CA1203039A - Water-absorbent resin having improved water- absorbency and improved water-dispersibility and process for producing same - Google Patents
Water-absorbent resin having improved water- absorbency and improved water-dispersibility and process for producing sameInfo
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- CA1203039A CA1203039A CA000417618A CA417618A CA1203039A CA 1203039 A CA1203039 A CA 1203039A CA 000417618 A CA000417618 A CA 000417618A CA 417618 A CA417618 A CA 417618A CA 1203039 A CA1203039 A CA 1203039A
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- water
- absorbency
- absorbent resin
- resin
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
- C08L33/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
-
- 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
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
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- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Epidemiology (AREA)
- General Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Dispersion Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
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- Veterinary Medicine (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Absorbent Articles And Supports Therefor (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Water-absorbent resins having improved water-absorbency, water-absorption rate and water-dispersibil-ity can be produced by crosslinking a water-absorbent resin comprising a carboxylate as a constituent of the resin with a crosslinking agent having at least two functional groups in the presence of water in a propor-tion of 0.01 to 1.3 parts by weight per part by weight of the resin in an inert solvent.
Water-absorbent resins having improved water-absorbency, water-absorption rate and water-dispersibil-ity can be produced by crosslinking a water-absorbent resin comprising a carboxylate as a constituent of the resin with a crosslinking agent having at least two functional groups in the presence of water in a propor-tion of 0.01 to 1.3 parts by weight per part by weight of the resin in an inert solvent.
Description
~q~y~
1 This invention relate~ to a water absorbent resin having an improved dispersibility in water and an improved water absorbency, and a process.for producing the water absorbent resin~ More particularly, it rela-tes to a process for producing a water-absorbent resin having an improved water-absorbency and an improved water-dispersibility which compri~e~ crosslinking a water-absorben~ resin comprising a carboxylate as a constituent of the resin with a crossLinking agent having at least two functional groups in the presence of water in an inert solventO
Water absorbent resins are used in the field of sanitation as menstrual articies, diapers~ disposable house-clo~hs and the like and in the field of agriculture 15 and horticulture as water retentive materials. Further, they are useful in other various fields such as coagula-tion of sludges, prevention of dew condensation on construction materials, dehydration of oils and so on.
As this type of water a~sorbent resin, there are known 20 crosslinked carboxymethyl cellulose, partially cross-linked polyethylene oxide9 crosslinked hydrolyzates of starch-acrylonitrile graft copolymer, partially cross~
linked polyacrylic acid salts: and the like However, all of them have disadvantages that they have low water-~)3~
1 absorbency, and even if ~he water-absorbency is satis-factory, the water-dispersibility is inferior or the water-absorbing rate is low.
If these disadvantages are overcome, it is clear that the water absorbent resins will be more broadly used in various fields including sanitary articles ~uch as sanitary napkins9 paper diapers, under-pads, and the like, and it has been desired that improved articles come into the market.
As the water-absorbent resin, there are known various synthetic resins as mentioned above.
Particularly, Japanese Patent Application Kokai (Laid-Open) Nos; 93,716/81; 131,608/81 and 147,806/81 disclo5e methods for producing water-absorbent resins using as lS the starting material acrylic acid, which are commer cially easily available and ar~ uniform in quality.
These water-absorbent resins have an improved water-absorbency even in an aqueous electrolyte solution and an improved stabili~y in the wa~er-ab~orbed state~
However, th~se water~absorbent resins are still unsatis-factory in dispersibility in water and water-absorbing rate. Moreover, European Patent Application No.
80304099.7 (Publication No~ 0036463) and U.S. Patent No, 4,340,706 disclose that a water-absorbent resin suitable for usages requiring a stability in the fluid absorbed state for a long period of time or a high water-absorbing rate can be obtained by crosslinking an ~1 3~
1 acrylic acid salt polymer with a crosslink.ing agent.
However, even the resin obtained by said method i5 still not sufficient in water-dispersibility and water absorption rate.
The present inventors have further made research on the conditions ~or crosslinking water-absorbent resins with a crosslinking agent. As a result, it has surprisingly and unexpectedly been found that when a water-absorbent resin comprising a car-boxylate as its constituent is cros~linked with a crosslinking agent having at least two functional groups in the presence o~ a specific amount of water in an inert solvent, the water-dispersibility and the water-absorption rate can bo~h be greatly improved while retaining its water-absorbency as i~ is.
According to thi~ invention, there is provided a process for producing a water-absorbent resin having an improved water-absorbing rate and water-dispersibility, characterized by crosslinking a water-absorbent resin comprising a carboxylate as a consti-tuent of the resin with a crosslinking agent having at least two functional groups in the pre~ence of water ln a proportion of 0.01 to 1.3 parts by weight per part by weight of the resin in an inert solvent, The water-absorhent resins used in this inven-tion may be a~y polymer or copolymer comprising a car-boxylate as its con~ti~uentO Among the polymers or 3~
copol~Mers, there may preferably be used those co~pr sing an alkali metal acrylate or an alkali metal methacrylate as their constituent and those comprising a carboxyla~e and a hydroxyl group as their constituents~
As said water-absorbent resin, there may be used crosslinked polyacrylic acid salts, crosslin]ced copolymers of acrylic acid salts and methacrylic acid salts, crosslinked saponification products of methyl acrylate-vinyl acetate copolymer, crosslinked saponification products of starch~ethyl acryla~e graft - copolymer, crosslinked starch-acrylic acid salt graft copolymer, crosslinked saponification products of starch-methyl methacrylate graft copolymer, crosslinked saponification products of starch-acrylamide graf~ copolymer, crosslinked saponification products of starch-acrylonitrile-2-acrylamide-2-methylpropane sulfonic acid graft copolymer, crosslinked saponification products of starch-acrylonitrile graft copolymer, crosslinked sa~onification products of starch-acrylonitrile-vinylsulfonic acid graft copolymer, polyethylene oxide crosslinked with acrylic acid, crosslinked sodium carboxymethyl cellulose, and the like.
The water-absorbent resins comprising a carboxylate as its constituent can be produced by the methods disclosed in Japanese Patent Application Kokai (Laid-Open) Nos. 93,716/81; 131,608/81; and 147,806/81 as referred to above as well as the methods disclosed in 1~
~ 4 -~2~
1 Japanese Patent Publication Nos. 30,710/79; 37,994/79;
and 46,200/78 and U.S.P. 4,041,22~. Representative methods for producing the ~ater-absorbent resins which may be used as the startlng materials are as follows:
Method 1 An aqueous solution of acrylic acid and alkali acrylate is suspended in an alicyclic or aliphatic hydrocarbon solvent containing a surfactant having an HLB of 8 to 12 and polymerized in the presence of a water~soluble radical polymerization initiator.
Method 2 To the polymeri~ation reaction product obtained by the same way as in Method 1 is added a poly-functional compound which can react with the carboxyl group, for example, a water-soluble glycidyl ether com-pound, a haloepoxy compound, or a dialdehyde compound, and th,e reslllting mixture is subjected to reaction after which the reaction product is slightly crosslinked.
Method 3 An aqueous solution of acrylic acid and alkali acrylate is suspended in a mixed solvent of an alicyclic or aliphatic hydrocarbon and an aliphatic alcohol con-taining a surface active agent and then polymerized in the presence of a water-soluble radical polymerization catalyst.
;:~
3q~13 1 Method 4 An aqueous solution of partially neutralized acrylic acid having a neutralization degree of 50 to 90%
is suspended in an aliphatic ketone, and then poly-merized in the presence of a water-soluble radical poly-merization catalyst and a water soluble high molecular weight dispersing agent.
Method 5 In a petroleum-based aliphatic hydrocarbon solvent is dispersed a more than 40% by weight aqueous alkali metal acrylate solution containing a water-soluble radical polymerization initiator in the presence of a sorbitan fatty acid ester having an HLB of 3 to 6 and ~he resulting suspension is subjected to polymeriza-tion in the absence of a crosslinking agent.Method 6 An aqueous sodium acrylate polymer solution is mixed with a crosslinking agent which can react with the carboxylate, and ~he resulting mixture is heated and dried at 30C or more to form a water absorbent sodium acrylate polymerq Method 7 Starch and acrylic acid are subjected to solu-tion polymerization in the presence of ammonium ceric nitrate solution, after which aqueou~ sodium hydroxide and a crosslinking agent are added ~hereto. The resulting translucent solution is heated and dried to ~3~3~
1 form a water-absorbent resin.
Method 8 Vinyl acetate and methyl ~crylate are subjected to emulsion polymeriæation, and the copolymer thus 5 obtained i5 saponified with sodium hydroxide in a methanol~water mixed solvent, after which the saponifi~
cation product is removed by filtration and dried.
O~her methods than those mentioned above may be used for producing the water-absorbent resin~ to be 10 used as the starting material in the process of this invention .
However, none of the resins produced by the above-mentioned methods exhibit sufficiently satisfac-tory water-dispersibility and water~absorption rate.
In this invention, in order to improve the : performance of the above~mentioned conventional water-absorbent resins, a speci~ic amoun~ o~ water is allowed to be present in the watex-absorbent resins.
: The effect of water/ in this case, is greatly varied depending upon the amount used. Accordingly,~in this invention, water must be used in a pr~portion of 0.01 to lo 3 parts by weight per part of the water -absorbent resin. If the amount of water i9 less than 0.01 part by wei~ht, the resin becomes in the substantially non-swollen state and hence the reaction thereof with thecrosslinkin~ age~t i~ difficult to carry out and require~
a long period of time. ~herefore, said amount is disad~-'i`l""''`-`.
~ .3 ~3~
1 vantageous in industryl On the other hand, if -the amount of water used is more than 1.3 parts by weight, the resin becomes too much swollen, and hence, the subsequent crosslinking reaction proceeds to the S interior of the resin particles, whereby the cross-linking density in the surface layer of the polymer particle becomes low, resulting in no improvement in wa~er~dispersibility and wa~er-absorption rate~ When it is intended ~o enhance the water-dispersibility and water-absorption rate in this case, more crosslinking agent becomes required, which rather reduces extremely the water-absorbency of the resin. Therefore, the use of more than 1.3 parts by weight of water is not desirable.
In view of the above fact, a particularly pre-ferable result is obtained when water is used in a pro-portion of 0.05 to 1.0 part by weight per part by weight of the water-absorbent resin.
The inert ~olvent used in this invention is a solvent which does not affect the water-absorbent resin at all, and includes, for example, lower al~ohols, poly-; hydric alcohols, ketones, ethers, aliphatic hydrocar-bons, aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons and the likè. As the lower alcohol, preferred are alcohols having 1 to 8 carbon atoms, such as methyl alcohols ethyl alcohol, normal propyl alcohol, isopropyl alcohol, normal butyl alcohol, ~ 8 --" . . --J3~
1 isobu~yl alcohol, tertiary butyl alcohol, amyl alcohol~
octyl alcohol and the like. As the polyhydric alcohol, preferred are ethylene glycol, propylene glycol, gly-cerine, diethylene glycol and the like, and as ~he ether, there may be used diethyl ether, dibutyl ether, dioxane, tetrahydrofuran and the likeO
As the aliphatic hydrocarbon, there may be used n-pentane, n-hexane, n~heptane, ligroin and the like; as the aromatic hydrocarbon, there may he u~ed benzene, toluene, xylene, chlorobenzene and the like, and as the alicyc].ic hydrocarbon, there may be used cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and the like. Further, the haloge-nated hydrocarbon include~ carbon tetrachloride, methy-lene chloride, chloroform, ethylene dichloride, trich-loroethylene and the like~
The above-mentioned inert solvents may be used alone or in admixture of two or more. However, in industry, the use of methyl alcohol, n-hexane, n-heptane or cyclohexane alone is prefexred.
The proportion of the inert solvent to the water-absorbent resin is preferably Ool to 50 parts by weight, more pref~rably 0.2 to ~0 parts by weight, per part by weight of the water-absorbent resin, though it 2S may be varied depending upon the kind o water-absorbent resin and the kind of the inert solvent. ~he smaller the amount o~ the inert solYent, the higher the volume ~_ g _ ~3 ~3~3~
1 efficiency. However, the dispersion of the water-absorbent resin becomes bad and the uniform crosslinking becomes difficult. On the contrary, when ~he amount of the inert solvent is larger, the water-ab~orbent resin tends to be dispersed and the crosslinking tends to take place uniformly. However, the volume efficiency becomes bad and the resin becomes difficult to handle. There-fore, the process of this invention must be carried out using water in an amoun~ within the above-mentioned lQ range.
As the crosslinking agent used in this inven-tion, there may be used any crosslinking agent having at least two functional groups which can react with ~he carboxylate, or groups present in the polymer such as hydroxyl group, sulfone group, amino group and the like, including diglycidyl ether compounds, haloepoxy com~
pounds, aldehyde compounds, isocyanate compounds and the like. among them, diglycidyl ether compounds are par-ticularly preferred. Specific examples of the diglyci-dyl ether compounds are (poly)ethyleneglycol diglydicylether, (poly~propyleneglycol diglycidyl ether, (poly)glycerine diglycidyl ether and the like, among which ethylene glycol diglycidyl ether is most preW
ferable. Examples of the haloepoxy compounds are epich-lorohydrint epibromohydrin, ~-methylepichlorohydrin and the like, and examples of the aldehyde compounds are glutaraldehyde, glyoxal and the like, and examples of a3e~3~ -~
1 the isocyanate compounds are 2,4-tolylene diisocyanate, hexamethylene diisocyanate and the like. All of them may be used effectively in this invention. Such crosslinking agents are selected depending upon the kind of the water-absorbent resin, and the purpose of use thereof lies in imparting a crosslinked structure again to the resin having water-absorbency. Therefore, the amount of the crosslinking agent used is generally very slight, and may be varied depending upon the kind of crosslinking agent/- the kind of inert solvent, the amount of water present, and the purpose of use of water-absorbent resin, though usually appropriate is the amount of 0,005 to 5.0% by weight based on the weight of the water~absorbent resinD In general, if the amount of the crosslinking agent used is less than n~ 005~ by weight, the effect of addition does not appear, and lf the amount is more than 5~0~ by weight, there is obtained a resin having an extremely high degree of crosslinking which reduces remarkably the water-~0 absorbency. Therefore, such amounts are not desirable.
There may be used many methods forcrosslinking the resin with a cro~slinking ag2nt in this invention. That is to say, the water absorbent resin may be dispersed in an inert solvent, followeed by adding water and then the crosslinking agent to the resulting dispersion, and thereafter heat-treating the resulting slurry, preferably under reflux, or alternatively, the ~ e ~
,; J
~2~ 3~
1 slurry after the addition o~ the crosslinking agent may be heated and evaporated, to effect the crosslinking.
As other methods, the reaction mixture obtained by the reaction ~n the presence of an inert solvent mentioned above may be subjected to adju5tm~nt of the ratio bet-ween the water-absorbent resin and the water, followed by adding a crosslinking agent and thereafter, heat-treating the resulting mixture, preferabl~ under reflux t or alternatively, the slurry after the addition of the crosslinking agent may be heated and evaporated, to effect the crosslinking. The heat treated product may be, of course, subjected to filtration and drying to obtain a commercial product9 In order to conduct the above-mentioned crosslinking reaction smoothly, the temperature for the heat-treatment of the slurry may preferably be usually ~ithin the range of from 40 to 150C though the tem-perature may be varied depending upon the kind of the crosslnking agen~ used, the kind of the inert ~olvent used, the amount of water present and the purpose of use of the water-absorbent resin and hence cannot be uni quely determined.
This invention is characterized in that ~he treatment method is simplel the formation of unswollen powder lump~at the initial ~tage of water absorption can be prevented, the dispersibility in water can greatly be improved and simultaneously the water-absorption rate is 'A
~Z~3~3~
1 much enhanced as well as the workability in actual use in various ~ields can be improved.
This invention is further explained below in more detail referring to Zxamples and Comparative Examples. However, these Examples are merely by way of illustration and not by way of limitation.
The term "absorbency" used herein means a value determined according to the following procedure:
In the case of deionized water-absorbency, 2 liters of deionized water and 1 g of the dried polymer were placed in a 3-liter beaker, and water was absorbed by the polymer for a predetermined period of time while the mixture was allowed to stand, after which the polymer was collected by filtration with a lO0-mesh metallic wire gauze and the volume of the swollen polymer obtained as a filtered cake was measured by means of a messcylinder~ The value was taken as the deionized water-absorbency~
In the case of saline solution-absorbency, 200 ml of saline solution (0.9% by weight aqueous sodium chloride solution) and l g of dried polymer were placed in a 300-~ml beaker and the solution was absorbed by the polymer for the predetermined period of time while the mixture was allowed to stand, after which it was filtered with a 200-mesh me-tallic wire gauze, and the volume of the swollen polymer obtained as a filtered cake was measured by means of a messcylinder3 The value 1 was taken as the saline solution-absorbency.
Comparative Example 1 In a 200-ml flask was placed 39.1 g o acrylic acid having a purity of 99.8~ by weight, and 76.5 g of a 22.6% by weight aqueous sodi.um hydroxide solution was dropped thereinto with cooling and stirring to neutra-lize 80 mole% of the acrylic acid, after which 0.13 g of potassium persulfate was added thereto. The resulting mixture was stirred at room temperature to form a solution.
Into a 500-ml flask provided with a reflux condenser purged with nitrogen were charged 213 g of cyclohexane and 1.9 g of sorbitan monolaurate having an HLB of 8.6, after which a surfactant was dissolved at room temperature with stirring. To the resulting solu-tion was added dropwise the above-mentioned aqueous par-tially neutralized acrylic acid solution to form a suspension. The flask was again sufficiently purged with nitrogen, the temperature of the suspension was elevated and polymerization was conducted for 3 hours while keeping the bath temperature at 55-60C~
The resul~ing polymerization mixture was vaporized to dryness under reduced pressure, to obtain 48.0 g of fine, granular, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~2~3~3~
1 Comparative Example 2 In a 100-ml flask was placed 39.1 g of acrylic acid having a p~rity of 99.8% by weight, and 54.2 g of a 28% by weight aqueous sodium hydroxide solution was dropped thereinto with cooling and stirring to neutra-lize 70 mole~ of the acryllc acid, after which 0.13 g of potassium persulfate was added thereto. The resulting mixture was stirred to form a solution at room tem-perature.
In a 500-ml flask provided with a stirrer purged with nitrogen were placed 213.6 g of cyclohexane and 1.1 g o~ sorbitan monostearate, and the surfactant was dissolved at 50-55C with stirring The resulting solution was cooled to room temperature, and the above~
mentioned partially neutralized acrylic acid solution was dropped ~hereinto to form a suspension. The tem-perature of the suspension was elevated with stirring while keeping the system at a reduced pressure of 300 Torr, and the suspension was kept at 50C to conduct the polymerization for 6 hours, after which the refluxing was stopped and the reaction mixture was evaporated to dryness under reduced pressure, thereby obtaining 48.8 g of a fine powder of white dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~3~39 1 Comparati~e Example 3 Into a reactor provided with a stlrrer, a nitrogen-blowing tube and a thermomeker were charged 20 g of corn starch and 400 g of water, and the resluting mixture was stirred at 80~C for one hour under a nitro-gen atmosphere. The resulting aqueous solution was cooled to 30C, and hO g of acrylic acid and 30 g of ammonium ceric nitrate solution (0.1 mole of cerium ion in 1 N nitric acid) were added thereto, after which the resulting mixture was subjected to polymerization at 30-40C for 3 hours.
To the polymerization mixture was added 50 g of a 30~ by weight aqueous sodium hydroxide solution with stirring~ and subsequently, 0.5 g of ethylene gly-lS col diglycidyl ether was added thereto, after which theresulting mixture was poured in~o a tray, and dried at 100C for 3 hours and then at 60C for 2 hours under reduced pressure. The resulting sheet-shaped material was pulverized to obtain 9S g of white powder. The water-absorbency and saline solution-absorbency were as shown in Table 3.
Comparative Example 4 In 300 ml of water containing 3 g of polyvinyl alcohol and 10 g of sodium chloride were dispersed 60 g of vinyl acetate and 40 g of methyl acrylate, and 0.5 g of benzoyl peroxide was added thereto, after which the `.!
~2~
1 resulting mixture was subjected to suspension polymeri za~ion at 6SC ~or 6 hours. The resulting copolymer was separated by filtra~ion and dried~
Subseqllen~1y, 34.4 g of the copolymer thus obtained was suspended in a saponifying solution con-sisting of 800 ~ of methanol, ~0 g of water and 160 ml of 5 N aqueous sodium hydroxide solution, and the resulting suspension was subjec~ed to saponification at 25C for one hour, after which the temperature of the saponification product was elevated to continue the saponification or 5 hoursO After the completion of the saponification, the saponification product was washed well with methanol, and thereafter dried to obtain 26 g of a water-absorbent copolymerO The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Comparative Example 5 The same procedure as in comparative Example 1 was repeated, except that the 39.1 g of acrylic acid having a purity of 99O8% by weight was replaced by 35.2 g of acrylic acid having a purity o~ 99.8% by weight and 4.7 g of methacrylic acid having a purity of 99% by weight, to obtain 49.3 g of finely granular~ dried polymer~ The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
. - 17 -~3~3~
1 Example 1 In a 500~ml ~lask provlded with a stirrer, an oil bath and a cooler was placed 41 g of the water-absorbent resin having a water content of 2 5% obtained in the same manner as in Comparative Example 1, and 50 g of methanol was then added thereto, after which a solu-tion of 32 mg of ethylene glycol diglycidyl ether in 9 g of water (total amount of water: 10 g) was added thereto with stirring. The resulting mixture was well stirred and then evaporated to dryness by keeping the oil bath at 110C, to obtain 41.5 g of finely granular/ dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Examples 2~6 The same procedure as in Example 1 wa~
repeated~ except that the amounts of methanol and water were varied as shown in Table 1, to obtain finely granu-lar, dried polymers. The water-absorbency and saline ~olution-absorbency of the polymers were as shown in Table 3.
~2C~3~3~
Table 1 Example No. Methanol (g) Water (g) Total water (g~
1 This invention relate~ to a water absorbent resin having an improved dispersibility in water and an improved water absorbency, and a process.for producing the water absorbent resin~ More particularly, it rela-tes to a process for producing a water-absorbent resin having an improved water-absorbency and an improved water-dispersibility which compri~e~ crosslinking a water-absorben~ resin comprising a carboxylate as a constituent of the resin with a crossLinking agent having at least two functional groups in the presence of water in an inert solventO
Water absorbent resins are used in the field of sanitation as menstrual articies, diapers~ disposable house-clo~hs and the like and in the field of agriculture 15 and horticulture as water retentive materials. Further, they are useful in other various fields such as coagula-tion of sludges, prevention of dew condensation on construction materials, dehydration of oils and so on.
As this type of water a~sorbent resin, there are known 20 crosslinked carboxymethyl cellulose, partially cross-linked polyethylene oxide9 crosslinked hydrolyzates of starch-acrylonitrile graft copolymer, partially cross~
linked polyacrylic acid salts: and the like However, all of them have disadvantages that they have low water-~)3~
1 absorbency, and even if ~he water-absorbency is satis-factory, the water-dispersibility is inferior or the water-absorbing rate is low.
If these disadvantages are overcome, it is clear that the water absorbent resins will be more broadly used in various fields including sanitary articles ~uch as sanitary napkins9 paper diapers, under-pads, and the like, and it has been desired that improved articles come into the market.
As the water-absorbent resin, there are known various synthetic resins as mentioned above.
Particularly, Japanese Patent Application Kokai (Laid-Open) Nos; 93,716/81; 131,608/81 and 147,806/81 disclo5e methods for producing water-absorbent resins using as lS the starting material acrylic acid, which are commer cially easily available and ar~ uniform in quality.
These water-absorbent resins have an improved water-absorbency even in an aqueous electrolyte solution and an improved stabili~y in the wa~er-ab~orbed state~
However, th~se water~absorbent resins are still unsatis-factory in dispersibility in water and water-absorbing rate. Moreover, European Patent Application No.
80304099.7 (Publication No~ 0036463) and U.S. Patent No, 4,340,706 disclose that a water-absorbent resin suitable for usages requiring a stability in the fluid absorbed state for a long period of time or a high water-absorbing rate can be obtained by crosslinking an ~1 3~
1 acrylic acid salt polymer with a crosslink.ing agent.
However, even the resin obtained by said method i5 still not sufficient in water-dispersibility and water absorption rate.
The present inventors have further made research on the conditions ~or crosslinking water-absorbent resins with a crosslinking agent. As a result, it has surprisingly and unexpectedly been found that when a water-absorbent resin comprising a car-boxylate as its constituent is cros~linked with a crosslinking agent having at least two functional groups in the presence o~ a specific amount of water in an inert solvent, the water-dispersibility and the water-absorption rate can bo~h be greatly improved while retaining its water-absorbency as i~ is.
According to thi~ invention, there is provided a process for producing a water-absorbent resin having an improved water-absorbing rate and water-dispersibility, characterized by crosslinking a water-absorbent resin comprising a carboxylate as a consti-tuent of the resin with a crosslinking agent having at least two functional groups in the pre~ence of water ln a proportion of 0.01 to 1.3 parts by weight per part by weight of the resin in an inert solvent, The water-absorhent resins used in this inven-tion may be a~y polymer or copolymer comprising a car-boxylate as its con~ti~uentO Among the polymers or 3~
copol~Mers, there may preferably be used those co~pr sing an alkali metal acrylate or an alkali metal methacrylate as their constituent and those comprising a carboxyla~e and a hydroxyl group as their constituents~
As said water-absorbent resin, there may be used crosslinked polyacrylic acid salts, crosslin]ced copolymers of acrylic acid salts and methacrylic acid salts, crosslinked saponification products of methyl acrylate-vinyl acetate copolymer, crosslinked saponification products of starch~ethyl acryla~e graft - copolymer, crosslinked starch-acrylic acid salt graft copolymer, crosslinked saponification products of starch-methyl methacrylate graft copolymer, crosslinked saponification products of starch-acrylamide graf~ copolymer, crosslinked saponification products of starch-acrylonitrile-2-acrylamide-2-methylpropane sulfonic acid graft copolymer, crosslinked saponification products of starch-acrylonitrile graft copolymer, crosslinked sa~onification products of starch-acrylonitrile-vinylsulfonic acid graft copolymer, polyethylene oxide crosslinked with acrylic acid, crosslinked sodium carboxymethyl cellulose, and the like.
The water-absorbent resins comprising a carboxylate as its constituent can be produced by the methods disclosed in Japanese Patent Application Kokai (Laid-Open) Nos. 93,716/81; 131,608/81; and 147,806/81 as referred to above as well as the methods disclosed in 1~
~ 4 -~2~
1 Japanese Patent Publication Nos. 30,710/79; 37,994/79;
and 46,200/78 and U.S.P. 4,041,22~. Representative methods for producing the ~ater-absorbent resins which may be used as the startlng materials are as follows:
Method 1 An aqueous solution of acrylic acid and alkali acrylate is suspended in an alicyclic or aliphatic hydrocarbon solvent containing a surfactant having an HLB of 8 to 12 and polymerized in the presence of a water~soluble radical polymerization initiator.
Method 2 To the polymeri~ation reaction product obtained by the same way as in Method 1 is added a poly-functional compound which can react with the carboxyl group, for example, a water-soluble glycidyl ether com-pound, a haloepoxy compound, or a dialdehyde compound, and th,e reslllting mixture is subjected to reaction after which the reaction product is slightly crosslinked.
Method 3 An aqueous solution of acrylic acid and alkali acrylate is suspended in a mixed solvent of an alicyclic or aliphatic hydrocarbon and an aliphatic alcohol con-taining a surface active agent and then polymerized in the presence of a water-soluble radical polymerization catalyst.
;:~
3q~13 1 Method 4 An aqueous solution of partially neutralized acrylic acid having a neutralization degree of 50 to 90%
is suspended in an aliphatic ketone, and then poly-merized in the presence of a water-soluble radical poly-merization catalyst and a water soluble high molecular weight dispersing agent.
Method 5 In a petroleum-based aliphatic hydrocarbon solvent is dispersed a more than 40% by weight aqueous alkali metal acrylate solution containing a water-soluble radical polymerization initiator in the presence of a sorbitan fatty acid ester having an HLB of 3 to 6 and ~he resulting suspension is subjected to polymeriza-tion in the absence of a crosslinking agent.Method 6 An aqueous sodium acrylate polymer solution is mixed with a crosslinking agent which can react with the carboxylate, and ~he resulting mixture is heated and dried at 30C or more to form a water absorbent sodium acrylate polymerq Method 7 Starch and acrylic acid are subjected to solu-tion polymerization in the presence of ammonium ceric nitrate solution, after which aqueou~ sodium hydroxide and a crosslinking agent are added ~hereto. The resulting translucent solution is heated and dried to ~3~3~
1 form a water-absorbent resin.
Method 8 Vinyl acetate and methyl ~crylate are subjected to emulsion polymeriæation, and the copolymer thus 5 obtained i5 saponified with sodium hydroxide in a methanol~water mixed solvent, after which the saponifi~
cation product is removed by filtration and dried.
O~her methods than those mentioned above may be used for producing the water-absorbent resin~ to be 10 used as the starting material in the process of this invention .
However, none of the resins produced by the above-mentioned methods exhibit sufficiently satisfac-tory water-dispersibility and water~absorption rate.
In this invention, in order to improve the : performance of the above~mentioned conventional water-absorbent resins, a speci~ic amoun~ o~ water is allowed to be present in the watex-absorbent resins.
: The effect of water/ in this case, is greatly varied depending upon the amount used. Accordingly,~in this invention, water must be used in a pr~portion of 0.01 to lo 3 parts by weight per part of the water -absorbent resin. If the amount of water i9 less than 0.01 part by wei~ht, the resin becomes in the substantially non-swollen state and hence the reaction thereof with thecrosslinkin~ age~t i~ difficult to carry out and require~
a long period of time. ~herefore, said amount is disad~-'i`l""''`-`.
~ .3 ~3~
1 vantageous in industryl On the other hand, if -the amount of water used is more than 1.3 parts by weight, the resin becomes too much swollen, and hence, the subsequent crosslinking reaction proceeds to the S interior of the resin particles, whereby the cross-linking density in the surface layer of the polymer particle becomes low, resulting in no improvement in wa~er~dispersibility and wa~er-absorption rate~ When it is intended ~o enhance the water-dispersibility and water-absorption rate in this case, more crosslinking agent becomes required, which rather reduces extremely the water-absorbency of the resin. Therefore, the use of more than 1.3 parts by weight of water is not desirable.
In view of the above fact, a particularly pre-ferable result is obtained when water is used in a pro-portion of 0.05 to 1.0 part by weight per part by weight of the water-absorbent resin.
The inert ~olvent used in this invention is a solvent which does not affect the water-absorbent resin at all, and includes, for example, lower al~ohols, poly-; hydric alcohols, ketones, ethers, aliphatic hydrocar-bons, aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons and the likè. As the lower alcohol, preferred are alcohols having 1 to 8 carbon atoms, such as methyl alcohols ethyl alcohol, normal propyl alcohol, isopropyl alcohol, normal butyl alcohol, ~ 8 --" . . --J3~
1 isobu~yl alcohol, tertiary butyl alcohol, amyl alcohol~
octyl alcohol and the like. As the polyhydric alcohol, preferred are ethylene glycol, propylene glycol, gly-cerine, diethylene glycol and the like, and as ~he ether, there may be used diethyl ether, dibutyl ether, dioxane, tetrahydrofuran and the likeO
As the aliphatic hydrocarbon, there may be used n-pentane, n-hexane, n~heptane, ligroin and the like; as the aromatic hydrocarbon, there may he u~ed benzene, toluene, xylene, chlorobenzene and the like, and as the alicyc].ic hydrocarbon, there may be used cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and the like. Further, the haloge-nated hydrocarbon include~ carbon tetrachloride, methy-lene chloride, chloroform, ethylene dichloride, trich-loroethylene and the like~
The above-mentioned inert solvents may be used alone or in admixture of two or more. However, in industry, the use of methyl alcohol, n-hexane, n-heptane or cyclohexane alone is prefexred.
The proportion of the inert solvent to the water-absorbent resin is preferably Ool to 50 parts by weight, more pref~rably 0.2 to ~0 parts by weight, per part by weight of the water-absorbent resin, though it 2S may be varied depending upon the kind o water-absorbent resin and the kind of the inert solvent. ~he smaller the amount o~ the inert solYent, the higher the volume ~_ g _ ~3 ~3~3~
1 efficiency. However, the dispersion of the water-absorbent resin becomes bad and the uniform crosslinking becomes difficult. On the contrary, when ~he amount of the inert solvent is larger, the water-ab~orbent resin tends to be dispersed and the crosslinking tends to take place uniformly. However, the volume efficiency becomes bad and the resin becomes difficult to handle. There-fore, the process of this invention must be carried out using water in an amoun~ within the above-mentioned lQ range.
As the crosslinking agent used in this inven-tion, there may be used any crosslinking agent having at least two functional groups which can react with ~he carboxylate, or groups present in the polymer such as hydroxyl group, sulfone group, amino group and the like, including diglycidyl ether compounds, haloepoxy com~
pounds, aldehyde compounds, isocyanate compounds and the like. among them, diglycidyl ether compounds are par-ticularly preferred. Specific examples of the diglyci-dyl ether compounds are (poly)ethyleneglycol diglydicylether, (poly~propyleneglycol diglycidyl ether, (poly)glycerine diglycidyl ether and the like, among which ethylene glycol diglycidyl ether is most preW
ferable. Examples of the haloepoxy compounds are epich-lorohydrint epibromohydrin, ~-methylepichlorohydrin and the like, and examples of the aldehyde compounds are glutaraldehyde, glyoxal and the like, and examples of a3e~3~ -~
1 the isocyanate compounds are 2,4-tolylene diisocyanate, hexamethylene diisocyanate and the like. All of them may be used effectively in this invention. Such crosslinking agents are selected depending upon the kind of the water-absorbent resin, and the purpose of use thereof lies in imparting a crosslinked structure again to the resin having water-absorbency. Therefore, the amount of the crosslinking agent used is generally very slight, and may be varied depending upon the kind of crosslinking agent/- the kind of inert solvent, the amount of water present, and the purpose of use of water-absorbent resin, though usually appropriate is the amount of 0,005 to 5.0% by weight based on the weight of the water~absorbent resinD In general, if the amount of the crosslinking agent used is less than n~ 005~ by weight, the effect of addition does not appear, and lf the amount is more than 5~0~ by weight, there is obtained a resin having an extremely high degree of crosslinking which reduces remarkably the water-~0 absorbency. Therefore, such amounts are not desirable.
There may be used many methods forcrosslinking the resin with a cro~slinking ag2nt in this invention. That is to say, the water absorbent resin may be dispersed in an inert solvent, followeed by adding water and then the crosslinking agent to the resulting dispersion, and thereafter heat-treating the resulting slurry, preferably under reflux, or alternatively, the ~ e ~
,; J
~2~ 3~
1 slurry after the addition o~ the crosslinking agent may be heated and evaporated, to effect the crosslinking.
As other methods, the reaction mixture obtained by the reaction ~n the presence of an inert solvent mentioned above may be subjected to adju5tm~nt of the ratio bet-ween the water-absorbent resin and the water, followed by adding a crosslinking agent and thereafter, heat-treating the resulting mixture, preferabl~ under reflux t or alternatively, the slurry after the addition of the crosslinking agent may be heated and evaporated, to effect the crosslinking. The heat treated product may be, of course, subjected to filtration and drying to obtain a commercial product9 In order to conduct the above-mentioned crosslinking reaction smoothly, the temperature for the heat-treatment of the slurry may preferably be usually ~ithin the range of from 40 to 150C though the tem-perature may be varied depending upon the kind of the crosslnking agen~ used, the kind of the inert ~olvent used, the amount of water present and the purpose of use of the water-absorbent resin and hence cannot be uni quely determined.
This invention is characterized in that ~he treatment method is simplel the formation of unswollen powder lump~at the initial ~tage of water absorption can be prevented, the dispersibility in water can greatly be improved and simultaneously the water-absorption rate is 'A
~Z~3~3~
1 much enhanced as well as the workability in actual use in various ~ields can be improved.
This invention is further explained below in more detail referring to Zxamples and Comparative Examples. However, these Examples are merely by way of illustration and not by way of limitation.
The term "absorbency" used herein means a value determined according to the following procedure:
In the case of deionized water-absorbency, 2 liters of deionized water and 1 g of the dried polymer were placed in a 3-liter beaker, and water was absorbed by the polymer for a predetermined period of time while the mixture was allowed to stand, after which the polymer was collected by filtration with a lO0-mesh metallic wire gauze and the volume of the swollen polymer obtained as a filtered cake was measured by means of a messcylinder~ The value was taken as the deionized water-absorbency~
In the case of saline solution-absorbency, 200 ml of saline solution (0.9% by weight aqueous sodium chloride solution) and l g of dried polymer were placed in a 300-~ml beaker and the solution was absorbed by the polymer for the predetermined period of time while the mixture was allowed to stand, after which it was filtered with a 200-mesh me-tallic wire gauze, and the volume of the swollen polymer obtained as a filtered cake was measured by means of a messcylinder3 The value 1 was taken as the saline solution-absorbency.
Comparative Example 1 In a 200-ml flask was placed 39.1 g o acrylic acid having a purity of 99.8~ by weight, and 76.5 g of a 22.6% by weight aqueous sodi.um hydroxide solution was dropped thereinto with cooling and stirring to neutra-lize 80 mole% of the acrylic acid, after which 0.13 g of potassium persulfate was added thereto. The resulting mixture was stirred at room temperature to form a solution.
Into a 500-ml flask provided with a reflux condenser purged with nitrogen were charged 213 g of cyclohexane and 1.9 g of sorbitan monolaurate having an HLB of 8.6, after which a surfactant was dissolved at room temperature with stirring. To the resulting solu-tion was added dropwise the above-mentioned aqueous par-tially neutralized acrylic acid solution to form a suspension. The flask was again sufficiently purged with nitrogen, the temperature of the suspension was elevated and polymerization was conducted for 3 hours while keeping the bath temperature at 55-60C~
The resul~ing polymerization mixture was vaporized to dryness under reduced pressure, to obtain 48.0 g of fine, granular, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~2~3~3~
1 Comparative Example 2 In a 100-ml flask was placed 39.1 g of acrylic acid having a p~rity of 99.8% by weight, and 54.2 g of a 28% by weight aqueous sodium hydroxide solution was dropped thereinto with cooling and stirring to neutra-lize 70 mole~ of the acryllc acid, after which 0.13 g of potassium persulfate was added thereto. The resulting mixture was stirred to form a solution at room tem-perature.
In a 500-ml flask provided with a stirrer purged with nitrogen were placed 213.6 g of cyclohexane and 1.1 g o~ sorbitan monostearate, and the surfactant was dissolved at 50-55C with stirring The resulting solution was cooled to room temperature, and the above~
mentioned partially neutralized acrylic acid solution was dropped ~hereinto to form a suspension. The tem-perature of the suspension was elevated with stirring while keeping the system at a reduced pressure of 300 Torr, and the suspension was kept at 50C to conduct the polymerization for 6 hours, after which the refluxing was stopped and the reaction mixture was evaporated to dryness under reduced pressure, thereby obtaining 48.8 g of a fine powder of white dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~3~39 1 Comparati~e Example 3 Into a reactor provided with a stlrrer, a nitrogen-blowing tube and a thermomeker were charged 20 g of corn starch and 400 g of water, and the resluting mixture was stirred at 80~C for one hour under a nitro-gen atmosphere. The resulting aqueous solution was cooled to 30C, and hO g of acrylic acid and 30 g of ammonium ceric nitrate solution (0.1 mole of cerium ion in 1 N nitric acid) were added thereto, after which the resulting mixture was subjected to polymerization at 30-40C for 3 hours.
To the polymerization mixture was added 50 g of a 30~ by weight aqueous sodium hydroxide solution with stirring~ and subsequently, 0.5 g of ethylene gly-lS col diglycidyl ether was added thereto, after which theresulting mixture was poured in~o a tray, and dried at 100C for 3 hours and then at 60C for 2 hours under reduced pressure. The resulting sheet-shaped material was pulverized to obtain 9S g of white powder. The water-absorbency and saline solution-absorbency were as shown in Table 3.
Comparative Example 4 In 300 ml of water containing 3 g of polyvinyl alcohol and 10 g of sodium chloride were dispersed 60 g of vinyl acetate and 40 g of methyl acrylate, and 0.5 g of benzoyl peroxide was added thereto, after which the `.!
~2~
1 resulting mixture was subjected to suspension polymeri za~ion at 6SC ~or 6 hours. The resulting copolymer was separated by filtra~ion and dried~
Subseqllen~1y, 34.4 g of the copolymer thus obtained was suspended in a saponifying solution con-sisting of 800 ~ of methanol, ~0 g of water and 160 ml of 5 N aqueous sodium hydroxide solution, and the resulting suspension was subjec~ed to saponification at 25C for one hour, after which the temperature of the saponification product was elevated to continue the saponification or 5 hoursO After the completion of the saponification, the saponification product was washed well with methanol, and thereafter dried to obtain 26 g of a water-absorbent copolymerO The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Comparative Example 5 The same procedure as in comparative Example 1 was repeated, except that the 39.1 g of acrylic acid having a purity of 99O8% by weight was replaced by 35.2 g of acrylic acid having a purity o~ 99.8% by weight and 4.7 g of methacrylic acid having a purity of 99% by weight, to obtain 49.3 g of finely granular~ dried polymer~ The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
. - 17 -~3~3~
1 Example 1 In a 500~ml ~lask provlded with a stirrer, an oil bath and a cooler was placed 41 g of the water-absorbent resin having a water content of 2 5% obtained in the same manner as in Comparative Example 1, and 50 g of methanol was then added thereto, after which a solu-tion of 32 mg of ethylene glycol diglycidyl ether in 9 g of water (total amount of water: 10 g) was added thereto with stirring. The resulting mixture was well stirred and then evaporated to dryness by keeping the oil bath at 110C, to obtain 41.5 g of finely granular/ dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Examples 2~6 The same procedure as in Example 1 wa~
repeated~ except that the amounts of methanol and water were varied as shown in Table 1, to obtain finely granu-lar, dried polymers. The water-absorbency and saline ~olution-absorbency of the polymers were as shown in Table 3.
~2C~3~3~
Table 1 Example No. Methanol (g) Water (g) Total water (g~
2 90 2.3 3.3
3 148 11.0 12.0
4 10.3 5.9 6.9 32 7~ 8.0 6 ~8 31.0 32.0 Example 7 The same procedure as in Example 1 was repeated, except that the methanol was repla~ed by n-heptane, to obtain finely granular, dried polymer.
The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Examples 8-10 ~he same procedure as in Example 7 was repeated, except that the amount o ethylen~ glycol diglycidyl ether was varied as shown in Table 2~ to obtain finely granular ~ dried polymerD The water-absorbency and saline solution~ahsorbency of the polymer were as shown in Table 3.
3~3~
Table 2 Example No. Ethyleneglycol dlglycidyl ether (mg) 1 Example 11 The same procedure as in Example 1 was repeated, except that epichlorohydrin was substituted for the ethylene glycol diglycidyl ether, to obtain finely granular, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 12 10From the polymerization mixture obtained in Comparative Example 2 was removed 22.2 g of the water and subsequently, 47.4 mg of ethylene glycol diglycidyl ether was added thereto, after which the resulting mix-ture was well stirred. The oil bath was thereafter kept at 110C ~o evaporate the mixture to dryness, thereby obtaining finely divided, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~.~03~3~
1 Example 13 The same procesure as in Example 1 was repeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 3 was substituted for the water-absorbent resin and polyethy-lene glycol diglycidyl ether was substituted for the ethylene glycol diglycidyl ether, to obtain powdery, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 14 The same procedure as in Example 1 was repeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 4 was substituted for the water-absorbent resin, and glycerine diglycidyl ether was substituted for the ethylene glycol diglycidyl ether, to obtain finely granular~ dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 15 The same procesure as in Example 1 wasrepeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 5 was substituted for the water-absorbent resin, to obtain finely granular, dried polymer. The water-absorbency ~2~3~3~
1 and saline solution-absorbency of the polymer were as shown in Table 3.
Comparative Example 6 The same procedure as in Example 1 was repeated, except that 100 g of n-heptane and 59 g of water were substituted for the methanol, to obtain a lump-like, dried polymer, which was then pulverized and used to measure the water-absorbency and saline solution-absorbency. The results obtained were as shown in Table 3.
3~
Table 3 Amount of Solvent water present Amo~lnt (% by weight) Kind (% by wt.) Comp, Ex. 1 " 3 " 4 Example 1 10 Methanol. 50 2 2.5 " 67.5 " 3 6.0 " 74 " 4 12 " 18 " 5 10 I~ 40 " 6 20 " 55 " 7 10 n-Heptane 50 " 8 10 " 50 " 9 10 . I~ 50 " 10 10 " 50 11 10 Methanol 50 " 12 8~34Cyclohexane 75.03 " 13 10 Methanol 50 " 14 10 " 50 " 15 10 " 50 Comp. Ex. 6 30 n-Heptane 50 Note. E-100: Ethylene glycol diglycidyl ether E-400: Polyekhylene glycol diglycidyl ether ECH : Epichlorohydrin G-100: Glycerine diglycidyl ether ~2~33~3~
Table 3 (Cont'd) Crosslinking Water-absorbent Water/resin agent resin weight ratio Kind ~mount (% by wt.) (mg) 0.25 E-100 32 0~083 " "
0.3 I~ ~
0.17 " "
0.2 " "
0.8 " "
0.25 " "
0.25 " 10 0.25 " 100 0.~5 " 500 0.25 ECH 32 16.63 0.50 Æ-100 47.4 0.25 E-100 32 0.25 E 100 32 1.50 E-100 32 ~3~
Table 3 (Cont'd) Deionized Saline water-absorbency solLltion ~absorbency (ml/g) (ml/y) After Aft:er After After Ater After 1 min 5 min 10 min 1 min 5 min 10 min 60100 200 8 15 ~5 80200 420 8 ~0a~l 330460 1100 31 65. 98 640920 1300 5~ 77116 ~2~3~3~:~
Table 3 (Cont'd) Forrnation of unswollen powder lump Formed A little formed Formed ..
..
ll ..
..
..
..
ll ..
The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Examples 8-10 ~he same procedure as in Example 7 was repeated, except that the amount o ethylen~ glycol diglycidyl ether was varied as shown in Table 2~ to obtain finely granular ~ dried polymerD The water-absorbency and saline solution~ahsorbency of the polymer were as shown in Table 3.
3~3~
Table 2 Example No. Ethyleneglycol dlglycidyl ether (mg) 1 Example 11 The same procedure as in Example 1 was repeated, except that epichlorohydrin was substituted for the ethylene glycol diglycidyl ether, to obtain finely granular, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 12 10From the polymerization mixture obtained in Comparative Example 2 was removed 22.2 g of the water and subsequently, 47.4 mg of ethylene glycol diglycidyl ether was added thereto, after which the resulting mix-ture was well stirred. The oil bath was thereafter kept at 110C ~o evaporate the mixture to dryness, thereby obtaining finely divided, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
~.~03~3~
1 Example 13 The same procesure as in Example 1 was repeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 3 was substituted for the water-absorbent resin and polyethy-lene glycol diglycidyl ether was substituted for the ethylene glycol diglycidyl ether, to obtain powdery, dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 14 The same procedure as in Example 1 was repeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 4 was substituted for the water-absorbent resin, and glycerine diglycidyl ether was substituted for the ethylene glycol diglycidyl ether, to obtain finely granular~ dried polymer. The water-absorbency and saline solution-absorbency of the polymer were as shown in Table 3.
Example 15 The same procesure as in Example 1 wasrepeated, except that the water-absorbent resin obtained in the same manner as in Comparative Example 5 was substituted for the water-absorbent resin, to obtain finely granular, dried polymer. The water-absorbency ~2~3~3~
1 and saline solution-absorbency of the polymer were as shown in Table 3.
Comparative Example 6 The same procedure as in Example 1 was repeated, except that 100 g of n-heptane and 59 g of water were substituted for the methanol, to obtain a lump-like, dried polymer, which was then pulverized and used to measure the water-absorbency and saline solution-absorbency. The results obtained were as shown in Table 3.
3~
Table 3 Amount of Solvent water present Amo~lnt (% by weight) Kind (% by wt.) Comp, Ex. 1 " 3 " 4 Example 1 10 Methanol. 50 2 2.5 " 67.5 " 3 6.0 " 74 " 4 12 " 18 " 5 10 I~ 40 " 6 20 " 55 " 7 10 n-Heptane 50 " 8 10 " 50 " 9 10 . I~ 50 " 10 10 " 50 11 10 Methanol 50 " 12 8~34Cyclohexane 75.03 " 13 10 Methanol 50 " 14 10 " 50 " 15 10 " 50 Comp. Ex. 6 30 n-Heptane 50 Note. E-100: Ethylene glycol diglycidyl ether E-400: Polyekhylene glycol diglycidyl ether ECH : Epichlorohydrin G-100: Glycerine diglycidyl ether ~2~33~3~
Table 3 (Cont'd) Crosslinking Water-absorbent Water/resin agent resin weight ratio Kind ~mount (% by wt.) (mg) 0.25 E-100 32 0~083 " "
0.3 I~ ~
0.17 " "
0.2 " "
0.8 " "
0.25 " "
0.25 " 10 0.25 " 100 0.~5 " 500 0.25 ECH 32 16.63 0.50 Æ-100 47.4 0.25 E-100 32 0.25 E 100 32 1.50 E-100 32 ~3~
Table 3 (Cont'd) Deionized Saline water-absorbency solLltion ~absorbency (ml/g) (ml/y) After Aft:er After After Ater After 1 min 5 min 10 min 1 min 5 min 10 min 60100 200 8 15 ~5 80200 420 8 ~0a~l 330460 1100 31 65. 98 640920 1300 5~ 77116 ~2~3~3~:~
Table 3 (Cont'd) Forrnation of unswollen powder lump Formed A little formed Formed ..
..
ll ..
..
..
..
ll ..
Claims
1. A process for producing a water-absorbent resin having an improved water-absorbency, characterized by crosslinking a water-absorbent resin comprising a carboxylate as a constituent of the resin with a crosslinking agent having at least two functional groups in the presence of water in a proportion of 0.01 to 1.3 parts by weight per part by weight of the resin in an inert solvent.
2. A process according to Claim 1, wherein the water-absorbent resin is a polymer comprising an alkali metal acrylate or methacrylate as a constituent.
3. A process according to Claim 1, wherein the water is present in a proportion of 0.05 to 1.0 parts by weight per part by weight of the water-absorbent resin.
4. A process according to Claim 1, wherein the water absorbent resin comprises a carboxylate and a hydroxyl group as constituents of the resin.
5. A process according to Claim 1, wherein the inert solvent is used in a proportion of 0.2 to 20 parts by weight per part by weight of the water-absorbent resin.
6. A process according to Claim 1, wherein the inert solvent is methanol.
7. A process according to Claim 1, wherein the inert solvent is cyclohexane.
8. A process according to Claim 1, wherein the inert solvent is n-heptane.
9. A process according to Claim 1, wherein the crosslinking agent is a diglycidyl ether compound.
10. A process according to Claim 9, wherein the crosslinking agent is ethylene glycol diglycidyl ether.
11. A water-absorbent resin having an improved water-absorbency obtained by the process according to
Claim 1.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP213885/81 | 1981-12-30 | ||
JP56213885A JPS6018690B2 (en) | 1981-12-30 | 1981-12-30 | Method for improving water absorbency of water absorbent resin |
Publications (1)
Publication Number | Publication Date |
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CA1203039A true CA1203039A (en) | 1986-04-08 |
Family
ID=16646623
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000417618A Expired CA1203039A (en) | 1981-12-30 | 1982-12-14 | Water-absorbent resin having improved water- absorbency and improved water-dispersibility and process for producing same |
Country Status (6)
Country | Link |
---|---|
US (2) | US4507438A (en) |
EP (1) | EP0083022B1 (en) |
JP (1) | JPS6018690B2 (en) |
AT (1) | ATE33029T1 (en) |
CA (1) | CA1203039A (en) |
DE (1) | DE3278241D1 (en) |
Families Citing this family (364)
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JPS58180233A (en) * | 1982-04-19 | 1983-10-21 | Nippon Shokubai Kagaku Kogyo Co Ltd | Absorbing agent |
JPS601204A (en) * | 1983-06-20 | 1985-01-07 | Kao Corp | Production of highly water-absorptive resin |
JPS5962665A (en) * | 1982-09-02 | 1984-04-10 | Kao Corp | Preparation of polymer having high water-absorption |
JPS601205A (en) * | 1983-06-20 | 1985-01-07 | Kao Corp | Production of highly water-absorptive polymer |
JPS59189103A (en) * | 1983-04-11 | 1984-10-26 | Nippon Shokubai Kagaku Kogyo Co Ltd | Water-absorbing agent |
CA1256640A (en) * | 1984-03-05 | 1989-06-27 | Harumasa Yamasaki | Absorptive material |
JPS60185550A (en) * | 1984-03-05 | 1985-09-21 | 花王株式会社 | Absorbing material |
CA1261614A (en) * | 1984-04-27 | 1989-09-26 | Shmuel Dabi | Crosslinked carboxyl polyelectrolytes and method of making same |
JPS60255814A (en) * | 1984-05-31 | 1985-12-17 | Arakawa Chem Ind Co Ltd | Production of water-absorptive resin of improved gel strength |
JP2509087B2 (en) * | 1984-08-11 | 1996-06-19 | 三洋化成工業株式会社 | Water absorbent resin, manufacturing method and water absorbent, water retention agent |
GB8422950D0 (en) * | 1984-09-11 | 1984-10-17 | Warne K J | Hydrogel |
JPS61166809A (en) * | 1985-01-19 | 1986-07-28 | Hayashikane Zosen Kk | Highly water-absorbing powder |
JPS61225249A (en) * | 1985-03-29 | 1986-10-07 | Toyoda Gosei Co Ltd | Water-swelling composition |
JPS61257235A (en) * | 1985-05-08 | 1986-11-14 | Sanyo Chem Ind Ltd | Water absorbent resin composition, its preparation and water absorbent-water retention agent |
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US20240100506A1 (en) | 2020-12-16 | 2024-03-28 | Basf Se | Process for producing superabsorbent particles |
WO2023046583A1 (en) | 2021-09-27 | 2023-03-30 | Basf Se | Process for producing superabsorbent particles |
TWI805461B (en) | 2022-08-04 | 2023-06-11 | 臺灣塑膠工業股份有限公司 | Superabsorbent polymer and method for producing the same |
US20240091073A1 (en) | 2022-09-08 | 2024-03-21 | The Procter & Gamble Company | Disposable absorbent pants with elasticized waist panel structure and obscuring print patterns |
Family Cites Families (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS426674Y1 (en) * | 1966-10-22 | 1967-03-29 | ||
US3980663A (en) * | 1973-06-20 | 1976-09-14 | The Dow Chemical Company | Absorbent articles and methods for their preparation from crosslinkable solutions of synthetic carboxylic polyelectrolytes |
US3926891A (en) * | 1974-03-13 | 1975-12-16 | Dow Chemical Co | Method for making a crosslinkable aqueous solution which is useful to form soft, water-swellable polyacrylate articles |
US3966679A (en) * | 1974-05-09 | 1976-06-29 | The Dow Chemical Company | Absorbent articles and methods for their preparation |
US4041228A (en) * | 1974-05-09 | 1977-08-09 | The Dow Chemical Company | Absorbent articles and methods for their preparation |
US4043952A (en) * | 1975-05-09 | 1977-08-23 | National Starch And Chemical Corporation | Surface treatment process for improving dispersibility of an absorbent composition, and product thereof |
JPS5214689A (en) * | 1975-07-24 | 1977-02-03 | Sumitomo Chem Co Ltd | Process for preparing a macromolecular material excellent in water abs orption properties |
US4051086A (en) * | 1976-03-25 | 1977-09-27 | Hercules Incorporated | Absorption rate of absorbent polymers by treating with glyoxal |
JPS5346200A (en) * | 1976-10-08 | 1978-04-25 | Bucalo Louis | Method and device for controlling number of spermatozoons |
JPS6024807B2 (en) * | 1979-02-19 | 1985-06-14 | 昭和電工株式会社 | Method for producing super absorbent hydrogel |
JPS55119942A (en) * | 1979-03-07 | 1980-09-16 | Hitachi Ltd | Deccelerating valve |
JPS5626909A (en) * | 1979-08-13 | 1981-03-16 | Seitetsu Kagaku Co Ltd | Preparation of water-absorbing acrylic polymer |
JPS5693716A (en) * | 1979-12-27 | 1981-07-29 | Seitetsu Kagaku Co Ltd | Production of highly water-absorptive acrylic acid polymer |
JPS6025045B2 (en) * | 1980-03-19 | 1985-06-15 | 製鉄化学工業株式会社 | Method for producing acrylic acid polymer with excellent salt water absorption ability |
JPS56140571A (en) * | 1980-04-03 | 1981-11-02 | Matsushita Electric Ind Co Ltd | Magnetic recording and reproducing device of picture |
JPS5842602A (en) * | 1981-09-07 | 1983-03-12 | Sanyo Chem Ind Ltd | Production of water-absorbing resin |
-
1981
- 1981-12-30 JP JP56213885A patent/JPS6018690B2/en not_active Expired
-
1982
- 1982-12-09 US US06/448,150 patent/US4507438A/en not_active Expired - Lifetime
- 1982-12-14 AT AT82111579T patent/ATE33029T1/en not_active IP Right Cessation
- 1982-12-14 DE DE8282111579T patent/DE3278241D1/en not_active Expired
- 1982-12-14 EP EP82111579A patent/EP0083022B1/en not_active Expired
- 1982-12-14 CA CA000417618A patent/CA1203039A/en not_active Expired
-
1984
- 1984-08-07 US US06/638,601 patent/US4541871A/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
ATE33029T1 (en) | 1988-04-15 |
EP0083022A2 (en) | 1983-07-06 |
EP0083022B1 (en) | 1988-03-16 |
JPS6018690B2 (en) | 1985-05-11 |
JPS58117222A (en) | 1983-07-12 |
US4541871A (en) | 1985-09-17 |
EP0083022A3 (en) | 1984-05-30 |
US4507438A (en) | 1985-03-26 |
DE3278241D1 (en) | 1988-04-21 |
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