EP0076888A2 - Absorbent flat product, and process for its manufacture - Google Patents

Abstract

An absorbent fabric interspersed with pores, a so-called “sponge cloth”, is proposed. The sponge cloth consists of a latex-bonded fiber material and optionally contains a reinforcement layer. The manufacturing process does not use conventional pore formers. The foam is formed using a gaseous medium and stabilized by drying and by vulcanization.

Description

The invention relates to an absorbent fabric interspersed with pores made of a latex-bonded fiber material, which optionally contains a reinforcement made of woven, knitted, foam, nonwoven or abrasive nonwoven.

Such fabrics are used in particular as a household cloth and are referred to as "sponge cloths" because of their absorbency. Sponge cloths are available in different designs. The most common is the viscose sponge cloth, while Gumni or polyurethane sponge cloths have no practical significance. In addition to the sponge cloths, sponges and window cloths made of cross-linked polyvinyl alcohol are used to a small extent. All of the products described above, in particular the crosslinked polyvinyl alcohol-containing cloths or sponges, are hard and brittle when dry.

The so-called viscose sponge cloth is the most common. It often contains a fabric to increase tear resistance. Since the viscose sponge cloth is hard and brittle when dry, you have to impregnate with a diluted softening solution, e.g. Glycerin, suggested. While the viscose sponge cloth cannot withstand any mechanical stress in the absolutely dry state without this plasticizer additive and absorbs about 10% moisture when air-conditioned, the moisture absorption in a "softened" cloth is about 20%. In practical use, where the cloth dries only by leaving it lying around, a cloth that is subjectively perceived as dry still contains at least 15 to 20% moisture, which is sufficient to not let the cloth become completely brittle. Despite the softening, however, a soft, comfortable grip is still not achieved and the swelling of the material cannot be eliminated with certainty. So the cloth bulges when drying mainly at the corners, so that there is no more flat support. For these reasons, the viscose sponge cloth is usually packed moist, which is not hygienically harmless, because bacterial and fungal attack must always be expected, unless bactericides and fungicides are additionally used.

The "softening" with glycerin or other water-soluble substances is also perceived as very disadvantageous because the "Softeners" are washed out during use, so that the initially soft sponge cloths become hard and boardy again when dry. In the known viscose sponge cloths, the advantage of the high suction speed and the high water absorption as well as the pleasant grip in the moist state is offset by the disadvantage that there is only a low durability, especially on the surface. When used, wiping to dryness is not possible and despite the packaging with plasticizers, the cloth is hard and boardy again after a while in a dry state. The risk of bacteria and fungi colonizing must always be taken into account. Production using the known cellulose xanthate process results in a greater or lesser environmental impact.

The invention is based on the object of developing an absorbent fabric which, with high water absorption and good suction speed, does not have the known disadvantages of the viscose sponge cloth. The cloth should be soft and pleasant to the touch, especially when dry, and should not show any bacteria or fungi. The use of plasticizers, pore formers or similar substances that interfere with use and change the properties of the cloth during use should be avoided. The object of the invention is also the development of an environmentally friendly method for producing the novel "sponge cloths".

The object of the invention is achieved by the absorbent sheet material described in the claims and by the method for its production, which is also specified.

The absorbent sheet according to the invention contains a hydrophilic fiber material which is latex-bonded and interspersed with essentially open pores. For reinforcement, it is advisable to use a woven, knitted fabric, a foam or a nonwoven that is on one or both sides with the latex-bound fiber material is coated. In the case of one-sided coating, the nonwoven fabric can also contain mineral abrasives, so that the nonwoven fabric side has an abrasive effect.

The fiber material consists of a mixture of hydrophilic staple fibers of different lengths and optionally fiber dust, cellulose, wood pulp, linters or the like. To increase the mechanical resistance, hydrophobic staple fibers made of synthetic material can be added as an admixture. The chamfer mixture is embedded in an open-pore foam, which suitably consists of heat-coagulable latex. Without any addition of salts or other pore formers, the latex is foamed using a gaseous medium, preferably with air. The fiber-latex ratio is expediently in the range from 80:20 to 10:90% by weight.

The fiber material from the mixture described above is mixed according to a preferred method in aqueous suspension with the latex mixture and then foamed with air. The resulting foam mass is applied to a textile carrier and fixed by coagulation by the action of heat. The fiber-latex structure is then dried together with the carrier material in order to obtain a coherent structure.

The fabric according to the invention differs decisively both from the raw materials and with regard to the production process from the known viscose sponge cloths. While the viscose sponge cloth is spread over the cellulose xanthate with salts, e.g. Sodium sulfate, as a pore former, the material according to the invention can be produced without pore former. The mass, which is only foamed with air, is fixed in its shape. The fixed latex foam is vulcanized or condensed during or after drying.

The fiber mixture is optionally processed together with a wetting agent in a 5 to 30% by weight suspension, based on their total weight, to form the fiber foam. It is usually advisable to use a 10% by weight suspension. The latex mixture can either be added to this foam without being foamed or it can also be already foamed. It is advisable to use heat-sensitive latex mixtures that are coagulated by heat after application to the reinforcing fabric, knitted fabric, foam or nonwoven fabric. The fabric fixed in this way is dried and then vulcanized or condensed.

The "sponge cloth" according to the invention has a soft feel even in the dry state and, in contrast to viscose sponge cloths, can therefore be marketed dry packed without the addition of water and plasticizers. It is therefore hygienically harmless, while the moist packaged viscose sponge cloths can always be infected by bacteria or fungi.

The sponge cloth is essentially open-pored. The cell walls are severely broken. There are larger voids than with the viscose sponge cloth. In terms of its structure, the product is very similar to the natural sponge with its dense tangle of fibrils and extensive cavities

While the base material of the viscose sponge cloth is purely hydrophilic, the material according to the invention can have hydrophilic properties both with regard to the fibers and hydrophobic with respect to the latex. In the dry state it is soft and elastic, while the elasticity is essentially retained even when wet. When wetting takes place very quickly, the material absorbs several times its own weight in water.

According to the invention, the fiber-latex ratio is between 80:20 and 10:90% by weight. Cellulose short cuts with a fiber length of about 2 to 16 mm are proposed as hydrophilic, absorbent fibers, furthermore cellulose, cellulose dust, cotton dust, linters, wood pulp, polyvinyl alcohol fibers and mixtures of the above-mentioned components. As a rule, fiber proportions of up to 100% by weight of cellulose dust, up to 100% by weight of cotton dust, up to 50% by weight of cellulose and 10 to 50% by weight of short cotton cuts (1.7 to 22 dtex) are recommended. For short cuts, fibers with a length of 5 to 8 mm are preferred. Polyamide, polyester, polypropylene or polyacrylonitrile fibers are suitable as hydrophobic synthetic short cut fibers. The synthetic fibers are advantageously added in an amount of 2 to 30% by weight. The proportions by weight relate in each case to the total weight of the fiber mixture. For better processability, 0.5 to 2% by weight of conventional wetting agents are expediently added.

The latex mixture consists of conventional acrylates, methacrylates, polyurethanes, butadiene-acrylonitrile copolymers or butadiene-styrene copolymers, it being recommended to use heat-coagulable mixtures, the composition of which can be determined by simple preliminary tests

The manufacturing process for the proposed fabric is defined in the claims. As a rule, a 10% by weight fiber suspension is foamed to a liter weight of 200 to 500 g. The non-foamed or foamed latex mixture is added to this foam, the mixture of both components being brought to a liter weight of appropriately 200 to 500 g. But you can also have a non-foam fiber suspension with unfoamed or versc _h mix äumter latex mixture and then bring both components to a liter weight of 200 to 500 g.

The coagulation point of the heat-sensitive mixture is expediently between 30 and 60 ° C.

The foamed mixture is applied to a reinforcing carrier made of woven, knitted, foam or nonwoven and coagulated under the action of heat. A pattern can be embossed for optical reasons. After drying at about 130 ° C, vulcanization is then carried out, e.g. at 150 ° C. The cloth is then washed out. Most of the water is removed by squeezing or suction and the pre-dewatered structure is dried again by the action of heat.

The backing material coated on one or both sides remains as a reinforcement in the finished sponge cloth. In the event that a reinforcing insert is not desired, it is advisable to apply the foamed mass of fibers and latex to an all-round metal or plastic belt. After the solidification, the pubic mass can then be separated from the carrier. A sponge-like material without internal reinforcement is thus obtained.

Due to the proposed fiber mixture, the hydrophilic properties of the cloth can be varied according to the intended use. A further variation is also possible through a suitable choice of latex. In addition to natural latex, rubber latex made from butadiene acrylonitrile, butadiene styrene and their diverse copolymers, if appropriate together with other copolymers, is also suitable as latex. In addition to polyacrylates and polymethacrylates and their numerous copolymers, aqueous dispersions of polyurethanes are also suitable.

The following examples serve to explain the invention.

example 1

106 g of butadiene acrylonitrile latex with a solids content of 47% by weight is adjusted to heat sensitivity using conventional additives (sulfur, zinc oxide, vulcanization accelerators, organopolysiloxanes, etc.) (coagulation point 55 to 60 ° C.) and foamed to twice the volume. 350 g of a 10% by weight cellulose dust / cotton dust suspension (cellulose / cotton 1: 1) are introduced into the foam and the entire mass is foamed to a final volume of 1100 ml. The foam mass is applied to a textile carrier material (cellulose fleece, 50 g / m ² ), coagulated and dried at 130 ° C. It is then vulcanized at 150 ° C. The material thus produced is soft and has closely spaced pores of approximately 0.5 to 1 mm in diameter. The material absorbs four times its own weight in water.

Example 2

106 g of butadiene acrylonitrile latex with a solids content of 47% by weight is adjusted to the heat with conventional additives (as in Example 1) (coagulation point 55 to 60 ° C.) and foamed to twice the volume. 200 g of a 10% by weight pulp suspension containing a wetting agent are stirred in, producing 650 ml of foam. The mass is applied to a 50 g / m ² cellulose fleece, coagulated, dried at 130 ° C and vulcanized at 150 ° C. After washing, it is dried again. The result is a heavy material with very good strength. The rather layer-like structure has pores of very different sizes of approximately 0.5 to 4 mm in diameter. With this material, a sink can be weighted to dryness.

Example 3

The latex foam produced as in Example 2 is mixed with 400 g of foam, which is produced by foaming a 10% by weight suspension of 75% by weight cellulose and 25% by weight fiber dust from 50% by weight cellulose and 50% by weight cotton dust. Water and wetting agent was obtained. 1700 ml of foam are produced. The foam mass is approx _. 2.5 mn thick on an approximately 50 g / m ² heavy nonwoven fabric made of cellulose fibers, coagulated at 55 ° C and pre-dried at 130 ° C. The back of the nonwoven fabric is treated in the same way and the product is then vulcanized at 150 ° C. and then washed out and dried again. The pores of the material are separated by very thin layers of material, so that there is a loose structure and a soft feel.

Example 4

142 g of a latex foam made of polybutadiene acrylonitrile with a solids content of 42% by weight and a liter weight of 475 g are mixed with 350 g of a foam which is made by foaming a 10% by weight cellulose dust-cotton dust suspension (50% cellulose dust and 50% by weight). % Cotton dust) was obtained. The foam mass is applied to a carrier made of 2 mm thick foam, coagulated at 50 ° C. and provided with a pattern by stamping. After predrying, the back is also coated, coagulated at 50 ° C and also provided with a sample. After drying and vulcanization at 140 bwz. The material is washed out at 160 ° C and mechanically freed of water by squeezing. The very soft, spring-elastic cloth has a very low basis weight (289 g / m ² ).

Example 5

180 g latex mixture of polybutadiene acrylonitrile with a solids content of 35.5% by weight, which contain 10 g chalk, are made up to 350 ml foamed. 17.5 g of cotton wool dust, 8.8 g of bleached cellulose and 15.1 g of cellulose short cut fibers 5.6 / 6 (58%) are mixed with 330 g of water and 25 g of oleoylmethyl tauride as a wetting agent (24%) to 1200 ml of foam volume brought. Both foams are combined and foamed to a total of 2100 ml. The mass is applied 2.5 mm thick to a cellulose tissue (mesh size 1 x 3 mm) and coagulated at 47 ° C. After the pattern is pre-dried and the back of the cellulose fabric coated, coagulated and embossed in the same way. After drying at 130 ° C is vulcanized at 150 °, then washed out and dried again.

The sponge cloth obtained according to this example has particularly favorable combinations of properties. The material is very soft and pleasant to the touch, has good strength and a low basis weight with a very open pore structure. It can be cooked without losing its structure and strength.

Example 6

180 g of latex mixture as in Example 5 are added without foaming to 399 g of fiber suspension which has been foamed to 1000 ml. The fiber blend contains 25% cotton wool dust, 25% cellulose dust, 25% cellulose, 10% cellulose short cut fibers 5,6 / 8 and 15% polyester short cut fibers 3,3 / 8. The mixture of latex compound and fiber foam is foamed to 2,150 ml. The mass is applied as in Example 5, dried and vulcanized. The material has a slightly harder grip than the material obtained in Example 5 and is characterized by a high tensile strength at very high. low basis weight.

Claims (12)

1. Porous, absorbent fabric made of a latex-bonded fiber material, which optionally contains a reinforcement made of woven, knitted, foam, nonwoven or abrasive nonwoven, characterized in that the fiber material is a mixture of hydrophilic staple fibers and / or fiber dust, pulp of different lengths, Wood pulp, linters or the like and optionally hydrophobic staple fibers as an admixture, the fiber mixture being embedded in an open-pore foam made of heat-coagulable latex, which contains no additives such as salts, pore formers or the like, the fiber-latex ratio in the range from 80: 20 to 10: 90% by weight. 2. Flat structure according to claim 1, characterized in that the fiber material up to 100% by weight cellulose dust, up to 100% by weight cotton dust or linters, up to 50% by weight cellulose, 10 to 50% by weight cellulose short cuts and Contains 2 to 30 wt.% Synthetic short cuts. 3. Flat structure according to one of claims 1 or 2, characterized in that the latex mixture contains latexes based on acrylates, methacrylates, polyurethanes, butadiene acrylonitriles, butadiene styrene or copolymers thereof. 4. A process for the production of an absorbent sheet material interspersed with pores according to one of claims 1 to 3, characterized in that the fiber mixture in aqueous suspension and the likewise aqueous latex suspension are foamed together or separately with a suitable gas, for example air, and so the foam obtained is homogeneously mixed either on a non-stick carrier or on one or both sides on a reinforcing insert which intimately connects with the foam, and that the fiber-containing latex foam then it is coagulated by the action of heat, an open pore structure being formed, which is stabilized by subsequent drying and vulcanization or condensation and that the solidified and stabilized fabric may be washed out again and dried again. 5. The method according to any one of claims 1 to 4, characterized in that the foam composition is applied thickly on one side to an abrasive fleece made of various synthetic fibers, binders and abrasives and then dried and vulcanized. 6. The method according to claim 4, characterized in that the aqueous fiber suspension is foamed with air to a liter weight of 200 to 500 g and the latex suspension is added without foam. 7. The method according to claim 4, characterized in that the aqueous latex suspension is foamed with air to a liter weight of 200 to 600 g and the fiber suspension is added unfoamed. 8. The method according to any one of claims 4 to 7, characterized in that cotton wool dust, linters, cellulose dust, cellulose short cuts, cellulose, wood pulp and / or polyvinyl alcohol fibers and as hydrophobic synthetic shortcut fibers such as polyamide, polyester, polypropylene as absorbent fibers and / or polyacrylonitrile are used, the hydrophilic fiber dusts or fibers and the hydrophobic synthetic short-cut fibers being used in a concentration of 5 to 30% by weight each in aqueous suspension. 9. The method according to claim 8, characterized in that the fiber concentration is 10% by weight. 10. The method according to any one of claims 4 to 9, characterized in that the fibers and the latex are used in a ratio between 80: 20 and 10 90. 11. The method according to claim 10, characterized in that the ratio of fibers to latex is between 70:30 and 40:60. 12. The method according to any one of claims 4 to 11, characterized in that 5 to 40% by weight of the latex are replaced by fillers such as chalk or kaolin.