CA2278946A1

CA2278946A1 - Textile fabrics

Info

Publication number: CA2278946A1
Application number: CA002278946A
Authority: CA
Inventors: Hermann Seyffer; Ralf Mossbach; Klaus Haas
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1998-07-28
Filing date: 1999-07-27
Publication date: 2000-01-28
Also published as: DE19833920A1; EP0976866A1; ATE281552T1; DE59910972D1; EP0976866B1; ES2232051T3

Abstract

Disclosed is a textile fabric comprising a web of fibers joined together by means of a polymeric binder, said fabric comprising an oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn in a state of colloidally disperse subdivision and a wetting agent selected from sulfosuccinates and sulfosuccinamates. The textile fabric is hydrophilic even after it has been repeatedly rinsed out.

Description

Textile fabrics Specification The present invention relates to textile fabrics comprising a web of fibers joined together by means of a polymeric binder, i.e., nonwoven fabrics, and a process for their production.
A nonwoven is produced by laying down a web of fibers which is subsequently consolidated or adhered together. The fibers can have a preferential direction or be randomly disposed. Various processes are known for forming the web, for example (1) mechanical webbing from staple fibers or filaments; (2) aerodynamic webbing from staple fibers or filaments; (3) hydrodynamic webbing from staple fibers or filaments; and (4) electrostatic webbing from very fine fibers or filaments. The webs obtained in this way are consolidated into nonwovens by various processes.
Wet processes are the most important. In these processes, the web is treated with an aqueous binder, for example a polymer latex, and subsequently, if necessary after removal of excess binder, dried and optionally cured. This basic principle has ultimately given rise to a large number of further developed processes.
Nonwovens are used in a large number of applications. For instance, nonwovens are increasingly used, for example, as cleaning cloths, wipes, dishcloths and napkins. In these applications, it is important that, for example, spilt liquids, such as milk, coffee, etc., be rapidly and completely absorbed when wiped away with the nonwoven and that moist surfaces be completely dried. The rate at which and the degree of completeness to which liquids are absorbed determine the performance characteristics of a wipe and are the main criteria for the quality of the wipe article.
The rate at which a wipe will absorb a liquid increases with the speed at which the liquid is transported on the fiber surface. A
hydrophilic surface is easily and rapidly wetted by water. The water will then spread very quickly over the entire surface of the nonwoven and will be "sucked away" from the point of contact.
Hydrophobic surfaces, in contrast, are not wetted. They therefore do not convey the liquid either and are unsuitable for application as a cleaning or wiping cloth. The amount of liquid which can be absorbed is decisively determined, inter alia, by the swelling behavior of the fiber. A hydrophobic binder forming substantially an envelope around the fiber impairs the kinetics of water absorption.
The water absorption properties of nonwovens are occasionally improved by using surface-active hydrophilicizing agents, such as emulsifiers, surfactants or wetting agents, in the course of their production. This does indeed provide excellent initial hydrophilicity. However, these nonwovens have the disadvantage that the hydrophilic agents are gradually washed off by water or other aqueous media. The product becomes increasingly more hydrophobic on repeated contact with water. After repeated rinsing, therefore, the dishcloth, cleaning cloth or wipe loses its ability to take up aqueous liquids rapidly. The cloth consequently loses its utility and has to be disposed of, even though its mechanical strength would be sufficient for further use cycles. This is undesirable in terms of a responsible handling of resources.
It is an object of the present invention to provide a hydrophilic textile fabric whose hydrophilicity survives repeated rinsing.
We have found that this object is achieved, surprisingly, by using certain oxides and/or hydroxides in a state of colloidally disperse subdivision in conjunction with certain wetting agents.
The present invention accordingly provides a textile fabric comprising a web of fibers joined together by means of a polymeric binder, said fabric comprising an oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn in a state of colloidally disperse subdivision and a wetting agent selected from sulfosuccinates and sulfosuccinamates.
The present invention further provides a process for producing a textile fabric by impregnating a web of fibers with a dispersion of a polymeric binder and drying and optionally curing the impregnated web, which comprises further impregnating said web with (i) a colloidal suspension of an oxide and/or hydroxide of Al, B, Si, Mg, Ti and/or Zn or a solution of a precursor of an oxide and/or hydroxide of Al, B, Si, Mg, Ti and/or Zn and inducing the formation of the oxide and/or hydroxide in a state of colloidally disperse subdivision and (ii) a wetting agent selected from sulfosuccinates and sulfosuccinamates.
Statements herein in relation to the textile fabric of the invention also apply, where appropriate, to the process of the invention, and vice versa.

The textile fabric of the invention preferably comprises 1 - 20g by weight, based on the dry weight of the polymeric binder, especially 3 - 15~ by weight, particularly preferably 5 - 15~ by weight, of oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn.
The textile fabric of the invention preferably comprises 1 - 20%
by weight, based on the dry weight of the polymeric binder, especially 2 - 10~ by weight, of wetting agent.
For the purposes of the present invention, "oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn" shall have a very wide meaning. As well as the simple oxides and hydroxides of the elements indicated, the expression shall encompass their hydrated forms of varying water content and the oxo anion salts with, for example, alkali metal or alkaline earth metal cations, for example the silicates and aluminates. The expression shall further encompass oxides and hydroxides in various states of condensation, for example the nesosilicates, amphiboles and phyllosilicates, and also mixed oxides and/or hydroxides.
Preferred oxides and/or hydroxides are silica, aluminum oxide, aluminum hydroxide, aluminosilicates, e.g., bentonites, montmorillonites.
The textile fabrics of the invention include, in uniformly dispersed form, a wetting agent selected from sulfosuccinates and sulfosuccinamates. The wetting agents used have in particular the following general structural formula II ii I

where M is an alkali metal, especially sodium, or one equivalent of an alkaline earth metal or ammonium, which may be substituted by from 1 to 4 C1-C4-alkyl or C1-C4-hydroxyalkyl groups;
X and Y, which may be identical or different, are each 0-(CnH2n0)m-Rr (CnH2n0)m-NHCOR, OM, OH, or NHR, Subject to the proviso that at least one of X and Y is not OM or OH, and R is linear or branched CS-C18-alkyl, C5-C18-alkenyl, C5-C18-cycloalkyl, (C1-C12-alkyl)aryl or phenyl;
n is an integer from 2 to 4; and m is an integer from 0 to 30.

It is particularly advantageous to use sulfosuccinic diesters in which the esterifying alcohols have a chain length of from 4 to 8 carbon atoms, e.g., sodium di(ethylhexyl) sulfosuccinate.
As to the fibers used, the invention is not subject to any significant restrictions. All fiber varieties are suitable which are currently used for producing nonwovens, e.g., polypropylene, polyester, polyamide fibers, cellulose fibers, such as viscose fibers, bicomponent fibers, e.g., polyester/copolyester, polypropylene/polyethylene, polyester/polyamide, polyester/polypropylene and nylon-6/nylon-6,6 fibers. Further suitable fibers are polyacrylonitrile, polyimide, polytetrafluoroethylene and polyphenylene sulfide fibers, mineral fibers or glass fibers and semisynthetic fibers, such as acetate fibers. Polypropylene fibers, polyester fibers and cellulose fibers and blends thereof are preferred.
All customary polymeric binders can be used. This includes in particular the polyacrylate dispersions, for example on the basis of C1-C4-alkyl (meth)acrylates, (meth)acrylic acid and/or (meth)acrylamide. Amide polymers or copolymers can be crosslinked with N-methylol compounds, such as urea-formaldehyde or melamine-formaldehyde resins. Internal crosslinking takes place on incorporating N-methylol(meth)acrylamide. It is also possible to use rubber latices, for example synthetic styrene-butadiene rubbers (SBR) and acrylonitrile-butadiene rubber (NBR), polyvinyl ester dispersions, optionally copolymerized with ethylene and/or vinyl chloride, for example copolymers of vinyl acetate and ethylene or vinyl acetate, vinyl chloride and ethylene, and also polyvinyl alcohols. It is further possible to cite polyurethane dispersions and also aminoplast and phenoplast precondensates.
Preference is given to the use of a binder comprising a polymer of monomers selected from the group consisting of C1-C4-alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamide, N-methylol(meth)acrylamide, styrene, butadiene, (meth)acrylonitrile, vinyl C1-C6-alkanoates, vinyl chloride, ethylene and vinyl alcohol. The amount of binder used, expressed as dry binder on the basis of the total weight of the consolidated nonwoven, is generally within the range from 10 to 40~ by weight, preferably about 20~ by weight.
It is of critical importance for the present invention that the oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn be present in the nonwoven of the invention in a state of colloidally disperse subdivision. Noncolloidal, coarser particles, as occasionally used as antiblocking additives or other aggregates, do not provide the desired effect. By colloidally disperse is meant that the majority of the particles, e.g., more than 90~ by weight, of the oxide and/or hydroxide are < 1 N.m, especially < 0.1 Eun, in size. The state of colloidally disperse subdivision can be achieved in the context of the present invention, for 5 example, by starting from a colloidal suspension of the oxide and/or hydroxide, for example a sol, such as a hydrosol, or a gel, or else by inducing the formation of the oxide and/or hydroxide in colloidally disperse form, for example in the form of a gel, within the web.
The web may be impregnated with the binder dispersion by all common impregnating methods, for example impregnation using an impregnator or in a pad-mangle. When the oxide and/or hydroxide forms a stable colloidal suspension in the presence of the polymeric binder, it is advantageous to incorporate the oxide and/or hydroxide into the binder dispersion. In this way, it-is possible to process, for example, colloidal.silicas. Colloidal dispersions of certain oxides and/or hydroxides cannot be prepared in situ in the binder dispersion. For instance, A13+
salts tend to coagulate the dispersion or, to be more precise, a coagulation occurs when it is attempted to convert the A13+ salts into A1(OH)3 by addition of a base, for example ammonia. In these cases, it is advantageous for the web to be impregnated with a colloidal suspension, preferably with a freshly prepared colloidal suspension, in the form of a sol or gel and dried and then impregnated with the polymeric binder. On the other hand, it is possible to impregnate the web with the solution of a precursor of the oxide and/or hydroxide and to induce the formation of the oxide and/or hydroxide in the web. For instance, the web can be saturated, for example, with a solution of A13+
ions, for example an A12(S04)3 solution or an A1(N03)3 solution, and preferably dried. It is only then that the web is impregnated with the binder dispersion. The neutral to slightly alkaline pH
of the dispersion leads to conversion of the A13+ ions into A1(OH)3. If necessary, the binder dispersion may have a pH
regulator, for example a buffer, added to it so as to establish a neutral to slightly alkaline pH, for example within the range from 6 to 9.
The web or nonwoven could further be saturated with a waterglass solution, i.e., a sodium orthosilicate solution, in which case colloidal silica can be generated by treatment with a dilute mineral acid, for example hydrochloric acid. A further example is the treatment with an aqueous solution of borax (Na2B407 ~ 10 H20) with subsequent drying.

The impregnation of the web or nonwoven with the colloidal suspension of the oxide and/or hydroxide, or the impregnation with the solution of the precursor and the inducing of the oxide/hydroxide formation, can take place at any time during the production of the textile fabric. It is preferred that they take place before or simultaneously with the impregnation with the binder.
The impregnation of the web or nonwoven with the wetting agent can take place at any time during the production of the textile fabric of the invention. In general, it is advantageous to effect the impregnation with the wetting agent simultaneously with the binder impregnation. To this end, the wetting agent is simply added to the aqueous binder dispersion.
The Examples which follow illustrate the invention.
Examples 1 to 10 70/30 polyester/staple viscose rayon webs (1.7 dtex; fiber length 38 mm; 30 g/m2) from 35 to 50 cm in length and from 25 to 28 cm in width were carried in longitudinal direction through a 25~
strength binder liquor and over an aspirator on an endless PES
sieve belt forming part of an impregnating and aspirating range.
The binder dispersion used was Acronal DS 2350 X ~ (polyacrylate dispersion based on butyl acrylate and acrylonitrile). The belt speed was within the range from 1 to 2 m per min. The degree of aspiration was varied to set the wet add-on to about 160, which corresponds to a dry add-on of about 40~. The binder liquor included the additives reported in the table which follows (in $
of dry weight of binder). The impregnated webs were placed on the belt of a Mathis TH sieve belt dryer, secured against slippage and dried at 150~C for 2 min. The upper surface of each web was labeled, and the add-on level was determined by weighing.
The nonwovens thus obtained were subjected to a wetting test immediately thereafter and after being rinsed out five times. To rinse the nonwoven, it was immersed in a 5 1 bucket of tap water, squeezed (or wrung) out by hand about 15 times, then wrapped in a towel and wrung dry in the towel. This sequence was repeated 5 times.
Hydrophilicity was quantified by using the colored runoff test.
This test is carried out essentially as follows: The nonwoven is fixed at an incline and has a defined amount of colored water applied to it. Depending on the hydrophilicity of the nonwoven, the water will run off or pass into the nonwoven at a certain speed. Characteristic colored spots are obtained, which are, for example, circular for rapid penetration into the nonwoven or narrow and elongate for slow penetration and preferential runoff.
The assessments are rated on a scale.
To carry out the test, a specimen 21 x 5 cm in size is clamped into a frame which is at an angle of 30 degrees to the horizontal. The side which was the upper surface in the dryer faces downwards in this test. A pipette is used to apply 0.5 ml of test liquid from a height of 10 mm and at a distance of 30 mm from the upper edge of the web. The test liquid was made up of 2 g of Hostapal CV solution and 2.5 g of Lurantin Lightfast Turquoise Blue GL per 1 1 of completely ion-free water. After the test specimen had been hung up and has dried, the upper surface of the web is inspected and rated on a scale from 0 for no wetting (all the test liquid has run off) to 5 for total wetting.
The results are reported in the table which follows.
Table Colored runoff test Trial Mineral Emulsifier*5 before after No. additive rinsing rinses 2 - 3.0~ of sodium di(2-ethylhexyl)4 0-1 sulfosuccinate *1 3 5~ of - 0 0 silica *4 4 5~ of 3.0~ of sodium di(2-ethylhexyl)5 5 silica sulfosuccinate *1 *4 5 5~ of 3~ of dodecylbenzenesulfonate5 1-2 silica *4 6 5~ of 5~ of sodium alkylnaphthalene-0-1 0-1 silica sulfonic acid *z *4 7 5~ of 5$ of sodium alkylnaphthalene-0-1 0-1 silica sulfonic acid *2 *4 8 5~ of 3~ of ammonium polyacrylate 2 0-1 *3 silica *4 9 10$ of - 0 0 silica *4 10 10~ of 3.0$ of sodium di(2-ethylhexyl)5 5 silica sulfosuccinate *1 *4 *1 Lumiten IRA
*2 alkyl = diisobutyl (Nekal BX ~) *3 Pigmentverteiler [pigment dispersant] A

*4 Levasil 200 ~ (Bayer) *5 emulsifier was added in liquor It is clear from the table that only Examples 4 and IO provide a nonwoven which is still hydrophilic after 5 rinses. These Examples included a sulfosuccinic ester in conjunction with colloidal silica. Without silica (Example 2), even the use of the same emulsifier does not provide durable hydrophilicity. Other emulsifiers (Examples 5, 6) do not lead to the desired durable hydrophilicity. Nor do polymeric additives (Example 8) or higher amounts of silica lead to the desired properties in the absence of sulfosuccinic esters (Example 9).
Examples 11 to 18 Standard pulp webs (Whatman #4; 100 pulp) from 35 to 50 cm in length and from 25 to 28 cm in width were pad-mangled with a lOg strength binder liquor (Acronal DS 2350 X) and then dried in a Mathis tenter dryer with laydown gauze. The liquor included the additives reported in the table which follows. In Examples 13 and 14, the webs were initially pad-mangled with a 5~ strength A12(S04)3 solution and dried and only then saturated with binder in the pad-mangle and redried.
The nonwovens obtained were subjected to an absorbency test. To this end, a strip of nonwoven, measuring 70 x 30 mm, which had been rinsed and dried 5 times was suspended in the above-described test liquid at a depth of about 5 mm and the wicking height of the test liquid recorded after 30 s. In addition, the penetration rate in the nonwoven was measured. To this end, 0.1 ml of test liquid was placed on the front surface of nonwoven samples which had been rinsed and dried 5 times and the time recorded for the drop to penetrate completely into the nonwoven. The results are reported in the table which follows.

Table Trial Mineral Emulsifier *5 Wicking Penetration No. additive height (min) in mm 11 - - 0 none 12 - 3.0~ of sodium 9 6 di(2-ethylhexyl) sulfosuccinate *1 13 A1z03 from- 0 none A12(S04)3 14 A1203 from3.Og of sodium 11,5 1 A12(S04)3 di(2-ethylhexyl) sulfosuccinate *1 5~ of 3.0~ of sodium 11 immediate silica di(2-ethylhexyl) *4 15 sulfosuccinate *1 16 10~ of 3.0~ of sodium 7 29 Sipern.D di(2-ethylhexyl) 10*6 sulfosuccinate *1 17 10~ of 3.0~ of sodium 9 8 china di(2-ethylhexyl}

clay *7 sulfosuccinate *1 18 10~ of 3.Og of sodium 13 5 Gelb-s. di(2-ethylhexyl) kreide sulfosuccinate *1 *8 *4 Levasil 200 ~ (Bayer) *5 emulsifier was added in liquor *6 Sipernat D 10 = silica powder *~ aluminum silicate powder *$ CaC03 It is clear from the table that only the combination of mineral filler (aluminum oxide/hydroxide or silica; trials 14, 15) with sulfosuccinic ester leads to the desired durable hydrophilicity.
The components alone (trials 12, 13) are not sufficient. The examples featuring noncolloidal mineral additives (Examples 16, 17 and 18) demonstrate the criticality of the state of colloidally disperse subdivision.

Claims

1. A textile fabric comprising a web of fibers joined together by means of a polymeric binder, said fabric comprising an oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn in a state of colloidally disperse subdivision and a wetting agent selected from sulfosuccinates and sulfosuccinamates.

2. A textile fabric as claimed in claim 1, comprising 1 - 20% by weight of oxide and/or hydroxide, based on the dry weight of said polymeric binder.

3. A textile fabric as claimed in claim 1 or 2, comprising 1 - 20% by weight of wetting agent, based on the dry weight of said polymeric binder.

4. A textile fabric as claimed in any of claims 1 to 3, wherein said oxide and/or hydroxide is selected from the group consisting of silica, aluminum oxide, aluminum hydroxide and alumosilicates.

5. A textile fabric as claimed in any of the preceding claims, wherein said sulfosuccinate and/or sulfosuccinamate contains one or two alkyl groups of from 4 to 8 carbon atoms.

6. A textile fabric as claimed in any of the preceding claims, wherein said fibers are selected from the group consisting of polypropylene fibers, polyester fibers and cellulosic fibers.

7. A textile fabric as claimed in any of the preceding claims, wherein said binder comprises a polymer of monomers selected from the group consisting of C1-C4-alkyl (meth)acrylates, (meth)acrylic acid, (meth)acrylamide, N-methylol(meth)acrylamide, styrene, butadiene, (meth)acrylonitrile, vinyl C1-C6-alkanoates, vinyl chloride, ethylene and vinyl alcohol.

8. A process for producing a textile fabric by impregnating a web of fibers with a dispersion of a polymeric binder and drying and optionally curing the impregnated web, which comprises further impregnating said web with (i) a colloidal suspension of an oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn or a solution of a precursor of an oxide and/or hydroxide of A1, B, Si, Mg, Ti and/or Zn and inducing the formation of the oxide and/or hydroxide in a state of colloidally disperse subdivision and (ii) a wetting agent selected from sulfosuccinates and sulfosuccinamates.

9. A process as claimed in claim 8, wherein said colloidal suspension of said oxide and/or hydroxide is present in said dispersion of said polymeric binder.

10. A process as claimed in claim 9, wherein said colloidal suspension is a suspension of colloidal silica.

11. A process as claimed in claim 8, wherein said precursor of an oxide and/or hydroxide is a solution comprising Al3+ ions.

12. A process as claimed in claim 11, wherein said inducing of said formation of said oxide and/or hydroxide is effected simultaneously with said impregnating with said dispersion of said polymeric binder.