FR2477555A1 - PREPARATION OF LOW VISCOSITY AND HIGH SOLIDS COPOLYMER LATEX - Google Patents

Abstract

THE INVENTION CONCERNS A PROCESS FOR PREPARING COPOLYMER LATEX STARTING FROM AT LEAST ONE MONOMERIC VINYL ESTER REPRESENTING 50 TO 95 OF THE TOTAL MONOMERS INTRODUCED AND AT LEAST ONE MONOMER CHOSEN FROM ACRYLATE OR METHACRYLATE ESTERS. IN A FIRST STAGE, A SIGNIFICANT PART OF THE TOTAL VINYL ESTER AND 0 TO 50 OF THE TOTAL WEIGHT OF ACRYLATE AND OR METHACRYLATE ESTER IS POLYMERIZED IN A WATER-BASED EMULSION MEDIUM CONTAINING A POLYMERIZATION CATALYST AND, THEN, IN A SECOND STAGE THE REST OF THE VINYL ESTER AND THE REST OF THE ACRYLATE AND OR METHACRYLATE ESTER ARE POLYMERIZED.

Description

The invention relates to the field of copolymer latices and more

  in particular, latexes having a high solids content and a low viscosity, which are prepared starting from a copolymerizable monomer mixture comprising a vinyl ester and an acrylate or methacrylate ester. It has been known for some time that numerous methods of polymerization and emulsion copolymerization of various ethylenic monomers, among them vinyl esters and acrylate and methacrylate esters. In general, to prepare a latex derived from a vinyl ester and one or more other monomers copolymerizable therewith, it is first introduced into a reactor an aqueous phase containing water, a surfactant, a buffer, a catalyst or a free radical type catalyst system and usually a protective colloid such as polyvinyl alcohol. Subsequently, the monomers are introduced into the reactor, either in streamed streams, the mixture being carried out in the reactor, either in the mixing state, or at once, batchwise, then heated to the polymerization temperature and The polymerization is allowed to proceed substantially to completion with constant stirring. The resulting latex is cooled, filtered and can be used in many applications, for example as paints and other surface coating compositions. , adhesive

  and textile treatment agents.

  Emulsion polymerization processes having one or more aspects of the copolymer latex process described above are described in US Pat. Nos. 2,496,384, 2,520,959, 3,248,356, 3,404,114, 3,423,353, US Pat. Nos. 3,483,171, 3,804,881 and 4,039,500. In particular US Pat. No. 3,423,353 discloses latexes derived from vinyl acetate and one or more comonomers including alkyl acrylates and methacrylates such as methyl acrylates. , methyl, propyl, butyl isobutyl and 2-ethylhexyl, methacrylates of methyl, ethyl and propyl-n, and it is said that the latex has a higher solids content than when conventional emulsion polymerization techniques are used, while having reduced viscosities and improved stability to freezing and thawing. The latices are prepared in the conventional manner and, once the polymerization is substantially complete, a relatively large amount of catalyst or polymerization initiator is added to the emulsion to decrease the viscosity and increase the particle size. It is said in the cited patent that this post-catalyst addition probably results in some degradation of the surfactant and the protective colloid containing ether chains, decreasing their molecular weight by an oxidation mechanism which involves a breakdown of the bonds. ether. it is believed that this oxidative degradation decreases the effectiveness of the surfactant and the protective colloid, resulting in some agglomeration of particles. It appears that the larger average particle size of the emulsion is also responsible for lowering the

the viscosity.

  It has now been discovered that latexes derived from vinyl esters and acrylate and / or methacrylate esters and having a high solids content and low viscosity can be easily and conveniently prepared by virtue of the polymerization itself. , which makes it possible to dispense with other handling steps such as the after-the-fact addition of relatively large quantities of catalyst such as

  in US Patent 3,423,353 already cited.

  The addition of catalyst afterwards to the latices prepared by the method of the present invention has no noticeable effect on the viscosity of the products, demonstrating that the viscosity of the latexes obtained is in the major

  part fixed during the polymerization.

  According to the invention, high solids low viscosity copolymer latexes are prepared from (a) at least one monomeric vinyl ester representing about 50-95% of the total weight of the monomers introduced and (b) ) at least one monomer selected from the acrylate and methacrylate esters and representing the remainder of the total monomers y in a first stage, polymerizes a significant part of the total vinyl monomer ester, for example at least about 10% by weight and preferably at least about 50% by weight thereof, with about 0-50% of the total weight of acrylate and / or methacrylate ester monomer, in an aqueous emulsion medium containing a polymerization catalyst and then the remaining vinyl ester monomer is polymerized in a second stage with the rest of the monomeric acrylate and / or methacrylate ester in the reaction medium containing a supplement.

  if necessary, the polymerisation continues.

  practically until completion. Preferably, during the first stage, the ratio of the vinyl ester to the acrylate and / or methacrylate is greater than about 4.5, until about 40 to 60% of the total monomers have been introduced and, during the second addition, the ratio of the monomeric vinyl ester to the acrylate and / or methacrylate monomer is less than about 4.5, until all the rest of the monomers have been introduced into the polymerization reactor. It can be added, at the beginning of the polymerization process or during it,

  one or more other copolymer ethylenic monomers

  sands with monomers (a) and (b) and present

  maximum of 5% of the total weight of monomers introduced.

  It may be advantageous to initially polymerize a small amount, about 5%, of the total vinyl ester monomer in the reactor before the start of the reaction.

first stage polymerization.

  The process according to the invention envisages the use of known and conventional surfactants, buffers, collars, protectors, catalysts, etc. in customary quantities, and it is possible to operate in the apparatuses previously used.

  for emulsion polymerization.

  Typically, the latices obtained according to the invention have a solids content of about 60 to 70% by weight and even more. The viscosity of the high solids latexes according to the invention is generally only a fraction of that of latex prepared in the usual manner, that is by simultaneous addition of the monomers, and usually it does not exceed This is the Brookfield viscosity (RVF, axis No. 1) at 2 rpm. Latexes having a high equivalent solids content, prepared in the conventional manner, attain a Brookfield viscosity (RVF, axis No. 5) at 2 rpm of 50 Pa.s. Due to the combination of a high solids content and a low viscosity, the latices of the invention are especially useful for the preparation of paints and other coatings.

of surface.

  The latices prepared according to the process of the invention contain copolymers of at least one vinyl ester

  and at least one acrylate and / or methacrylate ester. Gene-

  When these copolymers are prepared,

  about 50 to 95% and preferably about 65 to about% by weight of vinyl ester with about 5 to 50% and, preferably, about 15 to 35% by weight of acrylate and / or methacrylate ester, on the total weight of the monomers present. Among the vinyl esters which can be advantageously used in the invention are the formate, the

  propionate, butyrate and vinyl chloroacetate.

  Vinyl acetate is especially preferred in

  the invention. Examples of acrylate and methacrylate esters

  Examples which can advantageously be used in the invention are methyl, ethyl and propyl acrylates.

  butyl, dmisobutyl, secondary butyl, amyl, iso-

  amyl, hexyl, 2-ethylhexyl, octyl, 3,5,5-tri-

  methylhexyl, decyl, dodecyl, cetyl, octadecyl, cyclohexyl and phenyl, methacrylates of methyl, ethyl, propyl-n, amyl-n, isoamyl, hexyl,

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  2-ethylbutyl, octyl, 3,5,5-trimethylhexyl, decyl, cyclohexyl, norbornenyl, benzyl, phenyl and neopentyl. It has been found that the acrylate

  butyl is especially advantageous in the invention.

  As stated above, at most 5% of the total weight of the monomers present may be interpolymerized with one or more additional ethylenic monomers, for example ethylene, propylene, butene (1), butene (2 ), lisobutylene, pentene (1), 2-methylbutene (2), hexene (1), 4-methylpentene (1), 3,3-dimethylbutene (1),

  2,4,4-trimethylpentene (1), 6-ethylhexene (1), hepthe-

  ne (1), octene (1), decene (1), dodecene (1), allene, butadiene, isoprene, chloroprene, hexadiene (1,5), hexatriene (1,2,5), divinylacetylene, cyclopentadiene, dicyclopentadiene, norbornene, norbornadiene,

  methylnorbornene, cyclohexene, styrene, (- chloro)

  styrene, o-methylstyrene, allylbanzene, phenylacetyl

  1-phenyl butadiene (1,3), vinyl naphthalene, 4-methylstyrene, 2,4-dimethylstyrene, 3-ethylstyrene,

  2,5-diethylstyrene, 2-methoxystyrene, 4-methoxy-3-

  methylstyrene, 4-chlorostyrene, 3,4-dixthyl-o-methyl-

  styrene, 3-bromo-4-methyl-v-methylstyrene, 2,5-di-

  chlorostyrene, 4-fluorostyrene, 3-iodostyrene, 4-cyanostyrene, 4-vinylbenzotetyl, 4-acetoxyetyrene,

  4-vinylbenzyl alcohol, 3-hydroxystyrene, 14-di-

  hydroxystyrene, 3-nitrostyrene, 2-aminostyrene. the

  4-N, N-dimethylaminostyrene, 4-phenylstyrene, 4-chloro-

  1-vinyl naphthalene, acrylic acid, methacrylic acid, acrolein, methacrolein, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-methyl methacrylamide, chloroacrylic acid, acid

  methylchloracrylic acid, chloracetonitrile, ethacryloni-

  trile, N-phenyl-acrylamide, 1,4-diethyl acrylamide, P-cyclohexyl acrylamide, vinyl chloride, vinylidene chloride, vinylidene cyanide, vinyl fluoride, vinylidene fluoride, -

  trichloroethene, methyl-vinylketone, methyl-isopropyl

  penylketone, phenylketone, methyl-o (-chlorovinylketone,

  ethyl vinyl ketone, divinyl ketone, hydroxymethyl

  vinyl ketone, chloromethyl vinyl ketone, allylidene diacetate, methyl vinyl ether, isopropyl ether,

  vinyl ether, butylvinyl ether, 2-ethylhexyl ether,

  vinyl ether, 2-methoxyethyl vinyl ether, 2-chloro ether,

  ethylene vinyl, methoxyethoxyethylvinyl ether, hydroxyethylvinyl ether, aminoethylvinyl ether, omethylvinylmethyl ether, divinyl ether, divinyl ether of ethylene glycol, diethylene glycol or triethanolamine, cyclohexyl vinyl ether, benzyl vinyl ether, phenethyl vinyl ether, cresyl vinyl ether, hydroxy phenyl vinyl ether, chlorophenyl vinyl ether, naphthyl vinyl ether, dimethyl maleate, diethyl maleate, bis (2-ethylhexyl) maleate, maleic anhydride, dimethyl fumarate, dipropyl fumarate, vinyl and ethyl sulphide, divinyl sulphide, sulphide vinyl and p-tolyl, divinylsulfone, vinylethylsulfone, vinylethylsulfoxide, vinylsulfonic acid,

  vinylsulfonate, vinylsulfonamide, vinyl

  bensamide, vinylpyridine, N-vinylpyrrolidone, N-vinylcarbazole, N- (vinylbenzyl) -pyrrolidine,

  N- (vinylbenzyl) -piperidine, 1-vinylpyrene, 2-isopropyl

  penylfuran, 2-vinyl-dibenzofuran, 2-methyl-5-

  vinylpyridine, 3-isopropenylpyridine, 2-vinylpiperidine,

  2-vinylquinoline, 2-vinylbenzoxazole, 4-methyl-5-

  vinylthiazole, vinylthiophene, 2-isopropenylthiophene, indene, coumarone, 1-chloroethyl sulfide and vinyl, vinyl and 2-ethoxyethyl sulfide, vinyl and phenyl sulfide, vinyl sulfide and naphthyl )

  allylmercaptans, divinylsulfoxide, vinyl-phenyl-

  sulfoxide, vinyl-chlorophenylsulfoxide, vinylsulfonate methyl, vinylsulfanilide etc ... It is possible to introduce into the reactor part or all of these optional monomers at the beginning of the polymerization process or during this process. In this case, these monomers can be used at a concentration of less than about 2%

  by weight to avoid excessive coagulation.

  Surfactants contemplated by the invention include all known and conventional surfactants and emulsifiers, mainly nonionic and anionic

  their mixtures, previously used in the copolymer-

  emulsion of vinyl acetate and ethylene,

  nonionic surfactants being especially preferred.

  Among the nonionic surfactants with which we have had good results are * Igepalsm (GoA.F.),

  Tweens # (Atlas Chemical) and #Pluronices (BASF Wyandotte).

  #Igepals are the members of a homologous series of alkylphenoxypoly (ethyleneoxy) ethanols, which may be represented by the general formula ## STR5 ## wherein R represents an alkyl radical and a denotes the number of moles of ethylene oxide used; they include alkylphenoxypoly (ethyleneoxy) ethanols, the alkyl groups of which contain about 7 to 18 carbon atoms inclusively and which comprise from about 4 to

  ethylene oxide units, such as heptylphenoxypoly- (ethyl-

  leneoxy) ethanols, nonylphenoxypoly (ethyleneoxy)

  ethanols and dodecylphenoxypoly (ethyleneoxy) ethanols, the sodium or ammonium salts of the sulfate esters of these

  alkylphenoxypoly (ethyleneoxy) -thanols, the alkylpolyphenyl

  (6-ethyleneoxy) ethanols, alkylpoly (propyleneoxy) ethanol

  octylphenoxyethoxyethyl dimethyl

  benzylammonium, the tertiododecyl thioether of polyethylene

  glycol. NTweens # are polyoxyalkylene derivatives of fatty acid partial esters and sorbitol anhydride, for example the polyoxyalkylene derivatives of sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate. sorbitan monooleate and sorbitan trioleate. #Pluronics are condensation products of ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylneglycol etc ... Other suitable nonionic surfactants that can serve here are derivatives ethylene oxide and long-chain fatty alcohols such as octyl, dodecyl, lauryl or cetyl alcohols. Anionic surfactants that can be used herein include alkali sulfates derived from C12 & C14 alcohols such as sodium lauryl sulfate and salts.

  alkalis of alkylbenzenesulphonic acids and alkyltoluene-

  sulfonates containing aliphatic side chains of about 10 & 15 carbon atoms, etc. The surfactant is generally used at about 3 to 5% and preferably about 3.5 to 4.5% the total weight of

monomers present.

  A protective colloid is generally incorporated into the aqueous emulsions of the invention. Known and conventional protectors such as partially and completely hydrolysed polyvinyl alcohols,

  cellulose, for example hydroxymethylcellulose, hydroxypropyl

  ethylcellulose, ethyl-hydroxyethylcellulose and ethoxylated starch derivatives, natural and synthetic gums, for example gum tragacanth and gum arabic, polyacrylic acid, methyl vinyl ether / maleic anhydride copolymer and polyvinylpyrrolidone are suitable and use in the context of the invention, preferably from about 0.1 to 2% of the weight of the emulsion. The

  polyvinylpyrrolidone and the polyvinyl alcohols

  hydrolysed are especially advantageous for

use in the invention.

  The catalysts used in the copolytic reaction

  Merification are all conventional free radical polymerization catalysts previously used for the preparation of copolymer latexes and include inorganic peroxides such as hydrogen peroxide, sodium perchlorate and sodium perborate, inorganic persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate and reducing agents such as sodium hydrogen sulfite. The catalyst (including the reductant optionally used as cocatalyst) is generally used in an amount of about 0.1 to 1% of the total weight of the comonomers. The catalyst may be added to the reaction medium at one time or may be divided into two or more portions which are added to the medium at each addition of monomer or during one

  polymerization processes or both.

  An alkaline buffer can be added to the aqueous system

  such as sodium bicarbonate, potassium bicarbonate

  sium, sodium acetate etc ... to maintain the pH at

  at the desired level. The amount of buffer generally represents

  approximately 0.01 to 0.5% of the weight of the monomers.

  The way to introduce the monomers into the reactor is not critical. The monomers may be added to the reaction medium in a constant stream, dropwise or periodically in portions, the vinyl ester and the acrylate / methacrylate ester may be mixed before being introduced into the reactor or may be introduced. in the form of separate currents. Advantageously, the monomers are added in a constant stream at times ranging from about 1 to 5 hours, and preferably about 2 to 3 hours. We can choose the reaction temperature at the levels

  previously applied in emulsion polymerization.

  For both polymerization processes, the temperature may range from about 0 ° C to about 100 ° C, preferably from room temperature to about 80 ° C, the medium being constantly stirred or agitated otherwise substantially complete completion of the polymerization is usually indicated by the fact that the free monomer content of

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  the latex emulsion is less than about 1% and

  lower preference & about 0.5%.

  In the following examples, where conventional equipment is used and the parts are by weight, Examples 1 to 11 illustrate the copolymer latices and the emulsion polymerization process of the invention, while Comparative Examples 1A and 1B are given to illustrate prior latices and polymerization processes. Constituents of environments

  emulsions used in the examples are identified below.

  After s Constituting Triton X-405 "Triton O8-9" "Tamol 850" Sipon ESY "Mrnomer X-980" "Butyl Carbitola" Plasticizer Surfactant Natrosol 250.R '"Trycol PO-407" "CMP Acetate" Source Rohm and Haas Company Rohm and Hass Company Rohm and Hass Company Alcolac, Inc. Rohm and Hass Company Carbide Corporation Cincinnati Corporation Milacron Chemicals, Inc. Hercules, Inc. Emery Industries Troy Chemical Corporation

Octylphenoxy poly-

  (Ethyleneoxy) ethanol Ester phosphate, acid form Sodium salt of polymeric carboxylic acid

Sodium salt of sulphate

lauryl ether fats

  Trimethylolpropane trimethylolpropane, sodium lauryl sulphate Diethylene glycol monobutyl ether Hydroxyethylcellulose Octylphenol condensed with 40 ethylene oxide units

Preparation of

  vator containing 10% by weight of acetate

chlorométhoxypropyl-

mercuric

EXAMPLE 1

  In a 2000 resin tank agitator, reflux condenser, ml equipped with a funnel

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  addition and a thermometer, the following solutions are used: (a) Deionized water 200 parts Polyvinylpyrrolidone 2.5 parts (b) Deionized water 220 parts Triton X-405 "40 parts #Triton QS-9" 12.5 Sodium hydroxide to pH 10 and then 40 parts of sodium acetate. The reactor is heated in a water bath and, at 60 ° C., 1.65 parts of ammonium persulfate in 10 parts of water are added all at once. At 72 ° C., 320 parts of vinyl acetate are started and then continued at 78 ° C. to 80 ° C. in the course of about 65 minutes. Next, a mixture of 360 parts of vinyl acetate and 150 parts of vinyl acrylate is added over a period of about 120 minutes. When all the monomer mixture has been added, 0.2 part of ammonium persulfate is introduced and the mixture is kept at 80.degree. C. more for complete concentration of the monomers. Cooled at room temperature, the copolymer latex has a content in solids of 65.2% and a Brookfield viscosity (RVF, axis n 2) of 2.7 Pa.s &

  2 revolutions / min and 0.8 Pa.s & 20 revolutions / Mn.

  COMPARATIVE EXAMPLE 1 In this example, which illustrates the prior art, the monomers are added at one time. The protective colloid is omitted, in order to prevent the finished latex from

an unmanageable viscosity.

  In a 2000 ml resin flask equipped as in Example 1, deionized water was added 450 parts Triton X-405 37 parts Triton QS-9 25 parts Sodium hydroxide to pH 10 70 C using a water bath & temperature set and 1.65 parts of ammonium persulfate in 10 parts of water are added all at once, then a mixture of 720 parts of vinyl acetate and

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  parts of butyl acrylate in the space of about minutes. The reaction temperature rises rapidly to 80 ° C and is maintained at this level during the addition of the monomers. After addition of the monomers, 0.3 part of ammonium persulfate is added in 10 parts of water. The temperature is maintained at 80 ° C. for one more hour and then cooled to room temperature. The copolymer latex has a solids content of 64.6% and a Brookfield viscosity (RVF, axis No. 5) of 50 Pa.s at 2 rpm and 12.1 Pa.s at 20 rpm. This viscosity is absolutely excessive for a good composition of

latex paint.

  COMPARATIVE EXAMPLE 1 This example also illustrates the prior art process for the simultaneous copolymerization of all monomers. The following mixture is prepared in a resin flask equipped as in Example 1: Vinyl acetate 718 g Butyl acrylate 147 g Deionized water 470 g Triton X-405 37 g Triton Q8-9 25 NaOH 2.5 g (NH) 28208 1.65 + 0.3 g The surfactants are dissolved in water and the pH is adjusted

  of the solution & 11.6 with NaOH (dissolved in H2O).

  The solution is introduced into the reactor and heated to 0 ° C. At this stage, the first portion of (NH4) 2S208 is added and the addition of the monomer mixture is begun. The addition is rapid during the first 2 hours of polymerization (about 80% of the monomer is added during this time). During the last half-hour, the rate of addition of the monomers is decreased (the latex becomes rather viscous). When the addition of monomer is complete, the second part of the catalyst (dissolved in

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  500ml H20). Then, the mixture is kept at about

  C for about 1 hour. The polymerization temperature

  The latex obtained has a good appearance, but it is very viscous and contains no gel, but it contains many air bubbles. It is observed that the latex has the following properties s Solids s 64.6% Brookfield Viscosity (axis n 5) RPM 2 4 10 20 Reading 25 32.5 46 60.5 Factor 2000 1o00 400 200 mPa.s 50000 32500 13400 12100 The product spread on a glass plate is transparent,

but contains many bubbles.

  While the latex of Example 1 is very useful in paints, it is easy to see that the latexes obtained by the prior method of simultaneous copolymerization are not suitable for coatings of

surface coating.

2NMPLE2

  In the resin flask of Example 1 is introduced X Deionized water 420 parts "Triton X-405m 40 parts" Sipon Esy "20 parts Polyvinylpyrrolidone 5 parts Sodium acetate 3.2 parts Vinyl acetate 40 parts Ammonium persulfate 1 After 65 parts in Water 10 parts A 72 C, 320 parts of vinyl acetate are added, then it is continued between 78 and 80 ° C in the space of about 65 minutes. about 120 minutes a mixture of 360 parts of vinyl acetate and 150 parts of butyl acrylate.When all the monomer mixture was added, 0.2 part was added.

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  of ammonium persulfate and the mixture is maintained

  minutes longer at 80 ° C to consume the remaining monomers.

  Once cooled to room temperature, it is found that the latex contains 64.8% solids and has a Brookfield viscosity (RVF, axis n 1) of 0.55 Pa.s at 2 rpm and

0.28 Pa.s at 20 rpm.

MXEMLE 3

  In the resin flask of Example 1 are: Deionized water 335 parts "Triton X-405" 50 parts "Sipon Esyn 22 parts Polyvinylpyrrolidone 5 parts Sodium acetate 3.2 parts Vinyl acetate 40 parts After addition, at 60 ° C., 1.65 parts of ammonium persulfate in 10 parts of water, 320 parts of vinyl acetate are added in the course of 75 minutes between 78 ° C. and then a solution of 0.1 part of ammonium persulfate in 5 parts of water, then a mixture of 360 parts of vinyl acetate and 150 parts of

butyl in 135 minutes.

  To complete the polymerization, intermittently

  during the next hour 0.5 part of ammonium persulfate. The latex mixture, cooled to room temperature, contains 69.5% solids and has a Brookfield viscosity (RVF, axis n 2) of 1.2 Pa.s at 2 rpm and

0.57 Pa.s at 20 rpm.

EXAMPLE 4

  Example 2 is repeated except that 8.7 parts of acrylic acid are included in the second monomer addition, that is, a mixture of vinyl acetate and acrylate. butyl. The latex contains 65.8% solids and has a Brookfield viscosity (RVF, axis n 2) of 2.6 Pa.s.

  at 2 rpm and 0.9 Pa.s at 20 rpm.

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EXAMPLE 5

  To verify the qualities of the high solids latexes of the invention, normal latex paints are prepared starting from the copolymer latices of Example 1 (Part A) and Example 2 (Part B). Using normal paintmaking processes, a pigment paste is prepared and then diluted with water latex and thickener solution to provide viscosities for application to the brush. The viscosity of Part A of the paint is 77 Krebs and the Part B of the paint is 84 Krebs. Both paintings are spread on a Leneta contrast chart using a 152 μm squeegee. We examine the dried layers and find them

  very satisfactory, without coagulation of latex or agglomeration of pigment. Masking power is considered to be entirely

  acceptable. The brushes are applied to compressed cardboard, both in one layer and in two layers, with one night of drying between layers. Both paintings are applied without encountering any difficulty. The viscosity is checked after one month to determine the storage time and is found to be excellent. That of Part A paint only increased by 2 Krebs units and that of the painting of

Part B remained unchanged.

EXAMPLE 6

  In a resin flask such as that of Example 1, 8 vinyl acetate 720 g butyl acrylate 150 g deionized water 455 g Triton X-405 "40 g" 8ipon Esy "20 g Polyvinylpyrrolidone 5 g

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  Na2CCH3 3.2 g (NH4) 28208 165 + 0.1 + 0.2 g The surfactants, the polyvinylpyrrolidone and the buffer are dissolved in cold water * The solution plus 40 g of sodium acetate is added to the solution. reactor and heated. At 60 ° C., the first part of the catalyst is added and, when the reaction temperature reaches 72 ° C., the first part of the monomer (320 g of vinyl acetate) is begun. During this addition (65 minutes), the polymerization temperature is maintained between 76 and 78 ° C with cooling. As soon as the addition of the first part has been completed, the second part (360 g of vinyl acetate mixed with 150 g of butyl acrylate) is added.

  and a slight heating is necessary to maintain it.

  The addition is a little slower to prevent the accumulation in the reactor of free monomer, which could form foam. Catalyst is added when the addition has started and also when it is complete. When monomer addition is complete (160 minutes), the temperature rises to 84 ° C. The latex obtained has a good appearance. Very little grain remains on the filter after filtration

latex.

  It is observed that the latex has the following properties s Solids s 64.8% Brookfield Viscosity (axis n 1) RPM 2 4 10 20 Reading 11 185 35 56 Factor 50 25 10 5 mPa.s 550 462 360 280 A layer of latex spread on glass looks good i latex is a bit cloudy but does not contain

neither gel nor bubbles.

EXAMPLE 7

  In a resin balloon as in Example 1,

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  Vinyl acetate 740 g Butyl acrylate 157 g Deionized water 455 g Triton X-405 "40 g" Triton Os-9 "12.5 g Polyvinylpyrrolidone 3.5 g NaOH 1.2 g (NH4) 2208 1 The solution of polyvinylpyrrolidone and surfactant is prepared and the pH is adjusted as in the previous examples The first stage of monomer addition (55 minutes) is carried out in portions of 40 and 320 g of vinyl acetate The second stage of addition (140 minutes) comprises a mixture of 380 g of vinyl acetate and 157 g of butyl acrylate, although the second monomer addition is slightly increased to compensate for the possible losses. in solids indicates that it is not necessary.When the second stage of addition is started, the reaction temperature is lowered in the usual way & at this moment, an additional 0.1 g of catalyst is added but without much result The reaction temperature is then adjusted by acting on the monomer flow and the temperature. At the beginning of the second stage, the temperature drops to 75 ° C, but for the most part it is 78 to 80 ° C. At the end of the monomer addition, 0.2 g of (NH4) 2S208. The temperature rises to 83 C. No foam is observed. The latex contains the usual amount of grain, but once removed by filtration, the product has an acceptable appearance. It is observed that the latex has the following properties:

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  Solids 65.7% Brookfield Viscosity (axis n 2) RPM 2 4 10 20 Reading 8 12 20 29 Factor 200 100 40 20 mPa.s 1600 1200 800 580 A layer of latex spread on glass gives a slight haze, but the latex still has a good overall appearance.

EXAMPLE 8

  The following interior paint compositions are prepared with the copolymer latices of Examples 6 and 4 (Figure 5) in a Cowles dissolver. Water 516 g Acetate CMP 1 g Ethylene glycol 96 g Butylcarbitol 68 g E2CO3 4 g Tamol 850 8 g Plasticizing surfactant 12 g #Natrosol 250 MRI 600 g TiO2 600 g Clay calcine 240 g Kieselguhr 1000 g Total 3145 g AB paint Pigment paste 394 g 394 g

Latex of Example 6 80.5 g -

  Latex of Example 7 - 80 # 5 g Water 93 g 95 g Natrosol 250 MR 'at 15% 15 g 13 g Units Klebs 84 77

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  Paint layers A and B are spread on Leneta contrast diagrams using a 152 μm squeegee. The paints are applied by painting on compressed cardboard, both in one layer and in two layers, with one night of drying between layers. The cardboard plate is capped with the diluted latex of Example 6 prior to application of the paint. The layers of spreading and painting are satisfactory. There is no coagulation of latex or agglomeration of pigment,

  in neither painting.

  Paint Viscos A 84 units Klebs Paint B 79 units Klebs

EXAMPLE 9

  In a resin flask such as that of Example 1, vinyl acetate 735 g butyl acrylate 150 g deionized water 360 g Triton X-4054 50 g Sipon Esy, 22 g polyvinylpyrrolidone 5 g Nao2ccH33

2 3 3

  (NH4) 2S208 1.65 + 0.1 + 10.5 g The first stage of monomer addition (360 g of vinyl acetate is completed within 75 minutes) and when about 130 ml of the monomer mixture of the second stage of addition (360 g of mixed vinyl acetate & 150 g of butyl acrylate), the final addition of catalyst (0.5 g of ammonium sulfate in 20 ml of H 2 O). The latex obtained has a good appearance, while containing the usual amount of grains that can be easily removed by filtration or by similar means. It is observed that the latex has the following properties s - Solids s 69.3 - 0.5% Brookfield Viscosity (axis n 2) RPM 2 4 10 20 Reading 6 9.5 17.5 28.5 Factor 200 100 40 20 MPa.s 1200 950 700 570 A layer of the latex spread on glass several days after the preparation of the product gives a very good

  gel-free coating and bubbles.

EXAMPLE 10

  In a resin flask as in Example 2, vinyl acetate (720 g) butyl acrylate (150 g) acrylic acid 8.7 g deionized water (435 g) Triton X-405 (40 g) #Sipon Esyu (20 g) Polyvinylpyrrolidone 5 g NaO2CCH3 32 g (M4) 2S2O8 1.65 + 0.2 g The polymerization is started as in Example 6, but 360 g of vinyl acetate are added in the first stage (within 65 minutes ) and adding, at the second stage, 360 g of vinyl acetate mixed with butyl acrylate and 8.7 g of acrylic acid (within 160 minutes). During the second stage, the rate of addition and the temperature of the bath are regulated so that the reaction temperature is always close to the temperature of the bath (78 to 80 ° C.). No catalyst addition is made at the beginning of the second addition stage. The final catalyst addition is begun about 5 minutes after completion of the addition and is about 15 minutes. Once the addition of

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  monomers complete, the reaction temperature is for about 40 minutes slightly greater than or equal to the

  bath temperature. About 15 minutes after the temperature

  As a result, reaction temperature began to drop, the reactor contents were cooled to room temperature. The latex obtained has no odor of free monomer and has a good appearance, almost free of grains. Screening the

  monomer is very easy to achieve.

  It is observed that the latex has the following properties: Solids s 65.8% Brookfield Viscosity (axis nO 2) RPM 2 4 10 20 Reading 13 19 31 45 Factor 200 100 40 20 mPa.s 2600 1900 1240 900 Layers of latex spread on glass give a gel-free coating and bubbles having a very

good overall appearance.

EXAMPLE 11

  This example relates to obtaining a latex of high viscosity, the polymerization being conducted in two successive stages, but with polymerization of a mixture of vinyl acetate and butyl acrylate at each stage of monomer addition. In a resin flask as in Example 1, X Vinyl acetate 700 g Butyl acrylate 150 g Monomer X-980 "26 g Acrylic acid 8.7 g Deionized water 450 g # Emersal 6400" 20 g " Trycol PO-407 "40 g Polyvinylpyrrolidone 2 g NaO2CCH3 4g (NH4) 24208 16 g

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  To facilitate the dissolution of the "Emersal 6400",

  add a little water to the surfactant, then heat up.

  Monomer blends are prepared as follows: Initial stage 1 stage, 2nd stage stage, vinyl acetate 40 310 350 Butyl acrylate O 65 85 "Monomer X-980" O 13 13 Acrylic acid O 4.35 4.35 The first monomer addition stage is carried out in minutes and a second monomer addition stage is carried out in 85 minutes. No catalyst is added

  additional to the completion of monomer additions.

  The resulting latex, which contains the usual small amount of grain, has a good appearance and is only present

a trace of dilatancy.

  It is observed that the latex has the following properties s Solids s 65.2% Brookfield Viscosity (axis n 3) RPM 2 4 10 20 Reading 16.5 21 30 39 Factor 500 250 100 50 mPaos 8250 5250 3000 1950 A layer of this latex spread on glass has good

  appearance, with only a slight disturbance.

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Claims (13)

  A process for the preparation of high viscosity low viscosity copolymer latexes starting from at least one vinyl monomer ester accounting for about 50 to 95% of the total monomers introduced and at least   a monomer selected from acrylate or methacrylate esters   lates and representing the rest of the monomers introduced, characterized in that in a first stage, a significant part of the total vinyl ester is polymerized and O to about 50% of the total weight of acrylate ester and / or methacrylate in an aqueous emulsion medium containing a polymerization catalyst and then, in a second stage, the remainder of the vinyl ester and the remainder of the acrylate and / or methacrylate ester are polymerized in the reaction medium containing additional catalyst, if necessary, the polymerization continuing practically until completion. 2. A process according to claim 1, characterized in that it is polymerized in the first stage at least   10% of the total weight of vinyl ester.   3. A process according to claim 1, characterized in that it polymerizes in the first stage at least 25% total weight of vinyl ester.   4. Method according to one of claims 1 to 3,   characterized by the fact that the vinyl ester is acetate of vinyl.   5. Method according to one of claims 1 to 4,   characterized in that the acrylate ester is acrylate butyl.   6. A process according to one of claims 1 to 5,   characterized in that a total of about 65 to 85% by weight of vinyl ester is polymerized with a total of about 35 to 15% by weight of acrylate and / or methacrylate ester.   7. A process according to one of claims 1 to 6,   characterized by the fact that one initially adds to - 24 -   reaction medium less than about 60% of the total weight of vinyl ester present and that the remainder is added   successively with the acrylate and / or methacrylate ester.   8.- Method according to one of claims i to 7,   characterized by including a surfactant   consisting of at least one nonionic or anionic surfactant.   9. A process according to one of claims 1 to 8,   characterized in that the reaction medium contains in addition a protective collofde.   10.- Method according to one of claims 1 to 9,   characterized in that the reaction medium contains in addition an alkaline buffer.   11. A process according to one of claims 1 to 10,   characterized in that the remainder of the total vinyl ester is added in portions at the second stage together with the remainder of the acrylate and / or methacrylate ester, the ratio of the vinyl ester to the acrylate and / or methacrylate ester in the first added portion being greater than about 4.5, until about 40 to 60% of the total monomers have been added, and then in a second addition portion the ratio of vinyl ester to acrylate and / or methacrylate is less than about 4.5, until added to the reactor the rest of the monomers.   12. Process according to one of claims 1 to 11,   characterized in that at the beginning of the polymer is added   during or during the process, one or more ethylenic monomers copolymerizable with the two kinds of monomers mentioned and representing at most 5% of the total weight of monomers.   13. Latex prepared by the process according to one of Claims 1 to 12.