Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1995-02-10
2001-04-03
Sergent, Rabon (Department: 1711)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S331700, C525S123000, C525S440030, C528S059000, C528S060000, C528S065000, C528S074500, C528S075000, C528S080000
Reexamination Certificate
active
06210523
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to new isocyanate-based compositions useful as binders for the production of composite materials.
Composite materials (also called compression-molded materials) such as chipboards, composite boards or other molded bodies are produced by hot molding an inorganic or organic raw material such as a mass of wood chips, wood fibers, or other lignocellulose-containing material, with a binder such as an aqueous dispersion of a urea/formaldehyde resin or a phenol/formaldehyde resin. Isocyanates or isocyanate solutions may be used instead of formaldehyde resins as binders for hardboards (See, e.g., German Auslegeschrift 1,271,984; and German Offenlegungschriften 1,492,507; 1,653,177; and 2,109,686). The use of polyisocyanates as binders improves the stability and moisture characteristics of the composite materials and increases their mechanical strength. Polyisocyanates also have far-reaching process engineering advantages when used as binders. These advantages are discussed in German Offenlegungschrift 2,109,688.
The large-scale, industrial production of composite materials bonded with polyisocyanates (particularly lignocellulose-containing materials such as chipboards, fiberboards and plywood) is, however, impeded by the high adhesiveness of the polyisocyanate. This adhesiveness causes the molded composite to adhere strongly to all metal parts (especially pressing plates made of steel or aluminum) after the hot molding and makes mold release difficult.
Previously proposed methods for solving this release problem each have their disadvantages. Some of those disadvantages are greater than others. Release agents developed especially for use with isocyanates frequently have a good release action but they are unreliable in large-scale application, uneconomical and can also cause defective gluing or coating difficulties in the further processing of boards made with the release agent
German Offenlegungschrift 1,653,178 discloses the production of boards or molded bodies by hot molding mixtures of lignocellulose-containing material and polyisocyanates. In the disclosed process, the pressing plates or molds may be treated with polyhydroxylic compounds (e.g.. glycerol, ethylene glycol, polyester polyols or polyether polyols) before compression molding. The fact that a separate operation is necessary for the application of the release agent and that part of the polyisocyanate is consumed by reaction with the release agent makes this process disadvantageous.
Another approach to improving the release behavior of molded bodies is disclosed in German Offenlegungschrift 2,325,926. In this disclosure, release agents which catalyze the formation of isocyanurate in the isocyanate are used. The disadvantage of this process is that the catalyst has a destabilizing effect on the isocyanate which effectively prevents production of an isocyanate binder which will satisfy a specification.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a composition which is useful as a binder for the production of composite materials.
It is also an object of the present invention to provide a binder composition which may be used for the production of composite materials which does not adversely affect the removability of a composite article from a mold.
It is a further object of the present invention to provide a binder composition which is storage stable.
It is another object of the present invention to provide a process for the production of composite materials in which the composite material may be readily removed from a mold.
These and other objects which will be apparent to those skilled in the art are accomplished by using a composition made up of (a) an aromatic polyisocyanate in combination with (b) a polyester obtained by self-condensation of ricinoleic acid, optionally with the use of a starter polyol.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention provides a composition made up of (a) an aromatic polyisocyanate and (b) a polyester having an average molecular weight of from about 600 to about 5000 which polyester is obtainable by self-condensation of ricinoleic acid, optionally using a C
2
-C
20
starter polyol, and optional additives.
In a preferred embodiment of the present invention, polyisocyanate (a) is a polyisocyanate based on (i) diphenylmethane diisocyanate or (ii) a mixture of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates in which the proportion of diphenylmethane diisocyanates in the polyisocyanate mixture is preferably between 35 and 75 wt %. It is also preferred that polyester (b) have an average molecular weight of from about 620 to about 3000. Where a starter polyol is used in the production of polyester (b), it is preferred that the polyol be 1,6-hexanediol. It is also preferred that components (a) and (b) have been caused to react together completely or partially, optionally not until during application of the composition to the material from which a composite material is to be made.
The present invention is also directed to the use of the above-described composition, optionally in combination with known polyhydroxylic compounds having a molecular weight of from about 400 to about 10,000, as a binder for the production of composite materials.
It is also preferred that the binder of the present invention be used to produce composite materials which are based on cellulose-containing and/or lignocellulose-containing materials. In another preferred embodiment of the invention, ground scrap plastics (most preferably isocyanate-based scrap plastics) are used together with cellulose-containing and/or lignocellulose-containing materials to produce composite materials.
In the compositions of the present invention, the weight ratio of component (a) to component (b) is usually between 100:1 and 100:200, preferably between 100:5 and 100:30.
Polyesters (b) which are preferably used in the compositions of the present invention are the polyesters obtained by self-condensation of ricinoleic acid on a C
2
-C
20
starter polyol. The polyesters obtained are hydroxyfunctional polyesters. It is also possible, however, to use polyesters that are obtained by self-condensation of ricinoleic acid as component (b). These self-condensation polyesters have one more carboxyl group per molecule than the polyesters produced using a starter polyol.
Any of the known polyols having a functionality of from 2 to 6 and a molecular weight of from about 62 to about 399 may be used as the C
2
-C
20
starter polyol for the production of the polyester to be used in the practice of the present invention. Specific examples of suitable starter polyols include: ethylene glycol; 1,2- and 1,3-propanediol; 1,4- and 2,3-butanediol; 1,6- and 2,5-hexanediol; 2-ethylhexanediol; 1,12-octadecanediol; 3-methyl-1,5-pentanediol; 1,8-octanediol; neopentyl glycol; 1,4-bis (hydroxymethyl) cyclohexane; 2-methyl-1,3-propanediol; glycerol; trimethylolpropane; 1,2,6-hexanetriol; 1,2,4-butanetriol; trimethylolethane; pentaerythritol; quinitol; mannitol; sorbitol; formitol; 1,4,3,6-dianhydosorbitol; methylglycoside; diethylene glycol; triethylene glycol; tetraethylene glycol and higher polyethylene glycols; dipropylene glycol and higher polypropylene glycols; and dibutylene glycol and higher polybutylene glycols.
In the production of composite materials (compression-molded materials) by hot molding using the compositions of the present invention as binders, other additives may optionally be used. Such additives include those known in the ad, e.g., polyether polyols having molecular weights of from about 400 to about 10,000 and/or alkylene carbonates (EP-0 352,558).
When the compositions of the present invention are used as binders, they make it possible to produce compression-molded materials (e.g., chipboards) by hot molding, optionally after a single conditioning of the mold by application of a release agent. Repeated application of a mold release agent is not necessary. A noticeable reduction of the molding time is also repeat
Kapps Manfred
Kasperek Peter
Konig Klaus
Schmidt Manfred
Vehlewald Peter
Bayer Aktiengesellschaft
Gil Joseph C.
Sergent Rabon
Whalen Lyndanne M.
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