Formaldehyde-free aqueous binders

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...

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524249, 524494, C08K 300

Patent

active

06071994&

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The present invention relates to formaldehyde-free aqueous binders comprising of units derived from an ethylenically unsaturated acid anhydride or from an ethylenically unsaturated dicarboxylic acid whose carboxyl groups can form an anhydride group, and including less than 1.5% by weight, based on the sum of A)+B), of a phosphorus-containing reaction accelerant.
The present invention further relates to the use of the binders as coatings, impregnants or binders for fiber webs.
The consolidation of sheetlike fibrous structures, or fiber webs, is effected for example purely mechanically by needling or water jet consolidation of a wet- or air-laid web or by chemical consolidation of the webs with a polymeric binder. The binder is generally applied by impregnating, spraying or coating. To enhance the wet strength and heat resistance of the webs, use is frequently made of binders comprising formaldehyde-eliminating crosslinkers. Alternatives to existing binders are sought to avoid formaldehyde emissions.
U.S. Pat. No. 4,076,917 discloses binders comprising carboxylic acid or anhydride polymers and .beta.-hydroxyalkylamides as crosslinkers. The molar ratio of carboxyl groups to hydroxyl groups is preferably 1:1. The disadvantage is the relatively complicated synthesis of the B-hydroxyalkylamides. An appropriate binder is known from U.S. Pat. No. 5,340,868.
EP 445 578 discloses rigid sheets of finely divided materials, for example glass fibers, in which mixtures of high molecular weight polycarboxylic acids and polyhydric alcohols, alkanolamines or polyacid amines act as binders. The disclosed high molecular weight polycarboxylic acids are polyacrylic acid, copolymers of methyl methacrylate
-butyl acrylate/methacrylic acid and of methyl methacrylate/methacrylic acid. The polyhydric alcohols and alkanolamines disclosed are 2-hydroxymethyl-1,4-butanediol, trimethylolpropane, glycerol, poly(methylmethacrylate-co-hydroxypropyl acrylate), diethanolamine and triethanolamine. Maleic acid is mentioned as a possible comonomer for preparing the high molecular weight polycarboxylic acids.
EP 583 086 discloses formaldehyde-free aqueous binders for producing fiber webs, especially glass fiber webs. These binders require a phosphorus-containing reaction accelerant to provide adequate glass fiber web strengths. The binders comprise a polycarboxylic acid having at least 2 carboxyl groups and optionally also anhydride groups. Polyacrylic acid is used in particular, but copolymers of acrylic acid with maleic anhydride are also disclosed. The binder further comprises a polyol, for example glycerol, bis[N,N-di(.beta.-hydroxyethyl)adipamide [sic], pentaerythritol, diethylene glycol, ethylene glycol, gluconic acid, .beta.-D-lactose, sucrose, polyvinyl alcohol, diisopropanolamine, 2-(2-aminoethylamino)ethanol, triethanolamine, tris(hydroxymethylamino)methane and diethanolamine. The phosphorus-containing reaction accelerant is stated to be omittable only if a highly reactive polyol is used. .beta.-Hydroxyalkylamides are disclosed as highly reactive polyols.
EP-A 651 088 describes formaldehyde-free aqueous binders for cellulosic substrates. The presence of phosphorus-containing reaction accelerant is mandatory in these binders.
DE 4 408 688 discloses formaldehyde-free binders for fibrous sheet materials, comprising a mixture of polycarboxylic acid and aromatic or cycloaliphatic polyols. Despite a very high drying temperature (230.degree. C.), these binders provide only low wet breaking strength on glass fiber webs.
In addition to existing formaldehyde-free binders, it is always desirable to have further formaldehyde-free binders available as alternatives. For economic reasons it is desirable to consolidate sheetlike fibrous structures at low temperatures within a short time while obtaining good mechanical properties. Suitable binders are safe and do not emit toxic or environmentally harmful reaction products in use. Furthermore, suitable binders ideally consist of readily obtainable, inexpensive components.
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