CA1185033A

CA1185033A - Preparation of high solids copolymer latices with low viscosity

Info

Publication number: CA1185033A
Application number: CA000371121A
Authority: CA
Inventors: Manfred Heimberg
Original assignee: National Destillers and Chemical Corp
Current assignee: Equistar Chemicals LP
Priority date: 1980-03-10
Filing date: 1981-02-18
Publication date: 1985-04-02
Also published as: BR8101357A; NL8101158A; FR2477555A1; BE887849A; NO810785L; GB2071122B; DE3109085A1; GB2071122A; IT8120208A0; JPS56141311A; IT1195273B

Abstract

ABSTRACT OF THE DISCLOSURE
High solids, low viscosity copolymer latices especially useful when formulated as surface coatings are prepared from (a) at least one vinyl ester monomer in an amount representing from about 50 weight percent to about 95 weight percent of total monomer charge and (b) at least one acrylate ester and/or methacrylate ester monomer representing the balance of the total monomer charge. The latices are prepared in a multi-stage polymerization sequence in which a significant portion of the total vinyl ester monomer charge is polymerized together with from 0 to about 50 weight percent of the total acrylate ester and/or methacrylate ester monomer in the initial stage in an aqueous emulsion reaction medium containing a suitable catalyst and thereafter, the remaining portion of the total vinyl ester monomer charge together with the remaining portion of the acrylate ester and/or methacrylate ester monomer charge is polymerized in the reaction medium containing additional catalyst if needed and polymerization is continued substantially to completion.

Description

1 PREPA~TION OF HIGH SOLIDS COPOLYMER LATICES WITH LOW
VISCOSITY

This invention relates to the field of copolymer 5 latices and, more particularly, to such latices having high solids content and low viscosity and bein~ prepared from a mixture of copolymerization monomers inclu~ing a vinyl ester and an acrylate or methacrylate ester.
Numerous procedures for the emulsion polymerization 10 and copolymerization of various ethylenically unsaturated monomers, vinyl esters, acrylate esters and methacrylate esters among them, have been known for some time. In general, a latex derived from a vinyl ester and one or more other monomers copolymerizable therewith is prepared 15 by first charging an aqueous phase containing water, surface active agent, buffer, catalyst or catalyst system of the free radical type and usually a protective colloid such as polyvinyl alcohol (P~A), to a reactor. The monomers are thereafter charged to the reactor either as separate 20 streams with mixing occurring in the reactor or in admixture, and either all at once or incrementally, and following heating to polymerization temperature, - polymerization is thereafter permitted to proceed, aceompanied by eonstant agitation, substantially to 25 completion. The resulting latex is eooled and filtered and can be used in many applications, e.g., as paints and other surface coating compositions, adhesives and textile treating agents.

3o ,.~., S~33 1 Emulsion pol~merization procedures featuring one or more aspects of the aforedescribed method o~ preparing copolymer latices are descrlbed in U.S. Patent Nos.

2,496,384; 2,520,959; 3,248,356; 3,404,114; 3,423,353;
5 3,483,171; 3,804,881; and, 4, o39,500. u . s . Patent No.

3,423,353 to Levine et al. ln particular describes latlces obtained from vlnyl acetate and one or more other comonomers including al~yl acrylates and methacrylates such as methyl acrylate, ethyl acr~late~ propyl acrylate, butyl acrylate, 10 isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate and n-propyl methacrylate, the latices being said to possess higher solids contents than obtainable using conventional emulsion polymeri2ation techni~ues, while at the same time having reduced viscosities and lmproved 15 freeze-thaw stability. The latices are prepared in the conventional manner and once polymerization is substantially complete, a rel~tively large amoun~ of water-soluble polymerization catalyst or intiator is added to the emulsion to reducs viscosity and increase particle size.
20 Xt is speculated by patentees that this post-addition of catalyst results in some degradat~on of th~ surface active agen'G and the ether linkage-containing protective colloid when used, reducing their molecular weights by an oxidative mechanism which in~rolves rupture oî the ether linkages.
25 This oxidative degradation is thought to reduce the effectiveness of the surface actl~e agent and protecti~e colloid resulting in some agglomeration o~ partlcles. The larger average particle size o~ the emulsion is believed to be also responsible for the reduction in viscosity.

50~3 It has now been discovered that latices derived ~ro~ vinyl esters and acrylate and/or methacrylate esters having high solids contents and low viscosity can be 5 readily and conveniently prepared as a result of the polymerization itsel~, thus dispensing with the need ~or ~urther manipulative steps ~uch as the post-addition of relatively large quantities of catalyst o~ U.SI Patent No. 3,423,353 to Levine et al.
The post-addition of catalyst to latices prepared by the process of this invention has no significant ef~ect on the viscosities o~ the products~
demonstrating that the viscosities o~ the latices herein are for the most part ~ixed during polymerizationr In accordance with the present invention, high solids9 low viscosity copolymer latices are prepared from (a) at least one vinyl ester monomer in an amount representing from about 50 weight percent to qbout 95 weight percent o~
total monomer chargeg and (b) at least one monomer selected 20~rom the group consisting o~ acrylate ester monomer and methacrylate ester monomer representing the balance of the total monomer charge; which comprises, polymerizing in a first stage, a significant portion of the total vinyl ester monomer, e.g., at least about 10 weight percent and pre~erably 25at least about 50 weight percent of the total vinyl ester monomer~
together with from 0 to about ~0 weight percent of the total acrylate and/or methacrylate ester monomer in an aqueous emulsion reaction medium containing a polymerizatlon catalyst~ and thereafte polymerizing in a second~stage the remaining portion o~ the 30total vinyl ester monomer charge together with the remaining amount of the acrylate and/or methacrylate ester monomer in the reaction medium containing additional catalyst if needed, polymer-ization be~ng continued substantially to completion. Pre~erably 1 during the first sta~e, the ratio of vinyl ester to acrylate and/or methacrylate monomer ls greater than about 4.5 until about 40-60% of the total monomer charge is added and during the second addition, the ratio of 5 vlnyl ester monomer to acrylate and/or methacrylate monomer is Iess than about 4.5 unti.l the total remaining amount of monomers has been added to the polymerization reactor.
One or more other ethylenically unsaturated monomers co~
polymerizable with monomers (a) and (b) present in an amount 10 of up to 5 welght percent of the total monomer charge can be added at the commencement of or during the polymerization sequence. It may be advantageous to initially polymerize a small amount, i.e., about 5~, o~ the total vlnyl ester monomer in the reactor prior to commencement of the first 15 stage polymerization.
The process herein contemplates the use of known and conventional surface active agents, buffers~ protective colloids, catalysts, and the like, in the usual amounts, and can be carried out ~n equipment heretofore employed for 20 emulsion polymerization.
Typically, the latices produced in accordance with this invention will possess a solids content from - about 60 to about 70 weight percent and even higher. The ~ viscosities of the high solids latices herein are generally 25but a fraction of the viscosities of latices prepared in-the usual manner, l.e., by simultaneous addition of monomers, and will usually not exceed 15,000 cp. Brookf-ield viscosity (~VF, Spindle No. 1) at 2 rpm. Viscosities of latices of equivalent high solids which are preared in the con~entional 30way have attained 50,000 cp. Brookfi~ld ~iscosity (RVF~
Spindle No. 5) at 2 rpm. The combination of hlgh solids content and low vi~cosity makes the latices of this invention especially useful for formulation as paints and other surface coatings.

~5033 The latices prepared in accordance with the process o~ this invention contain copolymers of at least one vinyl ester and at least one acrylate and/or methacrylate ester.
5 Generally, when preparing these copolymers, from about 50 weight percent to about 95 wei~ht percent, and preferably from about ~5 weight percent to about 85 weight percent, of vinyl ester will be copolymerized with ~rom about 5 weight percent to about 50 weight percent, and preferably 10 ~rom about 15 weight percent to about 35 weight percent~
of acrylate and/or methacrylate ester based on the total weight of the monomers present.
Among the vinyl esters which can be advantageously used in this invention are included vinyl formate, vinyl 15 propionate, vinyl butyrate and vinyl chloroacetate. Vinyl acetate is e~pecially preferred ~or use herein. Illustra-tive of acrylate esters and methacrylate esters which can be used in this invention to good effect are methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 20 isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexylacrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decyl : acrylate, dodecyl acrylate~ cetyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl 25 methacrylate, ethyl methacrylate, n-propyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylbutyl methacrylate, octyl methacr~late, 3~5,5-trimethylhexyl methacrylate, decyl methacrylate, cyclohexyl methacrylate~ norbornenyl 3 methacrylate, benzyl metnacrylate, phenyl methacrylate,and neopentyl methacrylate. Butyl acrylate has been found to be especially advantageous ~or use herein.
As previously stated, up to 5 weight percent of the total weight of the monomers present can be 1 interpolymerized with one or more additional ethylenically unsaturated monomers illustrative of which are the followin~:
ethylene, propylene, l-butene, 2-butene, isobutylene, - 5 l-pentene, 2-methyl~2-butene, l-hexene, 4 methyl-l~pentene, 3,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene, 6-ethyl-l-heYene, l-heptene, l-octene, l-decene, l-dodecene, allene, butadiene, isoprene, chloroprene, 1,5-hexadiene, 1,2,5-hexatriene, divinylacetylene, cyclopentadiene, dicyclo-10 pentadieneg norbornene, norbornadiene, methylnorbornene, cyclohexene, styreneg alphà-chlorostyrene, alphamethyl-styrene, allylbenzene, phenylacetylene, l-phenyl-l, 3-butadiene, vinylnaphthalene, 4-methylstyrene~ 2,4-di-methylstyrene, 3-ethylstyrene, 2,5-diethylstyrene, 2-meth-15 oxystyren~ 4-methoxy-3-methylstyrene~ 4-chlorcstyrene, 3~

4-dimethyl-alpha-methylstyrene, 3-bromo - 4- methyl-alpha-methylstyrene3 2,5-dichlorostyrene, 4-fluorostyrene~ 3-iodostyrene, 4-cyan~styrene, 4~vinylbenzoic acid, 4-acet-oxystyrene, 4-vinyl benzyl alcohol, -3-hydroxystyrene, 1,4-20 dihydroxystyrene, 3-nitrostyrene, 2-aminostyrene, 4-~,N-dimethylaminostyrene, 4-phenyls+yrene, 4-chloro-1-vinyl-naphthalene, acrylic acid, methacrylic acid, acrolein, - methacrolein, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-methyl methacrylamide, chloroacrylic 25 acid, methyl chloroacrylic acid, chloroacrylonitrile~
ethacrylonitrile, ~-phenyl acrylamide, N,N-diethylacryl-amide, N-cyclohexyl acrylamide, vinyl chloride, vinylidene chloride, vinylidene cyanide, vinyl fluoride, vinylidene fluoride, trichloroethene, methyl vinyl ketone~ methyl 30 isopropenyl ~etoneg phenyl ketone, methyl alpha-chlorovinyl ketone, ethyl vinyl ketone, divinyl ketone, hydroxymethyl vinyl ketone, chloromethyl vinyl ketone3 allilydene dia-cetate, methyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, 2-methoxyethyl 3~ vinyl ether, 2-chloroethyl vinyl ether, methoxyethoxy 1 ethyl vinyl ether, hydroxyethyl vinyl ether, aminoethyl vinyl ether, alpha-methylvinyl methyl ether, divlnyl ether, di~inyl e~her of ethylene glycol or diethylene glycol or triethanolamine, cyclohexyl vinyl ether, benzyl vinyl ether, phenethyl vinyl ether, cresyl vinyl ether, hydroxyphenyl vinyl ether, chlorophenyl vinyl ether~ napthyl vinyl ether, d.~le~hyl maleate, diethyl maleate, di-(2-ethylhexyl) maleate, msle~c anhydride, dimethyl fumarate, dipropyl fumarate, vinyl ethyl sulfide, divinyl sulfide, v~nyl 10 p-tolyl sulfide, divinyl sulfone, vinyl ethyl sulfone, vinyl ethyl sulfoxide~ vinyl sulfonic acid, sodium vinyl sulfonate, vinyl sulfonamide, vlnyl ben~amlde, vinyl pyridine~ N-vinyl pyrollidone, N-vinyl carbaæole, N-(vinyl benzyl)-pyrrolidine, N-(vlnyl benzyl)-pyrrolidine, 15 N-(vinyl benzyl~ piperidine, l-vinyl pyrene, 2-isopropenyl furan, 2-vinyl dibenzofuran, 2-methyl-5-vlnyl pyridine, 3-isopropenyl pyridine, 2-vinyl piperidine, 2-vinyl quinoline, 2-vinyl benzoxazole 9 4-metk~1-5-vinyl.thiazole~
vinyl thiophene, 2-isopropenyl thiophene, lndene, coumarone, 20 l-chloroethyl vinyl sulfideg ~inyl 2-ethoxye~hyl sulfide, ~inyl phenyl sulfide, vinyl 2-naphthyl sulfide, allyl mercaptans, divinyl sulfoxide, vinyl phenyl sulfoxide, - vinyl chlorophenyl sulfoxide, methyl vinyl sulfonate, Yinyl ~ sulfoanilide, and the like. Part or all of these optional 25 monomers c~l be charged to the reactor at the commencPment of or during the polymerlzation sequence. In some lnstances, these monomers may be used at a co~cen-tration below about two weight p~rcent to avoid undue coagulation.
The surface actlve agents contemplated by_thls in~ention include any of the known and con~entional surface active and emulsifying agents, principally the

5()33 1 nonionic and anionic materials, and mixtures thereof heretofore empl3yed in the em~lsion copoly~erization of vinyl acetate and ethylene, the nonionic surfactants being especially preferred. Among the nonionic surface active 5 agents ~hich have been found to provide good results are ~ included the t'I~epals" (G.A.~.), the "Tweens" (Atlas Chemical) and the "Pluronics~ ASF ~yandotte). The "Igepals" are members of a homolo~ous series of alkylphenoxypol~(ethyleneoxy) ethanols which can be 10 reprecented by the general formula ~ ~ _ o ~ CH2 ~ ~ 1 2 ~ ~

15 ~herein R represents an alkyl radical and n represents the number of mols of ethylene oxide employed-~ among which are alkylphenoxypoly(ethyleneoxy) ethanols having alkyl groups containing from about 7 to about 18 carbon atoms, inclusive, and having from about 4 to about 100 ethyleneoxy 20 units, such as the heptylphenoY.ypoly(ethylenoY~y) ethanols, nonylphenoxypoly(ethyleneoxy) ethanols and dodecylphenoxy-poly(ethyleneoxy) ethanols; the sodium or ammonium salts of the sulfate esters of these alkylphenoxypoly~ethyleneoxy) ethanols, alkylpoly(ethyleneoxy) ethanols3 alkylpoly-(propyleneoxy)ethanols; octylphenoxyethoxyethyldime-thylbenzylammonium chloride; polyethylene glycol t- -dodecylthioether. The "Tweens" are polyoxyalkylene derivatives of fatty acid partial esters of sorbitol anllydride such as the polyoxyalkylene derivatives of 30 sorbitan monolaurate, sorbitan rnonopa~nitate~ sorbitan mono~tearate~ sorbitan tristearate, sorbitan monooleate and sorbitan trioleate. The "Pluronics" are condensates of 3~ * Trade Mark ~, ~ ~S03;~
9~
1 ethylene oxide with a hydrophobic base formed b~ condensing propylene oxide with propylene glycol, and the like. Other suitable nonionic surfactants which can be employed herein are ethylene oxide derivatives of long chain fatty alcohols 5 such as octyl~ dodecyl~ lauryl or cetyl alcohol. Anionic sur~ace active agents which can be used here~n include the alkali metal sulfates of C12 to Cll~ alcohols such as sodium lauryl sulfate and alkali metal salts of alkyl benzene sulfonic acids and alkyl toluene sulfonic acids having 10 aliphatic side chains of about 10 to about 15 carbon atoms~
and the like. The surface active agent is generally employed at from about 3~ to about 5~ and preferably, at from a~out 3.5v~ to about 4.5%g by weight of the total monomers present.
15A protective colloid is generally incorporated in the aqueous emulsions of this invention.~ Such known and conventional protective colloids as: the partially and fully hydrolyæed polyvinyl alcohols; cellulose ethers, e.g., hydroxymethyl cellulose, hydroxyethyl cellulose, 20 ethyl hydroxylethyl cellulose and ethoxylated starch derivatives; the natural and synthetic gums, e.g. gum tragacanth and gum arabic, polyacrylic acid, poly(methyl vinyl ether/maleic anhydride) and polyvinyepyrrolidone, -- are well suited for use herein, preferably at a level of 25 from about 0.1% to about 2% by weight of the emulsion.
Polyvinylpyrrolidone and the partially hydrolyzed polyvinyl alcohols are especially advantageous for use in this invention.
The catalysts used in the copolymerization reaction 30 are any of tne known and conventional free radical polymerization catalysts heretofore used for the prepara-tion of copolymer latices and include inorganic peroxides such as hydrogen peroxide, sodium perchlorate and sodium perborate, inorganic persulfates such as sodium persulfate, 35 potassi.um persulfate and ammonium persulfate and reducing lagents such as sodium hydrogen sulfite. Catalyst (includ-ing co catalyst reducing agent, lf employed) is generally utilized at a level of from about 0.1~ to about 1~ by weight of total comonomers. The catalyst can be added to 5the reaction medium all at once or it can be divided into two or more parts and added to the reactor medium with each addition of monomer or during either or both polymerizatlon sequences.
An alkaline buffering agent such as sodium lObicarbonate, ammonium bicarbonate~ sodium acetate, and the like3 may be added to the aqueous system to ma~n-tain the pH at the desired level. The amount of buffer is generally about 0.01 to 0.5% by weight based on the monomers.
The method by which the monomers are charged to the reactor is not critical. The monomers can be added to the reaction medium as a steady stream/ drop-wise or in periodic increments; the ~inyl ester and acrylate/methacrylate ester can be admixed pr~or to being charged to the reactor 20or these monomers can be introduced to the reactor as separate streams. Advantageously, the monomers are added as a steady s~ream over periods ranging from about 1 hour to about 5 hours and preferably, over a period of ~rom - about 2 hours to about 3 hours.
The temperakure reaction herein can be selected at levels which have heretofore been employed in emulsion polymerization. For both polymerization sequences the temperature can range from about 0C. to about lOO~C~
preferably ~rom about ambient temperature to about 80C, 30wi~h the reaction medium being constantly stirred or otherwise agitated. The substantlal completion of poly-merization Ls usually indicated when ~ree monomer content &~033 1 of the latex emulsion is below about 1~ and preferably - below about 0,5~.
In the examples which follow, ln which conventional equ~pment was used and weight parts Qre given~ examples 5 1 to 11 are illustrative of the copolymer latices and emulsion polymerization process of this invention while comparative examples 1~ and.lB are given by way of illustratin~ the prior art latices and polymerization procedures. Components of the emulsion media employed 10 in the examples are identified as follows:

1 Component Source Co~,position Triton X-~O~ Ro~ and Haas Octylphenoxy Company polyethoxy ethanol Triton QS-9 Rohm and Hass Phosphate ester, * Co~pany acid form Tamol 850 Rohm and Hass Sodium salt of Company polymeric carboxylic acid Sipon ~SY Alcolac, Inc. Sodium lauryl ether sulfate Mono~er X-980 Rohm and Hass Trimethylol Company propane tri~ethacrylate Sodium lauryl sullate Butyl Carbito~ Union Carbide Diethylene Corporation glycol monobutyl ether Plasticizer Cincinnati Milacron Surfactant Chemicals~ Inc.
Natrosol*250i~R Hercules, Inc. Xydroxyethyl-cellulose Trycol* PO-407 Emery Industries Octyl phenol condensed with 40 units of ethylene oxide CI~P Acetate Troy Chemical Preservative Corporation preparation : containin~ lO, - by weight of chloromethoxy-propylmercuric acetate * Trade Mark ~, ~ Example 1 .
To a 2000 ml resin flask equipped with stirrer, reflux condenser~ addition funnel and thermometer were Added the ~ollo~ing solutions:
(a) ~eionized water 200 parts Polyvinylpyrrolidone2.5 parts (b) Deionized water 220 parts TRITON X-405 40 parts TRTTON QS-9 12.5 parts Sodium hydroxide to pH 10 10 followed by 40 p~rts of vinyl acetate. The re~ctor was heated with a water bath and at 60C.,1.65 parts of ammonium persulfate in 10 parts of water ~lere added all at once. At 72C., the addition of 320 parts ol vinyl acetate was started and then continued at 78-80C, o~er 15 about 65 minutes. Thereafter, a mixture of 360 parts of vinyl acetate and 150 parts o-, butyl acrylate was added over about 120 minutes. When all the mo~omer mixture had been added, 002 part of ammonium persulfate ~las introduced and the batch was given an additional 30 rninutes at 80C.
20 to completely consume the monomers. Cooled to room temperature, the copolymer latex had a 65.2 percent solids content and a Brookfield Viscosity (RVF, Spindle No. 2) of - 2700 cp at 2 rpm and 800 cp at 20 rpm.
, ~ J~ 3 3 lComparative Example lA
In this example, which is illustrative of the prior art, a sin~le stage addition of monomers was used. The protective colloid ~as omitted in order to avoid 5unmanageable viscosity for the completed latex.
To a 2000 ml resin flask equipped as in Example 1 were added:
Deionized water450 parts TRITON X-405 37 parts TRITON QS-9 25 parts Sodium hydroxideto pH 10 The solution was brought to 70C ~Jith a controlled temperature water bath and 1.65 parts of ammonium persulfate in 10 parts of water were added all at once, followed by a mixture of 720 parts OL vinyl acetate and 15150 parts ol but~l acrylate monomers added over about 140 minutes. The reaction temperature rapidly rose to, and was controlled at, 800C durin~ addition of the monomers.
Followin~ the monomer addition~ 0.3 part of ammonium persulfate in 10 parts of water additionally was added.
20 The reaction temperature was held at 80C for another hour and then the batch was cooled to room temperature. The copolymer latex had S4.6 percent solids content and Brookfield viscosity (RVF, Spindle No. 5) of 50,000 cp at 2 rpm and 12,100 cp at ~0 rpm. This viscosity was - 25alto~ether too high for a good latex paint formulation.

5 ~ 3 3 ?aratlve EY~ample lB
. . _ .
This exa~ple is also illustrative of the prior art procedure of copolymerizing all of the monomers simultaneously. The following recipe was prepared and 5added to a resin flask equipped as in Example 1:
g.
Vinyl acetate 71 Butyl acrylate 14~
Deionized water 470 Triton X-405 37 Triton QS-9 25 NaOH 2.5 (NH4)2S2 8 1.65 + 0.3 The surface active agents were dissolved in the water and the solution's pH was adjusted to 11.6 with the NaOH (dissolved in H20). The solution was charged to the reactor, heated to 70C. At this point the first part of the (N~4)2S208 was added and the addition of the monomer blend comrnenced. The addltion rate was fast during the 20first 2 hours o~ polymerization (approximately 80~ of the monomer was added during this period~. During the last half hour the monomer addition rate was lowered (with the - latex becoming fairly viscous~. Upon completion of the monomer addition, the second part of the catalyst was added (dissolved in 500 ml ~ O). Afterwards, the batch was kept at about 800C for about 1 hour. The polymerization temperature was 80C+1C. The resulting latex had a good appearance but was very viscous; it did not contain any gel but it contained nurnerous air bubbles.
30The following properties of the latex were observed:

1 Solids: 5~
Brook~ield Viscosity (Spindle No. 5) r.p.m. 2 4 10 20 readin~ 25 32.5 4O 60.5 5 factor 2000 1000 400 200 cp 50000 32500 13400 ~2100 The dra~down on a ~lass plate was clear but contained many bubbles.
l~h.ile the latex of Example 1 is an excellent 10 candidate ~or use in paints, it is readily apparent that the latices produced in accordance with the prior art procedure of simultaneous copolymerization are not suitable materials for surface coating formulations.

.

~0 3o 1 Example 2 To the resin flask reactor of Example 1 were added:
Deionized water 420.parts TRITON X-405 40 parts SIPON ESY 20 parts Polyvinylpyrrolidone5 parts Sodium acetate 3.2 parts Vinyl acetate 40 parts Ammonium persulfate 1.65 parts in Water 10 parts At 72C., the addition of 320 parts of vinyl acetate was started, then continued at 78-SooC. over about 65 minutes.
Thereafter~ a mixture of 360 parts of vinyl acetate and 150 parts of butyl acrylate was added over about 120 15 minutes. When all the monomer mixture had been added, 0.2 part of ammonium persulfate was introduced and the batch was held an additional 30 minutes at 80C to consume remaining monomersO When coolad to room ~emperature9 the copolymer latex was found to have 64.8 percent solids and 20 a ~rookfield viscosity ~RVF, Spindle No. 1) of 550 cp at 2 rpm and 280 cp at 20 rpm.

~ ~S033 1 Example 3 ~ .
To the resin flask reactor of Example 1 were added:
Deionized water335 parts TRITON X-405 50 parts SIPON ESY 22 parts Polyvinylpyrrolidone 5 parts Sodium acetate3.2 parts Vinyl acetate40 parts After the addition at 60C. of 1.~5 parts of ammonium 10 persulfate in 10 parts of water~ 320 parts of vinyl acetate were added over 75 minutes at 78-800C. followed by a solution of 0.1 part of ammonium persulfate in 5 parts of water, then a mixture ol 300 parts o~ vinyl acetate and 150 parts of butyl acrylate over 135 minutes.
To complete polymerization, 0.5 part of ammonium persulfate W&S intermittently added over the next hour.
The laiex batch, cooled to room temperature, contained o9.5 percent solids and had a Brookfield viscosity (RVF, Spindle No. 2) of 1200 cp at 2 rpm and 570 cp at 20 rpm.

~ ~5~33 1 EY.ample 4 Example 2 ~ras repeated except that 8.7 parts of acrylic acid were included in the second mono~ner addition, i.e.~ of vinyl acetate-but~l acr~late mixture. The latex 5 contained 65.8 percent solids and had a Brookfield viscosit~ (R~, Spindle No.-2) of 2600 cp at 2 rprn and 900 cp at 20 rpm.

~S033 ^20 -1 EY.2m1~1e 5 , .
~ o test the perlormance ol the hi~h solids latices of this invention, standard latex paints were prepared from the copolymer latices of Example 1 (Part A) and Example 5 2 (Part B). Usin~ normal paint making procedures, a plgment ~rind was prepared and then let down with latex~
water alld thickener solution to arrive at sui~able brushing viscosities. The viscosity of the Part A paint was 77 Krebs Units (K.U.) and that of the Part B paint was 84 Kre~as 10 Units (K.U.). Both paints were drawn down on a Leneta contrast chart, using a ~ mil drawdown bar. The dry draw-downs ~rere exam~ned and found to be quite satisfactory with no latex coagulation or pigment agglomeration present.
Hiding power was considered to be entirely acceptable.
15 Brushouts were made on compressed paperboard, both one and two coa-ts, with an overni~ht dry between coats. Application of the two paints was accomplished without noting difficulties of any sort. Viscosities were cnecked af~er one month for shelf stability and found to be excellen~.
20 The Part A paint increased by only 2 K.U. and tne Part 3 paint remained the same.

~5~133 1 Example 6 -The following were added to a resin flask as in Example lo gm - 5 Vin~1 acetAte 720 Butyl acrylate 150 Deionized water 455 Triton X-405 40 Sipon ESY 20 Polyvinylpyrrolidone 5 N 2 3 3.2 (NH4)2S28 165 ~ 0.1 ~ 0.2 The surface active agents, polyvinylpyrrolidone and bu~fer were dissolved in cold water. The solution plus 1~40 gm of vinyl acetate were charged to the reactor and heated. At 60C., the first part of the catalyst was added and when the reaction temperature reached 72C., the addition of the first sta~e of monomer (320 gm vinyl acetate) was started. During this addition (65 minutes) 20the polymerization temperature was kept between 7~-78C.
with coolinO. Immediately after completing the addition of the ~irst stage, the addition of the second stage - (3500m vinyl acetate admixed with 150 gm butyl acrylate) was started. I'he reaction temperature dropped, and light 25 heating was necessary to keep the reaction temperature from falling. The rate of addition was somewhat low in order to prevent the build up of free monomer in the .eactor which mi~ht otherwise produce foam~- Catalyst was added both when the addition had started and upon its 30 co~pletion. A~ter completion of the monomer addition_ (160 minutes) the temperature rose to 84C. The latex obtained had a good appearance. Very little ~rit remained on the filter after the latex had been screened.

1 The follo~lirlg properties of the latex ~lere observed:
Solids: 54.8~
Brool~field Viscosity (Spindle No. 1) rOp.m~ 2 4 10 20 5 reading li 185 35 56 .
factor 5 25 10 5 cp 55 ~2 3~ 280 Glass drawdown of the latex appeared very good; the latex was some~hat hazy but gel/bubble-free.

5~ 33 l E~aMple 7 The following were added to a resin flask as in Example l:

gm Vinyl acetate 740 Butyl acrylate 157 Deionized water 455 Triton X-405 40 Triton QS-9 12.5 Polyvinylpyrrolidone 3.5 NaOH 1.2 (NHl~)2S2g 1.65 The polyvinylpyrrolidone/sur~ace active agent solution 15 was prepared and pH adjusted as in the previous examples.
First stage addition of monomer (55 minutes) consisted of increments of 40 and 320 gm vinyl acetate. Second stage addition (140 minutes) consisted of a mixture of 380 gm vinyl acetate and 157gm butyl acrylate. While the second 20 stage of monomer was slightly increased to compensate for possible losses, the solids content indicated that this was not necessary. ~hen the addition of the ~econd stage : was started, as usual the reaction temperature dropped.
At this point O.lgm of extra catalyst was added, but 25 without much result. The reaction temperature was then regulated by controling the monomer flow and bath temperature. At the beginning of the second stageg the temperature dropped to 75C., but during the major part, it was between 78~80C. At the end of the monomer ad~ition, 30.2gm of (I~4)2S208 was added. The tem~erature rose to 83C. No ~oam was observed. The latex contained the usual amount of grit~ but once this grit was removed by filtration the product had an acceptable appearance. The following properties of the latex were observed:

~L85~3 . , 1 Solids: 65.7~
Brookfield Vis~osity (Spindle No.2) r.p.m. 2 4 10 20 readin~ 8 12 20 29 5 factor 200 100 40 20 cp 1~00 1200 800 580 Glass drawdown of the late~ gave a slight haze but tlle latex l~as nevertheless of good overall appearance.

~ ~ ~ S ~ 3 3 ~25-1 Example 8 The following interior paint formulations wereprepared with the copolymer latices of Examples 6 and 7:
Pi~ment Grind (in a Cowles Dissolver) gm Water 516 CI`IP Acetate Ethylene Glycol 9~
Butyl CarbitolS8 K~C03 Tamol 850 8 Plasticizer Surfactant 12 3~ Natrosol 250 MR600 Calcined Clay240 Whitening (atomite~ 1000 Total 3145 Paint A B
Pigmeni Grind 394 394 20 Latex of Example 6 80.5 Latex of Example 7 - 80.5 Water 93 95 3~ Natrosol 250 MR 15 13 ~ Klebs Units (K.U.) 84 77 t Drawdowns of Paints A and B were made on Leneta contrast charts using a 6 mil drawdown bar. The paints were brushed on compressed paperboard, both one and two coats, with an overnight dry between coats. The paperboard panel was sealed with the diluted latex of Example 6 30 before appllcation of the paint. Both drawdowns and_ brushings were satis~actory. No coagulation of latex or pigmerlt agglomeration occurred with either paint.
Viscosities: Paint A 84 K.U.
Paint B 79 K.U.

-26 ~ ~ ~ 5~3 1 Ex~le 9 T,~e follo~lin~ were added tc a resin flaslt as in Example 1: grn Vinyl acetate 7 But~l acrylate 150 Deionized water 360 Triton X-405 50 Sipon ESY 22 Polyvinylpyrrolidone 5 Na 2CCH3 32 (l~4)2S208 1.~5 ~ 0.1 ~ 10.5 ~irst stage addition of mono~ner (360gm of vinyl acetate over 75 minutes) was completed and a~ter about 130cc of monomer mixture from the second stage addition (360g~ of 15vinyl acetate rnixed ~Jith 150gm butyl acrylate) remained to be added, the final addition of catalyst was started (0.5gm a~nonium sulfate in 20ccH20). The resultin~ latex had a ~ood appearance while containing the usual amount of grit which ~Jas readily removable by filtration or similar 20means. The following properties of the latex were observed-Solids: 69.3 - .5 Brookfield Viscosity (Spindle ~To. 2~
r.p.rn. 2 4 10 20 reading 6 9-5 17-5 28.5 25factor 200 ~oo 40 20 cp 1200 950 700 570 Glass drawdowrl of the latex made several days after the product ~Jas made gave a very good gel and bubble free coating.
3~

1 EXample 10 The following were added to a resin flask as in Example 2:
gm Vinyl acetate 720 Butyl acrylate 150 Acrylic acid 8.7 Deioni~ed water 435 Triton X-405 40 Sipon ESY 20 Polyvinylpyrrolidone 5 NaO2CCH3 3.2 (NH4)2S28 1.55 + 0.2 The polymerization was started as in Example 6 but with 15 3O0gm of vinyl acetate being added in the first stage (oveY 65 minutes) and 3OOsm of vinyl acetate admixed with 150gm butyl acrylate and ~.7gm acrylic acid being added in the second stage (over 160 minutes). During the second stage9 the addition rate and bath temperature were ?0 regulated so that reaction temlperature was always close to the bath temperature (78-80C). No catalyst addition was made at the start of the addition of the second stage. The final catalyst addition was ~tarted about 5 minutes after completion of the addition and extended over a period of 25 about 15 minutes. After completion of the monomer addition, the reaction temperature or about 40 minutes was slightly above or equal to the bath temperature. Approxi~ately 15 minutes after the reaction temperature ha~ ~egun to decline, the contents of the reactor were cooled to room temperature.
30 The resulting latex had no free monomer odor and had a good, nearly grit-free appearance. Screening of the monomer was very easily accomplished.

1 Tile followin~ properties of the latex were observed Solids: ~5.8~
Brookfield Viscosit~ (Spindle No. 2) rpn~ 2 4 10 20 sreading 13 19 31 45 factor 200 100 40 20 cp 2~00 1900 1240 900 Glass dra~down of the latex gave a gel and bubble free coatin~ of very good overall appearance.

gLl~S033 1 Exa~ple 11 This example results in a latex of high vlscosity~ pol~nerization being conducted.ln a sequence of two stag~ but with a mixture of vinyl acetate and butyl 5 acrylate being polymerized at each stage of monomer addition~ The ~ollowing were added to a resin flask as in ~x~le 1:
gm Vinyl acetate 700 Butyl acrylate 150 Monomer X-980 26 Acrylic ~cid 8.7 Deionized water 450 Emersal 6400 20 Trycol P0-407 - 40 ~olyvinylpyrrolidone ' 2 NaO2CCH3 4 (NH4)2S28 16 To facilitate the dissolution of the Emersa~ 6400, 20 some water was added to the surface active agent followed by heating.
The monomer mixtures were prepared as follows:
Initial - Stage First Stage ~gm) ' Second Stage (gm) 25 Vinyl acetate 4 310 350 ~utyl acrylate 65 85 Monomer X-980 13 ^ 13 Acrylic acid 0 4.35 4-35 First stage addition o~ monomer took place over 3 80 minutes and second stage addition of monomer was carried out over 85 minutes. No extra catalyst was added upon completion of the monomer additions, The resulting latex which contained the usual small amount of grit had a good appearance with ~ust ~ trace of dilatancy.

* Trade Mark ~ .

. -30-1 The following properties o~ the latex wer~
observed:
Sol.1ds: 65.2~
Broo~fleld Viscosity (Splndle No. 3) 5 r.pOmO 2 4 10 reading 16.5 1 3 3290 ~ac~or 500 250 100 50 cp 8250 5250 3000 1950 Glass drawdown o~ this latex had good appearance 10 w~th only a slight haze.

~0

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing high solids, low viscosity copolymer latices from:
a) at least one vinyl ester monomer in an amount representing from about 50 weight percent to about 95 weight percent of total monomer charge, and b) at least one monomer selected from acrylate ester monomer or methacrylate ester monomer representing the balance of the total monomer charge; which comprises, polymerizing in a first stage a significant portion of the total vinyl ester monomer charge and from 0 to about 50 weight percent of the total acrylate ester and/or methacrylate ester monomer in an aqueous emulsion reaction medium containing a polymerization catalyst, and there-after polymerizing in a second stage the remaining portion of the total vinyl ester monomer charge together with the remaining portion of the acrylate ester and/or meth-acrylate ester monomer in the reaction medium containing additional catalyst if needed, polymerization being continued substantially to completion.

2. The process of Claim 1 wherein at least 10 weight percent of the total vinyl ester monomer charge is polymerized in the first stage.

3. The process of Claim 1 wherein at least 25 weight percent of the total vinyl ester monomer charge is polymerized in the first stage.

4. The process of claim 1, 2 or 3, in which the vinyl ester monomer is vinyl acetate.

5. The process of claim 1, 2 or 3, in which the acxylate ester monomer is butyl acrylate.

6. The process of claim 1, 2 or 3, in which a total of from about 65 weight percent to about 85 weight percent of vinyl ester is copolymerized with a total of from about 35 weight percent to about 15 weight percent of acrylate and/or methacrylate ester.

7. The process of claim l, 2 or 3, in which less than about 60 weight percent of the total vinyl ester monomer present is initially added to the reaction medium with the balance thereof being sequentially added to the reaction medium with the acrylate and/or methacrylate ester.

8. The process of claim l, 2 or 3, which includes a surface active agent that is at least a non-ionic or anionic surface active agent.

9. The process of claim 1, 2 or 3, in which the reaction medium additionally contains a protect-ive colloid selected from partially and fully hydrolyzed poly-vinyl alcohols; cellulose ethers; hydroxymethyl cellulose;
hydroxyethyl cellulose, ethyl hydroxyethyl cellulose; ethyoxyl-ated starch derivatives; natural and synthetic gums; gum tragacanth; gum arabic; polyacrylic acid, poly (methyl vinyl ether), maleic anhydride, and polyvinylpyrrolidone, present in an amount of from about 0.1% to about 2% by weight of the emulsion.

10. The process of claim l, 2 or 3, in which the reaction medium additionally contains an alkaline buffering agent.

11. The process of claim 1, in which the balance of the total vinyl ester monomer charge together with the balance of the acrylate ester and/or methacrylate ester monomer charge is added incrementally in the second step, wherein the ratio of vinyl ester monomer to acrylate and/or methacrylate monomer in the first incremental addition is greater than about 4.5 until about 40-60% of the total monomer charge is added, and thereafter, in a second incremental addi-tion, the ratio of vinyl ester monomer to acrylate and/or meth-acrylate monomer is less than about 4.5 until the remaining amount of monomers is added to the reactor.

12. The process of of Claim 1 in which one or more other ethylenically unsaturated monomers copolymerizable with monomers (a) and (b) present in an amount of up to 5 weight percent of the total monomer charge is added at the commencement of, or during, polymerization.

13. The latex prepared by the process of Claim 1, 11 or 12.