FI65731C - FOERFARANDE FOER BELAEGGNING AV ETT HYDROFILT BAND MED EN MODIFIERAD CELLULOSAETER - Google Patents

Description

ESSr * l M (11) NOTICE OF PUBLICATION, ro 7 1 ij t ^ utlAggni ngsskmpt 65/31 C Patent granted 10 07 1934 “Patent meddelat ^ '(51) K» .lk? /Lnt.CL3 B 32 B 5/22, A 6l F 13/16 // B 05 0 1/16, A 61 L 15/00, D 01 H 1 / ½ FINLAND —FINLAND (21) PiH ^ liaMw.h («mMalinln | 762188 (22) H» k «Ml» p * lY «- AmMcntogadag 30.07.76 '(23) Alkupa) * - Glltl | h« t * d «| 30.07.76 (41) Tullut lulklMlul - ftllvlt offwteMf 02.02 77

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Patent and register authorities Amekwi uthfd och uti ^ krMUn pubUcund 30.03.8¾ (32) (33) (31) fyrfuttjr utuolkeu · IqW prlorltuc o 1.08.75 17.12.75 Federal Republic of Germany-Förbunds-republiken Tyskland (DE) P 253 ^ 35 P 2556723.1 (71) Hoechst Aktiengesel1schaft, Postfach 80 03 20, 6230 Frankfurt (Main) 80,

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (72) Arno Hoist, Wiesbaden, Helmut task, Wiesbaden, Ludwig Grosse, Taunusstein, Hans-Werner Dorr, Wiesbaden, Ehrenfried Nischwitz, Schmitten, Klaus Uhl, Neotashain, Neuenhain ) (7¾) Oy Koister Ab (5¾) Method for coating a hydrophilic strip with a modified cellulose ether - Förfarande för beläggning av ett hydrophililt band med en modifierad cellulosaeter

The invention relates to a coating process for converting hay-splitting, water-swellable and modified cellulose ether into a material which is easy to process and thus easy to use in the manufacture of sanitary napkins, caps, wound dressings, tampons, packaging papers, special agents, kitchen papers and the like.

More particularly, the invention relates to a method of coating a strip of hydrophilic material and a fabric, knitted nonwoven or paper based on cellulose or cellulosic material with a finely divided cellulose ether which, due to modification, has become partially water-insoluble but has become partially water-insoluble.

In the manufacture of the above products, a tissue or nonwoven fabric capable of absorbing aqueous fluids and in particular also physiological secretions such as blood and urine is used.

2,65731 Cellulose is mainly used in the form of tissue, spunbond, wadding or paper. In this case, certain substances have long been added to improve the water absorption of these products. For example, moist potato flour, dextrin and gelatin have been added to the cellulosic material and dried (DE patent 489,309).

Today, cellulose ethers are used to improve the water absorption of such materials, which by modification have been made at least for the most part insoluble in water. The modification of the cellulosic material takes place before, during or after the etherification of the cellulose. The etherifying agent and the degree of etherification are chosen so that, without modification, a cellulose ether which is substantially soluble in water at 20 ° C is formed. By modifying this, at least for the most part it becomes insoluble in water, but swells strongly in water. Methods for preparing such modified cellulose ethers are described in U.S. Patent Nos. 3,589,364 and 3,723,413. The cellulose ethers so modified retain their fiber form. This is also intended so that the resulting modified cellulose ethers can be processed as such or in admixture with other cellulose fibers into a nonwoven fabric or spun fibers and further into bandages, pads, caps and tampons.

Since said compounds are often fibrous, it is possible, for example, to make surface textures from them through a pulp, such as papermaking. However, these are paper-like rigid and also brittle, so their handling is a use especially in the field of hygiene, e.g. in paws and sanitary napkins, is hardly possible.

DE-A-2 441 781 already describes the attachment of modified cellulose ethers to textile surfaces by means of binders. Although the liquid absorbency of the surface structures thus prepared is improved, it is small in relation to the amount of cellulose ether used because the binder renders part of it ineffective.

In addition, in this method, the binder often causes curing, which is not desirable, especially in hygiene products.

Thus, limits had been set for the preparation of modified cellulose ethers and their preparation as useful products, which hindered the further development of this technique.

It is an object of the present invention to provide a method of converting finely divided, water-swellable and modified cellulose ether other than through fibrillated fibers into a material which is easy to process and thus easily suitable for the manufacture of wound dressings, sanitary napkins, dressings, tampons and the like.

The invention is characterized in that a finely divided cellulose ether having a water-insoluble content of more than 15% by weight but less than 50% by weight is attached to at least one side of the strip substrate, a) at least one surface of the strip is moistened with water and the moistened surface is coated with finely divided with cellulose ether, or b) dispersing the modified cellulose ether in a solution of unmodified cellulose ether in an organic solvent, optionally by adding water, and coating the substrate with the dispersion, or c) attaching the modified cellulose ether to a moist substrate by electrostatic drying, followed by coating.

The cellulose ethers useful in the process and on the strip are not only fibrous, but rather may be in finely divided form, especially in a free-flowing, suspending and electrostatically fluffable form. In the following, these forms are often referred to as powder, whether fibrous, irregularly crumbly, or otherwise finely divided. In many embodiments of the invention, the maximum particle size is not critical and may be 1 mm or more. But in practice the particle size is mainly about 0.02-0.5 mm. Cellulose ethers modified by crosslinking according to the method of DE-A-2 358 150 are preferably used. They are characterized by a high water suction and retention capacity. Modified cellulose ethers useful in the context of the invention are also described in DE-A-2 520 336.5, 2 520 337 and 2 519 927, DE-A-839 492, US-A-3589 364, 3723 413, 2639 239.

Even these cellulose ether modifications result in products with useful water absorbency when water-soluble moieties remain in the modified cellulose ether mass. The process according to the invention uses cellulose ethers which have not been modified into completely water-insoluble products and water-soluble portions 4 65731 had not been removed from the modified cellulose ether pulps.

In this case, the water-soluble portion may consist of cellulose ether portions to which the modification did not extend or cellulose ether portions which have been modified so little that they have not become a water-insoluble product. A water-soluble portion of at least 15% by weight is necessary because the adhesion of the modified cellulose ether particles to the hydrophilic strip is improved. However, the water-soluble fraction must not exceed 50% by weight.

The hydrophilic strip serving as a substrate consists of a fabric, a knitted nonwoven fabric and in particular a paper made of cellulose, wood chips, synthetic fibers, in particular polyolefin fibers described in e.g. DE-A-2 117 370, or mixtures thereof and has a liquid absorption and 2 retention capacity. Such a material generally has a basis weight of 12-50 g / m 2.

In one embodiment of the method according to the invention, at least one half of the strip made of hydrophilic material is moistened with water and the moistened surface is coated with a fine, modified cellulose ether. The wetting of the substrate surface is most simply done by briefly immersing the strip in water and pressing the strip to the desired degree of humidity. Coating with a swellable powder takes place, for example, by sprinkling the powder on a moist strip surface or in a fluidized chamber.

In the method, only those powder particles adhere to the substrate that come into direct contact with the wet surface. Thus, only as many powder particles adhere to the surface as can be transferred to the moist surface of the substrate as a denser layer. This densest layer is used in cases where it is desired to obtain maximum water absorption per unit area. More than the required amount of powder can be added to the wet surface, as the excess can be easily removed, e.g. by blowing.

The powder can be reused. However, if it is desired to make the most of the water uptake capacity of the absorbent powder, it is best to attach up to 50% by weight of the powder to a moist substrate, which can then be attached to the maximum by the method 5 65731 according to the invention. If it is desired to attach the water-absorbent powder only in places to the substrate, e.g. if necessary uncoated edge portions or a coating of a different pattern, it is most suitable to moisten the strip surface only in places, i. according to the desired pattern, e.g. by spraying water in question. according to the pattern. The desired coating pattern can also be obtained by coating the wet strip surface with the powder only in places. In this case, the strip surface or the strip as a whole is moistened, for example, by immersion in water.

An apparatus for carrying out the described method consists of the following main parts: a) an apparatus for applying water to a strip substrate, b) an apparatus for coating a wetted surface with finely divided cellulose ether, and c) an apparatus for drying the coated substrate in said order and conveying the strip substrate via devices a, b and c.

In particular, the coating in the device b can take place by applying the powder in a vibrating screen machine or in a fluidized chamber.

In the device a, the strip to be coated passes, for example, in a tank filled with water and the pressing rolls are pressed to the desired water content.

If the belt powder applicator b is a vibrating screen machine, the powder is applied in the usual way only to the other side of the belt, i.e. above or below. If it is desired to coat both sides, the strip is returned to the device b after being coated on one side, e.g. by means of a turning roller, whereby the recent underside becomes the upper side. In this case, the reciprocating strips do not have to be aligned. With the speed of the belt and the vibration mode of the screen, the coating of the belt surface with powder can be adjusted so that more or less powder is spread as desired. If an excess of powder has been sprinkled, i.e. more than can adhere to the wet tape surface, the excess is removed from the tape, recovered and reused.

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If the powder applicator b is a fluidized chamber, the strip passing therethrough is coated on both sides as a compressed air-powder mixture with a floating powder.

The drying device c consists, for example, of a drying drum around which the belt is wound.

In another embodiment of the process of the invention, the substrate is coated by dispersing the modified cellulose ether, optionally with the addition of water, in a solution of unmodified cellulose ether in an organic solvent, and the substrate is coated with this dispersion.

As the unmodified cellulose ether, alkylhydroxyalkylcellulose ether is especially used. Preferably, the viscosity of the cellulose ether as a 2% aqueous solution at 20 ° C is 10-30,000 cP.

As the organic solvent in which the unmodified cellulose ether is dissolved or in which an aqueous solution of the unmodified cellulose ether is mixed in a ratio of 60 to 90 parts by weight to 40 to 10 parts by weight, preferably 75 to 85 parts by weight to 25 to 15 parts by weight, an alcohol, e.g. methanol, is used. , ethanol, propanol-1, propano-ia-2, butanol-1, butanol-2, methylpropan-1-ol, or methyl propan-2-ol, ketone, e.g. methyl ethyl ketone or diethyl ketone, methane chlorine derivative , e.g. methylene chloride or chloroform and in particular mixtures of these solvents.

To a solution of the organic solvent and the unmodified cellulose ether, optionally containing water, is added to prepare a suspension of about 1-200 g / l, preferably 100-160 g / l of modified cellulose ether in fine form, preferably 0.02 to 0.25 mm in diameter, so that the coating suspension In a Ford cup, nozzle 4 mm, the measured viscosity is preferably 20-25 seconds.

The tape substrates used in the suspension coating may be wet strength or non-wet strength.

The coating of the substrate with the suspension takes place in a roll coating device. The layer can also incompletely cover the substrate surface, e.g. when the surface of the coating equipment rolls is raster or dot patterned (e.g. in gravure rolls). The amount of coating of the suspension is adjusted so that after coating the substrate contains about 0.5 to 50 2 g / m of modified cellulose ether.

65731

In addition, a strip-like, hydrophilic material that is the same or different from the uncoated substrate can be laminated to the coated side of the substrate.

In yet another embodiment of the method of the invention, the modified cellulose ether is electrostatically attached to the substrate.

This electrostatic flocculation and thus the coating of the substrate takes place by wetting at least one surface of the substrate with water, e.g. by immersing, spraying or impregnating and conveying the moist material through a high voltage field with a voltage of up to 100 kV, preferably about 30-60 kV. In this case, one of the two electrodes which generate a high voltage field comprises a screen or a perforated plate. Its function is to receive a modified cellulose ether, which is preferably very short fibers with a fiber length of about 0.05 to 1 mm, preferably about 0.05 to 0.3 mm. No special fiber preparation or antistatic aids are required. The mesh size or hole diameter of the electrode is selected to be about 60-100 times larger than the fiber diameter of the cellulose ether. The counter electrode is plate-like and its function is to operate in the high-voltage field in addition to its electrostatic function, e.g. as a support for the material to be flattened, which material is fed between the two electrodes so that it is at a distance of about 10-50 cm from the torn electrode and in the immediate vicinity of the counter electrode.

The fluffed material that has passed through the electric field can be dried, for example, with a heat radiator or in a heat duct, and finally it can be wound on a roll.

Materials with low wet strength, such as tissue paper, can be further supported between roll removal and roll winding devices by a load-bearing, endless belt, preferably made of plastic film, plastic mesh or metal mesh. Preferably, the belt is in the region of the device through which the moist material passes, i. between the wetting and drying zone.

In a further embodiment of the latter method, which is preferably used electrostatically for flotation, e.g. crepe paper, in order to preserve the original shape, e.g. Fluffing and drying take place as above.

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Preferably, the flocculated, modified cellulose ether material is kept mechanically agitated, e.g., by lightly vibrating or with a rotating scraper, so that its particles do not come into bridge contact at the electrode, which impairs the mobility of the fluff.

The hole electrode pushes the cellulose ether particles in the direction of the counter electrode and thus adheres to the strip substrate therebetween, where they absorb water from the moist surface and swell.

The latter phenomenon causes the particles to be able to travel in the opposite direction, e.g. when the charge changes, and thus the substrate is coated very evenly with the modified cellulose ether. It is assumed that in the final drying, the swollen particles adhere together, thus achieving dust-free and good adhesion of the coating material.

The method according to the invention can be implemented both continuously and in batches, whereby the density of the coating on the substrate can be varied within wide limits. It depends on e.g. the amount of water and electrode voltage used, but also the particle size of the flocculated, modified cellulose ether. The coating density can be at most about 100 g / m and the material used in the hygiene range about 15-50 g / m.

All the tape-like materials prepared according to the method of the invention are highly absorbent and, in addition, have good fluid retention. In addition, since they are easy to process, they can be very advantageously added to planar layered products, e.g. sanitary napkins, pads or bedding as lower, intermediate or upper layers, to have a positive effect on the absorbency. The layers prepared according to the invention can also be used as intermediate layers in "sandwich" structures, e.g. wet wipes (household towels), oil absorbent blankets and the like.

Example 1 2

The crepe paper web, 48.32 g / m 2, was drawn through water as described above, and after wiping the stuck water, it was drawn through a laboratory vibrating screen. The coated, mostly water-insoluble, modified carboxymethylcellulose, 3800 g / 100 g water absorption, was sprinkled through a 0.2 mm sieve so that, after drying, the basis weight of the paper had increased to 42 g / m 2. Prior to coating, the maximum absorption (absorbency) of crepe paper 9,65731 was 336 g / 100 g. By coating, the water absorption increased to 2012 g / 100 g of coated paper. The absorbency increased from 70 g to 145 g with the synthetic urine solution and from 71 g to 127 g per 100 g of coated paper with the synthetic blood solution. Synthetic urine or blood solution are aqueous solutions that are very similar in physical properties to human urine or blood.

Example 2 2

Tissue paper tape, basis weight 23.6 g / m 2, was moistened and sprinkled with powder as described in Example 1. After drying, the basis weight was 52 g / m 2. The water absorbency of the coated tissue paper increased from 650 ml to 3000 ml per 100 g.

Example 3 2

Tissue paper tape, basis weight 31.5 g / m 2, was moistened and powdered on both sides as described above. In this case, the moist strip was turned over in the spraying space and dried only after the second spraying. After drying, the basis weight was 4.7 g / m 2 and the water absorbency increased from 800 g to 1440 g per paper.-

Example 4

A gauze bandage, 8 cm wide, was moistened and sprinkled on one side with cellulose ether with a blood retention value of 980 ml / 100 g. After drying, the weight gain was 20% by weight. Blood retention increased from 763 ml to 1298 ml per 100 g of gauze.

Example 5 2

On one side of a tissue paper having a basis weight of 31.5 g / m 2, modified cellulose ether was sprinkled as described in Example 1, having a water absorption of 3800 ml and a 1% saline solution having an absorbency of 2000 ml per 100 g of strip material.

The coating density changed up to a maximum powder uptake of 2 was 16 g / m 2. The results were as follows: 10,65731

Absorbency / 100 g substance _Material_ml 1% NaCl solution ml water

Tissue paper without powder 420 420 + 1.6 g / m ^ powder 600 750 + 3.2 g / m ^ powder 800 1440 +8.0 g / m ^ powder 950 1580 + 16 g / m ^ powder 1100 2000 powder 2000 3800

The results are shown in Figure 1 as curves. It is observed that the lower the total amount of powder used, the greater the total amount of powder used increases as the amount of powder (abscissa) increases by 1 g, and that as the maximum powder space approaches 16 g / m, the increase in absorbency is negligible as the amount of powder increases by 1 g. It is also observed 2 that in the middle of the maximum amount of coating, i.e. 8 g / m, an absorbency of 1580 ml of distilled water and 950 ml of 1% saline per 100 g of binder is already achieved, which is very close to the maximum of 2000 ml and 1100 ml per 100 g: aa towards the tape material.

Example 6 2

One side of the cellulosic paper, basis weight 24 g / m 2, was coated in a roll coater equipped with a drying channel and a solvent vapor vacuum. The coating suspension was prepared from 200 ml of a 2% by weight aqueous solution of methylhydroxyethylcellulose ether, a viscosity at 20 ° C of 1000 cP, 800 ml of an 87% aqueous solution of isopropanol and 100 g of crosslinked bisacrylamidoacetic acid average diameter less than 0.2 mm. After drying, the coating contained more than 10 g / m of modified cellulose ether. The following example shows one use of coated paper.

Example 7

The coated cellulosic paper prepared in Example 6 was cut into a 100 cm specimen and held in water for 15 seconds. After taking the water, the water adhering to the surface was dried with absorbent paper and the test piece was weighed. It weighed 0.29 g when dry and 1.0 g when wet and had thus absorbed 0.77 g of water. The uncoated paper test piece weighed 0.25 g dry and 0.63 g wet and thus had absorbed 0.38 g of water. Thus, the absorbency of coated paper according to the invention is about twice that of uncoated paper.

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Example 8

Tissue paper, basis weight 18 g / m 2, was coated as described in Example 26 at an amount of 12.7 g / m 2. When test pieces of this coated and uncoated paper, each having an area of 2,1260 cm, and a sheet of filter paper of the same size were immersed in synthetic urine and the liquid was removed by suction for 15 minutes in a laboratory centrifuge at 1000 rpm, the following values were obtained: 1.1 urine solution and coated paper 18.5 ml. Thus, the retention capacity had improved considerably.

Example 9 2

The crepe paper, 25 g / m 2 and 30 cm wide, was allowed to run unrolled on a 40 cm wide polyester film which was continuously sprayed with water and moved endlessly at a speed of 80 m / min. The film and the paper thus moistened were introduced into a 50 kV high-voltage field in which the second electrode is screen-like and filled with a crosslinking agent with dimethylolmethylenebisacrylamide-modified carboxymethylcellulose, average fiber length 0.1 mm. The distance of the screen electrode from the paper was 25 cm. At the end of the fluff, the material was dried in infrared radiation and wound on a roll. The amount of coating of the modified cellulose ether was 25 g / m 2.

Example 10 2

A cotton nettle fabric, basis weight 150-170 g / m and width 50 cm, was run from a roll at a speed of 20 m / min, moistened with water under a spray tube and transported through a 60 kV high voltage field. With N-methylolacrylamide-modified carboxymethylcellulose, average fiber length 0.2 mm, the distance of the filled screen electrode from the paper was 35 cm. The amount of modified cellulose ether coating on the fluffed and dried material 2 was 18 g / m 2 and the material could be wound on a roll.

Claims (9)

A method of coating a strip of a hydrophilic material and the fabrication of fabric, knitwear, nonwoven or paper on the basis of cellulose or a cellulose containing material with a finely divided cellulose ether which, by modification, has become partially soluble in water, but has nevertheless remained strongly swellable by the action of water, characterized in that finely divided modified cellulose ether, in which the water-insoluble proportion exceeds 15% by weight, but still below 50% by weight, is adhered to at least one side of the web substrate, where a) one band surface is moistened with water and the wetted surface is coated with the finely divided modified cellulose ether or b) the modified cellulose ether is dispersed in a solution of unmodified cellulose ether in an organic solvent, optionally by adding water, and the substrate is coated with dispersion the modified cellulose ether is adhered to the moist substrate by electrostatic flocculation, where fter the coated tape is dried. A method according to claim 1, characterized in that the finely divided modified cellulose ether adhered to the tape only partially covers the tape surface. 3. A process according to claim 1 or 2, characterized in that the strip is coated at about 0.5-100 g / m, preferably at most 50 g / m of modified cellulose ether. 4. A process according to any of claims 1-3, characterized in that after the modified cellulose ether is adhered to, on the coating side of the coated band, a further band of a hydrophilic material is laminated. Process according to any of claims 1-4, characterized in that in the embodiment a) the strip surface is moistened with water only occasionally. Process according to any one of claims 1-4, characterized in that the unmodified cellulose ether at