CA1282200C - Batchwise preparation of crosslinked, finely divided polymers - Google Patents

Batchwise preparation of crosslinked, finely divided polymers

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Publication number
CA1282200C
CA1282200C CA000533515A CA533515A CA1282200C CA 1282200 C CA1282200 C CA 1282200C CA 000533515 A CA000533515 A CA 000533515A CA 533515 A CA533515 A CA 533515A CA 1282200 C CA1282200 C CA 1282200C
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weight
parts
water
stage
pressure
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CA000533515A
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French (fr)
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Bernhard H. Nowakowsky
Juergen Beck
Heinrich Hartmann
Christos Vamvakaris
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BASF SE
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BASF SE
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • 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
    • C08F2/00—Processes of polymerisation
    • C08F2/04—Polymerisation in solution
    • C08F2/10—Aqueous solvent

Abstract

Abstract of the Disclosure: Crosslinked, finely divided, water-absorbing polymers are prepared in a batchwise pro-cess by copolymerization of 100 parts by weight of a monomer mixture of acrylic acid or methacrylic acid, each of which is neutralized with from 0 to 100 mol% of an alkali metal or ammonium base, or acrylamide, methacryl-amide or N-vinylpyrrolidone with, as a crosslinking agent, from 0.01 to 5 parts by weight of a monomer con-taining two or more ethylenically unsaturated double bonds in 20-80% by weight aqueous solution in the pre-sence of an initiator in a multistage procedure in a batchwise mixing apparatus with constant thorough mixing in all stages, in the first stage the aqueous monomer solution being copolymerized at from 45 to 95°C and under from 0.1 to 0.8 bar with removal of some of the water by distillation, in the second stage the copolymerization being completed at from 100 to 170°C under a pressure of up to 8 bar, and in the third stage the water content of the resulting finely divided copolymer being decreased to 0.5-10% by weight under reduced pressure.

Description

German Laid-Open Application DOS 3,432,690 dis-closes a process for the continuous preparation of cross-linked polymers, in which water-soluble monomers are polymerized in the presence of a crosslinking agent and of S initiators in a kettle which is equipped with a plurality of mutually parallel rotating stirrer shafts provided with stirrer blades. The polymerization is carried out conti-n~ously in a two-arm kneader or, for example, in a three-shaft kneader. The polymerization temperature is preferably from 70 to 100C. In this type of reactor, a high degree of back-rnixing ta~es place, so that the monomer solution is introduced onto the finely divided water-containing gel polymer and polymerization of the monomer takes place on the surface of the polymer gel. The finely divided polymer gels prepared in this manner have a relatively high residual monomer content and contain substantial amounts of extract-ables, i.e. soluble components. They therefore have to be subjected, in a separate process step, to after-polymeriza-tion and subsequent crosslinking.
It is an object of the present invention to provide a process for the preparation of crosslinked, finely divided, water-absorbing polymers, in which the polymers obtained have a low residual monomer content and small amounts of extractables.
We have found that this object is achieved, according to the invention, by a process for the batchwise preparation of crosslinked, finely divided, water-absorbing polymers by copolymerization of 100 parts by weight of a monomer from group a) or of a monomer mixture from groups:
a) 50-100 parts by weight of acrylic acid or methacrylic acid, each of which has been neutralized with from 0 to 100 mol% of an alkali metal or ammonium base, acrylamide, methacrylamide and N-vinylpyrrolidone, b) 0-30 parts by weight of other water-soluble mono-X

QO
- 2 - ~.Z. 0050/38353 ethylenically unsaturated monomers and c) 0-Z0 parts by weight of uater-insoluble monoethyleni-cally unsaturated monomers ~~
with from 0.01 to 5 parts by weight of, as a crosslinking agent, a monomer containing two or more ethylenically un-saturated double bonds, in 20-80% by weight aqueous solu-tion in the presence of an initiator at above 45C, if the copo(ymerization is carried out in several stages in a batchuise mixing apparatus with constant thorough mixing during all stages, in the first stage the aqueous monomer solution being co-polymerized at from 45 to 95C under from 0.1 to 0.8 bar with removal of some of the water by distillation, in the second stage the copolymerization being completed at from 100 to 170C under a pressure up to 8 bar and, in the third stage, after the pressure has been let down, the water content of the resulting finely divided co-poly~er being reduced to 0.5-10~ by weight under reduced press~re at from 70 to 180C or under atmospheric pressure at ~ro- 120 to 180C. The copolymerizat;on is prefer-ably carried out in a batchwise kneader having a self-purging effect of not less than 80X.
~ater-absorbing copolymers based on polymers of acrylic acid, methacrylic acid and their a~ides and on ZS N-vinylpyrrolidone are prepared by copoly~erization of the monomers together with a crosslinking agent. Suitable mono~ers of group a) are acrylic acid and/or methacrylic acid, each of which is neutralized with from 0 to 100 mol~O
of an alkali metal or ammonium base. This group of mono-mers also includes acrylamide, methacrylamide and N-vinylpyrrolidone. For the partial or complete neutrali-zation of the acrylic acid or methacrylic acid, sodium hydroxide solution and/or potassium hydroxide solution are preferably used. Neutralization can of course also be carried out using sodium carbonate, patassium carbonate, ammonia or a substituted amine, ,uch as trimethylamine, tri-n-oc~ylamine or triethanolamine. Where acrylic acid 1~82~:00 - 3 - O.Z. 0050/38353 or methacrylic acid is used for the polymerization, neutralization may be effected before, during or after the polym~rization. ~n the copolymerization with the cross-linking agents, the monomers of group a) can be used either alone or as a mixture with one another in any ratio. For example, acrylic acid alone or mixtures of acrylic acid and methacrylic acid or of acrylic acid and acrylamide or of acrylic acid, acrylamide and methacryla-mide or mixtures of acrylamide and N-vinylpyrrolidone may be subjected to copolymerization. However, acrylic acid which has been neutral;zed with from S0 to 100 mol~
of sodium hydroxide solution and/or potassium nydroxide solution is preferably used as the monomer of group a).
Neutralization of the acrylic acid is preferably effected before the polymerization or during the first stage of the polymerization. The monomers of group a) can be co-polymerized with the crosslinking agent either alone or as a mixture with the monomers of groups b) and c~. In the case of mixtures of monomers from groups a) to c), the amount of monomers of group a) is from S0 to 99~.
The monomers of group b) consist of other water-soluble, monoethylenica(ly unsaturated monomers which differ fro~ the monoaers o~ group a). These include, ~or example, male;c acid, fumaric acid, crotonic acid, Z5 itaconic acid, ~inylsulfonic ac;d, vinylpyridinium salts, N-vinylfor~amide, basic acrylates and methacrylates in the form of the salts with strong mineral acids or in quaternized form, eg. dimethylaminoethyl acrylate, di-ethylaminoethyl acrylate, dimethylaminopropyl acrylate, dimethylaminobutyl acrylate, diethylaminoethyl methacry-late, dimethylaminoethyl methacrylate and dimethylamino-propyl acrylate. This group of monomers also includes the hydroxyalkyl acrylates and hydroxyalkyl methacrylates, eg. hydroxyethyl acryLate, hydroxyethyl methacrylate, hydroxypropyl acrylates, hydroxypropyl methacrylates, hydroxybutyl acrylates and hydroxybutyl methacryLates, as ~ell as acrylates and methacrylates ~hich were obtained - 4 - O.Z. 0050/38353 by esterificati-on of polyethylene glycols with acrylic acid or methacrylic acid in a molar ratio of 1:1. The polyethylene ~ycols used for the esterificat;on have molecu~ar weights of from 126 to 8,500. From 0 to 3û, preferably from 0.5 to 15, parts by weight of -the mono-mers of group b) are used per 100 parts by weight of the monomers of group a).
~ he monomers of group c) include water-insoluble monoethylenically unsaturated monomers. These are, for example, the esters of acrylic acid or methacrylic acid with monohydric alcohols of 1 to 18 carbon atoms, eg.
methyl acrylate, ethyl acrylate, propyl acrylate, iso-propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, the corresponding esters of methacrylic acid, diethyl fumarate, diethyl maleate, dimethyl maleate, dibutyl maleate, acrylonitrile, methacrylonitrile, vinyl acetate and vinyl propionate. From 0 to 20, preferably from 0.5 to 5, parts by ~eight of the onomers of group c) are used per 100 parts by weight of the monomers of group a) in the copolymerization.
The crosslinking agents used are compounds which contain two or mor- ethylenically unsaturated double bonds.
Examples of suitable crosslinking agents are N,N'-methy~-lenebisacrylamide, polyethylene glycol diacrylates andpolyethylene glycol dimethacrylates, each of ~hich is derived from a polyethylene glycol with a molecular weight of from 126 to 8,500, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, butanediol diacrylate, 3¢ hexanediol diacrylate, hexanediol dimethacrylate, diacry-lates and dimethacrylates of block copolymers of ethylene oxide and propylene oxide, adducts of ethylene oxide and/
or propylene oxide with trimethylolPropane which have been diesterified or triesterified with acrylic acid or methacrylic acid, glycerol or pentaerythritol which have been diesterified or polyesterified with acrylic acid or methacrylic acid, triallylamine, tetraallylethylenediamine, - 5 - O.Z. 0050/38353 divinylbenzene, diallyl phthalate, polyethylene glycol divinyl ether, trimethylolpropane diallyl ether, poly-ethylene glycol divinyl ether, butanediol divinyl ether, polyethylene glycol diallyl ether, butanediol d;allyl ether and divinylethylene urea. The crosslinking agents are used in the copolymerization in an amount of from 0.01 to 5, preferably from 0.1 to 3, parts by ~eight per 100 parts by weight of the monomers of groups a) to c).
The monomers are polymerized in a~ueous solution.
The water-insoluble monomers, which -may or may not be present, are usually finely dispersed in the aqueous solu-tion with the aid of emuLsifiers. Examples of suitable emulsifiers are oxyethyLated nonylphenols, oxyethylated castor oil, alkylsulfates, sorbitan fatty acid esters, oxyethylated sorbitoLs, oxyethylated sorbitan fatty acid esters and alkylsulfonates. The emulsifiers are used in an amount of from 0 to 3 parts by weight per 100 parts by ~eight of the monomers of groups a) to c). The concen-tration of the a~ueous monomer so~ution is preferably from 30 to 50~ by ueight.
SuitabLe initiators are, in the main, water-so~uble co~pounds ~hich form free radicals, for example azo initiators, such as 2,2'-azobis-tN,N'-dim-thyleneiso-butyramidine) dihydroch~oride, 2,2'-azobis-(2-amidino-propane) dihydrochloride, 2,2'-azobis-(N,H'-dimethylene-isobutyramidine), 4,4'-azobis-(4-cyanopentanecarboxylic acid) and 2-carbamylazoisobutyronitrile, and dibenzoyl peroxide, dilauryl peroxide, di-2-ethylhexyl Peroxydicar-bonate, dicyclohexyl peroxydicarbonate, bis-(4-tert-butylcyclohexyl) peroxydicarbonate, tert-butyl perpiva-late, tert-butyl perbenzoate, tert-butyl Permaleate, di-tert-butyl Peroxide~ tert-buty~ hydroperoxide, hydrogen peroxide, ammonium persulfate, potassium persu~fate, sodium persulfate and redox catalysts, suitable reducing components being irontII) ammonium sulfate, ascorbic acid, sodium hydroxymethanesulfinate, disodium disulfite and sodium bisulfite. The initiators can be used either alone -` ~2B~
- 6 - o.z. 0050/38353 or as a mixture; The rate of decomposition of the per-oxides, ~hich undergo rapid decomposition, can be reduced by the concomitant use of organic metal compLexes, eg.
copper acetylacetonate, so that the rate of decomposition of the peroxides can be adapted to the particular polymeri-zation temperature chosen. Redox catalysts consisting of one or more peroxides and of a reducing agent are pre-ferably used, a persulfate or perester or a mixture of a persulfate and a perester particuLarly preferably being used as a component of redox polymerization initiators.
The polymerization initiators are used in an amount of from 0.01 to 5, preferably from 0.2 to 3, ~ by weight, based on the monomers emp~oyed in the polymerization.
In order to regulate the molecular weight of the polymers, polymerization may also be carried out in the presence of a polymerization regulator, eg. mercapto-ethanol, mercaptopropano(, thiog~ycollic acid, dodecyl-mercaptan, formic acid or a halohydrocarbon, such as bromomethane or carbon tetrachloride. The polymerization regulators are used in an amount of from 0 to 3X by w-ight, based on the monomers employed in the polymeriza-tion.
According to the invention, copolymerization of the aqueous solution of the monomers is carried out in Z5 several stages in a batchuise mixing apparatus with con-tinuous thorough mixing of the substances during all stages. Since, in the course of the polymerization, the aqueous monomer solution is converted to a finely divided polymer via gel-like material, vigorous mixing must be 3Q ensured in a~ stages of the process. Examples of suit-able batchwise mixing apparatuses are kneaders which have a seCf-purging effect of not less than 80%. The kneaders may have one or more scre~s. The copolymerization can also advantageously be carried out in a single-screw cy~indrical mixer whose stirrer shaft has disk segments which, on the outer end, possess mixing bars in an arrange-ment such that intensive circulatory mixing of the - 7 - O.Z. 0050/38353 substances introduced into the ~i~e~ is effected. The single-screw cylindrical mixer has a diameter/length ratio of from 2:1 to 20:1. The disk segments are arranged in the form of a propeller on the stirrer shaft. From 2 to 2S of these disk segments are distributéd over the entire length of the stirrer shaft, a disk segment con-sisting of from 2 to 7 individual elements arranged in a propeLler-like ~anner. The mixing elements located on the outer end of the disk segments transport the polymeriz-ing mixture inside the mixing apparatus and at the sametime prevent polymer gel from being deposited on the internal wall of the mixer, because the mixing elements run close to the internal waLl of the cylindrical ~ixer Examples of suitable mixing elements are mi~ing bars which pass close to the wall or ploughshare-like attach-ments. The mixer also contains built-in flanged counter-hooks for removing the gel formed during the polymeriza-tion from the disk segments of the stirrer shaft and from the ~ixing bars. Such mixing apparatuses too have a self-purging effect of more than 80X. Suitable appara-tuses having a high self-purging effect are known and are described in, for examPle, Che-.-Ing.-Techn. 57 (1985), 1005.
The apparatuses uhich are suitable for po~ymeri-2ation are charged with the aqueous monomer so~ution whichmay contain a dissolved or dispersed initiator, the charge occupying not ore than 45, preferably from 20 to 35, by vo~ume of the said apparatuses. The polymerization apparatuses can, if required, be heated or cooled and are designed for operation under reduced and SuPeratmos-pheric pressure.
In the first stage of the copolymerization, the aqueous monomer solution is copolymerized in the Presence of a po(ymeri2ation initiator at from 45 to 95C under from 0.1 to 0.8 bar with removal of some of the water by dis-tillation. The water evaporated is removed from the mixer via a pressure-regulating apparatus. By distilling off ~8 ~ ~
- 8 - O.Z. 0050/38353 the water under-reduced pressure, it is possible to set the po~ymerization temperature exactly and to re~ove the heat of polymerization from the system in this manner.
In the first stage of the poly~erization, water is dis-tilled off in an amount suffic;ent to give a polymer gelof about 30-90X strength by weight, which can be converted to a crumb-like gel as early as the end of the first stage.
The duration of polymerization of the first stage is about 5-60 ninutes.
In the second stage of the copolymerization, the temperature of the reaction mixture is increased to 100-170C, preferably 120-140C. This means that, because of the water content of the polymerizing mixture, the pressure in the apparatus increases to about 1-8, preferably 2-5, bar. The polymerization is completed in the second stage.
In this stage of the process too, the reaction mixture must be thoroughly mixed and subjected to shearing. The heat treatment of the copolymer in the second stage lasts for about 10-100, preferably 15-50, minutes. After this treat-~ent, the pressure is brought to atmospheric pressure.
In the third stage of the copolynerization, like-~ise under constant thorough oixing of the reaction ~ix-ture, uhich ha~ becooe crù-b-like, the water content of the resulting finely divided copolymer is reduced to 0.5-10, preferably 3-6, X by weight at fro~ 70 to 180C and under reduced pressure. The pressure under which the co-poly~ers are dried is of course temperature-dependent and is fro~ 1û to 800 mbar. The duration of drying is about 10-100 oinutes. The crosslinked copolymer can, however, also be dried under atmospheric pressure at from 120 to 180C.
This procedure gives a free-flowing finely divided polyner which has very high water absorption and is used, for exanple, as a soil conditioner or as an absorbent in hygiene articles, for examPle diapers. In the Examples, parta and percentages are by weight, unless stated other-wise.

~28;2200 - 9 - O.Z~ 0050/38353 Determination of the absorptivity of the polymers In the Exa~ples, the absorptivity of each of the po~y~ers prepared for physiological saline is given.
~his vas determined by enclosing 0.2 9 of each polymer in S a teabag-like filter paper bag and immersing it for 10 minutes in 0.9X strength aqueous saline. After subtract-ing the amount absorbed by the empty bag, the absorptivity of the polymer was calculated in each case.
Determination of soluble components The content of soluble components not bound in the polymer net~ork was determined by swelling the polymer for 8 hours in water and measuring the carbon content of the aqueous solution.

A monomer solution ~hich is at 20C and consists of 500 parts of acrylic acid, 6 parts of N,N'-methylene-bisacrylamide and 120 parts of ~ater is initially taken under nitrogen in a 6 l single-scre~ cylindrical mixer ~hose stirrer shaft possesses disk segments ~hich have mixing bars on the outer end in an arrangement such that thorough circulatory mixing of the content is achieved, the charge occupying 35~ of the mixer capacity. The mixer has a diameter/~ength ratio of 7:1 ànd is designed to operate under redueed and superatmospheric pressure. 8 disk segments are arranged 15 c~ apart on each stirrer shaft of the mixer, a disk segment consisting of three individual elements. 150 parts of 50% strength aqueous sodium hydroxide solution are then~added to the constantly and thoroughly stirred monomer solution in order to neu-tralize 27% of the acrylic acid. During the neutraliza-tion, the reaction mixture is cooled to 30C. Thereafter, S parts of ammonium peroxydisu~fate in 25 parts of ~ater are mixed in. The stirrer shaft and housing of the single-screw mixer are heatable and are brought to 45C, ~hile the pressure inside the mixer is brought to 200 mbar.
The polymeri2ation reaction is then started by add~ng 1 part of sodium bisulfite in 10 parts of ~ater. At the ~ O
- 10 - o.z. OOS0/38353 same time, 300 parts of a 50% strength aqueous potassium hydroxide solution are added in the course of 10 minutes.
The temperature of the reaction mixture increases to 72C.
During the polymerization, 270 parts of water are dis-tilled off. The polymerization in the first stage lastsZS minutes. In the second stage of the polymerization, the pressure is first equilibrated to 1 bar under a nitrogen atmosphere, the mixer is then cLosed so that it is pressure-t;ght, and the reaction mixture therein is heated to 135C. This increases ~he pressure in the mixer to 4 bar. The reaction mixture is treated for 20 minutes at this temperature and under pressure, while stirring constantly and thoroughly. After the pressure has been brought to atmospheric pressure, the water con-tent of the resu(ting copolymer is reduced to Z.8~ in thethird stage, under 50 mbar and at 140C, with constant thorou~qh ~ixing. The pressure is then brought to atmos-pheric pressure. A crosslinked, finely divided water-absorbing polymer can then be removed from the mixer.
The mean particle diameter of the polymer is 3 mm. 1 9 of the polymer absorbs 61 9 of physioLogica~ saline. By swelling in water, it is Possible to extract about 9X of soluble components.

In the oixer described in Exanple 1, in which the charge occupies 3ûX of the capacity, a solution of 300 parts of acrylic acid, 100 parts of àcrylamide, 35 parts of H-vinylpyrrolidone and S parts of butanediol divinyl ether in 150 parts of water is partially neutralized with 220 parts of SOX aqueous potassium hydroxide solutian under nitrogen and with continued stirring, the tempera-ture being restricted to 30C by cooling. A solutian of 5 parts of potassium peroxydisulfate in 150 parts of water is ~ixed in, the stirrer shaft and the housing of the single-screw mixer are heated to 45C and the inter-nal pressure of the mixer set to 400 bar. Polymerization is initiated by adding 0.5 part of sodium hydroxymethane-~82;~0 ~ o.Z. 0050/38353sulfinate in 5 parts of water. During the 15 minute poly-merization, 120 9 of Sû% strength aqueous potassium hyd-roxide soLution are added and 260 parts of water are re-moved. The temperature of the reaction mixture increases S to 83C. In the second stage, the pressure is equilibra-ted to 1 bar with nitrogen, the mixer is closed tightLy and the reaction mixture is then heated to 120C, the pres-sure in the mixer increasing to about 3 bar. The con-stantty stirred reaction mixture is aftertreated for 20 minutes under these conditions. Finally, in the third stage, the pressure is equilibrated to atmospheric pres-sure and then reduced to 30 mbar, and the resulting co-poLymer is dried at 150C with thorough stirring to give a fine crumb-!ike material. The mixer is brought to atmospheric pressure, after which a crossLinked, finely divided water-absorbing Polymer having a mean particle diameter of 3 mm can be removed. 1 9 of the polymer absorbs 54 9 of physioLogical saLine. By sweLLing in ~ater, it is possible to separate off about 7X of soLubLe co~ponents.

In the single-shaft mixer described in ExampLe 1, in uhich the charge occuPies 40X of the capacity, a stirred solution of 250 parts of acrylic acid, 40 parts of ~ethacrylic acid, 43 parts of itaconic acid, 7 parts of divinylben2ene and 7 parts of sodiu~ pentadecylsul-fonate in 250 parts of water is partiaLty neutraLized with 230 parts of S0~ strength a~ueous potassium hydrox-ide soLution under nitrogen, and the temperature of the solution is kept at 30C during this procedure by remov-ing heat. After the addition of a soLution of 10 parts of sodium peroxydisulfate in 50 parts of ~ater, the stirrer shaft and housing of the singLe-shaft mixer are heated to 45C, the mixture is evacuated to 300 mbar and the poLymerization is initiated by adding O.S parts of ascorbic acid in 30 parts of water. The reaction mixture reaches 72C during the 25 minute polymerization in this - 12 - O.Z. 0050/38353 f;rst stage. 230 parts of water are distilled off. For the second stage of the polymerization, the pressure is equilibrated to 1 bar with a nitrogen atmosphere, the mixer is closed so that it is pressure-tight and the reaction mixture is heated to 130C, the pressure building up to about 3.5 bar. Aftertreatment is carried out at this temperature and under this pressure with thorough mixing for 35 minutes. Thereafter, the temperature is decreased to 60C, the pressure is reduced to atmos-pheric pressure and subsequent neutralization is carriedout with 120 parts of 50% strength aqueous potassium hy-droxide solution with thorough mixing of the polymer.
In the third stage, the pressure is reduced to 20 mbar and drying is carried out at 120C to a residual water con-tent of 5.2X to give a finely divided solid having a meanparticle diameter of 3 mm.
1 9 of the resulting copolymer absorbs 58 9 of physiological saline. ay swelling ;n water, it is Po bLe to extract about 7X of soluble components.

Claims (4)

1. A process for the batchwise preparation of a crosslinked, finely divided, water-absorbing polymer, which comprises multistage copolymerization in a batch-wise mixing apparatus, with constant thorough mixing in all stages, of 100 parts by weight of a monomer from group a) or of a monomer mixture from groups a) 50-100 parts by weight of acrylic acid or methacrylic acid, each of which has been neutralized with from 0 to 100 mol% of an alkali metal or ammonium base, acrylamide, methacrylamide and N-vinylpyrrolidone, b) 0-30 parts by weight of other water-soluble mono-ethylenically unsaturated monomers and c) 0-20 parts by weight of water-insoluble monoethyleni-cally unsaturated monomers with from 0.01 to 5 parts by weight of, as a crosslinking agent, a monomer containing two or more ethylenically un-saturated double bonds, in 20-80% by weight aqueous solu-tion in the presence of an initiator at above 45°C, in the first stage the aqueous monomer solution being co-polymerized at from 45 to 95°C under from 0.1 to 0.8 bar with removal of some of the water by distillation, in the second stage the copolymerization being completed at from 100 to 170°C under a pressure up to 8 bar and, in the third stage, after the pressure has been let down, the water content of the resulting finely divided co-polymer being reduced to 0.5-10% by weight under reduced pressure at from 70 to 180°C or under atmospheric pressure at from 120 to 180°C.
2. A process as claimed in claim 1, wherein the batchwise mixing apparatus used is a kneader having a self-purging effect of not less than 80%.
3. A process as claimed in claim 1, wherein acrylic acid, which has been neutralized with from 10 to 100 mol%
of sodium hydroxide solution and/or potassium hydroxide solution, is copolymerized with a monomer containing two or more ethylenically unsaturated double bonds.

- 14 - 0.2. 0050/38353
4. A process as claimed in claim 1, wherein N,N'-methylenebisacrylamide, polyethylene glycol diacrylates, polyethylene glycol divinyl ether, butanediol divinyl ether, trimethylolpropane triacrylate, butanediol diacry-late, polyethylene glycol diallyl ether and/or butanediol diallyl ether are used as crosslinking agents.
CA000533515A 1986-03-21 1987-03-17 Batchwise preparation of crosslinked, finely divided polymers Expired - Lifetime CA1282200C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863609545 DE3609545A1 (en) 1986-03-21 1986-03-21 METHOD FOR THE DISCONTINUOUS PRODUCTION OF CROSSLINKED, FINE-PARTICLE POLYMERISATS
DEP3609545.1 1986-03-21

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CA1282200C true CA1282200C (en) 1991-03-26

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EP (1) EP0238050B1 (en)
JP (1) JPS62227904A (en)
AT (1) ATE46913T1 (en)
AU (1) AU590693B2 (en)
CA (1) CA1282200C (en)
DE (2) DE3609545A1 (en)

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