CA2316342A1 - Encapsulated hydrogels - Google Patents
Encapsulated hydrogels Download PDFInfo
- Publication number
- CA2316342A1 CA2316342A1 CA002316342A CA2316342A CA2316342A1 CA 2316342 A1 CA2316342 A1 CA 2316342A1 CA 002316342 A CA002316342 A CA 002316342A CA 2316342 A CA2316342 A CA 2316342A CA 2316342 A1 CA2316342 A1 CA 2316342A1
- Authority
- CA
- Canada
- Prior art keywords
- hydrogel
- group
- absorption
- hydrophilic
- encapsulated
- 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
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
- C08F251/02—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof on to cellulose or derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
- C08L51/02—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to polysaccharides
-
- 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
The invention relates to a hydrogel, comprising a hydrophilic hydrogel with a high swelling capacity which is reversibly coated with a material which delays or prevents the uptake of water or aqueous fluids. The invention also relates to a method for producing the hydrogel and to a method for releasing said hydrophilic hydrogel with a high swelling capacity.
Description
Encapsulated hydrogels The present invention relates to encapsulated hydrogels, i.e. hydrogels whose ability to absorb water and aqueous liquids has been reversibly blocked, to processes for their preparation, and also to processes for reversing the encapsulation.
Particular examples of hydrophilic, highly swellable hydrogels are polymers made from (co)polymerized hydrophilic monomers or are graft (co)polymers made from one or more hydrophilic monomers on a suitable graft base, or are crosslinked cellulose ethers or crosslinked starch ethers or crosslinked carboxymethylcellulose or partially crosslinked polyalkylene oxide or natural products which are swellable in aqueous liquids, for example guar derivatives. The manufacture of diapers, tampons, sanitary towels and other hygiene products uses hydrogels of this type as products which absorb aqueous solutions. The hydrogels are also used as water-retaining agents in market gardening.
Hydrophilic, highly swellable hydrogels are increasingly required to be introduced into sheeting made from synthetic or natural fibers or from mixtures of fibers, or into water-absorbing layers made from plastic foam or from latex foam (see, for example, EP-A-427219 or DE-A-4.4 18 319). The rapid swellability of the abovementioned hydrogels in water or in aqueous liquids, a property which is highly valued in the final product, proves extremely problematic in these processes, which usually operate in aqueous media. The processing of conventional hydrogels by "wet-lay"
processes, in particular their use on papermaking machines, is not possible in industry. There is therefore an urgent need for a solution to this problem.
It has now been found that it is possible to encapsulate the hydrogel - particles reversibly, i.e. to coat them reversibly with a water-resistant film which delays or even completely prevents the absorption of the liquid. The effect simulates masking of the high swellability of the hydrogels, and they can therefore be processed as aqueous pastes or slurries in aqueous processes together with other materials, such as mineral fibers, phyllosilicates, mineral binders or cellulose powders, without swelling or absorbing water or aqueous liquids.
The' present invention therefore provides an encapsulated hydrogel, encompassing a hydrophilic, highly swellable hydrogel which is reversibly coated with a material which delays or prevents the absorption of water and of aqueous liquids.
Examples of materials suitable according to the invention for reversible coating of hydrogels are synthetic, naturally occurring or modified naturally occurring polymers or resins which can form, on the surface of the hydrogel particles, layers or films which are impermeable to water or resistant to water. Examples of suitable polymers are homo- andlor copolymers of olefinically unsaturated compounds, such as ethylene, propylene, styrene, esters of olefinically unsaturated acids and esters of olefinically unsaturated alcohols, amino resins, such as urea or melamine-aldehyde resins, phenolic resins, polyepoxides, polyester compounds, polyacetals, polycarbonates, polyamides, polyurethanes, silicone resins, ketone-aldehyde resins and alkyd resins.
The novel encapsulated hydrogels are prepared, for example, by applying the materials which prevent the absorption of water or of aqueous liquids to the hydrophilic, highly swellable hydrogel. The abovementioned materials are applied in apparatuses suitable for the purpose in particular as solutions, dispersions, suspensions, melts, or also as powder, onto the hydrophilic highly swellable hydrogel, which has generally been ground and screened. It is preferable to spray polymer solutions onto the hydrogel particles in reactors or in mixing and drying systems, such as Lbdige mixers, BEPEX mixers, NAUTA mixers, SCHUGGI mixers, PROCESSALL
apparatus, etc. Solutions may also be applied by spraying in fluidized-bed dryers. If the abovementioned materials are meltable powders or granules, they may firstly be applied in solid form to the hydrophilic, highly swellable hydrogel, so that in a subsequent step the temperature can be raised above the melting point of the powder or of the granules, in such a way that the surface of the particles becomes completely covered, and the resulting encapsulation has good strength.
The novel encapsulated hydrogels may also be prepared by using the methods described above to apply monomeric or oligomeric components to the surface of the particles and then converting these into layers or films which are water-impermeable or water-resistant by using, for example, polymerization, polycondensation or polyaddition. Examples of suitable monomeric or oligomeric components are epoxides, isocyanates, the compounds known as macromers, ketone resins, aldehyde resins, lactams, lactones, oxazolines, saturated and unsaturated polyesters and silicone resins.
Particular examples of the hydrophilic, highly swellable hydrogels on which the novel encapsulated hydrogels are based are polymers made from (co)polymerized hydrophilic monomers or are graft (co)polymers made from one or more hydrophilic monomers on a suitable graft base, or are crosslinked cellulose ethers or crosslinked starch ethers or natural products which are swellable in aqueous liquids, for example guar derivatives. These hydrogels are known to the person skilled in the art and are described, for example, in US-4,286,082, DE-C-27 06 135, US-4,340,706, DE-C-37 13 601, DE-C-28 40 010, DE-A-43 44 548, DE-A-40 20 780, DE-A-40 15 085, DE-A-39 17 846, DE-A-38 07 289, DE-A-35 33 337, DE-A-35 03 458, DE-A-42 44 548, DE-A-42 19 607, DE-A-40 21 847, DE-A-38 31 261, DE-A-35 11 086, DE-A-31 18 172, DE-A-30 28 043, DE-A-44 18 881, EP-A-801483, EP-A-455985, EP-A-467073, EP-A-312952, EP-A-205874, EP-A-499774, DE-A-26 12 846, DE-A-40 20 780, EP-A-205674, US-5,145,906, EP-A-530438, EP-A-670073, US-4,057,521, US-4,062,817, - US-4,525,527, US-4,295,987, US-5,011,892, US-4,076,663 or US-4,931,497. The content of the abovementioned patents is expressly incorporated into the present application by way of reference.
Particular examples of hydrophilic, highly swellable hydrogels are polymers made from (co)polymerized hydrophilic monomers or are graft (co)polymers made from one or more hydrophilic monomers on a suitable graft base, or are crosslinked cellulose ethers or crosslinked starch ethers or crosslinked carboxymethylcellulose or partially crosslinked polyalkylene oxide or natural products which are swellable in aqueous liquids, for example guar derivatives. The manufacture of diapers, tampons, sanitary towels and other hygiene products uses hydrogels of this type as products which absorb aqueous solutions. The hydrogels are also used as water-retaining agents in market gardening.
Hydrophilic, highly swellable hydrogels are increasingly required to be introduced into sheeting made from synthetic or natural fibers or from mixtures of fibers, or into water-absorbing layers made from plastic foam or from latex foam (see, for example, EP-A-427219 or DE-A-4.4 18 319). The rapid swellability of the abovementioned hydrogels in water or in aqueous liquids, a property which is highly valued in the final product, proves extremely problematic in these processes, which usually operate in aqueous media. The processing of conventional hydrogels by "wet-lay"
processes, in particular their use on papermaking machines, is not possible in industry. There is therefore an urgent need for a solution to this problem.
It has now been found that it is possible to encapsulate the hydrogel - particles reversibly, i.e. to coat them reversibly with a water-resistant film which delays or even completely prevents the absorption of the liquid. The effect simulates masking of the high swellability of the hydrogels, and they can therefore be processed as aqueous pastes or slurries in aqueous processes together with other materials, such as mineral fibers, phyllosilicates, mineral binders or cellulose powders, without swelling or absorbing water or aqueous liquids.
The' present invention therefore provides an encapsulated hydrogel, encompassing a hydrophilic, highly swellable hydrogel which is reversibly coated with a material which delays or prevents the absorption of water and of aqueous liquids.
Examples of materials suitable according to the invention for reversible coating of hydrogels are synthetic, naturally occurring or modified naturally occurring polymers or resins which can form, on the surface of the hydrogel particles, layers or films which are impermeable to water or resistant to water. Examples of suitable polymers are homo- andlor copolymers of olefinically unsaturated compounds, such as ethylene, propylene, styrene, esters of olefinically unsaturated acids and esters of olefinically unsaturated alcohols, amino resins, such as urea or melamine-aldehyde resins, phenolic resins, polyepoxides, polyester compounds, polyacetals, polycarbonates, polyamides, polyurethanes, silicone resins, ketone-aldehyde resins and alkyd resins.
The novel encapsulated hydrogels are prepared, for example, by applying the materials which prevent the absorption of water or of aqueous liquids to the hydrophilic, highly swellable hydrogel. The abovementioned materials are applied in apparatuses suitable for the purpose in particular as solutions, dispersions, suspensions, melts, or also as powder, onto the hydrophilic highly swellable hydrogel, which has generally been ground and screened. It is preferable to spray polymer solutions onto the hydrogel particles in reactors or in mixing and drying systems, such as Lbdige mixers, BEPEX mixers, NAUTA mixers, SCHUGGI mixers, PROCESSALL
apparatus, etc. Solutions may also be applied by spraying in fluidized-bed dryers. If the abovementioned materials are meltable powders or granules, they may firstly be applied in solid form to the hydrophilic, highly swellable hydrogel, so that in a subsequent step the temperature can be raised above the melting point of the powder or of the granules, in such a way that the surface of the particles becomes completely covered, and the resulting encapsulation has good strength.
The novel encapsulated hydrogels may also be prepared by using the methods described above to apply monomeric or oligomeric components to the surface of the particles and then converting these into layers or films which are water-impermeable or water-resistant by using, for example, polymerization, polycondensation or polyaddition. Examples of suitable monomeric or oligomeric components are epoxides, isocyanates, the compounds known as macromers, ketone resins, aldehyde resins, lactams, lactones, oxazolines, saturated and unsaturated polyesters and silicone resins.
Particular examples of the hydrophilic, highly swellable hydrogels on which the novel encapsulated hydrogels are based are polymers made from (co)polymerized hydrophilic monomers or are graft (co)polymers made from one or more hydrophilic monomers on a suitable graft base, or are crosslinked cellulose ethers or crosslinked starch ethers or natural products which are swellable in aqueous liquids, for example guar derivatives. These hydrogels are known to the person skilled in the art and are described, for example, in US-4,286,082, DE-C-27 06 135, US-4,340,706, DE-C-37 13 601, DE-C-28 40 010, DE-A-43 44 548, DE-A-40 20 780, DE-A-40 15 085, DE-A-39 17 846, DE-A-38 07 289, DE-A-35 33 337, DE-A-35 03 458, DE-A-42 44 548, DE-A-42 19 607, DE-A-40 21 847, DE-A-38 31 261, DE-A-35 11 086, DE-A-31 18 172, DE-A-30 28 043, DE-A-44 18 881, EP-A-801483, EP-A-455985, EP-A-467073, EP-A-312952, EP-A-205874, EP-A-499774, DE-A-26 12 846, DE-A-40 20 780, EP-A-205674, US-5,145,906, EP-A-530438, EP-A-670073, US-4,057,521, US-4,062,817, - US-4,525,527, US-4,295,987, US-5,011,892, US-4,076,663 or US-4,931,497. The content of the abovementioned patents is expressly incorporated into the present application by way of reference.
Examples of hydrophilic monomers suitable for preparing these hydrophilic, highly swellable hydrogels are polymerizable acids, such as acrylic acid, methacrylic acid, vinylsulfonic acid, vinylphosphonic acid, malefic acid including its anhydride, fumaric acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanephosphonic acid, and also the associated amides, hydroxyalkyl esters and amino-group- or ammonium-group-containing esters and amides, and also water-soluble N-vinylamides and diallyldimethylammonium chloride.
Preferred hydrophilic monomers are compounds of the formula I
\ /
C C
/ \
where R' is hydrogen, methyl or ethyl, RZ is the -COOR4 group, the sulfonyl group, the phosphonyl group, the phosphonyl group esterified with (C,-C4) alkanol or a group of the formula i Hs ~CwNyCH2R5 H CHs R3 is hydrogen, methyl, ethyl or the carboxyl group, R4 is hydrogen, amino or hydroxy-(C,-C4)-alkyl, and RS is the sulfonyl group, the phosphonyl group or the carboxyl group.
Examples of (C,-C,) alkanols are methanol, ethanol, n-propanol and n-butanol.
Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid.
Suitable graft bases for hydrophilic hydrogels obtainable by graft 5 copolymerization of olefinically unsaturated acids may be of natural or synthetic origin. Examples of these are starches, cellulose and cellulose derivatives, and also other polysaccharides and oligosaccharides, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, and also hydrophilic polyesters.
Examples of suitable polyalkylene oxides have the formula X
I
Rs-O-(CHz CH-O)~ R' where R6 and R', independently of one another, are hydrogen, alkyl, alkenyl or acryl, X is hydrogen or methyl, and n is an integer from 1 to 10,000.
R6 and R' are preferably hydrogen, (C,-C4)-alkyl, (CZ Cs)-alkenyl or phenyl.
Preferred hydrogels are in particular polyacrylates, polymethacrylates and the graft polymers described in US-4,931,497, US-5,011,892 and US-5,041,496.
The hydrophilic, highly swellable hydrogels are preferably crosslinked, i.e.
they comprise compounds having at least two double bonds incorporated into the polymer network. Particular examples of suitable crosslinking agents are methylenebisacryl- and -methacrylamide, polyol esters of unsaturated mono- or polycarboxylic acids, for example diacrylates or triacrylates, such as butanediol diacrylate, ethylene glycol diacrylate and also the corresponding dimethacrylates, and also trimethylolpropane triacrylate and allyl compounds, such as allyl (meth)acrylate, triallyl cyanurate, diallyl maleate, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl phosphates, and also vinylphosphonic acid derivatives as described, for example, in EP-A-343 427.
The hydrophilic, highly swellable hydrogels are moreover particularly preferably post-crosslinked in a manner known per se in an aqueous gel phase or surface-crosslinked in the form of polymer particles from grinding and screening processes. Crosslinking agents suitable for this are compounds which contain at least two groups capable of forming covalent bonds with the carboxyl groups of the hydrophilic polymer. Examples of suitable compounds are di- and polyglycidyl compounds, such as diglycidyl phosphonate, alkoxysilyl compounds, polyaziridines, polyamines and polyamidoamines. The abovementioned compounds may also be used in mixtures with one another (see, for example, EP-A-83022, EP-A-543303 and EP-A-530438). EP-A-349935 describes in particular polyamidoamines suitable as crosslinking agents.
The hydrophilic, highly swellable hydrogels may be prepared by poly-merization processes known per se. Preference is given to polymerization in aqueous solution by the process known angel polymerization. For this, from 15 to 50% by weight of aqueous solutions of one or more hydrophilic monomers and, if desired, of a suitable graft base are polymerized in the presence of a free-radical initiator, preferably without mechanical mixing, utilizing the Trommsdorff-Norrish effect (Bios Final Rep. 363.22; Makromol.
Chem. 1, 169 (1947)).
The polymerization reaction may be carried out in a temperature range of from 0 to 150°C, preferably from 10 to 100°C, either at atmospheric pressure or at superatmospheric or subatmospheric pressure. The polymerization may also, as is usual, be carried out in an inert gas atmosphere, preferably under nitrogen.
The polymerization may be initiated by high-energy electromagnetic radiation or by the usual chemical polymerization initiators, e.g. organic peroxides, such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, or by azo compounds, such as azodiisobutyronitrile, or also by inorganic peroxy compounds, such as (NH4)2S2Og, K2S2O8 or H202, if desired combined with reducing agents, such as sodium hydrogensulfite, and iron(II) sulfate or with redox systems comprising, as reducing component, an aliphatic and aromatic sulfinic acid, such as benzenesul~nic acid and toluenesulfinic acid, or derivatives of these acids, such as Mannich adducts made from sulfinic acid, aldehydes and amino compounds, as described in DE-C-1 301 566. The qualities of the polymers can be further improved by continuing to heat the polymer gels for several hours at temperatures in the range from 50 to 130°C, preferably from 70 to 100'C.
After the novel encapsulated hydrogels have been processed together with natural or synthetic fibers, for example, to give sheeting, for example, the material which delays or prevents the absorption of water or of aqueous liquids has to be removed again so that the absorption properties are reinstated.
The present invention therefore also provides a process for preparing hydrophilic, highly swellable hydrogels from the novel encapsulated hydrogels, which comprises removing the material which delays or prevents the absorption of water or of aqueous liquids.
The material which delays or prevents the absorption of water or of aqueous liquids can be removed, for example, by the action of energy.
Depending on the type of material, mechanical, thermal or chemical processes or high-energy radiation may be used.
Mechanical break-up of the encapsulation can be brought about, for example, by applying pressure in presses or calenders or the like, or by exposure to ultrasound. If the encapsulating materials can be melted, the introduction of heat can be used to make the hydrogels swellable. Certain encapsulating materials can also be released by exposure to suitable solvents.
Examples Test method Vortex test: 50 ml of 0.9% strength NaCI solution are placed in a 100 ml glass beaker. With stirring at 600 rpm by a magnetic stirrer, 2.00 g of test substance are added rapidly in such a way that there is no agglomeration.
The time (in seconds) measured is that required for the liquid vortex produced by stirring to close up and give a flat surface.
Test-tube swelling test: Swelling to a height of 5 cm after covering 0.5 g of the test substance with 0.9% strength sodium chloride solution in a 5 ml Fiolax test tube.
Lock-up time test: 1 g of SAP (t 0.01 g) is weighed into an aluminum dish (diameter 57 mm). 30 ml of 0.9% strength NaCI solution are measured out in a measuring cylinder and carefully poured onto the SAP distributed in the aluminum dish. A stopwatch is used to measure the time from first contact of the NaCI solution with the SAP to complete absorption of this solution. The absorption time required is recorded in seconds. Three measurements are carried out and a mean value is derived.
Example 1:
The experiment was carried out in a laboratory fluidized-bed apparatus (STREA-1 supplied by AEROMATIC-FIELDER AG) ("Coater" type). The Wurster (batch) process was used, and liquid conveyed by a hose pump was sprayed from below via a two-fluid die onto the bed material. The carrier gas used was air, which was preheated inside the apparatus before it entered the fluidized bed by a heating spiral to not more than 100°C. The gas used for spraying was also air, introduced via a separate feed without preheating. 200 g of commercially available superabsorbent (SANWE'T~ IM
7015 from CLARIANT GmbH) were charged to the fluidized-bed apparatus and preheated to about 75°C by a stream of hot air. The perforated base used (through which the carrier gas flows) had a flow resistance of 6%. A
0.8 mm two-fluid nozzle was used. Using a carrier gas flow of about 140 m3/h, an inlet temperature of from 96 to 99°C (discharge temperature from 75 to 85°C) and an atomizer pressure of 1.0 bar, spray application of 600 g of an aqueous polymer dispersion based on styrene-butadiene (STYROFAN~ LD 716 from BASF AG), diluted to 5%, was completed in 3 hours. The weight increase, based on the bed material initially charged and recorded after cooling, was 25 g, corresponding to a yield of 96% and a proportion of 15% of coating polymer in the totality of the product. The residual moisture in the product was< 1 %, compared with about 3% before coating, and the size profile was significantly shifted, compared with the starting material before encapsulation, toward a larger range. The swelling rate (vortex test) of 77 s recorded was significantly greater than that for the starting material (41 s). After the product had been ground, the swelling time measured in the vortex test was 49 s, and thus the value for the starting material had virtually been regained.
Example 2:
200 g of superabsorbent (SANWEI'~ IM 7015 from CLARIANT GmbH) were placed in the apparatus described in Example 1 and, using the same conditions and the same procedure, a homogeneous mixture of 182 g of a 9.1 % strength aqueous polyvinyl alcohol solution (1:1 mixture of MOWIOL~ 4-88 and MOWIOL~ 26-88 from Clariant GmbH), 4.5 g of a 76%
strength aqueous melamine-formaldehyde condensation resin (MADURIT~' SMW 818 from VIANOVA RESINS GmbH) and 50 g of water were applied by spraying during the course of 2 hours. This coated product, too, had a size profile which was significantly shifted to a coarser range compared with that of the starting material. The swelling rate measured in the vortex test was 93 s, but 51 s again after the product had been ground. Break-up of the encapsulation was also achieved by using a 5 kg steel cylinder with 100 cm2 load area to apply load for 30 seconds to the granules in the form of a 1 mm layer between the smooth sides of two moist cellulose webs (Tartas Biofluff cellulose C 92, thickness 0.9 mm, moisture level about 75%). The following values were found in the test-tube swelling test: non-encapsulated starting material = 26 s, encapsulated product = 57 s, ground product = 29 s and product subjected to breaking-up under pressure =
37 s.
Example 3:
The experiment was carried out in a Lodige mixer (M5R type). A liquid conveyed by a hose pump was sprayed from above into the interior of the mixer via a two-fluid nozzle onto the preheated (from about 80 to 150°C, 10 preferably 140°C) base material to be encapsulated, using a batch process. Nitrogen was used for spraying. 1000 g of base polymer (SANWET'~ IM 3000 P from Clariant GmbH) were placed in the Lodige mixer and heated. Using an atomizer pressure of 0.5 bar, a homogeneous mixture of 800 g of 75% strength aqueous melamine-formaldehyde condensation resin (MADURII'~ SMW 818 from VIANOVA RESINS GmbH) and 200 g of isopropanol were sprayed on during the course of about 8 h, followed by post-annealing for 1 h. The residual moisture of the product was <1 %, compared with about 4.5% before coating. The proportion of coating polymer in the totality of the product was about 38%. Compared with the starting material, the product obtained shows a marked grain size shift toward a coarser range (starting material: < 300 Nm = 100%, after coating <300 Nm = about 5%). Compared with the starting material (54 s), a significantly slower swelling rate of 5 min 55 s was recorded in the vortex text.
Example 4:
1000 g of base polymer (SANWEl'~ IM 3000 P from Clariant GmbH) were placed in the apparatus described in Example 1 with 200 g of hydrogenated castor oil (CUTINA~ HR from Henkel AG), and mixed. The contents of the mixer are heated to 100°C, and then cooled again to room temperature. The proportion of coating wax in the totality of the product is 'about 18%. This coated product, too, showed a marked shift of grain size toward a coarser range, when compared with the starting material. The swelling rate measured in the vortex test was 2 min 06 s. The Lock-up time test likewise measured a swelling rate which, at 195 s, was significantly slower than that of the starting material (94 s).
Examples of removal of the material which delays or prevents the absorption of water or of aqueous liquids:
Example 5:
Mechanical break-up of the encapsulation by application of pressure in a press The coated polymer obtained in Example 1 is placed under load for 6 s, at pressures of 100 and 200 bar, between the smooth sides of two cellulose webs (Tartas Biofluff cellulose C92, thickness 0.9 mm, moisture level about 75%) in a press (normally used for preparing KBr pressings for IR
spectroscopy) made by PAUL WEBER, Stuttgart, Germany.
Corresponding blank values are obtained for the starting material (SANWE'f~ IM 3000 P from Clariant GmbH). A vortex test was carried out.
Vortex test: Pressure applied without load 100 bar 200 bar Startin material 54 s 50 s 47 s Coated of mer 355 s 98 s 54 s Example 6:
Break-up of the encapsulation by exposure to ultrasound In each case, 2 g of the polymer obtained in Example 1 are treated in a 150 ml glass beaker in a water bath for 1 min and 5 min, using Sonoplus HD 200 high-performance ultrasound disintegrator equipment.
Corresponding blind values are measured on the starting material (SANWE'T~ IM 3000 P from Clariant GmbH). The swelling rates were determined in a vortex test.
Vortex test:
Ultrasound treatment no treatment 1 min 5 min Startin material54 s 55 s 53 s Coated of mer 355 s 245 s 75 s Example 7:
Break-up of the encapsulation by introducing heat A thin layer (with no mutually superpositioned particles) of the polymer obtained from Example 2, on a ~Iter paper resting on a Buchner funnel with suction flask (with suction applied) is heated with RO 4300 infrared equipment. The wax layer which had been applied melts and is removed via the filter paper and the suction applied. Corresponding blank values are measured for the starting material (SANWET~ IM 3000 P from Clariant GmbH). A vortex test was carried out on the coated polymer after heat treatment and cooling. Blank values were obtained in the same way.
Vortex test:
Heat treatment no treatment 5 min 10 min Startin material54 s 53 s 50 s Coated of mer 126 s 88 s 74 s
Preferred hydrophilic monomers are compounds of the formula I
\ /
C C
/ \
where R' is hydrogen, methyl or ethyl, RZ is the -COOR4 group, the sulfonyl group, the phosphonyl group, the phosphonyl group esterified with (C,-C4) alkanol or a group of the formula i Hs ~CwNyCH2R5 H CHs R3 is hydrogen, methyl, ethyl or the carboxyl group, R4 is hydrogen, amino or hydroxy-(C,-C4)-alkyl, and RS is the sulfonyl group, the phosphonyl group or the carboxyl group.
Examples of (C,-C,) alkanols are methanol, ethanol, n-propanol and n-butanol.
Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid.
Suitable graft bases for hydrophilic hydrogels obtainable by graft 5 copolymerization of olefinically unsaturated acids may be of natural or synthetic origin. Examples of these are starches, cellulose and cellulose derivatives, and also other polysaccharides and oligosaccharides, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, and also hydrophilic polyesters.
Examples of suitable polyalkylene oxides have the formula X
I
Rs-O-(CHz CH-O)~ R' where R6 and R', independently of one another, are hydrogen, alkyl, alkenyl or acryl, X is hydrogen or methyl, and n is an integer from 1 to 10,000.
R6 and R' are preferably hydrogen, (C,-C4)-alkyl, (CZ Cs)-alkenyl or phenyl.
Preferred hydrogels are in particular polyacrylates, polymethacrylates and the graft polymers described in US-4,931,497, US-5,011,892 and US-5,041,496.
The hydrophilic, highly swellable hydrogels are preferably crosslinked, i.e.
they comprise compounds having at least two double bonds incorporated into the polymer network. Particular examples of suitable crosslinking agents are methylenebisacryl- and -methacrylamide, polyol esters of unsaturated mono- or polycarboxylic acids, for example diacrylates or triacrylates, such as butanediol diacrylate, ethylene glycol diacrylate and also the corresponding dimethacrylates, and also trimethylolpropane triacrylate and allyl compounds, such as allyl (meth)acrylate, triallyl cyanurate, diallyl maleate, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl phosphates, and also vinylphosphonic acid derivatives as described, for example, in EP-A-343 427.
The hydrophilic, highly swellable hydrogels are moreover particularly preferably post-crosslinked in a manner known per se in an aqueous gel phase or surface-crosslinked in the form of polymer particles from grinding and screening processes. Crosslinking agents suitable for this are compounds which contain at least two groups capable of forming covalent bonds with the carboxyl groups of the hydrophilic polymer. Examples of suitable compounds are di- and polyglycidyl compounds, such as diglycidyl phosphonate, alkoxysilyl compounds, polyaziridines, polyamines and polyamidoamines. The abovementioned compounds may also be used in mixtures with one another (see, for example, EP-A-83022, EP-A-543303 and EP-A-530438). EP-A-349935 describes in particular polyamidoamines suitable as crosslinking agents.
The hydrophilic, highly swellable hydrogels may be prepared by poly-merization processes known per se. Preference is given to polymerization in aqueous solution by the process known angel polymerization. For this, from 15 to 50% by weight of aqueous solutions of one or more hydrophilic monomers and, if desired, of a suitable graft base are polymerized in the presence of a free-radical initiator, preferably without mechanical mixing, utilizing the Trommsdorff-Norrish effect (Bios Final Rep. 363.22; Makromol.
Chem. 1, 169 (1947)).
The polymerization reaction may be carried out in a temperature range of from 0 to 150°C, preferably from 10 to 100°C, either at atmospheric pressure or at superatmospheric or subatmospheric pressure. The polymerization may also, as is usual, be carried out in an inert gas atmosphere, preferably under nitrogen.
The polymerization may be initiated by high-energy electromagnetic radiation or by the usual chemical polymerization initiators, e.g. organic peroxides, such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, or by azo compounds, such as azodiisobutyronitrile, or also by inorganic peroxy compounds, such as (NH4)2S2Og, K2S2O8 or H202, if desired combined with reducing agents, such as sodium hydrogensulfite, and iron(II) sulfate or with redox systems comprising, as reducing component, an aliphatic and aromatic sulfinic acid, such as benzenesul~nic acid and toluenesulfinic acid, or derivatives of these acids, such as Mannich adducts made from sulfinic acid, aldehydes and amino compounds, as described in DE-C-1 301 566. The qualities of the polymers can be further improved by continuing to heat the polymer gels for several hours at temperatures in the range from 50 to 130°C, preferably from 70 to 100'C.
After the novel encapsulated hydrogels have been processed together with natural or synthetic fibers, for example, to give sheeting, for example, the material which delays or prevents the absorption of water or of aqueous liquids has to be removed again so that the absorption properties are reinstated.
The present invention therefore also provides a process for preparing hydrophilic, highly swellable hydrogels from the novel encapsulated hydrogels, which comprises removing the material which delays or prevents the absorption of water or of aqueous liquids.
The material which delays or prevents the absorption of water or of aqueous liquids can be removed, for example, by the action of energy.
Depending on the type of material, mechanical, thermal or chemical processes or high-energy radiation may be used.
Mechanical break-up of the encapsulation can be brought about, for example, by applying pressure in presses or calenders or the like, or by exposure to ultrasound. If the encapsulating materials can be melted, the introduction of heat can be used to make the hydrogels swellable. Certain encapsulating materials can also be released by exposure to suitable solvents.
Examples Test method Vortex test: 50 ml of 0.9% strength NaCI solution are placed in a 100 ml glass beaker. With stirring at 600 rpm by a magnetic stirrer, 2.00 g of test substance are added rapidly in such a way that there is no agglomeration.
The time (in seconds) measured is that required for the liquid vortex produced by stirring to close up and give a flat surface.
Test-tube swelling test: Swelling to a height of 5 cm after covering 0.5 g of the test substance with 0.9% strength sodium chloride solution in a 5 ml Fiolax test tube.
Lock-up time test: 1 g of SAP (t 0.01 g) is weighed into an aluminum dish (diameter 57 mm). 30 ml of 0.9% strength NaCI solution are measured out in a measuring cylinder and carefully poured onto the SAP distributed in the aluminum dish. A stopwatch is used to measure the time from first contact of the NaCI solution with the SAP to complete absorption of this solution. The absorption time required is recorded in seconds. Three measurements are carried out and a mean value is derived.
Example 1:
The experiment was carried out in a laboratory fluidized-bed apparatus (STREA-1 supplied by AEROMATIC-FIELDER AG) ("Coater" type). The Wurster (batch) process was used, and liquid conveyed by a hose pump was sprayed from below via a two-fluid die onto the bed material. The carrier gas used was air, which was preheated inside the apparatus before it entered the fluidized bed by a heating spiral to not more than 100°C. The gas used for spraying was also air, introduced via a separate feed without preheating. 200 g of commercially available superabsorbent (SANWE'T~ IM
7015 from CLARIANT GmbH) were charged to the fluidized-bed apparatus and preheated to about 75°C by a stream of hot air. The perforated base used (through which the carrier gas flows) had a flow resistance of 6%. A
0.8 mm two-fluid nozzle was used. Using a carrier gas flow of about 140 m3/h, an inlet temperature of from 96 to 99°C (discharge temperature from 75 to 85°C) and an atomizer pressure of 1.0 bar, spray application of 600 g of an aqueous polymer dispersion based on styrene-butadiene (STYROFAN~ LD 716 from BASF AG), diluted to 5%, was completed in 3 hours. The weight increase, based on the bed material initially charged and recorded after cooling, was 25 g, corresponding to a yield of 96% and a proportion of 15% of coating polymer in the totality of the product. The residual moisture in the product was< 1 %, compared with about 3% before coating, and the size profile was significantly shifted, compared with the starting material before encapsulation, toward a larger range. The swelling rate (vortex test) of 77 s recorded was significantly greater than that for the starting material (41 s). After the product had been ground, the swelling time measured in the vortex test was 49 s, and thus the value for the starting material had virtually been regained.
Example 2:
200 g of superabsorbent (SANWEI'~ IM 7015 from CLARIANT GmbH) were placed in the apparatus described in Example 1 and, using the same conditions and the same procedure, a homogeneous mixture of 182 g of a 9.1 % strength aqueous polyvinyl alcohol solution (1:1 mixture of MOWIOL~ 4-88 and MOWIOL~ 26-88 from Clariant GmbH), 4.5 g of a 76%
strength aqueous melamine-formaldehyde condensation resin (MADURIT~' SMW 818 from VIANOVA RESINS GmbH) and 50 g of water were applied by spraying during the course of 2 hours. This coated product, too, had a size profile which was significantly shifted to a coarser range compared with that of the starting material. The swelling rate measured in the vortex test was 93 s, but 51 s again after the product had been ground. Break-up of the encapsulation was also achieved by using a 5 kg steel cylinder with 100 cm2 load area to apply load for 30 seconds to the granules in the form of a 1 mm layer between the smooth sides of two moist cellulose webs (Tartas Biofluff cellulose C 92, thickness 0.9 mm, moisture level about 75%). The following values were found in the test-tube swelling test: non-encapsulated starting material = 26 s, encapsulated product = 57 s, ground product = 29 s and product subjected to breaking-up under pressure =
37 s.
Example 3:
The experiment was carried out in a Lodige mixer (M5R type). A liquid conveyed by a hose pump was sprayed from above into the interior of the mixer via a two-fluid nozzle onto the preheated (from about 80 to 150°C, 10 preferably 140°C) base material to be encapsulated, using a batch process. Nitrogen was used for spraying. 1000 g of base polymer (SANWET'~ IM 3000 P from Clariant GmbH) were placed in the Lodige mixer and heated. Using an atomizer pressure of 0.5 bar, a homogeneous mixture of 800 g of 75% strength aqueous melamine-formaldehyde condensation resin (MADURII'~ SMW 818 from VIANOVA RESINS GmbH) and 200 g of isopropanol were sprayed on during the course of about 8 h, followed by post-annealing for 1 h. The residual moisture of the product was <1 %, compared with about 4.5% before coating. The proportion of coating polymer in the totality of the product was about 38%. Compared with the starting material, the product obtained shows a marked grain size shift toward a coarser range (starting material: < 300 Nm = 100%, after coating <300 Nm = about 5%). Compared with the starting material (54 s), a significantly slower swelling rate of 5 min 55 s was recorded in the vortex text.
Example 4:
1000 g of base polymer (SANWEl'~ IM 3000 P from Clariant GmbH) were placed in the apparatus described in Example 1 with 200 g of hydrogenated castor oil (CUTINA~ HR from Henkel AG), and mixed. The contents of the mixer are heated to 100°C, and then cooled again to room temperature. The proportion of coating wax in the totality of the product is 'about 18%. This coated product, too, showed a marked shift of grain size toward a coarser range, when compared with the starting material. The swelling rate measured in the vortex test was 2 min 06 s. The Lock-up time test likewise measured a swelling rate which, at 195 s, was significantly slower than that of the starting material (94 s).
Examples of removal of the material which delays or prevents the absorption of water or of aqueous liquids:
Example 5:
Mechanical break-up of the encapsulation by application of pressure in a press The coated polymer obtained in Example 1 is placed under load for 6 s, at pressures of 100 and 200 bar, between the smooth sides of two cellulose webs (Tartas Biofluff cellulose C92, thickness 0.9 mm, moisture level about 75%) in a press (normally used for preparing KBr pressings for IR
spectroscopy) made by PAUL WEBER, Stuttgart, Germany.
Corresponding blank values are obtained for the starting material (SANWE'f~ IM 3000 P from Clariant GmbH). A vortex test was carried out.
Vortex test: Pressure applied without load 100 bar 200 bar Startin material 54 s 50 s 47 s Coated of mer 355 s 98 s 54 s Example 6:
Break-up of the encapsulation by exposure to ultrasound In each case, 2 g of the polymer obtained in Example 1 are treated in a 150 ml glass beaker in a water bath for 1 min and 5 min, using Sonoplus HD 200 high-performance ultrasound disintegrator equipment.
Corresponding blind values are measured on the starting material (SANWE'T~ IM 3000 P from Clariant GmbH). The swelling rates were determined in a vortex test.
Vortex test:
Ultrasound treatment no treatment 1 min 5 min Startin material54 s 55 s 53 s Coated of mer 355 s 245 s 75 s Example 7:
Break-up of the encapsulation by introducing heat A thin layer (with no mutually superpositioned particles) of the polymer obtained from Example 2, on a ~Iter paper resting on a Buchner funnel with suction flask (with suction applied) is heated with RO 4300 infrared equipment. The wax layer which had been applied melts and is removed via the filter paper and the suction applied. Corresponding blank values are measured for the starting material (SANWET~ IM 3000 P from Clariant GmbH). A vortex test was carried out on the coated polymer after heat treatment and cooling. Blank values were obtained in the same way.
Vortex test:
Heat treatment no treatment 5 min 10 min Startin material54 s 53 s 50 s Coated of mer 126 s 88 s 74 s
Claims (7)
1. An encapsulated hydrogel, encompassing a hydrophilic, highly swellable hydrogel which is reversibly coated with a material which delays or prevents the absorption of water and of aqueous liquids.
2. An encapsulated hydrogel as claimed in claim 1, wherein the material which delays or prevents the absorption of water or of aqueous liquids is a homo- and/or copolymer of olefinically unsaturated compounds, preferably ethylene, propylene, styrene, esters of olefinically unsaturated acids, esters of olefinically unsaturated alcohols, an amino resin, in particular urea or melamine-aldehyde resin, a phenolic resin, a polyepoxide, a polyester compound, a polyacetal, a polycarbonate, a polyamide, a polyurethane, a silicone resin or a ketone-aldehyde resin or alkyd resin.
3. An encapsulated hydrogel as claimed in claim 1 and/or 2, wherein the hydrophilic, highly swellable hydrogel is a polymer made from (co)polymerized hydrophilic monomers, or is a graft (co)polymer made from one or more hydrophilic monomers on a suitable graft base, or is a crosslinked cellulose or starch ether or a natural product which is swellable in aqueous liquids, in particular a guar derivative.
4. An encapsulated hydrogel as claimed in claim 3, wherein the hydrophilic monomers are compounds of the formula I
where 1a R1 is hydrogen, methyl or ethyl, R2 is the -COOR4 group, the sulfonyl group, the phosphonyl group, the phosphonyl group esterified with (C1-C4) alkanol or a group of the formula R3 is hydrogen, methyl, ethyl or the carboxyl group, R4 is hydrogen, amino or hydroxy-(C1-C4)-alkyl, and R5 is the sulfonyl group, the phosphonyl group or the carboxyl group.
where 1a R1 is hydrogen, methyl or ethyl, R2 is the -COOR4 group, the sulfonyl group, the phosphonyl group, the phosphonyl group esterified with (C1-C4) alkanol or a group of the formula R3 is hydrogen, methyl, ethyl or the carboxyl group, R4 is hydrogen, amino or hydroxy-(C1-C4)-alkyl, and R5 is the sulfonyl group, the phosphonyl group or the carboxyl group.
5. An encapsulated hydrogel as claimed in claim 3 and/or 4, wherein the hydrophilic monomers are acrylic acid or methacrylic acid.
6. The use of the encapsulated hydrogels as claimed in any of claims 1 to 5 in processing with natural or synthetic fibers in aqueous processes to give sheeting and reinstating the absorption properties of the hydrogels by removing the material which delays or prevents the absorption of water or of aqueous liquids.
7. The use as claimed in claim 6, wherein the removal of the material which delays or prevents the absorption of water or of aqueous liquids is brought about by the action of energy in the form of mechanical, thermal or chemical processes, or in the form of high-energy radiation.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19801933.5 | 1998-01-20 | ||
| DE19801933A DE19801933A1 (en) | 1998-01-20 | 1998-01-20 | Encapsulated hydrogel for use in sanitary products |
| PCT/EP1999/000337 WO1999037395A1 (en) | 1998-01-20 | 1999-01-20 | Encapsulated hydrogels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2316342A1 true CA2316342A1 (en) | 1999-07-29 |
Family
ID=7855120
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002316342A Abandoned CA2316342A1 (en) | 1998-01-20 | 1999-01-20 | Encapsulated hydrogels |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1049535B1 (en) |
| JP (1) | JP4970650B2 (en) |
| CA (1) | CA2316342A1 (en) |
| DE (2) | DE19801933A1 (en) |
| WO (1) | WO1999037395A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8247640B2 (en) | 2000-10-25 | 2012-08-21 | Evonik Stockhausen Gmbh | Highly swellable absorption medium with reduced caking tendency |
| US8287999B2 (en) | 2005-02-04 | 2012-10-16 | The Procter & Gamble Company | Absorbent structure with improved water-absorbing material comprising polyurethane, coalescing aid and antioxidant |
| EP4074756A4 (en) * | 2019-12-13 | 2023-12-13 | Sumitomo Seika Chemicals Co., Ltd. | Coated resin particles and method for producing coated resin particles |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10052966A1 (en) * | 2000-10-25 | 2002-05-02 | Stockhausen Chem Fab Gmbh | Highly-swellable absorption material with reduced caking tendency comprises an acid group-containing natural or synthetic polymer coated with a nitrogen-containing nonionic surfactant |
| AU2002318159A1 (en) | 2001-06-29 | 2003-03-03 | The Regents Of The University Of California | Biodegradable/bioactive nucleus pulposus implant and method for treating degenerated intervertebral discs |
| KR101825607B1 (en) | 2010-02-18 | 2018-02-05 | 다우 코닝 코포레이션 | Surface-modified hydrogels and hydrogel microparticles |
| CN102060959B (en) * | 2010-12-03 | 2012-07-04 | 中国科学院长春应用化学研究所 | Method for preparing polyacrylic acid water-retaining agent |
| WO2015200444A1 (en) | 2014-06-24 | 2015-12-30 | Saudi Arabian Oil Company | Encapsulation of an acid precursor for oil field applications |
| KR20240009958A (en) * | 2021-05-18 | 2024-01-23 | 스미토모 세이카 가부시키가이샤 | Coated resin particles and method for producing coated resin particles |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01261250A (en) * | 1988-04-08 | 1989-10-18 | Tsuruga Cement Kk | Admixture for cement concrete and mortar produced by using highly water-absorbing resin |
| JPH0280385A (en) * | 1988-09-14 | 1990-03-20 | Tsuruga Cement Kk | Admixture for cement concrete and mortar using high-water-absorption resin |
| JP2579814B2 (en) * | 1989-03-16 | 1997-02-12 | 三洋化成工業株式会社 | Water absorbing agent and method for producing the same |
| DE4426008A1 (en) * | 1994-07-22 | 1996-01-25 | Cassella Ag | Hydrophilic, highly-swellable hydrogel coated with non-reactive, water-insol. polymer film |
| JPH0931203A (en) * | 1995-07-24 | 1997-02-04 | Hoechst Ag | Hydrophilic highly swellable hydrogel |
-
1998
- 1998-01-20 DE DE19801933A patent/DE19801933A1/en not_active Withdrawn
-
1999
- 1999-01-20 EP EP99932440A patent/EP1049535B1/en not_active Expired - Lifetime
- 1999-01-20 CA CA002316342A patent/CA2316342A1/en not_active Abandoned
- 1999-01-20 WO PCT/EP1999/000337 patent/WO1999037395A1/en active IP Right Grant
- 1999-01-20 DE DE59902461T patent/DE59902461D1/en not_active Expired - Lifetime
- 1999-01-20 JP JP2000528364A patent/JP4970650B2/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8247640B2 (en) | 2000-10-25 | 2012-08-21 | Evonik Stockhausen Gmbh | Highly swellable absorption medium with reduced caking tendency |
| US8287999B2 (en) | 2005-02-04 | 2012-10-16 | The Procter & Gamble Company | Absorbent structure with improved water-absorbing material comprising polyurethane, coalescing aid and antioxidant |
| EP4074756A4 (en) * | 2019-12-13 | 2023-12-13 | Sumitomo Seika Chemicals Co., Ltd. | Coated resin particles and method for producing coated resin particles |
| EP4074755A4 (en) * | 2019-12-13 | 2024-01-24 | Sumitomo Seika Chemicals | Absorbent resin particles and absorbent |
Also Published As
| Publication number | Publication date |
|---|---|
| DE19801933A1 (en) | 1999-07-22 |
| EP1049535B1 (en) | 2002-08-28 |
| JP4970650B2 (en) | 2012-07-11 |
| JP2002501088A (en) | 2002-01-15 |
| WO1999037395A1 (en) | 1999-07-29 |
| EP1049535A1 (en) | 2000-11-08 |
| DE59902461D1 (en) | 2002-10-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6565768B1 (en) | Method for producing water-swellable hydorphilic polymers, said polymers and use thereof | |
| US6602950B1 (en) | Hydrophilic hydrogels with a high swelling capacity and method for producing and using them | |
| Kiatkamjornwong | Superabsorbent polymers and superabsorbent polymer composites | |
| CA2017570C (en) | Porous structure of an absorbent polymer | |
| CA2171085C (en) | Powder-form polymers capable of absorbing aqueous liquids, method of preparing them and their use as absorbents | |
| US5973014A (en) | Process for the preparation of porous, hydrophilic, highly swellable hydrogels | |
| EP0516925B1 (en) | Wrinkled absorbent particles of high effective surface area having fast absorption rate | |
| TWI290155B (en) | Hygiene article comprising an absorbent polymer | |
| US5164459A (en) | Method for treating the surface of an absorbent resin | |
| MXPA01007454A (en) | HIGHLY DILATABLE HYDROGELS, HYDROPHILIC, RETICULATED, METHOD FOR PRODUCTION AND USE | |
| JP2002121291A (en) | Water-absorbing resin powder and method for producing the same | |
| JP2877255B2 (en) | Manufacturing method of water absorbent resin with excellent durability | |
| KR20030068198A (en) | Hydrogels Coated with Steric or Electrostatic Spacers | |
| CZ20013128A3 (en) | Pulverized crosslinked absorption polymers, process of their preparation and use | |
| CN101094696A (en) | Superabsorbent polymer particles having a reduced amount of fine-sized particles, and methods of manufacturing the same | |
| JP2002504566A (en) | Postcrosslinking of hydrogels using 2-oxazolidinone | |
| EP1196204A1 (en) | Superabsorbent polymers having delayed water absorption characteristics | |
| JPH05339381A (en) | Production of water-absorptive resin and water absorbent | |
| CA2316342A1 (en) | Encapsulated hydrogels | |
| JPH07224204A (en) | Production of water-absorbing resin | |
| WO2006134085A1 (en) | Hydrogel-forming polymers with increased permeability and high absorption capacity | |
| JPS6155202A (en) | Paper and cloth article provided with high water absorbability | |
| JPH04227710A (en) | Manufacture of finely divided, water-swelling polysaccharide graft polymer | |
| MXPA00006632A (en) | Encapsulated hydrogels | |
| JP2002138147A (en) | Method of producing water-swellable crosslinked polymer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |