Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
1999-02-05
2001-01-16
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S392000, C427S393400
Reexamination Certificate
active
06174568
ABSTRACT:
TECHNICAL FIELD
The invention relates to solvent-resistant textile binders, to processes for the preparation thereof and to processes for preparing solvent-resistant fiber structures using the solvent-resistant textile binders.
BACKGROUND ART
The use of aqueous copolymer dispersions as binders for bonding and coating fiber structures such as woven fabrics, nonwovens and waddings of textile fiber or textile yarns is known. Copolymer dispersions of (meth)acrylate or vinyl ester copolymers which comprise self-crosslinking comonomer units with N-methylol or N-methylol ether functions to improve their strength are often used here. Up to 10% by weight of N-methylol(meth)acrylamide (NMA or NMMA) are usually copolymerized. Disadvantages of these binders are the release of formaldehyde due to cleavage of the N-methylol function and the low resistance to solvents of the materials bonded or coated with them. Improvement of the resistance to solvents by incorporation of precrosslinking, poly-ethylenically unsaturated comonomer units is known. However, this measure often leads to problems in the preparation of the copolymer dispersions.
Thermally self-crosslinking copolymers which comprise 2 to 10% by weight of N-methylol(meth)acrylamide or the N-methylol ether thereof are known from DE-A 2512589 (U.S. Pat. No. 4,044,197). The copolymer dispersions are prepared in the presence of any desired anionic, cationic or nonionic emulsifiers, anionic and nonionic emulsifiers being preferred. A disadvantage is that, although in the case of the N-methylolacrylamide-containing copolymers used therein the heat-treated copolymer films show a good resistance to solvents, the nonwovens bonded with them do not.
EP-B 205862 relates to textile binders based on vinyl acetate/ethylene copolymers which comprise 1 to 5% by weight of N-methylol(meth)acrylamide units or ethers thereof. To improve the wet strength if a copolymer binder of low NMA content is used, the additional use of melamine-formaldehyde resins is proposed. The polymerization is carried out in the presence of anionic or nonionic emulsifiers.
The doctrine of EP-A 261378 is to improve the heat stability of fiber mats bonded with N-methylol functional styrene/acrylate copolymers by employing as binders those copolymers in which the N-methylol functions are completely or partly etherified. The polymerization can take place in the presence of any desired nonionic or anionic emulsifiers.
WO-A 92/08835 describes textile binders based on vinyl acetate/ethylene copolymer emulsions which comprise exclusively N-(n-butoxymethyl)acrylamide units instead of N-methylol(meth)acrylamide units to reduce the release of formaldehyde. For the preparation according to the emulsion polymerization process, the usual ionic or nonionic emulsifiers can be used.
EP-A 86889 (AU-A 8310718) relates to a process for the preparation of a textile coating composition which shows no white swelling and no white fracture under the action of water. The coating composition comprises an aqueous copolymer emulsion which is obtained by emulsion copolymerization of (meth)acrylates with N-methylol(meth)acrylamide, the N-methylol(meth)acrylamides being etherified to the extent of at least 20 mol % with an alcohol and the emulsion polymerization being carried out in the presence of a mixture of fatty alcohol having 10 to 20 C atoms and fatty alcohol adducts of alkylene oxides or alkylphenols.
In DE-A 4432945 (WO-A 96/08597) it is proposed, for improving the solvent resistance, to employ textile binders with a mixture of N-methylol-functional comonomer units and N-methylol ether-functional comonomer units. By this means a marked improvement in solvent resistance is obtained, although this is still not satisfactory for certain applications, especially in the case of soft textile binders—for example, ethylene-vinyl acetate copolymers of high ethylene content.
SUMMARY OF THE INVENTION
The invention was based on the object of providing a binder based on aqueous copolymer dispersions or copolymer powders having N-methylol-functional and N-methylol ether-functional comonomer units, with which a further increase in the solvent resistance, in addition to a high dry and wet strength, is achieved, especially also in soft textile binders.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention relates to a solvent-resistant textile binder in the form of an aqueous copolymer dispersion or of a copolymer powder of copolymers having a T
g
of −60° C. to +60° C., obtainable by means of free-radical emulsion polymerization, in the presence of emulsifier(s) and optionally after drying of the aqueous copolymer dispersion thereby obtained, of
a) one or more monomers from the group consisting of vinyl esters of unbranched or branched carboxylic acids having 1 to 12 C atoms, esters of acrylic acid and methacrylic acid with unbranched or branched alcohols having 1 to 12 C atoms, vinylaromatics, vinyl halides and alpha-olefins and
b) 0.01 to 10% by weight, based on the total weight of the copolymer, of one or more monomers b1) selected from the group consisting of the N-(alkoxymethyl)acrylamides and N-(alkoxy-methyl)methacrylamides with a C
1
- to C
6
-alkyl radical or
one or more monomers b2) from the group N-methylolacrylamide and N-methylolmethacrylamide or
mixtures of N-(alkoxymethyl) compounds b1) and N-methylol compounds b2),
characterized in that as emulsifier(s)
from 0.01 to 10% by weight, based on the overall weight of the copolymer, of one or more emulsifiers from the group of the diesters of sulfosuccinic acid with linear, unbranched or branched, or cycloaliphatic alcohols are employed or are added to the aqueous copolymer dispersion after the end of the emulsion polymerization.
Preferred N-(alkoxymethyl)(meth)acrylamides are N-(isobutoxymethyl)acrylamide (IBMA), N-(isobutoxymethyl)methacrylamide (IBMMA), N-(n-butoxymethyl)acrylamide (NBMA) and N-(n-butoxymethyl)methacrylamide (NBMMA).
The copolymers preferably comprise 0.5 to 4.0% by weight, based on the total weight of the copolymer, of monomer units b1) selected from N-(alkoxymethyl)acrylamides or N-(alkoxymethyl)methacrylamides with a C
1
- to C
6
-alkyl radical or of monomer units b2) N-methylolacrylamide (NMA) or N-methylol-methacrylamide (NMMA), or of mixtures of monomer units b1) and monomer units b2). Copolymers which comprise, in the weight contents mentioned, mixtures of the N-(alkoxymethyl)(meth)acrylamides with N-methylolacrylamide or N-methylolmethacrylamide in a weight ratio of N-methylol compound to N-(alkoxymethyl) compound of 10:1 to 1:5 are particularly preferred. Copolymers which comprise 0.5 to 3.0% by weight, based on the total weight of the copolymer, of a mixture of NMA and IBMA (IBMMA) in a weight ratio of NMA/IBMA (IBMMA) of 6:1 to 1:3, in particular 6:1 to 1:1, are most preferred.
Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of alpha-branched monocarboxylic acids having 9 or 10 C atoms, for example VeoVa9
R
or VeoVa10
R
. Vinyl acetate is particularly preferred.
Preferred methacrylic acid esters or acrylic acid esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate and 2-ethylhexyl acrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred.
The vinyl ester copolymers can comprise, if appropriate, 1.0 to 50% by weight, based on the total weight of the comonomer phase, of alpha-olefins, such as ethylene or propylene, and/or vinylaromatics, such as styrene, and/or vinyl halides, such as vinyl chloride, and/or acrylic acid esters or methacrylic acid esters of alcohols having 1 to 12 C atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate and 2-ethylhexyl acrylate, and/or ethylenically unsaturated dicarboxylic acid esters or d
Koegler Gerhard
Kohlhammer Klaus
Lumpp Andreas
Rockinger Monika
Brooks & Kushman P.C.
Cameron Erma
Wacker-Chemie GmbH
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