CA2059425A1 - Process for the production of aqueous dispersions of chloroprene polymers - Google Patents

Abstract

A PROCESS FOR THE PRODUCTION OF AQUEOUS DISPERSIONS OF
CHLOROPRENE POLYMERS

A b s t r a c t Aqueous dispersions based on carboxyl-functional chloroprene polymers, which are eminently suitable as raw materials for adhesives, can be produced by a seed inflow process under defined conditions.

Le A 27 723 - Foreign Countries

Description

A PROCESS FOR THE__RODU TION OF AQUEOUS DISPER IONS OF

This invention relates to a process for the production of aqueous dispersions of carboxyl-functional chloroprenP
polymers which are suitable as raw materials for adhesives having excellent adhesion, more particularly to rubber and metals.
Contact adhesives are adhes ves which are applied to both parts to be joined and left to dry. By subsequently fitting the two parts together under pressure, a bond of high initial strength is established. By virtue of their o hi gh initial peel strength,chloroprene homopolymers and co-polymers are suitable raw materials for contact adhesives.
Although contact adhesives based on chloroprene polymers still predominantly contain organic solvents, there is a need for ecological and economic reasons for suitable aqueous dispersions. These dispersions should be acidic to mildly nPutral and should preferably have pH
values of 2 to 8 and, more preferably, 6 to 8. They should be shear-stable so that they do not lead to the precipita-tion of coagulum under shear stressing, as encountered, for example, during spraying.
~ queous dispersions o~ carboxyl-functional chloroprene polymers are known, for example, ~rom DE-PS 24 26 012 (=US
4,123,514) and DE-OS 25 ~0 545. These dispersions are prepared by polymerization of the monomers (in addition to chloroprene, at least one ~,B-ethylenically unsaturated carboxylic acid, such as methacrylic acid) in aqueous phase in the presence of protective colloids; polyvinyl alcohol and hydroxyalkyl cellulose are recommended as suitable protective colloids~ Typical anionic, cationic or nonionic emulsifiers are not used or only in very small quantities, if at all. The dispersions obtained in this way are said to be suitable as raw materials for adhesives.

Le A 27 723 - Foreign Countries By virtue of their pronounced hydrophilicity, protec-tive colloids present in the dispersion provide the dried polymer film with the property of absorbing undesirably large amounts of water in a humid environment. Since dried adhesive layers are expected to swell only slightly, if at all, even under unfavorable conditions, the chloroprene polymer dispersions according to DE-PS 24 26 012 and DE-OS
25 00 545 are only suitable to a limited extent as raw materials for adhesives.
In addition, the dispersions according to DE-PS 24 26 012 and DE-OS 25 00 545 also contain polymer particles larger than l ~m in diameter. These particles tend to sediment. Accordingly, an a~ditional step is necessary before processing in order to redisperse the sediment. In lS addition, applicants' own investigations have revealed another disadvantage of the dispersions prepared in accord-ance with DE-PS 24 26 012 and DE-OS 25 00 545. The chloro-prene polymers have only a very low percentage content of copol~merized units of ~,B-ethylenically unsaturated carboxylic acid. The high concentration of carboxyl groups in the aqueous phase indicates that a large proportion of the carboxylic acid has not participated in the polymeriza-tion reaction in the required manner.
Accordingly, the problem addressed by the present invention was to provide non-s~dimenting, acidic or neutral aqueous dispersions of copolymers based on chloroprene and ~,B-ethylenically unsaturated carboxylic acid in which the content of unsaturated carboxylic acid in the aq~leous phase would be as low as possible (i.e~ the unsaturated car-boxylic acid would be incorporated to a high degree in the copolymer). The dispersions would be suitable for use as raw materials for adhesive~ and would provide the adhesive layers with a long contact adhesion time, with high initial and ultimate strength and with low water absorption.
~he low degree of incorporation of the unsaturated Le A 27 723 2 21[?~

carboxylic acid in the polymers of DE-PS 24 26 012 and DE-OS 25 00 545 is primarily attributable to the copolymeriza-tion parameters of the chloroprene/unsaturated carboxylic acid (specifically: chloroprene/methacrylic acid) system;
cf. for example Brandrup/Immergut, "Polymer Handbook", 2nd Edition, II-156, J. Wiley, 1975. A higher degree of incor-poration can generally be obtained by a higher conversion although, in that case, the necessary reacti.on times and higher concentrations of initiator also promote higher gel contents of the polymers.
It has now surprisingly been found th~t the problem stated above can be solved by polymerization by the so-called "seed inflow process" in the absence of protective colloids (but optionally in the presence of typical ionic and/or nonionic emulsifiers) at temperatures of 5 to 35C
and preferably at temperatures of 10 to 35C, providing steps are taken to ensure that the inflow of monomer, as measured on the basis of polymer already present, does not exceed certain low values.
Accordingly, the present invention relates to a process for the production of aqueous dispersions of chloroprene polymer containing a) 90 to 99.6% by weight copolymerized chloroprene, of which up to 10% by weight may be replaced by other copolymerizable monomers and/or up to 2% by weiyht by sulfur, based in either case on a), and b) 0.4 to 10% by weight copolymerized ~,B-ethylenically unsaturated carboxylic acid corresponding to the following formula R
I

in which Le A 27 723 3 2~5~

R represents hydrogen, C14 alkyl or CH2COOH, by emulsion polymerization at 5 to 35C and preferably at 10 to 30C by the seed in~low method in the absence of protective colloids, in which 70 to 98% by weight and preferably 90 to 95% by weight monomer (a+b) ("inflow") is polymerized in the presence of 2 to 30% by weight and preferably 5 to 10% by weight polymer formed from the monomers a and optionally b ("seed"), the inflow being regulated in such a way that the ratîo by weight of polymer formed to free monomer in the reaction mixture at any stage of the subsequent polymerization process ~inflow process) is ~50:<50, preferably >70:.~30 and, more preferably, >80:<20, the percentages of components a) and b) on the one hand and of seed and inflow on the other hand adding up to 100.
"Other" copolymerizable monomers a) suitable for the process according to the invention do not include the carboxylic acids b), but instead mono- and di~ethylenically unsaturated compounds containing 3 to ~ carbon atoms, such as for example monoethylenically unsaturated aliphatic compounds, such as acrylonitxile, methacrylonitrile, ~-chloroacrylonitrile, vinylidene chloride, Cl_4 alkyl acry-lates, C14 alkyl methacrylates, vinyl-substituted aromati.c compounds, such as styrene and vinyl toll~enes, dienes, such as 1,3-butadiene, 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene and 2-chloro-3-methyl-1,3-butadiene.
Carboxylic acids b) suitable for the process according to the invention include, for example, acrylic acid, methacrylic acid, 2-ethyl acrylic acid, 2-propyl acrylic acid, 2-butyl acrylic acid, itacon.ic acid and mixtures thereof; the most preferred carboxylic acid b) is meth-acrylic acid.
The emulsion polymerization may be carried out in alkaline or acidic aqueous medium; cf. "Ullmanns Encyklo Le A 27 723 4 padie der Technischen Chemie", Vol. 9, pages 366 et ~., Verlag Urban und Schwarzenberg, Munchen/Berlin 1957;
"Encyclopedia of Polymer Science and Technology", Vol. 3, pages 705 to 730, John Wiley, New York 1965; I'Methoden der Organischen Chemie" (Houben-Weyl) XIV/1, 733 et ~q., Georg Thieme Verlag, 5tuttgart 1961. The polymerization is preferably carried out in an acidic pH range of 1.5 to 5 and, more particularly, 2 to 4.
The pH value may be adjusted and maintained by addi-tion of mineral acids ~r water-soluble, organic, non-polymerizable acids. The system may be buffered for protection against unintentional shifts in the pH value.
Activators and activator systems are used to initiate and maintain the polym~rization reaction. Preferred activators or activator systems include hydrogen peroxide, water soluble salts of peroxodisulfuric acid, such as potassium peroxodisulfate, organic peroxides and, prefer-ably, redox systems, i.e. combinations of inorganic or organic peroxo compounds with suitable reducing agents.
2xamples o~ such redox systems include the combinations potassium peroxodisulfate/sodium dithionite, ammonium persulfate/sodium hydroxymethyl sul~inate, diisopropyl hydroperoxide/hydrogen sulfide and peroxide/triethanol-amine. The activators or activator systems are generally used in quantities of 0.1 to 3 mmol and pre~erably in quantities o~ 0.2 to 2.5 mmol per 100 g polymerizable monomer used.
Suitable emulsifiers are, basically, any anionic, cationic, amphoteric and nonionic emulsifiers ~except for protective colloids), i.e. compounds of the type described, for example, in 'IMethoden der Organischen Chemie" (Houben-Weyl), 4th Edition, Vol. 141, Georg Thieme Verlag, Stutt gart 1961, pages 190 et se~.
Preferred anionic emulsifiers are alkyla~yl sulfonates containing ~ to 18 carbon atoms in the alkyl radical, C81a Le A 27 723 5 alkyl sul~ates and sulfonates, sulfonated succinic acid esters, sulfonated, sulfated or phosphated addition prod-ucts of alkylene oxides (more particularly ethylene and, optionally, propylene oxides) with C~1z alkylphenol~ and water-soluble naphthalene ~ulfonic acid/formaldehyde condensates. Particularly pre~erred anionic emulsifiers are the salts of the sulfated ethoxylation product of nonylphenol preferably containing 3 to 8 ethoxy units per molecule. Preferred cations of the anionic emulsi~iers are sodium, potassium and ammonium. Other preferred ionic emulsifiers are the salts of the diterpene carboxylic acids obtained from tall oil, pine balsam and root rosin and, more particularly, the dispro~ortionation, partial hydro-genation and polymerization products thereof; see W.
lS Barendrecht, ~.T. Lees in Ullmanns Encyklopadie der tech-nischen Chemie, 4th Edition, Vol. 12, Verlag Chemie, Weinheim/New York 1976, pages 528-538.
Preferred cationic emulsifiers are amine salts, quaternary ammonium and pyridinium salts, such as salts of dodecyl amine, salts of esterification products of paraffin fatty acid and dimethyl aminoethanol, salts of condensates of oleic acid and N,N-diethyl ethylenediamine, salts of reaction products of primary amines with bis-(2-chloro-ethyl)-ether or 2 chloro-2'-hydroxydiethyl ether; cetyl pyridinium chloride, lauryl pyridinium sul~ate; the ~alts o~ hydrogenated or dehydrogenated abietylamines.
Pre~err~d nonionic emulsifiers are polyadducts based on ethylene oxide and/or propylene oxide.
The emulsifiers are generally used in quantities of 0.1 to 4% by weight and preferably in quantities of 0.5 to 2.5% by weight, based on monomers to be polymerized.
The process according to the in~ention may be carried out in the presence of so-called molecular weight regula-tors ("regulators" for short); cf. "Methoden der 0rganis-chen Chemie" (Houhen-Weyl), 4th Edition, Vol. 14/1, Georg Le A 27 723 6 Thieme Verlag, stuttgart 1961, pages 197 et ~g., more particul~rly pages 31~ et seq. The regulators may be used in quantities of o.l to 3% by weight and preferably in guantities of o.3 to 1.5~ by weight, based on monomers to be polymerized. Suitable regulators include CalB alkyl mercaptans, such as octyl mercaptan, linear or branched dodecyl mercaptan, tridecyl mercaptan or mixtures thereof, di-C420-alkyl xanthogene disulfides containing linear, branched or cyclic alkyl radicals, such as ethyl xanthogene disulfide, isopropyl xanthogene disulfide and bis-(methyl-enetrimethylolpropane)-xanthogene disulfide, polysulfides and haloforms, such as iodoform. Both molecular weight and gel content may be influenced by the regulators. It has been found that the adhesives made from dispersions pro-duced in accor~ance with the invention have particularlyfavorable properties when the gel content of the chloro-prene polymers does not exceed 95% by weight.
The gel content is the percentage component which is insoluble in tetrahydro~uran at 25C (allow 250 mg sample to stand in 25 ml THF for 24 hours, centri~uge and dry at 70C to constant weight).
A "seed inflow process" is understood to be a polymer-ization process in which an emulsion polymer (~Iseed~) is first prepared from a small part o~ the total monomers to be polymeriæed and the rest of the monomers to be polymer-ized are left to polymerize in the presence of the seed either in the same reaction vessel or in another reaction vessel. It is essential that the polymerization reaction used to prepare the seed is completed, i.e. the solids content must have increased to more than 95%, based on total monomer used. It is also essential that the monomers to be polymerized in the subsequent inflow process are introduced in a form which precludes the premature forma-tion of an emulsion in the inflowing monomer. In other words, the monomers on the one hand and the emulsifiers and Le A 27 723 7 activators on the other hand may be regularly run in separately. Where this procedure is adopted t it should thus be assumed that few new polymer particles axe formed, i.e. the monomers of the inflow polymerize onto the polymer particles of the seed. In one particular e~bodiment, a small part of the inflow monomers may first be added to the seed so that these monomers swell the polymer particles of the seed and, hence, can bring them into a "more polymeriz-able" state. The remainder of the inflow monomers may then be introduced, the inflow rate being determined not only by the claimed parameters, but also by how quickly the energy released during the exothermic reaction can be dissipated.
In practice, a seed inflow process such as this may appear, for example, as follows:
The monomer, emulsifier, regulator and the oxidizing component of a redox activator system are initially intro-duced into water. This mixture is then heated to reaction temperature and the reaction is initiated by addition of a reducing component of the redox activator system, preferab-ly in the form o~ an aqueous solution, optionally in admixture with more emulsifier and/or regulator. The mixture is left to react until there is no further increase in the solids content. The resulting polymer is the "seed".
If desired, a small proportion of monomer and, option-ally, regulator may then be added and the seed allowed to swell.
Monomers on the one hand and regulator, emulsifier and activators on the other hand are then separately added in such a way that the claimed ratio of polymer formed to fre~
monomer is not exceeded in the reaction mixture. The components are normally allowed to flow in uni~ormly, although the inflow of monomer and inflow of activator may also overlap in such a way that the inflow of monomer is over before the inflow of activator.

Le A 27 723 8 ~S~,5 The average particle size of the "seed" polymer is preferably 50 to 100 nm while the average particle size of the polymer in the dispersion prepared in accordance with the invention is preferably 100 to 300 nm and, more pre~er-ably, 100 to 200 nm, with the proviso that the average particle size increases by at least 50% during the in~low polymerization process. In the context of the invention, the "average particle size" is the ~ value according to DIN 53 206, i.e. the diameter which belongs to the arith-lo metic mean of all particle volumes or masses.
The average particle size may be determined by ultra-centrifuge measurements (H.G. Muller, Colloid & Polymer Sci. 267, 1113-1116 (1989~).
Dispersions containing no more than 1~ by weight, based on solids, polymer particles having an average particle size of more than 1 ~m can he produced by the process according to the invention.
The process according to the invention may be con-tinued to a final monomer conversion of more than 85~ by weight and preferably more than 95% by weight. However, the reaction may also be terminated at an earlier stage by addition of polymerization inhibitors, such as diethyl hydroxyl amine or phenothiazine/butyl pyrocatPchol mix-tures. Residual monomers may be removed in the usual way, for example with steam.
The dispersion accumulating on completion o~ polymer-ization in ~he acidic pH range may be adjusted to the desired pH value, preferably in the range ~rom pH 6 to pH
8, by addition of aqueous potassium or sodium hydroxide solution, by addition of ammonia or by addition of amines, such as for example diethanolamine or triethanolamine.
The dispersions prepared in accordance with the invention are suitable for the production of water-based adhesives which are free from, or low in, organic solvents.
In this context, "low'l means a content o~ less than 30% by Le A 27 723 9 ~5~ 5 weight (organic solvent), based on the final adhesive.
For the production of adhesives from dispersions prepared in accordance with the invention, it is possible for example to use fillers, such as silica ~lour, quartz sand, highly disperse silica, hea~y spar, calcium car-bonate, chalk, dolomite or talcum, optionally ~ogether with wetting agents, such as for examplP polyphosphates, such as sodium hexametaphosphate, naphthalene sulfonic acid, ammonium or sodium polyacrylic acid salts, the fillers generally being added in quantities of lo to 60~ and preferably in quantities of 20 to 50~ by weight, based on adhesive, and the wetting agents generally being added in quantities of 0.2 to 0.6% by weight, based on filler.
Particularly important additives are zinc and magnes-ium oxide which act as acceptors for small quantities of hydrogen chloride which can be eliminated from the poly-mers.
Other suitable auxiliaries are organic thickeners, such as for example cellulose derivatives, alginates, starch, starch derivatives or polyacrylic acid, which may be used in quantities of 0.01 to 1% by weight, based on adhesive, or inorganic thickeners, ~uch as bentonites ~or example, which may be used in quantitie~ af 0.05 to S% by weight, based on adhesive.
Fungicides may also be added to preserve the adhe-sives. Fungicides are generally used in quantities of 0.02 to 1% by weight, based on adhesive. Suitable fungicides are, for example, phenol and cresol derivatives or organo-tin compounds.
Tackifying resins, such as for example unmodified or modified natural resins, such as colophony esters, or synthetic resins, such as phthalate resins, may also be added to the adhesive. Organic solvents, such as for example toluene, xylene, butyl acetate, methylethyl ketone, ethyl acetate, dioxane or mixtures thereo~, ar plastic-Le A 27 723 10 2~

izers, such as for ~xample adipate-, phthalate- or phos-phate-based pla.sticizers, may also be added to the disper-sions prepared in accor~ance with the invention.
The adhesives thus prepared are suitable for bonding materials of the same kind or of different kinds to ~ne another, including for example wood, paper, plastics, textiles, leather, rubber and inorganic materials, such as ceramics, earthenware or asbestos cement.
In the following Examples, percentages and parts are by weight.

Examples Tests Determination of gel content The dispersion is applied to a ylass plate and dried for three days under nitrogen at room temperature to ~orm a film. 250 mg sample are dissolved or swollen in 25 ml THF (containing 1 g polymerization inhibitor per liter THF) for 24 hours at room temperature in a closed vessel. The mixture is ultracentrifuged for 1 hour at 20,000 r.p.m. and the percentage by weight of material removed by centrifug-ing is determined after drying.
Determination of peel strength The test is carried out in accordance with DIN 53 273.
A 100 ~m thick wet film of the dispersion is applied to two test specimens ~Nora rubber, roughened, lOOx30 mm) and aired ~or 1 hour at room temperature. The test spec-imens are then fitted together for 10 seconds under a pressure of 4 bar. The bond is then tensile tested at room temperature in a commercially available tensile testing machine. The strength values are determined immediately after bonding and khen after 1 and 9 days.

Le A 27 723 11 i9~5 Determination o~ tensile shear strength Beechwood test specimens measuring 40x20x5 mm are coated twice with the dispersion so that a 100 ~m thick wet film is formed. After drying for 30 minutes at room temperature, the test specimens are fitted together so that they overlap over an area of 20 x 10 mm (1 minute, 0.3 bar). Tensile shear strength is measured immediately af~er ~onding and then a~ter 1 day and 9 days.
Determination of the carbo~ylate group content in the serum and in the polymer The determination is effected by conductometric titration in dependence upon the pH value.
The conductivity of the original latex and the latex after serum exchange are measured in dependence upon the adjusted pH value. The carboxyl group contents both in the original latex (= sum of COOH groups in the serum + poly-mer) and in the polymer can be determined from the titra-tion data.

Determination o~ shear stability Shear stability is determined by stirring the disper~
sion with an IKA U-Turrax s~irrer. The dispersion is sheared for 5, 15 and 30 minutes at 5,000 r.p.m. and then examined for fish eye fo~ma~ion or coagulate.

Assignment:
S minutes' shearing without coagulate: inadequate (-~
15 minutes' shearing without coagulate: satisfactory (o) 30 minutes' shearing without coagulate: very good (+) The modulus of elasticity is determined in accordance with DIN 53 455 and 53 457.

Le A 27 723 12 %~

Determination of water absorption 1. ample preparation In accordance with the formula:
5.6 x density polymer = g dispersion, solids content dispersion is poured into a tin dish (60 mm 0 x 8 mm height) until a 2 mm thick film is formed.
The adhesive film is stored for 14 days in a standard conditioning atmosphere until it is complete-ly dry. Two 20 x 20 mm test specimens are then prepared, weighed on an analytical balance (accuracy + 0.001 g) and stored in water for 24 h at 23C. The test specimens are then wiped with a dry paper tissue.

2. Measurement The weight of the adhesive films is then deter-mined. The increase in weight (water absorption) is expressed in ~.

Determination of contact adhesion time Cminutes]
In a standard conditioning atmosphere (23C/50~
relative air humidity), 5 mm wide and 0.32 mm thick adhe-sive films are applied in a length of approx. 300 mm to index card (250 g/m2) using a stencil of 0.32 mm thick wood-free art cardboard (weight per unit area 246 g/m2) and a film applicator.
Approx. 30 mm long adhesive films are cut out from these samples at time intervals of 5 mins. and are applied crosswise in pairs to the stamp of an apparatus so that a bonded area of 0.25 cm2 is formed. This bonded area is subjected to a constant load of 50 g for 10 seconds.

Le A 27 723 13 2~S~

The contact adhesion time is at an end when the adhesive films no longer adhere ~o one another a~ter removal from the apparatus.

Products used The ammonium salt of a sulfated ethoxylated nonyl phenol containing on average four ethoxy groups per mole-cule is used as the emulsifier.
The product o~ Comparison Example 1 is ~Neoprene 115, a product of DuPont, Wilmington/Del.~ USA.
The product of ComparisGn Example 2 is ~ispercoll C
74, a product of Bayer AG, Leverkusen.

ExamPles 1 to 5 (Seed inflow process with "internal seed") 0.25 part ammonium persulfate (APS), 88.5 parts deionized water, 0.07 part emulsifier, 4.2 parts chloro-prene, 0.15 part methacrylic acid and 0.1 part tert.
dodecyl mercaptan (t-DDM) are introduced into a stirred reactor.
The reaction vessel is heated to the polymerization temperature (see Table 1) and the polymerization reaction is initiated by starting the inflow of activator consisting of 6.8 par~s deionized water, 0~05 part sodium hydroxy-methyl sulfonate and 1 part ~mulsifier. AEter a reactiontime o~ 45 minutes, no further increase in the solids con~
tent is observed. The polymer particles of the resulting dispersions had an average particle size of 55 to 65 ~m.
4.2 Parts chloroprene and 0.15 part t-DDM were then added to the "seed". After a swelling time of 15 minutes, a monomer inflow of 90.8 parts chloroprene, 3.8 parts methacrylic acid and 1 part t-DDM is uniformly started.
On completion of the monomer inflow (8 hours) and the activator inflow (12 hours), the dispersion i5 freed from residual monomer by distillation with steam a~d adjusted Le A 27 723 14 ~:~?5~ 5 with ammonia to pH 6,5--7.5.
In the following, PS stands for "particle size" and PS
for "average particle size".
Table 1 Examples Temp. t~C] 10 15 20 25 30 Gel content t~] 5 Peel strength [N/mm]
- immediately 1.4 o.7 o.6 0.6 0.7 - 1 day 8.3 2.2 2.0 2.0 2.2 - 9 days 9.9 5.1 4.6 4.0 5.1 Contact adhesion 1 >8 >~ >8 >8 time [h.]
PS [nm] 147 lS2 155 151 15B
Examples 6 and 7 Further polymerizations were carried out using the formulation of Example 3 except that the guantity of methacrylic acid was varied. The reactions were carried out by the process described for Examples l to 5.

Table 2 Examples (Comparison) (Invention) ~ethacrylic acid [Parts] 0 1.9 3.8 Gel content t~] <5 <5 Peel strength tN/mm]
- immediately 0.4 0.~ 0.6 - 9 days 1 78 4 6 2 0 Contact adhesion time [h.] >8 ~8 ~8 PS tnm] 166 151 155 Le A 27 723 ~5 Examples 8_to 11 Dispersions having different regulator contents were prepared on the basis of the formulation of Example 3.

Table 3 Examples (Comparison) (Invention) .
t-DDM [parts] 0 0.25 0.50 0.75 1.00 Gel content >95 95 94 <5 <5 Peel strength [N/mm] .
- immediately 0.1 1.0 1.0 1.6 0.6 - 1 day 0.1 2.9 3.4 3.0 2.0 - 9 days 0.1 4.1 4.0 5.6 4.6 Contact adhesion time th.] - >8 >8 >8 >8 PS [nm] 155 147 138 150 155 Le A 27 723 16 Example 12 (Seed inflow process with "external seed") Seed latex:
0.34 Part ammonium persulfate, 112.75 parts deionized water, 0.34 part 10% aqueous sulfuric acid, 0.69 part sodium dodecyl benzenesulfonate, 0.21 part dipotassium hydrogen phosphate, 3.31 parts chloroprene, 0.14 part methacrylic acid and 0.69 part t-DDM are introduced into a stirred reactor. The reactor is temperature-controlled to 200C and the polymerization reaction is activated by starting an inflow consisting of 13.75 parts deionzed water and 0.12 part sodium hydroxymethyl sulfinate (inflow time 11 hours). 30 minutes after the start of the inflow of activator, a monomer inflow of 63 parts chloroprene and 2O35 parts methacrylic acid is started (inflow time 10 hours). PS of the seed latex: 63 nm.

Grafting stage:
0.54 Parts ammonium persulfate, 65 parts deionized water, 0.17 part emulsifier, 0.25 part dipotassium hydrogen phosphate, 0.25 part 10% aqueous sulfuric acid, 15 parts of the seed latex, 2.9 parts chloroprene, 0.1 part methacrylic acid and 1 part t-DDM are introduced into a stirred reac-tor. The reactor is temperature-controlled to 20C and the polymerization is initiated by starting an inflow (20 parts deionized water, 0.18 part sodium hydroxymethyl sulfonate, 1 part emulsifier, inflow time 17 hours). After 30 min-utes, a monomer inflow of 93.5 parts chloroprene and 3.5 parts methacrylic acid is started (inflow time 15 hours).

Table 4 Gel content ~%] 20 Peel strength [N/mm]
- immediately 1.7 - 1 day 3-4 Le A 27 723 17 - g days 5.8 contact adhesion time [h.] >8 PS [nm] 200 Comparison Examples 1 and 2 Commercially available polychloroprene latices corre sponding to the prior art were used for comparison with the dispersions according to the invention.

Example 12 comparison Examples Solids [%] 49.7 45.3 55.1 pH value 6.9 6.9 12.4 Gel content [%] 21 55 13 Av. PS ~nm] 208 290 110 E modulus [MPa] 1.15 0.61 Peel strength ~N/mm]
- immediately 1.7 0.4 3.2 ~ 1 day 3.4 0.9 8.8 - 9 days 5.8 1.7 9.6 Contact adhesion time [h.] >8 >8 <0.5 Water absorption [%] 4 33 Shear stability + - -COOH groups/serum [~] 14 68 80 COOH groups/
polymers [%] 86 32 20 Le A 27 723 18

Claims (7)

1. A process for the production of aqueous dispersions of chloroprene polymer containing a) 90 to 99.6% by weight copolymerized chloroprene, of which up to 10% by weight may be replaced by other copolymerizable monomers and/or up to 2% by weight by sulfur, based in either case on a), and b) 0.4 to 10% by weight copolymerized .alpha.,.beta.-ethylenically unsaturated carboxylic acid corresponding to the following formula in which R represents hydrogen, C1-4 alkyl or CH2COOH, by emulsion polymerization at 5 to 35°C by the seed inflow method in the absence of protective colloids, in which 70 to 98% by weight monomer (a+b) ("inflow") is polymerized in the presence of 2 to 30% by weight polymer formed from the monomers a and optionally b ("seed"), the inflow being regulated in such a way that the ratio by weight of polymer formed to free monomer in the reaction mixture at any stage of the subsequent polymerization process is >50:>50, the percentages of components a) and b) on the one hand and of seed and inflow on the other hand adding up to 100.

2. A process as claimed in claim 1, in which the polymer-ization temperature is 10 to 30°C.

3. A process as claimed in claim 1, in which 90 to 95% by weight inflow is polymerized in the presence of 5 to 10% by weight seed.

4. A process as claimed in claim 1, in which the inflow is regulated in such a way that the ratio by weight of Le A 27 723 19 polymer formed to free monomer in the reaction mixture at any stage of the subsequent polymerization process is >70:<30.

5. A process as claimed in claim 1, in which the inflow is regulated in such a way that the ratio by weight of polymer formed to free monomer in the reaction mixture at any stage of the subsequent polymerization process is >80:<20.

6. Dispersion obtainable by the process claimed in claims 1 to 5.

7. The use of the dispersions claimed in claim 6 for the production of adhesives.

Le A 27 723 20