FI62119C - MED ISOTIO CARBIDS STABILIZERS LATEX AV EN VATATENOLOESLIG ORGANIC POLYMER LAEMPLIG FOER ANVAENDNING VID ELEKTRODOPPLACKERINGSFOERFARANDEN - Google Patents

Description

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Patent · OCh registerttyrelaan AntOkan utlagd ech utl. * Krlft »n published 30.07.82 (32) (33) (31) Pyydatty« tuolkeuj - & «{ird prlorltat (71) The Dow Chemical Company, P.0. Box 1967, 2030 Abbott Road, Midland,

Mi chi gan, USA (72) Earl Henry Wagener, Concord, Michigan, Ritchie Antone Wessling,

Midland, Michigan, Dale Sabin Gibbs, Midland, Michigan, USA (74) Oy Kolster Ab (54) Isothiourea-stabilized latex of water-insoluble organic polymer for use in the electroprecipitation process elektrodopplackeringsförfaranden

The invention relates to colloidal aqueous dispersion polymers, i.e. latexes stabilized with isothiourea cations.

U.S. Patent 3,123,636 discloses thiourea halides, which are water-soluble viscous oils that can be used as insect traps as well as bactericides. The patent states that the compounds cause foaming when mixed with water with shaking, so they have surfactant properties.

U.S. Patent 3,594,355 describes water-soluble isothiourea salts of epihalohydrin polymers and copolymers. These water-soluble salts have been found to be highly useful as wool shrinkage testers, wet and dry paper additives, flocculants, crosslinkable textile coatings, and semipermeable films. However, that publication does not suggest that any kind of latex could be made from the polymers.

U.S. Patent 3,642,879 discloses S- (vinylbenzyl) isothiourea L compounds having the isothiourea moiety of the formula 62119, ™ 2 // // - s - cx \ NH2 These compounds are useful as plant protection agents for controlling various plants, insects and mold pests. . They are monomers that can be polymerized. The publication describes a latex formed from a copolymer of one of these compounds with styrene and butadiene. However, such latexes are useful and stable only under acidic conditions in a narrow pH range.

The present invention provides colloidal aqueous dispersions of cationic particles in which the polymer forming the dispersed particles is a water-insoluble, substantially electrically non-conductive organic polymer in which a substantial portion, at least half or more of the cationic activity is provided by isothiourea cations having only a covalent nitrogen atom. The colloidal aqueous dispersions, i.e. latexes, have a pH of about 2-12, preferably about 6-10, and a particle size of about 500-10,000 Å, preferably about 800-5,000 Å.

The dry electrically non-conductive, water-insoluble organic polymer latex used in the cathodic electroprecipitation process of the present invention, having a pH of about 2 to about 12 and a particle size of about 500 to 10,000 Å, is further characterized in that it contains particles in the aqueous dispersion. stabilized with cationic groups, a substantial part of which are isothiourea groups in which the nitrogen atom is covalently bonded only to the carbon atom.

It is a prerequisite of the present invention that the polymeric component is in the form of an aqueous dispersion of cationic particles, wherein a substantial portion, at least half, or more of the cationic activity is provided by isothiourea cations. Such cations can be incorporated into the polymer in various ways. For example, a surfactant containing an isothiourea cation can be used in the preparation of polymers by emulsion polymerization, where the surfactant 3 62119 is adsorbed on the polymer. Alternatively, the latex can be prepared by emulsion polymerization using other emulsifiers and replacing at least most of the polymerization emulsifier in such latices by removing this emulsifier, e.g. by dialysis or ion exchange, and replacing it with an isothiourea surfactant. Yet another method is to render preformed polymers obtained, e.g., by bulk polymerization, into aqueous dispersions with a similar surfactant used to dissolve the polymer in a solvent and then mixing the solution with water and surfactant and finally removing the solvent to provide a latex composition. Yet another method is to prepare a water-in-oil dispersion by adding an isothiourea cation surfactant to the preformed polymer and then slowly adding water to the water-in-oil dispersion with stirring until inversion occurs and an oil-in-water dispersion is formed. The isothiourea cation can also become part of such a polymer, e.g. by copolymerization with other monomeric particles of the polymer, the monomer of which contains an isothiourea cation, such as S-vinylbenzyl-Ν, Ν, Ν ', N'-tetramethyl-isothiourea chloride.

Monomers containing unsaturated double bonds polymerized by emulsion polymerization are represented, for example, by nonionic monomers such as alkenyl aromatic compounds such as styrene compounds; derivatives of ίΛ-methylene monocarboxylic acids such as acrylic esters, acrylonitriles and methacrylic esters; O, N-ethylenically unsaturated derivatives of dicarboxylic acids such as maleic esters; unsaturated alcohol esters; conjugated dienes; unsaturated ketones; unsaturated ethers, as well as other polymerizable vinylidene compounds such as vinyl chloride and vinylidene fluoride. Particular examples of compounds containing unsaturated double bonds include styrene, C 1-4 methylstyrene, arylmethylene-aryl-dimethyl-aryl-ethyl-styrene, n-ethylstyrene, , ar-diethylstyrene, t-butylstyrene, vinylnaphthalene, hydroxystyrene, methoxystyrene, cyanostyrene, acetylstyrene, monochlorostyrene, dichloro-styrene, and other halo-styrene, methyl acrylate, ethyl acrylate, ethyl acrylate, butyl acrylate, butyl acrylate, -hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate and 4-hydroxybutyl methacrylate, acrylonitrile, methacrylonitrile, acrylanilide, vinyl azide, vinyl acetate, vinyl acetate, vinyl acetate, vinyl acetate, ethyl maleate, ethyl maleate, ethyl maleate, ethyl maleate nylidene difluoride, vinyl methyl ketone, methyl isopropenyl ketone, vinyl ethyl ether, 1,3-butadiene and isoprene.

Such nonionic monomers form water-insoluble homopolymers or water-insoluble copolymers when more than one of the groups is used. However, other monomers which are water-soluble as homopolymers can be used as copolymerized parts with the above-mentioned monomers. Hydrophilic, water-soluble monomers include, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylamide, methacrylamide, and other modified acrylamides such as diacetone acrylamide and diacetone methacrylamide.

These monomers are not used in such large quantities that the copolymer becomes water-soluble or significantly electrically conductive. The proportion of such a somewhat hydrophilic, water-soluble monomer that can be copolymerized with the polymer behaving in accordance with this invention will normally range from 0-30% of the total weight of the copolymer.

The term "substantially hydrophobic, emulsifiable polymerizable, unsaturated double bond monomer composition" as used herein means a monomer or mixture of monomers as defined above.

In one embodiment, the aqueous dispersion of the invention is conventionally prepared from the above monomers by emulsification polymerization using a free radical generating catalyst, usually from about 0.01 to 3% by weight of the monomer, and an isothiourea surfactant as defined herein in conventional mixing, under weight and temperature conditions, using either batch, addition, or continuous addition of monomers, water, and other particles to the reaction vessel or series of such vessels, or by polymerization in a helical reactor. In another embodiment, the isothiourea monomers disclosed herein are copolymerized with the above monomers in the same manner except that the amount of isothiourea surfactant is reduced or omitted altogether. In both embodiments, the usual additives for latex compositions may be included in the mixture in small ordinary amounts in the usual manner. Such agents include, but are not limited to, chain transfer agents, short retarders, buffers, foaming agents, chelating agents, inorganic salts, plasticizers, colorants, antimicrobials, or other preservatives, etc. Small amounts of nonionic or other cationic agents. -active substances can also be added, especially when smaller amounts of monomeric isothiourea salts are used. Sometimes i s o t i ocarbami di surfactant or other surfactant; ·; the substances are added to the polymerization mixture as parts of a preformed initial latex. In one process, a small amount of the initial latex is added to water, polymerizable isothiourea salts, other additional monomers, free radical generating catalysts, and other additives used in emulsification polymerization by addition or continuous addition. , which temperatures are usually between 0 and 100 ° C, preferably below 90 ° C. It is often advantageous to keep the amount of monomer added as low as necessary so that the amount of monomer added controls the degree of polymerization.

Catalysts are of the type which produce free radicals and are usually per-oxygen compounds, for example inorganic persulphate compounds such as sodium persulphate, potassium persulphate and ammonium perulphate; inorganic peroxides such as hydrogen peroxide; organic hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; organic peroxides such as benzoyl peroxide, acetyl peroxide, lauryl peroxide, peracetic acid and perbenzoic acid, sometimes activated with water-soluble reducing agents such as iron compounds, sodium bisulphite or hydroxylamine hydrochloride 2.2 and other free radicals such as

The polymeric portions of such products may be polymers that are not readily prepared from monomers by emulsification polymerization, either because significant polymerization is not achieved to a commercially acceptable extent under conventional emulsification polymerization conditions, such as isobutene, or because a particular form of polymerized monomer is desired. Typical preformed polymers include polymers and copolymers of monoolefins having 2 to 20 carbon atoms such as ethylene, propylene, 1-butene, 2-butene, isobutene, pentene, hexene, octene, dodecene, hexadecene, octadecene, and in particular mono-olefins with Θ

6 621 1 S

carbon atoms. Particularly common are various ethylene / propylene copolymers.

Exemplary examples of other suitable polymers in the present invention include alkyd resins, block and graft polymers; for example styrene / butadiene graft and block polymers; epoxy resins such as reaction products of epichlorohydride and bisphenol-A; thermosetting vinyl ester resins, e.g. reaction products of approximately equal amounts of polyepoxide and unsaturated monocarbocyclic acid, such as acrylic acid and methacrylic acid, or reaction products of unsaturated fatty acids, such as oleic acid.

Methods for preparing the above polymers are well known and do not fall within the scope of this invention. The polymers are converted to aqueous dispersions by the methods described above.

Aqueous dispersions, i.e. latex compositions, regardless of their method of preparation, are usually prepared with a polymer solids content of 35-60, preferably about 4Ό-50 $. Kundispers are used for some purpose, e.g. in an electroprecipitation process, they can be diluted with water to the desired lower solids content before use such as 2-35%.

Aqueous dispersions can be used over a wide pH range such as about 2-12. However, since corrosion occurs below pH 6, operation in areas above pH 6 is recommended. Although isothiourea compounds are useful at values above pH 10, they degrade over time at such high pH. For this reason, a pH range of about 6-10 is especially recommended. If latexes need to be stored for some time, the pH must be maintained, during these times between 6-8.

Isothiourea surfactants, as well as other surfactants or emulsifiers in general, contain a hydrophobic and hydrophilic moiety. The hydrophilic portion of the isothiourea surfactant contains the hydrophilic portion of the isothiourea surfactant contains an isothiourea group represented by the formula -SO 2 or one of its resonant forms. If the dose must be pH independent, none of the free valences in the formula must be hydrogen . In this case, N-tetrasubstituted isothiourea compounds are preferred. The quality of the hydrophobic part is not important. The present invention relates to aqueous dispersions of polymers which are kept in dispersion mainly by isothiourea cations. Water-soluble salts of isothiourea surfactants or emulsifiers of formula 7 '2 62119 R'-S-C R4

\ / z N

XR5 wherein R * is a long chain, monovalent hydrophilic radical in which 2 is 8-25 carbon atoms, R and R are separately alkyl or hydroxyalkyl having 1-4 carbon atoms, R1 and R1 are independently alkyl or hydroxyalkyl having 1 -4 carbon atoms or are attached to a single divalent radical of 2-3 carbon atoms and z ”is a water-soluble counter anion. R 'may be a hydrocarbon radical or a primary hydrocarbon chain which may be cleaved by oxygen, sulfur, nitrogen, phosphorus or may have a keto, ester or amide bond or an end group such as hydroxy, keto, ester or amide. Hydrophilic groups are not limited to linear chains and may contain aromatic moieties such as alkyl.

The copolymerizable monomers which can be used to obtain isothiourea groups in a polymer have a formula similar to the surfactants given above, except that R 1 is a monovalent organic radical, e.g., aliphatic, aromatic or alicyclic with polymerizable unsaturated double bonds. When such monomers are used, the proportion is less than that which would be required to make the resulting copolymer water-soluble or electrically conductive in the dry state.

In the practice of the present invention, the counterion Z ~ is an anion and need not be water-soluble throughout the pH range, but must be water-soluble at the pH range accepted for the particular process or use expected of the product. The counter anion Z ~ is an anion that does not coagulate the dispersion. Typically, the anion is an anion of an inorganic acid such as chloride, bromide, fluoride, nitrate, sulfate, bicarbonate, and phosphate; or an anion of an organic acid such as acetate, maleate, citrate, propionate, fumarate acrylate, and benzoate or hydroxide.

Isothiourea compounds can be obtained by modifying the method disclosed in U.S. Patent 3,721,581 by reacting R'X in the hands of an N-tetrasubstituted thiourea of the formula H2 s = c ^ £ 4 \ s

OF

wherein R ', R 1, R 2, and R 2 are as defined above and X is halogen. In particular, R 'is better presented than that disclosed in said patent.

Compounds represented by the formula R'X include alkyl chlorides having 8 to 25 carbon atoms, such as n-octyl chloride, 2-ethylhexyl chloride, n-dodecyl chloride, tetradecyl chloride, cetyl chloride, eicosyl chloride, dodecyl chloride and tetradocyl chloride; alkyylibentsyylikloridit in which the alkyl has 4 to 18 carbon atoms such as n-butyylibentsyylikloridi, isoheksyylibentsyylikloridi, n-oktyylibentsyylikloridi, dodekyylibentsyylikloridi, tetradekyylibentsyyli chloride, and oktodekyylibentsyylikloridi} alkyylifenetyylikloridit as butyylifenetyylikloridi, heksyylifenetyylikloridi, oktyylifenetyylikloridi, dodekyylifenetyylikloridi, tetradekyylifenetyylikloridi, and hexadecyl-fenetyylikloridi; and dialkyl σ-chlorosuccinates such as diamyl α-chlorosuccinate, dihexyl α-chlorosuccinate, diheptyl α-chlorosuccinate diheptyl α-chlorosuccinate, dioctyl α-chlorosuccinate, dinonyl α-chlorosuccinate, didecyl α-chlorosuccinate and didodecyl α-chlorosuccinate. Compounds represented by the formula R'X which can be used to prepare copolymerizable monomers containing isothiourea groups include vinylbenzyl chloride allyl chloride, bromoalkyl acrylates, bromoalkyl methacrylates and 2-methylene-5-butenyl chloride. The corresponding bromides and iodides are suitable instead of chlorides.

N-tetrasubstituted thioureas are represented by tetramethylthiourea, tetraethylthiourea, N, N, N ', N'-tetrahydroxyethylthiourea, N, N, N', N'-tetrahydroxylpropylthiourea, N, N, N *, N'-tetrahydroxybutylurea '-ethylene-Ν, Ν'-dihydroxyethylthiourea, N, N'-dimethyl-N, N * -dibutylthiourea, N, N'-dimethyl-N, N-diethylthiourea and N, N'-diethyl-Ν, Ν'- diethyl-NiR'-dipropyylitiokarbamidi.

The particle size (average diameter) of the aqueous dispersion or latex is usually in the range of 500 k to 10,000 Å, preferably in the range of about 800 k to n.

5,000 k.

The polymer moieties have hydrophobic properties due to the nature of the polymer as well as some hydrophilic properties due to positive charges, and therefore some cationic nature due to isothiourea groups on the surface of the particles, such as an adsorbed emulsifier or a copolymerized suitable to cause dispersion in water, but not sufficient to cause water solubility and electrical conductivity in a dry organic polymer. Thus, isothiourea groups in polymers are derived from surfactants containing them, or from the copolymerization of monomers containing them, or from the conversion of another substituent group in the polymer to isothiourea groups. The isothiourea group, i.e. the cation, has the formula: 9 R2 621 19 +

-s-c ^ X

\ y

OF

X5 - 2 3 4 5 and my counterion is Z, where H, R, E, R and? are as defined above for what is an isothiourea surfactant. The number of cationic groups is usually about 0.0? from milliequivalents to about 0.4 milliequivalents per gram of polymer.

In this specification, as well as in the appended claims, the term "phthalation-active particles" as used for polymer particles means the above particles.

The products of this invention can be used in the deposition process in the coating of electrically conductive surfaces, i.e. in the coating of products having an electrically conductive surface.

Electroprecipitation processes in which the products of this invention can be used are disclosed in U.S. Patent 1,363,674, Aug. ? 1. on 1974 ·

The following examples provide illustrative information on how the present invention I may be practiced. All parts are by weight and all percentages are by weight unless otherwise indicated.

Example I

The thermoplastic acrylic latex is prepared as follows. A monomer mixture is prepared from 960 grams of hutyl acrylate and 640 grams of styrene, to which is added 10 g of a 82.7 baked solution of t-butyl hydroperoxide to form a monomer feed solution. An initial solution of 750 g of a surfactant solution prepared by mixing 745 g of water and 5 g of dodecylbenzyl-Ν, Ν, Ν ', N'-tetramethylisothiourea chloride under a nitrogen atmosphere is prepared for two hours under nitrogen, to which 25 g of monomer are then added. -feed solution followed by a continuously added reducing stream pumped at a rate of 7.67 g / h for about two hours, the stream being part of a solution prepared in advance from 9 grams of hydroxylamine hydrochloride diluted to 500 grams with deionized water. To this initial latex is added a monomer feed solution at a rate of 55 g / h by continuing the reducing flow at the same rate and composition as in the preparation of the initial latex and simultaneously pumping a 20 g / h surfactant solution prepared from 465 grams of deionized water and 25 g / h water into the reaction mixture. dodekyylihentsyyli-Ν, Ν, Ν *, N tetrametyylisotiokarbamidikloridista. 20 hours after the pumping of the 10 6 21 1 9 monomer has been stopped, 0.5 g of tert-butyl hydroperoxide is added and the reaction is continued for a further 2 hours. The product is a pure liquid latex with a solids content of 41 »1 i ° and a particle size of 1170 Å.

Example 2

Preparation of surfactant solution A.

A mixture of 67 x 1 grams (0.22 moles) of hexadecyl bromide and 26.4 grams (0.20 moles) of tetramethylthiourea is diluted with ethanol to a total weight of 200 g, which is then stirred at 85 ° C for 8 hours. The resulting crude product is filtered and extracted with hexane and then added to 500 parts of water. The resulting mixture is then stripped in vacuo at 35 ° C. The product is an aqueous solution containing 0.73 milliequivalents of hexadecyltetramethylisothiourea bromide per gram of solution (31> $ 9 active solution by weight).

Preparation of monomer Ben 1 isothiourea salt (comonomer emulsifier) solution B.

The mixture is prepared from 66 grams (0.5 moles) of tetramethylthiourea, 84 grams (0.55 moles) of vinylbenzyl chloride and 350 gtaO®a in methanol. The mixture is filtered and 480 grams of the filtrate are taken up in a flask which is brought to a temperature of 70 ° C and kept under stirring under a nitrogen atmosphere for 5 hours. 20 g of water are added to the crude product obtained. The product is an aqueous solution containing 1.16 milliequivalents of vinylbenzyltetramethylisothiourea chloride per gram of solution.

Manufacture of latex

The following ingredients are charged to the reactor: 2 parts of 2,2, -azobisisobutyronitrite

4 parts of surfactant solution A

water is added to a total of 300 parts 40 parts methyl methacrylate 60 parts ethyl acrylate

Nitrogen is introduced into the reactor and the contents are heated to 70 ° C with stirring. After 40 minutes, comonomer emulsifier B, previously diluted to $ 5 in active solution, is added at a rate of 10 parts per hour for 4.5 hours. At 70 ° C, the reaction conditions and stirring are continued for a total reaction time of 15 hours. Filtration gives a highly flowable permanent latex with a solids content of $ 23.9 and a particle size of 865 Å and containing 0.17 milliequivalents of isothiourea groups per gram of polymer.

Electrodeposition of latexes

Sufficient diammonium bisphosphate is added to a portion of the above latex to give a conductivity of 1500 microsiemens per centimeter, the pH is adjusted to 7.7 *, and the resulting product is diluted to 10 VJ> solids.

n 62119

The above product is used for coating zinc phosphatized steel sheets by cathodic electroplating. For each set, a rectangular polyethylene electroprecipitation cell with two graphite thianodes of the same size and spaced far apart is filled in part with latex. A rectangular sample, approximately 70 x 123 x 1.6 mm, of said metal, is immersed in the latex to a depth such that 2 to 10,000 mm of metal surface is in contact with the latex, halfway between the anodes, surface 70 x 123 mm perpendicular to the anode. A 150 volt DC power supply is connected separately to each anode as well as to each of the samples as cathodes. After 30 seconds, the power is turned off.

The results obtained for electroprecipitation are given as the average of the test results of the two plates, unless otherwise stated.

The coated sheets are removed from the pool and cleaned with deionized water. The even coating stays firmly attached during cleaning. After drying, the weight of the coating is 1.9 milligrams per square centimeter. During the process, the power is turned off quickly.

Example 3

Manufacture of latex

The following ingredients are introduced into the reactor: 1 part dodecylbenzyldimethylsulfonium chloride 2 parts 2,2 · -azohisobutyronitrile 0.4 parts dodecanediol 0.2 parts 2,6-di-tert-butyl-4-methylphenol 9.2 parts of comonomer emulsifier solution B from Example 2 (3 parts active)

Sufficient additional water to replenish 500 parts 64.5 parts styrene 82.3 parts butadiene

Nitrogen is introduced into the reactor and the contents are heated to 85 ° C and kept there and stirred for 16 hours. The result is a product with a solids content of 29.2 56 and this is evaporated in vacuo to give a liquid latex with a solids content of 31 »9 i» and a particle size of 1.140 K.

Latex electroprecipitation ^ An

To this portion of said latex is added 0.1 milliequivalents of surfactant solution A per gram of solids, the conductivity is adjusted to 1500 with diammonium bisphosphate, and the pH is adjusted to 7.6 with ammonium hydroxide. The resulting product is electroprecipitated on sheet phosphatized steel sheets as described in Example 2, except that the electrical voltage is 200 V, which is maintained for 2 minutes, instead of 150 V and JO seconds in Example 2. During the process, the stability of the bath is good and the power failure occurs quickly. The highly hydrophobic coating thus obtained on the steel sheets is very strongly associated with water rinsing. After drying, the coating is found to be 0.5 mm thick and the weight of the coating to be 0.56 milligrams per square centimeter.

Example 4

The aqueous dispersion is prepared from 50 grams of a polyhutadiene resin having a molecular weight of 5,300 and 4 grams of an aqueous solution containing 0.73 milliequivalents of dodecylbenzyltetramethylisothiourea chloride per gram of solution by slowly adding 30 g of water to give with a particle size of about 10,000 Λ.

The aqueous dispersion of polybutadiene resin is treated for use in electroprecipitation by adding sufficient dodecylbenzyltetramethylisothiourea chloride to 0.2 milliequivalents per gram of resin, diluting, dispersion with water to 300 grams, raising the conductivity to 850 with diammonium bisphosphate and adjusting the pH to 8.

The treated latex is mixed with 20 grams of an aqueous dispersion containing 50 Io of pigment, of which $ 99 is titanium dioxide and 1 ° already carbon black (Raven 1500) and 0.1 milliequivalents of dodecylbenzyldimethylsulfone chloride per gram of pigment; the mixture is then diluted to 36Ο g with water.

The resulting electrodeposition is performed on zinc phosphatized steel sheets by the methods set forth in Example 2, except that the electrical voltage is 100 V. The process has a rapid power failure. A highly hydrophobic coating is obtained. After rinsing with water and heating at 175 ° C for 20 minutes, the coating has a thickness of 0.33 mm and a coating weight of 4.6 milligrams per square centimeter.

Claims (9)

1. A latex of a water-insoluble organic polymer which is electrically nonconductive in a dry state suitable for use in electrodeposition process has a pH of about 2 - about 12 and a particle size of about 500 - about 10,000 Å, and which latex is further , characterized in that it contains particles that are stabilized in water dispersion by cationic groups, a substantial part of which is isothiouronium groups containing nitrogen atoms with covalent bonds only to carbon atoms. 2. Xr5 wherein R and R are individually alkyl or hydroxyalkyl of 1-4 carbon atoms, R 4 and R are individually alkyl or hydroxyalkyl of 1-4 carbon atoms or are combined in a divalent radical of 2-3 carbon atoms, and Z is a water-soluble anion. Latex according to claim 1, characterized in that the total amount of cationic groups is about 0.02 - about 0.4 milliequivalents per gram of polymer. 3. Latex according to claim 1, characterized in that the isothiouronium group has the formula 2 R Latex according to claim 1, characterized in that the isothiouronium group is provided by an adsorbed isothiouronium surfactant. 5. Latex according to claim 4, characterized in that the isothiouronium surfactant is dodecylbenzyltetramethylisothiouronium chloride. Latex according to claim 1, characterized in that the isothiouronium groups are provided by a copolymerized monomer containing an isothiouronium group of the formula (? / R2 VN ^ r3 R'-S-C, Z