EP0193107B1 - Bonded textile fabric and method for its production - Google Patents

Description

Field of the Invention

The invention relates to a method for producing bound textile fabrics by applying an acrylic resin dispersion which is free of formaldehyde and formaldehyde-releasing substances. The invention further relates to the textile fabrics produced by the method.

Aqueous acyl resin dispersions whose plastic content contained self-crosslinking amide methylol groups have hitherto been used frequently for the production of bound textile fabrics which are notable for high wet strength and for water and wash liquor resistance. When drying the treated fabric, small amounts of fomaldehyde could be released, whereas there are health concerns. We are therefore looking for binders for textile fabrics which provide sufficient wet strength, water and wash liquor resistance for practical purposes, but do not give off any formaldehyde when heated.

State of the art

It is known from DE-OS 32 02 122. to solidify To apply fibrous structures formaldehyde- and acrylonitrile-free acrylic resin dispersions, the resin component of which is composed of acrylic or methacrylic esters, a small proportion of hydroxyalkyl esters of unsaturated carboxylic acids and optionally small amounts of acrylic or methacrylic acid. Although textile fabrics equipped therewith have a higher wet strength than those whose binder does not contain the mentioned hydroxyalkyl ester component, the wet strength still leaves something to be desired. EP-A 19 169 describes aqueous dispersions which are suitable as binders for nonwoven fabrics and which contain, as binders, a copolymer of acrylic or methacrylic esters or other monomers and 3 to 10% by weight of units of acrylamidoglycolic acid. It is therefore a binder that does not release formaldehyde when heated. However, since the desired wet strength of the textile fabrics finished with them is not achieved with these binders, small proportions of N-methylolacrylamide are polymerized into the copolymers, thereby increasing the wet strength of the finished fiber structures. however, the risk of formaldehyde release occurs again.

EP-A 96 230 describes coating compositions which contain, as self-crosslinking binders, copolymers of acrylic monomers and a crosslinking system composed of methyl acrylamido-glycolic acid methyl ether and hydroxyl, carboxy or amido-functional comonomers. When heated, condensation reactions of the monomer units, the crosslinker system mentioned, occur. It is not known to use such copolymers as binders for textile fabrics.

Task and solution

The invention has for its object to produce bonded fabrics with improved wet strength, from whose binder no formaldehyde is released when heated.

The task is solved by a

80 - 99 Gew.-%

Acryl- und/oder Methacrylsäurealkylestern mit 1 bis 8 C-Atomen im Alkylrest oder deren Gemisch mit Styrol,

1 - 10 Gew.-%

eines Acrylamidoglykolsäure-Monomeren

0 - 20 Gew.-%

weiteren Comonomeren,
das dadurch gekennzeichnet ist,

daß als Bindemittel eine Dispersion eines Mischpolymerisats eingesetzt wird, dessen Acrylamidoglykolsäure-Einheiten sich von Monomeren der Formel I

ableiten, worin R ein Wasserstoffatom oder eine Methylgruppe, R' ein Alkylrest und R'' ein Wasserstoffatom oder ein Alkylrest sind.Process for the production of bonded textile fabrics by applying a binder containing an aqueous dispersion of a copolymer

80-99% by weight

Acrylic and / or methacrylic acid alkyl esters with 1 to 8 carbon atoms in the alkyl radical or their mixture with styrene,

1 - 10% by weight

of an acrylamidoglycolic acid monomer

0 - 20% by weight

other comonomers,
which is characterized by

that a dispersion of a copolymer whose acrylamidoglycolic acid units are different from monomers of the formula I is used as the binder

derive, wherein R is a hydrogen atom or a methyl group, R 'is an alkyl radical and R''is a hydrogen atom or an alkyl radical.

application

The bonded fabrics made according to the invention are distinguished from those with conventional formaldehyde-free binders by a significantly increased wet strength. This is important in cases where the bound textile fabric is exposed to mechanical stress during manufacture, further processing or when used in the wet state. A typical application is the production of bonded nonwovens based on synthetic fibers, in particular polyester fibers, which are used for the production of so-called disposable diapers. Here, the bonded non-woven fabrics form the outer cover of the diaper, which envelops a highly absorbent filler. Due to the low water absorption of the synthetic fibers, the outer shell still appears relatively dry when the coated insert has absorbed considerable amounts of liquid. However, it is essential that the outer casing does not tear under mechanical stress and exposes the liquid-saturated insert.

Implementation of the invention

als Bestandteil des in der wäßrigen Dispersion enthaltenen Mischpolymerisats. R, R' und R'' haben die im Anspruch 1 angegebene Bedeutung. Vorzugsweise ist R'' eine Alkylgruppe. R' und R'' können gleiche Alkylreste, insbesondere Methylgruppen sein. Es kommen jedoch auch andere Alkylreste mit vorzugsweise nicht mehr als 8 C-Atomen in Betracht, insbesondere niedere Alkylreste mit bis zu 4 C-Atomen.The increased wet strength of the textile fabrics bound in the sense of the invention is based on the units of an acrylamidoglycolic acid monomer of the formula

as a component of the copolymer contained in the aqueous dispersion. R, R 'and R''have the meaning given in claim 1. Preferably R "is an alkyl group. R 'and R''can be the same alkyl radicals, especially methyl groups. However, other alkyl radicals with preferably no more than 8 carbon atoms are also suitable, in particular lower alkyl radicals with up to 4 carbon atoms.

The acrylic or methacrylic acid alkyl esters forming the main part of the copolymer, or their mixture with styrene, are selected in a manner known _{per se} so that the dynamic freezing _temperature T _{1max is} not more than 60 °, preferably not more than 20 ° C. In typical cases, the copolymer consists of 30 to 60 wt .-% of monomer units that give hard homopolymers, such as methyl, ethyl, propyl, isopropyl methacrylate or styrene, and about 20 to 70% acrylic acid esters of C₁₋₈ alkanols or methacrylic acid esters of C₄₋₈ alkanols.

Unsaturated carboxylic acids such as acrylic or methacrylic acid are suitable as further monomer components Amounts of about 1% by weight improve the stability of the dispersion. Crosslinking comonomers, such as glycol dimethacrylate, allyl methacrylate, methylene-bis-methacrylamide or butanediol diacrylate, can also improve the strength properties of the binder in small amounts. Too high a proportion of crosslinking agents would interfere with the film formation process and should therefore be avoided. The comonomers which can also be used also include acrylonitrile and methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride and others. Hydroxyesters and amides of acrylic or methacrylic acid are generally not present in the copolymers.

The acrylic resin dispersions can be prepared by all common methods of emulsion polymerization. They can contain anionic, cationic or non-ionic emulsifiers or compatible mixtures thereof. They are expediently produced with solids contents of 50 to 70% by weight.

The method of the invention is suitable for binding and solidifying textile fabrics of all kinds; these include woven fabrics, knitted fabrics, wadding and in particular non-woven nonwovens. The invention is not restricted to certain types of fibers, but synthetic fibers or fiber mixtures containing synthetic fibers are fundamentally preferred. These mixtures can contain, for example, 70% or more of synthetic fibers. The synthetic fibers considered include fibers made from regenerated cellulose, such as rayon or rayon, and in particular fully synthetic fibers, such as polyester or polypropylene fibers. Preferred textile fabrics are constructed from 70 to 100% by weight of polyester fibers and 0 to 30% by weight of cellulose.

Solidification of fiber structures

The preparation of the dispersion for the consolidation of fiber structures depends on the application process and the requirements placed on the end product. The additives used in these processes. like wetting agents. Anti-foaming agents, thermosensitizers. Plasticizers and smoothing agents. Antistatic. Antimicrobials. Dyes, fillers, flame retardants, fragrances, etc. can also be used. In general, the dispersions are diluted with water to a binder content of 10 to 40 percent by weight. The viscosity of the diluted dispersion can range from 10 to 10,000 mPa.s. For the consolidation of wadding, for example made of polyester, polyamide or polyacrylonitrile fibers, an approximately 15 to 25% liquor is sprayed on. Compact nonwovens and needle felts can be solidified well by impregnation with 10 to 40% liquors and subsequent squeezing and drying. Light fiber fleeces can also be consolidated by foam impregnation; To do this, foaming agents and foam stabilizers are added to the approximately 10 to 25% dispersion and foamed with air up to a liter weight of 100 to 300 g. The impregnation is expediently carried out on the horizontal foulard. Very light non-woven fabrics can be partially solidified by printing with pastes that contain 20 to 40% binder and are adjusted to a viscosity of 4000 to 8000 mPa.s. Needle felts for high-quality floor and wall coverings are preferably splashed with thickened, possibly foamed liquors. Finally, nonwoven bonding is also possible by brushing.

The solidified fiber structures generally contain between 5 and 100%, based on the fiber weight, of binder. The preferred binder content is between 10 and 30% by weight. The fiber structures equipped according to the invention obtain their favorable application properties only by drying at dryer temperatures above 110 ° to about 200 °, preferably in the range between 120 and 160 ° C.

If additional resistance of the solidified fiber structure to organic solvents is required, a crosslinking agent, for example glyoxal, can be added to the dispersion.

Examples Preparation of a dispersion A which can be used according to the invention

In a reaction vessel equipped with a stirrer, thermometer and reflux condenser, 40 parts by weight of fully demineralized water are heated to 80 ° C. and 0.02 part by weight of the sodium salt of a sulfated addition product of triisobutylphenol and 7 moles of ethylene oxide and 0.04 part by weight. Parts of ammonium peroxodisulfate are added. For this purpose, an emulsion of 57 parts by weight of n-butyl acrylate and 39.5 parts by weight of methyl methacrylate is metered in within 4 hours. 3-5 parts by weight of acrylamidomethylglycolate methyl ether, 61.5 parts by weight of fully deionized water, 1.5 parts by weight of the sodium salt of a sulfated addition product of triisobutylphenol and 7 moles of ethylene oxide and 0.25 part by weight of ammonium peroxodisulfate. For postpolymerization, the batch is kept at 80 ° C. for 2 hours. A stable, coagulate-free dispersion with a solids content of approx. 50% is obtained.

Preparation of a comparison dispersion B without acrylamidoglycolic acid monomer units

In a polymerization vessel equipped with a reflux condenser, stirrer and thermometer, one of 44 parts by weight of methyl methacrylate, 56 parts by weight of n-butyl acrylate, 61.5 parts by weight of completely deionized water, 1.5 parts by weight of the sodium salt of a sulfated Addition product consisting of triisobutylphenol and 7 moles of ethylene oxide and 0.25 part by weight of ammonium peroxodisulfate in the course of 4 hours of a solution of 0.04 part by weight of ammonium peroxodisulfate heated to 80 ° C. and 0.02 part by weight of the above-mentioned emulsifier in 40 parts by weight of deionized water were added with stirring. The temperature is then kept at 80 ° C. for a further 2 hours. A stable coagulate-free dispersion of approximately 50% solids content is obtained.

Strengthening of fiber structures and application testing

To determine the breaking resistance, thermally pre-consolidated polyester fleece with a weight per unit area of approx. 18 g per m² is impregnated with the plastic dispersion diluted to approx. 25% dry matter, excess dispersion squeezed out with the padding so that a resin coating of approx. 15% is achieved. The damp fleece is dried in the stenter at 140 ° C for 5 minutes. The breaking resistance is determined according to DIN 53 857, Part 2 on dry fleece (F) and on wet fleece (F _n ) after 1 hour of water storage in the middle of a tensile testing machine that corresponds to DIN 51 221.
In order to demonstrate the advantageous applicability of the binders according to the invention also on hydrophilic fiber structures, a chromatography paper (No. 1, Whatman) is impregnated in the same way as indicated above for the polyester fleece. The resin layer is approx. 30%. The breaking resistance is determined according to DIN 53 112, sheets 1 and 2.

The results of the application test are summarized in the following table. The values represent mean values from 12 individual determinations.

Example 1 illustrates the invention using dispersion A.

Example 2 is a comparative test with comparative dispersion B which was not prepared according to the teaching of the invention.
Example 3 is a comparison test according to DE-OS 32 02 122.

Claims (11)

1. Process for producing bonded flat textile structures by applying a binder, containing an aqueous dispersion of a copolymer of
      80-99 wt.-% of alkyl acrylates and/or methacrylates having 1 to 8 C atoms in the alkyl moiety or a mixture thereof with styrene,
      1-10 wt.-% of an acrylamidoglycolic acid monomer,
      0-20 wt.-% of other comonomers,
      characterised in that the binder used is a dispersion of a copolymer the acrylamidoglycolic acid units of which are derived from monomers of formula I

   

   wherein R is a hydrogen atom or a methyl group, R' is an alkyl group and R'' is a hydrogen atom or an alkyl group.
2. Process according to claim 1, characterised in that a fibre fleece is used as the flat textile structure.
3. Process according to claim 2, characterised in that a fibre fleece made up entirely or predominantly of synthetic fibres is used.
4. Process according to claim 3, characterised in that a fibre fleece is used, the synthetic fibre content of which consists at least partly of polyester fibres.
5. Process according to one or more of claims 1 to 4, characterised in that, in the acrylamidoglycolic acid units of formula I, R'' is an alkyl group.
6. Bonded flat textile structure containing as binder a copolymer of
      80-99 wt.-% of alkyl acrylates and/or methacrylates having 1 to 8 C atoms in the alkyl moiety or a mixture thereof with styrene,
      1-10 wt.-% of acrylamidoglycolic acid monomer of formula I,
      0-20 wt.-% of other comonomers.
7. Bonded fibre fleece according to claim 6, characterised in that, in the acrylamidoglycolic acid units of formula I, R'' is an alkyl group.
8. Bonded flat textile structure according to claim 6 or 7, characterised in that it is a bonded, non-woven fibre fleece.
9. Bonded fibre fleece according to claim 8, characterised in that the fibre content consists wholly or predominantly of synthetic fibres.
10. Bonded fibre fleece according to claim 9, characterised in that the synthetic fibres consist wholly or predominantly of polyester fibres.
11. Bonded fibre fleece according to claim 9 or 10, characterised in that it contains 10 to 40 wt.-% of the binder.