CA2107716A1

CA2107716A1 - Compostable nonwoven bonded with a saccharide graft polymer

Info

Publication number: CA2107716A1
Application number: CA002107716A
Authority: CA
Inventors: Renate Wuestefeld; Karl-Heinz Schumacher; Howard Peter Kirsch
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1992-10-06
Filing date: 1993-10-05
Publication date: 1994-04-07
Also published as: EP0591821A1; EP0591821B1; DE59305131D1; JPH06192537A; CN1094422A; FI934386A; FI934386A0

Abstract

Abstract of the Disclosure: A nonwoven suitable for composting is bonded with from 5 to 100% by weight, based on the weight of the fibers used, of a polymer which has a glass transition temperature of from -70 to +40°C and is preparable by free radical polymerization of a mixture of ethylenically unsaturated monomers in an aqueous medium in the presence of a saccharide, the monomer mixture comprising from 0.5 to 15% by weight of N-alkylolamides of ,-monoethylenically unsaturated carboxylic acids having from 3 to 10 carbon atoms, acrylamidoglycolic acid, methacrylamidoglycolic acid and/or their ethers and esters or ether-esters with alcohols having up to 12 carbon atoms.

Description

2 ~ ~ 7 7 ~ ~ o. z . 0050/43607 COMPOSTABLE NON~OVEN BONDED WITH A SACCHARIDE
GRAFT POLYMER
The present invention relates to a nonwoven bonded with from 5 to 100% by weight, based on the weight of the fibers used, of a polymer which has a glass transition temperature of from -70 to ~40C and is preparable by free radical polymerization of ethylenically unsaturated monomers in an aqueous medium in the presence of a saccharide.
Nonwovens are generally flexible textile sheet materials formed by consolidating or bonding loose accumulations of individual fibers, ie. fiber webs. The consolidation or bonding of fiber webs to form bonded fiber webs, ie. nonwovens, by impregnating with aqueous polymer dispersions and subsequent evapora~ion of the water is generally known.
Because they are comparatively inexpensive to produce, compared with woven and knitted fabrics, non-wovens have found wide use in disposable textile pro-ducts. Examples are diapers, wipes and medical articlessuch as sanitary towels or sheets and blankets.
These products generally require high strength not only in the dry but also in the wet state combined with a soft character. In addition, products which are to come into more or less intimate contact with man have to meet increasing requirements in respect of their toxicological safeness.
As the volume of these disposable articles increases and society is becoming ever more concerned about the problem of waste, interest is beginning to focus on how to dispose of the used articles. Hitherto disposal has been chiefly by landfilling. Given that landfill space is becoming scarce and landfilling itself is becoming politically less acceptable, it would be extremely desirable to dispose of the nonwoven-containing disposable articles by the ideal alternative of composting. The product should therefore be readily compostable, ie. successfully rot down in . , : ....... . . . ; , . ::

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: ... . ~ ,-, 2~71~ o.z 0050/43607 composters. On coming into contact with earth the products should therefore quickly lose their strength and disintegrate.
DE-A-2 361 468 describes a nonwoven composed of short fibers such as cellulose fibers and a binder comprising a mixture of a polymer of ethylenically unsaturated monomers and naturally occurring polymers such as gelatin, collagen or starch. The mixture is applied to the fiber web from an aqueous medium and water is removed. However, the nonwovens thus formed are unsatisfactoLy in that they have unsatisfactory properties. For instance, the wet strength and the softness of these products are unsatisfactory.
US-A-3 651 210 describes a reactive copolymer of certain, inter alia oxirane-containing, monomers and proteins such as casein or soybean as coating material or adhesive. German Patent Application P 41 08 170.6 discloses free-radically polymerizing ethylenically unsaturated monomers in emulsion in the presence of proteins such as casein. The products are used to produce films and coatings, for example on paper.
Neither reference makes any suggestion of using polymers prepared in the presence of starch for bonding fiber webs. Moreover, the nonwovens obtained on using the graft polymers disclosed in P 41 08 170.6 for bonding are insufficiently water-resistant and too stiff.
EP-A-345 566 concerns web bonders based on a copolymer of hydroxyl-free monomers and hydroxyl-` 30 containing components such as polyvinyl alcohol, starch, starch derivatives or colloidal cellulose.
These web bonders are crosslinked by adding 1,3-dimethyl-4,5-dihydroxyimidazolidone to the polymer.
However, these products have poor wet strength and 35 unsatisfactory softness.
` It is an object of the present invention to y avoid the disadvantages of the prior art and to provide ~ nonwovens that have balanced properties and are .

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3 -2~ a77i~,o-z 0050/43607 compostable. The products should combine high dry strength, good wet strength and a soft character with good compostability.
We have found that this object is achieved by the nonwovens defined at the beginning. We have also found a process for consolidating fiber webs. Preferred embodiments are disclosed in the subclaims.
Suitable materials for the fiber webs are fibers which are biodegradable. These are generally 10 fibers having a diameter of from 0.002 to 0.1 mm, preferably from 0.01 to 0.05 mm, which can be determined for example in a conventional manner by means of electron micrographs. The fibers used are in general natural fibers of cellulosic origin, such as viscose fibers or cellulose fibers, or synthetic fibers, such as aliphatic polyester fibers, for example based on copolymers of 3-hydroxybutyrate, 3-hydroxyvalerate and 4-hydrooxyvalerate, as described in EP-A-466 050.
The forming of webs from the fibers is generally known (Rompp, Chemielexikon, Georg Thieme Verlag, Stuttgart - New York, 9th Edition, p. 4560).
They can be random-laid fiber webs or preferably oriented fiber webs with or without mechanical preconsolidation, for example by needling, entangling or knit-sewing.
The fiber webs are bonded with from 5 or more, ` preferably 11 or more, in particular 15 or more, especially 20 or more , ~ by weight and 100 or less, preferably 50 or less, in particular 35 or less, ~ by Iweight, each based on the amount of fiber web used, of ,~ the polymer.
The grafting of ethylenically unsaturated mono-mers on to starch is known, for example from EP-A-35 134 449, EP-A-334 515, EP-A-408 099 and German Patent Application P 41 33 193.1. Starch graft polymers are recommended for paper sizing (EP-B-257 412) as additiments to washing and cleaning agents or to paper ~: . - . ~ . . . , , . .. . .... , - .

.. . . .

~ Z 0050/43607 coating compositions (EP-A 441 197), for molds for metal casting (German Patent Application P 41 33 190.7) and for abrasives (German Patent Application P ~1 33 191.5).
The polymers used according to the invention have a glass transition temperature of from -70 to 40, preferably from -60 to 0C. This glass transition temperature is measurable in a conventional manner as laid down in ASTM 3418/82 (midpoint temperature).
Suitable free-radically polymerizable monomers are in particular monoethylenically unsaturated monomers such as olefins having up to 4 carbon atoms, eg. ethylene, aromatic vinyl monomers having up to 10 carbon atoms such as styrene, a-methylstyrene, ortho-chlorostyrene or vinyl toluenes, vinyl and vinylidene halides, such as vinyl and vinylidene chloride, esters of vinyl alcohol and monocarboxylic acids having from 1 to 18 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of ,-monoethylenically unsaturated mono- and dicarboxylic acids having preferably from 3 to 6 carbon atoms, in particular acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with alkanols having in general from 1 to 12, preferably from 1 to 8, in particular from 1 to 4, carbon atoms, in particular methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and 2-ethylhexyl methacrylate, dimethyl maleate or n-butyl maleate, nitriles of said ,-mono-ethylenically unsaturated carboxylic acids, such as acrylonitrile or methacrylonitrile, and also C4 to C8-conjugated dienes, such as 1,3-butadiene and isoprene.
In many cases it is advantageous for the proportion of the nitriles to be less than 15% by weight, preferably 0% by weight, of the total amount of monomers used.

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5 -2 ~ ~ 7 7 ~j-Z 0050/43607 The monomers mentioned are essentially insoluble in the aqueous medium and in general form the main monomers which, based on the total amount of the monomers used, normally account for a proportion of more than 50% by weight.
There are used crosslinking monomers in amounts of from 0.5 to 15, preferably from 0.5 to 10, % by weight, in particular from 1 to 6% by weight, based on the total amount of the monomers used, which do not undergo crosslinking until the polymer has been dried, and then the crosslinking reaction can be speeded up by heating with or without the addition of catalysts, for example proton-eliminating substances such as maleic acid, diammonium hydrogenphosphate or ammonium nitrate.
Examples of such monomers are n-alkylolamides of ,-monoethylenically unsaturated carboxylic acids having from 3 to 10 carbon atoms, of which N-methylolacrylamide and N-methylolmethacrylamide are preferred. Particular preference for use as crosslinking monomers is given to acrylamidoglycolic acid and methacrylamidoglycolic acid and their ethers, esters or ethyl-esters with alcohols such as alkanols having up to 12 carbon atoms, for example acrylamidomethoxyacetic acid, methyl acrylamidohydroxy acetate, methyl acrylamidomethoxy acetate, meth-acrylamidomethoxyacetic acid, methyl methacrylamido-hydroxy acetate, methyl methacrylamidomethoxy acetate, the corresponding butyl and butoxy derivatives, butyl acrylamidobutoxy acetate and butyl methacrylamidobutoxy acetate. Ammonium salts of the tmeth)acrylamido acids mentioned are also suitable. These crosslinking systems do not give off any toxicologically suspect formaldehyde in the crosslinking reaction. The free ` (meth)acrylamidoglycolic acid is very particularly ; 35 preferred.
Other monomers which polymerized by themselves usually result in water-soluble homopolymers are normally incorporated into the copolymer only in :~ .

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2 ~ ~ 7 7 ~ ~ Z 0050/43607 modifying amounts, based on the total amount of the monomers used, of less than 50% by weight, generally from 0 to 15, preferably from 1 to 10, ~ by weight.
Examples of such monomers are ,-monoethylenically unsaturated mono- and dicarboxylic acids having from 3 to 6 carbon atoms and amides thereof, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide, also vinylsulfonic acids and their water-soluble salts, vinylphosphonic acid, its salts and esters with alcohols having up to 4 carbon atoms and also N-vinylpyrrolidone and 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate or dimethylaminoethyl acrylate.
Preferred polymers arise from - 70-99.5% by weight of esters of acrylic and/or methacrylic acid with alkanols having from 1 to 12 carbon atoms, styrene, butadiene, vinyl acetate and/or propionate, - 0.5-15% by weight of crosslinking monomers, and - 0-15% by weight of other monomers.
Particularly preferred polymers arise from monomer mixtures comprising from 90 to 99.5, preferably from 94 to 99, ~ by weight of esters of acrylic and/or methacrylic acid with alkanols having from 1 to 12, in particular from 1 to 8, carbon atoms and from 0.5 to 10, preferably from 1 to 6, % by weight of acrylic acid, methacrylic acid and~or in particular acrylamidoglycolic acid, methacrylamidoglycolic acid, and the abovementioned derivatives of these acids, of which acrylamidoglycolic acid and methacrylamido-glycolic acid are very particularly preferred.
The weight percentages mentioned each relate to the total amount of the ethylenically unsaturated mono-mers used.
The monomers mentioned are generally polymerized by the method of free radical aqueous emulsion polymerization. It is in fact a yraft poly~erizatLon in the presence of saccharides.

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~ 7 ~ 21 ~ 60.Z 0050/436o7 Saccharides for the purposes of the present invention are monosaccharides, oligosaccharides and poly-saccharides and derivatives thereof.
Monosaccharides include the pentoses (C5H10O5) and hexoses (C6H12O6). Oligosaccharides are for example dimers or trimers of monosaccharides. Prefe~ence is given to using derivatives of the mono- and oligosaccharides such as the acetals with C6-C18-alkanols. Suitable are octyl-D-glucoside, decyl-D-glucoside and dodecyl-D-glucoside, tetradecyl-D-glucoside, hexadecyl-D-glucoside, octadecyl-D-glucoside and mixtures thereof.
The polysaccharides used are advantageously -glycosidically linked.
Preferred polysaccharides have a weight average molecular weight of from 1000 to 25000, preferably from 1000 to 13000, in particular from 2000 to 9000, msasur-able by gel permeation chromatography in conventional manner.
The polysaccharides can be of vegetable or animal origin, water-soluble or only water-dispersible.
Suitable are inter alia the swellable starches which are obtainable for example by hydrothermal treatment of native starch. Also suitable are thin-boiling starches.
These are starches which have been slightly degraded with acids or enzymes or oxidized with mild oxidizing agents and which when boiled with water do not form viscous gels but remain relatively thin liquids, even at high concentrations. It is also possible to use acid-modified starches which are obtained by heating an aqueous starch suspension at below the gelatinization temperature in the presence of small amounts of acids.
Also suitable are oxidatively modified starches.
Suitable oxidizing agents include for example chromic 135 acid, permanganate, hydrogen peroxide, nitrogen jdioxide, hypochlorite or periodic acid. The starting `~starch can in principle be any native starch such as cereal starch (eg. corn, wheat, rice or millet), tuber ~, .
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- 8 - 2 ~ ~ 7 ~1 ~o. z 0050/43607 or root starch (eg. potato, tapioca or arrowroot) or sago starch. It i5 advantageous to use roast dextrins as described for example in EP-A-408 099 and EP-A-334 515. They are obtainable by heating moist-dry starch, usually in the presence of small amounts of acid. Typical roast dextrins are for example commercially available white and yellow d~xtrins; they also include dextrins available under the trade marks Noredux and Tackidex. Herein the term dextrin is used generally in respect of starch degradation products.
However, it is very particularly advantageous to carry out the free radical emulsion polymerization in the presence of saccharified starches. These are starch degradation products obtainable by hydrolysis in aqueous phase. The` results are aqueous polymer dispersions which in addition to high mechanical and thermal stability have good rheological properties even after storage. Further details of the preparation of the starch and starch derivatives mentioned can be found in G. Tegge, Starke und Starkederivate, Behr's Verlag, Hamburg 1984. Of course, the starches and starch derivatives mentioned can also be used for the purposes of the invention when chemically modified, for example by etherification or esterification.
This chemical modification can be carried out on the starting starch prior to its degradation or thereafter. Esterifications are possible not only with inorganic but also with organic acids, their anhydrides or chlorides. Of particular interest are phosphated and acetylated derivatives. The most widely used m0thod of etherification is the treatment with organic halogen compounds, epoxides or sulfates in aqueous alkaline solution. Particularly suitable ethers are alkyl ethers, hydroxyalkyl ethers, carboxyalkyl ethers and allyl ethers. Also possible are cyanalkylated ` derivatives and also reaction products with 2,3-epoxypropyltrimethylammonium chloride. However, products which have not been chemically modified are .,.
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- 9 -2 ~ 7 ~ ~ ~ - Z 0050/43607 preferred. It is also possible to use degradation products of cellulose, for example cellobiose and oligomers thereof.
The saccharified starches which are very particularly preferred for use according to the invention are those which are commercially available (for example the C PUR products 01906, 01908, 01910, 01912, 01915, 01921, 01924, 01932 or 01934 from Cerestar). Such saccharified starches differ chemically from the roast dextrins, inter alia because in hydrolytic degradation in aqueous medium (usually suspensions or solutions, usually carried out at solids contents of from 10 to 30% by weight and preferably with acid or enzyme catalysis) there is essentially no scope for recombinatlon and branching, as results not least in different molecular weight distributions. For instance, saccharified starches which have a bimodal molecular weight distribution have proved particularly advantageous for the purposes of the invention. The preparation of saccharified starches is generally known and described inter alia in G. Tegge, Starke und Starkederivate, Behr's Verlag, Hamburg 1984, page 173 and page 220 ff. and also in EP-A-441 197.
Saccharified starches are normally completely soluble in water at room temperature, the solubility limit being in general above S0% by weight, which is particularly advantageous for preparing aqueous polymer dispersions.
It has also been found to be advantageous for the saccharified starches to have a polydispersity P
(defined as the ratio of the weight average molecular weight MW to the number average molecular weight Mn tmeasurable by gel permeation chromatography); P
characterizes the molecular weight di~tribution) within the range from 6 to 12.
It is also of advantage for the weight proportion of the saccharified starches which has a .

2 ~ ~ 7 7 ~ ~
molecular weight below 1000 to be at least 10% by weight, but not more than 70% by weight.
It is also advisable to use saccharified starches whose dextrose equivalent DE is from 5 to 40.
The DE value characterizes the reducing power relative to the reducing power of anhydrous dextrose and is determined according to DIN 10 308 Edition 5.71 of the Specialist Committee on Foods and Agricultural Products, (cf. also Gunther Tegge, Starke und Starke-derivate, Behr's Verlag, Hamburg 1984, page 305).
It has also been found that aqueous polymer dispersions which are particularly advantageous in their property profile are obtained on using saccharified starches whose 40% strength by weight 15 aqueous solutions have a dynamic viscosity 40 [Pa-s] of from 0.005 to 0.06, preferably from 0.005 to 0.03, at 25C and a shear gradient of 75 5-l when determined according to DIN 53 019.
The saccharides present during the free radical 20 aqueous emulsion polymerization can be present not only as individual dispersants but also mixed with other surface-active substances. They are normally present in the aqueous polymer dispersions in amounts, based on the ~mount of monomers used, of from 1 to 50, 25 preferably from 3 to 30, % by weight.
~ Suitable concomitant surface-active substances `~ include in principle the protective colloids and emulsifiers of an anionic, cationic or nonionic kind w~ich are usually used as dispersants. A detailed 30 description of suitable protective colloids is given in Houben-Weyl, Methoden der organischen Chemie, Volume ~IV/l, Makromolekulare Stoffe, Georg. Thieme Verlag, ` Stuttgart, 1961, pages 411 to 420. The concomitant i surface-active substances used are preferably 35 exclusively emulsifiers whose molecular weights, in contradistinction to the protective colloids, are usually below 2000. Of course, if mixtures of surface-Y active substances are used, the individual components .

11 2 ~ ~ 7 7 ~ ~ . z 0050t43607 have to be compatible with one another, which in case of doubt can be verified by means of a few preliminary experiments. The concomitant surface-active substances used are preferably anionic or nonionic emulsifiers.
Customary concomitant or coemulsifiers include for example ethoxylated fatty alcohols (degree of ethoxylation (EO): from 3 to 50, alkyl radical: C8-C36), ethoxylated mono-, di- and trialkylphenols (EO
degree: 3-50, alkyl radical: C4-Cg), ethoxylated alcohols (EO degree: 4-30, alkyl radical: C12-C18), ethoxylated alkylphenols (EO degree: 3-50, alkyl radical: C4-Cg), alkali metal salts of dialkyl esters of sulfosuccinic acid and also alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C8-C12), of alkyl sulfonic acids (alkyl radical: C12-C18), of alkyl diphenyl oxide sulfonic acids (alkyl radical:
C12-C18) and of alkylarylsulfonic acids (alkyl radical:
Cg-Cl8) and the corresponding acids. Further suitable emulsifiers are given in Houben-Weyl, Methoden der organischen Chemie, Volume XIV/l, Makromolekulare Stoffe, Georg. Thieme Verlag, Stuttgart, 1961, pages 192 to 208. Preference is given to those surface-active substances which are biodegradable and are toxico-logically safe and have toxicologically safe degradation and secondary products, such as sodium lauryl sulfate. The surface-active substances are in general used in amounts of from 0 to 5, preferably from 0.1 to 1, % by weight, based on the amount of monomers to be polymerized.
The polymerization temperature is in general from 30 to 95, preferably from 75 to 90C. The polymer-ization medium can consist not only of water but also of mixtures of water and water-miscible liquids such as methanol. Preference is given to using water only.
Emulsion polymerization is carried out in customary ~ apparatus equipped with mixing elements, for example i stirred flasks, kettles, autoclaves and cylindrical reactors. It can be carried out batchwise or continu-i : : - ~ ,, . :

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~ - 12 - O.Z 0050/43607 21~7~
ously, for example in kettle cascades or other inter-connected polymerization apparatus. It can be carried out not only as a batch process but also in the form of a feed stream addition process, including stages or with a gradient. Preference is given to the feed stream addition process in which part of the polymerization batch is introduced as the initial charge, heated to the polymerization temperature and polymerized incipiently and then the remainder of the polymerization batch is added, usually in a plurality of spatially separate streams, of which one or more contain the monomers in pure or in emulsified form, continuously, stagewise or under superposition of a concentration gradient while the polymerization in the polymerization zone is maintained. From an application point of view it is advantageous for the initial charge and/or the monomer stream to contain small amounts of emulsifiers, based on the total amount of the monomers to be polymerized, in general less than 0.5% by weight in order that the surface tension of the dispersing medium may be reduced and so the stirring in may be facilitated. Frequently the monomers are therefore introduced in the polymerization zone preemulsified with these auxiliary emulsifiers. Advantageously the total amount of the saccharide to be used is present in the aqueous initial charge, generally in dissolved form.
Suitable free radical polymerization initiators include all those capable of initiating a free radical aqueous emulsion polymerization. These can be not only peroxides, for example alkali metal peroxodisulfates, ammonium peroxodisulfate or H2O2 but also azo compounds.
It is also possible to use combined systems composed of at least one organic reducing agent and at least one peroxide and/or hydroperoxide, for example tert-butyl hydroperoxide and the sodium salt of hydroxymethanesulfinic acid or hydrogen peroxide and . . .

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- 13 -2 1 ~ 7 7 1 60. Z 0050/436o7 ascorbic acid. It is also possible to use combined systems which in addition contain a small amount of a metal compound that is soluble in the polymerization medium and whose metallic component can exist in more than one valence state, for example ascorbic acid/iron(II) sulfate/hydrogen peroxide, although in the case of ascorbic acid it is also common to employ the sodium salt of hydroxymethanesulfinic acid, sodium sulfite, sodium bisulfite or sodium metabisulfite and instead of hydrogen peroxide it is common to employ tert-butyl hydroperoxide or alkali metal peroxodisulfates and/or ammonium peroxodisulfates. In general the amount of free radical initiator systems used, based on the total amount of the monomers to be polymerized, is from `0.1 to 2% by weight. Particular preference is given to using ammonium and/or alkali metal peroxydisulfates by themselves or as part of combined systems as initiators.
The free radical aqueous graft polymerization can if desired be carried out in the presence of regulators. ~uitable regulators include for example mercapto compounds, such as mercaptoethanol, merca~topropanol, mercaptobutanol, mercapto acetic acid, mercapto propionic acid, butyl mercaptan and dodecyl mercaptan. Other suitable regulators are allyl compounds such as allyl alcohol. If the graft polymerization is carried out in the presence of regulators, they are used in amounts of from 0.05 to ~ 20% by weight, based on the monomers used in the `! 30 polymerization.
Of course, the free radical aqueous polymer-, ization of the invention can also be carried out under ~`` superatmospheric or reduced pressure.
The aqueous polymer dispersions are in general prepared with total solids contents of from 15 to 65,preferably from 30 to 60, % by weight.
The polymer dispersions may be admixed with customary additives. They are in general added after .~
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j' ' ' '' . ~: . , ' ~ . ' . : ' ' ` . . ' -- - 14 - 2 f~ 7 1~- z 0050/43607 the polymerization has ended. Suitable are crosslinkinq nonpolymerizable substances, which can usually be present in amounts of from 0.1 to 5% by weight. If the polymer contains free carboxyl groups, it is possible to use compounds which can crosslink such groups, such as basic compounds of polyvalent metals such as zinc oxide, calcium oxide or the corresponding hydroxides, acetates or carbonates or the corresponding mixed salts. It is also possible to use compounds which crosslink any hydroxyl groups present, such as di- and polyfunctional inorganic acids and acid derivatives, eg. phosphoryl chloride, alkali metal trimetaphosphates, alkali metal polyphosphates or alkali metal tetraborate, di- and polyfunctional organic acids, eg. adipic acid, citric acid, 1,2,3,4-butanetetracarboxylic acid, all-cis-1,2,3,4-cyclo-pentanetetracarboxylic acid, derivatives of di- and polyfunctional organic acids, such as anhydrides or mixed anhydrides, eg. diacetyl adipic acid, acetyl-citric anhydride, acid chlorides, eg. cyanuricchloride, imidazolides and guanidine derivatives, also di- and polyfunctional isocyanates such as hexamethylene diisocyanate, 2,4-diisocyanate toluene, di- and polyfunctional alkylating agents, eg.
epichlorohydrin, ,'-dichloroethyl ether, diepoxides, various aldehydes or aldehyde derivatives such as formaldehyde, acetaldehyde, acrolein, 2,5-dimethoxytetrahydrofuran or glutardialdehyde. It is also possible to use condensation products based on formaldehyde, glyoxal, melaminel phenol and/or urea.
The formaldehyde and the formaldehyde-containing crosslinker systems are less suitable because of toxicological reservations.
The additives customary for nonwovens can be added in known amountsl biodegradable substances being preferred. To preserve the product properties the non-wovens are frequently free of clay or chalk.

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The fiber w0bs are consolidated with the polymers by known methods (eg. Ullmann's Encyklopadie der technischen Chemie, 4th Edition, Volume 23, 1983, pages 738 to 742). The fiber web is usually saturated with the polymer dispersion by bath impregnation, foam impregnation, spraying, padding or printing. For this the dispersion may be diluted with water or else thickened with customary thickeners to achieve the desired processing viscosity. The treatment of the web with the dispersion is generally followed by a drying and heat treatment of the resulting bonded fiber web nonwoven. The drying conditions depend on the nature of the dryer used, but usually the drying temperature is within the range from 100 to 230C and the drying and/or heat treatment takes from 10 sec to 60 min.
The nonwovens of the invention combine good compostability with favorable performance character-istics. They have inter alia dry strength, wet strength and a soft hand. The wet strength of the products is surprising, since saccharides are hydrophilic substances, so that the wet strength was completely unforeseeable. Since oligo- and polysaccharides are known hard substances, owing to the numerous hydrogen bonds, the soft character of the nonwovens according to the invention is lik~wise surprising.
EXAMPLES
The polysaccharides used were the starches C
PUR 01915 or 01934 from Cerestar Deutschland GmbH, D-1150 Krefeld 12. They all have essentially a bimodal molecular weight distribution and are characterized as ~ follows:
j Type MW U % by wt. DE 40 < 1000 [Pa-s]
01915 6680-8350 6.8-8.~ 32.9-34.7 17-19 0.021 ` 35 01934 3000 6.0 ~8.4 36-39 0.009 ill Determination of Mn by means of vapor pressure osmosis gave the following value for the 01915:

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980 g/mol MW and P were determined by gel permeation chromatography in a conventional manner using the follow 5 ing parameters:
Columns: 3 off 7.5 @ 600 mm steel packed wLth TSK gel G 2000 PW; G 3000 PW and G 4000 PW. Pore size 5 ~m Mobile phase: Distilled water 10 Temperature: RT (room temperature) Detection: Differential refractometer (eg.
ERC 7511) Flow rate: 0.8 ml/min. Pump: (eg. ERC 64.00) Injection volume: 20 ~l valve: (eg. VICI 6-way ~alve) 15 Evaluation: Bruker Chromstar GPC software Calibration: In the low molecular weight region with glucose, raffinose, maltose and maltopentose. In the high molecular weight region with pullulan standards having polydispersity ~ 1.2.

A mixture of 766 g of water, 100 g of starch 01915 (from Cerestar) and 2.2 g of commercial emulisifer based on an alkyl diphenyl oxide sulfonic acid (Dowfax 2A1 from Dow) is heated to 85C and admixed with 20% by weight of stream 2 and 5 min later with 10~ by weight of stream 1. After 15 min at 85C
for incipient polymerization the metered addition is begun of the remainders of streams 1 and 2.- The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2). This is followed by postpolymerization at 85C for 1 h, cooling and addition at an internal temperature of ~ 30C of 2.9 g of t-butyl hydroperoxide (70% strength by weight in water). 5 min later a mixture of 2 g of sodium salt of hydroxylmethanesulfinic acid, 0.1 g of ammonium iron II
sulfate, 0.5 g of sodium salt of ethylenediaminetetra--:
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` - 17 ~ 2 ~ ~ 7 7 ~ ~j Z 0050/43607 acetic acid and 10 g of water is added over 15 min and subsequently stirred in for 30 min.
The solids content of the aqueous polymer dispersion: about 44% by weight, measured according to 5 DIN 53 189.
Glass transition temperature of film formed from a polymer dispersion (film thickness: 0.5 mm, drying: 30 h at room temperature): -42C
Stream 1:
380 g of water 950 g of n-butyl acrylate g of acrylic acid g of acrylamidoglycolic acid 2.2 g of Dowfax 2A1 (45% strength by weight in water) Stream 2:

6 g of sodium peroxodisulfate 200 g of water A mixture of 365 g of water and 35 g of starch 01915 is heated to 85C and admixed with 20% by weight of stream 2 and 5 min later with 10% by weight of stream 1. After 15 min at 85C for incipient polymeri~-ation the metered addition is begun of the remainders of streams 1 and 2. The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2).
This is followed by postpolymerization at 85C for 1 h, cooling down and addition at an internal temperature of 70C of 1.4 g of t-butyl hydroperoxide (70% strength by weight in water). 5 min later a mixture is added of 1 g of sodium salt of hydroxylmethanesulfinic acid, 0.05 g of ammonium iron II sulfate, 0.25 g of sodium salt of ethylenediaminetetraacetic acid and 5 g of water over 60 min followed by cooling down to room temperature.
Solids content of the aqueous polymer disper-sion: about 44% by weight.
Glass transition temperature: -12C (determined as described in Example 1) .~ . .
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Stream 1:
190 g of water 483 g of ethyl acrylate 17.5 g of acrylamidoglycolic acid 5.6 g of Dowfax 2Al (45% strength by weight in water) Stream 2:
3 g of sodium peroxodisulfate 100 g of water A mixture of 882 g of water, 63 g of starch 01915 and 2.8 g of Dowfax 2Al is heated to 85C and admixed with 20% by weight of stream 2 and 5 min later with 10% by weight of stream 1. After 15 min at 85C
for incipient polymerization the metered addition is begun of the remainders of streams 1 and 2. The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2). This is followed by postpolymerization at 85C for 1 h, cooling down and addition at 70C of 3.6 g of t-butyl hydroperoxide (70~
strength by weight in water~. 5 min la~er a mixture is added of 2.5 g of sodium salt of hydroxylmethanesulfinic acid, 0.13 g of ammonium iron II sulfate, 0.63 g of sodium salt of ethylenediamine-, 25 tetraacetic acid and 12.5 g of water over 15 min and subsequently stirred in for 30 min.
Solids content of the aqueous polymer disper-sion: about 44% by weight.
Glass transition temperature: -34C (determined as described in Example 1) ~Stream 1:
475 g of water 875 g of n-butyl acrylate 300 g of ethyl acrylate g of acrylic acid g of acrylamidoglycolic acid 14 g of Dowfax 2A1 (45% strength by weight in water) '~ .
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Stream 2:

7.5 g of sodium peroxodisulfate 250 g of water A mixture of 383 g of water, 50 g of starch 01934 and l.11 g of Dowfax 2Al is heated to 85C and admixed with 20% by weight of stream 2 and 5 min later with 10% by weight of stream l. After 15 min at 85C
for incipient polymerization the metered addition is begun of the remainders of streams 1 and 2. The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2). This is followed by postpolymerization at 85C for 1 h, cooling down and addition 70C of 1.4 g of t-butyl hydroperoxide (70%
strength by weight in water). 5 min later a mixture is ~.
added of 1 g of sodium salt of hydroxylmethanesulfinic acid, 0.05 g of ammonium iron II sulfate, 0.25 g of sodium salt of ethylenediaminetetraacetic acid and 5 g of water over 15 min and subsequently stirred in for 30 min.
Solids content of the aqueous polymer disper-sion: about 44% by weight. :
Glass transition temperature: -11C (determined as described in Example 1) Stream 1: .
190 g of water 483 g of ethyl acrylate 17.5 g of acrylamidoglycolic acid 5.6 g of Dowfax 2A1 (45% strength by weight in water) Stream 2:
3 g of sodium peroxodisulfate 100 g of water :.

A mixture of 826 g of water, 2.5 g of sodium acetate and 62.5 g of starch 01934 is heated to 85C
and 20% of stream 3 and 36% of stream 1 are added. This - 20 - O.Z 0050/43607 ~a7~
is followed by 15 min at 85C for incipient polymeriz-ation and then the remainder of stream 1 and 27~ of stream 3 are metered in over an hour. On completion of the addition of stream 1, stream 2 and the remainder of stream 3 are added over 1.5 h (stream 2) and 2 h (stream 3). This is followed by 1 h at 85C for incipient polymerization, cooling down to 70C and addition of 8.3 g of hydrogen peroxide (30% strength in water). 5 min later a mixture 2.5 g of ascorbic acid, 0.08 g of ammonium iron II sulfate and 13 g of water is added over 1 h, and the mixture is stirred for 30 min and cooled down to room temperature.
Total solids content of the aqueous polymer dispersion: about 43%.
Glass transition temperature: 0C
Stream 1:
140 g of water 338 g of ethyl acrylate 12 g of acrylamidoglycolic acid 12 g of Steinapol NLS (15% strength in water) Stream 2:
360 g of water 287 g of ethyl acrylate 581 g of vinyl propionate 32 g of acrylamidoglycolic acid g of Steinapol NLS (15% strength in water) Stream 3:
7.S g of sodium peroxodisulfate 250 g of water [Steinapol NLS = sodium lauryl sulfate]

644 g of water are introduced as initial charge, heated to 85C and admixed with 20% of stream 2 and 10% of stream 1. This is followed by 15 min at 85C
for incipient polymerization and then the metered addition is begun of the remainders of streams 1 and 2.
The addition takes place continuously over 2.5 h , ,,.~ , , , . ~:

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2 ~ ~ 7 r~ 1 ~ Z 0050/43607 (stream 1) and 3 h (stream 2). This is followed by postpolymerization at 85C for 1 h, cooling down to 70C and addition of 2.9 g of t-butyl hydroperoxide (70% strength in water). 5 min later a mixture is added of 2 g of sodium salt of hydroxylmethanesulfinic acid, O.1 g of ammonium iron II sulfate, 0.5 g of sodium salt of ethylenediaminetetraacetic acid and 10 g of water over 1 h, and the mixture is subsequently stirred for 30 min and cooled down to room temperature.
Solids content of the aqueous polymer disper-sion: about 45 ~.
Glass transition temperature: -11C
Stream 1:
380 g of water 965 g of ethyl acrylate g of acrylamidoglycolic acid 11.1 g of Dowfax 2A1 (45% strength in water) 67 g C8-C10-glucoside (55% strength in water) Stream 2:
6 g of sodium peroxodisulfate 200 g of water t The C8 C10-glucoside used was prepared as ; described in German Patent Application DE-P 4212080.2 by the following method:
25 A 2-1 multi-neck stirred reactor equipped with baffles, disk stirrer, thermometer, stillhead, and a metering unit comprising a metering pump, a pressure control valve and a nozzle was charged with 663 g of Lorol C8_10 Spezial (Henkel, mixture of octanol and decanol), followed by 2.6 g (0.008 mol) of dodecyl-benzenesulfonic acid. This mixture was admixed with 121.6 g of an alkylglucoside/alcohol emulsifier mixture i (composition: 63% of Lorol, 22.6% of C12-monoglucoside, .`~ 5.2% of C12-diglucoside, 2.2~ of C12-triglucoside, 0.7%
of C12-tetraglucoside, < 0.5~ of C12-pentaglucoside, 5.9~ of polyglucose). The glucose-containing portions of the emulsifier amounted to 30~, based on the glucose . ~

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- 22 2-1 Q ~ - Z 0050/43607 used. The molar ratio of fatty alcohol to glucose was 6:1.
The solution was heated to 115-120C. 214 g (0.83 mol) of a 60C dextrose syrup (70~ strength solu-tion, glucose content about 99.5~) was metered in undera reduced pressure of from 30 to 35 mbar in such a way as to produce a cloudy emulsion containing virtually no particulate precipitates of polyglucose. After 4 h metering and 30 min stirring, 83 g of water were dis-tilled off. This left a slightly cloudy, pale yellowreaction solution.
After cooling down to 90C, the catalyst was deactivated with 1.6 g of 50~ strength sodium hydroxide solution, the resulting solution having a pH of 8.3 (measured in 50% strength aqueous solution). The excess alcohol was removed by means of a thin-film evaporator (heating temperature 170C, runoff temperature 140C) at a vacuum of 1 mbar. The product was made with water directly into an aqueous solution and bleached with 12.3 g of H2O2 (30% strength solution) at 80C.

661 g of water are introduced as initial charge, heated to 85C and admixed with 20% of stream 2 and 10~ of stream 1. This is followed by 15 min at 85C
for incipient polymerization and then the metered addition is begun of the remainders of streams 1 and 2.
The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2). This is followed by postpolymerization at 85C for 1 h, cooling down to 70C and addition of 2.9 g of t-butyl hydroperoxide (70% strength in water). 5 min later a mixture is added of 2 g of sodium salt of hydroxylmethanesulfinic acid, 0.1 g of ammonium iron II sulfate, 0.5 g of sodium salt of ethylenediaminetetraacetic acid and 10 g of water over 1 h, and the mixture is subsequently stirred for 30 min and cooled down to room temperature.
Solids content of the aqueous polymer disper-sion: about 44%.

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Stream 1:
380 g of water 965 g of ethyl acrylate g of acrylamidoglycolic acid 11.1 g of Dowfax 2Al (45% strength in water) g C10-Cl2-glucoside (47% strength in water) Stream 2:
6 g of sodium peroxodisulfate 200 g of water The C10-C12-glucoside used was prepared as des-cribed in Example 6, but using 754 g of Nafol@ 1012 (from Condea, mixture of decanol, dodecanol and small amounts of tetradecanol).

In a 2 l capacity glass apparatus equipped with horseshoe stirrer, addition means for monomers, initiator solutions and ammonia solution, reflux ; condenser and nitrogen inlet and outlet, 120 g casein (in the acid form) are suspended in 500 g of water under nitrogen at 20C. Then 180 g of n-butyl acrylate are added in one portion and the mixture is stirred at 20C for 15 min. Then 9 g of 25~ strength aqueous ammonia solution are added dropwise over lS min. After the ammonia has been added, the mixture is stirred at 20C for a further 40 min. Then 20 g of a 13% strength by weight sodium peroxide sulfate solution are added in one portion and the temperature of the reaction mixture is increased to 75C.
As that temperature is reached, 20 g of a 10~
strength by weight sodium peroxide sulfate solution are added over 2 h and the reaction mixture is subsequently ~; stirred at 70C for a further 2 h. Then 1 g of t-butyl `~ perpivalate is added and the mixture is stirred at 75C
for a further 2 h.

Example 4 was repeated with the starch being added after the polymerization was over.

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' - - 24 - O.Z 0050J43607 2~7~ "., The starch mixture used was an emulsion polymer based on styrene/butadiene, prepared without saccharide and having a glass transition temperature of -16C.

A mixture of 832 g of water and 2.8 g of Dowfax 2Al is heated to 85C and admixed with 20~ of stream 2 and 10%
of stream 1. After 15 min at 85C for incipient polymerization the metered addition i5 begun of the remainders of streams 1 and 2. The addition takes place continuously over 2.5 h (stream 1) and 3 h (stream 2).
This is followed by postpolymerization at 85C for 1 h, cooling down to 70C and addition of 3.6 g of t-butyl hydroperoxide (70~ strength in water). 5 min later a mixture is added of 2.5 g of sodium salt of hydroxylmethanesulfinic acid, 0.13 g of ammonium iron II sulfate, 0.63 g of sodium salt of ethylenediamine-tetraacetic acid and 13 g of water over lh, and is subse~uently stirred for 30 min and cooled down to room temperature.
Total solids content of the aqueous polymer dispersion: about 44%.
Stream 1:
475 g of water 875 g of butyl acrylate 300 g of ethyl acrylate g of hydroxyethyl acrylate g of acrylic acid 3014 g of Dowfax 2Al (45~ ~trength in water) : . Stream 2:
7.5 g of sodium peroxodisulfate 250 g of water To 700 parts by weight of the polymer dispersion is added a mixture of 38.5 parts by weight of a solution of 1,3-dimethyl-4,5-dihydroxyimidazolidin-2-one (40~ strength in water) and ~:i :: - .. . .

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31 parts by weight of citric acid (25~ strength in water) and stirred in for 5 min.
Making of nonwovens:
A longitudinally oriented (fiber orientation preferentially in one direction, the longitudinal direction) cellulose fiber web having a basis weight of 35 g/m2 was impregnated in separate runs with the dispersions of the above-described examples and comparative examples, which had first been diluted to a uniform solids content of 10%, passed between two contrarotating rolls to remove excess dispersion, and then exposed to a temperature of 150C for 4 min. The binder content of the nonwovens thus obtained was in all cases 25~ by weight.
Investigations of nonwovens:
The nonwovens were cut into 50 mm wide strips and these strips were subjected to a strip tensile test analogously to DIN 53 857 in the dry and in the water-wet state, with a free clamp length of 10 cm, to determine the breaking strength transversely (through appropriate cutting out of the test specimens) to the preferential fiber direction.
Furthermore, the nonwoven specimens were bent around a metallic mandrel to determine the bending stiffness, which is used as a measure of softness. The bending stiffness is the force which had to be applied to achieve bending. This force was measured transversely to the preferential fiber direction.
The results of the these experiments are shown in Table 1.
,Examples and Tensile strength [N] Bending Comparative Examples Dry Water-wet stiffness [mN]
Example 1 33 8 24 Example 2 34 9 41 Example 3 31 13 21 Example 4 33 8 24 Example 5 13 - 26 ~ ~ 7 7 i' ~ o. z ~050/43607 Example 6 13 Example 7 11 Comparative Example 1 91 < 1 130 Comparative Example 2 12 20 Comparative Example 3 47 13 30 Comparative Example 4 10 6 20 To investigate the compostability of the non-wovens obtained according to the invention, they were tested in line with the burial test of DIN 53 933, ie.
buried in potting compost and left for a defined period of time. After the nonwovens had been dug back out, their breaking strength was determined and compared with the breaking strength of a corresponding sample which had not been buried to determine the loss of breaking strength due to burial in the compost. This loss of breaking strength is used as a measure of compostability. In addition, the nonwoven specimens were visually inspected in respect of their degree of disintegration. The higher the breaking strength loss and the greater the visually detectable disintegration of the specimens, the better the compostability of the nonwovens.
The nonwovens for the composting trials were ,produced as described above, but the raw web used was a .125 lightly preneedled viscose staple web having a basis weight of 50 g/m2. The results of the composting trials are summarized in Table 2:

Example Breaking strengthBreaking strength (dry) (dry) 9 d before burialafter burial ~ Example 1 27 N 5 N
`~, Example 3 25 N 13 N
1 35 Compa~ative Example 3 40 N 30 N
¦ Unconsolidated raw web 10 N 2 N

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71~ z 0050/43607 Visual assessment of the nonwoven specimens revealed that the specimens bonded with Comparative Example 3 showed hardly any visible disintegration after burial. Nonwovens bonded with Example 1 and Example 3, by contrast, showed distinct signs of disintegration: the specimens had become noticeably thinner and showed the odd small hole.

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Claims

1. A nonwoven bonded with from 5 to 100% by weight, based on the weight of the fibers used, of a polymer which has a glass transition temperature of from -70 to +40°C and is preparable by free radical polymerization of a mixture of ethylenically unsatur-ated monomers in an aqueous medium in the presence of a saccharide, the monomer mixture comprising from 0.5 to 15% by weight of N-alkylolamides of ,-monoethylenically unsaturated carboxylic acids having from 3 to 10 carbon atoms, acrylamidoglycolic acid, methacrylamidoglycolic acid or their ethers, esters or ether-esters with alcohols having up to 12 carbon atoms.

2. The nonwoven of claim 1, wherein the saccharide has a weight average molecular weight of from 1000 to 25000.

3. The nonwoven of claim 1, wherein the saccharide used is dextrin.

4. The nonwoven of claim 1, wherein the saccharide used is a starch degradation product obtainable by hydrolysis in aqueous phase.

5. The nonwoven of claim 1, wherein the saccharide used is an acetal of a mono- or oligosaccharide with alkanols having from 6 to 18 carbon atoms.

6. The nonwoven of claim 1, wherein the polymer contains - from 70 to 99.5% by weight of esters of acrylic and/or methacrylic acid with alkanols having from 1 to 12 carbon atoms, styrene, butadiene, vinyl acetate and/or propionate, - from 0.5 to 15% by weight of N-alkylolamides of ,-monoethylenically unsaturated carboxylic acids having from 3 to 10 carbon atoms, acrylamidoglycolic acid, methacrylamidoglycolic acid or their ethers, esters or ether-esters with alcohols having up to 12 carbon atoms - from 0 to 15% by weight of other monomers.

7. A process for consolidating fiber webs, which comprises using from 5 to 100% by weight, based on the weight of the fibers used, of a polymer which has a glass transition temperature of from -70 to +40°C and is preparable by free radical polymerization of a mixture of ethylenically unsaturated monomers in an aqueous medium in the presence of a saccharide, the monomer mixture comprising from 0.5 to 15% by weight of N-alkylolamides of ,-monoethylenically unsaturated carboxylic acids having from 3 to 10 carbon atoms, acrylamidoglycolic acid, methacrylamidoglycolic acid or their ethers, esters or ether-esters with alcohols having up to 12 carbon atoms.

8. A method of using the nonwoven of claim 1 for manufacturing diapers.