESELLSCHAFT o.z. ooo0050/42570 Feed 1: 55 kg of vinyl chloride kg of vinyl propionate kg of n-butyl acrylate 1.7 kg of emulsifier IT 0.78 kg of emulsifier I and 41 kg of water Feed 2: Feed 3: Feed 4: Feed 5: 0.003 kg of the Na salt of hydroxymethanesulfinic acid 0.125 kg of sodium acetate and 14 kg of water 0.162 kg of sodium peroxydisulfate and 12 kg of water 0.048 kg of sodium peroxydisulfate and 4 kg of water 0.0018 kg of the Na salt of hydroxymethanesulfinic acid 0.0273 kg of sodium acetate and 4 kg of water Emulsifier I: Na salt of the sulfated derivative of ethoxylated isooctyl phenol (degree of ethoxylation: Emulsifier II: ethoxylated isooctyl phenol (degree of ethoxylation: D 2 to D 4: D 5 to D 8: as D 1, except that the emulsion polymerization was carried out in the sequence of operations stated above but at 600, 700 and 80 °C respectively, instead of 50 OC.

as D 1 to D 4 in the sequence of operations stated above but with the amount of sodium peroxydisulfate used increased by 50% in each case.

3s b) addition of basic agents as well as of active ingredients to the dispersions D 1 to D 8 and assessment of discoloration The pH of the aqueous phase of the dispersions D 1 to D 8 was raised, in each case, to a value of 8 by the addition of ammonia, KOH, NaOH and Ca(OH) 2 after which BASFAKTIENGESELLSCHAFT O.Z.o000/42570 there were added in each case, based on the solids content of the aqueous dispersion, 0.1 %w/w of the following active substances, followed by visual assessment of the discoloration after a few days: Benzaldehyde, camphor, benzyl alcohol, esters derived from formic acid and nbutanol, oleic acid, tetraethyl orthosilicate, bis(4-hydroxyphenyl)-sulfone, citric acid, salt of guanidine with hydrogen chloride (hydrochloric acid).

The use of ammonia gave distinct yellowing, whereas the use of KOH and NaOH o produced only a minimum yellow cast and the use of Ca(OH) 2 gave no discoloration.

The best degree of whiteness was exhibited by the dispersion which contained Ca(OH) 2 and citric acid or Ca(OH) 2 and the salt of guanidine with hydrogen chloride.

The resulting fresh dispersions were subsequently processed to form film material, stored in a desiccator cabinet at 50 OC for 14 days and again checked visually for is discoloration. The results were the same as those obtained for the liquid condition.

In all instances, the discolorations resulting fiom the use of the active ingredients of the invention were less pronounced than in the absence thereof, the action of citric acid and the salt of guanidine with hydrogen chloride being superior to that of sodium thiosulfate (comparative test), and the action of the other active substances was substantially equivalent to that of sodium thiosulfate.

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Claims

1. Aqueous polymer dispersion, obtained by polymerizing, in aqueous met um by the free radical emulsion polymerization method, a mixture of monomers which contains from 10 to 100% w/w of nalogen-containing monomers, adjusting the pH of the aqueous phase of the resulting aqueous polymer dispersion to a value of from 5 to 10 by the addition of ammonia and primary and secondary amines of different basic agents and adding, based on the mixture of monomers, from 0.005 to 1% w/w of at least one active ingredient selected from the group consisting of benzaldehyde, derivatives of benzaldehyde having one or tvo C1-C4 alkyl radicals on the aromatic nucleus, benzyl alcohol, camphor, esters derived from formic acid and C3-C6 alkanols, Clo-C 22 -unsaturated fatty acicb, tetraalkyl orthosilicates containing alkyl radicals of from 1 to 4 carbon atoms, bis(4-hydroxyphenyl)-sulfone, citric acid and the salts thereof as well as salts of guanidine with organic or inorganic acids, both the addition of the basic agents and that of at least one active ingredient being possible prior to, during, and/or subsequently to the emulsion polymerization.

2. Aqueous polymer dispersion as claimed in claim 1, containing, as active ingredient, at least one selected from the group consisting of citric acid and salts thereof and salts of guanidine with organic or inorganic acids.

3. Aqueous polymer dispersion as claimed in claim 1 or claim 2, containing, as active ingredient, citric acid, the salt of guanidine with hydrogen chloride or a mixture of these active components. DATED this 30th day of September, 1993 BASF AKTIENGESELLSCHAFT WATERMARK PATtNT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA a BASFAKTIENGESELLSCHAFT o.z.o0050/42570 Aqueous polymer dispersions Abstract of the disclosure: Aqueous polymer dispersions, obtainable by polymerizing, in aqueous medium by the free radical emulsion polymerization method, a mixture of monomers which contains from 10 to 100 w/w of halogen-containing monomers, adjusting the pH of the aqueous phase of the resulting aqueous polymer dispersion to a value of s from 5 to 10 by the addition of ammonia and primary and secondary amines of different basic agents and adding, based on the mixture of monomers, from 0.005 to 1 w/w of at least one active ingredient selected from the group consisting of benzaldehyde, derivatives of benzaldehyde having one or two c--c4 alkyl radicals on the aromatic nucleus, benzyl alcohol, camphor, esters derived from formic acid o and c3-C6 alkanols, C01-C 22 -unsaturated fatty acids, tetraalkyl orthosilicates contain- ing alkyl radicals of from 1 to 4 carbon atoms, bis(4-hydroxyphenyl)-sulfone, citric acid and the salts thereof as well as salts of guanidine with organic or inorganic acids, both the addition of the basic agents and tnat of at least one active ;ngredient being possible prior to, during, and/or subsequently to the emulsior polymerization. 9