CA1077788A - Process for the transformation of comminuted and swellable cellulose ether into an easily workable material - Google Patents
Process for the transformation of comminuted and swellable cellulose ether into an easily workable materialInfo
- Publication number
- CA1077788A CA1077788A CA258,212A CA258212A CA1077788A CA 1077788 A CA1077788 A CA 1077788A CA 258212 A CA258212 A CA 258212A CA 1077788 A CA1077788 A CA 1077788A
- Authority
- CA
- Canada
- Prior art keywords
- cellulose ether
- web
- water
- modified cellulose
- comminuted
- 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.)
- Expired
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Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H19/00—Coated paper; Coating material
- D21H19/10—Coatings without pigments
- D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
- D21H19/34—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising cellulose or derivatives thereof
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/22—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
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- Health & Medical Sciences (AREA)
- Hematology (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Epidemiology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Absorbent Articles And Supports Therefor (AREA)
- Laminated Bodies (AREA)
- Paper (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the transformation of comminuted and modified cellulose ethers which are swellable with water into a material which is not only desirably swellable but also predominantly insoluble in water and thus suitable for further processing and use in medical bandages, hygienic pads, napkins, tampons and the like.
A process for the transformation of comminuted and modified cellulose ethers which are swellable with water into a material which is not only desirably swellable but also predominantly insoluble in water and thus suitable for further processing and use in medical bandages, hygienic pads, napkins, tampons and the like.
Description
~ 77'7~
The present invention relates to a process for the transformation of comminuted and modified cellulose ether swellable with water, into a material that may easily be further processed and may thus be used without difficulty, in particular, in the production of hygienic pads, napkins, bandagesg tampons, wrapping papers, insulating material, household papers and similar articles.
For the manufacture of such products, tissues or fleeces are used that can absorb a~ueous liquids, in particular physiological body fluids such as blood or urine. Cellulose in the form of tissues, bai~e, cotton wool or paper is mainly used. For a long time certain substances ha~e been added in order to increase the capacity of these articles to absorb aqueous liquidsO
For example moist potato flour, dextrine or gelatine have been applied to the cellulose material and dried as disclosed in German Patent NoO 489,309.
Recently it has become known to use cellulose ethers, which have been rendered at least largely water-insoluble by modification, for increasing the water absorption capacity of such materials. Modification is carried out with the cellulose material before, during or after the etherification of the cellulose. The etherification agent and the degree of etherification are ; chosen in such a manner that without modification a cellulose ether essen-` 20 tially soluble in water of 20C would be produced. By means of the modifi-cation the cellulose ether is rendered at least largely water-insoluble but is highly swellable with water. Processes for the manufacture of such modified ~ cellulose ethers are described in United States Patent Specifications Nos.
-~ 3,589S364 and 3,723,413. The cellulose ethers modified in this manner maintain :
their fibrous structure. This is done on purpose, in order to render possible further processing of the modified cellulose ethers obtained, either on their own or mixed with fibres of other cellulose material to form fibre fleeces, baize, bandages, cushions, napkins or tamponsO
Since the compounds mentioned abo~e are often in a fibrous state it ~ .
, , . . . , ~ ', ,: ~ : ,:. ; ' . , :
~1~77~8~3 is possible to transform them into flat-shaped articles, for example by suspending them in a wet process similar to that of paper production. However, the flat-shaped articles that can be produced in this manner have a rigidity similar to that of paper and are brittle, so that they can hardly be used in the hygienic field, e.g. in napkins or tampons.
In German Offenlegungsschrift No. 2,441,781 it has also been disclosed to fix modified cellulose ethers on textile areas by means of binders. The flat-shaped articles produced in this manner do have an increased absorption capacity towards liquids. However, this increased absorption capacity is low relative to the quantity of cellulose ether used, because the binder makes a portion of it ineffective. Furthermore, in this method the portion of binder may cause a hardening which is undesired, especially if the products are to be used as hygienic articles.
Thus the production of modified cellulose ethers and their further processing into useful objects were limited and further development in this technical field was hindered.
It is one object of the present invention to provide a process other than fleece-forming or baize-forming for transforming comminuted and ` modified cellulose ethers swellable with water into a material that can easily be further processed and may thus be used especially in the production of medical bandages, hygienic pads, napkins, tampons and similar articles.
By the present invention a coated web composed of a hydrophilic cellulose material is provided.
According to the present invention, there is provided a process for the transformation of comminuted cellulose ether, at least a major portion of which has been rendered water-insoluble by modification but which is still :! hignly swellable with wa~er, into an easily workable material, characterized - in that the co~minuted modified cellulose ether is attached to at least one ` surface of a web-shaped support composed of hydrophilic material and the ~` 30 support is then dried, the process further comprising the attaching of the modified cellulose ether to the support by means of electrostatic flocking ~B
~L~77788 or comprising the covering of the support, which is wetted with water, with a comminuted and modified cellulose ether, or comprising the coating of the support with a dispersion of the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent.
In another aspect oE the present invention, there is provided a coated web formed of a hydrophilic cellulose material characterized in that a comminuted and modified cellulose ether is attached to at least one surface of the hydrophilic cellulose material elther by means of electrostatic flocking or by covering said hydrophilic cellulose material, which is wetted with water, with a comminuted and modified cellulose ether or by coating the hydrophilic cellulose material with a dispersion of the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent.
The modified cellulose ethers usable in the process and included on the web are not only those having a fibrous structure, but they may have any form as long as they are comminuted, pourable, suspendible and electro-, statically flockable. Cellulose ethers in this state will hereinafter often be called powder, irrespective of the fact whether the particles are fibrous ~ crumbs of irregular shape or otherwise comminuted. The size of the particles ,;'..
'! iS of no decisive importance for the realisation of some embodiments of the invention. It may be 1 mm and more. In practice, however, it is mainly inthe range of from approximately 0.02 to 0.5 mm. Cellulose ethers are prefer-ably used that are modified by cross-linking according to the process described .
in German Offenlegungsschrift No. 23 57 079 or that are modified according to German Offenlegungsschrift No. 23 58 150. They are characterized by high ,. ., water absorption and water retention values. Modified cellulose ethers usable within the scope of the invention are also, for example, those given in German Patent No. 839,492, in United States Patent Specifications Nos. 3,589,364, 3,723,413 or 2,639,239~
These modifications of cellulose ethers lead to products having an acceptable water absorption capacity even if the modified cellulose ether still contains water-soluble parts. Thus in practice cellulose ethers are often not '.
'~
` ~977788 modified to form completely water-insoluble products, and in most cases the water-soluble parts are not removed from the modified cellulose ethers. The water-soluble portion may consist of those parts of cellulose ether which were not modified at all or of those parts which were not modified enough to become water-insoluble. A water-soluble portion of at least ' :
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~777~8 ;~
lS per cent by weight is advantageous in most cases, because it improves adhesion of the particles of modified cellulose ether to the hydrophilic web.
Howe~er, the water-soluble portion should not exceed approximately SO per cent by weight.
The hydrophilic web serving as a support preferably consists of a tissue, knit fabric or fleece or in particular of a paper composed of cellu-lose, wood pulp or synthetic fibres, especially a polyolefin fibre as described in German Offenlegungsschrift No. 21 17 370, or mixtures of them and has certain absorption and retention capacities towards liquids. The weight of this material is between 12 and 500 g/m2. .^~
In a preferred embodiment of the process according to the invention at least one surface of the web composed of hydrophilic material is wetted with water and is then covered with the comminuted modified cellulose ether.
The easiest way of wetting the surface of the support is to dip the web for a short moment into water and then squee&e it to the desired degree of mois-ture. The swellable powder is applied, for example, by strewing it onto the moist surface of the web, or in a vortex chamber.
In the process only those powder particles are attached-to the support that come into direct contact with the moist su~rface. The maximum amount of powder particles adhering to the surface is deter~ined by the number of particles that can lie closely side by side in one layer on the moist surface of the support. This highest density uill be used in those cases in which it is important to obtain a maximum water absorption capacity per unit of area. In this case more than the necessary amount of powder may be applied to the moist surface, since the excess powder can be easily re-moved, for example by blowing, and can then be reused. On the other hand, if maximum use is to be made of the water absorption capacity of the absorbent - powder, it is useful not to apply to the moist support more than 50 per cent by weight of the maximum amount of powder that can be applied according to the process of ~he in~ention. If the water-absorbing powder is to adhere ., ' ' , 9 . ,' ~77788 only to parts of the surface, for example if uncoated marginal areas or a coating according to a different pattern is required, it is useful to wet the surface of the web only in parts, i.e. according to the pattern desired7 e.g. by spraying it with water according to the pattern. The pattern desired may also be obtained by applying the powder to parts of the moist surface of the web. In this case the web surface or the whole web may be wetted, e.g.
by dipping it into water.
~n apparatus for carrying out the process described above consists mainly of the following devices:
a) a device for applying water to the web-shaped support, b) a device for applying the comminuted cellulose to the wetted surface and ~ c) a device for drying the coated support .,~. furthermore, a device for transporting the web-shaped support through the ~ devices a), b) and c) is necessary. The covering within the device b) may .~ be carried out in particular by powdering with the aid of a vibration screen :;, device or in a vortex chamber.
~,,;. ::
In device a), the web to be covered is passed, for example, through a vessel filled with water and is then squeezed by a squeegee roller to the :j 20 water content desired.
If the device b) for powdering the web is a vibration screen de-vice, usually only one side of the web is powdered, i.e. its upper surface.
If both sides are to be powdered, the web is, after being powdered on one side, deviated by a deviating roller for example, and is guided back into the device b) in such a manner that its bottom surface becomes its top sur-face. During this process the part of the web moving forward and the part moving backward must not be superposed. By means of the passing speed of the web and the way in which the screen is vibrated the powdering of the web surface can be controlled so as to apply more or less powder to it, as de-sired. If more powder is applied to the moist web surface than can adhere to it, the excess powder is removed from the web, is collected and is reused in another powdering process.
If the device b) for powdering is a vortex chamber, both surfaces of the moist web guided through it are covered with the powder whirled up by compressed air.
The drying device c) consists, for example, of drying drums around which the covered web is guided.
In another preferred embodiment of the process according to the invention the support is covered with a dispersion produced by dispersing the modified cellulose ether in an organic solvent, to which water may be added if necessary.
An alkyl hydroxyalkyl cellulose ether is preferably used as an unmodified cellulose ether. It should preferably have a ~iscosity of about 10 to 30,000 cP in a 2 per cent strength aqueous solution at 20C.
Preferably an alcohol such as methanol, ethanol, propanol-l, propanol-2, butano~-l, butanol-2, methyl propanol-l or methyl propanol-2, a ketone such as methyl ethyl ketone or diethyl ketone, a chloroderivative of methane such as methylene chloride or chloroform or especially mixtures of these solvents are used as the organic solvent in which the unmodified cel-lulose ether is dissolved or which is mixed with an aqueous solution of the unmodified cellulose ether at a ratio of 60 to 90 parts by weight to 40 to 10 parts by weight, preferably about 75 to 85 parts by weight to 25 to 15 parts by weight.
For the preparation of the suspension approximately 1 to 200 g/l, preferably 100 to 160 g/l of comminuted modified cellulose ether having a preferred average particle size of 0.02 to 0.25 mm are added to the solution of organic solvent and unmodified cellulose ether, to which water may be added if necessary, in such a manner that the suspension to be applied has a viscosity of 20 to 25 seconds, measured in a Ford measuring cup having a 4 mm die.
1~777~8 The web-shaped supports used for the application of the suspension may be wet-strength supports.
The coating of the support with the suspension is carried out in a coating device provided with a roller. The covering of the surface of the support by the layer may be incomplete, for example if the roller in the application device has a screen-shaped or punctiform surface structure (e.g.
in the case of a gravure printing roll). The quantity of suspension to be applied is determined such that after the coating about 0.5 to 50 g/m2 of the modified cellulose ether are on the support. ' In addition, a web-shaped hydrophilic material having the same composition as or a ccmposition similar to, the uncoated support may be laminated onto the coated side of the support.
In another preferred embodiment of the process according to the invention the modified cellulose ether is attached to the support by means of electrostatic flocking.
~ This electrostatic flocking and thus coating of the support is .~ effected by wetting at least one of its surfaces with water, for example by ;~J dipping, spraying or impregnating and guiding the still wet material through a high-voltage field of up to 100 ~v, preferably about 30 to 60 kv. One of the two electrodes which produce the high-voltage field has the shape of a screen or a perforated plate and serves the purpose of housing the modified cellulose ether, which prefera~ly consists of very short fibres having a length of from about 0.05 to 1 mm, advantageously about 0.05 to 0.3 mm, and does not require any particular preparation of the fibre or any antistatic aids. The width of mesh or the diameter of one perforation of the electrode is determined such that it is 60 to 100 times the diameter of the cellulose ether fibre. The counter-electrode is flat-shaped, and within the area of the high-voltage field it is not confined to its electrostatic use, but also s~rves, for example~ as a support for the material to be flocked that is guided between the two electrodes in such a manner that it is at a distance -- 7 _ 777~
of about 10 to 50 cm from the perforated or screen electrode and is close to the counter-electrode.
After having passed through the electric field the flocked material is dried, for example by a heat radiator or in a heating chamber and may then be wound up.
In the case of material having a low wet strength, like tissue paper for example, an endless belt able to support load may be used as an additional support between the storage roller and the wind-up roller, a belt which consists especially of a plastics film, a plastics grate or a metal net. This device is advantageously arranged in the area of the apparatus through which the wet material passes, i.e. the area between the wetting and drying areas.
In another embodiment of the latter process~ which is preferably , applied in the electrostatic flocking of material such as crepeA paper in order to maintain its original shape, e.g. the crepe, first an endless belt ,~
is wetted which then in turn wets the material to be flocked that comes into contact with the belt. Flocking and drying are carried out as described above.
The material to be flocked onto the support, which consists of ; 20 modified cellulose ether, is advantageously kept in motion by mechanical means, e.g. by slight vibration or a revolving scraper, in order to a~oid bridge-forming between its particles in the electrode, because this may im-pair the mobility of the flocks.
The cellulose ether particles are pushed from the screen electrode in the direction of the counter-electrode and thus also in the direction of the web-shaped support between the electrodes. They absorb water from the wet surface of the support and swell. The swelling preven-ts a pos`sible re-turn of the particles, which may be caused, for example, by charge reversion, and thus the support is uniformly covered with modified cellulose ether.
It is expected that during the drying that follows the swollen particles are glued to the support, thus ensuring good adhesion and preventing ~L~7778~3 the particles detaching themselves in the form of dust.
The process according to the invention may be carried out continu-ously as well as discontinuously, the density of the coating on the support being widely variable. It depends, for example, on the quantity of water applied, on the voltage applied to the electrodes, but also on the particle size of the modified cellulose ether to be flocked. The density may be up to 100 g/m2, in the case of material to be used for hygienic purposes it pre-ferably is 15 to 30 g/m2. ~
All the web-shaped materials produced according to the process of -the invention, especially according to its preferred embodiments, are highly ~ ;
absorbent and have a high liquid retention capacity. Since they are also easily workable it is advantageous to include them as a bottom, intermediate or top layer in flat-shaped laminar articles as they are used, for example, in the hygienic field in bandages, napkins or bed sheets, in order to improve their absorption capacity. The material produced according to the invention I may also be used as intermediate layers in flat-shaped articles ha~ing a ; "sandwich structure", for example dish-cloths, oil-absorbing mats and the like. ~-~xample 1 -.: .
A web of creped paper having a weight of 48.32 g/m2 is guided through water, as shown in the description, and after removing the water ad-hering to it is passed through a laboratory screen device. The modified car-boxy methyl cellulose to be applied, which is largely water-insoluble and has a water absorption capacity of 3800 g/100 g, is applied through an 0.2 mm screen, so that after drying the weight of the paper is increased by 42 g/m2 ~efore the powder mg the creped paper has an absorption capacity of 336 g per 100 g. Due to the powdering its water absorption capacity increases to 2012 g per 100 g of powdered paper. Its absorption capacity towards synthetic urine solution increases from 70 to 145 g and towards synthetic blood solu-tion from 71 to 127 g per 100 g of powdered paper (synthetic urine solution , _ g _ , ' : , , ', , ` ' ' ', ' 1 ~ ; ', ; 1 ;; "~ ~, , "~ ~ ~ " " ",, "~ "~" ,,, ; ; , " ~ , ;
777~
and synthetic blood solution are aqueous solutions the physical properties o~
which are very similar to human urine and blood).
Example 2 A tissue paper web having a weight of 23.6 g/m2 is wetted and powdered as described in Example l. After drying, its weight has increased by 52 g/m2. The water absorption capacity of the powdered tissue paper in-creases from 650 to 3000 ml per 100 g.
Example 3 A tissue paper web having a weight of 31.5 g/m2 is wetted and sub-sequently powdered on both surfaces as shown in the description. The moist web is deviated within the powdering chamber and dried only after the second powdering. The weight increase after drying is 4.7 g/m , and the absorption capacity increases from 800 to 1440 g of water per lO0 g of paper.
Example 4 A web of regenerated cellulose having a weight of 48 g/m is soaked with a 4 per cent strengbh aqueous glycerin solution, liquid adhering to it is removed, and one surface of the web is then powdered with a swellable cellulose ether in the powdering device shown in Example 1. After drying, its weight is 80 g/m , and its absorption capacity has increased from 200 to 2460 ml of water per lO0 g.
Example 5 After being wetted, a medical mull bandage having a width of 8 cm is powdered on one side with a cellulose ether which has a blood retention value of 980 ml/lO0 g, and after drying the weight of the bandage has in-creased by 20 per cent. Its blood retention capacity increases from 763 to 1298 ml per lO0 g of mull bandage.
Example 6 A tissue paper web having a weight of 31.5 g/m2 is powdered on one side, as described in Example 1, with a modified cellulose ether ~he water absorption capacity of which is 3800 ml per lO0 g, and its absorption cap-, ~137778~
acity towards a 1 per cent strength salt solution is 2000 ml per 100 g. The powdering density is increased to its maximum, i.e. 16 g/m2. The following results were obtained:
Absorption capacit:y per 100 g of material:
ml of 1% strength Material: NaCl solution ml of water tissue paper without powder 420 420 with 1~6 g/m of powder 600 750 with 3.2 g/m2 of powder 800 1440 with 8.0 g/m2 of powder 950 1S80 with 16 g/m2 of powder 1100 2000 powder 2000 3800 The results are shown in a diagram in Figure 1. It can be seen that the absorption capacity (coordinate), based on an increase in the amount of powder (abscissa) by 1 g, increases the more the less powder has been used on the whole and that when the maximum powder application of 16 g/m is ap-proached, the absorption capacity increases only insignificantly with an increase of 1 g in the powder quantity. It can also be seen that with half of the maximum powdering, i.e. 8 g/m , an absorption capacity towards dis-tilled water of 1580 ml per 100 g of web material is obtained, and an absorp-tion capacity towards a 1 ~er cent strength salt solution of 950 ml per 100 g of web material. Thus the maximum values of 2000 g and 1100 g per 100 g of web material are already approached.
Example 7 One side of a cellulose paper having a weight of 24 g/m2 is coated in a coating device provided with a roller and having a drying chamber and a suction device for removing solvent vapours~ The suspension to be applied is prepared from 200 ml of a two per cent strength aqueous solution of methyl hydroxy ethyl cellulose ether having a viscosity of 1,000 cP at 20C, oE
800 ml of aqueous isopropanol (87 per cent strength), and 100 g o:E particles ~77788 of a carbo~y methyl cellulose modified with the cross-linking agent bis-acrylamido acetic acid and having an average particle size of less than 0.2 mm. After drying more than 10 g/m2 of the modified cellulose ether are in the coating. The following example shows one of the purposes for which the coated paper may be used.
Example 8 2 ~ !
A sample of 100 cm size is cut out of a coated cellulose paper produced according to Example 7 and is immersed in water for 15 seconds. The water adhering to the surface after taking the paper out is removed by dabb-ing it with blotting paper, and then the sample is weighed. In its dry state it weighs 0 29 g and in its wet state 1.06 g, which means that it has absorb-ed 0.77 g of water. A sample of uncoated paper weighs 0.25 g in its dry state and 0.63 g in its wet state, i.e. it has absorbed 0.38 g of water. The absorption capacity of the paper coated according to the invention is thus about twice as high as that of the uncoated paper.
Example 9 A tissue paper having a weight of 18 g/m2 is coated as described in Example 7, and the quantity applied is 12.7 g/m . If samples of this coated paper and of uncoated paper each having a size of 1260 cm are dipped into a synthetic urine solution, each of them together with a filter paper sheet having the same si~e, and after 15 minutes are taken out and centrifuged in a laboratory centrifuge at 1,000 revolutions per minute, the following fig-ures for the liquid retention value are obtained: the uncoated paper retains 1.1 ml of synthetic urine solution, the coated paper retains 18.5 ml. These figures show an essentially improved retention capacity.
Example 10 A creped paper having a weight of 25 g/m and a width of 30 cm is unwound from a supply roller and is applied without pressure to an endless pol~ester film that has a width of 40 cm, moves at a speed of 80 m/min, and is continuously sprayed with water. The film and the p~per thus wetted are ' .- : . ..
r778~3 guided through a 50 kv high voltage field. One electrode has the form of a screen and is filled with a carboxy methyl cellulose modified with the cross-linking agent dimethylol methylene bisacryl amide and having an average fibre length of 0.1 mm. The screen electrode is arranged at a distance of 25 cm from the paper. After the flocking~ the material passes through the area of an infrared radiator for drying and can then be wound up. The quantity of modified cellulose ether applied is 25 g/m .
Example ll A cotton-nettle cloth tissue having a weight of 150 to 170 g/m2 and a width of 50 cm is unrolled from a supply roller at a speed of 20 m/min, is wetted with water with the aid of a spray tube, and is then guided through a 60 kv high voltage field. The screen electrode is arranged at a distance of 35 cm from the paper and is filled with a carboxy methyl cellulose modified with N-methylol acrylamide, having an average fibre length of 0.2 mm. The quantity of modified cellulose ether flocked onto the material and still ~ present there after drying is 18 g/m2. The dried material can be wound up.
: ':
. .
The present invention relates to a process for the transformation of comminuted and modified cellulose ether swellable with water, into a material that may easily be further processed and may thus be used without difficulty, in particular, in the production of hygienic pads, napkins, bandagesg tampons, wrapping papers, insulating material, household papers and similar articles.
For the manufacture of such products, tissues or fleeces are used that can absorb a~ueous liquids, in particular physiological body fluids such as blood or urine. Cellulose in the form of tissues, bai~e, cotton wool or paper is mainly used. For a long time certain substances ha~e been added in order to increase the capacity of these articles to absorb aqueous liquidsO
For example moist potato flour, dextrine or gelatine have been applied to the cellulose material and dried as disclosed in German Patent NoO 489,309.
Recently it has become known to use cellulose ethers, which have been rendered at least largely water-insoluble by modification, for increasing the water absorption capacity of such materials. Modification is carried out with the cellulose material before, during or after the etherification of the cellulose. The etherification agent and the degree of etherification are ; chosen in such a manner that without modification a cellulose ether essen-` 20 tially soluble in water of 20C would be produced. By means of the modifi-cation the cellulose ether is rendered at least largely water-insoluble but is highly swellable with water. Processes for the manufacture of such modified ~ cellulose ethers are described in United States Patent Specifications Nos.
-~ 3,589S364 and 3,723,413. The cellulose ethers modified in this manner maintain :
their fibrous structure. This is done on purpose, in order to render possible further processing of the modified cellulose ethers obtained, either on their own or mixed with fibres of other cellulose material to form fibre fleeces, baize, bandages, cushions, napkins or tamponsO
Since the compounds mentioned abo~e are often in a fibrous state it ~ .
, , . . . , ~ ', ,: ~ : ,:. ; ' . , :
~1~77~8~3 is possible to transform them into flat-shaped articles, for example by suspending them in a wet process similar to that of paper production. However, the flat-shaped articles that can be produced in this manner have a rigidity similar to that of paper and are brittle, so that they can hardly be used in the hygienic field, e.g. in napkins or tampons.
In German Offenlegungsschrift No. 2,441,781 it has also been disclosed to fix modified cellulose ethers on textile areas by means of binders. The flat-shaped articles produced in this manner do have an increased absorption capacity towards liquids. However, this increased absorption capacity is low relative to the quantity of cellulose ether used, because the binder makes a portion of it ineffective. Furthermore, in this method the portion of binder may cause a hardening which is undesired, especially if the products are to be used as hygienic articles.
Thus the production of modified cellulose ethers and their further processing into useful objects were limited and further development in this technical field was hindered.
It is one object of the present invention to provide a process other than fleece-forming or baize-forming for transforming comminuted and ` modified cellulose ethers swellable with water into a material that can easily be further processed and may thus be used especially in the production of medical bandages, hygienic pads, napkins, tampons and similar articles.
By the present invention a coated web composed of a hydrophilic cellulose material is provided.
According to the present invention, there is provided a process for the transformation of comminuted cellulose ether, at least a major portion of which has been rendered water-insoluble by modification but which is still :! hignly swellable with wa~er, into an easily workable material, characterized - in that the co~minuted modified cellulose ether is attached to at least one ` surface of a web-shaped support composed of hydrophilic material and the ~` 30 support is then dried, the process further comprising the attaching of the modified cellulose ether to the support by means of electrostatic flocking ~B
~L~77788 or comprising the covering of the support, which is wetted with water, with a comminuted and modified cellulose ether, or comprising the coating of the support with a dispersion of the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent.
In another aspect oE the present invention, there is provided a coated web formed of a hydrophilic cellulose material characterized in that a comminuted and modified cellulose ether is attached to at least one surface of the hydrophilic cellulose material elther by means of electrostatic flocking or by covering said hydrophilic cellulose material, which is wetted with water, with a comminuted and modified cellulose ether or by coating the hydrophilic cellulose material with a dispersion of the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent.
The modified cellulose ethers usable in the process and included on the web are not only those having a fibrous structure, but they may have any form as long as they are comminuted, pourable, suspendible and electro-, statically flockable. Cellulose ethers in this state will hereinafter often be called powder, irrespective of the fact whether the particles are fibrous ~ crumbs of irregular shape or otherwise comminuted. The size of the particles ,;'..
'! iS of no decisive importance for the realisation of some embodiments of the invention. It may be 1 mm and more. In practice, however, it is mainly inthe range of from approximately 0.02 to 0.5 mm. Cellulose ethers are prefer-ably used that are modified by cross-linking according to the process described .
in German Offenlegungsschrift No. 23 57 079 or that are modified according to German Offenlegungsschrift No. 23 58 150. They are characterized by high ,. ., water absorption and water retention values. Modified cellulose ethers usable within the scope of the invention are also, for example, those given in German Patent No. 839,492, in United States Patent Specifications Nos. 3,589,364, 3,723,413 or 2,639,239~
These modifications of cellulose ethers lead to products having an acceptable water absorption capacity even if the modified cellulose ether still contains water-soluble parts. Thus in practice cellulose ethers are often not '.
'~
` ~977788 modified to form completely water-insoluble products, and in most cases the water-soluble parts are not removed from the modified cellulose ethers. The water-soluble portion may consist of those parts of cellulose ether which were not modified at all or of those parts which were not modified enough to become water-insoluble. A water-soluble portion of at least ' :
.1~., .
,: ,, :i ~
' ' -3a-~ .
~777~8 ;~
lS per cent by weight is advantageous in most cases, because it improves adhesion of the particles of modified cellulose ether to the hydrophilic web.
Howe~er, the water-soluble portion should not exceed approximately SO per cent by weight.
The hydrophilic web serving as a support preferably consists of a tissue, knit fabric or fleece or in particular of a paper composed of cellu-lose, wood pulp or synthetic fibres, especially a polyolefin fibre as described in German Offenlegungsschrift No. 21 17 370, or mixtures of them and has certain absorption and retention capacities towards liquids. The weight of this material is between 12 and 500 g/m2. .^~
In a preferred embodiment of the process according to the invention at least one surface of the web composed of hydrophilic material is wetted with water and is then covered with the comminuted modified cellulose ether.
The easiest way of wetting the surface of the support is to dip the web for a short moment into water and then squee&e it to the desired degree of mois-ture. The swellable powder is applied, for example, by strewing it onto the moist surface of the web, or in a vortex chamber.
In the process only those powder particles are attached-to the support that come into direct contact with the moist su~rface. The maximum amount of powder particles adhering to the surface is deter~ined by the number of particles that can lie closely side by side in one layer on the moist surface of the support. This highest density uill be used in those cases in which it is important to obtain a maximum water absorption capacity per unit of area. In this case more than the necessary amount of powder may be applied to the moist surface, since the excess powder can be easily re-moved, for example by blowing, and can then be reused. On the other hand, if maximum use is to be made of the water absorption capacity of the absorbent - powder, it is useful not to apply to the moist support more than 50 per cent by weight of the maximum amount of powder that can be applied according to the process of ~he in~ention. If the water-absorbing powder is to adhere ., ' ' , 9 . ,' ~77788 only to parts of the surface, for example if uncoated marginal areas or a coating according to a different pattern is required, it is useful to wet the surface of the web only in parts, i.e. according to the pattern desired7 e.g. by spraying it with water according to the pattern. The pattern desired may also be obtained by applying the powder to parts of the moist surface of the web. In this case the web surface or the whole web may be wetted, e.g.
by dipping it into water.
~n apparatus for carrying out the process described above consists mainly of the following devices:
a) a device for applying water to the web-shaped support, b) a device for applying the comminuted cellulose to the wetted surface and ~ c) a device for drying the coated support .,~. furthermore, a device for transporting the web-shaped support through the ~ devices a), b) and c) is necessary. The covering within the device b) may .~ be carried out in particular by powdering with the aid of a vibration screen :;, device or in a vortex chamber.
~,,;. ::
In device a), the web to be covered is passed, for example, through a vessel filled with water and is then squeezed by a squeegee roller to the :j 20 water content desired.
If the device b) for powdering the web is a vibration screen de-vice, usually only one side of the web is powdered, i.e. its upper surface.
If both sides are to be powdered, the web is, after being powdered on one side, deviated by a deviating roller for example, and is guided back into the device b) in such a manner that its bottom surface becomes its top sur-face. During this process the part of the web moving forward and the part moving backward must not be superposed. By means of the passing speed of the web and the way in which the screen is vibrated the powdering of the web surface can be controlled so as to apply more or less powder to it, as de-sired. If more powder is applied to the moist web surface than can adhere to it, the excess powder is removed from the web, is collected and is reused in another powdering process.
If the device b) for powdering is a vortex chamber, both surfaces of the moist web guided through it are covered with the powder whirled up by compressed air.
The drying device c) consists, for example, of drying drums around which the covered web is guided.
In another preferred embodiment of the process according to the invention the support is covered with a dispersion produced by dispersing the modified cellulose ether in an organic solvent, to which water may be added if necessary.
An alkyl hydroxyalkyl cellulose ether is preferably used as an unmodified cellulose ether. It should preferably have a ~iscosity of about 10 to 30,000 cP in a 2 per cent strength aqueous solution at 20C.
Preferably an alcohol such as methanol, ethanol, propanol-l, propanol-2, butano~-l, butanol-2, methyl propanol-l or methyl propanol-2, a ketone such as methyl ethyl ketone or diethyl ketone, a chloroderivative of methane such as methylene chloride or chloroform or especially mixtures of these solvents are used as the organic solvent in which the unmodified cel-lulose ether is dissolved or which is mixed with an aqueous solution of the unmodified cellulose ether at a ratio of 60 to 90 parts by weight to 40 to 10 parts by weight, preferably about 75 to 85 parts by weight to 25 to 15 parts by weight.
For the preparation of the suspension approximately 1 to 200 g/l, preferably 100 to 160 g/l of comminuted modified cellulose ether having a preferred average particle size of 0.02 to 0.25 mm are added to the solution of organic solvent and unmodified cellulose ether, to which water may be added if necessary, in such a manner that the suspension to be applied has a viscosity of 20 to 25 seconds, measured in a Ford measuring cup having a 4 mm die.
1~777~8 The web-shaped supports used for the application of the suspension may be wet-strength supports.
The coating of the support with the suspension is carried out in a coating device provided with a roller. The covering of the surface of the support by the layer may be incomplete, for example if the roller in the application device has a screen-shaped or punctiform surface structure (e.g.
in the case of a gravure printing roll). The quantity of suspension to be applied is determined such that after the coating about 0.5 to 50 g/m2 of the modified cellulose ether are on the support. ' In addition, a web-shaped hydrophilic material having the same composition as or a ccmposition similar to, the uncoated support may be laminated onto the coated side of the support.
In another preferred embodiment of the process according to the invention the modified cellulose ether is attached to the support by means of electrostatic flocking.
~ This electrostatic flocking and thus coating of the support is .~ effected by wetting at least one of its surfaces with water, for example by ;~J dipping, spraying or impregnating and guiding the still wet material through a high-voltage field of up to 100 ~v, preferably about 30 to 60 kv. One of the two electrodes which produce the high-voltage field has the shape of a screen or a perforated plate and serves the purpose of housing the modified cellulose ether, which prefera~ly consists of very short fibres having a length of from about 0.05 to 1 mm, advantageously about 0.05 to 0.3 mm, and does not require any particular preparation of the fibre or any antistatic aids. The width of mesh or the diameter of one perforation of the electrode is determined such that it is 60 to 100 times the diameter of the cellulose ether fibre. The counter-electrode is flat-shaped, and within the area of the high-voltage field it is not confined to its electrostatic use, but also s~rves, for example~ as a support for the material to be flocked that is guided between the two electrodes in such a manner that it is at a distance -- 7 _ 777~
of about 10 to 50 cm from the perforated or screen electrode and is close to the counter-electrode.
After having passed through the electric field the flocked material is dried, for example by a heat radiator or in a heating chamber and may then be wound up.
In the case of material having a low wet strength, like tissue paper for example, an endless belt able to support load may be used as an additional support between the storage roller and the wind-up roller, a belt which consists especially of a plastics film, a plastics grate or a metal net. This device is advantageously arranged in the area of the apparatus through which the wet material passes, i.e. the area between the wetting and drying areas.
In another embodiment of the latter process~ which is preferably , applied in the electrostatic flocking of material such as crepeA paper in order to maintain its original shape, e.g. the crepe, first an endless belt ,~
is wetted which then in turn wets the material to be flocked that comes into contact with the belt. Flocking and drying are carried out as described above.
The material to be flocked onto the support, which consists of ; 20 modified cellulose ether, is advantageously kept in motion by mechanical means, e.g. by slight vibration or a revolving scraper, in order to a~oid bridge-forming between its particles in the electrode, because this may im-pair the mobility of the flocks.
The cellulose ether particles are pushed from the screen electrode in the direction of the counter-electrode and thus also in the direction of the web-shaped support between the electrodes. They absorb water from the wet surface of the support and swell. The swelling preven-ts a pos`sible re-turn of the particles, which may be caused, for example, by charge reversion, and thus the support is uniformly covered with modified cellulose ether.
It is expected that during the drying that follows the swollen particles are glued to the support, thus ensuring good adhesion and preventing ~L~7778~3 the particles detaching themselves in the form of dust.
The process according to the invention may be carried out continu-ously as well as discontinuously, the density of the coating on the support being widely variable. It depends, for example, on the quantity of water applied, on the voltage applied to the electrodes, but also on the particle size of the modified cellulose ether to be flocked. The density may be up to 100 g/m2, in the case of material to be used for hygienic purposes it pre-ferably is 15 to 30 g/m2. ~
All the web-shaped materials produced according to the process of -the invention, especially according to its preferred embodiments, are highly ~ ;
absorbent and have a high liquid retention capacity. Since they are also easily workable it is advantageous to include them as a bottom, intermediate or top layer in flat-shaped laminar articles as they are used, for example, in the hygienic field in bandages, napkins or bed sheets, in order to improve their absorption capacity. The material produced according to the invention I may also be used as intermediate layers in flat-shaped articles ha~ing a ; "sandwich structure", for example dish-cloths, oil-absorbing mats and the like. ~-~xample 1 -.: .
A web of creped paper having a weight of 48.32 g/m2 is guided through water, as shown in the description, and after removing the water ad-hering to it is passed through a laboratory screen device. The modified car-boxy methyl cellulose to be applied, which is largely water-insoluble and has a water absorption capacity of 3800 g/100 g, is applied through an 0.2 mm screen, so that after drying the weight of the paper is increased by 42 g/m2 ~efore the powder mg the creped paper has an absorption capacity of 336 g per 100 g. Due to the powdering its water absorption capacity increases to 2012 g per 100 g of powdered paper. Its absorption capacity towards synthetic urine solution increases from 70 to 145 g and towards synthetic blood solu-tion from 71 to 127 g per 100 g of powdered paper (synthetic urine solution , _ g _ , ' : , , ', , ` ' ' ', ' 1 ~ ; ', ; 1 ;; "~ ~, , "~ ~ ~ " " ",, "~ "~" ,,, ; ; , " ~ , ;
777~
and synthetic blood solution are aqueous solutions the physical properties o~
which are very similar to human urine and blood).
Example 2 A tissue paper web having a weight of 23.6 g/m2 is wetted and powdered as described in Example l. After drying, its weight has increased by 52 g/m2. The water absorption capacity of the powdered tissue paper in-creases from 650 to 3000 ml per 100 g.
Example 3 A tissue paper web having a weight of 31.5 g/m2 is wetted and sub-sequently powdered on both surfaces as shown in the description. The moist web is deviated within the powdering chamber and dried only after the second powdering. The weight increase after drying is 4.7 g/m , and the absorption capacity increases from 800 to 1440 g of water per lO0 g of paper.
Example 4 A web of regenerated cellulose having a weight of 48 g/m is soaked with a 4 per cent strengbh aqueous glycerin solution, liquid adhering to it is removed, and one surface of the web is then powdered with a swellable cellulose ether in the powdering device shown in Example 1. After drying, its weight is 80 g/m , and its absorption capacity has increased from 200 to 2460 ml of water per lO0 g.
Example 5 After being wetted, a medical mull bandage having a width of 8 cm is powdered on one side with a cellulose ether which has a blood retention value of 980 ml/lO0 g, and after drying the weight of the bandage has in-creased by 20 per cent. Its blood retention capacity increases from 763 to 1298 ml per lO0 g of mull bandage.
Example 6 A tissue paper web having a weight of 31.5 g/m2 is powdered on one side, as described in Example 1, with a modified cellulose ether ~he water absorption capacity of which is 3800 ml per lO0 g, and its absorption cap-, ~137778~
acity towards a 1 per cent strength salt solution is 2000 ml per 100 g. The powdering density is increased to its maximum, i.e. 16 g/m2. The following results were obtained:
Absorption capacit:y per 100 g of material:
ml of 1% strength Material: NaCl solution ml of water tissue paper without powder 420 420 with 1~6 g/m of powder 600 750 with 3.2 g/m2 of powder 800 1440 with 8.0 g/m2 of powder 950 1S80 with 16 g/m2 of powder 1100 2000 powder 2000 3800 The results are shown in a diagram in Figure 1. It can be seen that the absorption capacity (coordinate), based on an increase in the amount of powder (abscissa) by 1 g, increases the more the less powder has been used on the whole and that when the maximum powder application of 16 g/m is ap-proached, the absorption capacity increases only insignificantly with an increase of 1 g in the powder quantity. It can also be seen that with half of the maximum powdering, i.e. 8 g/m , an absorption capacity towards dis-tilled water of 1580 ml per 100 g of web material is obtained, and an absorp-tion capacity towards a 1 ~er cent strength salt solution of 950 ml per 100 g of web material. Thus the maximum values of 2000 g and 1100 g per 100 g of web material are already approached.
Example 7 One side of a cellulose paper having a weight of 24 g/m2 is coated in a coating device provided with a roller and having a drying chamber and a suction device for removing solvent vapours~ The suspension to be applied is prepared from 200 ml of a two per cent strength aqueous solution of methyl hydroxy ethyl cellulose ether having a viscosity of 1,000 cP at 20C, oE
800 ml of aqueous isopropanol (87 per cent strength), and 100 g o:E particles ~77788 of a carbo~y methyl cellulose modified with the cross-linking agent bis-acrylamido acetic acid and having an average particle size of less than 0.2 mm. After drying more than 10 g/m2 of the modified cellulose ether are in the coating. The following example shows one of the purposes for which the coated paper may be used.
Example 8 2 ~ !
A sample of 100 cm size is cut out of a coated cellulose paper produced according to Example 7 and is immersed in water for 15 seconds. The water adhering to the surface after taking the paper out is removed by dabb-ing it with blotting paper, and then the sample is weighed. In its dry state it weighs 0 29 g and in its wet state 1.06 g, which means that it has absorb-ed 0.77 g of water. A sample of uncoated paper weighs 0.25 g in its dry state and 0.63 g in its wet state, i.e. it has absorbed 0.38 g of water. The absorption capacity of the paper coated according to the invention is thus about twice as high as that of the uncoated paper.
Example 9 A tissue paper having a weight of 18 g/m2 is coated as described in Example 7, and the quantity applied is 12.7 g/m . If samples of this coated paper and of uncoated paper each having a size of 1260 cm are dipped into a synthetic urine solution, each of them together with a filter paper sheet having the same si~e, and after 15 minutes are taken out and centrifuged in a laboratory centrifuge at 1,000 revolutions per minute, the following fig-ures for the liquid retention value are obtained: the uncoated paper retains 1.1 ml of synthetic urine solution, the coated paper retains 18.5 ml. These figures show an essentially improved retention capacity.
Example 10 A creped paper having a weight of 25 g/m and a width of 30 cm is unwound from a supply roller and is applied without pressure to an endless pol~ester film that has a width of 40 cm, moves at a speed of 80 m/min, and is continuously sprayed with water. The film and the p~per thus wetted are ' .- : . ..
r778~3 guided through a 50 kv high voltage field. One electrode has the form of a screen and is filled with a carboxy methyl cellulose modified with the cross-linking agent dimethylol methylene bisacryl amide and having an average fibre length of 0.1 mm. The screen electrode is arranged at a distance of 25 cm from the paper. After the flocking~ the material passes through the area of an infrared radiator for drying and can then be wound up. The quantity of modified cellulose ether applied is 25 g/m .
Example ll A cotton-nettle cloth tissue having a weight of 150 to 170 g/m2 and a width of 50 cm is unrolled from a supply roller at a speed of 20 m/min, is wetted with water with the aid of a spray tube, and is then guided through a 60 kv high voltage field. The screen electrode is arranged at a distance of 35 cm from the paper and is filled with a carboxy methyl cellulose modified with N-methylol acrylamide, having an average fibre length of 0.2 mm. The quantity of modified cellulose ether flocked onto the material and still ~ present there after drying is 18 g/m2. The dried material can be wound up.
: ':
. .
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the transformation of comminuted cellulose ether, at least a major portion of which has been rendered water-insoluble by modification but which is still highly swellable with water, into an easily workable material, characterized in that the comminuted modified cellulose ether is attached to at least one surface of a web-shaped support composed of hydrophilic material and the support is then dried, the process further comprising the attaching of the modified cellulose ether to the support by means of electrostatic flocking or comprising the covering of the support, which is wetted with water, with a comminuted and modified cellulose ether, or comprising the coating of the support with a dispersion of the modified cellulose ether in a solution of modified cellulose ether in an organic solvent.
2. A process according to claim 1, characterized in that a comminuted modified cellulose ether is used that contains more than 15 per cent by weight, but less than 50 per cent by weight, of water-soluble parts.
3. A process according to claim 1, characterized in that the comminuted modified cellulose ether attached to the web covers the web surface incompletely.
4. A process according to claim 1, characterized in that about 0.5 to 100 g/m , preferably up to 50 g/m , of the modified cellulose ether are attached to the web.
5. A process according to claim 1, characterized in that after the attachment of the modified cellulose ether the coated side of the web is additionally laminated with a web-shaped hydrophilic material.
6. A process according to claim 1, characterized in that a hydrophilic web material is used that consists of cellulose or a material containing cellulose.
7. A process according to claim 1, characterized in that only parts of the web surface are wetted with water.
8. A process according to claim 1, characterized in that the unmodified cellulose ether is an alkylhydroxyalkyl cellulose ether.
9. A process according to claim 1, characterized in that the unmodified cellulose ether has a viscosity of about 10 to 30,000 cP in a 2 per cent strength aqueous solution at 20°C.
10. A process according to claim 1, characterized in that an alcohol, a ketone, a chloroderivative of methane, or a mixture of these is used as the organic solvent.
11. A process according to claim 1, in which the modified cellulose ether is attached to the support by means of electrostatic flocking, characterized in that the modified cellulose ether used consists of fibers having an average length of 0.05 to 1 mm, preferably 0.05 to 0.3 mm.
12. A process as claimed in claim 6, wherein said hydrophilic web material is paper, tissue or regenerated cellulose.
13. A coated web formed of a hydrophilic cellulose material characterized in that a comminuted and modified cellulose ether is attached to at least one surface of the hydrophilic cellulose material either by means of electrostatic flocking or by covering said hydrophilic cellulose material, which is wetted with water, with a comminuted and modified cellulose ether or by coating the hydrophilic cellulose material with a dispersion of the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent.
14. A coated web according to claim 13, characterized in that the cellulose ether which would be essentially water-soluble without modification, is modified so as to become more than 50 per cent by weight and up to 85 per cent by weight water-insoluble.
15. A coated web according to claim 14, characterized in that the modification is effected by cross-linking.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2534358A DE2534358C3 (en) | 1975-08-01 | 1975-08-01 | Process for coating a tape made of hydrophilic material with powder made from a modified cellulose ether |
| DE2554558A DE2554558C3 (en) | 1975-12-04 | 1975-12-04 | Process for coating a tape made of hydrophilic material with powder made from a modified cellulose ether |
| DE2556723A DE2556723C3 (en) | 1975-12-17 | 1975-12-17 | Method and device for the electrostatic coating of a strip made of hydrophilic material with powder made of a modified cellulose ether |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077788A true CA1077788A (en) | 1980-05-20 |
Family
ID=27186480
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA258,212A Expired CA1077788A (en) | 1975-08-01 | 1976-07-30 | Process for the transformation of comminuted and swellable cellulose ether into an easily workable material |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS5219491A (en) |
| AT (1) | AT352896B (en) |
| AU (1) | AU503577B2 (en) |
| BR (1) | BR7604982A (en) |
| CA (1) | CA1077788A (en) |
| CH (1) | CH620586A5 (en) |
| DK (1) | DK344576A (en) |
| ES (1) | ES450319A1 (en) |
| FR (1) | FR2319434A1 (en) |
| GB (1) | GB1561705A (en) |
| IT (1) | IT1062646B (en) |
| LU (1) | LU75505A1 (en) |
| NL (1) | NL7608429A (en) |
| SE (1) | SE426079B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS50113331A (en) * | 1974-02-20 | 1975-09-05 | ||
| DE3141098C2 (en) * | 1981-10-16 | 1987-01-29 | Chemische Fabrik Stockhausen GmbH, 4150 Krefeld | Process for producing an absorbent material |
| US4650716A (en) * | 1985-05-14 | 1987-03-17 | Hercules Incorporated | Novel salts of carboxymethylcellulose |
| DE69518906T2 (en) * | 1995-04-11 | 2001-03-01 | Pantex S.R.L., Agliana | Material for the manufacture of sanitary napkins and absorbent articles made with this material |
| GB2314790A (en) * | 1996-07-01 | 1998-01-14 | William Graham Lamyman | Moisture absorbent covering means |
| US20200217018A1 (en) * | 2017-09-29 | 2020-07-09 | Essity Hygiene And Health Aktiebolag | Coreless roll of absorbent sheet and method for manufacturing the same |
| CN109030092A (en) * | 2018-10-24 | 2018-12-18 | 中国地质科学院水文地质环境地质研究所 | A kind of field pollen collecting device and pollen collecting and processing method |
-
1976
- 1976-07-28 AU AU16304/76A patent/AU503577B2/en not_active Expired
- 1976-07-28 CH CH966876A patent/CH620586A5/en not_active IP Right Cessation
- 1976-07-29 FR FR7623155A patent/FR2319434A1/en active Granted
- 1976-07-29 NL NL7608429A patent/NL7608429A/en not_active Application Discontinuation
- 1976-07-30 AT AT566076A patent/AT352896B/en not_active IP Right Cessation
- 1976-07-30 GB GB31922/76A patent/GB1561705A/en not_active Expired
- 1976-07-30 DK DK344576A patent/DK344576A/en unknown
- 1976-07-30 BR BR7604982A patent/BR7604982A/en unknown
- 1976-07-30 SE SE7608631A patent/SE426079B/en unknown
- 1976-07-30 IT IT50697/76A patent/IT1062646B/en active
- 1976-07-30 CA CA258,212A patent/CA1077788A/en not_active Expired
- 1976-07-30 ES ES450319A patent/ES450319A1/en not_active Expired
- 1976-07-30 LU LU75505A patent/LU75505A1/xx unknown
- 1976-08-02 JP JP51092256A patent/JPS5219491A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1561705A (en) | 1980-02-27 |
| JPS5219491A (en) | 1977-02-14 |
| NL7608429A (en) | 1977-02-03 |
| AT352896B (en) | 1979-10-10 |
| AU1630476A (en) | 1978-02-02 |
| SE426079B (en) | 1982-12-06 |
| ES450319A1 (en) | 1978-03-01 |
| AU503577B2 (en) | 1979-09-13 |
| BR7604982A (en) | 1977-08-09 |
| SE7608631L (en) | 1977-02-02 |
| ATA566076A (en) | 1979-03-15 |
| FR2319434B1 (en) | 1980-04-25 |
| DK344576A (en) | 1976-02-02 |
| FR2319434A1 (en) | 1977-02-25 |
| CH620586A5 (en) | 1980-12-15 |
| LU75505A1 (en) | 1978-02-09 |
| IT1062646B (en) | 1984-10-20 |
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