Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-01-15
2004-06-22
Seldisck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S009000, C524S013000, C524S015000, C524S016000, C524S035000
Reexamination Certificate
active
06753361
ABSTRACT:
The present invention relates to the use of compositions which comprise reaction products of low molecular mass dicarboxylic or tricarboxylic acids with ammonia to produce moldings from finely divided materials.
The production of moldings from finely divided materials, such as fiberboard or chipboard panels, etc., and the production of sheetlike structures from fiber materials, examples being fiber webs and fiber mats, is frequently carried out using a polymeric binder. To increase the strength, especially the wet strength and thermal stability, it is common to use binders which comprise crosslinkers that give off formaldehyde. Binders based on phenol-formaldehyde resins are known, for example, from U.S. Pat. No. 4,612,224. WO 94/20661 describes crosslinkable dispersion powders and their use as binders for fibers, comprising N-methylolamide groups as crosslinking components. On crosslinking, these groups give off formaldehyde.
Emissions of formaldehyde as a result of the binder are, however, problematic not least for reasons of occupational hygiene. Numerous alternatives have already been proposed in order to avoid formaldehyde emissions. For instance, U.S. Pat. No. 4,076,917 discloses binders which comprise carboxylic acid or carboxylic anhydride polymers and &bgr;-hydroxyalkylamides as crosslinkers. A disadvantage is the complicated preparation of the &bgr;-hydroxyalkylamides. Similar binders are known from EP-A 583 086.
EP-A 445 578 discloses boards made from finely divided materials such as glass fibers, whose binder comprises a composition comprising high molecular mass polycarboxylic acids and polyhydric alcohols, alkanolamines and/or polyfunctional amines. The water resistance of the boards obtained, is not satisfactory.
WO 99/09100 describes the use of heat-curable aqueous compositions which comprise a polymer having a low acid-group fraction, a polymer rich in acid groups, and at least one alkanolamine having two hydroxyl groups as binders for moldings from finely divided materials.
WO 99/02591 describes heat-curable compositions comprising a surface-active amine and a polymer with a low acid group fraction, prepared in the presence of a carboxyl-rich polymer, and their use as binders for moldings from finely divided materials.
The formaldehyde-free binder systems of the prior art are generally polymer systems. These systems generally have a high processing viscosity, which in connection with the production of moldings from finely divided materials often hinders uniform incorporation of the binders into the substrate to be bound and, in the course of the shaping operation, leads to inhomogeneities and thus to a relatively low mechanical strength in the molding. Moreover, these binder systems are comparatively costly, since the polymer component generally requires an additional preparation step.
WO 94/15993 discloses the preparation of polymers of aspartic acid by thermal condensation of monoamides of fumaric acid or maleic acid or of ammonium salts of the monoamides of these acids. From WO 95/02007 it is known that the monoamides required to prepare the aspartic acid polymers, and their ammonium salts, may be prepared in situ by reacting the acid anhydrides with a component that supplies ammonia.
It is an object of the present invention to provide a binder system for finely divided materials which on processing does not lead to formaldehyde emissions, which is favorably priced and with which moldings or consolidated sheetlike structures may be produced from fiber materials.
We have found that this object is achieved, surprisingly, by compositions which comprise a reaction product of a dicarboxylic or tricarboxylic acid or the anhydride thereof with ammonia and, if desired, a primary amine and/or a compound containing at least two hydroxyl groups, and/or, as a precursor of said reaction product, a mixture of said dicarboxylic or tricarboxylic acids or its anhydride with a substance which releases ammonia on heating.
The present invention accordingly provides a method for producing moldings from finely divided materials and for sheetlike structures of fiber materials, wherein the finely divided material is mixed or impregnated with a heat-curable composition and the resultant mixture is shaped at temperatures above 120° C. or an unconsolidated sheet-like structure of fiber materials is first treated with a heat-curable composition and then heated at temperatures above 120° C., wherein the heat-curable composition comprises:
at least one reaction product of
i. at least one polycarboxylic acid of the formula I:
in which
R is hydrogen or a CH
2
COOH group,
X is OH or NH
2
if Y is hydrogen,
Y is OH or NH
2
if X is hydrogen, or
X and Y together are a &pgr; bond, and/or an anhydride of the polycarboxylic acid I
ii. with ammonia and, if desired
iii. with primary amines and/or compounds containing at least two hydroxyl groups; and/or
a mixture of at least one polycarboxylic acid of the formula I and/or its anhydride and at least one substance which releases ammonia on heating and, if desired, primary amines and/or compounds containing at least two hydroxyl groups.
The invention further provides the sheetlike structures and moldings obtainable by these processes. The invention additionally provides heat-curable compositions which besides the aforementioned constituents comprise at least one further constituent selected from finely divided film forming polymers of ethylenically unsaturated monomers, compounds containing at least two hydroxyl groups, and water-soluble homopolymers and copolymers of acrylic acid and/or methacrylic acid.
In principle and in accordance with the invention, all conceivable reaction products of the polycarboxylic acid I or its anhydride with ammonia are suitable. These reaction products include the monoamides, bisamides and trisamides of the polycarboxylic acids I in which one (monoamides), two or all the carboxyl groups have been converted into carboxamide groups. They also include the monoammonium, bisammonium and trisammonium salts of the polycarboxylic acids I and also the monoammonium and bisammonium salts of monoamides and bisamides of I. Suitable polycarboxylic acids I are the unsaturated dicarboxylic and tricarboxylic acids: maleic acid, fumaric acid and aconitic acid; the hydroxyl-bearing dicarboxylic and tricarboxylic acids: malic acid and citric acid; and the amino-bearing dicarboxylic acid: aspartic acid. Suitable anhydrides are the intramolecular anhydrides of I, an example being maleic anhydride.
Without wishing to restrict the invention by one theory, it is assumed that, on heating, the compositions defined above condense to oligomers or polymers containing amide groups and/or cyclic imide groups in accordance with the schemes shown in EP-B 677 080 on pages 4 and 5. Said latter groups are probably responsible for the strength of the moldings and sheetlike structures. It is supposed that heating is accompanied first by polymerization of the monoamides of the ethylenically unsaturated polycarboxylic acids Ia (monoamide of the polycarboxylic acids I in which X and Y together are a &pgr; bond), in which the nitrogen of the amide group undergoes addition onto the ethylenically unsaturated double bond of Ia. The oligomer which is initially formed in this case, containing amide structural units II, reacts on prolonged exposure to heat and/or an increase in temperature, with intramolecular condensation, to form a polymer containing cyclic imide groups III. The intramolecular condensation generally begins at temperatures above 120° C., preferably above 130° C., and takes place to an increased extent at temperatures above 140° C., in particular above 150° C., and with particular preference above 160° C. In scheme 1, the reaction is illustrated on the example of the reaction of an ethylenically unsaturated dicarboxylic monoamide Ia.
The ammonium salts of the monoamides also polymerize in a similar way, as shown in Scheme 2 using the example of the ammonium salt of the monoamide Ia′. In Scheme 1 and Scheme 2, the variables n and k re
Gerst Matthias
Kroner Matthias
Reck Bernd
BASF - Aktiengesellschaft
Rajguru U. K.
Seldisck James J.
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