CA1217893A - Method for making polymodal aqueous synthetic resin dispersions - Google Patents
Method for making polymodal aqueous synthetic resin dispersionsInfo
- Publication number
- CA1217893A CA1217893A CA000455292A CA455292A CA1217893A CA 1217893 A CA1217893 A CA 1217893A CA 000455292 A CA000455292 A CA 000455292A CA 455292 A CA455292 A CA 455292A CA 1217893 A CA1217893 A CA 1217893A
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- Prior art keywords
- seed latex
- particles
- monomers
- polymerization
- weight
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
- C08F265/04—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of esters
- C08F265/06—Polymerisation of acrylate or methacrylate esters on to polymers thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F291/00—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00
Abstract
ABSTRACT OF THE DISCLOSURE
A method for making an aqueous polymodal synthetic resin dispersion by the emulsion polymerization of an ethylenically unsaturated monomer difficultly soluble in water, or a mixture of such monomers forming a polymer which is water insoluble under the conditions of polymerization, in an aqueous phase containing an emulsifier and a water soluble polymerization initiator, which method comprises adding a seed latex to the polymerization mixture in the course of the emulsion polymerization before more than 40 weight percent of said monomers have been polymerized, the particles of said seed latex being smaller by a factor ranging from 2 to 15 than are particles already formed by emulsion polymerization, the amount by weight of the particles in the seed latex being not greater than 10 percent by weight of the monomers and the ratio by weight of particles of said seed latex to the weight of the monomers already polymerized being from 1:4 to 1:500.
A method for making an aqueous polymodal synthetic resin dispersion by the emulsion polymerization of an ethylenically unsaturated monomer difficultly soluble in water, or a mixture of such monomers forming a polymer which is water insoluble under the conditions of polymerization, in an aqueous phase containing an emulsifier and a water soluble polymerization initiator, which method comprises adding a seed latex to the polymerization mixture in the course of the emulsion polymerization before more than 40 weight percent of said monomers have been polymerized, the particles of said seed latex being smaller by a factor ranging from 2 to 15 than are particles already formed by emulsion polymerization, the amount by weight of the particles in the seed latex being not greater than 10 percent by weight of the monomers and the ratio by weight of particles of said seed latex to the weight of the monomers already polymerized being from 1:4 to 1:500.
Description
The present inven-tion relates to a method for making polyrnodal (including bimodal) syn-thetic resin dispersions.
Polymodal dispersions are dispersions wherein the par-ticl.es are of di*ferent s:izesl with several clis-tinct maxima in the par-ticle size dis-tribu-tion curve. Dispersions wi-th two such rnaxima are bimodal and -those wi-th more -than -two rnaxima are polyrnoda:L. Cornpared wi-th dispersions having only one particLe slze maxi.rrlurrl, bimodal and other polymodal dispersion have a lower viscosity, exhibi-t be-t-ter flowability in film formation, and give films possessing improved water resistance.
According to published German patent application DOS
29 31 127, bimodal dispersions can be prepared by mixing dispersion having different average particle sizes.
Ano-ther approach is to add, in the second stage of a two stage emulsion polymerization process, an additional amount of emulsifying agent sufficient -to result in the formation of new particles which do not grow to a size as large as the particles originally formed and which, thus, form a second maximum in the distribution curve. The processes of published German patent applications DOS 28 37 992 and 29 31 127 and of U.S. patent 4,254,004 are based on this principle. However, it is difficult to obtain reproducible results with these processes because the properties of the dispersion depend markedly on -the number of particles formed in the second stage. That number depends, in a manner tha-t is difficult to de-termine, on a number of factors.
According to French patent 2,344,579, a "microsuspension"
of polyvinyl chlor:ide particles exhibi-ting more than two par-ticle size maxima is obtained by mixing a pre~iously prepared ~;
"microsuspension" with two further previously prepared "rnicrosuspensions" or dispersions, at least orle of which contains an organically soluble initiator incorporated in i-ts particles, and by adding more monomer in -the absence of fur-ther ini-tla-tors. The par-ticles incorporating the initiator -then con-tinue -to grow un-til the desired high solids content is reached, while the size of the particles free of initiator remains near:Ly -the same. The prepara-tion of such ini-tiator containing "microsuspensions" differ from -that of conven-tional emulsion polymerization in -that -the po]ymerization -time is much longer and relatively coarse particles are formed which will settle unless they are kep-t in -the dispersed state by agitation. The products obtained by this process can be used as substitutes for aqueous synthetic resin dispersions only in exceptional cases.
Published German patent application P 31 47 008 relates -to a process for the preparation of highly concentra-ted bimodal or polymodal synthetic resin dispersion wherein at least two la-tices containing synthetic resin particles of different particle sizes are mixed and monomers are polymerized in the presence of the mixture until the solids content is greater -than 58 weight percent. In the practice of this process, the syn-the-tic resins contained in the mixture of previously prepared latices always amount -to more than half of the syn-thetic resin contained in the final product, and usually to from 60 to 70 weigh-t percen-t. For -this reason, relatively large amounts are needed of -the previously prepared latices, at least one of which must be s-tocked in sufficient quantity whereas the other can ke prepared in a preceding process step. In this process, control of the size of -the finer latex particles is possible only within certain limits.
Polymodal dispersions are dispersions wherein the par-ticl.es are of di*ferent s:izesl with several clis-tinct maxima in the par-ticle size dis-tribu-tion curve. Dispersions wi-th two such rnaxima are bimodal and -those wi-th more -than -two rnaxima are polyrnoda:L. Cornpared wi-th dispersions having only one particLe slze maxi.rrlurrl, bimodal and other polymodal dispersion have a lower viscosity, exhibi-t be-t-ter flowability in film formation, and give films possessing improved water resistance.
According to published German patent application DOS
29 31 127, bimodal dispersions can be prepared by mixing dispersion having different average particle sizes.
Ano-ther approach is to add, in the second stage of a two stage emulsion polymerization process, an additional amount of emulsifying agent sufficient -to result in the formation of new particles which do not grow to a size as large as the particles originally formed and which, thus, form a second maximum in the distribution curve. The processes of published German patent applications DOS 28 37 992 and 29 31 127 and of U.S. patent 4,254,004 are based on this principle. However, it is difficult to obtain reproducible results with these processes because the properties of the dispersion depend markedly on -the number of particles formed in the second stage. That number depends, in a manner tha-t is difficult to de-termine, on a number of factors.
According to French patent 2,344,579, a "microsuspension"
of polyvinyl chlor:ide particles exhibi-ting more than two par-ticle size maxima is obtained by mixing a pre~iously prepared ~;
"microsuspension" with two further previously prepared "rnicrosuspensions" or dispersions, at least orle of which contains an organically soluble initiator incorporated in i-ts particles, and by adding more monomer in -the absence of fur-ther ini-tla-tors. The par-ticles incorporating the initiator -then con-tinue -to grow un-til the desired high solids content is reached, while the size of the particles free of initiator remains near:Ly -the same. The prepara-tion of such ini-tiator containing "microsuspensions" differ from -that of conven-tional emulsion polymerization in -that -the po]ymerization -time is much longer and relatively coarse particles are formed which will settle unless they are kep-t in -the dispersed state by agitation. The products obtained by this process can be used as substitutes for aqueous synthetic resin dispersions only in exceptional cases.
Published German patent application P 31 47 008 relates -to a process for the preparation of highly concentra-ted bimodal or polymodal synthetic resin dispersion wherein at least two la-tices containing synthetic resin particles of different particle sizes are mixed and monomers are polymerized in the presence of the mixture until the solids content is greater -than 58 weight percent. In the practice of this process, the syn-the-tic resins contained in the mixture of previously prepared latices always amount -to more than half of the syn-thetic resin contained in the final product, and usually to from 60 to 70 weigh-t percen-t. For -this reason, relatively large amounts are needed of -the previously prepared latices, at least one of which must be s-tocked in sufficient quantity whereas the other can ke prepared in a preceding process step. In this process, control of the size of -the finer latex particles is possible only within certain limits.
- 2 -The object of the presen-t inven-tion is to provi~le an improved process for the prepara-tion of polymodal syn-thetlc resin dispersions by -the emulsion polymerization of unsa-turated rnonor(lers in an aqueous phase con-taining an ini-tiator and an emulsifier, with addi-tion of a seed la-tex in the course of polyrner:iza-tion. 'I'his improved process should make i-t possible to reduce the need for a previously prepared seed latex and reliably to secure reproducibili-ty of -the particle size distribution, thus to obtain polymodal synthetic resin dispersions with constant, uniform end use properties. The synthetic resin dispersions prepared according to the method of the invention comprise at least -two particle families of different average particle size the largest particle family having an average diameter of 0.6 ~m or less and the average particle size of the next smaller particle family being at most two thirds of -the average particle size of the largest par-ticle family.
In accordance with the invention, this object is achieved by adding the seed latex before more than 40 weight percent of the monomers have been polymerized. Further, the seed la-tex particles are smaller by a factor ranging from 2 -to 15 than are the particles already formed by emulsion polymerization. Finally, the amount of the synthetic resin particles in the seed latex is no-t grea-ter than 10 percent by weight of the monomers, and the ratio of -the weight of the particles to the weight of the monomers already polymerized ranges from 1:4 to 1:500.
The process of the invention permits the preparation of polymodal synthetic resin dispersions without major modification of -the usual processes whereby conventional synthetic resin dispersions having only one maximum in the particle size dis-tribu-tion curve can l~?s~ 3 prepared. A polymodal particle size dis-tribu-tion is achieved solely through the one--time or repea-ted addit:ion of relatively srna]l amounts of a seed latex a-t an early stage of -the emulsion polymerization. Compared with methods in which a second particle forma-tion phase is ini-tia-ted by renewed addi-t:ion of emu]sLfier, the process of -the inven-tion :is distinguished by rnore accura-te reproducibili-ty since -the number of the addi-tional seeds can be controlled very accurately through the amount of -the seed la-tex. In contrast -to processes in which subs-tantial amoun-ts or different types of seed la-tices are added in -the course of polymerization, the process of the inven-tion requires very little seed latex of only one type. The process of -the invention therefore is both simple and reliably reproducible.
The monomers which are subjec-ted to emulsion polymerization in accordance with the invention are difficultly soluble in water at least to a considerable extent, by which is mean-t a solubili-ty of less than 10 weight percent, and preferably of less -than 2 weigh-t percent, at 20C. The proportion of difficulty soluble monomers in the polymer must be sufficiently high for the emulsion polymer formed -to be insoluble in the water phase, at least under the conditions of polymerization, and to precipi-tate in the form of dispersed latex particles. When mixtures of monomers are po]ymerized, -they are preferably composed of at least 70 weigh-t percent, and highly preferably of at least 90 weigh-t percent, of difficul-tly soluble monomers.
Sui-table monomers include the alkyl es-ters of acrylic acid and methacrylic acid having from 1 to 20 carbon a-toms in -the alkyl group, styrene and its homologs, vinyl es-ters of lower carboxylic __ids, dienes, and lower alpha-olefins, for example. These will generally -form the pr:incipal monomers representing more -than 50 weight percen-t of the synthetic resin. S~li-ta~le modifying rnonomers which usually account for less than 50 weight percen-t of the synthetic resin are acryloni-trile and rne-thacrylon:i-trile, acrylarrlide and methacrylamide as well as N-rnethylol compounds and N-methylol ethers -thereof, hydroxyalkyl es-ters of acrylic acid and methacrylic acid, optionally ~uaternized aminoalkyl esters and aminoalkylamides of acrylic acid and me-thacrylic acid, unsaturated carboxylic acids such as acrylic acid and me-thacrylic acid, maleic, fumar:ic and itaconic acid, and the half es-ters of dibasic carboxylic acids, as well as maleic anhydride.
A preferred class of synthetic resins is formed predominantly, that is, to -the extent of 70 percent or more, of alkyl esters of acrylic acid and/or methacrylic acid or mixtures thereof and of styrene. The resins preferably contain a srnall amount of an alpha, beta-unsaturated carboxylic acid.
The seed latex is formed by an aqueous dispersion of synthetic resin particles free of radical forming ini-tiators, which are smaller by a factor ranging from 2 to 15 than the particles of the emulsion polynler a-t the time the seed latex is added. The seed latex particles have an average par-ticle size ran~ing from 0.01 to 0.2 micron, for example, and preferably from 0.02 to 0.1 micron.
The average particle size is the weigh-t average of -the particle diameter, as determined by the method of H. Lange, Kolloid-Zeitschrift and Zeitschrift fur Polymere 223, 24 (1968), for example. A modern method of measurement is based on measuremen-t of the variations in sca-ttered ligh-t due to the Brownian movemen-t of the la-tex particles in a laser beam, generally called photon correla-tion spectroscopy.
The seed latex is prepared conventionally by emulsion polymerization in an a~ueous phase containing an emulsifier. By the use of an emulsi~ier concentration close to or s]iyhtly above the critical micelle co~centration, a very large number oE small latex seeds is formed, which seeds, through appropriate monomer addition, are allowed to grow to a particle size in the above range. The monomers from which the seed latex is formed may be the same as those used in the emulsion polymerization in accordance with the invention. However, other monomers, selected by the criteria set forth above with respect to the aforesaid monomers, may also be used.
The seed latex may have a polymer content ranging from 20 to 50, and preferably from 30 to 40, percent by weight. Lower polymer contents increase the amounts required to be used: higher polymer contents are detrimental because of high viscosity and because of stabilization problems during preparation and storage. As a rule, the seed latex can be stored for an extended period of time and may be kept on hand for a great many production batches of the polymodal synthetic resin dispersion~
An important objective of the invention is to minimize the need for a seed latex. The earlier during the emulsion polymerization the seed latex is added, the less seed latex will be required. The seed latex may be added as soon as the average particle size of the emulsion polymer heing formed is twice the average particle size of the seed latex. Seed latex should not be added after 40 weight percent of the monomers have been converted during the emulsion polymerization. The preferred time of addition is between a monomer conversion of 2 and 30 weight percent.
The amount of seed latex to be added wi]l depend on the amount of emulsion pol~mer already forrned at the time of such addition, or rather at the time at which such addition is started. (The amount of the emulsion polymer can ~e equatect with sufficient accuracy with the amount o~ the monomers already charged.) The weight ratio between the synthetic resin particles of the seed latex and of the emu]sion polymer should range from 1:~ to 1:500 parts by weight. The weight ratio preferably ranges from 1:20 to 1:200 parts by weight. The greater the difference in siæe between the seed latex particles and the emulsion polymer particles already formed, and the earlier the addition of seed latex is started, the smaller that ratio can be. From the weight ratio indicated, it is seen that the amount of the seed latex should not be greater than 10 percent, by weight of the total amount of the monomers. The amount of the seed latex preferably is less than 5 weight percent, and highly preferably less than ~ weight percent, of the amount of the monomers. The see~ latex may be added all at once or in several portions, or more or less continuously over the conversion period indicated.
During polymerization of the monomers, the seed latex particles continue to grow along with the particles o-f the emulsion polymer. However, particles of different sizes do not grow exactly at the same rate. In the final product, the particles having the larger diameter account for the major portion of the weight of the dispersed synthetic resin, preferably from 60 to 95 weight percent~ while the small particles predominate numerically.
The aqueous phase initially consists of the amount oE water charged, in which emulsion polymerization is started, and is later augmented by the amount of water introduced with the seed la-teY~ and, if ~he monomers are used in the form of an aqueous emulsion, by the water content of the latter~
I'he amount of the water phase will depend on the desired so1ids content of the finished dispersion. The monomers may be added in the form of a 30 to 80 weight percent emulsion. When highly concentrated dispersions with solids contents greater than 65 percent are prepared, the monomers are preferably used in anhydrous form or at most with a small amount of water dissolved or emulsified therein. In that case, the amount of the aqueous phase is preferably limited to less than 70, and more particularly to from 40 to 60, parts by weight per lOO parts by weight of the monomers.
The aqueous phase in which the monomers polymerize contains a dissolved emulsifier and a dissol~ed initiator.
The emulsifier may be a single surface active substance or a mixture of several such substances.
The emulsifier may be charged to the water phase at the start. Additional amounts of emulsifier may be introduced with the monomer emulsion.
Optionally, an emulsifier may be dissolved in the monomers, or an aqueous emulsifier solution may be dispersed in them. As a rule, no new particles should form during the emulsion polymerization and none will form if the amount of emulsifier optionally added is chosen and is metered in a manner such that no free emulsifier, that is no emulsifier not adsorbed on the particle surface, is present.
The seed latex may contain the anionic, cationic, or nonionic low molecular weight emulsifiers of a surfactant nature whieh are commonly used with synthetic resin dispersions, or eompatible mixtures thereof, in -the usual amounts. The emulsifier systems of -the aqueous phase and oE
-the seed latex must, of course, be compatible with each other, whieh in case oE doubt should be aseertained in advanee. As a rule, an:ioni,e emulsifiers are eompat:ible with one another and with nonionie emulsifiers. This is true also of eationie emulsifiers, whereas anionic and eationie emulsifiers usually are not compatible with one another.
This should be borne in mind also when Eurther emulsifier is added. The coneentration of ionie emulsifiers in the final produet preferably ranges from 0.01 to 2 pereent by weight of the water phase.
The emulsifiers whieh are used alone or in admixture are those whieh are commonly used in emulsion polymeri~ation and are eomposed o~ a hydrophilic and a hydrophobie molecular portion. Their molecular weights usually are under 1,000. Water soluble polymers ha~ing higher moleeular weights are oeeasionally used eoneurrently as proteetive eolloids.
Commonly used emulsifiers contain long chain alkyl groups having from 8 to 22 carbon atoms, or aryl groups, and particularly alkyl substituted aryl groups sueh as nonylphenol or triisobutylphenol groups, as the hydrophobie molecular portion, and polyglyeol ether groups eomposed of from 3 to 100 ethylene oxide groups or propylene oxide groups as nonionic hydrophilic groups, or sulfonic acid groups, sulfuric acid half ester groups linked to polyglycol ether groups, phosphonic acid groups, or carboxyl groups as anionic groups, or quaternar~ ammonium salt groups as eationic groups. The products of addition of from 3 to 100 7~3 moles of ethylene oxide to nonylphenol or triisobutylphenol, their sulfuric acid half esters/ or their phosphoric a~id partial esters are typical of these kinds of emulsifiers.
The concentration of the emulslfier6 in the aqueous phase should only b~ hiyh enough for the ernulsifiers to be bound completely to the surface of the latex partic]es 50 that no free micelles are present which might form the seeds oE new particles. As a rule, from 0.01 to 2 percent of emulsifier, by weiyht of the aqueous phase, should be present during the polymerization. On completion of polymerization, nonionic emulsifiers are often added.
The preparation of genuine synthetic resin dispersions possessing the end use properties which are characteristic of these products requires that the polymerization be initiated by free radicals in the aqueous phase. The latter should therefore contain a dissolved initiator which decomposes to yield free radicals under the conditions of polymerization. Initiators are classed as thermal and redox initiators. The first of these classes comprises water soluble peroxygen compounds such as an alkali metal or ammonium persulfate, or water soluble azo compounds such as azo-bis-cyanovaleric acid or its salts.
They decompose at 50 to 100C~ and more particularly at 70 to 90C, to form free radicals initiating polymerization.
Redox initiators are formed of an oxidizing component, such as an alkali metal or ammonium persulfate or hydrogen peroxide, and a reduciny component, such as hydrogen sul-fite or a tertiary aromatic amine. The initiator is preferably used in an amount ran~ing from 0.01 to 0.5 percent by weiyht of the monomers.
~7~3 The emulsion polymeriza-tion may be initiated in the manner described in connec-tion with the preparation of the seed latex, wi-th fresh la-tex seeds then being forrned. However, i-t is also possible and of-ten preferred -to in-troduce a small amount of -the seecl:la-tex in-to -the ini-tially charged wa-ter phase even before -the start of emulsion polymeriza-tion. This method offers the advan-tage that the numerical ratio between -the large part:icle and -the srnall particle fractions of -the emulsion polymer can be prede-termined with a high degree of accuracy.
The monomers, as such or in the form of an aqueous emulsion, are added in the course of the polymerization, gradually and in keeping with the conversion, under polymerization conditions in such a way tha-t there will be no accumulation of large amounts of unconver-ted monomers. Uniform addition of the monomers over a period from 0.5 to 5 hours with stirring usually is advisable. The hea-t of polymerization evolved can be removed through the wa]l of the vessel by cooling.
The polymerization temperature is based on the decomposition charac-teristics of the initiator and is held at -the desired level by cooling. When therrnally decomposing initiators are used, the polymerization -temperature will usually range from 60 to ~0C. Redox initia-tor sys-tems are effective primarily in the range from 20 to 60C. Vigorous stirring during emulsion polymeriza-tion is advisable.
As soon as the latex particles have grown to a size bearing the desired rela-tion to the size of -the seed latex, addition of the latter is begun. The seed latex is preferably added all at once, but it may also be added over an extended period of -time or in ,.. .
_everal portions. However, addition of the seed latex should be comple-ted before more than 40 weight percent of the monomers have been added and polymerized. The monomer feed may, bu-t need no-t, be interrup-ted as the seed latex is added. Polyrnerization is continued unchanged after the seed latex addition. Monomer addi-tion is terminated before the average particle diame-ter of the larges-t particle family is larger -than 0.6,urn. On complet:ion of polymerization, stirring is preferably continued for a few hours under polymerization condi-tions. This may be followed by the steps usually -taken for the removal of residual monomers, for restabiliza-tion by the addition of further emulsii`ier, or for pH
adjustment.
Polymodal dispersions higher than bimodal will be formed by the process of the invention when the seed latex is added at -two or more distinctly separate times, or when a bimodal or polymodal dispersion is used as the seed latex.
A better understanding of the present invention and of its many advantages will be had by referring -to the following specific examples, given by way of illustration.
For use in these Examples, a seed latex was prepared as follows.
In a stainless steel reaction vessel having a capacity of lOO liters and equipped with a reflux condenser, stirrer, and feed vessel, 0.056 kg of ammonium persulfate and 0.56 kg of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium sal-t are dissolved at 80C in 34.2 kg of distilled water. An emulsion previously prepared from 2.772 kg of methyl methacrylate, 3.168 kg of butyl acrylate, 0.24 ky of methacrylic acid, 0.021 kg of the above emul~ifier, and 6 kg of distilled water is added dropwise to this solution at 80C within 60 minutes, with stirriny. An emulsion formed of 8.316 kg of methyl methacrylate, 9.504 kg of but~l acrylate, 0.063 kg of the above emulsifier, 0.028 kg of the above initiator, and 18 kg of distilled water is then metered in over a period of 3 hours. On completion of this addition, the batch is maintained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 29.5~, a pH of 2.5, a viscosity of 43 mPa.sec, and a particle size of 0.04~ micron is so obtained.
The particle diameters given here and in the Examples which follow for unimodal dispersions are average values determined by a special laser nephelometric method with due regard to Brownian molecular movementO This method of measurement is described in a publication of Coulter Electronics ~td. tl979) describing the Coulter "Nano-Sizer"
apparatus.
0A96 g of ammonium persulfate and 0.1 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles ethylene oxide which has been sulfated and converted to the sodium salt are dissolved in 320 g of distilled water in a 2-liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 828 g of butyl methacrylate, 354 g of butyl acrylate, 18 g of methacrylic acid, 10 g of the above emulsifier, 0.65 g of the above initiator, and 490 g of distilled water is added dropwise to this solution at vooC over a period of 4 hours, with stirring. 10 minutes after the start of this addition, 2 g of a 25% NH3 solution are added to -the dispersion and, within 10 minutes, 3 g of the seed latex are added, both wi-thout interruption of -the emulsion addl-tion. On comple-tion of -the addi-tion, -the ba-tch is main-tained a-t 80C for 2 hours and then cooled to room tempera-ture.
A coagula-te free dispersion having a solids conterlt of 59.9%, a pH of 5.8, and a viscosi-ty of 555 mPa.sec is so obtained.
With regard to the particle sizes, see Table I at -the end of these Examples.
0.042 kg of ammonium persulfa-te and 0.0028 kg of an emulsifier consisting of a reac-tion product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium sal-t are dissolved at 80C in 8.7 kg dis-tilled wa-ter in a stainless steel reaction vessel having a capaci-ty of 100 liters and equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 35.88 kg of bu-tyl methacrylate, 15.34 kg of butyl acrylate, 0.78 kg of methacrylic acid, 0.42 kg of the above emulsifier, 0.028 kg of the above initiator, and 16.7 kg of distilled water is added dropwise to this solution over a period of 5 hours, with stirring. 55 minutes after the start of this addition, 0.080 kg of a 25% NH3 solu-tion is added to the dispersion and, within 10 minutes, 0.80 kg of the seed latex is also added, without interruption of -the emulsion addition. On completion of the addition, the batch is maintained at 80C for 2 hours and then cooled to room -temperature.
~7~3 A coagulate free dispersion having a solids conten-t of about 67% and a viscosi-ty of 2,000 mPa.sec is so obtained. ~ th regard to the particle sizes, see Table I.
:L.05 g of ammonium persulfate, 2 g of the seed latex, and 0.07 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles o-f ethylene oxide which has been sulfated and conver-ted to -the sodium salt are dissolved in 650 g of distilled water in a polymerization vessel equipped as described in Example 1. A monomer/emulsifier mixture previously prepared from 897 g of bu-tyl me-thacrylate, 383.5 g of butyl acrylate, 19.5 g of methacrylic acid, and 10.5 g of the above emulsifier is added dropwise to this solution at 80C over a period of 4 hours, with stirring. 60 minutes after -the star-t of this addition, 2 g of a 25%
NH3 solution are added to the dispersion and, within lO minutes, 100 g of the finely divided seed latex are added, without interruption of the monomer addi-tion. On completion of the latter, 0.7 g of the above initiator is added and the batch is main-tained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 64.8%, a pH of 7.5 and a viscosity of l,lOO mPa.sec is so obtained.
With regard to particle sizes, see Table I.
Comparative example with seed latex addition af-ter polymeriza-tion of more than 40% of the monomers 1.2 g of ammonium persulfate and 0.1 g of an emulsifier consisting of a reac-tion product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium salt are dissolved 7~3.'~
at 80C in 738 g of distilled water in a 2 liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel.
A monomer/emulsifier mixture previously prepared rom 828 y of butyl methacrylate, 354 y of butyl acrylate, 18 g of methacrylic acid, and 12 g of the above emulsifier is added dropwise to this solution at 80C over a period of 4 hours, with stirring. 160 minutes after the start of this addition, 2 g of a 25% NH3 solution are added to the dispersion and, within 10 minutes, 120 g of seed latex are added, without interruption of the monomer addition. On completion of the addition, 0.8 g of the above initiator is added and the batch is maintained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 60.4~, a p~ of 6.3, and a viscosity of 230 mPa.sec is so obtained.
Following Tahle I shows that, with regard to particle size, with this method an unsatisfactorily small amount of finely dispersed polymer is formed notwithstanding the use of more seed latex.
-- TABLE I ~ ~3 Particle Particle size distribution of bimodal size**) dispersion*
of Finely dispersed Coarsely dispersed emulsion por-tion por-tion polymerArnount Size Amoun-tSize Example upon ~Wt.%) (micron) (Wt.%)(micron) No. addi-tion of seed latex (micron) 1 0.16 30 0.26 70 0.39 2 0.30 25 0.13 75 0.~5
In accordance with the invention, this object is achieved by adding the seed latex before more than 40 weight percent of the monomers have been polymerized. Further, the seed la-tex particles are smaller by a factor ranging from 2 -to 15 than are the particles already formed by emulsion polymerization. Finally, the amount of the synthetic resin particles in the seed latex is no-t grea-ter than 10 percent by weight of the monomers, and the ratio of -the weight of the particles to the weight of the monomers already polymerized ranges from 1:4 to 1:500.
The process of the invention permits the preparation of polymodal synthetic resin dispersions without major modification of -the usual processes whereby conventional synthetic resin dispersions having only one maximum in the particle size dis-tribu-tion curve can l~?s~ 3 prepared. A polymodal particle size dis-tribu-tion is achieved solely through the one--time or repea-ted addit:ion of relatively srna]l amounts of a seed latex a-t an early stage of -the emulsion polymerization. Compared with methods in which a second particle forma-tion phase is ini-tia-ted by renewed addi-t:ion of emu]sLfier, the process of -the inven-tion :is distinguished by rnore accura-te reproducibili-ty since -the number of the addi-tional seeds can be controlled very accurately through the amount of -the seed la-tex. In contrast -to processes in which subs-tantial amoun-ts or different types of seed la-tices are added in -the course of polymerization, the process of the inven-tion requires very little seed latex of only one type. The process of -the invention therefore is both simple and reliably reproducible.
The monomers which are subjec-ted to emulsion polymerization in accordance with the invention are difficultly soluble in water at least to a considerable extent, by which is mean-t a solubili-ty of less than 10 weight percent, and preferably of less -than 2 weigh-t percent, at 20C. The proportion of difficulty soluble monomers in the polymer must be sufficiently high for the emulsion polymer formed -to be insoluble in the water phase, at least under the conditions of polymerization, and to precipi-tate in the form of dispersed latex particles. When mixtures of monomers are po]ymerized, -they are preferably composed of at least 70 weigh-t percent, and highly preferably of at least 90 weigh-t percent, of difficul-tly soluble monomers.
Sui-table monomers include the alkyl es-ters of acrylic acid and methacrylic acid having from 1 to 20 carbon a-toms in -the alkyl group, styrene and its homologs, vinyl es-ters of lower carboxylic __ids, dienes, and lower alpha-olefins, for example. These will generally -form the pr:incipal monomers representing more -than 50 weight percen-t of the synthetic resin. S~li-ta~le modifying rnonomers which usually account for less than 50 weight percen-t of the synthetic resin are acryloni-trile and rne-thacrylon:i-trile, acrylarrlide and methacrylamide as well as N-rnethylol compounds and N-methylol ethers -thereof, hydroxyalkyl es-ters of acrylic acid and methacrylic acid, optionally ~uaternized aminoalkyl esters and aminoalkylamides of acrylic acid and me-thacrylic acid, unsaturated carboxylic acids such as acrylic acid and me-thacrylic acid, maleic, fumar:ic and itaconic acid, and the half es-ters of dibasic carboxylic acids, as well as maleic anhydride.
A preferred class of synthetic resins is formed predominantly, that is, to -the extent of 70 percent or more, of alkyl esters of acrylic acid and/or methacrylic acid or mixtures thereof and of styrene. The resins preferably contain a srnall amount of an alpha, beta-unsaturated carboxylic acid.
The seed latex is formed by an aqueous dispersion of synthetic resin particles free of radical forming ini-tiators, which are smaller by a factor ranging from 2 to 15 than the particles of the emulsion polynler a-t the time the seed latex is added. The seed latex particles have an average par-ticle size ran~ing from 0.01 to 0.2 micron, for example, and preferably from 0.02 to 0.1 micron.
The average particle size is the weigh-t average of -the particle diameter, as determined by the method of H. Lange, Kolloid-Zeitschrift and Zeitschrift fur Polymere 223, 24 (1968), for example. A modern method of measurement is based on measuremen-t of the variations in sca-ttered ligh-t due to the Brownian movemen-t of the la-tex particles in a laser beam, generally called photon correla-tion spectroscopy.
The seed latex is prepared conventionally by emulsion polymerization in an a~ueous phase containing an emulsifier. By the use of an emulsi~ier concentration close to or s]iyhtly above the critical micelle co~centration, a very large number oE small latex seeds is formed, which seeds, through appropriate monomer addition, are allowed to grow to a particle size in the above range. The monomers from which the seed latex is formed may be the same as those used in the emulsion polymerization in accordance with the invention. However, other monomers, selected by the criteria set forth above with respect to the aforesaid monomers, may also be used.
The seed latex may have a polymer content ranging from 20 to 50, and preferably from 30 to 40, percent by weight. Lower polymer contents increase the amounts required to be used: higher polymer contents are detrimental because of high viscosity and because of stabilization problems during preparation and storage. As a rule, the seed latex can be stored for an extended period of time and may be kept on hand for a great many production batches of the polymodal synthetic resin dispersion~
An important objective of the invention is to minimize the need for a seed latex. The earlier during the emulsion polymerization the seed latex is added, the less seed latex will be required. The seed latex may be added as soon as the average particle size of the emulsion polymer heing formed is twice the average particle size of the seed latex. Seed latex should not be added after 40 weight percent of the monomers have been converted during the emulsion polymerization. The preferred time of addition is between a monomer conversion of 2 and 30 weight percent.
The amount of seed latex to be added wi]l depend on the amount of emulsion pol~mer already forrned at the time of such addition, or rather at the time at which such addition is started. (The amount of the emulsion polymer can ~e equatect with sufficient accuracy with the amount o~ the monomers already charged.) The weight ratio between the synthetic resin particles of the seed latex and of the emu]sion polymer should range from 1:~ to 1:500 parts by weight. The weight ratio preferably ranges from 1:20 to 1:200 parts by weight. The greater the difference in siæe between the seed latex particles and the emulsion polymer particles already formed, and the earlier the addition of seed latex is started, the smaller that ratio can be. From the weight ratio indicated, it is seen that the amount of the seed latex should not be greater than 10 percent, by weight of the total amount of the monomers. The amount of the seed latex preferably is less than 5 weight percent, and highly preferably less than ~ weight percent, of the amount of the monomers. The see~ latex may be added all at once or in several portions, or more or less continuously over the conversion period indicated.
During polymerization of the monomers, the seed latex particles continue to grow along with the particles o-f the emulsion polymer. However, particles of different sizes do not grow exactly at the same rate. In the final product, the particles having the larger diameter account for the major portion of the weight of the dispersed synthetic resin, preferably from 60 to 95 weight percent~ while the small particles predominate numerically.
The aqueous phase initially consists of the amount oE water charged, in which emulsion polymerization is started, and is later augmented by the amount of water introduced with the seed la-teY~ and, if ~he monomers are used in the form of an aqueous emulsion, by the water content of the latter~
I'he amount of the water phase will depend on the desired so1ids content of the finished dispersion. The monomers may be added in the form of a 30 to 80 weight percent emulsion. When highly concentrated dispersions with solids contents greater than 65 percent are prepared, the monomers are preferably used in anhydrous form or at most with a small amount of water dissolved or emulsified therein. In that case, the amount of the aqueous phase is preferably limited to less than 70, and more particularly to from 40 to 60, parts by weight per lOO parts by weight of the monomers.
The aqueous phase in which the monomers polymerize contains a dissolved emulsifier and a dissol~ed initiator.
The emulsifier may be a single surface active substance or a mixture of several such substances.
The emulsifier may be charged to the water phase at the start. Additional amounts of emulsifier may be introduced with the monomer emulsion.
Optionally, an emulsifier may be dissolved in the monomers, or an aqueous emulsifier solution may be dispersed in them. As a rule, no new particles should form during the emulsion polymerization and none will form if the amount of emulsifier optionally added is chosen and is metered in a manner such that no free emulsifier, that is no emulsifier not adsorbed on the particle surface, is present.
The seed latex may contain the anionic, cationic, or nonionic low molecular weight emulsifiers of a surfactant nature whieh are commonly used with synthetic resin dispersions, or eompatible mixtures thereof, in -the usual amounts. The emulsifier systems of -the aqueous phase and oE
-the seed latex must, of course, be compatible with each other, whieh in case oE doubt should be aseertained in advanee. As a rule, an:ioni,e emulsifiers are eompat:ible with one another and with nonionie emulsifiers. This is true also of eationie emulsifiers, whereas anionic and eationie emulsifiers usually are not compatible with one another.
This should be borne in mind also when Eurther emulsifier is added. The coneentration of ionie emulsifiers in the final produet preferably ranges from 0.01 to 2 pereent by weight of the water phase.
The emulsifiers whieh are used alone or in admixture are those whieh are commonly used in emulsion polymeri~ation and are eomposed o~ a hydrophilic and a hydrophobie molecular portion. Their molecular weights usually are under 1,000. Water soluble polymers ha~ing higher moleeular weights are oeeasionally used eoneurrently as proteetive eolloids.
Commonly used emulsifiers contain long chain alkyl groups having from 8 to 22 carbon atoms, or aryl groups, and particularly alkyl substituted aryl groups sueh as nonylphenol or triisobutylphenol groups, as the hydrophobie molecular portion, and polyglyeol ether groups eomposed of from 3 to 100 ethylene oxide groups or propylene oxide groups as nonionic hydrophilic groups, or sulfonic acid groups, sulfuric acid half ester groups linked to polyglycol ether groups, phosphonic acid groups, or carboxyl groups as anionic groups, or quaternar~ ammonium salt groups as eationic groups. The products of addition of from 3 to 100 7~3 moles of ethylene oxide to nonylphenol or triisobutylphenol, their sulfuric acid half esters/ or their phosphoric a~id partial esters are typical of these kinds of emulsifiers.
The concentration of the emulslfier6 in the aqueous phase should only b~ hiyh enough for the ernulsifiers to be bound completely to the surface of the latex partic]es 50 that no free micelles are present which might form the seeds oE new particles. As a rule, from 0.01 to 2 percent of emulsifier, by weiyht of the aqueous phase, should be present during the polymerization. On completion of polymerization, nonionic emulsifiers are often added.
The preparation of genuine synthetic resin dispersions possessing the end use properties which are characteristic of these products requires that the polymerization be initiated by free radicals in the aqueous phase. The latter should therefore contain a dissolved initiator which decomposes to yield free radicals under the conditions of polymerization. Initiators are classed as thermal and redox initiators. The first of these classes comprises water soluble peroxygen compounds such as an alkali metal or ammonium persulfate, or water soluble azo compounds such as azo-bis-cyanovaleric acid or its salts.
They decompose at 50 to 100C~ and more particularly at 70 to 90C, to form free radicals initiating polymerization.
Redox initiators are formed of an oxidizing component, such as an alkali metal or ammonium persulfate or hydrogen peroxide, and a reduciny component, such as hydrogen sul-fite or a tertiary aromatic amine. The initiator is preferably used in an amount ran~ing from 0.01 to 0.5 percent by weiyht of the monomers.
~7~3 The emulsion polymeriza-tion may be initiated in the manner described in connec-tion with the preparation of the seed latex, wi-th fresh la-tex seeds then being forrned. However, i-t is also possible and of-ten preferred -to in-troduce a small amount of -the seecl:la-tex in-to -the ini-tially charged wa-ter phase even before -the start of emulsion polymeriza-tion. This method offers the advan-tage that the numerical ratio between -the large part:icle and -the srnall particle fractions of -the emulsion polymer can be prede-termined with a high degree of accuracy.
The monomers, as such or in the form of an aqueous emulsion, are added in the course of the polymerization, gradually and in keeping with the conversion, under polymerization conditions in such a way tha-t there will be no accumulation of large amounts of unconver-ted monomers. Uniform addition of the monomers over a period from 0.5 to 5 hours with stirring usually is advisable. The hea-t of polymerization evolved can be removed through the wa]l of the vessel by cooling.
The polymerization temperature is based on the decomposition charac-teristics of the initiator and is held at -the desired level by cooling. When therrnally decomposing initiators are used, the polymerization -temperature will usually range from 60 to ~0C. Redox initia-tor sys-tems are effective primarily in the range from 20 to 60C. Vigorous stirring during emulsion polymeriza-tion is advisable.
As soon as the latex particles have grown to a size bearing the desired rela-tion to the size of -the seed latex, addition of the latter is begun. The seed latex is preferably added all at once, but it may also be added over an extended period of -time or in ,.. .
_everal portions. However, addition of the seed latex should be comple-ted before more than 40 weight percent of the monomers have been added and polymerized. The monomer feed may, bu-t need no-t, be interrup-ted as the seed latex is added. Polyrnerization is continued unchanged after the seed latex addition. Monomer addi-tion is terminated before the average particle diame-ter of the larges-t particle family is larger -than 0.6,urn. On complet:ion of polymerization, stirring is preferably continued for a few hours under polymerization condi-tions. This may be followed by the steps usually -taken for the removal of residual monomers, for restabiliza-tion by the addition of further emulsii`ier, or for pH
adjustment.
Polymodal dispersions higher than bimodal will be formed by the process of the invention when the seed latex is added at -two or more distinctly separate times, or when a bimodal or polymodal dispersion is used as the seed latex.
A better understanding of the present invention and of its many advantages will be had by referring -to the following specific examples, given by way of illustration.
For use in these Examples, a seed latex was prepared as follows.
In a stainless steel reaction vessel having a capacity of lOO liters and equipped with a reflux condenser, stirrer, and feed vessel, 0.056 kg of ammonium persulfate and 0.56 kg of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium sal-t are dissolved at 80C in 34.2 kg of distilled water. An emulsion previously prepared from 2.772 kg of methyl methacrylate, 3.168 kg of butyl acrylate, 0.24 ky of methacrylic acid, 0.021 kg of the above emul~ifier, and 6 kg of distilled water is added dropwise to this solution at 80C within 60 minutes, with stirriny. An emulsion formed of 8.316 kg of methyl methacrylate, 9.504 kg of but~l acrylate, 0.063 kg of the above emulsifier, 0.028 kg of the above initiator, and 18 kg of distilled water is then metered in over a period of 3 hours. On completion of this addition, the batch is maintained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 29.5~, a pH of 2.5, a viscosity of 43 mPa.sec, and a particle size of 0.04~ micron is so obtained.
The particle diameters given here and in the Examples which follow for unimodal dispersions are average values determined by a special laser nephelometric method with due regard to Brownian molecular movementO This method of measurement is described in a publication of Coulter Electronics ~td. tl979) describing the Coulter "Nano-Sizer"
apparatus.
0A96 g of ammonium persulfate and 0.1 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles ethylene oxide which has been sulfated and converted to the sodium salt are dissolved in 320 g of distilled water in a 2-liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 828 g of butyl methacrylate, 354 g of butyl acrylate, 18 g of methacrylic acid, 10 g of the above emulsifier, 0.65 g of the above initiator, and 490 g of distilled water is added dropwise to this solution at vooC over a period of 4 hours, with stirring. 10 minutes after the start of this addition, 2 g of a 25% NH3 solution are added to -the dispersion and, within 10 minutes, 3 g of the seed latex are added, both wi-thout interruption of -the emulsion addl-tion. On comple-tion of -the addi-tion, -the ba-tch is main-tained a-t 80C for 2 hours and then cooled to room tempera-ture.
A coagula-te free dispersion having a solids conterlt of 59.9%, a pH of 5.8, and a viscosi-ty of 555 mPa.sec is so obtained.
With regard to the particle sizes, see Table I at -the end of these Examples.
0.042 kg of ammonium persulfa-te and 0.0028 kg of an emulsifier consisting of a reac-tion product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium sal-t are dissolved at 80C in 8.7 kg dis-tilled wa-ter in a stainless steel reaction vessel having a capaci-ty of 100 liters and equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 35.88 kg of bu-tyl methacrylate, 15.34 kg of butyl acrylate, 0.78 kg of methacrylic acid, 0.42 kg of the above emulsifier, 0.028 kg of the above initiator, and 16.7 kg of distilled water is added dropwise to this solution over a period of 5 hours, with stirring. 55 minutes after the start of this addition, 0.080 kg of a 25% NH3 solu-tion is added to the dispersion and, within 10 minutes, 0.80 kg of the seed latex is also added, without interruption of -the emulsion addition. On completion of the addition, the batch is maintained at 80C for 2 hours and then cooled to room -temperature.
~7~3 A coagulate free dispersion having a solids conten-t of about 67% and a viscosi-ty of 2,000 mPa.sec is so obtained. ~ th regard to the particle sizes, see Table I.
:L.05 g of ammonium persulfate, 2 g of the seed latex, and 0.07 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles o-f ethylene oxide which has been sulfated and conver-ted to -the sodium salt are dissolved in 650 g of distilled water in a polymerization vessel equipped as described in Example 1. A monomer/emulsifier mixture previously prepared from 897 g of bu-tyl me-thacrylate, 383.5 g of butyl acrylate, 19.5 g of methacrylic acid, and 10.5 g of the above emulsifier is added dropwise to this solution at 80C over a period of 4 hours, with stirring. 60 minutes after -the star-t of this addition, 2 g of a 25%
NH3 solution are added to the dispersion and, within lO minutes, 100 g of the finely divided seed latex are added, without interruption of the monomer addi-tion. On completion of the latter, 0.7 g of the above initiator is added and the batch is main-tained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 64.8%, a pH of 7.5 and a viscosity of l,lOO mPa.sec is so obtained.
With regard to particle sizes, see Table I.
Comparative example with seed latex addition af-ter polymeriza-tion of more than 40% of the monomers 1.2 g of ammonium persulfate and 0.1 g of an emulsifier consisting of a reac-tion product of triisobutylphenol and 7 moles of ethylene oxide which has been sulfated and converted to the sodium salt are dissolved 7~3.'~
at 80C in 738 g of distilled water in a 2 liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel.
A monomer/emulsifier mixture previously prepared rom 828 y of butyl methacrylate, 354 y of butyl acrylate, 18 g of methacrylic acid, and 12 g of the above emulsifier is added dropwise to this solution at 80C over a period of 4 hours, with stirring. 160 minutes after the start of this addition, 2 g of a 25% NH3 solution are added to the dispersion and, within 10 minutes, 120 g of seed latex are added, without interruption of the monomer addition. On completion of the addition, 0.8 g of the above initiator is added and the batch is maintained at 80C for 2 hours and then cooled to room temperature.
A coagulate free dispersion having a solids content of 60.4~, a p~ of 6.3, and a viscosity of 230 mPa.sec is so obtained.
Following Tahle I shows that, with regard to particle size, with this method an unsatisfactorily small amount of finely dispersed polymer is formed notwithstanding the use of more seed latex.
-- TABLE I ~ ~3 Particle Particle size distribution of bimodal size**) dispersion*
of Finely dispersed Coarsely dispersed emulsion por-tion por-tion polymerArnount Size Amoun-tSize Example upon ~Wt.%) (micron) (Wt.%)(micron) No. addi-tion of seed latex (micron) 1 0.16 30 0.26 70 0.39 2 0.30 25 0.13 75 0.~5
3 0.31 20 0.09 80 0.45 Comparative less more example 0.42 than 5 0.05-0.07 than 95 0.47 *) The particle size dis-tribution was determined by the ultracentrifuge method of W. S~holten and H. Lange, Kolloidzeitschrift and Zeitschrift fur Polymere 250 (1972) 782.
**) Determined by photon correlation spectroscopy 0.12 g of ammonium persulfate and 0.16 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles ethylene oxide which has been sulfated and converted to the sodium salt and 2.3 g of the seed latex are dissolved in 235 g of distilled water in a 2-liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 828 g of bu-tyl methacrylate, 354 g of butyl acrylate, 18 g of methacrylic acid, 12 g of the above emulsifier, 0.8 g of the above initiator, and 550 g of distilled water is added dropwise to this solution at 80C over a period of 4 hours, with s-tirring. 10 minutes af-ter the start of -this addition, 2 g of a 25% NH3 solution are added to the dispersion and, within 5 minutes, 2.3 g of -the seed la-tex are added, both without interruption of the emulsion addition.
30 minutes later a further amount of 23 g of the seed latex is added ~ 7~
.
vvithin 5 minutes. On completion of the emulsion addi-tion, the ba-tch is maintained at 80C for 2 hours and -then cooled -to room tempera-ture.
A coagulate free dispersion having a solids content of 60.2 percent b.w., a pH of 5.8, and a viscosi-ty of 650 mPa.sec ls so obtained. 30% of the par-ticles have a diameter of 0.135,um, 13% of 0.23,urn and 57% of 0.45~um, as determined by the ultracentrifuge me-thod.
**) Determined by photon correlation spectroscopy 0.12 g of ammonium persulfate and 0.16 g of an emulsifier consisting of a reaction product of triisobutylphenol and 7 moles ethylene oxide which has been sulfated and converted to the sodium salt and 2.3 g of the seed latex are dissolved in 235 g of distilled water in a 2-liter Witt jar equipped with a reflux condenser, stirrer, and feed vessel. An emulsion previously prepared from 828 g of bu-tyl methacrylate, 354 g of butyl acrylate, 18 g of methacrylic acid, 12 g of the above emulsifier, 0.8 g of the above initiator, and 550 g of distilled water is added dropwise to this solution at 80C over a period of 4 hours, with s-tirring. 10 minutes af-ter the start of -this addition, 2 g of a 25% NH3 solution are added to the dispersion and, within 5 minutes, 2.3 g of -the seed la-tex are added, both without interruption of the emulsion addition.
30 minutes later a further amount of 23 g of the seed latex is added ~ 7~
.
vvithin 5 minutes. On completion of the emulsion addi-tion, the ba-tch is maintained at 80C for 2 hours and -then cooled -to room tempera-ture.
A coagulate free dispersion having a solids content of 60.2 percent b.w., a pH of 5.8, and a viscosi-ty of 650 mPa.sec ls so obtained. 30% of the par-ticles have a diameter of 0.135,um, 13% of 0.23,urn and 57% of 0.45~um, as determined by the ultracentrifuge me-thod.
Claims (2)
- .AT IS CLAIMED IS:
l. A method for making an aqueous polymodal synthetic resin dispersion comprising at least two particle families of different average particle size the largest particle family having an average particle diameter of 0.6 um or less and the average particle size of the next smaller particle family being at most two thirds of the average particle size of the largest particle family, which method comprises a) gradually adding an ethylenically unsaturated monomer difficultly soluble in water or a mixture of ethylenically unsaturated monomers forming a polymer which is insoluble under the conditions of polymerization, as such or in the form of an aqueous emulsion to an aqueous phase containing an emulsifier and a water soluble polymerization initiator and having a temperature at which polymerization of said monomers is effected;
b) adding a seed latex containing synthetic resin particles to the polymerization mixture in the course of the polymerization before more than 40 weight percent of said monomers have been added, the particles of said seed latex being smaller by a factor ranging from 2 to 15 than are the particles already formed by emulsion polymerization of step a (the size of the particles being calculated as average particle diameters), the amount by weight of the particles in the seed latex being not greater than 10 percent by weight of the monomers and the ratio by weight of particles of said seed latex to the weight of the monomers already added being from 1:4 to 1:500;
- Page one of Claims -continuing the monomer addition under emulsion polymerization conditions after the addition of said seed latex and terminating said monomer addition and emulsion polymerization before the average particle diameter of the largest particle family is larger than 0.6 um. - 2. A method as in Claim 1 wherein said aqueous phase prior to the monomer addition contains an additional amount of said seed latex.
- Page two of Claims -
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3319340.1 | 1983-05-27 | ||
| DE19833319340 DE3319340A1 (en) | 1983-05-27 | 1983-05-27 | METHOD FOR PRODUCING BI- OR POLYMODAL AQUEOUS PLASTIC DISPERSIONS |
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| Publication Number | Publication Date |
|---|---|
| CA1217893A true CA1217893A (en) | 1987-02-10 |
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ID=6200077
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000455292A Expired CA1217893A (en) | 1983-05-27 | 1984-05-28 | Method for making polymodal aqueous synthetic resin dispersions |
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|---|---|
| US (1) | US4539361A (en) |
| EP (1) | EP0129699B2 (en) |
| JP (1) | JPS59227902A (en) |
| CA (1) | CA1217893A (en) |
| DE (2) | DE3319340A1 (en) |
| ES (1) | ES8502450A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3265276D1 (en) * | 1981-11-23 | 1985-09-12 | Agfa Gevaert Nv | Method for the preparation of stable aqueous dispersions of polymer beads and the use of these dispersions in photographic elements |
| DE3319340A1 (en) * | 1983-05-27 | 1984-11-29 | Röhm GmbH, 6100 Darmstadt | METHOD FOR PRODUCING BI- OR POLYMODAL AQUEOUS PLASTIC DISPERSIONS |
| US5169884A (en) * | 1985-07-10 | 1992-12-08 | Sequa Chemicals, Inc. | Coating compositions |
| US4686260A (en) * | 1985-07-10 | 1987-08-11 | Sun Chemical Corporation | Printing ink composition |
| US5177128A (en) * | 1985-07-10 | 1993-01-05 | Sequa Chemicals, Inc. | Paper coating composition |
| US5190997A (en) * | 1985-07-10 | 1993-03-02 | Sequa Chemicals, Inc. | Adhesive composition |
| US4616057A (en) * | 1985-07-10 | 1986-10-07 | Sun Chemical Corporation | Polymer emulsion containing an interpenetrating polymer network |
| US4683269A (en) * | 1985-12-18 | 1987-07-28 | Reichhold Chemicals, Inc. | Opaque binder system |
| US4954558A (en) * | 1986-08-22 | 1990-09-04 | S. C. Johnson & Son, Inc. | Resin-fortified emulsion polymers and methods of preparing the same |
| US4820762A (en) * | 1986-08-22 | 1989-04-11 | S.C. Johnson & Son, Inc. | Resin-fortified emulsion polymers and methods of preparing the same |
| US4839413A (en) * | 1986-08-22 | 1989-06-13 | S.C. Johnson & Son, Inc. | Resin-fortified emulsion polymers and methods of preparing the same |
| US5216065A (en) * | 1990-11-29 | 1993-06-01 | The Mead Corporation | Emulsion polymerization with large particle size |
| DE4213967A1 (en) * | 1992-04-29 | 1993-11-04 | Basf Ag | AQUEOUS POLYMER DISPERSION |
| DE4213968A1 (en) * | 1992-04-29 | 1993-11-04 | Basf Ag | AQUEOUS POLYMER DISPERSION |
| DE4213965A1 (en) * | 1992-04-29 | 1993-11-04 | Basf Ag | AQUEOUS POLYMER DISPERSION |
| DE4213969A1 (en) * | 1992-04-29 | 1993-11-04 | Basf Ag | AQUEOUS POLYMER DISPERSION |
| DE4213964A1 (en) * | 1992-04-29 | 1993-11-04 | Basf Ag | AQUEOUS POLYMER DISPERSIONS |
| DE4307683A1 (en) * | 1993-03-11 | 1994-09-15 | Basf Ag | Process for the preparation of an aqueous polymer dispersion |
| DE4332012A1 (en) * | 1993-09-21 | 1995-03-23 | Roehm Gmbh | PSA dispersions |
| US5914366A (en) * | 1993-11-24 | 1999-06-22 | Cytec Technology Corp. | Multimodal emulsions and processes for preparing multimodal emulsions |
| US5486576A (en) * | 1994-07-01 | 1996-01-23 | Rohm And Haas Company | Method for reducing microfoam in a spray-applied waterborne thermoset composition |
| JP3817738B2 (en) † | 1994-09-30 | 2006-09-06 | 日本ゼオン株式会社 | Copolymer latex and method for producing the same |
| US5506282A (en) * | 1994-12-06 | 1996-04-09 | Rohm And Haas Company | Method for providing maximum coating film gloss |
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1983
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1984
- 1984-05-18 DE DE8484105658T patent/DE3473151D1/en not_active Expired
- 1984-05-18 EP EP84105658A patent/EP0129699B2/en not_active Expired - Lifetime
- 1984-05-24 ES ES532781A patent/ES8502450A1/en not_active Expired
- 1984-05-25 JP JP59104890A patent/JPS59227902A/en active Pending
- 1984-05-28 CA CA000455292A patent/CA1217893A/en not_active Expired
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1985
- 1985-03-04 US US06/708,096 patent/US4539361A/en not_active Expired - Lifetime
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|---|---|
| JPS59227902A (en) | 1984-12-21 |
| US4539361A (en) | 1985-09-03 |
| EP0129699B1 (en) | 1988-08-03 |
| EP0129699B2 (en) | 1993-11-18 |
| ES532781A0 (en) | 1985-01-16 |
| DE3473151D1 (en) | 1988-09-08 |
| EP0129699A2 (en) | 1985-01-02 |
| EP0129699A3 (en) | 1986-06-25 |
| DE3319340C2 (en) | 1991-04-11 |
| ES8502450A1 (en) | 1985-01-16 |
| DE3319340A1 (en) | 1984-11-29 |
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