A non-woven material containing from 2% to 25% by dry weight of an alkali-soluble, water-resistant in neutral to weakly acidic solutions, binder for non-woven materials based on an aqueous vinyl acetate copolymer containing protective colloids and optionally emulsifiers and having the following monomer units PA1 (1) 50% to 70% of vinyl acetate PA1 (2) 20% to 35% of vinyl esters of higher alkanoic acids and/or higher alkyl esters of acrylic or methacrylic acids, and PA1 (3) 3% to 15% of ethylenically-unsaturated acids, said binder being applied to said non-woven material as an aqueous dispersion and subsequently dried.

BACKGROUND OF THE ART 
Binders for non-woven materials based on vinyl acetate copolymers, are 
known. Such binders, among others, increase the mechanical strength, the 
wet tear strength and the resistance to dry cleaning and impart a pleasant 
handle to the non-woven materials produced therewith. When punching 
sheet-like articles, particularly of circular form, from a continuous web 
of non-woven materials substantial amounts of scrap may be produced, 
which, because of the binder content, cannot be recycled to the non-woven 
material manufacturing process. To be able to do so, it would be necessary 
again to remove the binder from the non-woven material. 
Copolymers which contain carboxyl groups and are soluble in alkali are 
known. However, such polymers are so sensitive to water that their use as 
binders for the manufacture of non-woven materials having good wet tear 
strength is not possible. 
The use of alkali-soluble polymeric substances as textile glues (sizes) has 
been known for a substantial time. As a result of the use of water-jet 
looms when processing sized yarns, the additional need for sufficient 
water resistance of these alkali-soluble sizes arose. In German 
Offenlegungsschrift (DOS) No. 2,162,285, this object was achieved by 
using, as textile glues, poly-(vinyl acetate/dialkyl maleate/acrylic acid) 
sizes, dimethyl maleate and/or diethyl maleate being employed as the 
dialkyl maleate. It is known that such polymers meet the standards to 
which the water resistance of a yarn sized therewith has to conform when 
used for water-jet weaving, but they cannot be used as alkali-elutable 
binders for non-woven materials having good wet tear strength. 
OBJECTS OF THE INVENTION 
An object of the present invention is the development of a binder for 
non-woven materials which is removeable with alkalis and which gives the 
non-woven material a high wet tear strength. 
Another object of the present invention is the development of an 
alkali-soluble, water-resistant in neutral to weakly acidic solutions, 
binder for non-woven materials consisting essentially of an aqueous vinyl 
acetate copolymer having a solids content of from 10% to 60% by weight and 
the following range of monomeric units: 
(1) 50% to 70% by weight of the monomer units of vinyl acetate units, 
(2) 20% to 35% by weight of the monomer units of higher molecular weight 
ethylenically-unsaturated ester units selected from the group consisting 
of vinyl esters of alkanoic acids having from 8 to 18 carbon atoms, alkyl 
esters having from 4 to 18 carbon atoms in the alkyl of acrylic acid, 
alkyl esters having from 4 to 18 carbon atoms in the alkyl of methacrylic 
acid, and mixtures thereof, and 
(3) 3% to 15% by weight of the monomer units of ethylenically-unsaturated 
acid units selected from the group consisting of alkenoic acids having 3 
to 4 carbon atoms, alkenedioic acids having 4 carbon atoms, alkyl 
monoesters having 1 to 18 carbon atoms in the alkyl of alkenedioic acids 
having 4 carbon atoms, alkenyl monoesters having from 3 to 6 carbon atoms 
in the alkenyl of alkanedioic acids having 2 to 6 carbon atoms, and 
mixtures thereof, and containing from 0.5% to 10% by weight, based on the 
monomer units of protective colloids and from 0 to 6% by weight, based on 
the monomer units of emulsifiers. 
These and other objects of the invention will become more apparent as the 
description thereof proceeds. 
DESCRIPTION OF THE INVENTION 
The invention relates to binders for non-woven materials which are soluble 
in aqueous alkalis but are resistant to aqueous neutral or weakly acidic 
solutions, and are based on aqueous vinyl acetate copolymer dispersions 
with solids contents of between 10% and 60% by weight, characterized in 
that the polymer resin consists of 
50% to 70% by weight of vinyl acetate units, 
20% to 35% by weight of units of alkanoic acid vinyl esters with 8 to 18 
carbon atoms in the alkyl group of the acid and/or acrylic or methacrylic 
acid alkyl esters with 4 to 18 carbon atoms in the alkyl group, and 
3% to 15% by weight of ethylenically-unsaturated monocarboxylic acids 
and/or dicarboxylic acids with 3 to 4 carbon atoms or monoesters of the 
latter with alkyl groups having between 1 and 18 carbon atoms and/or 
monoesters of saturated dicarboxylic acids with 2 to 6 carbon atoms and 
unsaturated alcohols with 3 to 6 carbon atoms, and contains 
0.5% to 10% by weight of protective colloids and up to 
6% by weight of emulsifiers. 
More particularly, the present invention relates to an alkali-soluble, 
water-resistant in neutral to weakly acidic solutions, binder for 
non-woven materials consisting essentially of an aqueous vinyl acetate 
copolymer having a solids content of from 10% to 60% by weight and the 
following range of monomeric units: 
(1) 50% to 70% by weight of the monomer units of vinyl acetate units, 
(2) 20% to 35% by weight of the monomer units of higher molecular weight 
ethylenically-unsaturated ester units selected from the group consisting 
of vinyl esters of alkanoic acids having from 8 to 18 carbon atoms, alkyl 
esters having from 4 to 18 carbon atoms in the alkyl of acrylic acid, 
alkyl esters having from 4 to 18 carbon atoms in the alkyl of methacrylic 
acid, and mixtures thereof, and 
(3) 3% to 15% by weight of the monomer units of ethylenically-unsaturated 
acid units selected from the group consisting of alkenoic acids having 3 
to 4 carbon atoms, alkenedioic acids having 4 carbon atoms, alkyl 
monoesters having from 1 to 18 carbon atoms in the alkyl of alkenedioic 
acids having 4 carbon atoms, alkenyl monoesters having from 3 to 6 carbon 
atoms in the alkenyl of alkenoic acids having 2 to 6 carbon atoms, and 
mixtures thereof, and containing from 0.5% to 10% by weight, based on the 
monomer units, of protective colloids and from 0 to 6% by weight, based on 
the monomer units, of emulsifiers. 
The use of the binders of the invention makes it possible to again dissolve 
the synthetic resin binder out of the scrap after the punching process, 
and thus to find renewed use for the punching scrap by recycling to the 
production of the non-woven materials. The binders are particularly 
effective for application to cellulosic non-woven materials. 
The binders exhibit good properties if units of isononanoic acid vinyl 
ester and/or n-butyl acrylate are employed as the units of alkanoic acid 
vinyl esters and acrylic or methacrylic acid alkyl esters respectively. 
The use of crotonic acid as the ethylenically unsaturated monocarboxylic 
acid and of hydroxyethylcellulose and/or polyvinyl alcohol as the 
protective colloids has proved particularly advantageous. 
The binders can be used for the manufacture of non-woven materials. A 
particular embodiment is the manufacture of non-woven filters using the 
binders according to the invention, particular interest residing in the 
manufacture of cellulose non-woven filters. The binders are employed in 
amounts of from 2% to 25% by dry weight of the non-woven material. 
The binders according to the invention are distinguished by the fact that 
on the one hand they are not dissolved by aqueous neutral or weakly acid 
solutions but on the other hand can be eluted or washed out by aqueous 
alkaline solutions, such as, for example, sodium carbonate solution. In 
addition, the non-woven filters treated with the binders according to the 
invention are distinguished by good wet tear strength. 
The aqueous polymer resin dispersions are in general manufactured in a 
stirred polymerization autoclave with heating and cooling equipment. The 
requisite amount of protective colloid and emulsifier, if any, is first 
introduced as a solution in the aqueous phase. After flushing with 
nitrogen, a part of the monomer mixture and an equivalent part of the 
peroxide catalyst are added to the initial charge and the mixture is 
warmed to 45.degree. to 65.degree. C. The metering-in of the reducing 
component of the redox catalyst in dilute aqueous solution is then 
started. The metering-in of the reducing component is carried out in such 
a way that it only terminates after the end of the metering-in of the 
monomer mixture. The metering-in of the monomer mixture is started when 
the internal temperature of the polymerization batch has risen to at least 
75.degree. C. Preferably, the polymerization is carried out at 
temperatures between 75.degree. and 85.degree. C. After completion of the 
metering-in of all reactants the polymerization is continued for 2 hours 
at 90.degree. C. and the mixture is then cooled. Grit-free and 
coagulate-free dispersions with solids contents of up to 60% by weight are 
obtained Viscosities of 300 to 500 mPas (Epprecht rheometer at 20.degree. 
C., measuring cup C, stage III) are preferred. 
Suitable protective colloids for use in the polymerization are partially 
saponified polyvinyl acetates having a degree of hydrolysis of between 74 
and 97 mol %, water-soluble cellulose derivatives, such as, for example, 
carboxymethylcellulose, carboxypropylcellulose, hydroxypropylcellulose, 
polyvinylpyrrolidone, polyacrylic acids, polyacrylamide, water-soluble 
polyacrylic acid-and polyacrylamide copolymers, methylcellulose, gelatine, 
casein and water-soluble starch products. Preferably, partially saponified 
polyvinyl acetate having a degree of hydrolysis of 81 to 94 mol %, and/or 
water-soluble hydroxyethylcellulose, are employed. The protective colloids 
are added to the polymerization batch in amounts of 0.5% to 10% by weight, 
based on the weight of the monomers. 
Suitable emulsifiers are alkylarylsulfonates, alkylsulfates, sulfates of 
hydroxyalkanols, sulfonated fatty acids, sulfates and phosphates of alkyl- 
and alkylarylpolyethoxyalkanols, addition products of 5 to 50 mols of 
ethylene oxide to straight-chain and branched-chain alkyl alcohols with 6 
to 22 carbon atoms or to alkylphenols, and block copolymers of ethylene 
oxide and propylene oxide. Alkylsulfonates, sulfosuccinic acid monoesters 
and diesters, isotridecyl alcohol polyethyleneglycol ether and nonylphenol 
polyethyleneglycol ether are particularly suitable. The emulsifiers, if 
employed, are added to the polymerization batch in amounts of up to 6% by 
weight. 
Suitable catalysts are water-soluble redox catalyst systems with oxidizing 
peroxide components such as inorganic peroxides, for example hydrogen 
peroxide or potassium peroxy-disulfate, or organic peroxides such as 
tertiary butyl hydroperoxide, and with inorganic sulfur compounds in which 
sulfur is in an oxidation state of up to 6, such as, for example, sodium 
formaldehyde-sulfoxylate, as the reducing component. A further suitable 
reducing component is a palladium sol together with hydrogen, in the 
presence of traces of heavy metals. The catalysts are employed in amounts 
of between 0.1% to 1% by weight of the total dispersion. 
The monomers which are copolymerized are vinyl acetate as the basic 
monomer, used in amounts of 50% to 70% by weight of the monomers and 20% 
to 35% by weight of the monomers of units of alkanoic acid vinyl esters 
with 8 to 18 carbon atoms in the alkyl group of the alkanoic acid, such 
as, for example, i-nonanoic acid vinyl ester, vinyl laurate, 
2-ethylhexanoic acid vinyl ester, Versatic.RTM. acid vinyl ester (Versatic 
acids are mixtures of secondary and tertiary alkanoic acids having various 
chain lengths. Versatic acid (9 11) has from 9 to 11 carbon atoms) and/or 
acrylicor methacrylic acid alkyl esters with 4 to 18 carbon atoms in the 
alkyl group, such as, for example, n-butyl acrylate and 2-ethylhexyl 
acrylate. Preferably i-nonanoic acid vinyl ester and/or n-butyl acrylate 
are employed. When mixtures of both types of esters are employed, the 
ratio of vinyl esters to acrylic esters is from 1:100 to 100:1. In 
addition, 3% to 15% by weight of the monomers of ethylenically-unsaturated 
monocarboxylic acid and/or dicarboxylic acids with 3 to 4 carbon atoms, 
such as alkenoic acids for example, crotonic acid, acrylic acid, or 
metacrylic acid, alkenedioic acids, for example, fumaric acid or maleic 
acid, or monoesters of the alkene-dicarboxylic acids with alkyl groups 
having between 1 and 18 carbon atoms, and/or monoesters of 
alkane-dicarboxylic acids with 2 to 6 carbon atoms and unsaturated 
alcohols (alkenols) with 3 to 6 carbon atoms are employed, such as, for 
example, adipic acid monoallyl ester or succinic acid monoallyl ester. 
Known regulators, for example aldehydes, organic halogen compounds, 
mercaptans or nitro compounds may also be present during the 
polymerization, in order to regulate the molecular weight. 
To regulate the pH value during the polymerization reaction, customary 
buffer systems such as sodium bicarbonate, sodium acetate, trisodium 
citrate and secondary and tertiary phosphates, such as, for example, 
disodium hydrogen phosphate or trisodium phosphate, pyrophosphates and 
polyphosphates, such as tetrasodium pyrophosphate, sodium tripolyphosphate 
and sodium hexametaphosphate, may be added. 
The elutability and wet tear strength were tested using filter paper (No. 
850/60 from Machery and Nagel), weighing about 68 gm/m.sup.2, by 
impregnating the filter paper for one minute with a dispersion having a 
solids content of 10% to 15% by weight, then squeezing off on a padder 
(100 N/cm linear pressure, 1 m/minute running speed, at room temperature), 
drying for one and a half hours at room temperature and then drying for 
half an hour at 100.degree. C. The amount of binder taken up was 
determined by difference from weighing under standard climatic conditions. 
To test the elutability, 2 to 2.5 gm of filter paper contaning binder were 
boiled in 1 liter of a 2% strength aqueous sodium carbonate solution 
(Na.sub.2 CO.sub.3.10H.sub.2 O) for 30 minutes, then rinsed twice for 2 
minutes with hot water at 60.degree. to 70.degree. C. and once for 5 
minutes with cold water, and thereafter dried for half an hour at 
100.degree. C. The dried samples were weighed under standard climatic 
conditions. 
The wet tear strength was tested in accordance with DIN 53,857. The maximum 
tensile force N was determined from 5 values in the lengthwise direction 
and 5 values in the crosswise direction. The length between clamps was 100 
mm, and the width of the sample 15 mm. 
The low water solubility of the binder in neutral or weakly acid solutions 
can be determined in the same way by the difference between weighings 
under defined conditions before and after the treatment with neutral or 
weakly acid aqueous solutions. 
When using the binders according to the invention in non-woven materials, 
the wet tear strength showed excellent values both in the lengthwise and 
in the crosswise direction. The solubility in neutral or weakly acid 
solutions is so low that the non-woven materials containing the binders 
can be employed for foodstuffs purposes. The elutability of the binder 
with alkaline aqueous solutions permits regenerating the cellulose from 
the punching scrap. 
The following examples are illustrative of the practice of the invention 
without being limitative in any respect.

EXAMPLE 1 
38.3 parts by weight of water, 3 parts by weight of a substantially 
saponified polyvinyl alcohol having a degree of hydrolysis of 87.5 mol %, 
0.04 parts by weight of a secondary alkylsulfonate with 12 to 15 carbon 
atoms in the alkyl group and 0.54 part by weight of an isotridecyl alcohol 
etherified with 15 mols of ethylene oxide were introduced into a reactor 
equipped with a reflux condenser, stirrer, metering devices, nitrogen 
inlet and heatable and coolable jacket. After flushing with nitrogen, 21% 
by weight of the monomer solution, which consists of 29.7 parts by weight 
of vinyl acetate, 12 parts by weight of isononanoic acid vinyl ester, 3.8 
parts by weight of n-butyl acrylate, 2.4 parts by weight of crotonic acid 
and 0.1 part by weight of t-butyl hydroperoxide, were introduced into the 
receiver and the reaction mixture was warmed. The metering of the reducing 
component, which is composed of 10 parts by weight of water, 0.06 part by 
weight of sodium formaldehyde-sulfoxylate and 0.06 part by weight of 
sodium bicarbonate, was started at a temperature of the reaction mixture 
of 55.degree. C. The metering of the reducing component was carried out in 
such a way that it was completed one hour after the monomer addition was 
completed. 
The metering-in of the monomer solution was started at an internal 
temperature of 80.degree. C. The polymerization was carried out at a 
temperature of the reaction mixture of 78.degree. to 82.degree. C. When 
everything had been metered in, polymerization was continued for 2 hours 
at 90.degree. C. and the mixture was then cooled. A stable, grit-free and 
coagulate-free dispersion was obtained, which had a solids content of 50% 
by weight and a viscosity of 400 mPas (Epprecht rheometer at 20.degree. 
C., measuring cup C, stage III). 
EXAMPLE 2 
A dispersion was prepared analogously to Example 1 with a polymer resin 
consisting of 59.1% by weight of vinyl acetate units, 31.4% by weight of 
n-butyl acrylate units and 4.8% by weight of crotonic acid units. The 
protective colloid employed here was 1.9% by weight of 
hydroxyethylcellulose, while the emulsifier employed was an 
alkylphenol/ethylene oxide addition product with 23 ethylene oxide units 
per alkylphenol, the alkylphenol containing 9 carbon atoms in the alkyl. 
EXAMPLE 3 
(Comparative Example 1) 
In order to demonstrate the superiority of the binders according to the 
invention over products which do not contain any units of alkanoic acid 
vinyl esters with 8 to 18 carbon atoms in the alkyl radical of the 
alkanoic acid and/or acrylic or methacrylic acid alkyl esters with 4 to 18 
carbon atoms in the alkyl radical, a dispersion was prepared with a 
polymer resin consisting of 92.3% by weight of vinyl acetate units and 
3.0% by weight of crotonic acid units. The protective colloid/emulsifier 
system had the same composition as in Example 2. 
EXAMPLE 4 
(Comparative Example 2) 
In order to demonstrate the superiority of the binders according to the 
invention over the dispersions disclosed in German Offenlegungsschrift No. 
2,162,285, the latex described in Example 1 of German Offenlegungsschrift 
No. 2,162,285, page 8, was prepared. 
The table which follows summarizes the values determined for each of the 
dispersions, these values resulting from the investigations described 
above. 
TABLE 
__________________________________________________________________________ 
Elutability and wet tear strength of filter paper treated with the 
dispersions of Examples 1-4 
Elutability 
Dispersion 
Amount of 
Loss of 
Amount of 
Wet tear strength 
according 
binder 
binder 
binder Maximum tensile force N 
to Example 
applied 
applied 
applied after 1 minute's 
after 30 minutes' 
No. (%) (%) (%) Dry 
storage in water 
storage in water 
__________________________________________________________________________ 
1 11.7 97.4 
10.0 34.0 
7.55 5.72 
2 10.3 98.4 
10.3 33.6 
7.63 6.53 
3 11.6 97.1 
10.5 31.0 
4.21 3.23 
4 9.9 89.2 
10.5 31.4 
3.21 2.53 
Original 
filter 
paper -- 1.6* 
-- 12.5 
2.14 1.99 
__________________________________________________________________________ 
*Loss in weight 
The preceding specific embodiments are illustrative of the practice of the 
invention. It is to be understood however, that other expedients known to 
those skilled in the art or disclosed herein, may be employed without 
departing from the spirit of the invention or the scope of the appended 
claims.