GB1561705A

GB1561705A - Articles comprising cellulose ethers and the manufacture thereof

Info

Publication number: GB1561705A
Application number: GB31922/76A
Authority: GB
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1975-08-01
Filing date: 1976-07-30
Publication date: 1980-02-27
Also published as: JPS5219491A; BR7604982A; CH620586A5; LU75505A1; ATA566076A; AT352896B; CA1077788A; AU1630476A; SE7608631L; FR2319434B1; ES450319A1; FR2319434A1; SE426079B; IT1062646B; NL7608429A; DK344576A; AU503577B2

Abstract

Small-particle cellulose ether which has become at least for the most part water-insoluble owing to modification but has remained highly swellable with water is converted into a material convenient for use. This entails the small-particle modified cellulose ether being attached at least on one side on a strip of hydrophilic material as substrate, and the latter being dried. The resulting strips are highly absorbent and show good fluid retention.

Description

(54) ARTICLES COMPRISING CELLULOSE ETHERS AND THE MANUFACTURE THEREOF (71) We, HOECHST AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany, of 6230 Frankfurt/Main 80, Postfach 80 03 20, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to articles comprising cellulose ethers and to a process for the transformation of comminuted, modified cellulose ether material that is swellable in water into a material that may be further processed relatively easily and which may conveniently be used in particular in the production of hygienic pads, napkins, bandages, tampons, wrapping papers, insulating material, household papers and similar articles.

For the manufacture of such products there are used tissues or fleeces that can absorb aqueous liquids, in particular physiological body fluids such as blood or urine. Cellulose in the form of tissues, baize, cotton wool or paper is mainly used. For a long time certain substances have been added in order to increase the capacity of these articles to absorb aqueous liquids. For example, moist potato flour, dextrine or gelatine have been applied to the cellulose material and dried (see German Patent No. 489 309).

It has been proposed to use cellulose ethers that have been rendered at least largely water-insoluble by modification for increasing the water absorption capacity of such materials. Modification may be carried out before, during or after etherification of the cellulose. The etherification agent and the degree of etherification are chosen in such a manner that without modification a cellulose ether essentially soluble in water at 20"C would be produced. By means of the modification the cellulose ether is rendered at least largely water-insoluble but is highly swellable in water. Processes for the manufacture of such modified cellulose ethers are described in U.S. Patent Specifications Nos. 3 589 364 and 3723 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 cellulosic material to form fibre fleeces, baize, bandages, cushions, napkins or tampons.

Because the cellulose substances mentioned above are often in a fibrous state it is possible to transform them into sheet-like articles, for example by suspending them in a wet process similar to that used for paper production. However, the sheet-like 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 hygiene field, e.g. in napkins or tampons.

German Offenlegungsschrift No. 24 41 781 discloses that sheet-like articles may be produced by attaching modified cellulose ethers to surfaces of textile webs by means of binders. The articles produced in this manner do have an increased absorption capacity for liquids. The absorption capacity is, however, low relative to the quantity of cellulose ether used, because the binder makes a portion of the cellulose ether ineffective. Furthermore, the binder may cause a hardening of parts of the cellulose ether which is undesirable, especially if the products are to be used in the hygiene field.

According to the present invention there is provided an article comprising a substrate comprising hydrophilic material and, adherent to and in direct contact with one or more surfaces of the substrate, particles of a water-absorbent modified cellulose ethers, which ether has been rendered at least largely water-insoluble by the modification.

The present invention also provides a process for the manufacture of such an article which comprises wetting one or more surfaces of the substrate and/or the particles of modified cellulose ether, applying the particles to at least one surface of the substrate and drying the resulting material. Wetting may be effected using water or a water-containing solution.

The modified cellulose ether materials usable in the article and process of the invention need not have a fibrous structure; they may have any form as long as they are comminuted and pourable and/or suspendible and/or electrostatically flockable. Cellulose ether materials in this state will hereinafter often be referred to as "Particles", irrespective of whether they are for example fibrous, particles 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 for example, be 1 mm or more.

In practice, however, it will usually be in the range of from approximately 0.02 to 0.5 mm. As the cellulose ethers, there are preferably used those that have been modified by cross-linking according to the process described in German Offenlegungschrift No. 23 57 079 or that are modified according to German Offenlgungsschrift No. 23 58 150. Those materials are characterized by high water absorption and water retention properties. Examples of other suitable modified cellulose ethers are given in German Patent Applications Nos. P 25 20 336.5, P 25 20 337.6 and P 25 19 927.3, in German Patent No. 839 492 and in U.S. Patent Specifications Nos. 3 589 364, 3723 413 and 2 639 239.

Modified cellulose ethers have an acceptable water absorption capacity even though they may still contain water-soluble portions. In practice, cellulose ethers are often not modified to form completely water-insoluble products, and in most cases the water-soluble portions are not removed from the product. The water-soluble portions 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 15 per cent by weight is advantageous in most cases because it improves adhesion of the particles of modified cellulose ether to the hydrophilic web. However, the water-soluble portion should not exceed 50 per cent by weight.

The substrate preferably comprises a web of material, e.g. a tissue, a knitted fabric or fleece, or in particular, a paper comprising cellulose, wood pulp or synthetic fibres, especially polyofelin fibres as described in German Offenlegungsschrift No. 21 17 370, or mixtures thereof that have adequate absorption and retention capacities for 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 substrate is wetted with water and is then covered with the comminuted modified cellulose ether. The easiest way of wetting the substrate is to dip it for a short time into water and then to squeeze it to such an extent that the desired amount of moisture is retained by the substrate. The particles are then applied by, for example, strewing them onto the moist surface (s) of the substrate or applying them in a vortex chamber.

In the process only those particles are attached to the substrate that come into direct contact with its moist surface s). The maximum amount of powder particles adhering to the surface(s) is determined by the number of particles that can lie closely side by side in one layer on the moist surface(s) of the substrate. This highest density will be used in those cases in which it is important to obtain a maximum water absorption capacity per unit surface area. In this case more than the maximum amount of particles may be applied to the moist surface(s) since the excess particles can be easily removed, for example by blowing off the excess and can then be reused. On the other hand as will be explained later very nearly maximum water absorption capacity of the particles (per unit area) may be obtained by using for example, about 50 per cent by weight of the maximum amount of particles that can be applied to the support. If the water-absorbing powder is to adhere only to parts of the surface(s) of the substrate, for example if uncoated marginal areas or a coating in a particular pattern is required, it is useful to wet only only a part or parts of the surface(s) of the substrate i.e. according to the pattern desired, e.g. by spraying it patternwise with water. The pattern desired may, alternatively be obtained by applying the powder patternwise to the moist surface(s) of the substrate. In this case all of the substrate surface(s) or the whole substrate may be wetted, e.g. by dipping it into water.

An apparatus for carrying out the process described above may comprise the following devices: a) a device for applying water to the substrate surface(s) b) a device for applying the comminuted cellulose to the wetted surface(s) and c) a device for drying the coated substrate as well as a device for transporting the substrate through the devices a), b) and c).

The covering within the device b) may be carried out in particular with the aid of a vibration screen device or in a vortex chamber.

In device a) the substrate is for example, passed through a vessel filled with water and is then squeezed by a squeeze roller to the desired extent.

The device b) may be a vibration screen device, in which case usually only one side of the support is covered, i.e. its upper surface. If both sides are to be covered, the support is, after being covered on one side, deviated, for example by a deviating roller and is guided back into the device b) in such a manner that its uncovered surface becomes its upper surface. During this process the part of the support moving forward and the part moving backward must not be superposed. The transport speed of the support through the device and the way in which the screen is vibrated can be controlled so as to apply the desired amount of particles to the support. If more particles are applied to the moist support surface than can adhere to it, the excess powder is removed from the support and may be collected and re-used in subsequent processes.

The device b) may, alternatively, be a vortex chamber, in which case both surfaces of the moist support guided through the chamber are covered with the particles which are whirled up by compressed air.

The drying device c) comprises, for example, one or more drying drums around which the covered support 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, in which there is dissolved an unmodified cellulose ether.

An alkyl hydroxyalkyl cellulose ether is preferably used as the unmodified cellulose ether and it preferably has a viscosity of 10 cP to 30,000 cP in a 2 per cent strength aqueous solution at 20 C.

An alcohol, for example methanol, ethanol, propanol-1, propanol-2, butanol-1, butanol-2, methyl propanol-1 or methyl propanol-2, a ketone, for example methyl ethyl ketone or diethyl ketone, a chloroderivative of methane, for example methylene chloride or chloroform or especially a mixture of one or more of these solvents is preferably used as the organic solvent in which the unmodified cellulose ether is dissolved optionally with the addition of water. The organic solvent is preferably present in a ratio of 60 to 90 parts by weight to 40 to 10 parts by weight of unmodified cellulose ether or aqueous solution thereof, more preferably 75 to 85 parts by weight to 25 to 15 parts by weight.

For the preparation of the dispersion approximately 1 to 200 g per litre, preferably 100 to 160 g per litre + of comminuted modified cellulose ether having a preferred average particle size of 0.02 to 0.25 mm are added to the solution of unmodified cellulose ether so that the suspension has a viscosity of from 20 to 25 seconds, measured in a Ford measuring cup having a 4 mm die.

The supports used for the application of the suspension may be wet-strength supports.

The coating of the support with the suspension may be 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 applied is preferably such that, after coating, about 0.5 to 50 g/m2 of the modified cellulose ether are on 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 may be effected by wetting at least one of the surfaces of the support with water, for example by dipping, spraying or immersing and guiding the wet material through a high-voltage field of up to 100 kv, preferably about 30 to 60 kv. One of the two electrodes which produce the high-voltage field preferably has the shape of a screen or a perforated plate and serves the purpose of housing the modified cellulose ether, which preferably consists of very short fibres having a length of from 0.05 to 1 mm, advantageously 0.05 to 0.3 mm, and which does not require any special preparation of the fibre, for example the application of 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 average diameter of the cellulose ether fibre. The counter-electrode is flat-shaped, and within the area of the high-voltage field it serves the purpose not only of an electrode but also for example, as a support for the support to be flocked, the latter being guided between the two electrodes in such a manner that it is at a distance 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 such, for example, as tissue paper, an endless belt able to support load may be used as an additional support between the storage roller and the wind-up roller. The belt may comprise especially a plastics film, a plastics grate or a metal net. The belt 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 a support comprising, for example, creped paper in order to maintain its origial shape, e.g. the crepe, first an endless belt is wetted and then the support is brought into contact with the belt whereby the support itself becomes wetted. Flocking and drying may then be carried out as described above.

The modified cellulose ether is advantageously kept in motion by mechanical means, e.g.

by slight vibration or a revolving scraper, in order to avoid bridge-forming between its particles in the electrode, because this may impair 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 support passing between the electrodes. The particles absorb water from the wet surface of the support and swell. The swelling prevents a possible loss of the particles from the support surface which may be caused, for example, by charge reversion, and thus the support is uniformly covered with modified cellulose ether. It is thought that, during the drying that follows, the swollen particles are "glued" to the support, thus ensuring good adhesion and preventing the particles detaching themselves in the form of dust.

The processes of the invention may be carried out continuously 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 (in the case of electrostatic flocking) and also on the particle size of the modified cellulose ether to be flocked. The density of modified cellulose particles on the support may be up to 100 g/m2 but in the case of material to be used for hygiene purposes it is preferably from 15 to 30 g/m2.

A web-shaped hydrophilic material which may have the same composition as or a composition similar to, the uncoated support may be laminated onto the coated side of the support. All the web-shaped materials produced by the process of the invention, especially by its preferred embodiments, are relatively 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 used, for example, in the hygiene field, for example in bandages, napkins or bed sheets, in order to improve the absorption capacity of such articles. The material produced according to the invention may also be used as intermediate layers in flat-shaped articles having a "sandwich structure", for example dish-cloths, oil-absorbing mats and the like.

The following Examples illustrate the invention Example 1 A web of creped paper having a weight of 48.32 g/m2 is guided through water in the manner hereinbefore described and after removing the excess water adhering to it is passed through a laboratory screen device. The modified carboxy methyl cellulose to be applied, which is largely water-insoluble and has a water absorption capacity of 3800 g/1()0 g, is applied through an 0.2 mm screen, so that after drying the weight of the paper is in-creased by 42 g/m2. Before application of the cellulose the creped paper has an absorption capacity of 336 g per 100 g. After application its water absorption capacity increases to 2012 g per 100 g of covered paper. Its absorption capacity towards synthetic urine solution increases from 70 to 145 g and towards synthetic blood solution from 71 to 127 g per 100 g of covered paper (synthetic urine solution and synthetic blood solution are aqueous solutions the physical properties of 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 has cellulose ether applied to it as described in Example 1. After drying, the weight of the web has increased by 52 g/m2. The water absorption capacity of the covered tissue paper increases from 650 to 3000 ml per 100 g.

Example 3 A tissue paper web having a weight of 31.5 gim2 is wetted and subsequently covered with cellulose ether on both surfaces using the device hereinbefore described. The moist web is deviated within the cellulose ether-application chamber and dried only after the second powdering. The weight increase (after drying) is 4.7 g/m2, and the absorption capacity increases from 800 to 1440 g of water per 100 g of paper.

Example 4 A web of regenerated cellulose having a weight of 48 g/m2 is soaked with a 4 per cent strength aqueous glycerin solution, excess liquid adhering to it is removed and one surface of the web is then coated with a swellable cellulose ether in the device described in Example 1. After drying, its weight is 80 g/m2, and its absorption capacity has increased from 200 to 2460 ml of water per 100 g.

Example SAfter bemg wetted, a medical mull bandage having a width of 3 cm is coated on one side with a cellulose ether which has a blood retention value of 980 ml/100g, and after drying the weight of the bandage has increased by 20 per cent. Its blood retention capacity increases from 763 to 1298 ml per 100 g of mull bandage.

Example 6 A tissue paper web having a weight of 31.5 g/m2 is coated on one side, as described in Example 1, with a modified cellulose ether the water absorption capacity of which is 3800 ml per 100 g. and the absorption capacity towards a 1 per cent strength salt solution of which is 2000 ml per 100 g.

The cellulose particle density is increased to its maximum i.e. 16 g/m2. The following results were obtained: Absorption capacity per 100 g of material ml of 1% strength ml of water Material: NaCl solution tissue paper without particles 420 420 with 1.6 g/m2 of particles 600 750 with 3.2 g/m2 of particles 800 1440 with 8.0 g/m2 of particles 950 1580 with 16 g/m2 of particles 1100 2000 Particles 2000 3800 These results are plotted in the accompanying drawing which is a graph of absorption capacity vs. the density of cellulose ether applied. It can be seen that the absorption capacity (plotted on the ordinate), against the density of particles (plotted on the abscissa) initially increases rapidly with increasing amount of applied particles but that when the maximum application of 16 g/m2 is approached, the absorption capacity increases only insignificantly with an increase of amount of applied particles. It can also be seen that, with half of the maximum amount of particles i.e. 8 g/m2, an absorption capacity towards distilled water of 1580 ml per 100 g of web material and an absorption capacity towards a 1 per cent strength salt solution of 950 ml per 100 g of web material are obtained. 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 gjm2 is coated with a suspension in a coating device provided with a roller and having a drying chamber and a suction device for removing solvent vapours. The suspension 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 20"C, of 800 ml of aqueous is opropanol (87 per cent strength), and 100 g of particles of a carboxy 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 contained in the coating.

Example 8 A sample of 100 cm2 area 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 surfaces of the sample after taking the paper out of the water is removed by dabbing it with blotting pauper, and then the sample is weighed. In its dry state it weights 0.29 g and in its wet state 1.06 g, which means that it has absorbed 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 coated paper 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 /m2. 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 size, and after 15 minutes are taken out and centrifuged in a laboratory centrifuge at 1,000 revolutions per minute, the following figures 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 markedly improved retention capacity.

Example 10 A creped paper having a weight of 25 g/m2 and a width of 30 cm is unwound from a supply roller and is applied without pressure to an endless polyester film belt 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 paper thus wetted are 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 is transported past an infrared radiator so as to dry the material which can be wound up. The quantity of modified cellulose ether applied is 25 g/m2.

Example 11 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 he 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 thereon after drying is 18 g/m2. The dried material can be wound up.

WHAT WE CLAIM IS: 1. An article comprising a substrate comprising hydrophilic material and, adherent to and in direct contact with one or more surfaces of the substrate, particles of a water-absorbent modified cellulose ether, which ether has been rendered at least largely water-insoluble by the modification.

2. An article as claimed in claim 1 wherein the modified cellulose ether contains from 15 to 50 per cent by weight of water soluble material.

3. An article as claimed in claim 1 or claim 2 wherein the cellulose ether has been modified by cross-linking.

4. An article as claimed in any one of claims 1 to 3 wherein the or each surface of the substrate is covered incompletely by the particles of modified cellulose ether.

5. An article as claimed in any one of claims 1 to 4 wherein the particles of modified cellulose ether are present on the or each surface at a density of from 0.5 to 100 g/ square metre of surface.

6. An article as claimed in claim 5 wherein the density is up to 50 g per square metre of surface.

7. An article as claimed in any one of claims 1 to 6 wherein the particles of modified cellulose ether comprise fibres.

8. An article as claimed in claim 7 wherein the fibres have an average length of from 0.02 to 1 mm.

9. An article as claimed in claim 8 wherein the fibres have an average length of from 0.05 to 0.3 mm.

10. An article as claimed in any one of claims 1 to 9 wherein the substrate is a web of material.

11. An article as claimed in any one of claims 1 to 10 wherein at least one substrate surface having particles of modified cellulose ether thereon is laminated with a layer of hydrophilic material.

12. An article as claimed in any one of claims 1 to 11 wherein the substrate consists of cellulose or a material containing cellulose.

13. An article as claimed in claim 12 comprising cellulosic paper or tissue or regenerated cellulose.

14. An article as claimed in claim 1 substantially as described in any one of the Examples herein.

15. A liquid-absorbent article comprising an article as claimed in any one of claims 1 to 14.

16. A liquid-absorbent article as claimed in claim 15 which is a hygienic pad, napkin, bandage or tampon.

17. A process for the manufacture of an article as claimed in claim 1, which comprises wetting one or more surfaces of the substrate and/or the particles of modified cellulose ether, applying the particles to at least one surface of the substrate and drying the resulting material.

18. A process as claimed in claim 17 wherein wetting is effected using water or a water-containing solution.

19. A process as claimed in claim 17 or claim 18 which comprises wetting one or more surfaces of the substrate, applying dry particles of modified cellulose ether to one or more of said surfaces and drying the resulting material.

20. A process as claimed in claim 19 wherein only a part of the or each surface is wetted.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 10 A creped paper having a weight of 25 g/m2 and a width of 30 cm is unwound from a supply roller and is applied without pressure to an endless polyester film belt 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 paper thus wetted are 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 is transported past an infrared radiator so as to dry the material which can be wound up. The quantity of modified cellulose ether applied is 25 g/m2. Example 11 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 he 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 thereon after drying is 18 g/m2. The dried material can be wound up. WHAT WE CLAIM IS:

1. An article comprising a substrate comprising hydrophilic material and, adherent to and in direct contact with one or more surfaces of the substrate, particles of a water-absorbent modified cellulose ether, which ether has been rendered at least largely water-insoluble by the modification.

21. A process as claimed in claim 17 wherein the particles of modified cellulose ether

are dispersed in a solution of an unmodified cellulose ether in an organic solvent, one or more surfaces of the substrate is or are coated with the dispersion and the resulting material is dried.

22. A process as claimed in claim 21 wherein said organic solvent contains water.

23. A process as claimed in claim 21 or claim 22 wherein the unmodified cellulose ether is an alkylhydroxylalkyl cellulose ether.

24. A process as claimed in any one of claims 21 to 23 wherein the unmodified cellulose ether has a viscosity of from 10 cP to 30,000 cP in a 2 per cent aqueous solution at 20"C.

25. A process as claimed in any one of claims 21 to 24 wherein the organic solvent is an alcohol, a ketone, a chloroderivative of methane or a mixture of two or more of these classes of compounds.

26. A process as claimed in claim 19 or claim 20 wherein the particles of modified cellulose ether are applied by electrostatic flocking.

27. A process as claimed in claim 17 carried out substantially as described in any one of the Examples herein.

28. An article whenever manufactured by a process as claimed in any one of claims 17 to 27.