CA2074033A1

CA2074033A1 - Aqueous polymer dispersions

Info

Publication number: CA2074033A1
Application number: CA002074033A
Authority: CA
Inventors: Heinrich Grubert; Rolf Dersch; Josef Neutzner; Rainer Hummerich; Peter J.M.W. Claassen
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1991-07-26
Filing date: 1992-07-16
Publication date: 1993-01-27
Also published as: JPH05202255A; DE4124819A1; EP0524513A3; AU645212B2; AU2053292A; ES2068652T3; DE59201397D1; EP0524513B1; EP0524513A2

Abstract

BASF AKTIENGESELLSCHAFT O.Z.0050/42571 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, 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 guanidine prior to, during, and/or subsequently to the emulsion polymerization.

Description

BAsF~ut`r~ sE~sc~l~n o.z.oosol42571 _ 2074~33 Aqueous Polymer Dispersions The present invention relates to aqueous polymer dispersions obtainabie by polymerizing, in aqueous medium by the free radical emulsion polymerization method, a mixture of monomers which contains from 10 to 100 ~OW~ of halogen-containing monomers, and adjusting the pH of the aqueous phase of the resulting 5 aqueous polymer dispersion to a value of from 5 to 10 by the addition of guanidine 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 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 15 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 a2~ 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 oneepoxide compound. A disadvantage arising from the addition of epoxides is, however, that these have, as side-effect, a cross-linking action on the polymeric portion of the aqueous dispersion.

The prior German PatentApplicatfon P 4~ 24 154.8 relates to essentially non-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 æw~ of halogen-containing monomers, 30 in the presence of from 0.5 to 6%w~h, based on the mixture of monomers, of exclusively anionic and/or non-ionic surface-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 35 therefrorn is that their discoloration characteristics with reference to time are not entirely sa~isfactory.

BASF~ 5~5~5Ct1A~T O Z oo50142571 __ 207~033 The prior German Patent App/ication 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 contains from 10 to 100 ~0 w,~ of halogen-containing monomers, adjus~ing the pH
5 of the aqueous phase of the resulting aqueous polymer dispersion to a value offrom 5 to 10 by the addition of ammonia and primary and secondary amines of dif.~erent basic agents and adding, based on the mixture of monomers, from 0.005to 1 ~0w~v of at least one active ingredient selected from the group consisting of glycerol, pivalic acid, paraldehyde, 2,6-di-tert-butyl-p-cresol, benzophenone, alkyl-substituted benzophenones, thiosulfuric acid and salts thereof as well as oxalicacid and salts thereof, thiosulfuric acid and salts thereof being highly recommend-ed for use as active ingredients.

It is thus an object of the present invention to provide an aqueous polymer t5 dispersion containing polymerized units of halogen-containing monomers in thepolymeric phase, whose pH is adjusted to a value of from 5 to 10 by the addition of a basic agent and which, as also film formed therefrom, shows a very satisfactory low level of discoloration even after prolonged storage, without further additives.

20 Accordingly, we have found the aqueous polymer dispersion defined above. We have also found that the tendency of aqueous polymer dispersions of the invention to discoloration can be further reduced by adding from 0.005 to 1 %w,~ and preferably from 0.05 to 0.5 %w~, based on the monomer mixture, of at least one active substance selected from the group consisting of glycerol, pivalic acid, 25 paraldehyde, 2,6-di-tert-butyl-p-cresol, benzophenone, alkyl-substituted benzo-phenones, thiosulfuric acid and salts thereof, oxalic acid and salts thereof, benzaldehyde, derivatives of benzaldehyde having one or two C1-C4 alkyl radicalson the aromatic nucleus, benzyl alcohol, camphor, esters derived ~rom formic acid and c3-C6 alkanols, C~0-C22-unsaturated fatty acids, tetraalkyl orthosilicates 3t) 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, the addition of said active substance(s) being effected prior to, during, and/or subsequently to the emulsion polyrnerization. Particularly good whites are exhibited by dispersions to which sodium thiosulfate, benzaldehyde, 35 camphor, benzyl alcohol, the ester derived from formic acid and n-butanol, oleic acid, tetraethyl orthosilicata, bis(4-hydroxyphenyl)-sulfone, citric acid or a mixture of these active ingredients has been added. It is particularly advanta~eous to add citric acid as one of said active substances.

Preferred halogen-containing monomers are vinyl bromide, vinyl chloride and 2~74033 BASFA~T~E~ GESE-~SC~ O ~ ooso/42571 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 1n carbon atoms, the rnethyl, ethyl, isopropyl, n-butyl, isobutyl, ter~-butyl, n-hexyl, and 2-ethylhexyl esters being 5 preferred. Other suitable comonomers are "~-monoethylenically unsaturated carboxylic acids such as acrylic and methacrylic acids, vinyl esters of lower alkanecarboxylic acids such as vinyl acetate and vinyl propionate, nitriles of lower a,~-monoethylenically unsaturated carboxylic acids such as acrylonitrile and methacrylonitrile as well as the amides of these carboxylic acids, acrylates and,0 methacrylates with lower polyhydric alcohols, and unsaturated sulfonic and phosphonic acids, further examples being lower mono-unsaturated or polyunsatur-ated hydrocarbons such as ethylene, propene, and butadiene. Preferably, the monomer mixture to be polymerized contains, based on the total weight of monomers, from 20 to 90 ~Ow/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 20 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/orhydroperoxide, eg, tert-butyl hydroperoxide and the Na salt of hydroxymethane-sulfinic acid, as well as combined systems which additionally contain a small amount of a metal compound which is soluble in the polymerisation medium and 25 whose metallic component can occur in more than one valence stage, eg, ascorbic acid/iron(l/) 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.

30 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 æwhv, based on the monomers. The content thereof is preferably from 0.1 to 0.3 % w~. Amounts of up to 10 %w~ are less preferred.

35 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 particularly advantageous to use exclusively non-ionic and anionic emulsifiers and mixtures thereof.

Preferably used non-ionic emulsifiers are ethoxylated alkanols (degree of 207~033 T'E' ~i~SE~S~ 0 Z oosc~42571 _ . _ _ _ . .. _ _ _ ... . . _ . . _ _ . . _ .. . . _ . _ . . .. _ . . _ ~
ethoxylation: from 2 to 100, alkyl radical: Cg-C36)~ ethoxylated alcohols containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 2 to 10~, chain length: c8-c36). ethoxylated mono-, di- oder tri-alkylphenols and mono-, di- oder tri-alkylnaphthols (degree of ethoxylation: from 2 to 100, alkyl radical: c4-c36), s ethoxylated aliphatic monocarboxylic acids (degree of ethoxylation: from 6 to 5~, alkyl radical: c8-c24) and ethoxylated monocarboxylic acids containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 6 to S0, alkyl radical: c8-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 30, alkyl radical: C12-C~8), ethoxylated alcohols containing from 1 to 4 olefinic double bonds (degree of ethoxylation: from 4 to 30, alkyl radical: c12-c18) and of 75 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: C8-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: C~o-C18) and of esters 20 of sulfosuccinic acid with alcohols containing from 4 to 18 carbon atoms.

Protective colloids may also be used along with emulsifiers as surface-active substances for the emulsion polymerization. Examples of suitable protective colloids are high molecular weight compounds such as poly(vinyl alcohol)s, 25 poly(vinyl pyrrolidone)s, cellulose derivatives, polyacrylamides, polymethacryl-amides, poly(carboxylic acid)s or the alkali metal or ammonium salts thereof.
Furthermore, chain-stoppage regulators may be used in the emulsion polymeriza-tion process.

30 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 30 to 90C. However, dispersions of the invention which are particularly free from discoloration are 35 obtained when the emulsion polymerization temperature is from 30 to 70 C. The polymerization medium may consist either of water only or of a mixture of water and one or more liquids miscible therewith, such as meth~nol. We prefer to use water only. The emulsion polymerization can be carried out as a batch process orin the form of a continuous-feed process using both cascade and gradient 40 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 BASFArllY~sE~sc~lAF7 o.2.ooso/42571 heated to the polymerization temperature, after which the remainder is fed in via separate feeds, one or more of which contains the monomers as pure substance or in the form of an emulsion, this being effected continuously, in stages or in such a manner that there is an overall concentration gradient. The solids content of the s resulting aqueous polymer dispersion is generally from 5 to 60 % w/w.

Surprisingly, bo~h the aqueous polymer dispersions of the invention and films produced therefrom show no discoloration even after prolonged storage.

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 1, 0.03 kg of sodiumperoxydisulfate (Na2S208) and 0.0005 kg Of iron(lI~ sulfate hepta-hydrate (FeS04 7H20) was heated to the polymerization temperature, ie, 50 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 ovsr a period of 30 minutes at 50C 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 0.12kg of a 70%w/w strength aqueous-alcoholic solution of tert-butyl hydroperoxide and O.OSkg of emulsifier I in 0.35kg of water followed by the addition of 0.17kg of the Na salt of hydroxymethane-sulfinic acid in 0.35kg of water.

30 Feed 1: 55 kg of vinyl chloride 10 kg of vinyl propionate 35 kg of n-butyl acrylate 1.7 kg of emulsifier II
0.78 kg of emulsifier I and 41 kg Of water Feed 2: 0.003 kg of the Na salt of hydroxymethanesulfinic acid 0.125 kg of sodium acetate and 14 kg of water s 2~7~033 BASF~TIE!~O~S~-~SC~FT O Z ooso~42571 Feed ~: 0.162 kg of sodium peroxydisulfate and 12 ~g of water Feed 4: 0.048 ~g of sodium peroxydisulfate and s 4 kgof water Feed 5: 0.0018kg of the Na salt of hydroxymethanesulfinic acid 0.0273kg of sodium acetate and 4 kg of water Emulsifier I: Na salt of the sulfated derivative of ethoxylated isooctyl phenol (degree of ethoxylation: 25) EmulsifierII: ethoxylated isooctyl phenol (degree of ethoxylation: 25) D 2 to D 4: as D 1, except that the emulsion polymerization was carried out in the sequence of operations stated above but at 60, 70 and 80C
respectively, instead of 50 C.
O D 5 to D 8: as D 1 to D 4 in the sequence of operations stated above except that the amount of sodium peroxydisulfate used was increased by 50 ~0 in each case.

b) Addition of guanidine and active ingredients to the dispersions D 1 to D 825 assessment of discoloration The pH of the aqueous phase of the dispersions D 1 to D ~ was raised, in each case, to a value of 8 by the addition of guanidine, after which some of the dispersions were left unchanged whilst to others there were added in each case, 30 based on the solids content thereof, 0.1 %w~ of the active substances stated below, and the dispersions were then allo~ed to stand for 10 days, after which the discoloration was assessed visually:

glycerol, pivalic acid, paraldehyde, 2,6-di-tert-butyl-p-cresol, benzophenone, 35 sodium oxalate, sodium thiosulfate, benzaldehyde, camphor, benzyl alcohol, esters derived from formic acid and n-butanol, oleic acid, tetraethyl orthosilicate, bis(4-hydroxyphenyl)-sulfone, and citric acid.

In no case was there any discoloration. The best degree of whiteness was 40 exhibited by the dispersion which contained citric acid as supplementary active BASFA~T~E~aESELLSC~FT o.Qooso/42s71 ingredient. The use of ammonia as basic agent in a comparative experiment produced distinct yellowing.

The dispersions were then made up anew and processed to form film material, stored in a desiccator cabinet at 50 C for 14 days and again checked visually for discoloration. The results were the same as those obtained for the liquid condition, ie, the degree of whiteness was improved somewhat by the addition of the active ingredients, the strongest effect being obtained with citric acid.

Claims

1. Aqueous polymer dispersion, 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, 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 guanidine prior to, during, and/or subsequently to the emulsion polymerization.
.

2. Aqueous polymer dispersion as claimed in claim 1, obtainable by the addition of from 0.005 to 1 %w/w, based on the weight of the monomer mixture, of at least one active substance selected from the group consisting of glycerol, pivalic acid, paraldehyde, 2,6-di-tert-butyl-p-cresol, benzophenone, alkyl-substituted benzophenones, thiosulfuric acid and salts thereof, oxalic acid and salts thereof, benzaldehyde, derivatives of benzaldehyde having one or two C1-C4 alkyl radicals on the aromatic nucleus, benzyl alcohol, camphor, esters derived frorn formic acid and C3-C6 alkanols, C10-C22-unsaturated fatty acids, tetraalkyl orthosilicates containing alkyl radicals of from 1 to 4 carbon atoms,bis(4-hydroxyphenyl)-sulfone, and citric acid, the addition of said active substance(s) being effected prior to, during, and/or subsequently to the emulsion polymerization.