Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles
Patent
1998-08-21
2000-08-08
Cole, Elizabeth M.
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
264121, 264257, 156296, 1563071, 156332, 4282924, B32B 2102
Patent
active
060997737
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to the use of formaldehyde-free binders for producing shaped articles and boards from finely divided natural materials, for example wood chips, wood fibers, sisal fibers, jute fibres, flax fibers or cork chips.
Shaped articles, for example boards, are frequently produced from such renewable raw materials using formaldehyde condensation resins as binders. The disadvantage of these binders is the emission of formaldehyde not only during the manufacture of the boards and shaped articles but also during their later use.
EP 445 578 discloses shaped articles composed of finely divided materials (including wood fibers) in which condensation products of a mixture comprising at least one high molecular weight polycarboxylic acid and at least one polyfunctional amine, alkanolamine or alcohol are used as binders. The disclosed high molecular weight polycarboxylic acids are polyacrylic acid poly(methyl methacrylate-co-n-butyl acrylate-co-methacrylic acid) and poly(methyl methacrylate-co-methacrylic acid). The polyhydric alcohols and alkanolamines used are 2-hydroxymethyl-1,4-butanediol, trimethylolpropane, glycerol, poly(methyl methacrylate-co-hydroxypropyl acrylate), diethanolamine and triethanolamine. Maleic acid is mentioned as a possible comonomer for preparing the high molecular weight polycarboxylic acids, but the use of maleic acid copolymers is not more particularly described. Preference is given to the use of .alpha.,.beta.-unsaturated carboxylic acids. The use of triethanolamine as crosslinker is mentioned in an Example, but only in combination with an aqueous dispersion of a copolymer of methyl methacrylate and methacrylic acid obtained in an emulsion polymerization.
However, the water resistance of the shaped wood-fiber articles described in EP 445 578 leaves something to be desired.
EP 583 086 discloses formaldehyde-free aqueous binders for producing mechanically stable, heat-resistant glass fiber webs. The binders comprise polycarboxylic acids, polyols and a phosphorus-containing reaction accelerant. There is no mention of the binder being used for binding finely divided natural materials.
EP 651 088 describes the bonding of cellulose substrates, especially fiber webs, with aqueous compositions of polycarboxylic acids, polyols and phosphorus-containing accelerants. The presence of phosphorus-containing compounds, for example sodium hypophosphite monohydrate, as reaction accelerant is mandatory in these binders.
The production of shaped articles, especially chipboard, is mentioned as a possible use; however, the use of maleic acid or maleic anhydride copolymers together with alkanolamines for this purpose is not disclosed.
It is an object of the present invention to provide highly reactive formaldehyde-free binders for producing boards and shaped articles from finely divided natural materials. The shaped articles and boards shall have good mechanical properties, especially low water swellability.
We have found that this object is achieved by the use of a formaldehyde-free aqueous binder 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 produce shaped articles.
The present invention also provides shaped articles obtainable by the foregoing use.
The aqueous binder of this invention includes a polymer A) containing from 5 to 100% by weight, preferably from 5 to 50% by weight, particularly preferably from 10 to 40% by weight, of units derived from an ethylenically unsaturated acid anhydride or an ethylenically unsaturated dicarboxylic acid whose carboxyl groups are capable of forming an anhydride group (hereinafter referred to as monomer a)).
The acid anhydrides are preferably dicarboxylic anhydrides. Suitable ethylenically unsaturated dicarboxylic acids are generally those having carboxylic acid groups on vicinal carbons. The carboxylic acid groups can also be present in the form of their salts.
Preferred monomers a) are maleic aci
Beckerle Wilhelm Friedrich
Hummerich Rainer
Kistenmacher Axel
Reck Bernd
Rupaner Robert
BASF - Aktiengesellschaft
Cole Elizabeth M.
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