DE1258255B - Process for the production of hydrophobic, water-resistant or wash-resistant nonwovens, preferably based on natural and / or regenerated cellulose - Google Patents

Description

Process for the production of hydrophobic, water- or wash-resistant Nonwovens, preferably based on natural and / or regenerated cellulose The process refers to nonwovens made by impregnating loose Fiber structures, preferably nonwovens made of cellulose fibers, such as rayon or Cotton, with aqueous solutions of binders, which in addition to hydroxyl groups Contain carboxyl groups and which are in the form of their water-soluble salts, z. B. carboxymethyl celluloses or alginates, and solidification of the fiber structure by subsequent drying or flocculation of the binder.

The production of nonwovens is already becoming technical on a large scale carried out. However, the fibers are mostly bonded using aqueous dispersions of rubber or synthetic resins. Rubber or synthetic resin bonded Nonwovens are generally not resistant to cleaning and are often also thermoplastic. In addition, you cannot do this, for example, when using cellulose fibers dye homogeneously, because fibers and binders are very different in terms of dyeing behavior. It is also known that water-soluble fabrics are used for gluing fiber webs Binders, e.g. B. starch, carboxymethy! Cellulose or alginates, can use. The nonwovens obtained with these binders, however, are not water or washable and disintegrate again when placed in water or washing liquors into the fibers.

There are several methods of improving water resistance known.

According to British Patent 734 725 , water-soluble ammonium salts of the carboxymethyl or. the carboxyethyl cellulose incorporated into the nonwoven fabric. After drying, the heating is so high that the free acid is formed with elimination of ammonia, which then changes to the water-insoluble state when further exposure to heat. The same can be achieved if, instead of the ammonium salt, a water-soluble alkali salt which still contains at least 50% free carboxyl groups is used. After drying and subsequent heat treatment, this salt also becomes insoluble. In the case of paper, for example, the process leads to an improvement in the wet strength. However, the washing resistance is insufficient; In addition, this does not result in any hydrophobization, d. H. no water-repellent properties achieved.

It is also known that the water-soluble salts of carboxymethyl or the carboxyethyl cellulose or alginic acid by reaction with acids or with metal salts, e.g. B. with aluminum salts, converted into water-insoluble compounds can. However, these compounds are not washable because they are alkaline Laundry can be converted back into water-soluble alkali salts.

One has now set oneself the task of producing nonwovens, preferably such Made of cellulose fibers, with water-soluble binders, in addition to hydroxyl groups still contain carboxyl groups to solidify and the nonwovens obtained in this way through a suitable post-treatment in the water- or wash-resistant state and to give them water-repellent properties at the same time.

This was achieved according to the invention in the following way: In a known manner, fiber fleeces are produced on the card or on the Rando-Webber or by another method; these are then - also in a known manner - with the aqueous solution of the binder, for. B. od by passing the loose fleece between followers made of metal gauze. Like. Through the bath, impregnated. The fleece can also be pre-consolidated on the surface by spraying with the solution of the binder and then by dipping, e.g. B. in a padder, or by sucking the solution through the fleece and then removing the excess impregnating agent, e.g. B. be impregnated by squeezing. After drying the impregnated fleece at an elevated temperature or without intermediate drying while it is still moist, it is subjected to an aftertreatment with an aqueous solution containing the following components: 1. A water-soluble synthetic resin precondensate from the group of so-called reactive resins, these are synthetic resins that are capable are to react in the presence of acidic catalysts and at elevated temperature with the hydroxyl groups of the binder to form bridges and thereby make it resistant to alkaline washing liquors, 2. a water-soluble metal salt that reacts with the carboxyl groups of the binder, converting it into a water-insoluble compound and at the same time gives the nonwoven water-repellent properties.

Only by implementing these two components can you get at Use of these water-soluble binders, water-resistant or wash-resistant substances with hydrophobic properties.

Alkali salts of carboxymethylene huloses and of alginic acids are preferably used as binders. In order to achieve good thorough impregnation and thus good bonding of the fiber material, it is advisable to use types which are relatively low-viscosity in aqueous solution. In particular, such types whose aqueous 1 0 /, by weight solutions have a viscosity of up to 1:00 are cP.

Tetramethylolazethylene diurea, for example, can be found as reactive resins or Dimethyloldihydroxyäthylenurea or Dimethyloläthylenurea use.

Suitable metal salts are preferably those which are used during hydrolysis form strong acids, such as B. aluminum formate, and therefore at the same time as Catalyst in the reaction of the reactive resins with the hydroxyl groups of the binder works.

The binders not only lead to an excellent bond of the fiber material, but result in the case of the cellulose fibers preferably used another advantage that fiber material and binding agent can be dyed homogeneously, which is not the case when gluing with rubber or synthetic resin binders.

The hydrophobic properties of the nonwoven material can still be improved are, if the aqueous solution of the binder water-soluble soaps, for. B. sodium or ammonium oleate added, which is then in the NachbehandUung, z. B. with aluminum formate, in water-insoluble, highly hydrophobic aluminum salts realize.

Both the binder solution and the aftertreatment bath can be pigments, dyes, fillers, plasticizers, antifouling, flame retardant Substances etc. are added.

When using cellulose fibers, the reactive resin will also react with the hydroxyl groups of the cellulose, which improves the swelling resistance and elasticity of the nonwoven fabric. In addition, bridging can also occur between the cellulose and the binder, which naturally results in particularly good bonding. For the nonwovens to be produced according to the invention, random fiber nonwovens made of cellulose fibers, e.g. B. made of rayon or cotton. The ratio of fiber weight to binder depends on the desired properties of the nonwoven. The impregnation of the fiber webs with the solution of the binder can all already in the nonwoven fabric manufacturing processes customary - take place - in a foam by transfer of the solution.

The reactive resin can also be added to the binder solution. In this case, however, it is necessary that the liquor is an acid-releasing catalyst, for. B. ammonium nitrate is added. In addition, the impregnated material must be dried after squeezing and subjected to a heat treatment between 120 and 160 ° C. so that the reaction of the reactive resin with the hydroxyl groups of the binder takes place. The amount of reactive resin depends on the amount of binder and the desired degree of crosslinking. The more reactive resin is present, the more hydroxyl graves are converted. It is advisable to add more metal salts to the aftertreatment bath than is necessary for the reaction with the carboxyl grapes, because this prevents the binder - if it has not yet reacted with the reactive resin - from going back into solution and because the excess leads to an improvement the hydrophobization achieved.

Claims (4)

Claims: 1. A process for the production of hydrophobic, water- or wash-resistant nonwovens by gluing together loose fiber structures, preferably based on natural and / or regenerated cellulose with a water-soluble binder which, in addition to hydroxyl groups, also contains carboxyl groups, characterized in that the fiber structures are after impregnation with the aqueous solution of the binder and optionally an intermediate drying, an aftertreatment with an aqueous liquor which a) subjects a reactive resin based on N-methylol compounds, which in the presence of an acid catalyst and when heated to a temperature above 100'C reacts with the hydroxyl groups of the binder, b) a metal salt, such as aluminum formate, which makes the binder water-insoluble by reacting with the carboxyl groups and at the same time gives the nonwoven water-repellent properties. 2. The method according to claim 1, characterized in that the reactive resin and an acid-releasing catalyst required for reaction with the hydroxyl groups, for. B. Ammonium nitrate, is already added to the solution of the binder and that the reaction of the carboxyl groups with the metal salt takes place by impregnating the already solidified fiber structure with an aqueous solution of the metal salt and subsequent drying. 3. The method according spoke 1 and 2, characterized in that water-soluble soaps are added to the aqueous solution of the binder, which are converted into water-soluble, highly hydrophobizing salts by the subsequent treatment. 4. The method according spoke 1 to 3, characterized in that the solution of the binder and / or the solution of the aftertreatment bath pigments, dyes, FüRstoffe, plasticizers, antifouling, flame retardant substances, etc. are added. Considered publications: German Patent Nos. 857 040, 866 596, 895 436, 965 864, 968 049; German Auslegeschrift No. 1 056 916; German interpretation document C 8371 IVa / 55i (published on December 27, 1956).