EP0664816A1 - Polymere absorbant l'eau presentant de meilleures proprietes - Google Patents

Polymere absorbant l'eau presentant de meilleures proprietes

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Publication number
EP0664816A1
EP0664816A1 EP93923399A EP93923399A EP0664816A1 EP 0664816 A1 EP0664816 A1 EP 0664816A1 EP 93923399 A EP93923399 A EP 93923399A EP 93923399 A EP93923399 A EP 93923399A EP 0664816 A1 EP0664816 A1 EP 0664816A1
Authority
EP
European Patent Office
Prior art keywords
water
crosslinking agent
surface crosslinking
crosslinked polymer
percent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93923399A
Other languages
German (de)
English (en)
Inventor
Andrew T. Graham
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US07/960,675 external-priority patent/US5447727A/en
Priority claimed from US07/975,171 external-priority patent/US5385983A/en
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Publication of EP0664816A1 publication Critical patent/EP0664816A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
    • C08F265/04—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of esters
    • C08F265/06—Polymerisation of acrylate or methacrylate esters on to polymers thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • 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

Definitions

  • the subject invention pertains to a surface-cross nked water-absorbent polymer having improved properties
  • the subject invention further pertains to a process for preparing such a polymer
  • the subject invention further pertains to a method of using such a polymer
  • Water-swell able polymers are used as constituents in personal care devices which absorb bodily fluids, such as sanitary napkins, incontinent devices and disposable baby diapers
  • bodily fluids such as sanitary napkins, incontinent devices and disposable baby diapers
  • Examples of such polymers are disclosed in U 5 Patent Nos 3,926,891 , 4, 190,562, and 4,293,609
  • Various processes are known for producing absorbent polymers For example,
  • U S Patent No 4,833,222 teaches a process for preparing an absorbent polymer from a neutralized monomer with a surface-active agent
  • U S Patent No 4,808,637 teaches the uniform reaction of acrylic acid, an alkali metal salt of carbonic acid, aluminum acetate, sodium sulfate and water, preferably using microwave radiation as a heat source to initiate polymerization
  • Another process com p ⁇ ses the steps of prepa ⁇ ng a reacti on m i xtu re consi sti ng essentially of particular amounts of polyme ⁇ zable acid group-containing monomers, crosslinking agent and optionally free radical initiator in an aqueous medium and thereafter polymerizing and neutralizing at least a portion of the acid functional groups
  • Absorbent polymers used in personal care devices are characterized by certain performance properties, including centrifuge capacity, absorbence under load, shear modulus, and percent extractables
  • U S Patent No 4,666,983 discloses an absorbent article obtained by mixing 100 parts by weight of an absorbent resin powder having a carboxyl group with 0 0001 to 10 oarts by weight of a crosslinking agent to crosslink the molecular chains existing at least in the vicinity of the surface of the absorbent resin powder
  • U S Patent No 4,734,478 discloses a water-absorbing resin powder having the molecular chains near its surface, the resin powder being obtained by mixing 100 parts by weight of a powder of a carboxyl-containing water-absorbing resin with 0 001 to 10 parts by weight of a polyhydric alcohol and heating the mixture at a temperature of at least 100°C o react the powder with the polyhydric alcohol, the improvement comprising conducting the mixing of the powder and the polyhydric alcohol in the presence of 0 01 to 8 parts by weight of a hydrophilic organic solvent and 0 to 8 parts by weight of water per 100 parts by weight of the powder
  • Japanese Kokai Publication 84632/1981 discloses an absorption agent consisting of a crosslinked poly(alkal ⁇ metal acrylate) material obtained from 0 01 to 10 parts by weight of a water-soluble and/or water dispersible surfactant and 0 005 to 20 parts by weight of a water- soluble polyvalent alcohol per 100 parts by weight of an acrylic acid/acrylate based polymer composed of
  • European Patent Application 248,963 discloses a process of post treatment wherein the surface of water-absorbent resin particles are treated with polyquarternary amines to significantly increase the absorption rate and to increase the absorption under load (AUL) by 10 percent
  • the polyquarternary amines are applied as solutions in methanol
  • European Patent Application 248,437 discloses a process for post surface crosslinking in which an aqueous solution of a water-soiuble peroxide radical initiator is sprayed onto the surface of the water absorbent resin particles and the coated particles are heated
  • the reference alleges the achievement of additional surface crosslinking, leading to a product of improved water absorbency and water absorption rate
  • the reference discloses that the uniformity of penetration of the aqueous solution into the surface of the absorbent polymer may be improved by using a water soluble organic solvent such as methanol
  • the disclosed process suffers the disadvantage of using high levels of peroxide free radical initiators, which discolors partly neutralized polyacrylic acid, making the product less appealing for personal care applications
  • the disclosed process suffers the further disadvantage of increasing the amount of extractable polymer, e g , low molecular weight water-soluble polymer, if the polymer is subjected to heat
  • German Patent DE 3,713,601 discloses a process in which surface crosslinking is obtained by the addition of a crosslmker of glycidyl or polyglycidyl compounds These crosslinking agents are not preferred in applications wherein the polymer is expected to contact human skin Industry would find great advantage in an aqueous fluid absorbent having improved absorbency under load and capacity Industry would further find great advantage in a process for producing such an aqueous fluid absorbent
  • the subject invention provides a water- absorbent polymeric material comprising a crosslinked polymer of a partially neutralized ⁇ , ⁇ - ethylenically unsaturated monomer, the crosslinked polymer being crosslinked with a primary crosslinking agent selected from the group consisting of methylenebisacrylamide, b ⁇ s(acrylam ⁇ do)acet ⁇ c acid and its salts, allyl acrylate, allyl methacrylate and esters or amides having both a vinyl and an allyl functionality, or highly ethoxylated t ⁇ methylolpropane t ⁇ acrylate, the crosslinked polymer being additionally crosslinked with a surface crosslinking agent, whereupon the molecular chains existing in the vicinity of the surface of the polymer are crosslinked
  • a primary crosslinking agent selected from the group consisting of methylenebisacrylamide, b ⁇ s(acrylam ⁇ do)acet ⁇ c acid and its salts, allyl acrylate, allyl methacrylate and esters or
  • the subject invention further provides a process for preparing an aqueous fluid absorbent material comprising (a) preparing a crosslinked polymer of a partially neutralized ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomer, the crosslinked polymer being crosslinked with a primary crosslinking agent selected from the group consisting of methylenebisacrylamide, b ⁇ s(acrylam ⁇ do)acet ⁇ c acid and its salts, allyl acrylate, allyl methacrylate and esters or amides having both a vinyl and an allyl functionality,
  • compositions of the subject invention will find great utility in personal care devices, where it is critical that the polymer have the capacity to hold substantial quantities of fluid, and retain such fluids upon the exertion of pressure, e g , upon s ⁇ tm 9
  • the subject invention provides a process for preparing an aqueous fluid absorbent material comprising-
  • a hydrogel comprising from 20 to 95 percent water-absorbent resin bearing carboxyl moieties and from 5 to 80 percent water with a composition comprising a surface crosslinking agent in the absence of a surfactant, the composition optionally further comprising additional water and/or a water miscible polar solvent, under conditions such that the surface crosslinking agent coats the hydrogel without substantial penetration into the interior of absorbent resin particles of the hydrogel to form a coated hydrogel;
  • water absorbent resin particles are prepared by either a gel polymerization process or by a reverse suspension polymerization process, both of which are well-known
  • hydrogel which is a water- swollen form of the polymer containing at least about 5 weight percent water
  • this hydrogel is subjected to mechanical means for reducing the oarticle size to granulate the hydrogel
  • the hydrogel is dried to remove the water
  • the particles are then typically subjected to further mechanical means of particle size reduction and classification including chopping, grinding, and sieving
  • Surface crosslinked refers to absorbent resi n polymer particles which are contacted with a crosslinking agent after completion of polymerization under conditions such that the particles are coated at or near the surface and the particles are exposed to conditions such that the surface crosslinking agent reacts with carboxyl groups at or near the surface of the particle to crosslink the water absorbent resin
  • Hydrogel as used herein, means water swollen absorbent resin particles In preferred embodiments, such hydrogels comprise from 15 to 95 percent by weight water absorbent polymer, with the remainder comprising water In a more preferred embodiment, the hydrogel comprises from 30 to 95 percent water absorbent polymer In a most preferred embodiment, the hydrogel comprises from 80 to 95 percent water-absorbent polymer
  • the surface crosslinking agent may be applied at nearly any stage in the production process.
  • the surface crossl i nking agent may be applied to wet hydrogel exiting the reactor having a water content from 65 to 80 percent; to partially dried hydrogel having a water content between 15 and 35 percent, to more fully dried hydrogel having a water content between 5 and 15 percent, or to a polymer powder, having a water content less than about 5 percent
  • the water-swellable or lightly crosslinked hydrophihc polymers that are usefully used in the present invention can be any of the known hydrophihc polymers which are capable of absorbing large quantities of fluids
  • water-absorbent polymers useful in this invention are water-absorbent polymers which contain carboxyl moieties Preferably, at least about 0.01 equivalent of carboxyl groups are present per 100 grams of the water-absorbent resin
  • carboxyl-containing water absorbent polymers are hydrolyzates of starch-acrylonit ⁇ le graft copolymers, partially neutralized products of starch- acrylic acid graft copolymers, saponification products of vinyl acetate acrylic ester copolymers, hydrolyzates of acrylonit ⁇ le copolymers, crosslinked products of hydrolyzates of acrylonit ⁇ ie copolymers, hydrolyzates of acrylamide copolymers, crosslinked products of hydrolyzates of acryiamide copolymers, partially neutralized products of polyacrylic acids and crosslinked products of partially neutralized polyacrylic acids
  • Suitable ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomers include, for example, acrylic acid, methacry c acid, crotonic acid, isocrotonic acid and alkali metal salts and ammonium salts thereof, maleic acid, fumanc acid, itaconic acid, acrylamide, methacrylamide and 2-acrylam ⁇ do- 2-methyl-1-propane sulfon ⁇ c ac ⁇ d and its salts
  • the preferred monomers include acrylic acid and
  • the water-soluble monomers useful in the present invention may be used in amounts ranging from 10 percent to 80 percent by weight based on the total weight of the aqueous monomer solution Preferably, the amount ranges from 20 percent to 60 percent based on the total weight of the aqueous monomer solution
  • the minor amounts of other water-soluble, unsaturated monomers such as alkyl esters of the acid monomers, e g , methyl acrylate or methyl methacrylate may be present
  • certain grafting polymers such as, for example, polyvinyl alcohol, starch and water soluble or swellable cellulose ethers may be employed to prepare products having superior properties Such grafting polymers, when employed, are used in amounts up to about
  • chelating agent to remove trace metals from solution, e g , when a metal reaction vessel is employed
  • a metal reaction vessel is employed
  • VERSENEX V-80 an aqueous solution of the pentasodium salt of diethylenetriamme pentacetic acid
  • Such chelating agents when employed, are generally used in
  • the polymerization may be carried out using acid monomers that are not neutralized or that have been neutralized or partially neutralized prior to the polymerization Neutralization is conveniently achieved by contacting the aqueous monomer with an amount
  • the amount of basic material will be sufficient to neutralize between 40 percent and 85 percent, and most preferably between 55 percent and 75 percent of the acid groups present in the acid monomers
  • the neutralization is advantageously carried out at temperatures below 40°C, preferably at temperatures below 35 C C
  • Compounds which are useful to neutralize the acid groups of the monomer are typically those which will sufficiently neutralize the acid groups without having a detrimental effect on the polymerization process
  • Such compounds include alkali metal hydroxides, alkali metal carbonates and bicarbonates
  • the material used to neutralize the monomer is sodium or potassium hydroxide or sodium carbonate or potassium carbonate In determining the desired degree of neutralization, care must be taken to ensure that the pH of the resulting crosslinked absorbent polymer, which will be contacted
  • the water-absorbent resin will preferably be lightly crosslinked to render it water-insoluble
  • the desired crosslinked structure may be obtained by the copolyme ⁇ zation of the selected water-soluble monomer and a crosslinking agent possessing at least two polyme ⁇ zable double bonds in the molecular unit
  • the crosslinking agent is present in an amount effective to crosslink the water-soluble polymer
  • the preferred amount of crosslinking agent is determined by the desired degree of absorption capacity and the desired strength to retain the absorbed fluid, i e , the desired absorption under load (AUL)
  • the crosslinking agent is used in amounts ranging from 0 0005 to 5 parts by weight per 100 parts by weight of ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomer used More preferably, the amount ranges from 0 1 to 1 part by weight per 100 parts by weight of the ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomer If an amount over about 5 parts by weight of crosslinking agent per 100 parts is used, the
  • Suitable dispersing agents include carboxymethyl cellulose suspending aids, methyl cellulose, hydroxypropyl cellulose, and polyvinyl alcohol Such dispersing agents are typically provided at a concentration between 0 005 and 0 1 weight 0 percent, based on the total weight of ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomer reactants
  • Preferred crosslinking agents include trimethylolpropanet ⁇ acrylate, ethoxylated trimethylol propanet ⁇ acrylate, butyleneglycoldiacrylate, ethyleneglycoldi methacrylate, ethylenebisacrylamide and diallylcarbonate, methylenebisacrylamide, b ⁇ s(acrylam ⁇ do)acet ⁇ c acid and its salts, allyl acrylate, allyl methacrylate and difunctional monovinyl and monoallyl 5 esters and amides
  • crosslinking agents yields particularly preferred absorptive properties
  • preferred crosslinking agents include methylenebisacrylamide, b ⁇ s(acrylam ⁇ do)acet ⁇ c acid and its salts, allyl acrylate, allyl methacrylate and esters or amides having both a vinyl and an allyl functionality
  • crosslinking agents such as highly ethoxylated tnmethylolpropane triacrylate
  • highly ethoxylated 5 tnmethylolpropane triacrylate is a C 2 - ⁇ o polyhydric hydrocarbon which has been ethoxylated with from two to eight ethylene oxide units per hydroxyl moiety of the ethylene oxide chain wherein the hydroxy moiety at the end of each chain is este ⁇ fied with a 2 - ⁇ o unsaturated carboxyhc acid or ester thereof
  • highly ethoxylated tnmethylolpropane triacrylate is trimethylol propane which has been ethoxylated with 2 to 7 ethylene oxide units 0 per hydroxy moiety and wherein each hydroxy moiety has been este ⁇ fied with an acrylate moiety
  • an aqueous solution of the ⁇ , ⁇ -ethylen ⁇ cally unsaturated monomer in the partially neutralized form, the crosslinking agent, the initiator and a grafting polymer substrate, if 5 desired is prepared
  • the polymerization of the mixture may be initiated by elevating the temperature of the mixture containing the initiator or by using a redox-type initiator as described above Generally, the temperature at which polymerization will begin ranges from 20°C to 45°C
  • the temperature at which the polymerization is carried out is highly dependent on the type of monomers used and the specific initiator system employed
  • the maximum temperature of polymerization ranges from 50°C to 100 C C, most preferably from 60° to 100°C
  • the method by which the temperature of the polymerization is controlled is not critical so long as sufficient cooling is present to remove the heat which is generated during the polymerization
  • the resultant hydrogel typically contains from 20 to 35 weight percent water- absorbent polymer and from 65 to 80 percent water
  • the hydrogel is typically initially mechanically sized to form sized hydrogel particles having a reduced size prior to drying Typically, such sized hydrogel particles have an average diameter less than about 2 cm
  • the sized hydrogel oartides are typically dried using means well-known in the art
  • drying means include fluidized bed driers, rotary driers, forced air ovens, through circulation band driers, etc
  • drying will occur in two or more stages
  • the sized hydrogel particles are partially dried in the first stage, e g , the size hydrogel particles are dried to less than 10 percent moisture level, preferably a 5 percent moisture level
  • the hydrogel particles tend to fuse together to form a sheet
  • the partially dried hydrogel sheets are broken to form pieces which are very roughly about 10 cm x 10 cm x 2 cm in dimension
  • Such pieces are then more fully dried in the second stage, e g , are dried to a moisture level less than about 5 percent Following the completion of drying the pieces are more fully sized to form particles having an average diameter less than about 0 8 mm
  • the polymer particles are surface crosslinked with a suitable surface crosslinking agent
  • suitable surface crosslinking agent include polyhydroxyl compounds, polyglycidyl ether compounds, polyfunctional azi ⁇ dine compounds, polyfunctional amine compounds and polyfunctional isocyanate compounds, with polyhydroxy compounds being especially preferred
  • the polyhydroxy compound which is used as a surface crosslinking agent is a compound which contains at least two hydroxyl groups which are capable of readily reacting with the carboxyl groups of the water-absorbent resin of the hydrogel Suitable polyhydroxy compounds will not volatilize or degrade at the temperature of heating
  • the polyhydroxy compound used in this invention is selected from the group consisting of glycol, diethylene glycol, t ⁇ ethylene glycol, polyethylene glycols, glycerol, polyglycerol, polyethoxylated glycerol, propylene glycol, polypropylene glycols, diethanolamine, t ⁇ ethanolamine, polyethylene oxide, propane diol, butane diol, hydroxy terminated oxyethylene-oxypropylene block copolymers, tnmethylolpropane, pentaeryth ⁇ tol, sorbitol, mannitol, sugars, sugar derivatives, polyoxyethylene sorbitol derivatives, polyoxyethylenelanolin derivatives, polye
  • polyglycidyl ether compounds are ethylene glycol diglycidyl ether and glycerin diglycidyl ether
  • polyfunctional azi ⁇ dine compounds are 2,2- b ⁇ shydroxymethylbutanol-tr ⁇ s[3-(1-az ⁇ r ⁇ d ⁇ nyl)prop ⁇ onate], sold under the tradename Chemitite PZ-33, 1 ,6-hexamethylened ⁇ ethyleneurea, sold under the tradename Chemitite HZ-22, and d ⁇ phenylmethaneb ⁇ s-4,4'-N,N'-d ⁇ ethyloneurea, sold under the tradename Chemitite DZ-22, all of which are manufactured by Nippon Shokubai Kagaku Kogyo Co , Ltd
  • Specific examples of the polyfunctional amines are ethylenediamine, t ⁇ ethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneamineamine
  • the surface crosslinking agent is present in an amount effective to crosslink the surface of the polymer Such amount is determined by the desired capacity and AUL of the final polymer Ideally, such amount should significantly improve the gel strength of the polymer, as evidenced by an increased absorption under load (AUL), while not significantly reducing the capacity of the resin
  • the surface crosslinking agent is used in amounts ranging from 0 00002 to 10 parts by weight of the essentially dried absorbent resin product More preferably, the amount ranges from 0 0002 to 0 005 parts by weight per 1 part by weight of dried absorbent resin product, ⁇ e , from 200 to 5000 ppm based on the weight of the dried absorbent resin product
  • the surface crosslinking agent will be provided in an amount of at least 300 ppm, more preferably at least 500 ppm, and more preferably at least 1000 ppm, and most preferably at least 3000 ppm based on the weight of the d ⁇ ed polymer
  • the surface crosslinking agent may be applied at any stage of the
  • composition containing the surface crosslinking agent may include a surfactant to facilitate a homogeneous distribution of the surface crosslinking agent on the polymer particles, to improve the processabihty of the coated polymer particles, to reduce the tendency of the dried powder to agglomerate when exposed to humid air or water, and/or to bind fine dust of the water-absorbent resin
  • Suitable surfactants are nonionic surfactants which are dispersible in water and which have an HLB value in the range of from 3 to 10
  • Preferred surfactants are those selected from the group of sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerol or polyglycerol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene acyl esters, o and sucrose fatty acid esters or modified surface active polyesters
  • Such surfactants are preferably used in an amount from 0 01 to 2 parts per 100 parts by weight of the water-absorbent resin, more preferably from 0 075 to 0 5 parts per 100 parts by weight of the water-absorbent resin
  • the surfactant When the surfactant has two or more hydroxyl moieties capable of reacting with 5 carboxyl moieties, the surfactant can be used both as a polyhydroxy compound, e g , surface crosslinking agent, and as a surfactant.
  • a polyhydroxy compound e g
  • surface crosslinking agent e.g
  • certain polyhydroxy compounds which serve as surface crosslinking agents may also serve as surfactants
  • One example of such a polyhydroxy compound is a polyethoxylated sorbitol lanolin derivative
  • the hydrogels/powders and the surface crosslinking agent should be contacted 0 under conditions such that the particles can be coated with the surface crosslinking agent, but such that the surface crosslinking agent does not significantly diffuse into the internal structure of the water-absorbent resin particle
  • such contacting will be conducted with some form of mechanical distribution, such that adequate distribution of the surface crosslinking agent on the water-absorbent resin particles occurs Grinding, followed by moderate stirring, 5 shaking, or even a short distance of conveying in a screw-conveyer is sufficient for such adequate distribution of the surface crosslinking agent over the hydrogel particles, particularly if the hydrogel particles are at an elevated temperature
  • neat surface crosslinking agent may be applied to the partially dried sized hydrogel particles exiting the first stage of a two-stage drier, whereupon the surface crosslinking agent is distributed over the surfaces of 0 the particles during a mechanical sizing operation that occurs after the completion of drying but prior to heat treatment
  • the temperature of contacting can be any temperature at which the surface crosslinking agent does not significantly react with the carboxyl moieties of the absorbent resin polymer Such temperatures are typically at least from 20 to 150°C It should be noted that 5 elevated temperatures, i e., those above ambient temperatures, improve the speed of coating of the hydrogel particles
  • the hydrogel Upon application of the surface crosslinking agent to a hydrogel, the hydrogel is dried to a moisture level less than about 5 weight percent Preferably, the hydrogel is dried to a moisture level from 1 to 5 weight percent. Should the surface crosslinking agent be applied to the hydrogel prior to any drying, e.g., straight from the reactor, the drying will obviously require more time than should the surface crosslinking agent have been applied at some point downstream from the reactor, e.g., after passage through the first stage of a two-stage drier.
  • the temperature at which the drying takes place is a temperature high enough such that the water and any optional organic solvent is removed in a reasonable time period, yet not so high as to react the surface crosslinking agent with the carboxyl moieties of the water-absorbent resin.
  • the temperature of the water-absorbent resin particles during drying is about 170°C or less. More preferably, the temperature during drying is from
  • the drying time should be sufficient to remove substantially all of the water and the optional solvent in a reasonable time period, and will depend on the drying system employed. Typically, the drying will reduce the moisture level of the hydrogel to a level from 1 to 5 weight percent.
  • the coated hydrogel will preferably be subjected to mechanical particle reduction means, e.g., chopping, cutting, and/or grinding.
  • mechanical particle reduction means serve to reduce the particle size of the water-absorbent resin particles to a particle size acceptable in the ultimate end use.
  • mechanical particle reduction will further preferably serve to distribute the surface crosslinking agent over the mechanically reduced particles.
  • the coated absorbent resin particles are sized by first chopping, and then grinding.
  • the resultant particle size is less than 2 mm, and is more preferably less than 0.8 mm.
  • the resultant particles have a size of at least 0.04 mm, more preferably at least 0.07 mm, and most preferably greater than 0.1 mm.
  • the surface crosslinking agent is applied to a powder, e.g., to a sized product having a moisture content less than about 5 weight percent
  • the surface crosslinking agent is applied with mixing by a ribbon mixer, screw mixer, fluidized bed mixer, V- shaped rotating mixer, etc.
  • the mixed dried powder is then heat treated in the above manner.
  • Application of the surface crosslinking agent, mixing, and heat treatment may advantageously
  • the water-absorbent resin particles are subjected to conditions such that the polyhydroxy compound reacts with the carboxyl moieties of the water absorbent resin, so as to crosslink the water-absorbent resin at or near the surface of the particles.
  • the dried and coated water-absorbent resin particles are heated
  • Such heat treatment is preferably carried out at a temperature of at least about 170, more preferably of at least 180, and most preferably of at least about 190°C.
  • Such heat treatment is preferably carried out at a temperature of less than about 250, more preferably less than about 230 and most preferably less than about 210°C
  • the time period for heat treatment should be sufficient for the surface crosslinking agent present at or near the surface of the absorbent resin to react with the carboxyl moieties
  • the exacttimes of heat treatment required will be affected by the equipment chosen, and can be determined empirically by examination of product properties
  • the time is at least about 3 minutes, and more preferably at least about 5 minutes If the time is too long, the process becomes uneconomical and a risk is run that the absorbent resin may be damaged
  • the maximum time of heating is about 150 minutes or less, o more preferably 60 minutes or less
  • the method of heat treatment is not critical
  • forced air ovens, fluidized bed heaters, heated screw conveyors, and the like may be successfully employed
  • the coated and heated polymer may be remoistu ⁇ zed for ease in handling
  • an absorbent resin may be obtained by dispersing an aqueous solution of ac /lie acid/acrylate containing a water-soluble free radical polymerization initiator and one of the primary crosslinking agents set forth above in an alicychc and/or an aliphatic hydrocarbon solvent in the 0 presence of a suspending aid, and subjecting the mixture to suspension polymerization
  • the resultant polymer beads are dried to remove residual solvent
  • the surface crosslinking agent is then applied to the dried beads with mixing, such as a ribbon mixer, a screw mixer, a rotating disc mixer, a fluidized bed mixer, a V-shaped rotating mixer, etc
  • the mixed dried beads are then heat treated in the manner specified above Application of the surface crosslinking agent, 5 mixing, and heat treatment may advantageously occur simultaneously, e g , in the case of a fluidized bed mixer
  • sixty minute 0 3 psi AUL was measured as described in European Patent Application EP 339,461-A1
  • sixty minute 0 6 ps ⁇ AUL was measured in the 0 manner described for the measurement of 0 3 psi AUL, except that a 0 6 ps ⁇ pressure rather than a 0 3 psi pressure was applied and except that the test time was 90 minutes rather than 60 minutes
  • centrifuge capacity was determined as described in U S Patent 4,286,082 except that an absorption time of 30 minutes rather than 3 to 5 minutes was employed
  • fish eyes formation was determined as described in U S Patent No 4,666,983
  • the extractables and modulus 5 were determined as descr bed in U S Reissue Patent 32,649, with the relevant portions of ea of the cited references being incorporated herein by reference
  • vortex time was taken as the time for the vortex to disappear when 2 grams of polymer was added to 50 grams of a 0 9 percent
  • Comparative Example 1-A A portion of the material of Comparative Example 1-A was 0 heat treated for 35 minutes at 210°C to form Comparative Example 1-B The remainder of the unground and unscreened material was treated by weighing portions of the dried resin mass and weighing enough glycerine onto each portion to give the indicated amount of glycerin based on dry solids Samples of each portion were ground and screened to pass through a 100 mesh sieve, and were heat treated for 35 minutes at 210°C to form Examples lA and 1 B 5 The results of Examples 1A, 1 B, and Comparative Examples 1-A and 1-B are set forth in Table One Example Two
  • Comparative Example 2-A A portion of the material of Comparative Example 2-A was heat treated for 35 m ⁇ nutes at 210°C to form Comparative Example 2-B The remainder of the unground and unscreened material was treated by weighi ng portions of the dried resin mass and weighing enough glycerine onto each portion to gi e the indicated amount of glycerin based on dry solids. Samples of each portion were ground and screened to pass through a 100 mesh sieve, and were heat treated for 35 minutes at 210°C to form Examples 2A and 2B The results of Examples 2A, 2B, and Comparati e Examples 2-A and 2-B set forth in Table One
  • Examples One and Two demonstrate that i mproved absorption rate and reduced fish eye formation and gel blocking can be obtained with a surface crosslinki ng agent is appl ied to the dry or partially dry absorbent resin polymer mass prior to grinding
  • the surface crossl inking agent can be applied in a range of at least from 300 to 3000 ppm, based on dry solids
  • the resultant gel was separated into five parts for drying and coati ng with glycerin Glycerin was added dropwise to the gel,at the drying stage extrapolated from the indicated percent moisture of the sample, in order to give about 500 ppm glycerine, based on the final dried weight of the polymer
  • samples of the resi n mass were taken Fol lowing addition of the glycerin, the samples were d ⁇ ed to a moisture level of 5 percent and were ground and screened.
  • Comparative Example 4-A represents an uncoated, non-heat treated sample of Example 4A.
  • Comparative Example 4-B rcQresents the uncoated sample of Comparative Example 4-A which has been heat treated
  • Example Five In a beaker, 300 grams acrylic acid 0 75 grams VERSENEX V-80 chelating agent,
  • the resultant gel was separated into four parts and was dried in a standard commercial forced air oven. When dry, one portion of the material was ground and saved as Comparative Example 5-1. Other portions of the material were treated by weighing the portions and weighing the indicated amount of glycerin onto the portions The coated portions were placed i n a food blender and were ground and screened to a 20 to 100 mesh cut The sized and coated portions were placed in a jar and tumbled in a roller mixer for an additional 1 5 to 30 minutes The samples were tnen placed in a forced ai r oven at 200°C for 40 minutes to react the glycerin with the carboxyl groups on the absorbent resin One of the sized portions was not coated with glycerin, but was heat treated as described, resulti ng i n Comparative Example 5-2. The final products (Examples 5A, 5B, and 5C) and the products of the comparative examples were analyzed The results of Examples 5A, 5B, 5C, and Comparative Examples 5-1 and
  • Example 6 Polymerizations were carried out in the same manner as described i n Example 5, excepti ng that the glyceri n was replaced with the i ndicated coating material Table Four lists the coating material (surface crossli nking agent), the amount of coating material used, and the product properties after heat treatment.
  • Examples 6A, 6B, 6C, 6D and 6E are examples of the invention. Comparative examples 6-A1 , 6-A2, 6-A3, 6-A4, and 6-A5 correspond to examples 6A, 6B, 6C, 6D and 6E, excepting that the comparative examples represent uncoated samples which have not been heat treated.
  • Comparative examples 6-B 1 , 6-B2, 6-B3, 6-B4, and 6-B 5 correspond to examples 6A, 6B, 6C, 6D and 6E, excepting that the comparative examples represent uncoated samples which have been heat treated in the manner for heat treating the samples of Examples 6A, 6B, 6C, 6D and 6E
  • the final products (Examples 6A, 6B, 6C, 6D and 6E) and the products of the comparative examples were analyzed T e results of Examples 6A, 6B, 6C, 6D, 6E, of Comparative Examples 6-A1 , 6-A2, 6-
  • Example Seven 0.95 grams methylenebisacrylamide crosslinking agent was added, the mixture was added to a reactor, and the reactor was purged with nitrogen.
  • Example Eight 0.95 grams allyl methacrylate crosslinking agent was added, the mixture was added to a reactor, and the reactor was purged with nitrogen.
  • the resultant gels were each separated into two parts and were dried in a standard commercial forced air oven. When dry, one portion of each material was ground and saved as Comparative Examples 7-1 , 7-2, 8-1 and 8-2. Other portions of the material were treated by weighing the portions and weighing the indicated amount of the surface 0 crosslinking agent onto the portions. The coated portions were placed in a food blender and were ground and screened to a 20 to 100 mesh cut. The sized products were coated with the indicated amount of coating material and were placed in a jar and tumbled in a roller mixer for an additional 15 to 30 minutes. The samples were then placed in a forced air oven at 200°C for 40 minutes to react the hydroxyl groups of the coating materials with the carboxyl groups on 5 the absorbent resin. The final products (Examples 7A, 7B, 7C, 7D, 8A, 8B, 8C, and 8D) and the products of the comparative examples (7-1 , 7-2, 8-1 , and 8-2) were analyzed.
  • Examples 7A, 7B, 7C, 7D, 8A, 8B, 8C, and 8D and comparative examples 7-1 , 7-2, 8-1 , and 8-2 are set forth in Table Five.
  • Example 9-1 is a heat treated uncoated sample. The results of Examples 9A, 9B, 9C and comparative example 9-1 are set forth in
  • Example Ten demonstrates the applicability of heat treating temperatures between 180 and 200°C in the practice of the subject invention.
  • Example Ten further demonstrates the shift in product properties that occurs as a function of the time for heat treatment.
  • a portion of the polymer was weighed into a container, and to it was added 250 grams of an 80/20 propanol/water solution containing glycerine, such that the weight of glycerine to the weight of polymer was 0.2 percent. This material was dried overnight at 100°C. Subsequently, this material was dried in an open glass container in a 180°C oven for 40 minutes. The 0.3 psi AUL was 31.7 g/g, the centrifuge capacity was 36.1 g/g, and the 16 hour extractables were 14 percent.
  • a polymerization is conducted in the same manner as described in Example Five.
  • the gel is dried and ground using a food blender and screened to a 20 to 100 mesh cut Glycerin is added to the powder at a 500 ppm level.
  • the sample is tumbled for 15 to 20 minutes on a roller mixer.
  • the samples are then placed in a forced air oven at 200°C for 40 minutes.
  • the 0.3 psi AUL is about 30 g/g
  • the centrifuge capacity is about 35 g/g
  • the 16 hour extractables are about 8 percent.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Epidemiology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
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  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • General Chemical & Material Sciences (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

Selon un mode de réalisation, la présente invention se rapporte à un polymère réticulé en surface absorbant l'eau et présentant de meilleures propriétés et à son procédé de préparation. On obtient les propriétés d'absorption désirées par l'utilisation d'un agent de réticulation principal préféré couplé avec une réticulation en surface. Des agents de réticulation principaux appropriés comprennent le méthylènebisacrylamide, l'acide bis(acrylamido)acétique et ses sels, l'acrylate d'allyle, le méthacrylate d'allyle et des esters ou amides ayant aussi bien une fonction vinyle qu'une fonction allyle. Selon un autre mode de réalisation, l'invention se rapporte à un procédé de préparation d'un polymère absorbant l'eau par l'addition d'un agent de réticulation en surface à un hydrogel en l'absence d'un tensioactif.
EP93923399A 1992-10-14 1993-10-14 Polymere absorbant l'eau presentant de meilleures proprietes Withdrawn EP0664816A1 (fr)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
US96067492A 1992-10-14 1992-10-14
US07/960,675 US5447727A (en) 1992-10-14 1992-10-14 Water-absorbent polymer having improved properties
US960675 1992-10-14
US960674 1992-10-14
US07/975,171 US5385983A (en) 1992-11-12 1992-11-12 Process for preparing a water-absorbent polymer
US975171 1992-11-12
PCT/US1993/009848 WO1994009043A1 (fr) 1992-10-14 1993-10-14 Polymere absorbant l'eau presentant de meilleures proprietes

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Families Citing this family (33)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69524928T2 (de) * 1994-06-13 2002-08-29 Nippon Shokubai Co. Ltd., Osaka Wasser-absorbent, verfahren zu dessen herstellung und den enthaltender absorbent-gegenstand
USRE38444E1 (en) 1994-06-13 2004-02-24 Nippon Shokubai Co., Ltd. Absorbing agent, process of manufacturing same, and absorbent product containing same
DE19543368C2 (de) * 1995-11-21 1998-11-26 Stockhausen Chem Fab Gmbh Wasserabsorbierende Polymere mit verbesserten Eigenschaften, Verfahren zu deren Herstellung und deren Verwendung
DE19543366C2 (de) * 1995-11-21 1998-09-10 Stockhausen Chem Fab Gmbh Mit ungesättigten Aminoalkoholen vernetzte, wasserquellbare Polymerisate, deren Herstellung und Verwendung
ID19116A (id) * 1996-10-15 1998-06-18 Nippon Catalytic Chem Ind Bahan pengabsorpsi air dan proses produksinya
US6184433B1 (en) 1997-04-14 2001-02-06 Nippon Shokubai Co., Ltd. Pressure-resistant absorbent resin, disposable diaper using the resin, and absorbent resin, and method for production thereof
DE19716657A1 (de) 1997-04-21 1998-10-22 Stockhausen Chem Fab Gmbh Superabsorber mit kontrollierter Absorptionsgeschwindigkeit
DE19717394C2 (de) * 1997-04-24 2001-11-29 Stockhausen Chem Fab Gmbh Druckfähige Einkomponentenquellpaste und deren Verwendung
US5856410A (en) * 1997-05-23 1999-01-05 Amcol International Corporation Polyacrylate superabsorbent post-polymerization neutralized with solid, non-hydroxyl neutralizing agent.
US6187902B1 (en) 1997-12-25 2001-02-13 Nippon Shokubai Co., Ltd. Production process of hydrophilic crosslinked polymer
US6254990B1 (en) 1998-02-18 2001-07-03 Nippon Shokubai Co., Ltd. Surface-crosslinking process for water-absorbent resin
DE19807502B4 (de) * 1998-02-21 2004-04-08 Basf Ag Verfahren zur Nachvernetzung von Hydrogelen mit 2-Oxazolidinonen, daraus hergestellte Hydrogele und deren Verwendung
US6503979B1 (en) * 1998-02-26 2003-01-07 Basf Aktiengesellschaft Method for cross-linking hydrogels with bis- and poly-2-oxazolidinones
JP2009154155A (ja) * 1998-03-03 2009-07-16 Nippon Shokubai Co Ltd 吸水剤の製造方法
JP4141526B2 (ja) 1998-04-07 2008-08-27 株式会社日本触媒 吸水性樹脂の製造方法
JP2010214371A (ja) * 1998-04-15 2010-09-30 Nippon Shokubai Co Ltd 吸水剤、吸収体、吸収性物品、および吸収特性の測定方法
JP4942235B2 (ja) * 1998-04-15 2012-05-30 株式会社日本触媒 吸水剤、吸収体、吸収性物品、および吸収特性の測定方法
DE19825486C2 (de) 1998-06-08 2000-07-06 Stockhausen Chem Fab Gmbh Wasserabsorbierende Polymere mit supramolekularen Hohlraummolekülen, Verfahren zu deren Herstellung und deren Verwendung
DE19854574A1 (de) * 1998-11-26 2000-05-31 Basf Ag Verfahren zur Nachvernetzung von Hydrogelen mit N-Acyl-2-Oxazolidinonen
DE19854573A1 (de) 1998-11-26 2000-05-31 Basf Ag Verfahren zur Nachvernetzung von Hydrogelen mit 2-Oxo-tetrahydro-1,3-oxazinen
US6297335B1 (en) * 1999-02-05 2001-10-02 Basf Aktiengesellschaft Crosslinked, hydrophilic, highly swellable hydrogels, production thereof and use thereof
DE19939662A1 (de) 1999-08-20 2001-02-22 Stockhausen Chem Fab Gmbh Wasserabsorbierende Polymere mit Hohlraumverbindungen, Verfahren zur deren Herstellung und deren Verwendung
US6414214B1 (en) * 1999-10-04 2002-07-02 Basf Aktiengesellschaft Mechanically stable hydrogel-forming polymers
US6569910B1 (en) * 1999-10-27 2003-05-27 Basf Aktiengesellschaft Ion exchange resins and methods of making the same
WO2001079314A1 (fr) * 2000-04-13 2001-10-25 Sanyo Chemical Industries, Ltd. Polymere reticule, procede de preparation associe, structure absorbante et article absorbant
US7101946B2 (en) 2002-02-14 2006-09-05 Stockhausen Gmbh Water-absorbing polymers having interstitial compounds, a process for their production, and their use
EP1680470B1 (fr) 2003-11-07 2016-02-03 Nippon Shokubai Co., Ltd. Composition de resine hydrophile particulaire et son procede de production
US7163966B2 (en) * 2003-12-19 2007-01-16 Stockhausen, Inc. Superabsorbent polymer having increased rate of water absorption
DE102004055765A1 (de) 2004-11-18 2006-05-24 Basf Ag Verfahren zur Herstellung wasserabsorbierender Polymere
SA08290542B1 (ar) 2007-08-28 2012-11-14 نيبون شوكوباي كو. ، ليمتد طريقة لإنتاج راتنج ماص للماء
FR3005660B1 (fr) * 2013-05-17 2015-04-24 Arkema France Procede de reticulation en surface de particules de polymere
KR102909465B1 (ko) * 2020-08-25 2026-01-09 킴벌리-클라크 월드와이드, 인크. 흡수성 구조체 및 흡수성 구조체 제조 방법
CN117229595B (zh) * 2023-09-18 2026-03-24 北京航空航天大学 一种高吸水凝胶及其制备方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5842602A (ja) * 1981-09-07 1983-03-12 Sanyo Chem Ind Ltd 吸水性樹脂の製造法
CA1256640A (fr) * 1984-03-05 1989-06-27 Harumasa Yamasaki Materiel absorbant
US4734478A (en) * 1984-07-02 1988-03-29 Nippon Shokubai Kagaku Kogyo Co., Ltd. Water absorbing agent
US4783510A (en) * 1986-06-04 1988-11-08 Taiyo Fishery Co., Ltd. Process for improving a water absorbent polyacrylic acid polymer and an improved polymer produced by said process
JPH01207327A (ja) * 1987-10-29 1989-08-21 Nippon Shokubai Kagaku Kogyo Co Ltd 吸水性樹脂の表面処理方法
US5164459A (en) * 1990-04-02 1992-11-17 Nippon Shokubai Kagaku Kogyo Co., Ltd. Method for treating the surface of an absorbent resin

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9409043A1 *

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AU5329994A (en) 1994-05-09
WO1994009043A1 (fr) 1994-04-28
BR9307292A (pt) 1999-06-01
KR950703583A (ko) 1995-09-20

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