CA2082623A1 - Water-absorbent resin particles for absorbent structures - Google Patents
Water-absorbent resin particles for absorbent structuresInfo
- Publication number
- CA2082623A1 CA2082623A1 CA 2082623 CA2082623A CA2082623A1 CA 2082623 A1 CA2082623 A1 CA 2082623A1 CA 2082623 CA2082623 CA 2082623 CA 2082623 A CA2082623 A CA 2082623A CA 2082623 A1 CA2082623 A1 CA 2082623A1
- Authority
- CA
- Canada
- Prior art keywords
- water
- absorbent resin
- absorbent
- resin particles
- flow control
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
- C08J3/124—Treatment for improving the free-flowing characteristics
-
- 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
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/14—Water soluble or water swellable polymers, e.g. aqueous gels
Abstract
Water-absorbent resin particles comprising a carboxyl containing water-absorbent resin characterized in that the water-absorbent resin is rendered adhesive by the incorporation of a thermoplastic polymer with hydrophilic character. Optionally, a flow control additive is also employed. In another embodiment the invention comprises water-absorbent structures or articles which comprise a woven or nonwoven mass of fibers of a desired shape characterized in that adhesivized water-absorbent resin particles of the invention are bound to the fibers of the woven or nonwoven mass of fibers. The particles must be prepared by blending water-absorbent resin particles containing carboxyl moieties with a thermoplastic resin having hydrophilic character until the mixture no longer flows freely and, optionally, adding to the water-absorbent resin particles and thermoplastic polymer mixture a flow control additive and blending until the mixture flows freely.
Description
.~ 1 . ,.
2 ~3~5~3 WATER-ABSORBENT RESIN PARTICLES FOR ABSORBENT STRUCTURES
:~ This invention relates to novel water-absorbent resin particles, a process or the preparation of such ~ :
water-absorbe~t resin particles and to absorbent ::
. . .
; 5 structures contai~ing the water-absorbe~t resin ' particles. The invention further relates to water-;~ absorbent resin compositions with improved aqueous fluid absorption properties, and ~ater-absorbent structures co~taining these water-absorbent resin compositions.
. , , ., . .;
It is kno~n to form woven and non-woven structures `of celluloisic f;bers5 ~iatural cotton fibers, sy~thetic fibers or mixt~res thereof for use in .
~absorbing aqueous fluids.-I~ one example, the fibers are formed into op~n-structured absorbe~ webs~ and i~ .
~ Y~ r ~ J ~ ; L; , " ~
another, the ~ibers are thermally bonded to.form co~pLex s~ructures. The flbers used 1~ such structures ca~ , quickly absorb aqueous 1uids and distribute them over the whole absorbent structure by capillary forces~ The .
structures, i~ the absence o~:water.-absorbe~t~resln~ ~ r particles7 have limited absorptIon capaclty,.a~d are very ~ulky due to the large amou~t .of materlal neeted.to provide acceptable absorptio~ capacltyO Further, the .
WO91/18~2 PCT~GB91/00780 2 ~ ~i~ 5 ~ 3 2 ahsorbent structures do not retain fluid under pressure.
. A means for improving the absorbency characteristics is to incorporate in the absorbent structures water absorbent resin particles which imbibe fluid to form a swollen hydrogel material, as described for example in US Pate~t 4,610,678. This hydrogel serves to retain the absorbed fluid even under pressure and gives the '' absorbent structure a "dry feel" even when wetted. I~i . .
order to reduce the bulk of absorbent structures ':
containing ~ater absorbent resin particles, large volumes of the absorbent structure material can be replaced with s~all volumes of absorbent resin particles. The absorbent resin particles must ~uickly absorb fluids and 'retain such fluids to pre~ent leakage. ' ' Water absorbent resin particles (als~ referred to as superabsorbent polymers) are primarily used in personal care products to absorb body fluids, ~or example baby diapers, adult incontinence products, feminine hygiene products, a~d the like. ' ' ' ' ' ' ''' .
Water-absorbing resins well known in the art include, for exa'mple',' the hydrolyzate of'a s`tarch~
acrylonitrile' graft'poly~èr as^discloséd in US Patent 25 3,661,815;' the'nèùtralization product of à starch- - `' a'crylonitrile acid `graft polymer 'as discloséd in US ' .
Patent'`4,0i6,663; thë'saponificat-on produc~ o~ `a vi~yl acetate-acrylic ester copolymer as disclosed ln Japa~ese Laid-Op"én Pat'ènt`'PubIi'cation No"." 14689/1977; thé' ' hytroly~a~e of an acrylonitrile copolymer and t~e ' `~
hy'droly'za~te' of an acrylamide copolymer as disclosed ln ~: Japan'ese Patei~'-Publii`ation ~5959/1978, the crosslinke~
' ~ ' products 'of'thes~ hydrolyzates and a self-curable poly(sodium acrylate) obtalned by inverse phase ~ -J j r r, ~ , 7,, ,~r . ~ "t ~
, ' '.
.
',: ' ' . ,,, ' , ,. ' . . -. ~ ' .. ' , ' ' :
WO91/18~2 PCT/GB91/00780 . . ~ .
Z~ 23 - .
suspension polymerization as disclosed in US Pa~ent 4,093,776; and the crosslinked product of partially neutralized polyacrylic acid as disclosed in Japanese Laid-Open Patent Publication 84304/1980.
: 5 The absorbent structures demonstrate limited ability to retain the water-absorbent resin particles . ,- -which are randomly dispersed throughout the structure in the desired locations. This can cause loss of the water-absorbent resin particles during the manufacturing process of such s~ructures~ irritation of the subject durin~ the end use, such as, baby's skin when the structure is used as a disposable diaper. It is - , difficult.to distribute the water-absorbent resin particles evenly~within the absorbent.structure.
Further, the water-absorbent resin particles can ~igrate within the structure9 causing a loss in absorbent p'roperties of the.entire struc~ure. Such water-absorbent resin particles can.a~glomerate.or be too close.to one :' another.c:.Water-absorbent. resiniparticles;in the prese~ce . of -aqueous~.fluids form gels.,If,the gel~parti`cl LS of. ;
.: resi'~s:.,particles are too' close:'toione.another gel~
blockage can occur`-and:the-ability.-of.-the:closely~
,, 25 associated.water-absorbent.:resin particle's~to.~ully :--' , .'. , ' : . absorb iqueous~fluids:is.~s-ignificantly,~reduced~;In,:order ,, , ' to maintain'~.a~minimum'.~absorpt;on~capaci'tyj!more w'ater.
.; absorbent~.. rasin~:parti'cles'~may~`be'rused'.. ;t'han.would:.be' 30 . ~ecessary;in'the:absence'o~^the.rrisk~o~;improper~
dist`ribution':andl:'gel~bl'o'ckàge.J.,Further.,:in~:the~
i pr'epara~ion~oflwater'-abscrbent`'~:s'`t'ru'ctures,'.~handling and ~ cutti~g~'ca~rcause~los~s~ o~ 'ater-ab~orbe~t~:resin~
'' .: par~i'c`l~s ~romJthe~st:ructu'r~e';~re'suIti~glin-~aste,L~a~d~
coùld ~`'presentL~industrial~chygiëne.~.problems.~ . C.3~L~r;.
, .
, .
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WO9~/18~ PCT/GB91/OQ780 i' ``.- 4 ....
Water-absorbent structures function to re~ove aqueous fluids from a source and retain such aqueous fluids. The structures contain hydrophilic fibers which are designed to absorb and ~ransport the aqueous fluid quickly to the interior structure by capillary and wicking means. Such fibers transport the fluid to the water absorbent resin particles wh ch absorb and reeain the aqueous fluids. One problem associated with such -:
water-absorbent structures is the speed of absorption of fluids from ~he exterior of the structure by the fibers. ' EP 90,311,527.7 and GB-A-2237205 disclose a ~ethod of increasing the rate of aqueous fluid flow into the absorbent s~ructures, such'as a baby diaper or fe~inine hygiene napkin, by the.addition of a surface active agent to the body side of the membrane of the absorbent structure. The surface active agent has the ef~ect,of reducing thei-surface tension of,the body fluid or aqueous fluid to enhance the speed at which said -aqueous fluid passes through.the~body.side Pf.the ~ .~-:.,.;, , membrane of the absorbent-structure and into ~he fiber, structure. This method ,o~ reducing the sur~ace:tension '' of aqueous.:body,fluids is,extremely effecti,vP in . ~
achiev'ing rapid.flow and distribution~:of-the body fluid throughout.the~absorbent',structure~.~owever,~this reduction.~ofisurface~tensi`on:has~the disadvantage,,of i~pairing'the;ability;.~of~.:the~absorbentJfiber,.structure 'to'hold-and.retain`the~aqueous body fluid., Water~
absorbent!resins,are~ cluded;withi~ the,:structure :to;:-, aid.in.;retaining~,such~;fluids,.~,Afproblem 1l associated.with '' the use of.~water~absorbent;:.r.esin particles.,~is~,,tha,t.,~the~
speed.~,o~-~.absorption,~of..,.the~hydrophilic~fibe,rs in~the~s~ .
structure is fasteri~.than..the.speed~,o~abso~ption.of.~he water-absorbent resin particles. Therefore, there is a . ' ':
-- : . , ... ~
: : . . ~ . . . . .. .
WO91/18042 pcT/Gs9l/oo78o 1~ 5 Z~
~ime differential between absorption of the aqueaus fluid by the hydrophilic fibers and absorption of the fluid by the water-absorbent resin particles. During this time differential, there is a risk that the absorbent structure could lose such aqueous fluid before being absorbed and bound by the water-absorbent resin s truo tures .
What is needed is a water-absorbent reisin particle which can bie effectively distributed within a absorbent structure and a means of effectively retaining the water-absorbent resins at the desired points in the absorbent structure~
In one embodiment the inven~ion provides water-absorbent res~n particles comprising a carboxyl containing water-absorbent resin, wherein the water-absorbent resin particles also co~prise a thermoplasticpolymer with hydrophilic character. Optionally, the particles also comprise a flow control additive. In a~other embodiment the invention comprises a water-absorbent-structure1whichjcomprise a ~oven or non-woven ~5 mass of fibers having bound thereto particles as described above.
In aanother embodiment, the invention provides a process for preparlng water-absorbent resin particles l,~
havi~g adhesive properties which comprises blending ~ater-absorbent resin particles containing carboxyl ~ ,3 ~ r~ ; r'3~ J~ 3 2.,i3'~S.~;'S;~ ?~ r~ / 3 ~oieties ~ith a ~her~oplastlc resl~ having hydrophilic character until the mixture ~o longer flows freely and,~ -~ ,r ~ h,~ r~7 ~ t ! .~ s~ 7 ,; ~
optio~al ~ ? atding ~to the wat~er,-~a~b!sor~bent resln ~ ~ ~ *
. :
' ~
-.
- , , , , : ,...... . .
WO91/l8042 PCT/GB91/00780 ~ ~ ~ ?~ 6 !~` ~
particles and thermoplastic polymer mixture a flow control additive and blending until the mixt~re flows freely.
The flow control additive can comprise an inorganic material which functions to give ehe compos;tion flowability ~ithout tackiness.
Alternatively, the flow control additive can comprise a water-soluble pol~mer which functions to increaise the viscosity of aqueous -fluids and ~hich further ~unctions to restore the flowability of the mixture of water-absorbent resin and thermoplastic polymer. In the embodiment where the flow control additive is the water-soluble hydrophilic polymer, the absorbent resincomposition improves the function of the water-absorbent structures into which they are incorporated as the flow control additive increases the viscosity of aqueous fluids ab'sorbed by the structure'such that the absorbent fluid'cannot easily be release'd by the structure before being bound by'the ~ater-absorb'ent resin particles.
~., , .... .., - . - . . :. . - .. , The adhesivized'wa~er-absorbent resin'particles of the invention can be more effec~ively distributed ' ' within absorbent structures, and facilitate the"
maintenance of such effective distribution. As a sesult the invention allows the preparation of absorbent ; s~ructures wherë gel blockagë is' mini~ized.''Further, the uYe o~ such adheslv~xed ~ater-absorbent resins r~sult in less 10BS o res~ln during manufa'cturing"and handling of the wàter-absorbent' structures and prevent the problems ~ r L~tt ,~ ?.-~ ; 2 ~ r ~ } ; 3 i;-assoc~ated` wlth such loss. The adhesivized~water-~, ~, . .`.'jdX,.~" ~ .t ~ L ~ r1i ~ J~ u ^
; absorbe~t resln par~lcles of the lnventlo~ allow more ~ficient use of such particles in water-absorbent 1 , -.. : ........... ... . : . :, .: '` ': .: ~'' ' : ,, ' .' ;: .
.
WO91/l8042 PCT/GB91/00780 t ~
7 ~8~
structures, and allow the fabricator to use the optimum amount without significant waste. In those embodiments where the flow control additive is a water-soluble hydrophilic polymer, the retention of fluids by the absorbent structure is significantly enhanced.
Adhesivized as used herein refers to resin particles that are modified such that at a later time they can be adhered to a portion of an absorbent stru~~ture~ e.g. to the fibers of an absorbent s~ructure.
The water-absc,rb~nt resins useful in this invention are well-known to those skilled in the art. In particular, water-absorbent polymers useful in this invention are water-absorbent polymers which contain carboxyl moieties. Among preferred carboxyl containing water absorbent polymers are hydrolyzates of starch-acrylo~itrile graft copolymers? partially neutralizedproducts,o~ a starch-acrylic acid graft,copo,ly~ers, saponificatio~ products of vinyl acetate acrylic ester-copolymers, hydrolyzates of acrylo~itrile copolymers, crosslinked products of hydrolyzates of acrylonitrile copolymers, hydrolyza~es ofJacsylamide copolymers, crosslinked,products"ofihydrolyzates of~acrylamide~: :
copolymers,~-~partially~Reutralized;produc~s of polyacrylic ~ acidq ~ and l crosslinked; products of partially~
neutralizedjlpolyacrylic~;acids. ~ - s~
,r~Eispecialily,preferred aire ~alkal i metal ,~c~
~ype polymers obtained~by copolymierizing 100 parts of a~
acrylic^ai~id-tjpe~o;nol~er~com~ sedj,o~f~ o~ 50,mo~1~e ~
percent of acrylic, ac-ld~and 50 to;!99 mole percent of5i~a . : ' ' ''' ~ ~.
WO91/l8042 pcT/Gs9l/oo78o (, .~ .
~ 8 ::-2 ~
alkali metal acrylate and 0 to S parts by weight of a crosslinkable monomer in aqueous solution in a monomer concentration of at least 20 percent by weight. In another preferred embodi~ent the alkali metal acrylate-type polymers are obtained by polymerizing acrylic acid and post neutral.izing the polymer ~i~h an alkali ~etal base.
There is no limitation to the amount of the carboxyl groups of the wa~er-absorbi~g resin.
Preferably, at least 0.01 equivalent of carboxyl groups are present per 100 g of the water-absorbing resin~ In the case of the partially neutralized polyacrylic acid, the proportion of the unneutralized portion is preferably 1 to 50 mole percent. In one preferred embodiment the water-absorbent resins are crosslinked at or ~ear the particle surface by a polyhydroxy compound capable of reacting with the carboxyL moieties of the water-absorbent resin and ~ay optionally have coated on .
or bound to ~he surface a non-ionic surfactant with an ~LB from 3 to 10.
.
, . . .. . . . ... , .
.The:polyhydroxy compound which is used asja surface~crosslinki~g agent~is a;compollnd which contains-at least ~wo~hydroxyl groups.~hich.arercapable or .. ...~-readily,reacting with the:carboxyl groups.of.:the water-absorbent ~esin, a~d which is~.capable o~.,being dispersed~
over the surface of a water-absorbe~t resin p~rticle.
Preferably, the polyhydroxy compound used in this invé ~ on comp`~ises~~ethyle~e.iglyc`ol,-'diethylene glycol, ylene giycol~ polyethy~lrè-neV~`gly`co`
polyglycrlrol~ propyléne gI~yco'iJ dipropyle~e giycol~
tripropylë~è giy`col~ po ~propyie~e glycoi!s , ' ` ` ` ';
' .:
' - - . . - - . , . - , , , , . -... . ` ,, ... :.: , ~ ` . : .
g ~ ; ,s~ Ç~%~
.; ~ ; .
diethanolamine, triethanolamine~ propane diol, butanediol, hydroxy terminated oxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, trimethylolpropane, pentaerythritol, sorbitol, mannitol, sugars, sugar derivatives or the like. More preferred polyhydroxy compounds include diethylene glycol, triethylene glycol, glycerol, propylene glycol, trimethylol propane, ~.
pentaerythritol or sorbitol. Even more preferred are ~0 sorbitol or glycerol.
:.
The surfactants which may be coated on the surface of, or bound to the surface of the water-lS absorbent resin particles are nonionic:surfactantshaving an HLB in the range of 3 to lO and which are : dispersible in water. Preferable sur~actants co~prise .
sorbitan fatty acid esters, polyoxyethylene sorbitan :fatty acid esters? glycerol or polyglycerol fatty acid 20 esters, polyoxy ethylene alkyl ethers~ polyoxyethylene .
alkylphenol ethers, polyoxyethylene acyl esters, sucrose fatty acid esters or modified surace a`ctive polyesters.
.~More preferred sur~actants are polyethoxylated sorbitol 1~lanolin deriva~ives, for example a surfactant available from ICI under the Tradename Gl425. A sufficient amount :: of surfactant is.. used toi~facili~ate a homogeneous distribution.~of thelsurface.crosslinking.~.agent-.on the~
: surface.. lof:~the.gel.iparticlei,~to improve.the processability..of the.~gel.~by reducing .its.stickinessj to .
reduce the tendency.o~.the dried powder to agglomerate:.. ri ~: when exposed to hu~id.air./or water,~and to bind-fine.~
dust of the water-absorbent.. resin. r~ ;s./~ ;
, , .
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'` , ' ' ' ' ' , , ~ ', . ' , .` ' WO9~/l8042 pcT/Gs91/oo78o ' %~5~3 The water-absorben~ resins are adhesivized by contacting and blending with a thermoplastic polymer with hydrophilic character. Thermoplastic as used herein refers to a polymer which softens, flows and becomes tacky at elevated temperatures. For the purposes of this invention, the polymer must soften? begin eo flow and become tacky at a temperature wh;ch does not harm the wa~er-absorbent resins or materials from which .the ~ater-absorbent structures are prepared and which does not cause the proper~ies of the final water-absorbent resin structure to be significantly degraded.
PrPferably~ the polymer begins to soften at a temperature at or above 35C and more preferably at or above 70C. As the absorbent:resin struc~ures could be and often are exposed to temperatures approaching 35C, it is preferable ~hat the thermoplastic polymer be `
relatively stable at temperatures approaching 35C.
Preferably the thermoplastic polymer begins to 1OW and become tacky at temperatures of 170C or less, more preférably 130C or less, and most preferably 80C or léss.` The''material'used`in the absorbent resin structure .. . , . ~ . .. ..
may be deleteriously effected by exposure to ', tempèratures'abové 170C. ' ;
~ydrophilic character:means. herein.that the ;, thermoplastic~polymer.~has a:portion which demonstrates.'. ' , '`
affinity for water.Such afinity for,water can`~be ,~. ..
indicated by:its:ability,to dissolve or disperseiin .
wBter.~ Thermoplastic.~polymers::,which have: both a~ .~ ,:,,.~. '!
' hydrophobic~portion~.and.a hydrophilic~portion may-~be ,.j.
used in this inven~ion~providedi.they have~the w~ o ` ' eppropriate ther~oplastic charact`eristics. Thus ertain . .
8urfactants which have ther~oplastic character may be .. .. .
,! :
WO9l/l8~2 PCT/GB91l00780 . .
, "i , 11 2 ~ ~ ~ 6 used in the invention. Among preferred classes of thermoplastic polymers are the polyvinyl pyrrolidone polymers, copolymers of polyvinyl pyrrolidone and vinyl .acetate, polyethylene oxides, and polyethoxylated surfactants having a hydrocarbon cap. Hydrocarbon cap means herein a hydrophobic hydrocarbon moiety at one end of the polyethylene oxide chain. Such hydrocarbon caps can be aromatic, aliphaticj or have both aromatic and elevatic components. In one preferred embodiment, the hydrocarbon cap is a nonyl-phenoxy moiety. Examples 0?-surfactants which are useful as ~he thermoplas~ic polymer with hydrophilic character include Synperonic NP
35 available from ICI, straight chain fatty alcohol inititated ethrylates.such as Lutensol AO 30 available . 15 from BASF, and ocyl phenoxy ethrylates Triton X-100 available from Rohm & Haas.
Among more preferred thermaplastic polymers useul in the invention are the polyvinylpyrrol;dones, - polyvinylpyrrolidone vinyl acetate copolymers?.and.the polyethylene oxide based materials. Most preferred . ehermoplastic polymers are the polyvinyl pyrrolidones.
Polymers of a wide.`range.of molecular weights-mày be used in the.invention,.provided the-above-mentioned characteristicsmare exhibited by;the polymers.~
. . The optional flow ,control additive.functio~s.. to;
JU maintain the flowabiLity of.the.co~position.o~ thei.,~ l~
inventiotn,-~ T~h,ere;~;ar~e~L~two j~clas;ses `,Ei fflow,,c,ontrol" ~ ti;
additives which can be used. One class comprises..an~
inorganic ma~erial ~hich functions to improve and maintain the flowability of the adhesivized water- ~.
absorbe~t resins particles of the i~vention. Such ,, - .
, .
:: :
~' . .
, , - .
WO91/18~2 PCT/GB91/00780 f~
2 ~i~ 6 ~ ~ 12 materials are well-known to those skilled in the art.
Examples of materials ~hich may be used include zinc oxide, talc, silica powders and the like. The most preferred of this class of flow control additives is zinc oxide. In a second embodiment the flow control additive can be a polymer which dissolves in or is dispersible in aqueous based fluids and increases the viscosity of aqueous fluids in which it is dissolved or dispersed. Such polymers are well-known to those skilled in the art. Among preferred classes of such polymers are polymers derived from carbohydrates, and modified poly~ers derived from carbohydrates. Included are the polysaccharides, modified polysaccharides, xanthum gums, and ~uar gums. Preferred polysaccharides are the oellulosic materials such as alkyl substituted cellulosics, hydroxyalkyl substituted cellul-osics and the like~ examples of such are cellulose, methylcellulose, ethylcellulose, hydroxyethyl cellulose .~.
and hydroxypropyl cellulose. In another preferred embodiment a mixture of guar and Xanthum may be used as tne nyarOpnlLlC polymer. -~' . .:
, . . . , ~ . ... ... . . . . .. . . . . . . . .
~- .. The.inclusion of.the water-.soluble polymers as :
flow control.additives resultsiin absorbent.'resi'n ~
composition.whi~h:.causes aqueous 'fluids;.in:contact-with such eomposition to ha~e an increased viscosity. By increasing the viscosi~y of such aqueous fluids such aqueous~luids are retained for~a significant'period i~ i!'.
the abs~o"rbentlstruc'~'u're wh'ile the water-absorbe~ti!resins ab~orb thë''aqueoùs-fluid;and;b'ind'''them'within'the''''`' '' strUCtUre'.'; ' ~c ~if~ ? ~ C -. D~ J ~ rl~3 ~ `?~
.' . , ' .
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WO91/18042 pcT/Gsfgl/foo78fd f~' 13 2 ~ ~ ~f5~f~' The water-absorbent resin is contacted with a sufficient amount of thermoplastic polymer to adhesivize substantially all of the resin particles. If too much thermoplastic polymer is used, the ability of the water- ' absorbent ~esin to absorb aqueous fluids will be deleteriously effected. Conversely, if an insufficient amount of thermoplastîc pol~mer is-used,'~all of the water-absorbent resin particles will not be adhesivized.
Preferably, at least one part of thermoplastic polymer per hundred parts of water-absorbent resin is used, more preferably at l.east 3 parts by weight of thermoplastic polymer per hundred parts by.weight of water-absorbent resin~ Pre~erably, 20 parts by wfeight or less of thermoplastic polymer per hundred parts of water-15 absor~ent resin is used, more preferably lO parts by .
weight or less and ~ost preferably 8 parts by weight or ' less are used. It is believed that by choice of a polymer which has hydrophilic character, such polymer . when contacted with the water-absorbent resins at ambifent;temperature forms.'a physical bond on the surface of the water-absorbent-:resin particle. As the'`~` '' thermoplastic;polymer~bound.to.-the surface of 'the water-absorbent resin particle blocks-access of aqueous-fluids to the water~.absorbent.resin particle, if too ~uch thermoplastic~polymer.-:is usedj:the ability of':water to ..
come in contact:~ithr~the.water-absorbfent:resin'particle i8 significantly reduced.~ mm~
.
The amount of~flow.control~.additive'which is 'used .,is.dependent.~upo~.the class-.:o'flow-'control~f ~{`I~f'~
addi~t~ive chosen.~In;~hat-~embodiment wh'ere 'th'e''~flowr-'~
contJr;o~additi.ve ~i,s ;an~inorga~ic'..~ ert material';,':~San'~ Si amount.lwhich.results i~ free..flow..'o'f;~thetcompo'si~'io'n'''o'f :, ' '' ' ... . . .. . .. . . . . . . ..... . . . . .... . .
WO9l/18~2 PCT/GB91/00780 ( Z~i~5~3 1 4 the invention is used. The effective lower limit is ~hat minimum amount which results in free flow of the adhesivized water-absorbent resin composition of the invention. The upper limit is based on econ~mics. In a preferred embodi~ent, at least 0.25 parts by weight per hundred parts of water absorbent resin is used~ In a more preferred embodiment at least O.S parts by weight of flow control additive per hundred parts of water-absorbent resiin is used. Preferably, one part by weight 10 or Iess of flow control additive is used per hundred '' parts of water-absorbent resin. In that embodiment where the flow control additive is a water-soluble polymer which increases the viscosity of aqueous fluids into which it is dissolved, a sufficient a~ount is added to allow the adhesivized water-absorbent resins to freely flow. If too little of such flow control additive is ' used, the adhesivized water-absorbent resins will not flow freely. If too much is used, the functioning of the water-absorbent resin structure ~ay be deleteriously effected. In this embodiment, preferably, one or more parts by weight of such'flow control additive per' hundred parts,of resin is used, more preferably 5 parts by wei'gh~ and most preferably..at least:10 parts by weight. Preferably 20 parts by ~eight per hundred parts of water-absorbent:resin.-are u~ed, more:preferably'l5 ' parts by weight,or-less;are;used, and'most'preferably 12 parts by weight or less are used. .
. The,iadhesivized water-absorbent'resin ':;
compositions .of,,~this`~invention may be .prèparè'd`'by'the ''!' ~ollowi~g.process,.,..The:.~ate'r-absorbe~'t 're i~n'~`par'~iclés L ~ `
ar'e co~tacted wi,t,h,:a~suffic'ie~tA~amount o~-:thèrm`oplasitic`-' poly~er ~wlth a ,hydrophilic charac`ter tn`d~blended under ~
, ~ .
WO91/18042 PCT/GB9t/00780 ~..~ .
'' ' 2 ~ ~ 5 condi~ions such that the resin particles become adhesivized. More particularly, the thermoplastic ;, polymer and water-absorbent resin particles are blended by standard means at ambient temperature until the composition is ~ell mixed. Evidence that the composition is well-mixed is indicated by the material beco~ing fluffy and demonstrating poor flow characteristics. ~ , Temperatures other than ambient may be used as long as it does it deletereously effect the properties of the adhesivized resins. The time period for such blending depends on the scale at which the blending occurs the type of mixer used and whether a batch or continuous process is used', and can be empirically deter~ined as described before. In a continous process at least 2 to
:~ This invention relates to novel water-absorbent resin particles, a process or the preparation of such ~ :
water-absorbe~t resin particles and to absorbent ::
. . .
; 5 structures contai~ing the water-absorbe~t resin ' particles. The invention further relates to water-;~ absorbent resin compositions with improved aqueous fluid absorption properties, and ~ater-absorbent structures co~taining these water-absorbent resin compositions.
. , , ., . .;
It is kno~n to form woven and non-woven structures `of celluloisic f;bers5 ~iatural cotton fibers, sy~thetic fibers or mixt~res thereof for use in .
~absorbing aqueous fluids.-I~ one example, the fibers are formed into op~n-structured absorbe~ webs~ and i~ .
~ Y~ r ~ J ~ ; L; , " ~
another, the ~ibers are thermally bonded to.form co~pLex s~ructures. The flbers used 1~ such structures ca~ , quickly absorb aqueous 1uids and distribute them over the whole absorbent structure by capillary forces~ The .
structures, i~ the absence o~:water.-absorbe~t~resln~ ~ r particles7 have limited absorptIon capaclty,.a~d are very ~ulky due to the large amou~t .of materlal neeted.to provide acceptable absorptio~ capacltyO Further, the .
WO91/18~2 PCT~GB91/00780 2 ~ ~i~ 5 ~ 3 2 ahsorbent structures do not retain fluid under pressure.
. A means for improving the absorbency characteristics is to incorporate in the absorbent structures water absorbent resin particles which imbibe fluid to form a swollen hydrogel material, as described for example in US Pate~t 4,610,678. This hydrogel serves to retain the absorbed fluid even under pressure and gives the '' absorbent structure a "dry feel" even when wetted. I~i . .
order to reduce the bulk of absorbent structures ':
containing ~ater absorbent resin particles, large volumes of the absorbent structure material can be replaced with s~all volumes of absorbent resin particles. The absorbent resin particles must ~uickly absorb fluids and 'retain such fluids to pre~ent leakage. ' ' Water absorbent resin particles (als~ referred to as superabsorbent polymers) are primarily used in personal care products to absorb body fluids, ~or example baby diapers, adult incontinence products, feminine hygiene products, a~d the like. ' ' ' ' ' ' ''' .
Water-absorbing resins well known in the art include, for exa'mple',' the hydrolyzate of'a s`tarch~
acrylonitrile' graft'poly~èr as^discloséd in US Patent 25 3,661,815;' the'nèùtralization product of à starch- - `' a'crylonitrile acid `graft polymer 'as discloséd in US ' .
Patent'`4,0i6,663; thë'saponificat-on produc~ o~ `a vi~yl acetate-acrylic ester copolymer as disclosed ln Japa~ese Laid-Op"én Pat'ènt`'PubIi'cation No"." 14689/1977; thé' ' hytroly~a~e of an acrylonitrile copolymer and t~e ' `~
hy'droly'za~te' of an acrylamide copolymer as disclosed ln ~: Japan'ese Patei~'-Publii`ation ~5959/1978, the crosslinke~
' ~ ' products 'of'thes~ hydrolyzates and a self-curable poly(sodium acrylate) obtalned by inverse phase ~ -J j r r, ~ , 7,, ,~r . ~ "t ~
, ' '.
.
',: ' ' . ,,, ' , ,. ' . . -. ~ ' .. ' , ' ' :
WO91/18~2 PCT/GB91/00780 . . ~ .
Z~ 23 - .
suspension polymerization as disclosed in US Pa~ent 4,093,776; and the crosslinked product of partially neutralized polyacrylic acid as disclosed in Japanese Laid-Open Patent Publication 84304/1980.
: 5 The absorbent structures demonstrate limited ability to retain the water-absorbent resin particles . ,- -which are randomly dispersed throughout the structure in the desired locations. This can cause loss of the water-absorbent resin particles during the manufacturing process of such s~ructures~ irritation of the subject durin~ the end use, such as, baby's skin when the structure is used as a disposable diaper. It is - , difficult.to distribute the water-absorbent resin particles evenly~within the absorbent.structure.
Further, the water-absorbent resin particles can ~igrate within the structure9 causing a loss in absorbent p'roperties of the.entire struc~ure. Such water-absorbent resin particles can.a~glomerate.or be too close.to one :' another.c:.Water-absorbent. resiniparticles;in the prese~ce . of -aqueous~.fluids form gels.,If,the gel~parti`cl LS of. ;
.: resi'~s:.,particles are too' close:'toione.another gel~
blockage can occur`-and:the-ability.-of.-the:closely~
,, 25 associated.water-absorbent.:resin particle's~to.~ully :--' , .'. , ' : . absorb iqueous~fluids:is.~s-ignificantly,~reduced~;In,:order ,, , ' to maintain'~.a~minimum'.~absorpt;on~capaci'tyj!more w'ater.
.; absorbent~.. rasin~:parti'cles'~may~`be'rused'.. ;t'han.would:.be' 30 . ~ecessary;in'the:absence'o~^the.rrisk~o~;improper~
dist`ribution':andl:'gel~bl'o'ckàge.J.,Further.,:in~:the~
i pr'epara~ion~oflwater'-abscrbent`'~:s'`t'ru'ctures,'.~handling and ~ cutti~g~'ca~rcause~los~s~ o~ 'ater-ab~orbe~t~:resin~
'' .: par~i'c`l~s ~romJthe~st:ructu'r~e';~re'suIti~glin-~aste,L~a~d~
coùld ~`'presentL~industrial~chygiëne.~.problems.~ . C.3~L~r;.
, .
, .
' ~
.,,, :,, , , ,, , ... . ,.. .. . . .. . . .. '... ".
WO9~/18~ PCT/GB91/OQ780 i' ``.- 4 ....
Water-absorbent structures function to re~ove aqueous fluids from a source and retain such aqueous fluids. The structures contain hydrophilic fibers which are designed to absorb and ~ransport the aqueous fluid quickly to the interior structure by capillary and wicking means. Such fibers transport the fluid to the water absorbent resin particles wh ch absorb and reeain the aqueous fluids. One problem associated with such -:
water-absorbent structures is the speed of absorption of fluids from ~he exterior of the structure by the fibers. ' EP 90,311,527.7 and GB-A-2237205 disclose a ~ethod of increasing the rate of aqueous fluid flow into the absorbent s~ructures, such'as a baby diaper or fe~inine hygiene napkin, by the.addition of a surface active agent to the body side of the membrane of the absorbent structure. The surface active agent has the ef~ect,of reducing thei-surface tension of,the body fluid or aqueous fluid to enhance the speed at which said -aqueous fluid passes through.the~body.side Pf.the ~ .~-:.,.;, , membrane of the absorbent-structure and into ~he fiber, structure. This method ,o~ reducing the sur~ace:tension '' of aqueous.:body,fluids is,extremely effecti,vP in . ~
achiev'ing rapid.flow and distribution~:of-the body fluid throughout.the~absorbent',structure~.~owever,~this reduction.~ofisurface~tensi`on:has~the disadvantage,,of i~pairing'the;ability;.~of~.:the~absorbentJfiber,.structure 'to'hold-and.retain`the~aqueous body fluid., Water~
absorbent!resins,are~ cluded;withi~ the,:structure :to;:-, aid.in.;retaining~,such~;fluids,.~,Afproblem 1l associated.with '' the use of.~water~absorbent;:.r.esin particles.,~is~,,tha,t.,~the~
speed.~,o~-~.absorption,~of..,.the~hydrophilic~fibe,rs in~the~s~ .
structure is fasteri~.than..the.speed~,o~abso~ption.of.~he water-absorbent resin particles. Therefore, there is a . ' ':
-- : . , ... ~
: : . . ~ . . . . .. .
WO91/18042 pcT/Gs9l/oo78o 1~ 5 Z~
~ime differential between absorption of the aqueaus fluid by the hydrophilic fibers and absorption of the fluid by the water-absorbent resin particles. During this time differential, there is a risk that the absorbent structure could lose such aqueous fluid before being absorbed and bound by the water-absorbent resin s truo tures .
What is needed is a water-absorbent reisin particle which can bie effectively distributed within a absorbent structure and a means of effectively retaining the water-absorbent resins at the desired points in the absorbent structure~
In one embodiment the inven~ion provides water-absorbent res~n particles comprising a carboxyl containing water-absorbent resin, wherein the water-absorbent resin particles also co~prise a thermoplasticpolymer with hydrophilic character. Optionally, the particles also comprise a flow control additive. In a~other embodiment the invention comprises a water-absorbent-structure1whichjcomprise a ~oven or non-woven ~5 mass of fibers having bound thereto particles as described above.
In aanother embodiment, the invention provides a process for preparlng water-absorbent resin particles l,~
havi~g adhesive properties which comprises blending ~ater-absorbent resin particles containing carboxyl ~ ,3 ~ r~ ; r'3~ J~ 3 2.,i3'~S.~;'S;~ ?~ r~ / 3 ~oieties ~ith a ~her~oplastlc resl~ having hydrophilic character until the mixture ~o longer flows freely and,~ -~ ,r ~ h,~ r~7 ~ t ! .~ s~ 7 ,; ~
optio~al ~ ? atding ~to the wat~er,-~a~b!sor~bent resln ~ ~ ~ *
. :
' ~
-.
- , , , , : ,...... . .
WO91/l8042 PCT/GB91/00780 ~ ~ ~ ?~ 6 !~` ~
particles and thermoplastic polymer mixture a flow control additive and blending until the mixt~re flows freely.
The flow control additive can comprise an inorganic material which functions to give ehe compos;tion flowability ~ithout tackiness.
Alternatively, the flow control additive can comprise a water-soluble pol~mer which functions to increaise the viscosity of aqueous -fluids and ~hich further ~unctions to restore the flowability of the mixture of water-absorbent resin and thermoplastic polymer. In the embodiment where the flow control additive is the water-soluble hydrophilic polymer, the absorbent resincomposition improves the function of the water-absorbent structures into which they are incorporated as the flow control additive increases the viscosity of aqueous fluids ab'sorbed by the structure'such that the absorbent fluid'cannot easily be release'd by the structure before being bound by'the ~ater-absorb'ent resin particles.
~., , .... .., - . - . . :. . - .. , The adhesivized'wa~er-absorbent resin'particles of the invention can be more effec~ively distributed ' ' within absorbent structures, and facilitate the"
maintenance of such effective distribution. As a sesult the invention allows the preparation of absorbent ; s~ructures wherë gel blockagë is' mini~ized.''Further, the uYe o~ such adheslv~xed ~ater-absorbent resins r~sult in less 10BS o res~ln during manufa'cturing"and handling of the wàter-absorbent' structures and prevent the problems ~ r L~tt ,~ ?.-~ ; 2 ~ r ~ } ; 3 i;-assoc~ated` wlth such loss. The adhesivized~water-~, ~, . .`.'jdX,.~" ~ .t ~ L ~ r1i ~ J~ u ^
; absorbe~t resln par~lcles of the lnventlo~ allow more ~ficient use of such particles in water-absorbent 1 , -.. : ........... ... . : . :, .: '` ': .: ~'' ' : ,, ' .' ;: .
.
WO91/l8042 PCT/GB91/00780 t ~
7 ~8~
structures, and allow the fabricator to use the optimum amount without significant waste. In those embodiments where the flow control additive is a water-soluble hydrophilic polymer, the retention of fluids by the absorbent structure is significantly enhanced.
Adhesivized as used herein refers to resin particles that are modified such that at a later time they can be adhered to a portion of an absorbent stru~~ture~ e.g. to the fibers of an absorbent s~ructure.
The water-absc,rb~nt resins useful in this invention are well-known to those skilled in the art. In particular, water-absorbent polymers useful in this invention are water-absorbent polymers which contain carboxyl moieties. Among preferred carboxyl containing water absorbent polymers are hydrolyzates of starch-acrylo~itrile graft copolymers? partially neutralizedproducts,o~ a starch-acrylic acid graft,copo,ly~ers, saponificatio~ products of vinyl acetate acrylic ester-copolymers, hydrolyzates of acrylo~itrile copolymers, crosslinked products of hydrolyzates of acrylonitrile copolymers, hydrolyza~es ofJacsylamide copolymers, crosslinked,products"ofihydrolyzates of~acrylamide~: :
copolymers,~-~partially~Reutralized;produc~s of polyacrylic ~ acidq ~ and l crosslinked; products of partially~
neutralizedjlpolyacrylic~;acids. ~ - s~
,r~Eispecialily,preferred aire ~alkal i metal ,~c~
~ype polymers obtained~by copolymierizing 100 parts of a~
acrylic^ai~id-tjpe~o;nol~er~com~ sedj,o~f~ o~ 50,mo~1~e ~
percent of acrylic, ac-ld~and 50 to;!99 mole percent of5i~a . : ' ' ''' ~ ~.
WO91/l8042 pcT/Gs9l/oo78o (, .~ .
~ 8 ::-2 ~
alkali metal acrylate and 0 to S parts by weight of a crosslinkable monomer in aqueous solution in a monomer concentration of at least 20 percent by weight. In another preferred embodi~ent the alkali metal acrylate-type polymers are obtained by polymerizing acrylic acid and post neutral.izing the polymer ~i~h an alkali ~etal base.
There is no limitation to the amount of the carboxyl groups of the wa~er-absorbi~g resin.
Preferably, at least 0.01 equivalent of carboxyl groups are present per 100 g of the water-absorbing resin~ In the case of the partially neutralized polyacrylic acid, the proportion of the unneutralized portion is preferably 1 to 50 mole percent. In one preferred embodiment the water-absorbent resins are crosslinked at or ~ear the particle surface by a polyhydroxy compound capable of reacting with the carboxyL moieties of the water-absorbent resin and ~ay optionally have coated on .
or bound to ~he surface a non-ionic surfactant with an ~LB from 3 to 10.
.
, . . .. . . . ... , .
.The:polyhydroxy compound which is used asja surface~crosslinki~g agent~is a;compollnd which contains-at least ~wo~hydroxyl groups.~hich.arercapable or .. ...~-readily,reacting with the:carboxyl groups.of.:the water-absorbent ~esin, a~d which is~.capable o~.,being dispersed~
over the surface of a water-absorbe~t resin p~rticle.
Preferably, the polyhydroxy compound used in this invé ~ on comp`~ises~~ethyle~e.iglyc`ol,-'diethylene glycol, ylene giycol~ polyethy~lrè-neV~`gly`co`
polyglycrlrol~ propyléne gI~yco'iJ dipropyle~e giycol~
tripropylë~è giy`col~ po ~propyie~e glycoi!s , ' ` ` ` ';
' .:
' - - . . - - . , . - , , , , . -... . ` ,, ... :.: , ~ ` . : .
g ~ ; ,s~ Ç~%~
.; ~ ; .
diethanolamine, triethanolamine~ propane diol, butanediol, hydroxy terminated oxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, trimethylolpropane, pentaerythritol, sorbitol, mannitol, sugars, sugar derivatives or the like. More preferred polyhydroxy compounds include diethylene glycol, triethylene glycol, glycerol, propylene glycol, trimethylol propane, ~.
pentaerythritol or sorbitol. Even more preferred are ~0 sorbitol or glycerol.
:.
The surfactants which may be coated on the surface of, or bound to the surface of the water-lS absorbent resin particles are nonionic:surfactantshaving an HLB in the range of 3 to lO and which are : dispersible in water. Preferable sur~actants co~prise .
sorbitan fatty acid esters, polyoxyethylene sorbitan :fatty acid esters? glycerol or polyglycerol fatty acid 20 esters, polyoxy ethylene alkyl ethers~ polyoxyethylene .
alkylphenol ethers, polyoxyethylene acyl esters, sucrose fatty acid esters or modified surace a`ctive polyesters.
.~More preferred sur~actants are polyethoxylated sorbitol 1~lanolin deriva~ives, for example a surfactant available from ICI under the Tradename Gl425. A sufficient amount :: of surfactant is.. used toi~facili~ate a homogeneous distribution.~of thelsurface.crosslinking.~.agent-.on the~
: surface.. lof:~the.gel.iparticlei,~to improve.the processability..of the.~gel.~by reducing .its.stickinessj to .
reduce the tendency.o~.the dried powder to agglomerate:.. ri ~: when exposed to hu~id.air./or water,~and to bind-fine.~
dust of the water-absorbent.. resin. r~ ;s./~ ;
, , .
`
' 1.:'.
'' I ' ~ . . . -- - - , .
'` , ' ' ' ' ' , , ~ ', . ' , .` ' WO9~/l8042 pcT/Gs91/oo78o ' %~5~3 The water-absorben~ resins are adhesivized by contacting and blending with a thermoplastic polymer with hydrophilic character. Thermoplastic as used herein refers to a polymer which softens, flows and becomes tacky at elevated temperatures. For the purposes of this invention, the polymer must soften? begin eo flow and become tacky at a temperature wh;ch does not harm the wa~er-absorbent resins or materials from which .the ~ater-absorbent structures are prepared and which does not cause the proper~ies of the final water-absorbent resin structure to be significantly degraded.
PrPferably~ the polymer begins to soften at a temperature at or above 35C and more preferably at or above 70C. As the absorbent:resin struc~ures could be and often are exposed to temperatures approaching 35C, it is preferable ~hat the thermoplastic polymer be `
relatively stable at temperatures approaching 35C.
Preferably the thermoplastic polymer begins to 1OW and become tacky at temperatures of 170C or less, more preférably 130C or less, and most preferably 80C or léss.` The''material'used`in the absorbent resin structure .. . , . ~ . .. ..
may be deleteriously effected by exposure to ', tempèratures'abové 170C. ' ;
~ydrophilic character:means. herein.that the ;, thermoplastic~polymer.~has a:portion which demonstrates.'. ' , '`
affinity for water.Such afinity for,water can`~be ,~. ..
indicated by:its:ability,to dissolve or disperseiin .
wBter.~ Thermoplastic.~polymers::,which have: both a~ .~ ,:,,.~. '!
' hydrophobic~portion~.and.a hydrophilic~portion may-~be ,.j.
used in this inven~ion~providedi.they have~the w~ o ` ' eppropriate ther~oplastic charact`eristics. Thus ertain . .
8urfactants which have ther~oplastic character may be .. .. .
,! :
WO9l/l8~2 PCT/GB91l00780 . .
, "i , 11 2 ~ ~ ~ 6 used in the invention. Among preferred classes of thermoplastic polymers are the polyvinyl pyrrolidone polymers, copolymers of polyvinyl pyrrolidone and vinyl .acetate, polyethylene oxides, and polyethoxylated surfactants having a hydrocarbon cap. Hydrocarbon cap means herein a hydrophobic hydrocarbon moiety at one end of the polyethylene oxide chain. Such hydrocarbon caps can be aromatic, aliphaticj or have both aromatic and elevatic components. In one preferred embodiment, the hydrocarbon cap is a nonyl-phenoxy moiety. Examples 0?-surfactants which are useful as ~he thermoplas~ic polymer with hydrophilic character include Synperonic NP
35 available from ICI, straight chain fatty alcohol inititated ethrylates.such as Lutensol AO 30 available . 15 from BASF, and ocyl phenoxy ethrylates Triton X-100 available from Rohm & Haas.
Among more preferred thermaplastic polymers useul in the invention are the polyvinylpyrrol;dones, - polyvinylpyrrolidone vinyl acetate copolymers?.and.the polyethylene oxide based materials. Most preferred . ehermoplastic polymers are the polyvinyl pyrrolidones.
Polymers of a wide.`range.of molecular weights-mày be used in the.invention,.provided the-above-mentioned characteristicsmare exhibited by;the polymers.~
. . The optional flow ,control additive.functio~s.. to;
JU maintain the flowabiLity of.the.co~position.o~ thei.,~ l~
inventiotn,-~ T~h,ere;~;ar~e~L~two j~clas;ses `,Ei fflow,,c,ontrol" ~ ti;
additives which can be used. One class comprises..an~
inorganic ma~erial ~hich functions to improve and maintain the flowability of the adhesivized water- ~.
absorbe~t resins particles of the i~vention. Such ,, - .
, .
:: :
~' . .
, , - .
WO91/18~2 PCT/GB91/00780 f~
2 ~i~ 6 ~ ~ 12 materials are well-known to those skilled in the art.
Examples of materials ~hich may be used include zinc oxide, talc, silica powders and the like. The most preferred of this class of flow control additives is zinc oxide. In a second embodiment the flow control additive can be a polymer which dissolves in or is dispersible in aqueous based fluids and increases the viscosity of aqueous fluids in which it is dissolved or dispersed. Such polymers are well-known to those skilled in the art. Among preferred classes of such polymers are polymers derived from carbohydrates, and modified poly~ers derived from carbohydrates. Included are the polysaccharides, modified polysaccharides, xanthum gums, and ~uar gums. Preferred polysaccharides are the oellulosic materials such as alkyl substituted cellulosics, hydroxyalkyl substituted cellul-osics and the like~ examples of such are cellulose, methylcellulose, ethylcellulose, hydroxyethyl cellulose .~.
and hydroxypropyl cellulose. In another preferred embodiment a mixture of guar and Xanthum may be used as tne nyarOpnlLlC polymer. -~' . .:
, . . . , ~ . ... ... . . . . .. . . . . . . . .
~- .. The.inclusion of.the water-.soluble polymers as :
flow control.additives resultsiin absorbent.'resi'n ~
composition.whi~h:.causes aqueous 'fluids;.in:contact-with such eomposition to ha~e an increased viscosity. By increasing the viscosi~y of such aqueous fluids such aqueous~luids are retained for~a significant'period i~ i!'.
the abs~o"rbentlstruc'~'u're wh'ile the water-absorbe~ti!resins ab~orb thë''aqueoùs-fluid;and;b'ind'''them'within'the''''`' '' strUCtUre'.'; ' ~c ~if~ ? ~ C -. D~ J ~ rl~3 ~ `?~
.' . , ' .
.
WO91/18042 pcT/Gsfgl/foo78fd f~' 13 2 ~ ~ ~f5~f~' The water-absorbent resin is contacted with a sufficient amount of thermoplastic polymer to adhesivize substantially all of the resin particles. If too much thermoplastic polymer is used, the ability of the water- ' absorbent ~esin to absorb aqueous fluids will be deleteriously effected. Conversely, if an insufficient amount of thermoplastîc pol~mer is-used,'~all of the water-absorbent resin particles will not be adhesivized.
Preferably, at least one part of thermoplastic polymer per hundred parts of water-absorbent resin is used, more preferably at l.east 3 parts by weight of thermoplastic polymer per hundred parts by.weight of water-absorbent resin~ Pre~erably, 20 parts by wfeight or less of thermoplastic polymer per hundred parts of water-15 absor~ent resin is used, more preferably lO parts by .
weight or less and ~ost preferably 8 parts by weight or ' less are used. It is believed that by choice of a polymer which has hydrophilic character, such polymer . when contacted with the water-absorbent resins at ambifent;temperature forms.'a physical bond on the surface of the water-absorbent-:resin particle. As the'`~` '' thermoplastic;polymer~bound.to.-the surface of 'the water-absorbent resin particle blocks-access of aqueous-fluids to the water~.absorbent.resin particle, if too ~uch thermoplastic~polymer.-:is usedj:the ability of':water to ..
come in contact:~ithr~the.water-absorbfent:resin'particle i8 significantly reduced.~ mm~
.
The amount of~flow.control~.additive'which is 'used .,is.dependent.~upo~.the class-.:o'flow-'control~f ~{`I~f'~
addi~t~ive chosen.~In;~hat-~embodiment wh'ere 'th'e''~flowr-'~
contJr;o~additi.ve ~i,s ;an~inorga~ic'..~ ert material';,':~San'~ Si amount.lwhich.results i~ free..flow..'o'f;~thetcompo'si~'io'n'''o'f :, ' '' ' ... . . .. . .. . . . . . . ..... . . . . .... . .
WO9l/18~2 PCT/GB91/00780 ( Z~i~5~3 1 4 the invention is used. The effective lower limit is ~hat minimum amount which results in free flow of the adhesivized water-absorbent resin composition of the invention. The upper limit is based on econ~mics. In a preferred embodi~ent, at least 0.25 parts by weight per hundred parts of water absorbent resin is used~ In a more preferred embodiment at least O.S parts by weight of flow control additive per hundred parts of water-absorbent resiin is used. Preferably, one part by weight 10 or Iess of flow control additive is used per hundred '' parts of water-absorbent resin. In that embodiment where the flow control additive is a water-soluble polymer which increases the viscosity of aqueous fluids into which it is dissolved, a sufficient a~ount is added to allow the adhesivized water-absorbent resins to freely flow. If too little of such flow control additive is ' used, the adhesivized water-absorbent resins will not flow freely. If too much is used, the functioning of the water-absorbent resin structure ~ay be deleteriously effected. In this embodiment, preferably, one or more parts by weight of such'flow control additive per' hundred parts,of resin is used, more preferably 5 parts by wei'gh~ and most preferably..at least:10 parts by weight. Preferably 20 parts by ~eight per hundred parts of water-absorbent:resin.-are u~ed, more:preferably'l5 ' parts by weight,or-less;are;used, and'most'preferably 12 parts by weight or less are used. .
. The,iadhesivized water-absorbent'resin ':;
compositions .of,,~this`~invention may be .prèparè'd`'by'the ''!' ~ollowi~g.process,.,..The:.~ate'r-absorbe~'t 're i~n'~`par'~iclés L ~ `
ar'e co~tacted wi,t,h,:a~suffic'ie~tA~amount o~-:thèrm`oplasitic`-' poly~er ~wlth a ,hydrophilic charac`ter tn`d~blended under ~
, ~ .
WO91/18042 PCT/GB9t/00780 ~..~ .
'' ' 2 ~ ~ 5 condi~ions such that the resin particles become adhesivized. More particularly, the thermoplastic ;, polymer and water-absorbent resin particles are blended by standard means at ambient temperature until the composition is ~ell mixed. Evidence that the composition is well-mixed is indicated by the material beco~ing fluffy and demonstrating poor flow characteristics. ~ , Temperatures other than ambient may be used as long as it does it deletereously effect the properties of the adhesivized resins. The time period for such blending depends on the scale at which the blending occurs the type of mixer used and whether a batch or continuous process is used', and can be empirically deter~ined as described before. In a continous process at least 2 to
3 seconds contact time is preferred. In a batch process as little as five seconds contact time may be used and as much as 3 to 4 hours may be used. Once the flow characteristics of the adhesivized resin deteriorate, the flow control additive can optionally be added and blending may continuè. This blending can continue for a suf~icient time~'such`'that thë adhesivized resins fiows freely.-This can take place`,at any temperature which does not deleteriously affect the properties of the adhesivized ~ater-absorbènt rësin, and most conveniently `
takes plàce at`ambiënt temper tures. This blending ,,, continues for a time such that the ~aterial flows i~reely..'The time period for'snch blending depends on the scale at which.the~blending occurs the,type of mixer 30 used and,whether.a batch;or~co,ntinuou,s,process:is used,i '-' and can be empirically~determined as ~described before. .
Itn?Ja ~ continous~;proces~s~ !at ~lea,st~2,jt,o,53-,iseconds,~,contact;
time is~pre~erred. ~,In~aybatch processias~little as~five seconds contact time,may,be^~use,d,~,and~asjimuch,,as~,3ito 4^:~
hours may,be,used. Blending~ca~occur by ~any means ;~hich :
WOgltl8042 PCT/~B91/00780 z~ ?~5~ 16 effectively results in contact of all of the components.
Such mea~s well-known to those skilled in the art, and the choice of such is not critical to the invention.
The adhesivized water-absorbent resins of the inve~tion are primarily used by incorporating them into absorbent structures. Such structures are primarily composed of natural and/or synthetic fibers, the fibers can be formed into woven and non-woven structures. Such structures are well-known'to those skilled in the art.
The water-absorbent resins of this invention can be ~ contacted with finished structures or mixed 1n with the ; component parts prior to ~ormation of the structure~ In general, the adhesivized abs~rbent resins of the invention are incorporatèd into the absorbent structure and 'the absorbent structure is exposed to temperatures at which the thermoplastic polym,er softens and becomes tacky.'Under such conditions, the adhesivized water-absorbent resin particles are then bound to fibers ofthe ~absorbent'stru'ctu'rë. The thermal bonding technique resùlts in'fixating the'water-absorbent resin particlés in the`'absorbent st'ructure. This prevents loss of ., " , . , ,, , .~ .. .... . . . . .. .. .
absorbent resin particl~es during hand1ing and prevents migration and agglomeration of water-absorbent resin partlcles .
'In one~embodiment absorben't' resin'structûres ' ~
a~e~preparediby'~what`i~;'kD,own"'in"'t~è'art:às~a'l'lofting' i process~ In~such''proces'5'"a'mixtùre'0~'fibers'~is;là;d 1`' ', ~ dowrl,~san,d!the~fibèrsiare'~hëàtèd to"èpàrîd't~e;;strùcturè.
In'such procéss``the''f;bers':~càn'either bè'~prët~eated w'ith the adhesivizedf'water~àbSorbent re'sini~or f~ithe temperature of~the lofti~g';process`~is high~e~ough~ thë^-', WO 91tl8042 P~/GB91/00780 : `
adhesive structures can be bound to ehe fibers during the lofting step, provided the lofting temperature is sufficient to cause the thermoplastic polymer to soften and become tacky. In a~other embodiment~ absorbent structures are prepared via a thermal bonding process.
In such process, a mixture of hydrophilie fibers and hydrophobic thermoplastic fibers are mixed and water-absorbent resin par~icles are contacted ~ith such mixture. Thereafter the mixture of fibers and water-absorbent resin particle is exposed to temperatures atwhioh the thermoplastic polymer with hydrophilic character a~d the thermoplastic fibers of the struc~ure begin to flow and beeome tacky such that the mass of fibers and resin become bound together upon cooling.
Synthetic fibers such as polyes~er, and polyolefin and natural or regenerated cellulosic fibers are preferably used. Preferably, the structure comprises a mixture o hydrophilic fibers, such as cellulosic and regenerated cellulose based fibers, with hydrophobic polyolefin and polyester fibers. Preferably such mixture contains 20 percent or greater cellulosic fibers.
' The particle size of the water-absorbent resin is not critical with respect to this invention. Particle sizes useful are those commonly known as useful in absorbent structures. In a preferred embodiment the particle size is less than about 2 millimeters, more pre~erably 0.8 millimeters or less. Preferably the particles have a size of 0.2 millimeters or greater, and more preferably 0.5 millimeters or greater.
In one embodiment of the inve~tion~ water-absorbent resin particles of the invention csn be .
'' ~
..
WO91/18~2 PCT/GB91/00780 blended with the flow control additive which is a hydrophilic polymer soluble in water in the absence of the thermoplastic polymer. Such a composition can be used in those uses in which the adhesive is not required in the final structure. These CompOsitiQns provide a means for improving the retention of aqueous fluids in an absorbent structure by holding the fluids in t~e structure while the absorbent resins are absorbing the liquid.
. , . ... . , , ~ . . .. ..
: ~ ' ' ' ' , :' , '', :
''.
", ., ' ' ' ~'. ' . ': ' ' ' :
WOgl/18~2 pcT/Gs91/oo78o 7................................................ ' ,, ~ , :~ ' 1 9 z~ s~3 .
Several ther~soplastic poly~sers are contacted with water-absorbent resin particles and subjected to : the following tests. ....
.
Coatin~ Affinity Test Into a 500 ml glass jar are weighed 100 g of a water-.
- absorbent resin particle. To this is added a portion of thermoplastic polymer. A top is placed on the jar and it is shaken or ~bout 10 seconds. The physical condition : of the mixture is noted aftër shaking. This is repeated for each thermoplastic polymer at levels of 5, 10, 15 - and 20 g.
-.
Polymer Bondin~
Mixtures of water-absorbent resin and : 20 thermoplastic polymer (5, 10, 15 and 20 parts of :
thermoplastic polymer per 100 parts of resin)?are ..-..
prepared by blending. The mixtures are separately sandwiched betwee~ two pieces ~of filter paper and hea~ed : ~o~ a ceramic hot platé. Evidënce of thërmal âdhesion is noted`at ~arlous temperatures.
i; ..The water-absorben~resin particlesiàrè basèd `
on~polyacrylic;a~id cros'sii~ed'with~rtrimlethylol propane 30 sandspartially.~neu~ràlized wiæh~isodium'jhydroxidë'to!à
level.~ofi~68 pèrcent~neutralization'. The~ ther~soplastic 3i polymers are polyvinylide~e~pyrroiidd~ë~of~thrëë
molecular weights (8000~ 38~000 and 630~000); ~wo polyethylene oxite based polymers (MW lOO,OOO and : -- : .
600~0003 and a low molecular weight polyvinyl alcohol, :. .
,0 - . . . . .
.
'1 , ~ : .
~: , ... . . , . . .. . . . . ~ ... - .
WO91/18~2 PCT/GB91~00780 ~ ~. 20 ".~
available fro~ Air Products under the trade name Airvol 205.
Results Coatin~ Affinity Test Good coating affinil:y is demonstrated by the polymer adhering to the water absorbent resin thermoplastic particles. Poor coating afflnity is demonstrated by the presence of the thermoplastic polymer as a slowly settling dust once shaking is discontinued. The polyvinyl pyrrolidone demonstrated excellent coating affinity at all molecular weights. The polyethylene oxide polymers demonstrate limited affi~ity for the water absorbent resin by the presence of dust at 10, 15 and 20 parts of thermoplastic polymer per hundred parts of resin. The polyvinyl alcohol exhibits excellent powder coating affinicy, as only a slight amount of free dust is detected at 20 parts of polyvinyl alcohol.
Results Bondin:~ Testi;
, .. ... . . . . ............... .
The watèr absorbént resin blendéd with polyethyie~e oxide at 5 parts demonstrate good adhesio~.
Water absorbeit resin particles coated wlth polyvinyl pyrrolido~es of all ~hree molecular ~eights demonstrate good bonding characteristics at 75~C~ The polyvinyl alcohoa coated water-absorbent~resins-demonstrate a ~sl,i~ht adhesive character~at 100,C.~ The;results:of~both tests are.~jom~iled.r~in,Table~ L refers:.to low~molecular ~.
~eight,4Mire~ers t~o medlum molecular,weight, and ~ ~ :
refers to~highùmolecularlweight. ..;~ Lt~
,, ~: ' : . ' ', . : :: ' . . , : :,. : ' ' ' ,, - ~, Wo 91/~8042 pcr/GBs1/oo78o Tabl e E~am Polymer ~ ~rer Bond ng Coating Affinity ~ . . _ ._ . 1 Polyvinyl Good (75C) ExcellenVall levels pyrrolidone L
. ., _ _ 2 Polyvinyl Good (75C~ Excellent/all levels pyrroltdone M
. ~
3 Polyvinyl Good (75C) ExcellenVall levels p~l~one H _
takes plàce at`ambiënt temper tures. This blending ,,, continues for a time such that the ~aterial flows i~reely..'The time period for'snch blending depends on the scale at which.the~blending occurs the,type of mixer 30 used and,whether.a batch;or~co,ntinuou,s,process:is used,i '-' and can be empirically~determined as ~described before. .
Itn?Ja ~ continous~;proces~s~ !at ~lea,st~2,jt,o,53-,iseconds,~,contact;
time is~pre~erred. ~,In~aybatch processias~little as~five seconds contact time,may,be^~use,d,~,and~asjimuch,,as~,3ito 4^:~
hours may,be,used. Blending~ca~occur by ~any means ;~hich :
WOgltl8042 PCT/~B91/00780 z~ ?~5~ 16 effectively results in contact of all of the components.
Such mea~s well-known to those skilled in the art, and the choice of such is not critical to the invention.
The adhesivized water-absorbent resins of the inve~tion are primarily used by incorporating them into absorbent structures. Such structures are primarily composed of natural and/or synthetic fibers, the fibers can be formed into woven and non-woven structures. Such structures are well-known'to those skilled in the art.
The water-absorbent resins of this invention can be ~ contacted with finished structures or mixed 1n with the ; component parts prior to ~ormation of the structure~ In general, the adhesivized abs~rbent resins of the invention are incorporatèd into the absorbent structure and 'the absorbent structure is exposed to temperatures at which the thermoplastic polym,er softens and becomes tacky.'Under such conditions, the adhesivized water-absorbent resin particles are then bound to fibers ofthe ~absorbent'stru'ctu'rë. The thermal bonding technique resùlts in'fixating the'water-absorbent resin particlés in the`'absorbent st'ructure. This prevents loss of ., " , . , ,, , .~ .. .... . . . . .. .. .
absorbent resin particl~es during hand1ing and prevents migration and agglomeration of water-absorbent resin partlcles .
'In one~embodiment absorben't' resin'structûres ' ~
a~e~preparediby'~what`i~;'kD,own"'in"'t~è'art:às~a'l'lofting' i process~ In~such''proces'5'"a'mixtùre'0~'fibers'~is;là;d 1`' ', ~ dowrl,~san,d!the~fibèrsiare'~hëàtèd to"èpàrîd't~e;;strùcturè.
In'such procéss``the''f;bers':~càn'either bè'~prët~eated w'ith the adhesivizedf'water~àbSorbent re'sini~or f~ithe temperature of~the lofti~g';process`~is high~e~ough~ thë^-', WO 91tl8042 P~/GB91/00780 : `
adhesive structures can be bound to ehe fibers during the lofting step, provided the lofting temperature is sufficient to cause the thermoplastic polymer to soften and become tacky. In a~other embodiment~ absorbent structures are prepared via a thermal bonding process.
In such process, a mixture of hydrophilie fibers and hydrophobic thermoplastic fibers are mixed and water-absorbent resin par~icles are contacted ~ith such mixture. Thereafter the mixture of fibers and water-absorbent resin particle is exposed to temperatures atwhioh the thermoplastic polymer with hydrophilic character a~d the thermoplastic fibers of the struc~ure begin to flow and beeome tacky such that the mass of fibers and resin become bound together upon cooling.
Synthetic fibers such as polyes~er, and polyolefin and natural or regenerated cellulosic fibers are preferably used. Preferably, the structure comprises a mixture o hydrophilic fibers, such as cellulosic and regenerated cellulose based fibers, with hydrophobic polyolefin and polyester fibers. Preferably such mixture contains 20 percent or greater cellulosic fibers.
' The particle size of the water-absorbent resin is not critical with respect to this invention. Particle sizes useful are those commonly known as useful in absorbent structures. In a preferred embodiment the particle size is less than about 2 millimeters, more pre~erably 0.8 millimeters or less. Preferably the particles have a size of 0.2 millimeters or greater, and more preferably 0.5 millimeters or greater.
In one embodiment of the inve~tion~ water-absorbent resin particles of the invention csn be .
'' ~
..
WO91/18~2 PCT/GB91/00780 blended with the flow control additive which is a hydrophilic polymer soluble in water in the absence of the thermoplastic polymer. Such a composition can be used in those uses in which the adhesive is not required in the final structure. These CompOsitiQns provide a means for improving the retention of aqueous fluids in an absorbent structure by holding the fluids in t~e structure while the absorbent resins are absorbing the liquid.
. , . ... . , , ~ . . .. ..
: ~ ' ' ' ' , :' , '', :
''.
", ., ' ' ' ~'. ' . ': ' ' ' :
WOgl/18~2 pcT/Gs91/oo78o 7................................................ ' ,, ~ , :~ ' 1 9 z~ s~3 .
Several ther~soplastic poly~sers are contacted with water-absorbent resin particles and subjected to : the following tests. ....
.
Coatin~ Affinity Test Into a 500 ml glass jar are weighed 100 g of a water-.
- absorbent resin particle. To this is added a portion of thermoplastic polymer. A top is placed on the jar and it is shaken or ~bout 10 seconds. The physical condition : of the mixture is noted aftër shaking. This is repeated for each thermoplastic polymer at levels of 5, 10, 15 - and 20 g.
-.
Polymer Bondin~
Mixtures of water-absorbent resin and : 20 thermoplastic polymer (5, 10, 15 and 20 parts of :
thermoplastic polymer per 100 parts of resin)?are ..-..
prepared by blending. The mixtures are separately sandwiched betwee~ two pieces ~of filter paper and hea~ed : ~o~ a ceramic hot platé. Evidënce of thërmal âdhesion is noted`at ~arlous temperatures.
i; ..The water-absorben~resin particlesiàrè basèd `
on~polyacrylic;a~id cros'sii~ed'with~rtrimlethylol propane 30 sandspartially.~neu~ràlized wiæh~isodium'jhydroxidë'to!à
level.~ofi~68 pèrcent~neutralization'. The~ ther~soplastic 3i polymers are polyvinylide~e~pyrroiidd~ë~of~thrëë
molecular weights (8000~ 38~000 and 630~000); ~wo polyethylene oxite based polymers (MW lOO,OOO and : -- : .
600~0003 and a low molecular weight polyvinyl alcohol, :. .
,0 - . . . . .
.
'1 , ~ : .
~: , ... . . , . . .. . . . . ~ ... - .
WO91/18~2 PCT/GB91~00780 ~ ~. 20 ".~
available fro~ Air Products under the trade name Airvol 205.
Results Coatin~ Affinity Test Good coating affinil:y is demonstrated by the polymer adhering to the water absorbent resin thermoplastic particles. Poor coating afflnity is demonstrated by the presence of the thermoplastic polymer as a slowly settling dust once shaking is discontinued. The polyvinyl pyrrolidone demonstrated excellent coating affinity at all molecular weights. The polyethylene oxide polymers demonstrate limited affi~ity for the water absorbent resin by the presence of dust at 10, 15 and 20 parts of thermoplastic polymer per hundred parts of resin. The polyvinyl alcohol exhibits excellent powder coating affinicy, as only a slight amount of free dust is detected at 20 parts of polyvinyl alcohol.
Results Bondin:~ Testi;
, .. ... . . . . ............... .
The watèr absorbént resin blendéd with polyethyie~e oxide at 5 parts demonstrate good adhesio~.
Water absorbeit resin particles coated wlth polyvinyl pyrrolido~es of all ~hree molecular ~eights demonstrate good bonding characteristics at 75~C~ The polyvinyl alcohoa coated water-absorbent~resins-demonstrate a ~sl,i~ht adhesive character~at 100,C.~ The;results:of~both tests are.~jom~iled.r~in,Table~ L refers:.to low~molecular ~.
~eight,4Mire~ers t~o medlum molecular,weight, and ~ ~ :
refers to~highùmolecularlweight. ..;~ Lt~
,, ~: ' : . ' ', . : :: ' . . , : :,. : ' ' ' ,, - ~, Wo 91/~8042 pcr/GBs1/oo78o Tabl e E~am Polymer ~ ~rer Bond ng Coating Affinity ~ . . _ ._ . 1 Polyvinyl Good (75C) ExcellenVall levels pyrrolidone L
. ., _ _ 2 Polyvinyl Good (75C~ Excellent/all levels pyrroltdone M
. ~
3 Polyvinyl Good (75C) ExcellenVall levels p~l~one H _
4 Polyethylene oxide Good Good/ 5 parts; dust L present at 10, 15 and 20 parts
5 Polyetbyl-e ~-iCe G ~d bo~d ~ 5 p-~-H . dust present atlO, 15 and 2Q parts
6 Polyvinyl alcohol Slight (100C) Excellent/ Slight . dust at 20 parts _~ . ...
EXAMPLES 7-19 .' - 20 The properties of several adhesivized absorbent resin samples ~are:determi~ed.'':The :foll'owing'''standard ' ' test methods are'used.~
Absorption Under Load. , ;~.~. , ,,,. . ,. ~' A:nylQ~ screen (37:;~diàmeter; 100 m`esh) is pu't on top of perforated metal plate (holes with'~5 ..)~
followed by a filter paper and finally by a stai~less -steel cylinder, whose both ends are open, of 26 mm inner, :'`
' diameter~ 37 mm outer diameter and a hel'ght`'of 50'mm.'''' 160,.,~mg:,of:water-absorbent~resin:"partic'l'e's'`;a'r'e';pL`aced ', into ~he cyli~der;la~d~evenly~distributed,~-cove'~edlby 'a~
non-,woven~.sheet.~o~ a,diameter~of~'26-tmm-r'ànd'J`fin~ally'~'Ri3-'~ ;i presscd~down.~with a teflon pisto~'of 26'?=''~diàmèter~
.. . .
WO9lt18M2 PCT/GB91/007B0 z ~ ' 22 -'' i.
which carries the weight. The total weight of piston and cylinder is 104.4 g. The metal plate with the product in the cylinder on top is immersed into the 0.9 percent saline solu~ion such, that the nylon screen and the water surface have the same level so that the filter paper and the water-absorbent resin particles are able to absorb water without any static pressure.
A soak time of one hour is applied. The plate 10 is removed from the water reservoir and the excess water .:
in the holes of the plate and in the nylon screen is soaked up by paper tissues. Then the weight is removed from ~he swollen gel and the gel is weighed. The weight ratio of saline solution absorbed under load to wa~er~
absorben~ resin particles is ~he absorption under load (AUL).
' Centrifu~e Capacity ~ . 200 mg ,of~water-absorbent resin particles are place within a sealable tea bag (63,5 x 76.2 mm), i~mersed for 30 minutes into a 0.9 percent saline sol~ion and then centrifuged for three minutes at 1600 rpm. The weigh~ ratio of saline'solution absorbed'~o'-- '' '' . water-absorbent..resin particles,:is the:absorbency capacity!.~cc)- ~. ,,.; .i,: .;."~.~ .,'. m i.~ ,`; i r \ `~
3 0 1 ~ I r ~ t~ u .
Sp'ee~d''~,o,f Absorption' ~ ,,A.6.cm~di met,er~,non~ ,o,ve~,:sheet,:available from`
- Suominen~Novelling 3 T,.391~is;,plac'ed -.! on~the~.test-.~plate of~i a Demand Absorbency,.~,~ester~ availablei~rom Co~5MS,rJ0.50;~
g o~ water-absorbent resin~isrplaced in the.cen~ër~5 cm^-;
`' ' . .
. ~
. .
WO9l/l8042 PCT/GB91/00780 3 ;2~523`~
of the non-woven sheet. A 0.9 percent NaCl in water solution is contacted with the resin. The time over which 10.1 ml of solution is absorbed by the resin is noted. This is the speed of absorption. The solution is added for 30 minutes. The absorbed volume i~ recorded.
20 filter papers (11.5 x ll.S cm) are weighed. An 11.3 c~ diameter non-woven sheet is placed over the swollen absorbent resin and 20 square filter papers 11.5 x 11.5 cm are placed over the non-woven sheet. Thereafter a load of 1917.7 g (11.5 x ll.S cm) is placed over the filter papers to give a load of 1973 g (3.~5 kPa on 8 cm diameter area). After 5 minutes the load is released and the wetted filter papers are weighed. The maximum free absorp~ion capacity (MFAC 91 g) is calculated as follows:
; MFAC = (Vl-Vlb) d 0.5 Vl is the absorbed volume of the absorbent resin Vlb is the absorbed volume of the filter papers znd non-woven sheets of a blank, run without~absorbent resin;
d is the density of the saline solution (1.01) The retention under pressure (PT, g/~) is 25 calculated as follows: `
R = Vl x d - (P2-Pl) 0.5 Pl is the weight of the dry filter papers ;i~
P~ is the weight of the wetted filter papers.
.
: ., -, .
.; .
.
'" ' ,~
: ~ ' ' ', WO91/18~2 PCT/GB91/00780 2 ~ 24 Bulk Density Bulk density is calculated acc~rding to ASTM D-l895-69.
FLow Rate .
Flow rate is determinated according eO ASTM
Dl895-69, and represents the time it takes lO0 grams of material to flow out of a funnel ha~ing a 9.5 mm opening.
` , The water absorbent resin is a polyacrylic acid crosslinked with trimethylol propane and partially :15 ~eutralized with sodium hydroxide, 68 percent. The water absorbent resin particles demonstrate two particle size distributions, Standard, 97 percent between O.l and 0.8 mm; and fine 99 percent less than 0.31 mm. The :. thermoplastic polymer used is polyvinyl pyrrolidone :~20 (PVP) of;three different molecular weights; (L) 8000, tM) 38,000, and (H)-:630,000. The results are compiled in . . .
TabIe II. ~ . -. ~ . . .. : . .
,~ . . .
, .
,. . : . ., , i ,, -c ,~ ~
; : . . i ' - ` ' ' ! ' "
' ' ' ' . ' ' ' ' ' ~:
..-~:
- ~ . . .. . . . .. ~ . . ,,. , ,: . . .. . . . . . . . .
WO 91/~8042 PCI`/GB91/00780 ! `` 2 5 ~ ~ , Z~
.
~'o~ o c~l o Oo o r~ I~ r~ O O L~. ~ ~ ..
_ ~ O~ _ O~ _ CJ~ . ~ _ _ _ ,~_ ... ___ _ _ _ _ _ _ _ ~ c ~ . . r ~ r~ o ~ ~ o~ ~ ~ ~ r~l ~ ~ .r~l O ~ O~ ~ a~ ~, ~D O U~ O
m C~ ~ ~D D D r~ ~D D 9 ~ ID ~D D ~ ~
o o o o o o o o C~ o o o o ___ _ _ _ _ _ _ _ _ _ '.
~:n . . .' ~r, o~, .- oo, ~ ~ oo , ~- C:~ ~
~: u~ r~J , ~ O ~ _ O O ,~ ~ ~ ~D .
___ _ _ _ _ _ __ _ ~ o C ~ .
E ~ a~ E ~ ~ ^~ ~ ~D o c~. ~r ~ ~ ~ ~ ~i cn O ~1 _ a~ o ~ o I~ o r~ ~
/~ es ~r i. e~ ~ ~ ~ ~ ~ ~ ~ ~ :
U
~C~_ ,o c~_ ~ co ~ ~ r~l ~ ~2 c ~ ~ ~D es Lr~ ,.
n~ _ o ~s, . _ . . ~ ~ o L~l ~ , ~ ~ _ ~ . r~l _ ~l ~ ~ _ ~ ~ ~ ~
_ __ _ _ . _ _ __ __ _ cn ., ..
cn o~ L~ o L~l Ln ~ c~ u: 9 _ ~ .- ~ O L~l D L~ ~ ~ ~9 O
_ o~ ~ ~ Lr~ I~ o~ I~ co r~ oo r~ D
~ ~ r~l ~ ~ ~ ~l ~ ~ ~ ~l ~ ~
.._. _ , _ _ .~ _ _ _ _ . _-- ' .
n ~ " ~ '~r~'' ' ~ ' ,~- --~
. cn ~ ~i r~ ~_ I~' ~ .. I~ I~ .. Lri . U-.,,.- ,, - - - - . - ~ - - , - - ,........
~ ~ ' ~ ~ ~ ~ . ..0~:, '~ ~8'. ....~.,. ~. . . '' ` `' ' ~
:` 3 O O O O . O C~ .
~ U~ L~ _ Lrs Lrs _ ~ Lrl Ln .. _ _ ~ _ _ _ _ _ _ _ _ _ . .''.. " _` ,,,,~ ,`,,S' ;~ ~,'.t .. :~' ~ L~. ;~ _~ _ C ), LL . C ~ L~ ,., C ~ .C; ~; ~.. ..
._ -, .... __ ._. _ : ; _ _ _ _ _ _ ,!,, ., .,,~,,. ~1 ':,` ,,.. /.: ., .~ ".~ ~ . ,~,, . j~ - , ,.
s C. ~ 4;1 ~ _ ' .! 1 `;~:-i .i ;1, .~ - ,,; n ' ! ,j ~ ~ ~,S ~:~ ,''J
,, Q ~ - ~ . o ~;. ' ,.~ ~;~ :~ ~ ~ ~ :~ ~ I I ~ o ~ 3 ~
., , _ _ __ _ _ _ _ _ ; __ _ _ ~
r, ; f 1~ ~ . ~ . ~ ,. ~O _r .i '; _ ~ ~ ; ~ ~ ~
: :.
,: : : : .
.: : ~ ' ;. ' . ` ` ' ' WO91/18~12 pcT/Gs9l/oo78o 2 3 26 -`
Examples 20-2~
83 parts by weight of the water absorbent resin described in the previous examples, 5 parts by weight of polyvinylpyrrolidone (8,000 mw) and 12 parts by weight of a hydrophilic polymer are put into a 200 ml plastic bottle. Two different hydrophilic polymers are separately usedj methyl cellulose and a mix~ure of 12 percent xanthum and 88'percent guar. The bo~tle is closed and shaken for 2 hours.' The compositions are then tested for centrifuge capacity, retention under pressure (PF), speed of absorption and Demand Absorption (DAT). A
Control is prepared without the hydrophilic polymer using 9S par~s absorbent resin and 5 parts , polyvinylpyrrolidone. The results are compiled in Table III.
- - ~ , - Table III
.~_ _ . _ _ _ _ Exa Hydrophilic Centrifug under Absorben Absorptio 10 mp Polymer e apaclty P~euure cy~DA~ nSpeec . ;31.1 31 :` 40 ~ 1~3?
21GuarXanthum 306 ~83 ~ ` 40 '~ 7~ ' 22Methylceilulose 273 246 39 51 15, ~ ; , ' ' ' , ' ' Examples;23-~4i ,A mixture of ,130 gràms'of 56 percent by'weight cellulosic fiber,~l4 percént~by"weight':'sy`nthetic fiber (polyethylene coated polypropyle~e fiber? and 30 percent ,by weight of a~wa'ter, absorbent res'in~comprising.95 percen~.. of- a plrtially ~eutralized polya~rylic acid ,',~
crossllnked Iw1th, !trimethylol~ propan. ~t68 percent `~ h NaOH) and 0.5 percent by weight~polyvinylpyrrolidone are . . .
., ,; ': ' , . . . ..... . .. . . .. ..
WO91/18~2 PCT/GB91/00~80 f- 27 2~8~-3 `
contacted and thermally bonded at elevated temperacures such that a coherent matrix is formed.
A second sample comprises two substantially equal layers o~ non-wove~`celIulosic fibérs with a layer of the water abso~bent resin, without a thermoplastic polymer, disposed between ~he layers of cellulosic fibers. The sample comprises 90 percent by weight of the cellulosic fiber, and 10 percent by weight of water absorbent resin, and has a unit weight of 470 g/m2.
The two samples are tes~ed as described hereinaf~er.
.
; A Fritsch "Analysette 3" apparatus is arranged such tha~ five sieves are arra~ged from top to bottom, 800 um~ 400 um, 315 um~ 200 um, and lO0 um~ with a pan ~ below the screens~ A sample of 5 to lO grams is weighed.
; The sample is placed on the top sieve, and a cover is placed over the sieve. The sieve assembly is securely fastened in the Fritsch apparatus.
": ~ .
The apparatus is shaken for 15 minutes. The top screen with ~he sample is placed on a balance and the ~
bala~ce is set ~o 0Ø The sample is removed from the ~, . . . . . . . .
top scree~ and th~ screen is brushed. The empty screen is placed on the balance. The negative weight is the final weight o~ the sample on the screen. The weight ~t~
loss of each sample due to shaking is calculated. The results are compiled in Table-IV.
: . . -?~
.~ . .
: , WO91/18~2 PCT/GB91/00780 Table IV
,__ ._~ ~ ~
Example Beglnnlng End weight g 1~ We gh~
23~ 9.5 g.1 4 , ~
24 6.7 6.7 0 .
~-~r-t an exa ~ lnvention ~
The loss in Examp~e 23 show loss of both water absorbent polymer and cellulosic fibers 7 it is difficult to determine the exact composieion of the material removed rom the absorbent structure.
; 5 , . '' ' ' "
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~ 25 ~ :
, ~
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.. . . . . .
.
EXAMPLES 7-19 .' - 20 The properties of several adhesivized absorbent resin samples ~are:determi~ed.'':The :foll'owing'''standard ' ' test methods are'used.~
Absorption Under Load. , ;~.~. , ,,,. . ,. ~' A:nylQ~ screen (37:;~diàmeter; 100 m`esh) is pu't on top of perforated metal plate (holes with'~5 ..)~
followed by a filter paper and finally by a stai~less -steel cylinder, whose both ends are open, of 26 mm inner, :'`
' diameter~ 37 mm outer diameter and a hel'ght`'of 50'mm.'''' 160,.,~mg:,of:water-absorbent~resin:"partic'l'e's'`;a'r'e';pL`aced ', into ~he cyli~der;la~d~evenly~distributed,~-cove'~edlby 'a~
non-,woven~.sheet.~o~ a,diameter~of~'26-tmm-r'ànd'J`fin~ally'~'Ri3-'~ ;i presscd~down.~with a teflon pisto~'of 26'?=''~diàmèter~
.. . .
WO9lt18M2 PCT/GB91/007B0 z ~ ' 22 -'' i.
which carries the weight. The total weight of piston and cylinder is 104.4 g. The metal plate with the product in the cylinder on top is immersed into the 0.9 percent saline solu~ion such, that the nylon screen and the water surface have the same level so that the filter paper and the water-absorbent resin particles are able to absorb water without any static pressure.
A soak time of one hour is applied. The plate 10 is removed from the water reservoir and the excess water .:
in the holes of the plate and in the nylon screen is soaked up by paper tissues. Then the weight is removed from ~he swollen gel and the gel is weighed. The weight ratio of saline solution absorbed under load to wa~er~
absorben~ resin particles is ~he absorption under load (AUL).
' Centrifu~e Capacity ~ . 200 mg ,of~water-absorbent resin particles are place within a sealable tea bag (63,5 x 76.2 mm), i~mersed for 30 minutes into a 0.9 percent saline sol~ion and then centrifuged for three minutes at 1600 rpm. The weigh~ ratio of saline'solution absorbed'~o'-- '' '' . water-absorbent..resin particles,:is the:absorbency capacity!.~cc)- ~. ,,.; .i,: .;."~.~ .,'. m i.~ ,`; i r \ `~
3 0 1 ~ I r ~ t~ u .
Sp'ee~d''~,o,f Absorption' ~ ,,A.6.cm~di met,er~,non~ ,o,ve~,:sheet,:available from`
- Suominen~Novelling 3 T,.391~is;,plac'ed -.! on~the~.test-.~plate of~i a Demand Absorbency,.~,~ester~ availablei~rom Co~5MS,rJ0.50;~
g o~ water-absorbent resin~isrplaced in the.cen~ër~5 cm^-;
`' ' . .
. ~
. .
WO9l/l8042 PCT/GB91/00780 3 ;2~523`~
of the non-woven sheet. A 0.9 percent NaCl in water solution is contacted with the resin. The time over which 10.1 ml of solution is absorbed by the resin is noted. This is the speed of absorption. The solution is added for 30 minutes. The absorbed volume i~ recorded.
20 filter papers (11.5 x ll.S cm) are weighed. An 11.3 c~ diameter non-woven sheet is placed over the swollen absorbent resin and 20 square filter papers 11.5 x 11.5 cm are placed over the non-woven sheet. Thereafter a load of 1917.7 g (11.5 x ll.S cm) is placed over the filter papers to give a load of 1973 g (3.~5 kPa on 8 cm diameter area). After 5 minutes the load is released and the wetted filter papers are weighed. The maximum free absorp~ion capacity (MFAC 91 g) is calculated as follows:
; MFAC = (Vl-Vlb) d 0.5 Vl is the absorbed volume of the absorbent resin Vlb is the absorbed volume of the filter papers znd non-woven sheets of a blank, run without~absorbent resin;
d is the density of the saline solution (1.01) The retention under pressure (PT, g/~) is 25 calculated as follows: `
R = Vl x d - (P2-Pl) 0.5 Pl is the weight of the dry filter papers ;i~
P~ is the weight of the wetted filter papers.
.
: ., -, .
.; .
.
'" ' ,~
: ~ ' ' ', WO91/18~2 PCT/GB91/00780 2 ~ 24 Bulk Density Bulk density is calculated acc~rding to ASTM D-l895-69.
FLow Rate .
Flow rate is determinated according eO ASTM
Dl895-69, and represents the time it takes lO0 grams of material to flow out of a funnel ha~ing a 9.5 mm opening.
` , The water absorbent resin is a polyacrylic acid crosslinked with trimethylol propane and partially :15 ~eutralized with sodium hydroxide, 68 percent. The water absorbent resin particles demonstrate two particle size distributions, Standard, 97 percent between O.l and 0.8 mm; and fine 99 percent less than 0.31 mm. The :. thermoplastic polymer used is polyvinyl pyrrolidone :~20 (PVP) of;three different molecular weights; (L) 8000, tM) 38,000, and (H)-:630,000. The results are compiled in . . .
TabIe II. ~ . -. ~ . . .. : . .
,~ . . .
, .
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..-~:
- ~ . . .. . . . .. ~ . . ,,. , ,: . . .. . . . . . . . .
WO 91/~8042 PCI`/GB91/00780 ! `` 2 5 ~ ~ , Z~
.
~'o~ o c~l o Oo o r~ I~ r~ O O L~. ~ ~ ..
_ ~ O~ _ O~ _ CJ~ . ~ _ _ _ ,~_ ... ___ _ _ _ _ _ _ _ ~ c ~ . . r ~ r~ o ~ ~ o~ ~ ~ ~ r~l ~ ~ .r~l O ~ O~ ~ a~ ~, ~D O U~ O
m C~ ~ ~D D D r~ ~D D 9 ~ ID ~D D ~ ~
o o o o o o o o C~ o o o o ___ _ _ _ _ _ _ _ _ _ '.
~:n . . .' ~r, o~, .- oo, ~ ~ oo , ~- C:~ ~
~: u~ r~J , ~ O ~ _ O O ,~ ~ ~ ~D .
___ _ _ _ _ _ __ _ ~ o C ~ .
E ~ a~ E ~ ~ ^~ ~ ~D o c~. ~r ~ ~ ~ ~ ~i cn O ~1 _ a~ o ~ o I~ o r~ ~
/~ es ~r i. e~ ~ ~ ~ ~ ~ ~ ~ ~ :
U
~C~_ ,o c~_ ~ co ~ ~ r~l ~ ~2 c ~ ~ ~D es Lr~ ,.
n~ _ o ~s, . _ . . ~ ~ o L~l ~ , ~ ~ _ ~ . r~l _ ~l ~ ~ _ ~ ~ ~ ~
_ __ _ _ . _ _ __ __ _ cn ., ..
cn o~ L~ o L~l Ln ~ c~ u: 9 _ ~ .- ~ O L~l D L~ ~ ~ ~9 O
_ o~ ~ ~ Lr~ I~ o~ I~ co r~ oo r~ D
~ ~ r~l ~ ~ ~ ~l ~ ~ ~ ~l ~ ~
.._. _ , _ _ .~ _ _ _ _ . _-- ' .
n ~ " ~ '~r~'' ' ~ ' ,~- --~
. cn ~ ~i r~ ~_ I~' ~ .. I~ I~ .. Lri . U-.,,.- ,, - - - - . - ~ - - , - - ,........
~ ~ ' ~ ~ ~ ~ . ..0~:, '~ ~8'. ....~.,. ~. . . '' ` `' ' ~
:` 3 O O O O . O C~ .
~ U~ L~ _ Lrs Lrs _ ~ Lrl Ln .. _ _ ~ _ _ _ _ _ _ _ _ _ . .''.. " _` ,,,,~ ,`,,S' ;~ ~,'.t .. :~' ~ L~. ;~ _~ _ C ), LL . C ~ L~ ,., C ~ .C; ~; ~.. ..
._ -, .... __ ._. _ : ; _ _ _ _ _ _ ,!,, ., .,,~,,. ~1 ':,` ,,.. /.: ., .~ ".~ ~ . ,~,, . j~ - , ,.
s C. ~ 4;1 ~ _ ' .! 1 `;~:-i .i ;1, .~ - ,,; n ' ! ,j ~ ~ ~,S ~:~ ,''J
,, Q ~ - ~ . o ~;. ' ,.~ ~;~ :~ ~ ~ ~ :~ ~ I I ~ o ~ 3 ~
., , _ _ __ _ _ _ _ _ ; __ _ _ ~
r, ; f 1~ ~ . ~ . ~ ,. ~O _r .i '; _ ~ ~ ; ~ ~ ~
: :.
,: : : : .
.: : ~ ' ;. ' . ` ` ' ' WO91/18~12 pcT/Gs9l/oo78o 2 3 26 -`
Examples 20-2~
83 parts by weight of the water absorbent resin described in the previous examples, 5 parts by weight of polyvinylpyrrolidone (8,000 mw) and 12 parts by weight of a hydrophilic polymer are put into a 200 ml plastic bottle. Two different hydrophilic polymers are separately usedj methyl cellulose and a mix~ure of 12 percent xanthum and 88'percent guar. The bo~tle is closed and shaken for 2 hours.' The compositions are then tested for centrifuge capacity, retention under pressure (PF), speed of absorption and Demand Absorption (DAT). A
Control is prepared without the hydrophilic polymer using 9S par~s absorbent resin and 5 parts , polyvinylpyrrolidone. The results are compiled in Table III.
- - ~ , - Table III
.~_ _ . _ _ _ _ Exa Hydrophilic Centrifug under Absorben Absorptio 10 mp Polymer e apaclty P~euure cy~DA~ nSpeec . ;31.1 31 :` 40 ~ 1~3?
21GuarXanthum 306 ~83 ~ ` 40 '~ 7~ ' 22Methylceilulose 273 246 39 51 15, ~ ; , ' ' ' , ' ' Examples;23-~4i ,A mixture of ,130 gràms'of 56 percent by'weight cellulosic fiber,~l4 percént~by"weight':'sy`nthetic fiber (polyethylene coated polypropyle~e fiber? and 30 percent ,by weight of a~wa'ter, absorbent res'in~comprising.95 percen~.. of- a plrtially ~eutralized polya~rylic acid ,',~
crossllnked Iw1th, !trimethylol~ propan. ~t68 percent `~ h NaOH) and 0.5 percent by weight~polyvinylpyrrolidone are . . .
., ,; ': ' , . . . ..... . .. . . .. ..
WO91/18~2 PCT/GB91/00~80 f- 27 2~8~-3 `
contacted and thermally bonded at elevated temperacures such that a coherent matrix is formed.
A second sample comprises two substantially equal layers o~ non-wove~`celIulosic fibérs with a layer of the water abso~bent resin, without a thermoplastic polymer, disposed between ~he layers of cellulosic fibers. The sample comprises 90 percent by weight of the cellulosic fiber, and 10 percent by weight of water absorbent resin, and has a unit weight of 470 g/m2.
The two samples are tes~ed as described hereinaf~er.
.
; A Fritsch "Analysette 3" apparatus is arranged such tha~ five sieves are arra~ged from top to bottom, 800 um~ 400 um, 315 um~ 200 um, and lO0 um~ with a pan ~ below the screens~ A sample of 5 to lO grams is weighed.
; The sample is placed on the top sieve, and a cover is placed over the sieve. The sieve assembly is securely fastened in the Fritsch apparatus.
": ~ .
The apparatus is shaken for 15 minutes. The top screen with ~he sample is placed on a balance and the ~
bala~ce is set ~o 0Ø The sample is removed from the ~, . . . . . . . .
top scree~ and th~ screen is brushed. The empty screen is placed on the balance. The negative weight is the final weight o~ the sample on the screen. The weight ~t~
loss of each sample due to shaking is calculated. The results are compiled in Table-IV.
: . . -?~
.~ . .
: , WO91/18~2 PCT/GB91/00780 Table IV
,__ ._~ ~ ~
Example Beglnnlng End weight g 1~ We gh~
23~ 9.5 g.1 4 , ~
24 6.7 6.7 0 .
~-~r-t an exa ~ lnvention ~
The loss in Examp~e 23 show loss of both water absorbent polymer and cellulosic fibers 7 it is difficult to determine the exact composieion of the material removed rom the absorbent structure.
; 5 , . '' ' ' "
'~ , ,. ',' ,.' ~' ``~ ` ' ;``' ' ' , ' ' ` . ' '`~' ~
~71~s 1 5 .P ~ `` ~ ~ t , .
~ 25 ~ :
, ~
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.. . . . . .
.
Claims (10)
1. Water-absorbent resin particles comprising a carboxyl containing water-absorbent resin characterized in that the particles further comprise on the surface a thermoplastic polymer having adhesive properties and hydrophilic character.
2. Water-absorbent resin particles according to Claim 1 wherein the thermoplastic polymer has a softening point from 35°C to 170°C.
3. Water-absorbent resin particles according to Claim 1 or Claim 2 which is further characterized by the presence of a flow control additive.
4. Water-absorbent resin particles according to Claim 3 which comprise from 1 to 30 parts by weight of thermoplastic polymer and from 1 to 15 parts by weight of flow control additive per hundred parts of carboxyl containing water-absorbent resin.
5. Water-absorbent resin particles according to Claim 3 or Claim 4 wherein the flow control agent is an inert powder which promotes flow.
6. Water-absorbent resin particles according to Claim 3 or Claim 4 characterized in that the flow control additive is a polymer which is soluble or dispersable in aqueous fluids and increases the viscosity of aqueous fluids.
7. Water-absorbent resin particles according to any one of Claims 3 to 6 which comprises A) a carboxyl containing water-absorbent resin comprising a hydrolyzate of a starch-acrylonitrile graft copolymer, a partially neutralized produce of a starch-acrylic acid graft copolymer, a saponification product of a vinyl acetate acrylic ester copolymer, a hydrolyzate of an acrylonitrile copolymer, a crosslinked product of a hydrolyzate of an acrylonitrile copolymer, a hydrolyzate of an acrylamide copolymer, a crosslinked product of a hydrolyzate of an acrylamide copolymer, a partially neutralized product of polyacrylic acid, or a crosslinked product of partially neutralized polyacrylic acid, wherein such water-absorbent resin may optionally be surface crosslinked by a polyhydroxy compound capable of reacting with the carboxyl moieties of the water-absorbent resin or may optionally have coated on the 3 PCT/??91/00780 surface a nonionic surfactant having an HLB of from 3 to 10;
B) a thermoplastic polymer comprising a polyvinyl pyrrolidone, a polyvinyl pyrrolidone-vinyl acetate copolymer, a polyethylene oxide, or a polyethylene oxide capped on one end with a hydrophobic hydrocarbon moiety; and C) a flow control agent comprising a polysaccharide, a modified polysaccharide or a mixture thereof.
B) a thermoplastic polymer comprising a polyvinyl pyrrolidone, a polyvinyl pyrrolidone-vinyl acetate copolymer, a polyethylene oxide, or a polyethylene oxide capped on one end with a hydrophobic hydrocarbon moiety; and C) a flow control agent comprising a polysaccharide, a modified polysaccharide or a mixture thereof.
8. A process for preparing water-absorbent resin particles according to any one of Claims 1 to 7 which process comprises A) contacting particles of a water-absorbent resin containing carboxyl moities with a thermoplastic resin having hydrophilic character and having adhesive properties until the mixture no longer flows freely; and B) optionally, contacting the water-absorbent resin and thermoplastic polymer mixture with a flow control additive and blending until the mixture flows freely.
9. A water absorbent article comprising a woven or non-woven mass of fibers having bound thereto water-absorbent resin particles according to any one of Claims 1 to Claim 7.
4 PCT/??91/00780
4 PCT/??91/00780
10. A water-absorbent resin composition comprising water-absorbent resin particles containing carboxyl moieties characterized in that the composition also comprises a flow control additive which is a hydrophilic polymer which dissolves or disperses in aqueous fluids and which increases the viscosity of such aqueous fluids.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9011250.9 | 1990-05-19 | ||
| GB909011250A GB9011250D0 (en) | 1990-05-19 | 1990-05-19 | Attachment of absorbent granules or fibres in open structure webs |
| GB919102143A GB9102143D0 (en) | 1991-01-31 | 1991-01-31 | Viscosity adjustment within absorbent hygiene products |
| GB9102143.6 | 1991-01-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2082623A1 true CA2082623A1 (en) | 1991-11-20 |
Family
ID=26297100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2082623 Abandoned CA2082623A1 (en) | 1990-05-19 | 1991-05-17 | Water-absorbent resin particles for absorbent structures |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0530231A1 (en) |
| JP (1) | JPH05507511A (en) |
| AU (1) | AU7863091A (en) |
| CA (1) | CA2082623A1 (en) |
| WO (1) | WO1991018042A1 (en) |
Families Citing this family (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU643058B2 (en) * | 1990-08-30 | 1993-11-04 | Terumo Kabushiki Kaisha | Wound-covering materials |
| DE4206857C2 (en) * | 1992-03-05 | 1996-08-29 | Stockhausen Chem Fab Gmbh | Polymer composition, absorbent material composition, their production and use |
| JP3323232B2 (en) * | 1992-05-23 | 2002-09-09 | 住友精化株式会社 | Composite composition of superabsorbent resin particles |
| TW320647B (en) * | 1993-02-24 | 1997-11-21 | ||
| AU4276893A (en) * | 1993-03-29 | 1994-10-24 | Dow Chemical Company, The | Absorbent polymer having reduced dusting tendencies |
| SE503798C2 (en) * | 1994-10-27 | 1996-09-09 | Moelnlycke Ab | Absorbent product such as a diaper, incontinence cover, sanitary napkin or the like with a hydrophilic adhesive |
| US6103785A (en) * | 1998-03-26 | 2000-08-15 | Nippon Shokubai Co., Ltd. | Water-absorbing agent and its production process and use |
| US6534572B1 (en) | 1998-05-07 | 2003-03-18 | H. B. Fuller Licensing & Financing, Inc. | Compositions comprising a thermoplastic component and superabsorbent polymer |
| JP2000212458A (en) * | 1999-01-25 | 2000-08-02 | Sumitomo Seika Chem Co Ltd | Highly water-absorptive resin particle |
| DE19909653A1 (en) | 1999-03-05 | 2000-09-07 | Stockhausen Chem Fab Gmbh | Powdery, crosslinked, aqueous liquids and blood-absorbing polymers, processes for their preparation and their use |
| EP1072630B1 (en) * | 1999-07-26 | 2004-12-01 | Nippon Shokubai Co., Ltd. | Water-absorbing composition and its use |
| WO2001023012A1 (en) * | 1999-09-30 | 2001-04-05 | The Dow Chemical Company | Binding superabsorbent polymers to substrates |
| US6720073B2 (en) * | 2000-04-07 | 2004-04-13 | Kimberly-Clark Worldwide, Inc. | Material enhancement to maintain high absorbent capacity under high loads following rigorous process conditions |
| MXPA03000200A (en) * | 2000-07-24 | 2003-09-22 | Dow Global Technologies Inc | Thermoplastic superabsorbent polymer blend compositions and their preparation. |
| US20030119406A1 (en) | 2001-12-20 | 2003-06-26 | Abuto Francis Paul | Targeted on-line stabilized absorbent structures |
| US6709613B2 (en) | 2001-12-21 | 2004-03-23 | Kimberly-Clark Worldwide, Inc. | Particulate addition method and apparatus |
| KR20030062738A (en) * | 2002-01-18 | 2003-07-28 | 주식회사 디엠씨 | An absorbent resin composition and a method for manufacturing the same |
| EP1594557B1 (en) | 2003-02-10 | 2019-05-01 | Nippon Shokubai Co., Ltd. | Water-absorbent resin composition and its production process |
| WO2004096301A2 (en) * | 2003-04-24 | 2004-11-11 | Dow Global Technologies Inc. | Fluid-absorbent compositions and articles, porous articles, and methods for making the same |
| US7169843B2 (en) | 2003-04-25 | 2007-01-30 | Stockhausen, Inc. | Superabsorbent polymer with high permeability |
| DE10334286B4 (en) | 2003-07-25 | 2006-01-05 | Stockhausen Gmbh | Powdered, water-absorbing polymers with fine particles bound by means of thermoplastic adhesives, process for their preparation and chemical products and compounds containing them |
| US7173086B2 (en) | 2003-10-31 | 2007-02-06 | Stockhausen, Inc. | Superabsorbent polymer with high permeability |
| JP4676747B2 (en) * | 2004-11-24 | 2011-04-27 | 株式会社日本触媒 | Water-absorbing resin particles and production method thereof, water-absorbing resin particle composition, and use |
| US7812082B2 (en) | 2005-12-12 | 2010-10-12 | Evonik Stockhausen, Llc | Thermoplastic coated superabsorbent polymer compositions |
| DE102006060156A1 (en) * | 2006-12-18 | 2008-06-19 | Evonik Stockhausen Gmbh | Water-absorbing polymer structures produced using polymer dispersions |
| US8536278B2 (en) | 2008-07-11 | 2013-09-17 | Basf Se | Method for the surface post-crosslinking of water absorbing polymer particles |
| JP6096199B2 (en) * | 2012-08-27 | 2017-03-15 | 株式会社日本触媒 | Particulate water-absorbing agent and method for producing the same |
| MY177389A (en) * | 2014-05-23 | 2020-09-14 | Sdp Global Co Ltd | Water-absorbing resin particles, absorber comprising same, and absorbent article |
| KR102215025B1 (en) | 2017-06-30 | 2021-02-10 | 주식회사 엘지화학 | Preparation method of super absorbent polymer and super absorbent polymer obtained by the method |
| KR102568226B1 (en) | 2017-12-11 | 2023-08-18 | 주식회사 엘지화학 | Super absorbent polymer and preparation method for the same |
| KR102418591B1 (en) | 2018-11-13 | 2022-07-07 | 주식회사 엘지화학 | Super absorbent polymer and preparation method for the same |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2222780C3 (en) * | 1972-05-10 | 1975-05-07 | Vereinigte Papierwerke Schickedanz & Co, 8500 Nuernberg | Process for determining finely divided hydrocolloid swelling substances to be used in hygiene articles on documents |
| GB1517398A (en) * | 1975-04-18 | 1978-07-12 | Avtex Fibers Inc | Viscose fibres of high fluid-holding capacity |
| GB2007998B (en) * | 1977-10-18 | 1982-10-20 | Unilever Ltd | Absorbent materials |
| DE3741157A1 (en) * | 1987-12-04 | 1989-06-15 | Stockhausen Chem Fab Gmbh | METHOD FOR THE AGGLOMERATION OF WATER-SOILABLE POLYMER BY MELTING (SINTER) GRANULATION WITH POWDER-SUBSTANCES AND USE OF THE GRANULES |
-
1991
- 1991-05-17 WO PCT/GB1991/000780 patent/WO1991018042A1/en not_active Application Discontinuation
- 1991-05-17 JP JP91508962A patent/JPH05507511A/en active Pending
- 1991-05-17 AU AU78630/91A patent/AU7863091A/en not_active Abandoned
- 1991-05-17 EP EP19910909158 patent/EP0530231A1/en not_active Withdrawn
- 1991-05-17 CA CA 2082623 patent/CA2082623A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05507511A (en) | 1993-10-28 |
| WO1991018042A1 (en) | 1991-11-28 |
| EP0530231A1 (en) | 1993-03-10 |
| AU7863091A (en) | 1991-12-10 |
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