EP2496343A1

EP2496343A1 - Textiles comprising improved superabsorbers

Info

Publication number: EP2496343A1
Application number: EP10771474A
Authority: EP
Inventors: Peter Rudolf; Andreas Brockmeyer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-11-06
Filing date: 2010-11-02
Publication date: 2012-09-12
Also published as: CN102596393A; US20120209231A1; WO2011054784A1; JP2013510245A

Abstract

The invention relates to textiles comprising improved superabsorbers comprising hydrophilic fibers introduced after applying superabsorbers. A relatively open-pored textile can have superabsorbers applied in this manner, but the distribution of liquid fed to the textile is significantly improved by means of the additionally introduced hydrophilic fibers.

Description

The present invention relates to improved superabsorbent-containing textiles, processes for their preparation and their use for water absorption, including use for moisture regulation. The invention relates in particular to textiles containing superabsorbents, in which the distribution of liquid is improved.

Superabsorbent containing textiles are known. In such textiles, superabsorbent is a constituent of the textile; it is produced, for example, by polymerization of a corresponding monomer solution or monomer suspension applied to the textile or introduced into the textile fabric as a finished powdery or fibrous superabsorber during production of the textile.

Superabsorbents themselves are also known. Also, for such materials, terms such as "high swellable polymer" "hydrogel" (often used for the dry form), "hydrogel-forming polymer", "water-absorbent polymer", "absorbent gelling material", "swellable resin", "water-absorbent resin These are crosslinked hydrophilic polymers, in particular polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose partially cross-linked polyalkylene oxide or natural products swellable in aqueous liquids, such as guar derivatives, whereby water-absorbing polymers based on partially neutralized acrylic acid are the most widespread.The essential properties of superabsorbents are their ability to multiply their own weight of aqueous liquids absorb the fluid and even under some pressure not to release the liquid again. The dry superabsorbent transforms into a gel when it absorbs liquid, with the usual water absorption corresponding to a hydrogel. Crosslinking is essential for synthetic superabsorbents and an important difference to conventional pure thickeners, as it leads to the insolubility of the polymers in water. Soluble substances would not be useful as superabsorbents. By far the most important application of superabsorbents is the absorption of body fluids. Superabsorbents are used, for example, in infant diapers, adult incontinence products or feminine hygiene products. Other fields of application are, for example, those used as water-retaining agents in agricultural horticulture, as water storage for protection against fire, for liquid absorption in food packaging or, more generally, for the absorption of moisture.

The state of the art for superabsorbers, for example, in the monograph "Modern Superabsorbent Polymer Technology", FL Buchholz and AT. Graham, Wiley-VCH, 1998, pages 69 to 17, summarized.

WO 01/56625, EP-A 1 178 149 and US 5,962,068 describe processes for the production of water-absorbing textiles in which water-absorbing polymers are grafted onto a support material. WO 2006/106096 A1 describes moisture-regulating textiles which contain at least one planar support material, at least one water-soluble hygroscopic substance and at least one superabsorber grafted onto the support material in the presence of the water-soluble hygroscopic substance. JP-A 05-105705 relates to non-flowing drying agents, consisting of a carrier material and hygroscopic salts, wherein the hygroscopic salts are fixed by means of superabsorbers on the carrier material.

WO 2007/023085 A1 teaches moisture-regulating textiles which do not form any undesirable unevenness upon contact with relatively high quantities of liquid (for example, spilling liquid on the textile). The moisture-regulating textiles of WO 2007/023086 A1 contain a plasticizer in order to avoid undesired stiffness.

WO 00/6431 1 discloses textiles in which superabsorbents have been polymerized onto a support material. The textiles are used for moisture regulation in seat cushions. WO 2004/067826 A1 teaches multilayer textile fabrics, in particular those of single-sided mesh-coated nonwovens, which may contain functional agents, for example superabsorbents, and are suitable as upholstery fabrics. DE 40 01 207 A1, DE 40 34 920 A1, DE 41 27 337 A1, DE 42 06 895 A1,

DE 197 26 810 C1 and DE 198 09 156 A1 relate to the use of moisture-regulating textiles in seat furniture, in particular in motor vehicle seats.

A constant task in the application of superabsorbers is to distribute the liquid to be absorbed well over the available amount of superabsorber. This is the case in particular for hygiene articles in which the liquid to be absorbed is locally concentrated and introduced in a comparatively large amount in a short time, but may also be relevant in other applications, for example if liquid is spilled onto a climate-regulating layer of a pad. If only superabsorbent swells locally, a gel layer forms, the further liquid entry blocks (the so-called "gel-blocking"), the distances between the gel particles are too high, the liquid runs through. In hygiene articles, more precisely in their "absorbent core" (often called "diaper core" or only "core") are therefore usually integrated liquid distribution layers, which ensure uniform distribution in a liquid storage layer. This storage layer contains the entire amount or at least the predominant amount of superabsorber which permanently absorbs the discontinued liquid. It is typically in the storage layer with Cellu- loose fibers ("fluff") mixed to provide for liquid transport within the storage layer.

No. 5,728,085 describes a hygiene article in which pulp roll goods are used directly and without the usual further loosening as the absorption layer. US 2002/01223728 A1 teaches a liquid distribution layer for sanitary articles in which crosslinked and uncrosslinked cellulose fibers are combined.

According to the teaching of WO 2005/094 749 A2, the problem of liquid distribution is solved by using a superabsorber with a relatively low content of fluff, which itself has high fluid-transfer capability and is combined with hydrophilic dendritic polymer and water-insoluble phosphate.

US 6,140,550 discloses a comparatively open, fiber-formed structure such as an open-celled polyurethane foam containing superabsorbents. The open structure allows unhindered entry of liquid. This structure may also be laminated with other fabrics, such as nonwovens of hydrophilic fibers. No. 5,451,452 combines a foam-type superabsorbent with a textile layer for liquid distribution.

According to the teaching of WO 95/35 081 A1, strips of denser material are incorporated in a hygiene article in the absorption body of a hygiene article, which is essentially composed of nonwoven or wadding (often with the English term "fluff") and superabsorbers, in order to better penetrate the incoming liquid WO 01/21 122 A1 teaches absorption bodies in which superabsorbent is arranged in a concentrated manner in longitudinal strips by a fluff matrix The fluting formed in particular after a first swelling of the superabsorber promotes the distribution of liquid WO 97/40 223 A1 describes a process for producing a nonwoven having different pore sizes. Such a structure has better liquid distribution.

WO 03/053 483 A1 teaches a cover layer for a hygiene article which, although made of hydrophobic material, has been permanently hydrophilized on the surface. This causes improved liquid distribution in the absorption body under the cover layer.

US 2004/0 254 551 A1 discloses an absorbent core for sanitary articles which also manages without liquid distribution layers and in which fluff, superabsorbents, binding elements (eg two-component fibers) and thin hollow fibers are combined. WO 94/24975 A1 teaches the use of thin hydrophilic fibers in addition to fluff in the core to improve the liquid distribution.

There is an additional problem with textiles containing superabsorbents. If such materials are produced by spraying a monomer mixture onto the textile and subsequent polymerization, firmly adhering superabsorbent particles are formed, which is generally desirable. For this purpose, it is desirable that the textile is relatively open-pored, otherwise the sprayed monomer mixture remains only on the surface of the textile and after polymerization a comparatively hard superabsorber surface layer with little gaps between the Superabso- rer particles arises, the pronounced gel-blocking The fabric also substantially loses flexibility, which is undesirable in applications such as a storage layer in sanitary articles or as a moisture-regulating layer in upholstery, however, when using a very open-pored fabric, applied liquid is often only satisfactorily absorbed, since the open-pore textile itself can only badly buffer and distribute liquids, a considerable proportion of applied liquid then merely runs through the textile.

It is therefore the object to find an improved superabsorbent-containing textile. In particular, it should be better able than known textiles to be able to distribute applied liquid in itself, so that this liquid can be absorbed as completely as possible by the superabsorber contained. In addition, the textile should lose as little as possible of their flexibility and superabsorbent should be able to be applied to them in an advantageous manner.

Accordingly, there has been found an improved superabsorbent-containing fabric containing hydrophilic fibers incorporated after the superabsorber application.

Furthermore, a process for their preparation and applications has been found.

It has been found that with the textile according to the invention and the process for its production on the one hand it is achieved that a relatively open-pored textile can be provided with superabsorber, but the liquid distribution is significantly improved by the additionally introduced hydrophilic fibers.

The textile can in principle be any type of textile to which superabsorbents can be applied. Textiles are flexible fiber composites, in particular flat flexible fiber composites. In addition to fibers, fiber composites of this type also have interstices (often also called "pores") between the fibers In the context of this invention, textiles are, in particular, semi-finished and finished textile products, such as tapes, nonwoven fabrics (ie fiber composites held together by the fibers' own adhesion). or nonwovens (these are additionally consolidated nonwoven fabrics), felts (felted wicks, needle felts), woven fabrics, bobbinets, braids, knitted fabrics and knits, netting, lace, embroidery, stitchbonded fabrics, tufts, mixed forms thereof, and finished textile goods made therefrom. The basic definitions of textiles and other relevant terms in this field are laid down in DIN 60000 (January 1969). In the context of this invention, open-celled sheet-like foams such as textiles can also be used and are covered by the term textiles. Mainly for economic reasons, nonwovens are predominantly used for the fields of application in question, depending on the intended use, with or without additional strengthening beyond the fibers' own adhesion. Nonwovens are preferred textiles for the present invention, essentially for economic reasons. If the term "fleece" is used in the description of the present invention, this term is therefore synonymous with textiles. "Materials such as the superabsorber-containing textiles in question are often also referred to as" superabsorbent nonwovens "or" superabsorbent coated nonwovens ". called.

The textile according to the invention comprises at least one textile as a flat carrier material and at least one superabsorbent. It may contain further constituents, in particular those already known as constituents of superabsorbent nonwovens. Examples of such further ingredients are hygroscopic substances or plasticizers.

Suitable nonwovens according to the invention include in particular those made of synthetic fibers. The plastic fibers can be made from all polymers from which fibers are formed and from which fibers a nonwoven fabric can be made. Examples of suitable polymers are polyolefins such as polyethylene, polypropylene and the like, polyesters such as polyethyleneterephthalate and the like, polyamides such as polyamide 6, polyamide 6,6, poly (iminocarboxylpentamethylene) and the like, acrylic fibers and modified cellulosic material such as cellulose acetate and rayon, and mixtures and copolymers thereof.

The production of the plastic fibers can be carried out by meltblowing, by the spunbonding process, by extrusion and drawing or by other wet, dry and melt spinning processes known to the person skilled in the art. The plastic fibers from which the web is formed may have a finite length or be substantially endless. For example, if the plastic fibers are formed by meltblowing, they can be essentially endless (few visible ends). When the fibers are made by extrusion and drawing into a tow or sliver, they may be so used or staple fibers having a length of, for example, about 25 millimeters to about 75 millimeters or short cut fibers having a length of about 1 millimeter to about 25 millimeters cut. The plastic Fibers may suitably have a maximum cross section of about 0.5 microns to about 50 microns as determined microscopically with the light microscope and the calibrated step micrometer or by scanning electron micrographs.

The nonwoven fabric can be produced directly by wet or dry forming, by spunbond or meltblown processes, for example by carding or web formation in the air flow ("airlaids") of staple or short cut fibers The nonwoven web may then be thermally or mechanically bonded to one of the methods known in the art for bonding nonwovens include thermobonding, spot bonding, powder bonding, ultrasonic bonding, chemical bonding, mechanical needling, water jet bonding, stitching and the same.

The fibers may be homogeneous fibers or else multicomponent fibers, in particular bicomponent fibers such as core-sheath or side-by-side fibers.

The nonwoven may consist of a single type of plastic fiber or contain plastic fibers of different fiber lengths or diameters formed from different polymers. For example, the nonwoven may comprise a blend of (1) polyethylene sheath bicomponent polypropylene core polypropylene fibers having a maximum cross sectional diameter of about 20 microns and a length of about 38 millimeters, and (2) polyester fibers (polyethylene terephthalate) having a largest cross sectional diameter of about 25 microns and a length of about 38 millimeters. The fibers 1 and 2 may be present in a weight ratio of 1:99 to 99: 1. The fibers may be uniformly mixed or enriched on opposing planar surfaces of the web. A suitable nonwoven generally consists of at least 10 wt%, preferably at least 20 wt%, more preferably at least 25 wt%, and most preferably at least 50 wt% plastic fiber. The weight fraction of plastic fiber may be 100% by weight. In addition to the plastic fibers, however, the nonwoven may also contain 0 to 90% by weight of a non-plastic fiber such as pulp fluff, cotton linters, cotton and the like.

In general, the polymers from which the synthetic fibers of the web are formed have inherently hydrophobic properties. In this case, a material is referred to as "hydrophobic" when the contact angle between water and the material is greater than 90 degrees. A material is referred to as "hydrophilic" if the contact angle between water and the material is less than 90 degrees. Within the framework of In the invention, a polymeric material is considered to be "inherently" hydrophobic or hydrophilic if it is hydrophobic or hydrophilic without application of additives or adjuvants (such as surfactants or spin aids). The nonwoven generally has a basis weight of at least 20 g / m ² , preferably at least 30 g / m ² and more preferably at least 50 g / m ² and generally at most 800 g / m ² , preferably at most 400 g / m ² and most preferably not more than 200 g / m ² . The nonwoven fabric typically has a density of at least 0.005 g / cm ^3, preferably at least 0.008 g / cm ³ and more preferably at least 0.01 g / cm ^3, and generally of at most 0.12 g / cm ^3, preferably of at most

0.1 g / cm ³ and in a particularly preferred form of at most 0.08 g / cm ³ . The nonwoven may additionally contain hydrophilic fibers. These may be inherently hydrophilic materials such as cellulosic fibers, such as pulp fluff, cotton linters and the like, cellulosic regenerate fibers such as rayon or certain nylon copolymers such as poly (pentamethylenecarbonamide) (polyamide-6) / polyethylene oxide. Alternatively, hydrophilic fibers are also obtainable by treating hydrophobic fibers with a hydrophilizing agent. For example, the hydrophilic fibers can also be made from a polyolefin, which is subsequently coated with a surfactant, such as a surfactant, so that the fiber becomes hydrophilic. Other methods for hydrophilizing fibers from hydrophobic substances are also known and suitable in the context of the invention.

Methods of making inherently hydrophilic fibers such as pulp fluff are known, as well as methods of making regenerated cellulose fibers such as rayon or hydrophilic fiber hydrophilization methods. When the hydrophilic fibers are made by hydrophilizing hydrophobic fibers, the fibers desirably have a fiber length and a diameter in the above ranges. When the hydrophilic fibers are inherently hydrophilic, such as pulp fluff, rayon, cotton, cotton linters and the like, the fibers typically have a length of from about 1.0 millimeter to about 50 millimeters and a diameter of about 0, 5 microns to about 100 microns.

The web may contain a single type of hydrophilic fiber, but also hydrophilic fibers of different composition, length and diameter.

In a particular embodiment, the web consists of airlaid cellulosic fibers such as pulp fluff. Pulp fluff fibers are preferred over synthetic fibers for their ease of accessibility and cost advantage used. Such a nonwoven generally has a basis weight of at least 20 g / m ² , preferably at least 25 g / m ² and more preferably at least 50 g / m ² and generally of at most 200 g / m ² , preferably at most 150 g / m ² and most preferably at most 125 g / m ² . Such a web generally has a density of at least 0.04 g / cm ³ , preferably at least 0.06 g / cm ^3, and more preferably at least 0.08 g / cm ^3, and generally at most 0.20 g / cm ³ , preferably of at most 0.16 g / cm ³ and in a particularly preferred form of at most 0.14 g / cm ³ . Another useful carrier material in the superabsorbent web is one of the elastomers known and often used for composites in seating, mattress and automotive seat covers. Nonwovens of the "multiknif", "maliwatt", "malivlies" or "kunit" type, for example, are nonwovens which are produced, for example, by stitch-bonding processes and are characterized by a partial reorientation of the mostly longitudinal fibers in the transverse direction, so that a thickening of the web takes place and a certain compressive elasticity or cushioning effect is generated.

The superabsorbent nonwoven according to the invention contains superabsorbers on or in the nonwoven used as carrier material. This is produced, for example, by polymerization of a corresponding monomer solution or suspension applied to the nonwoven on the nonwoven or introduced as a finished powdered or fibrous superabsorber in the production of the nonwoven in this by the production of the nonwoven fabric in the presence of superabsorbent particles. In this case, any known superabsorbent can be used. The polymerization of a monomer solution applied to the nonwoven typically leads to superabsorber particles adhering particularly firmly to the fibers and uniformly distributed in the nonwoven, and is also technically comparatively simple and therefore the preferred process for the production of superabsorbent nonwovens.

The monomer solution or suspension applied (for example sprayed or impregnated) onto the nonwoven fabric in this process for subsequent polymerization typically contains: a) at least one ethylenically unsaturated acid group-bearing monomer which may be at least partially neutralized,

b) at least one crosslinker,

c) at least one initiator,

d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomers mentioned under a);

e) optionally one or more water-soluble polymers f) at least one solvent; and

g) optionally further additives and / or auxiliaries.

The monomers a) are preferably water-soluble, i. the solubility in water at 23 ° C. is typically at least 1 g / 100 g of water, preferably at least 5 g / 100 g of water, more preferably at least 25 g / 100 g of water, most preferably at least 35 g / 100 g of water.

Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and itaconic acid. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.

Further suitable monomers a) are, for example, ethylenically unsaturated sulfonic acids, such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

Impurities can have a significant influence on the polymerization. Therefore, the raw materials used should have the highest possible purity. It is therefore often advantageous to purify the monomers a) specifically. Suitable purification processes are described, for example, in WO 2002/055469 A1, WO 2003/078378 A1 and WO 2004/035514 A1. A suitable monomer a) is, for example, an acrylic acid purified according to WO 2004/035514 A1 with 99.8460% by weight of acrylic acid, 0.0950% by weight of acetic acid, 0.0332% by weight of water, 0.0203% by weight. % Propionic acid, 0.0001% by weight furfurale, 0.0001% by weight maleic anhydride,

0.0003% by weight of diacrylic acid and 0.0050% by weight of hydroquinone monomethyl ether.

The proportion of acrylic acid and / or salts thereof in the total amount of monomers a) is preferably at least 50 mol%, particularly preferably at least 90 mol%, very particularly preferably at least 95 mol%. Usually, a part of the monomer a) is neutralized. Although it is theoretically possible to polymerize the monomer in the unneutralized state and then to neutralize the resulting polymer gel, with superabsorbent nonwovens a sufficiently homogeneous neutralization at this stage is usually complicated and therefore uneconomical. Preferably, therefore, the monomer is partially neutralized. This is usually done by mixing the neutralizing agent as an aqueous solution or preferably as a solid in the monomer or the monomer solution. The degree of neutralization of the monomer is generally at least 25 mol%, preferably at least 50 mol% and more preferably at least 60 mol% and generally at most 95 mol%, preferably at most 80 mol%, and most preferably not more than 75 mol%, the usual neutralizing agents may be used, preferably alkali metal hydroxides, alkali metal tallow oxides, alkali metal carbonates or alkali metal bicarbonates and mixtures thereof. Instead of alkali metal salts and ammonium salts can be used. Sodium and potassium are particularly preferred as alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof.

The monomer solution contains as stabilizer against undesired early polymerization preferably up to 250 ppm by weight, preferably at most 130 ppm by weight, more preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, particularly preferably at least 30 Ppm by weight, in particular by 50 ppm by weight of hydroquinone half ether, in each case based on the unneutralized monomer a). For example, an ethylenically unsaturated, acid group-carrying monomer having a corresponding content of hydroquinone half-ether can be used to prepare the monomer solution. This stabilizer is sometimes also referred to as a "polymerization", even if it is intended only to inhibit uncontrolled or premature polymerization and no inhibition of the desired polymerization to the superabsorbent.

Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or alpha-tocopherol (vitamin E). These stabilizers require dissolved oxygen for optimal effect. Therefore, the monomer solution may be polymerized prior to polymerization by inerting, i. By flowing with an inert gas, preferably nitrogen or carbon dioxide, freed of dissolved oxygen and thus conveniently the stabilization of the monomer against polymerization are lowered. Preferably, the oxygen content of the monomer solution before polymerization is reduced to less than 1 ppm by weight, more preferably less than 0.5 ppm by weight, most preferably less than 0.1 ppm by weight.

Suitable crosslinkers b) are compounds having at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups which can be radically copolymerized into the polymer chain, and functional groups which can form covalent bonds with the acid groups of the monomer a). Furthermore, polyvalent metal salts which can form coordinative bonds with at least two acid groups of the monomer a) are also suitable as crosslinking agents b).

Crosslinkers b) are preferably compounds having at least two polymerizable groups which can be incorporated in the polymer network in free-radically polymerized form. Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane, as described in EP 530 438 A1. ben, di- and triacrylates, as in EP 547 847 A1, EP 559 476 A1, EP 632 068 A1, WO 93/21237 A1, WO 2003/104299 A1, WO 2003/104300 A1, WO 2003/104301 A1 and DE 103 31 450 A1, mixed acrylates which, in addition to acrylate groups, contain further ethylenically unsaturated groups, as described in DE 103 31 456 A1 and DE 103 55 401 A1, or crosslinker mixtures, as described, for example, in DE 195 43 368 A1, DE 196 46 484 A1, WO 90/15830 A1 and WO 2002/32962 A2.

Preferred crosslinkers b) are pentaerythritol triallyl ether, tetraalloxyethane, methylenebis-methacrylamide, 15-tuply ethoxylated methylolpropane triacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate and triallylamine.

Very particularly preferred crosslinkers b) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in WO 2003/104301 A1. Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol. Very particular preference is given to diacrylates or triacrylates of 1 to 5 times ethoxylated and / or propoxylated glycerol. Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerol, in particular the triacrylate of 3-times ethoxylated glycerol.

The amount of crosslinker b) is generally from 0.05 to 1, 5 wt .-%, particularly preferably 0.1 to 1 wt .-%, most preferably 0.3 to 0.6 wt .-%, each based on monomer a).

As initiators c) it is possible to use all compounds which generate free radicals under the polymerization conditions, for example thermal initiators, redox initiators or photoinitiators. Suitable redox initiators are sodium peroxodisulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, sodium peroxodisulfate / sodium bisulfite and hydrogen peroxide / sodium bisulfite. Often, mixtures of thermal initiators and redox initiators are used, such as sodium peroxodisulfate / hydrogen peroxide / ascorbic acid. However, the reducing component used is preferably a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite. Such mixtures are as Brüggolite ^® FF6 and FF7 Brüggolite ^® (Bruggemann Chemicals; Heilbronn; DE) available. However, the production of superabsorbent nonwovens is often photopolymerized, in which case suitable photoinitiators are used. Preferred initiators include water-soluble azo compounds such as 2,2'-azo-bis (2- (2-imidazol-2-yl)) propane dihydrochloride and 2,2'-azobis (amidino) propane dihydrochloride, water-soluble benzophenones such as 4-benzoyl N, N, N-trimethylbenzenethanaminium chloride, 2-hydroxy-3- (4-benzoylphenoxy) -3-N, N, N-trimethyl-1-propane ammonium chloride monohydrate, 2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioaxanthone-2-yloxy) -N, N, N-trimethyl-1-propanaminium chloride, 2-hydroxy-1 - [4- (4-one hydroxyethoxy) - phenyl] -2-methyl-1-propanone, 2-hydroxy-2-methyl-1-phenylpropan-1-one and 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo) 2-propenyl) oxy] ethylbenzolmethanaminiumchlond. A particularly preferred initiator combination contains both an azo initiator and 2-hydroxy-1- [4- (hydroxethoxy) phenyl] -2-methyl-1-propanone.

The monomer solution or suspension contains a sufficient amount of one or more initiators to polymerize the superabsorbent-forming monomer contained in the monomer solution or suspension. Typically, the amount of initiator is in the range of 0.01 to 5.0, and more preferably in the range of 0.2 to 2.0 weight percent, based on the weight of monomer a).

Examples of ethylenically unsaturated monomers d) which can be copolymerized with the ethylenically unsaturated monomers having acid groups are acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate. As water-soluble polymers e) it is possible to use polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, modified cellulose, such as methylcellulose or hydroxyethylcellulose, gelatin, polyglycols or polyacrylic acids, preferably starch, starch derivatives and modified cellulose. The monomer solution usually contains a solvent or suspending agent f). Since most of the solutions or relatively small proportions of insoluble components containing suspensions (for example, supersaturated solutions) is used, the following is for the sake of simplicity, only solutions of the following. Any solvent or solvent mixture can be used with which a satisfactory application of the monomer solution to the nonwoven fabric is possible. Mostly and preferably, water is used. The water content of the monomer solution is generally at least 40% by weight, preferably at least 45% by weight and more preferably at least 50% by weight, and generally at most 75% by weight, preferably at most 70% by weight in a particularly preferred form at most 65% by weight. If the monomer solution is applied by spraying on the nonwoven, the amount of water is adjusted so that a good sprayable solution is obtained. Optionally, this can also be achieved by using thickeners. In general, a viscosity of the spray solution of at least 20 centipoise, preferably at least 30 centipoise, and more preferably at least 40 centipoise, and generally at most 400 centipoise, preferably at most 150 centipoise and most preferably at most 100 Centipoise, each measured in a Brookfield viscometer set. With increasing water content, the energy expenditure increases during the subsequent drying and with decreasing water content, the heat of polymerization can only be dissipated insufficiently.

The monomer solution optionally contains further additives or auxiliaries. Examples of such additives or auxiliaries are hygroscopic substances, in particular sodium chloride, as described for example in WO 2006/106096 A1 or JP 05/105705 A, plasticizers, as described in WO 2007/023085 A1, thickeners or substances acting as such, for example finely divided particulate superabsorbents as described in WO 01/56625 A2.

The order of addition of the components of the monomer solution in the preparation of the monomer solution is not particularly important per se, but for safety reasons, it is preferred to add the initiator last.

To produce a superabsorbent nonwoven, the monomer solution is first applied to the nonwoven used as carrier material. Convenient methods of application include spraying or dropping the monomer solution onto the web or soaking the web with monomer solution, conveniently by passing a nonwoven web through the monomer solution in a padder or similar apparatus capable of applying predetermined amounts of a liquid to a fabric. The monomer solution is typically applied in amounts such that a final superabsorbent content after final drying of generally at least 20 g / m ² , preferably at least 40 g / m ² and more preferably at least 40 g / m ² and generally at most 700 g / m ² , preferably at most 500 g / m ² and in a particularly preferred form at most 400 g / m ^{2 is} achieved.

Preferably is sprayed. The spraying can take place by means of all conventional spraying devices, for example by nozzles. Both single-fluid nozzles and two-fluid nozzles, in which the monomer solution is atomized by a gas, can be used. As the gas, air or an inert gas such as nitrogen, argon or helium can be used. Preference is given to the use of air, nitrogen or a nitrogen-air mixture. The use of an inert gas such as nitrogen has the advantage of promoting the removal of oxygen from the monomer solution and thus reducing the polymerization inhibiting effect of stabilizers such as MEHQ.

After application of the monomer solution to the nonwoven, this condition is tered, where the monomers polymerize. For example, depending on the initiator contained in the monomer solution, these conditions include the action of heat, ultraviolet rays, electron beams, or their combination on the nonwoven fabric charged with the monomer solution. The polymerization may be carried out batchwise or continuously, for example by passing the nonwoven fabric charged with monomer solution through irradiation or heating sections on a conveyor belt.

When the polymerization is thermally initiated, the reaction device is not particularly limited. In the case of discontinuous polymerizations, the monomer solution applied to the nonwoven can be polymerized in an oven in air or in an inert atmosphere or else in vacuo. When continuously fed, the mat passes through a dryer, such as an infrared dryer, through-air dryer, or the like. The polymerization temperature is selected as a function of the thickness of the substrate, the monomer concentration and the type and amount of the thermal initiator used in the monomer solution so that complete polymerization, apart from the tolerable in each case residual monomer concentration, is achieved. The thermal polymerization is typically carried out in a temperature range from 20 ° C to 150 ° C, and preferably from 40 ° C to 100 ° C. The polymerization time depends on the polymerization temperature, but is typically in the range of a few seconds to 2 hours, and preferably in the range of several seconds to 10 minutes.

Upon initiation of polymerization by ultraviolet radiation, irradiation is conventionally effected using conventional UV lamps. Irradiation conditions, such as irradiation intensity and time, depend on the type of fibrous substrate used, the amount of monomer applied to the substrate, the amount and amount of initiator, and are chosen according to the art. Typically, the irradiation is carried out using a UV lamp with an intensity in the range of 100 to 700 watts per inch, preferably in the range of 400 to 600 watts per inch, with a distance between UV lamp and substrate between 2 to 30 centimeters , over a period of 0.1 seconds to 10 minutes. The irradiation with ultraviolet rays may be carried out under vacuum, in the presence of an inert gas such as nitrogen, argon, helium and the like, or in air. The irradiation temperature is not critical, whereby the irradiation of the sprayed fleece can be carried out with satisfactory results, usually at room temperature.

To initiate the polymerization by means of electron beams, for example, a commercially available electron acceleration device like the Electrocurtain ^® CB is 175 (Energy Sciences, Inc., Wilmington, USA). In the range of 150 to 300 kilovolt operating accelerometers are usable. The typically in the range of 1 to 10 milliampere beam current of such systems can on the desired te dose of ionizing radiation can be adjusted. The particular dose of ionizing radiation will vary somewhat depending on such factors as the presence or absence of crosslinking monomers, the desired degree of polymerization of the polymer, the degree of crosslinking desired, and the like. In general, it is desirable to irradiate the nonwoven web charged with monomer solution with doses of about 1 to 16 megarads, and preferably 2 to 8 megarads. In particular, when using low doses, it is desirable to deoxygenate the monomer solution, for example, by bubbling nitrogen through the solution prior to application to the web. The dose is preferably chosen so that no fiber degradation occurs.

After the polymerization, superabsorbent nonwoven fabric is usually dried, for example, by drying in a convection oven, passing through a hot air dryer, passing through a lit with infrared lamps route or other suitable and known measures and apparatus for drying fabric webs. It is dried until the desired moisture content of the superabsorber is reached.

The nonwoven used as a carrier material can be applied to one or both sides with monomer solution and irradiated. If desired, the superabsorbent fleece can be aftertreated. Examples of possible post-treatments are the application of plasticizers, surfactants, other textile auxiliaries, the setting of a desired moisture content or the surface postcrosslinking (often also only postcrosslinking) of the superabsorbent particles The measures can also be combined.

Suitable surface postcrosslinkers are compounds containing groups that can form covalent bonds with at least two carboxylate groups of the polymer particles. Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides, as described in EP 83 022 A2,

EP 543 303 A1 and EP 937 736 A2, di- or polyfunctional alcohols, as described in DE 33 14 019 A1, DE 35 23 617 A1 and EP 450 922 A2, or ß-hydroxyalkylamides, as in DE 102 04 938 A1 and US 6,239,230. DE 40 20 780 C1 also discloses cyclic carbonates, in DE 198 07 502 A1 2-oxazolidone and its derivatives, such as 2-hydroxyethyl-2-oxazolidone, in DE 198 07 992 C1 bis- and poly-2-oxazolidinones , in DE 198 54 573 A1 2-oxotetrahydro-1,3-oxazine and its derivatives, in DE 198 54 574 A1 N-acyl-2-oxazolidones, in DE 102 04 937 A1 cyclic ureas, in DE 103 34 584 A1 bicyclic Amidacetals, described in EP 1 199 327 A2 oxetanes and cyclic ureas and in WO 2003/31482 A1 morpholine-2,3-dione and its derivatives as suitable postcrosslinkers. Preferred secondary crosslinkers are ethylene carbonate, ethylene glycol diglycidyl ether, reaction products of polyamides with epichlorohydrin and mixtures of propylene glycol and 1,4-butanediol. Very particularly preferred postcrosslinkers are 2-hydroxyethyloxazolidin-2-one, oxazolidine-2-one and 1,3-propanediol. It is also possible to use postcrosslinkers which contain additional polymerizable ethylenically unsaturated groups, as described in DE 37 13 601 A1.

If postcrosslinking, the amount of postcrosslinker is generally 0.001 to 2 wt .-%, preferably 0.02 to 1 wt .-%, particularly preferably 0.05 to 0.2 wt .-%, each based on the amount of superabsorbent in the fleece. In a further embodiment of the present invention, polyvalent cations are applied to the particle surface before, during or after the post-crosslinking in addition to the postcrosslinkers or as postcrosslinkers. The polyvalent cations which can be used in the process according to the invention are, for example, divalent cations, such as the cations of zinc, magnesium, calcium, iron and strontium, trivalent cations, such as the cations of aluminum, iron, chromium, rare earths and manganese, tetravalent cations, such as the cations of Titanium and zirconium. As the counterion, chloride, bromide, sulfate, hydrogensulfate, carbonate, hydrogencarbonate, nitrate, phosphate, hydrogenphosphate, dihydrogenphosphate and carboxylate, such as acetate and lactate, are possible. Aluminum sulfate is preferred. Apart from metal salts, polyamines can also be used as polyvalent cations.

The amount of polyvalent cation used is, for example, 0.001 to

1, 5 wt .-%, preferably 0.005 to 1 wt .-%, particularly preferably 0.02 to

0.8% by weight. in each case based on the polymer particles.

The post-crosslinking is usually carried out so that a solution of the postcrosslinker is sprayed onto the dried superabsorbent web. Following spraying, drying is carried out, the postcrosslinking reaction taking place both before and during drying. Spraying (in principle, application by impregnation is also possible) and drying are carried out as described above for the polymerization of the monomer solution.

The postcrosslinkers are typically used as an aqueous solution. About the content of non-aqueous solvent or total amount of solvent, the penetration depth of the postcrosslinker can be adjusted in the superabsorbent particles. If only water is used as the solvent, it is advantageous to add a surfactant. As a result, the wetting behavior is improved and the tendency to agglomerate is reduced. However, preference is given to using solvent mixtures, for example isopropanol / water, 1,3-propanediol / water and propylene glycol / water, the mixing mass ratio preferably being from 20:80 to 40:60. After application of the superabsorbent hydrophilic fibers are introduced into the superabsorbent web thus produced. In contrast to fibers, including hydrophilic ones, which were already part of the fleece when the superabsorber was applied, these subsequently introduced fibers do not carry any superabsorbent particles. They ultimately serve to fill up the relatively large pores of the original superabsorbent web so as to improve the caching and distribution of liquid.

As hydrophilic fibers it is possible to use all of the abovementioned inherently hydrophilic fibers or hydrophilicized by additional measures, which may also already be the original constituent of the nonwoven.

Examples of inherently hydrophilic or optionally hydrophilized fiber materials which can be used according to the invention are monocomponent fibers such as fibers of polyethylene, polypropylene, nylon 6, nylon 6,6, nylon 12, copolyamide, polyesters such as polyethylene terephthalate ("PET"), polyethylene Terephthalate copolymers or mixtures thereof or bicomponent fibers such as polypropylene / polyethylene terephthalate fibers, polyethylene / PET, polypropylene / nylon 6, nylon 6 / ΡΕΤ, polytrimethylene terephthalate, polyethylene terephthalate, polytetramethylene terephthalate, copolyester / PET, copolyester / nylon-6, copolyester / nylon-6, 6, poly-4-methyl-1-pentene / PET, poly-4-methyl-1-pentene / nylon-6, poly-4-methyl-1 - Pentene / nylon-6; poly-4-methyl-1-pentene / nylon-6,6; PET / polyethylene naphthalate (PEN); nylon-6,6 / poly-1,4-cyclohexane-dimethyl (PCT ), Polypropylene / polybutylene terephthalate (PBI), nylon 6 / copolyamide, polylactic acid / polystyrene, polyurethane / acetal or soluble copolyester / polyet Hylen.

Further examples of suitable fibrous materials are cellulose and cellulose derivatives, such as cellulose or cellulose derived from wood or cellulose, cellulose, cellulose acetate, wood fibers, polyvinyl alcohol or polyacrylate. Preferably, cellulose or polyester fibers are used.

The hydrophilic fibers typically have a length of about 1.0 millimeter to about 50 millimeters and a diameter of about 0.5 microns to about 100 microns.

The hydrophilic fibers may be incorporated into the superabsorbent web by any known method of incorporating fibers into a web. Such methods are known in particular from felt production. A very simple method is the rolling in of scattered fibers, another the needling of a Superabsorbervlie- ses with scattered hydrophilic fibers. This can be done from one side, but also from both sides of the fleece. The textile according to the invention can additionally be aftertreated by any known measure. In particular, when used for moisture regulation, it can be laminated with an outer fabric and also contain further layers in addition to the outer fabric and superabsorbent nonwoven. These are chosen according to the purpose. Examples of possible further layers are, for example, a structuring layer under a synthetic leather outer material, spacer fabrics and flame-laminated foams, a back textile protective or reinforcing layer or a water-impermeable back layer.

The textiles according to the invention are outstandingly suitable for the absorption of liquids, for example in hygiene articles, but also for moisture regulation, in particular in mattresses and seat cushions, for example in seating or car seats and in other interior linings or floor mats. Sanitary articles, seat cushions or mattresses containing at least one textile according to the invention have excellent absorption and regulating ability for moisture.

Claims

claims

1 . Superabsorber-containing textile containing after the application of superabsorbent introduced hydrophilic fibers.

2. textile according to claim 1, characterized in that it is a non-woven.

3. Textile according to one of claims 1 or 2, characterized in that it is a polyester fiber fleece.

4. Textile according to one of claims 1 to 3, characterized in that the hydrophilic fibers are cellulose fibers

5. Textile according to one of claims 1 to 4, characterized in that the superabsorbent is a crosslinked polymer based on partially neutralized acrylic acid.

6. A process for producing a textile as defined in claims 1 to 5, comprising the steps

i) applying a monomer mixture to a textile,

ii) polymerization of the monomer mixture to form a superabsorbent, and iii) incorporation of hydrophilic fibers.

7. The method according to claim 6, characterized in that the monomer mixture contains partially neutralized acrylic acid and a crosslinker.

8. The method according to any one of claims 6 or 7, characterized in that the acrylic acid is neutralized to at least 25 mol%.

9. The method according to any one of claims 6 to 8, characterized in that hydrophilic fibers are introduced by walking or needling in the textile.

10. Use of textiles according to one of claims 1 to 5 for the absorption of liquids.

1 1. Use of textiles according to one of claims 1 to 5 for moisture regulation.

12. hygiene articles, seat cushions or mattresses, containing at least one textile according to one of claims 1 to 5.