CA2025035A1 - Cellular cellulosic material with improved water retention and preparation of the latter - Google Patents
Cellular cellulosic material with improved water retention and preparation of the latterInfo
- Publication number
- CA2025035A1 CA2025035A1 CA002025035A CA2025035A CA2025035A1 CA 2025035 A1 CA2025035 A1 CA 2025035A1 CA 002025035 A CA002025035 A CA 002025035A CA 2025035 A CA2025035 A CA 2025035A CA 2025035 A1 CA2025035 A1 CA 2025035A1
- Authority
- CA
- Canada
- Prior art keywords
- particles
- superabsorbent polymer
- cellulose
- cellular
- viscose
- 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
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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
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
-
- 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
- A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
- A61L15/28—Polysaccharides or their derivatives
-
- 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
- A61L15/425—Porous materials, e.g. foams or sponges
-
- 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
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/08—Cellulose derivatives
- C08J2301/22—Cellulose xanthate
- C08J2301/24—Viscose
Landscapes
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- General Health & Medical Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- Veterinary Medicine (AREA)
- Public Health (AREA)
- Hematology (AREA)
- Epidemiology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Dispersion Chemistry (AREA)
- Medicinal Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Polymers & Plastics (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE The subject of the present invention is a cellular cellulosic Material, with improved water retention, characterized in that it contains particles of superabsorbent polymer, trapped in the cellulose network. It also relates to a process for the preparation of such a material.
Description
The subject of the present invention is a cellular cellulosic material -or sponge- with improved retention of water (and, more generally, of aqueous liquids). It also relates to a process for the preparation of such a material.
S The applicant has deYeloped a new product of the sponge type which, in addition to the fact that it possesses an improved capacity for water retention, remains moist and supple for a longer time than a sponge of t~e prior art. To the touch and in appearance it is also improved.
In fact, in the dry state, a sponge is rough and retracts, whereas when it is moist it has a soft and pleasant feelO This change of state is seen particularly in thin sponges which become warped when dry.
In order to solve this problem -maintain a sponge humid and supple, particularly when it is being stored or on sale- it has been suggested, according to the prior art, that magnesium chloride and glycols be incorporated within the said sponge. This solution does not prove to be completely satisfactory. The said magnesium chloride and the said glycols are leached out as soon as the sponges are used and then no longer play their role in water retention and as plasticizers of the cellulose.
The applicant now suggests the introduction of particles of a superabsorbent polymer in the buLk of the said cellu1ar cellulosic material~ The specifications for the said particles will be provided below.
Particles of a superabsorbent polymer are already used advantageously in disposable products such as diapers.
Their introduction, according to the invention, into the area of sponges -within the cellulose network- is not an obvious step.
In fact, the simple incorporation of particles of a superabsorbent polymer during the manufacturing process for sponges or cellular cellulosic materials -cal~ed the viscose process without protection of the said particles invariably leads to degradation of the latter by hydrolysis and/or compression and, consequently 9 to a considerable loss of thei} water-retaining capacity.
The addition of the said particles after manufacture of the said cellular cellulosic material does not enable them to be inserted into the interior of the said material and be retained there mechanically. Furthermore, the presence of the said particles at the surface of the said material or sponge in the swollen state after absorption of water confers on it a slimy, sticky feel hardly appropriaee to its use, particularly in the area of household cleaning.
Absorbent articles obtained by the viscose process and containing particles of a superabsorbent polymer have been described in the patent application EP-A-0 293 ~08. The said particles are not trapped in the cellulose network at the interior of these articles.
The said articles are usually laminated materials; thus5 the particles of superabsorbent polymer are found betweell two layers of compressed cellulosic material.
The applicant now suggests a method for the incorporation of particles of superabsorbent pol~mer into the structure of cellular cellulosic materials without degradation and in a stable manner in order to obtain the expected results set out above.
Such materials, including the said particles in their cellulosic structure, constitute a subject of the invention; the process for their preparation constitutes another.
Thus, the subject of the present invention is a cellular cellulosic material with improved water retention, characterized in that it contains particles of a superabsorbent polymer trapped in the cellulose network.
Characteristically, the particles of superabsorbent polymer are found in the sponges of the invention, trapped in the cellulose network. They are localized in the interstices of the said cellulose.
It has been possible to produce such a currently novel structure by means of the process described below; the viscose process ~known to the person skilled in the art- in which, according to the invention, the temporarily protected particles of superabsorbent polymer are introduced into the viscose before the acidic regeneration of ehe cellulose.
The particles of su~erabsorbent polymer assume the function of retainers of water or any other liquid. They are particles of superabsorbent polymers (usually known under ~he abbreviation S.A.P.:
Super Absorbent Polymer~.
These polymers may be of natural or synthetic origin and, for the purposes of the invention, are advantageously insoluble in water.
For reasons of convenience r we will sometimes use the abbreviation S.A.P. in the continuation of the presen~ description.
These polymers - S.A.P.- when placed in contact with water form a physical or chemical gel, also called hydrogel, capable of absorbing considerable amounts of water in its macromolecular network.
Superabsorbent polymers (S.A.P.) of natural origin are for example polymers, the macromolecular network of which is of the polysaccharide type such as agar--agar, gelose, alginate, carboxy-methylcellulose, such as is described in particular in the patent US-A-3 58~ 364, hydroxyethylce]lulose, methylcelllllose, gelled cellulose triacetate as is described in particular in the patents US-A-l 693 8~0 and US-A-3 ~346 404, polyacrylonitrile-grafted starch as is described in particular in the patents US-A-3 93~ 099 and US-A-3 661 815 and acrylic acid-grafted starch such as is described in the patent FR-A-2 305 452.
Superabsorbent polymerc (S.A.P.) of synthetic origin are polymers, for example, the macromolecular network of which is ~ormed by acrylic polymers; hydroxyethyl methacrylate poLymers, cross-linked polyvinyl alcohol; polyacrylamide; partially hydrolysed poly~inyl acetate; hydroxyethyl acrylate; mono-acrylate of diethylene-glycol;
monomethacrylate of diethylene-glycol; 2-hydroxypropyl acrylate; 2-hydroxypropyl methacrylate; 3-hydroxypropyl acrylate; 3-hydroxypropyl methacrylate; monomethacrylate of dipropylene-glycol; vinylpyrrolidone;
acrylamide; methacrylamide; N-propylacrylamide; N-isopropyl-methacrylamide; N-methylacrylamide; N-2-hydroxyethylmethacrylamide;
hydrogels of polyurethane, composed of lightly cross-linked polymers of prepolymers terminated by an isocyanate which are the products of reaction of a poly(alkylenoxy)polyol with an organic diisocyanate lightly cross-]inked with water or an organic polyamine~ as described in the patent US-A-3 939 105; copolymers of acrylate monomers with ethylenic unsaturation and hydroxyalkyl methacrylates and acrylates and methacrylates of alkoxyalkylene-glycols, as described in the patent US-A-4 038 264 as well as other superabsorbent polymers (S.A.P.) known to the person skilled in the art.
The superabsorbent polymers ~S.A.P.~ of synthetic origin and insoluble in water are preferred because they are thermally more stable and les~s susceptible to degradation by the action of microorganisms.
The superabsorbent polymers (S.A.P.), lnsoluble in water, are obtained by the cross-linking of macromolecules and are available in the form of flakes, powders, films, fibres and spheres or "beads"
For the purposes of the invention, particles of spherical form, possessing a diameter included between about 50 and 400 ~m, will preferably be used.
For reasons of homogeneity of the water retention effect, it is desirable that the said particles are uniformly distributed and particles of S.A.P. possessing a diameter included between 50 and 200 ~m will advantageously be used.
In particular, products called "beads", produced by polymeri~ation in reverse suspension, will be used.
At present, such products are marketed in EUROPE by the HOECHST (ref. PL ~2'i5) 7 BASF ~Luquasorb HC 9797) and NORSOLOR (X 5 TS) companies.
In order l:o obtain the desired result, the cellular cellulosic materials according to the invention usually contain about 1 to 5% by weight of particles of S.A.P. with respect to the weight of dry cellulose. That they may contain a larger amount, up to 10%
or more, is in no way excluded. It will obviously be advisable to check thAt the amounts incorporated do not or not excessively impair the properties of the flnished product: feel, appearance, mechanical behaviour, According to a variant of the invention, the cellular cellulosic material is line~ on at least one of its faces with another material. It may be any type of material compatible with the cellular cellulosic material and the introduction of which presents any interest in the field of application of the said celLular cellulosic material.
As an illustration in no way limiting, mention should be made of the introduction of an expanded latex foam, cross-linked in particular like the one constituting the ~opping face of the product described in the patent application EP ~8 401 930.8 of the applicant, published under the number 0 335 050.
It has been observed tha~ the introduction of such a synthetic latex foam also improves the water retaining power of the cellular cellulosic material to which the foam is attached. The kinetics of the evaporation of water are found to be diminished without impairment of any of the properties of the sponge-type product possessing at least one mopping face made of synthetic latex.
Advantageously, such a composite material also contains particles of a superabsorbent polymer between the said cellular cellulosic material and the said other material.
Thus, at the interior of this composite material, particles of a superabsorbent polymer are encountered at the interface cellular cellulosic material/other material and in the bulk of the said cellular cellulosic material.
As specified above, the cellular cellulosic materials of the invention owe their attractive properties to ~he fact that they contain non-degraded particles of S.A.P.within their cellulose network.
The method of incorporation of the said particles within the said materials thus constitutes a key element of the present invention. This incorporation takes place during the prepara~ion of the said material by the viscose process, known to the person skilled in the art.
This process for the production of cellular cellulosic materials is summarized below.
Wood pulp is used as starting material. It is dissolved by means of ~he viscose process through the intermediary of the xanthate derivative with addition of an expanding agent and fibres.
The pulp obtained may ~e coated, ior example, on either side of a grid. This coating step is followed by a step of acidic regeneration of the cel~ulose. The pulp may also be introduced into a mould, then regenerated in a basic medium. The cellulose thus regenerated is then rinsed~ subjected to a bleaching treatment, Ctlt up and packaged. This process may optionally include one or more steps to modify the finished product, and in particular the lining of at least one of the faces of the said product with another material.
The cellular cellulosic material of the invention is produced in the framework of the viscose process with the addition of the following steps:
- incorporation of temporarily protected particles of a superabsorbent polymer into the cellulose xanthate (viscose) before regeneration, - optionally, dusting of temporarily protected particles of a superabsorbent polymer on a~ least one face of the said cellular cellulosic material obtained with acidic or basic regeneration of the cellulose, before the lining of the said face with another material, - and deprotection of the said particles of superabsorbent polymer in the last stage of manufacture of the materialO
According to a first variant, the said particles of S.~.P.
are introduced into the cellulose xanthate (viscose) preferably after the addition of the expanding aKent and ~he fibres.
In this lat:ter case, they are incorporated either into the mixer generating the mixture of the said expanding agent 7 fibres and the xanthate derivate, or during the coating of the mixture obtained -xanthate derivative (viscose) + fibres + expanding agent- and preferably between two layers of the said mixture.
The said particles of superabsorbent polymer are thus introduced into the process, temporarily protected. Their pro~ection must be such that, on the one hand, they withstand the steps of the viscose process that they may be re~uired to undergo and/or the additional steps of modificaticn of the product obtained by the said viscose process wlthout being damaged and, on the other, they can be deprotected without impairment of the said particles, their properties and the material in which they are present.
They can be ensured such protection by encapsulation in a monolayer or bilayer membrane, consisting essentially of one (or two) mixture(s) of at least one film-forming polymer and at least one hydrophobic crystalline material.
Such a membrane is the subject of a French patent application filed in the name of the Applicant on 12 September ~989 under the No. 89 11 924.
The combination of these two types of materials -film-forming polymer(s), hydrophobic crystalline material(s)- enables a ~ight membrane to be produced under the harsh conditions of the viscooe process; a membrane which nonetheless permits the release of the encapsulated S.A.P. The degradation or removal of the said membrane for the release of the S.A.P. may be accomplished in particular by mechanical means (compression, grinding, ultrasonics), by thermal means (heating, freezing), by actinic radiation (U.V., I.R., beams of electrons, microwaves) and by chemical means (change of pH, dissolution, chemical attack). Usually, the said S.A.P. is released by fusion of the hydrophobic crystalline material(s), involved in the composition of its membrane.
Advantageously, the said membrane materials are organo--soluble compounds. Their solubility in organic solvents enables particularly efficient techniques to be employed for coating the particles of the superabsorbent polymer (S.A.P.); techniques which will be specified below.
However, the invention does not exclude the employment of compoun~s slightly or not at all organosoluble in conjunction with the use of other techniques of coa~ing or surface film formation.
The film-forming polymer entering into the composition of the membrane according to the invention may be selected from the polymers of natural origin, the polymers of synthetic origin or their mixtures.
It may be advantageously selected from the cellulose derivatives -such as the ethylcelluloses, the acetophthalates or acetobutyrates of cellulose- or their mixtures.
Similarly, it may advan1_ageously be selected from the (co)polymers of styrene, vinylidene cllloride-based (co)polymers or their mixtures~
As indicated above, it may even consist of a mixture of at least one polymer of natural origin and at least one polymer of synthetic origin.
The hydrophobic crystalline material entering into the composition of the membrane is advantageously selected from the fatty acids, the derivatives of fatty acids (amides or bistearamides of fatty acids...), the microcrystalline waxes and their mixtures. In particular, behenic acid, stearic acid, stearamide, bistearamide or erucamide may be used. Advantageously a "pure" crystalline material~
possessing a sharp melting point, is selected. Then, in order to release the encapsulated particle of superabsorbent polymer (S.A.P.) it is always possible to raise the temperature of the medium -celiular cellulosic material- in which it is found to at least and possibly above the said sharp melting point.
The two principle constituents of the membrane are advantageously used in the following proportions by weight: about 10 to 90% of film-forming polymer for about 90 to 10% of hydrophobic crystalline material.
A mixture, particularly preferred when a polymer of natural origin is used, contains about 30% of the said film-forming polymer and 70% of the hydrophobic crystalline material.
In addition to its two principle constituents, the membrane may contain additives and in particular products intended to improve its wettability and/or its hydrophobicity and/or its adhesion to the particle of superabsorbent polymer (S.A.P.). For example, mineral lamellar fillers such as mica may be added in order to improve the hydrophobicity and the watertight of the membra~e.
According to one of the preferred variants of the invention, encapsulated particles of S.A.P. may be included ln a monolayer membrane consisting essentially of a mixture of about 30% by weigh~
of polystyrene and about 70~ by weight of stearamide.
According to another preferred variant of the invention, encapsulated particles of S.A.P. are included in a bilayer membrane, r~ r l --~ r~
the first layer of which consists essentially of a mixture of about 30~ by weight of polystyrene and about 70% by weight of stearamide and the second layer of which, the layer in contact wi~h the particle of S.A.P., consists essentially o~ a mixture of about 30% by weight of ethylcellulose and about 70% by weight of behenic acid.
It is obvious that the nature of the constituents entering into the composition of the membrane and the proportions in which they occur play an important role in the efficacy and duration of the protection of the encapsulated S.A.P. Other factors also need to be taken into account, in particular the thickness of the said membrane as well as the process used for its constitution.
The person skilled in the art is in the position to determine each of the said parameters for the optimi~ation of the said protection.
As far as the thickness of the membrane is concerned, it is obvious that by increasing it,the protection of the encapsulated product (S.A.P.) is improved.
In general, an effective protection -during the preparation of the cellular cellulosic materials of the invention- of the encapsulated S.A.P. is obtained with a membrane thickness included between 10 and 50 ~m.
The thickness of the monolayer or bilayer membrane, the nature of the constituents of which has been specified above, is advantageously included between 25 and 40 ~m.
All known suitable encapsulation techniques may be employed for the encapsulation of the particles of S.A.P.
Advantageously, the said S.A.P. may be encapsulated by spraying of the materials required to constitute the successive membranes, the said materials being dissolved in a suitable solvent.
This process can be implemented in particular with organosoluble materials, dissolved in an organic solvent which does not cause the superabsorbent polymer (S.A.P.) to be encapsulated to swell. Usual solvents such as alcohols t chlorinated solvents, alkanes..~ or their mixtures may be used.
This process is advantageously implemented in order to bring about encapsulation by means of surface film formation, in particular in a fluidi~ed bed. Techniques such as those used in the ~urster, Top Spray or tangential spraying processes can be used. These processes enable successive films to be formed around the particle of super-absorbent polymer by repeated exposure of the latter close to the nozzle of the spray.
Other coating techniques, known to the person skilled in the art, enable the particles of S.A.P. for the purposes of the invention to be produced. Special mention should be made of the techniques by fusion.
The tight of the coated particles obtained may be further improved, in some cases, by a thermal or annealing treatment (at a temperature lower than the melting point of the hydrophobic crystalline material).
Such a thermal treatment can be performed after the coating with a single layer or af~er coating with a first layer and/or after coating with a second layer.
The particles thus encapsulated preserve their water retention capacity intact. It has been possible to observe that even if the transfer of the particle between the different reaction mPdia rendered the shell brittle, the protection remained efficacious.
The problem of ~he deprotection of the said particles arises when the manufacturing process of the material is complete.
Advantageously, the said deprotection is performed during a final step in the manufacture of the said material.
This deprotection, in par~icular when it consists of removing the monolayer or bilayer membrane described above, may be performed by mechanical means, by thermal means or by actinic radiation and chemical means.
The deprotection by fusion (thermal means) is preferred.
For this purpose, the product obtained may be treated thermally either in a hot air tunnel or by hot water vapour or by microwaves or high frequency... In order to obtain the desired result -removal of che membrane described above- the product is usually treated at at least 100C for several seconds.
It should be noted that advantageously the said deprotection can be produced simultaneously with the cross-linking of a material applied to at least one face of the cel lular cellulosic material. It has been seen that such ~aterials may CO1lSiSt of an e~panded latex foam.
The cel]ular cellulosic material of the invention can thus be obtained by the viscose process with the introduction of the temporarily protected particles of S.A.P~
This protection can be provided by the monolayer or bilayer membrane described above.
Other types of protection can be developed and are not excluded from the framework of the present inventionO
The applicant specifies below two preferred variants of the method for the preparation of the cellular cellulosic materials according to the invention.
According to the first variant, sponges are prepared in bulk in which particles of S.A.P. are preEerably uniformly distributed.
The viscose process is used. The encapsulated particles of S.A.P. are incorporated into the cellulose xanthate (viscose).
The product obtained undergoes an acidic regeneration. After rinsing and bleaching, the cellular cellulosic material obtained is subjected to a thermal treatmen~.
The aim of the said thermal treatment i5 to release the said particles of S.A.P. distributed in the bulk of the said material.
It is performed at at least 100C for several seconds.
According to the second Yariant, a mopping cellular cellulosic material is prepared such as that described in the application EP O 335 050 of the Applicant :
On one face of a cellular cellulosic material obtained by the viscose process as modified abo~e (by incorporation of encapsulated particles of S.A.P. in the cellulose xanthate) encapsulated particles of S.A.P. are dusted. The said face is then coated with a non-crosslinked latex foam. The entire preparation is then subjected to a thermal treatment, the parameters of which are fixed in order ensure both ~he cross linking of the said foam and the release of the encapsulated particles of S.A~P. The de~erminatlon of these parameters lies wlthin the competence of a person skilled i~ the art.
In the ~ccompanying drawings-:
FIGURE 1 is a graphical presentation of water retention and absorption r~sults obtained acc~rdirlg to Example 2 helow;
FIGURE 2 is a photomicrograph of a section through a product according to the invention.
The examples helow illustrate the invention and confirm its v~lu~.
Example 1 (prior art) This example is given for reference~
Manufacture of a standard sponge without addi~ion of S.A.P.
a) Wood pulp 1 NaOH
b) Alkali-cellulose c) Cellulose xanthat:e (viscose) l Addition of fibres and expanding agent d) Pulp 1 Coating on both sides of a grid 1 Acid baths e~ Regenerated cellulose Rinsing - bleaching Incorporation of MgCl2 ~ , Cutting up - packaging f) F inished product (290 g/m2 of dry cellulose) . Dimensions 20 x 20 cm 30 ' . Thickness 6 mm . Weight of cellulose 10 g . Weight of magnesium chloride MgCl2 3 g . Weight of water (8) 15 8 Example 2 Manufac~u~e of a sponge according to the invention containing 5% of S.A.P. in its bulk.
a) Wood pulp S 1 NaQH
b) Alkali-cellulose CS
~ 2 c) Cellulose xanthate (~iscose) 1 Fibres ~ expa~ding agent d) Pulp Coating of the pulp and dusting of encapsulated S.A.P~ as a sandwich be~ween two layers of viscose Acid bath e) Regenerated cellulose Rinsing - bleaching Thermal treatment (100C for 10 seconds) ~ Cutting up packaging f) F nished product . ~imensions20 x 20 cm . Thickness 6 mm . Weight of cellulose 10 g . Weight of S~A.P. 0.5 g . Weight of wa~er20 g Characteristics of the particles of S.A.P. incorporated:
- Diameter of the S.A.P. 280 - 400 ~m - Bilayer coating:
internal layer: behenic acid - ethylcellulose ~70/30) external layer: stearamide - polyst~rene (70/30 - Ccating thickness 30 ~m Samples from examples 1 and 2 were tested.
The table 1 below and the accompanying figure 1 lllustrate the impact of the modifications contributed according to the in~ention on the characteris~ics of absorption and retention of water of ~he products as well as on the kinetic~ of eYaporatioll of water.
S The applicant has deYeloped a new product of the sponge type which, in addition to the fact that it possesses an improved capacity for water retention, remains moist and supple for a longer time than a sponge of t~e prior art. To the touch and in appearance it is also improved.
In fact, in the dry state, a sponge is rough and retracts, whereas when it is moist it has a soft and pleasant feelO This change of state is seen particularly in thin sponges which become warped when dry.
In order to solve this problem -maintain a sponge humid and supple, particularly when it is being stored or on sale- it has been suggested, according to the prior art, that magnesium chloride and glycols be incorporated within the said sponge. This solution does not prove to be completely satisfactory. The said magnesium chloride and the said glycols are leached out as soon as the sponges are used and then no longer play their role in water retention and as plasticizers of the cellulose.
The applicant now suggests the introduction of particles of a superabsorbent polymer in the buLk of the said cellu1ar cellulosic material~ The specifications for the said particles will be provided below.
Particles of a superabsorbent polymer are already used advantageously in disposable products such as diapers.
Their introduction, according to the invention, into the area of sponges -within the cellulose network- is not an obvious step.
In fact, the simple incorporation of particles of a superabsorbent polymer during the manufacturing process for sponges or cellular cellulosic materials -cal~ed the viscose process without protection of the said particles invariably leads to degradation of the latter by hydrolysis and/or compression and, consequently 9 to a considerable loss of thei} water-retaining capacity.
The addition of the said particles after manufacture of the said cellular cellulosic material does not enable them to be inserted into the interior of the said material and be retained there mechanically. Furthermore, the presence of the said particles at the surface of the said material or sponge in the swollen state after absorption of water confers on it a slimy, sticky feel hardly appropriaee to its use, particularly in the area of household cleaning.
Absorbent articles obtained by the viscose process and containing particles of a superabsorbent polymer have been described in the patent application EP-A-0 293 ~08. The said particles are not trapped in the cellulose network at the interior of these articles.
The said articles are usually laminated materials; thus5 the particles of superabsorbent polymer are found betweell two layers of compressed cellulosic material.
The applicant now suggests a method for the incorporation of particles of superabsorbent pol~mer into the structure of cellular cellulosic materials without degradation and in a stable manner in order to obtain the expected results set out above.
Such materials, including the said particles in their cellulosic structure, constitute a subject of the invention; the process for their preparation constitutes another.
Thus, the subject of the present invention is a cellular cellulosic material with improved water retention, characterized in that it contains particles of a superabsorbent polymer trapped in the cellulose network.
Characteristically, the particles of superabsorbent polymer are found in the sponges of the invention, trapped in the cellulose network. They are localized in the interstices of the said cellulose.
It has been possible to produce such a currently novel structure by means of the process described below; the viscose process ~known to the person skilled in the art- in which, according to the invention, the temporarily protected particles of superabsorbent polymer are introduced into the viscose before the acidic regeneration of ehe cellulose.
The particles of su~erabsorbent polymer assume the function of retainers of water or any other liquid. They are particles of superabsorbent polymers (usually known under ~he abbreviation S.A.P.:
Super Absorbent Polymer~.
These polymers may be of natural or synthetic origin and, for the purposes of the invention, are advantageously insoluble in water.
For reasons of convenience r we will sometimes use the abbreviation S.A.P. in the continuation of the presen~ description.
These polymers - S.A.P.- when placed in contact with water form a physical or chemical gel, also called hydrogel, capable of absorbing considerable amounts of water in its macromolecular network.
Superabsorbent polymers (S.A.P.) of natural origin are for example polymers, the macromolecular network of which is of the polysaccharide type such as agar--agar, gelose, alginate, carboxy-methylcellulose, such as is described in particular in the patent US-A-3 58~ 364, hydroxyethylce]lulose, methylcelllllose, gelled cellulose triacetate as is described in particular in the patents US-A-l 693 8~0 and US-A-3 ~346 404, polyacrylonitrile-grafted starch as is described in particular in the patents US-A-3 93~ 099 and US-A-3 661 815 and acrylic acid-grafted starch such as is described in the patent FR-A-2 305 452.
Superabsorbent polymerc (S.A.P.) of synthetic origin are polymers, for example, the macromolecular network of which is ~ormed by acrylic polymers; hydroxyethyl methacrylate poLymers, cross-linked polyvinyl alcohol; polyacrylamide; partially hydrolysed poly~inyl acetate; hydroxyethyl acrylate; mono-acrylate of diethylene-glycol;
monomethacrylate of diethylene-glycol; 2-hydroxypropyl acrylate; 2-hydroxypropyl methacrylate; 3-hydroxypropyl acrylate; 3-hydroxypropyl methacrylate; monomethacrylate of dipropylene-glycol; vinylpyrrolidone;
acrylamide; methacrylamide; N-propylacrylamide; N-isopropyl-methacrylamide; N-methylacrylamide; N-2-hydroxyethylmethacrylamide;
hydrogels of polyurethane, composed of lightly cross-linked polymers of prepolymers terminated by an isocyanate which are the products of reaction of a poly(alkylenoxy)polyol with an organic diisocyanate lightly cross-]inked with water or an organic polyamine~ as described in the patent US-A-3 939 105; copolymers of acrylate monomers with ethylenic unsaturation and hydroxyalkyl methacrylates and acrylates and methacrylates of alkoxyalkylene-glycols, as described in the patent US-A-4 038 264 as well as other superabsorbent polymers (S.A.P.) known to the person skilled in the art.
The superabsorbent polymers ~S.A.P.~ of synthetic origin and insoluble in water are preferred because they are thermally more stable and les~s susceptible to degradation by the action of microorganisms.
The superabsorbent polymers (S.A.P.), lnsoluble in water, are obtained by the cross-linking of macromolecules and are available in the form of flakes, powders, films, fibres and spheres or "beads"
For the purposes of the invention, particles of spherical form, possessing a diameter included between about 50 and 400 ~m, will preferably be used.
For reasons of homogeneity of the water retention effect, it is desirable that the said particles are uniformly distributed and particles of S.A.P. possessing a diameter included between 50 and 200 ~m will advantageously be used.
In particular, products called "beads", produced by polymeri~ation in reverse suspension, will be used.
At present, such products are marketed in EUROPE by the HOECHST (ref. PL ~2'i5) 7 BASF ~Luquasorb HC 9797) and NORSOLOR (X 5 TS) companies.
In order l:o obtain the desired result, the cellular cellulosic materials according to the invention usually contain about 1 to 5% by weight of particles of S.A.P. with respect to the weight of dry cellulose. That they may contain a larger amount, up to 10%
or more, is in no way excluded. It will obviously be advisable to check thAt the amounts incorporated do not or not excessively impair the properties of the flnished product: feel, appearance, mechanical behaviour, According to a variant of the invention, the cellular cellulosic material is line~ on at least one of its faces with another material. It may be any type of material compatible with the cellular cellulosic material and the introduction of which presents any interest in the field of application of the said celLular cellulosic material.
As an illustration in no way limiting, mention should be made of the introduction of an expanded latex foam, cross-linked in particular like the one constituting the ~opping face of the product described in the patent application EP ~8 401 930.8 of the applicant, published under the number 0 335 050.
It has been observed tha~ the introduction of such a synthetic latex foam also improves the water retaining power of the cellular cellulosic material to which the foam is attached. The kinetics of the evaporation of water are found to be diminished without impairment of any of the properties of the sponge-type product possessing at least one mopping face made of synthetic latex.
Advantageously, such a composite material also contains particles of a superabsorbent polymer between the said cellular cellulosic material and the said other material.
Thus, at the interior of this composite material, particles of a superabsorbent polymer are encountered at the interface cellular cellulosic material/other material and in the bulk of the said cellular cellulosic material.
As specified above, the cellular cellulosic materials of the invention owe their attractive properties to ~he fact that they contain non-degraded particles of S.A.P.within their cellulose network.
The method of incorporation of the said particles within the said materials thus constitutes a key element of the present invention. This incorporation takes place during the prepara~ion of the said material by the viscose process, known to the person skilled in the art.
This process for the production of cellular cellulosic materials is summarized below.
Wood pulp is used as starting material. It is dissolved by means of ~he viscose process through the intermediary of the xanthate derivative with addition of an expanding agent and fibres.
The pulp obtained may ~e coated, ior example, on either side of a grid. This coating step is followed by a step of acidic regeneration of the cel~ulose. The pulp may also be introduced into a mould, then regenerated in a basic medium. The cellulose thus regenerated is then rinsed~ subjected to a bleaching treatment, Ctlt up and packaged. This process may optionally include one or more steps to modify the finished product, and in particular the lining of at least one of the faces of the said product with another material.
The cellular cellulosic material of the invention is produced in the framework of the viscose process with the addition of the following steps:
- incorporation of temporarily protected particles of a superabsorbent polymer into the cellulose xanthate (viscose) before regeneration, - optionally, dusting of temporarily protected particles of a superabsorbent polymer on a~ least one face of the said cellular cellulosic material obtained with acidic or basic regeneration of the cellulose, before the lining of the said face with another material, - and deprotection of the said particles of superabsorbent polymer in the last stage of manufacture of the materialO
According to a first variant, the said particles of S.~.P.
are introduced into the cellulose xanthate (viscose) preferably after the addition of the expanding aKent and ~he fibres.
In this lat:ter case, they are incorporated either into the mixer generating the mixture of the said expanding agent 7 fibres and the xanthate derivate, or during the coating of the mixture obtained -xanthate derivative (viscose) + fibres + expanding agent- and preferably between two layers of the said mixture.
The said particles of superabsorbent polymer are thus introduced into the process, temporarily protected. Their pro~ection must be such that, on the one hand, they withstand the steps of the viscose process that they may be re~uired to undergo and/or the additional steps of modificaticn of the product obtained by the said viscose process wlthout being damaged and, on the other, they can be deprotected without impairment of the said particles, their properties and the material in which they are present.
They can be ensured such protection by encapsulation in a monolayer or bilayer membrane, consisting essentially of one (or two) mixture(s) of at least one film-forming polymer and at least one hydrophobic crystalline material.
Such a membrane is the subject of a French patent application filed in the name of the Applicant on 12 September ~989 under the No. 89 11 924.
The combination of these two types of materials -film-forming polymer(s), hydrophobic crystalline material(s)- enables a ~ight membrane to be produced under the harsh conditions of the viscooe process; a membrane which nonetheless permits the release of the encapsulated S.A.P. The degradation or removal of the said membrane for the release of the S.A.P. may be accomplished in particular by mechanical means (compression, grinding, ultrasonics), by thermal means (heating, freezing), by actinic radiation (U.V., I.R., beams of electrons, microwaves) and by chemical means (change of pH, dissolution, chemical attack). Usually, the said S.A.P. is released by fusion of the hydrophobic crystalline material(s), involved in the composition of its membrane.
Advantageously, the said membrane materials are organo--soluble compounds. Their solubility in organic solvents enables particularly efficient techniques to be employed for coating the particles of the superabsorbent polymer (S.A.P.); techniques which will be specified below.
However, the invention does not exclude the employment of compoun~s slightly or not at all organosoluble in conjunction with the use of other techniques of coa~ing or surface film formation.
The film-forming polymer entering into the composition of the membrane according to the invention may be selected from the polymers of natural origin, the polymers of synthetic origin or their mixtures.
It may be advantageously selected from the cellulose derivatives -such as the ethylcelluloses, the acetophthalates or acetobutyrates of cellulose- or their mixtures.
Similarly, it may advan1_ageously be selected from the (co)polymers of styrene, vinylidene cllloride-based (co)polymers or their mixtures~
As indicated above, it may even consist of a mixture of at least one polymer of natural origin and at least one polymer of synthetic origin.
The hydrophobic crystalline material entering into the composition of the membrane is advantageously selected from the fatty acids, the derivatives of fatty acids (amides or bistearamides of fatty acids...), the microcrystalline waxes and their mixtures. In particular, behenic acid, stearic acid, stearamide, bistearamide or erucamide may be used. Advantageously a "pure" crystalline material~
possessing a sharp melting point, is selected. Then, in order to release the encapsulated particle of superabsorbent polymer (S.A.P.) it is always possible to raise the temperature of the medium -celiular cellulosic material- in which it is found to at least and possibly above the said sharp melting point.
The two principle constituents of the membrane are advantageously used in the following proportions by weight: about 10 to 90% of film-forming polymer for about 90 to 10% of hydrophobic crystalline material.
A mixture, particularly preferred when a polymer of natural origin is used, contains about 30% of the said film-forming polymer and 70% of the hydrophobic crystalline material.
In addition to its two principle constituents, the membrane may contain additives and in particular products intended to improve its wettability and/or its hydrophobicity and/or its adhesion to the particle of superabsorbent polymer (S.A.P.). For example, mineral lamellar fillers such as mica may be added in order to improve the hydrophobicity and the watertight of the membra~e.
According to one of the preferred variants of the invention, encapsulated particles of S.A.P. may be included ln a monolayer membrane consisting essentially of a mixture of about 30% by weigh~
of polystyrene and about 70~ by weight of stearamide.
According to another preferred variant of the invention, encapsulated particles of S.A.P. are included in a bilayer membrane, r~ r l --~ r~
the first layer of which consists essentially of a mixture of about 30~ by weight of polystyrene and about 70% by weight of stearamide and the second layer of which, the layer in contact wi~h the particle of S.A.P., consists essentially o~ a mixture of about 30% by weight of ethylcellulose and about 70% by weight of behenic acid.
It is obvious that the nature of the constituents entering into the composition of the membrane and the proportions in which they occur play an important role in the efficacy and duration of the protection of the encapsulated S.A.P. Other factors also need to be taken into account, in particular the thickness of the said membrane as well as the process used for its constitution.
The person skilled in the art is in the position to determine each of the said parameters for the optimi~ation of the said protection.
As far as the thickness of the membrane is concerned, it is obvious that by increasing it,the protection of the encapsulated product (S.A.P.) is improved.
In general, an effective protection -during the preparation of the cellular cellulosic materials of the invention- of the encapsulated S.A.P. is obtained with a membrane thickness included between 10 and 50 ~m.
The thickness of the monolayer or bilayer membrane, the nature of the constituents of which has been specified above, is advantageously included between 25 and 40 ~m.
All known suitable encapsulation techniques may be employed for the encapsulation of the particles of S.A.P.
Advantageously, the said S.A.P. may be encapsulated by spraying of the materials required to constitute the successive membranes, the said materials being dissolved in a suitable solvent.
This process can be implemented in particular with organosoluble materials, dissolved in an organic solvent which does not cause the superabsorbent polymer (S.A.P.) to be encapsulated to swell. Usual solvents such as alcohols t chlorinated solvents, alkanes..~ or their mixtures may be used.
This process is advantageously implemented in order to bring about encapsulation by means of surface film formation, in particular in a fluidi~ed bed. Techniques such as those used in the ~urster, Top Spray or tangential spraying processes can be used. These processes enable successive films to be formed around the particle of super-absorbent polymer by repeated exposure of the latter close to the nozzle of the spray.
Other coating techniques, known to the person skilled in the art, enable the particles of S.A.P. for the purposes of the invention to be produced. Special mention should be made of the techniques by fusion.
The tight of the coated particles obtained may be further improved, in some cases, by a thermal or annealing treatment (at a temperature lower than the melting point of the hydrophobic crystalline material).
Such a thermal treatment can be performed after the coating with a single layer or af~er coating with a first layer and/or after coating with a second layer.
The particles thus encapsulated preserve their water retention capacity intact. It has been possible to observe that even if the transfer of the particle between the different reaction mPdia rendered the shell brittle, the protection remained efficacious.
The problem of ~he deprotection of the said particles arises when the manufacturing process of the material is complete.
Advantageously, the said deprotection is performed during a final step in the manufacture of the said material.
This deprotection, in par~icular when it consists of removing the monolayer or bilayer membrane described above, may be performed by mechanical means, by thermal means or by actinic radiation and chemical means.
The deprotection by fusion (thermal means) is preferred.
For this purpose, the product obtained may be treated thermally either in a hot air tunnel or by hot water vapour or by microwaves or high frequency... In order to obtain the desired result -removal of che membrane described above- the product is usually treated at at least 100C for several seconds.
It should be noted that advantageously the said deprotection can be produced simultaneously with the cross-linking of a material applied to at least one face of the cel lular cellulosic material. It has been seen that such ~aterials may CO1lSiSt of an e~panded latex foam.
The cel]ular cellulosic material of the invention can thus be obtained by the viscose process with the introduction of the temporarily protected particles of S.A.P~
This protection can be provided by the monolayer or bilayer membrane described above.
Other types of protection can be developed and are not excluded from the framework of the present inventionO
The applicant specifies below two preferred variants of the method for the preparation of the cellular cellulosic materials according to the invention.
According to the first variant, sponges are prepared in bulk in which particles of S.A.P. are preEerably uniformly distributed.
The viscose process is used. The encapsulated particles of S.A.P. are incorporated into the cellulose xanthate (viscose).
The product obtained undergoes an acidic regeneration. After rinsing and bleaching, the cellular cellulosic material obtained is subjected to a thermal treatmen~.
The aim of the said thermal treatment i5 to release the said particles of S.A.P. distributed in the bulk of the said material.
It is performed at at least 100C for several seconds.
According to the second Yariant, a mopping cellular cellulosic material is prepared such as that described in the application EP O 335 050 of the Applicant :
On one face of a cellular cellulosic material obtained by the viscose process as modified abo~e (by incorporation of encapsulated particles of S.A.P. in the cellulose xanthate) encapsulated particles of S.A.P. are dusted. The said face is then coated with a non-crosslinked latex foam. The entire preparation is then subjected to a thermal treatment, the parameters of which are fixed in order ensure both ~he cross linking of the said foam and the release of the encapsulated particles of S.A~P. The de~erminatlon of these parameters lies wlthin the competence of a person skilled i~ the art.
In the ~ccompanying drawings-:
FIGURE 1 is a graphical presentation of water retention and absorption r~sults obtained acc~rdirlg to Example 2 helow;
FIGURE 2 is a photomicrograph of a section through a product according to the invention.
The examples helow illustrate the invention and confirm its v~lu~.
Example 1 (prior art) This example is given for reference~
Manufacture of a standard sponge without addi~ion of S.A.P.
a) Wood pulp 1 NaOH
b) Alkali-cellulose c) Cellulose xanthat:e (viscose) l Addition of fibres and expanding agent d) Pulp 1 Coating on both sides of a grid 1 Acid baths e~ Regenerated cellulose Rinsing - bleaching Incorporation of MgCl2 ~ , Cutting up - packaging f) F inished product (290 g/m2 of dry cellulose) . Dimensions 20 x 20 cm 30 ' . Thickness 6 mm . Weight of cellulose 10 g . Weight of magnesium chloride MgCl2 3 g . Weight of water (8) 15 8 Example 2 Manufac~u~e of a sponge according to the invention containing 5% of S.A.P. in its bulk.
a) Wood pulp S 1 NaQH
b) Alkali-cellulose CS
~ 2 c) Cellulose xanthate (~iscose) 1 Fibres ~ expa~ding agent d) Pulp Coating of the pulp and dusting of encapsulated S.A.P~ as a sandwich be~ween two layers of viscose Acid bath e) Regenerated cellulose Rinsing - bleaching Thermal treatment (100C for 10 seconds) ~ Cutting up packaging f) F nished product . ~imensions20 x 20 cm . Thickness 6 mm . Weight of cellulose 10 g . Weight of S~A.P. 0.5 g . Weight of wa~er20 g Characteristics of the particles of S.A.P. incorporated:
- Diameter of the S.A.P. 280 - 400 ~m - Bilayer coating:
internal layer: behenic acid - ethylcellulose ~70/30) external layer: stearamide - polyst~rene (70/30 - Ccating thickness 30 ~m Samples from examples 1 and 2 were tested.
The table 1 below and the accompanying figure 1 lllustrate the impact of the modifications contributed according to the in~ention on the characteris~ics of absorption and retention of water of ~he products as well as on the kinetic~ of eYaporatioll of water.
2 ~
Table 1 Absorption and retention of tap water by samples 1 and 2 S _ _ .................. ___ _ l 1) Water absorption (g) 2) Water retention (g) _ ____ Sample ex 1100 - 120 10 - 15 Sample ex 2175 - 200 ¦ 80 - 90 (1) Total tap water absorption measured according to the Edana standard 10.1.-72 (2) Retention of tap water after centrifugation (3000 rev/mn 12 seconds). The centrifugation corresponds to a mean manual expression of absorbed water by the product.
The cur~es for water evaporation (figure 1) were drawn up under controlled atmospheric conditions: 20C - 50% R.H. They give the kinetics of evaporation of water from the samples after one rinsing with tap water followed by a centrifugation under the conditions taken from (2) above.
Table 1 and figure 1 demonstrate the desired impro~ement in water retention.
In figure 2 - micrograph through a section of a sponge fabric of the invention, micrograph obtained by means of scanning electron microscopy (enlargement x 35)- it can be clearly seen that the particles of the superabsorbent polymer are in the interior of the interstices of the cellulose (in the network).
Table 1 Absorption and retention of tap water by samples 1 and 2 S _ _ .................. ___ _ l 1) Water absorption (g) 2) Water retention (g) _ ____ Sample ex 1100 - 120 10 - 15 Sample ex 2175 - 200 ¦ 80 - 90 (1) Total tap water absorption measured according to the Edana standard 10.1.-72 (2) Retention of tap water after centrifugation (3000 rev/mn 12 seconds). The centrifugation corresponds to a mean manual expression of absorbed water by the product.
The cur~es for water evaporation (figure 1) were drawn up under controlled atmospheric conditions: 20C - 50% R.H. They give the kinetics of evaporation of water from the samples after one rinsing with tap water followed by a centrifugation under the conditions taken from (2) above.
Table 1 and figure 1 demonstrate the desired impro~ement in water retention.
In figure 2 - micrograph through a section of a sponge fabric of the invention, micrograph obtained by means of scanning electron microscopy (enlargement x 35)- it can be clearly seen that the particles of the superabsorbent polymer are in the interior of the interstices of the cellulose (in the network).
Claims (14)
1. Cellular cellulosic material with improved water retention, characterized in that it contains particles of a superabsorbent polymer trapped in the cellulose network.
2. Cellular cellosic material according to Claim 1, characterized in that the said particles are spheres about 50 to 400 µm, and preferably included between 50 and 200µm, in diameter.
3. Cellular cellosic material according to Claim 1, characterized in that its contains about I to 5 % by weight of the said particles with respect to the weight of dry cellulose.
4. Cellular cellosic material according to Claim 1, characterized in that it is lined on at least one of its faces with another material, such as a cross-linked expanded latex foam.
5. Cellular cellosic material according to Claim 4, characterized in that it contains additionally particles of superabsorbent polymer between the said cellular cellulosic material and the said other material.
6. Preparation by means of the viscose process of a cellular cellulosic material according to Claim 1 -starting from dissolved wood pulp through the intermediary of the xanthate derivative (viscose), with addition of an expanding agent and fibres, acidic of basic regeneration of the cellulose obtained, rinsings and bleaching-optionally followed by the lining of at least one of its faces by another material, characterized in that it comprises the additional steps :
- incorporation of temporarily protected particles of superabsorbent polymer into cellulose xanthate (viscose) before regeneration, - optionally, dusting of temporarily protected particles of superabsorbent polymer on at least one face of the said cellular cellulosic material obtained with acidic or basic regeneration of the cellulose, before the lining of the said face with another material, - and deprotection of the said particles of superabsorbent polymer in the last phase of manufacture of the material.
- incorporation of temporarily protected particles of superabsorbent polymer into cellulose xanthate (viscose) before regeneration, - optionally, dusting of temporarily protected particles of superabsorbent polymer on at least one face of the said cellular cellulosic material obtained with acidic or basic regeneration of the cellulose, before the lining of the said face with another material, - and deprotection of the said particles of superabsorbent polymer in the last phase of manufacture of the material.
7. Preparation according to Claim 6, characterized in that the temporarily protected particles of superabsorbent polymer are incorporated after the addition of the expanding agent and fibres either in the mixer generating the mixture of the said expanding agent, fibres and xanthate derivative (viscose), or during the coating of the mixture obtained -xanthate derivative (viscose) + fibres + expanding agent- and preferably between two coats of the said mixture.
8. Preparation according to Claim 6, characterized in that the said particles of superabsorbent polymer, incorporated and optionally dusted, are coated with a monolayer or bilayer membrane consisting essentially of one (or two) mixture(s) of at least one film-forming polymer and at least one hydrophobic crystalline material.
9. Preparation according to Claim 8, characterized in that the said film-forming polymer is selected from :
- polymers of natural origin such as the cellulose derivatives and in particular the ethylcelluloses, the acetophthalates of cellulose or the acetobutyrates of cellulose, - polymers of synthetic origin such as styrene (co)polymers or vinylidene chloride-based (co)polymers, - or their mixtures, and in that the said crystalline material is selected from the fatty acids -and in particular behenic acid, stearic acid- the derivatives of fatty acids -and in particular stearamide, bistearamide or erucamide-the microcrystalline waxes and their mixtures.
- polymers of natural origin such as the cellulose derivatives and in particular the ethylcelluloses, the acetophthalates of cellulose or the acetobutyrates of cellulose, - polymers of synthetic origin such as styrene (co)polymers or vinylidene chloride-based (co)polymers, - or their mixtures, and in that the said crystalline material is selected from the fatty acids -and in particular behenic acid, stearic acid- the derivatives of fatty acids -and in particular stearamide, bistearamide or erucamide-the microcrystalline waxes and their mixtures.
10. Preparation according to Claim 9, characterized in that the said particles of superabsorbent polymer are coated with a monolayer membrane consisting essentially of a mixture of about 30 % by weight of polystyrene and about 70 % by weight of stearamide.
11. Preparation according to Claim 9, characterized in that the said particles of superabsorbent polymer are coated with a bilayer membrane, the first layer of which (external layer) consists essentially of a mixture of about 30 % by weight of polystyrene and about 70 % by weight of stearamide and the second layer of which consists essentially of a mixture of about 30 % by weight of ethylcelluloses and about 70 % by weight of behenic acid.
12. Preparation according to Claim 8, characterized in that the said particles of superabsorbent polymer are deprotected on completion of the manufacturing process for the material or during a final phase of manufacture of the latter by degradation or even removal of the membrane by mechanical, thermal or chemical means or by actinic radiation.
13. Preparation according to Claim 8, characterized in that the said particles of encapsulated superabsorbent polymer are incorporated into the cellulose xanthate (viscose) and in that after acidic regeneration, the material is in particular rinsed, bleached and subjected to a thermal treatment -for several seconds at more than 100°C- in order to release the said particles of superabsorbent polymer within the cellular cellulosic material obtained.
14. Preparation according to Claim 8, characterized in that the encapsulated particles of superabsorbent polymer are dusted on one face of the cellular cellulosic material obtained by the viscose process with incorporation of encaspulated particles of superabsorbent polymer into the cellulose xanthate (viscose), the said face being then coated with a non-cross-linked latex foam and subjected to a thermal treatment ensuring both the cross-linking of the said foam and the release of the particles of superabsorbent polymer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8911925A FR2651783B1 (en) | 1989-09-12 | 1989-09-12 | CELLULOSIC ALVEOLAR MATERIAL WITH IMPROVED WATER RETENTION AND PREPARATION THEREOF. |
| FR8911925 | 1989-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2025035A1 true CA2025035A1 (en) | 1991-03-13 |
Family
ID=9385374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002025035A Abandoned CA2025035A1 (en) | 1989-09-12 | 1990-09-11 | Cellular cellulosic material with improved water retention and preparation of the latter |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0418151A1 (en) |
| CA (1) | CA2025035A1 (en) |
| FR (1) | FR2651783B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002070125A1 (en) * | 2001-03-03 | 2002-09-12 | Fluid Technologies Plc | Absorbent materials |
| CN114206283A (en) * | 2019-09-26 | 2022-03-18 | 大王制纸株式会社 | Functional sheet, absorbent article provided with same, and method for producing same |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4122359C2 (en) * | 1991-07-05 | 1993-12-02 | Helen Harper Hygienic Gmbh | Absorbent material and its use |
| FR2703057B1 (en) * | 1993-03-24 | 1995-06-16 | Elysees Balzac Financiere | Cellulose cellular material containing a biocidal agent and process for its preparation. |
| AT402932B (en) * | 1995-12-22 | 1997-09-25 | Chemiefaser Lenzing Ag | CELLULOSE SPONGE AND METHOD FOR THE PRODUCTION THEREOF |
| GB9626894D0 (en) * | 1996-12-24 | 1997-02-12 | Courtaulds Fibres Holdings Ltd | Cellulosic sponges |
| FR2767541B1 (en) * | 1997-08-21 | 1999-10-08 | Hutchinson | SPONGIOUS MATERIAL, MANUFACTURING METHOD THEREOF AND APPLICATIONS THEREOF |
| DE102005007270A1 (en) | 2005-02-17 | 2006-08-24 | Kalle Gmbh | Sponge cloth, process for its preparation and its use |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3954493A (en) * | 1972-10-19 | 1976-05-04 | Avicon, Inc. | Regenerated cellulose sponge |
| US4069366A (en) * | 1975-03-26 | 1978-01-17 | Rohm And Haas Company | Permeable polymeric liner on absorbent pads |
| DE2707308C2 (en) * | 1977-02-19 | 1982-07-01 | Hoechst Ag, 6000 Frankfurt | Shaped bodies with a spongy structure based on regenerated cellulose for medical purposes |
| US4169121A (en) * | 1977-09-09 | 1979-09-25 | Helmut Pietsch | Absorbent material for aqueous physiological fluids and process for its production |
| EP0055056A1 (en) * | 1980-12-22 | 1982-06-30 | Rohm And Haas Company | Alloy rayon fibers of high fluid-holding capacity, method of producing them and manufactured articles comprising them |
| US4429001A (en) * | 1982-03-04 | 1984-01-31 | Minnesota Mining And Manufacturing Company | Sheet product containing sorbent particulate material |
| DE3863846D1 (en) * | 1987-05-27 | 1991-08-29 | Lion Corp | ABSORBENT ARTICLE. |
| JP2626758B2 (en) * | 1987-05-27 | 1997-07-02 | ライオン株式会社 | Absorbent articles |
| FR2629334B1 (en) * | 1988-03-30 | 1991-09-13 | Spontex Sa | CELLULOSIC ALVEOLAR WIPING MATERIAL |
-
1989
- 1989-09-12 FR FR8911925A patent/FR2651783B1/en not_active Expired - Fee Related
-
1990
- 1990-09-11 CA CA002025035A patent/CA2025035A1/en not_active Abandoned
- 1990-09-12 EP EP90402507A patent/EP0418151A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002070125A1 (en) * | 2001-03-03 | 2002-09-12 | Fluid Technologies Plc | Absorbent materials |
| CN114206283A (en) * | 2019-09-26 | 2022-03-18 | 大王制纸株式会社 | Functional sheet, absorbent article provided with same, and method for producing same |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2651783A1 (en) | 1991-03-15 |
| FR2651783B1 (en) | 1993-05-07 |
| EP0418151A1 (en) | 1991-03-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19940312 |