Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-07-02
2002-10-15
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S153000, C528S155000, C528S158000
Reexamination Certificate
active
06465599
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention refers to a new curing composition for phenolic resins, especially for the polymerization of resoles and the formation of novolaks.
2. Description of the Prior Art
Phenolic resins have become known for a rather long time. They may generally be classified in two groups, namely the resoles and the novolaks. The resoles are obtained by a condensation reaction starting from optionally substituted phenols and aldehydes, in particular formaldehyde, in a basic medium, whereas the condensation of the same starting products but in an acidic medium and generally in using other stoichiometric ratios leads to novolaks which may be hardened by crosslinking at elevated temperatures in the presence of formaldehyde or a formaldehyde liberating compound, for example hexamethylene tetramine.
For their use in practice, the phenolic resins are crosslinked or cured to the so-called phenoplasts which may be hard foams, composite products that contain extenders or fillers such as bakelite, or others. Certain phenolic resins are self-curing, especially such resins that are crosslinking via their reactive methylol groups, but this self-curing does not yield well-defined end products, and the hardening process is very slow.
The crosslinking of resoles and the formation of novolaks occur according to acidic mechanisms. To this end, sulfuric acid or toluene sulfonic acid are used for example. However, the use of these acids has the major disadvantage that these acids are imprisoned as such within the forming polymers during the polycondensation and crosslinking reactions; the finished products will therefore contain free acids that are very difficult to remove from the product and cause slow decomposition reactions. Therefore, other possibilities have already been proposed in order to overcome this drawback.
U.S. Pat. No. 3,870,661 (to P. J. Crook and S. P. Riley) discloses a foamed phenol-formaldehyde resin, obtained by reacting a resole resin with a sulfonated novolak in the presence of a surfactant and a foaming agent. Furthermore, U.S. Pat. No. 3,872,033 (to P. Boden, P. J. Crook, M. E. Hall and S. P. Riley) discloses a solid fire-retarding phenol-formaldehyde resin, obtained by reacting a resole with a hardening composition produced by reacting a sulfonated phenol with formaldehyde, in the presence of a surfactant and a foaming agent.
The hardening compositions or catalysts, respectively, used in these two documents are composed, as judged by the present inventors, of sulfonated linear phenolic oligomers. In fact, the above two patents do not disclose or suggest any concrete composition or configuration of these hardeners. The one skilled in the art knows that under the reaction conditions described in the two patent specifications, linear phenolic oligomers are formed that are sulfonated after or before the oligomerization reaction using phenol and formaldehyde.
These reaction conditions further comprise reaction temperatures and reaction times during the condensation of phenol and formaldehyde of at most 130° C. and 65 minutes in Crook et al. and 50° C. and 2 hours in Boden et al. Where para substituted phenols are used in Crook et al., which would be a necessary condition for producing cyclic phenolic oligomers, the reaction conditions are 75° C./45 minutes, absolutely insufficient for the formation even of traces of cyclics.
The hardening compositions and curing catalysts, respectively, that are known from the above discussed prior art suffer from the disadvantage that their composition will change within wide limits when the reaction conditions, such as temperature, time and the concentrations and relative amounts of reactants, are not strictly the same from one batch to another. Since the chemical and most physical properties of the compositions are not disclosed (with the exception of solids content of aqueous solutions and their viscosity) and thus cannot be reproduced, the properties of phenolic foams produced from these compositions will widely vary too. This fact follows directly from the lecture of both U.S. Patents referenced above.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the disadvantages of the known bridging compositions for resoles or condensation catalysts for novolaks by replacing the acids or the sulfonated linear phenolic oligomers that have been used until now, to improve the polycondensation and crosslinking processes, and to further improve the quality and usefulness of the finally obtained phenolic resins and novolaks. This object is attained by a new composition which contains (A) a first component selected from partially sulfonated cyclic phenolic oligomers and totally sulfonated cyclic phenolic oligomers, and (B) a second component selected from partially sulfonated linear phenolic oligomers and totally sulfonated linear phenolic oligomers, the weight ratio of component (A) to component (B) being comprised between 1 to 99% of component (A) and 99 to 1% of component (B).
The present invention further provides a curing composition, useful as a bridging agent in the polycondensation of resoles and in the formation of novolaks to be produced from a phenol and an aldehyde, said curing composition comprising an intimate blend of (A) from about 1% to about 99% of a first component selected from partially sulfonated cyclic phenolic oligomers and totally sulfonated cyclic phenolic oligomers, produced by reacting a para substituted phenol with formaldehyde in the presence of a basic catalyst and under substantially anhydrous conditions at temperatures of at least about 135° C., recovering cyclic phenolic oligomers from the reaction mixture, and partially or totally sulfonating these cyclic phenolic oligomers, and (B) from about 99% to about 1% of a second component selected from partially ant totally sulfonated linear phenolic oligomers produced by preparing linear phenolic oligomers from a phenol and formaldehyde in the presence of a basic or an acidic catalyst, recovering linear phenolic oligomers from the reaction mixture, and partially or totally sulfonating these linear phenolic oligomers.
Furthermore, this invention also includes a phenolic resin obtained by a polycondensation of a resole, the phenolic resin comprising, chemically incorporated into the microstructure of the polymer, a curing composition consisting of from about 1 to 100 % of at least one partially or totally sulfonated cyclic phenolic oligomer; that composition may further contain, if the percentage of said partially or totally sulfonated cyclic phenolic oligomer is lower than 100%, at least one partially or totally sulfonated linear phenolic oligomer and/or sulfonated monomeric phenol.
In an analogous manner, this invention also includes a novolak obtained by a polycondensation of an aldehyde, a phenol and a catalyst composition, the novolak comprising, chemically incorporated into its microstructure, said catalyst composition which consists of from about 1 to 100 % of at least one partially or totally sulfonated cyclic phenolic oligomer; that composition may further contain, if the percentage of said partially or totally sulfonated cyclic phenolic oligomer is lower than 100%, at least one partially or totally sulfonated linear phenolic oligomer and/or sulfonated monomeric phenol.
In this document, all percentages refer to the weight if not otherwise specified.
In a general manner, the sulfonated cyclic phenolic oligomers are called “calixarene sulfonic acids” and are produced by a dealkylating sulfonation of p-alkyl substituted calixarenes, or by first dealkylating such compounds and the sulfonating them. Details are discussed below.
Although it may be imagined that cyclic phenolic oligomers may theoretically be formed in the processes of the above discussed Crook and Boden references, the one skilled in the art knows that the amounts thereof possibly formed during the reactions which are disclosed, would be undetectably low since the reaction conditions, even if they were drastically reinforced, do not a
Choquard Philippe
Lamartine Roger
Mullis Jeffrey
Pitney Hardin Kipp & Szuch LLP
Transdiffusia S.A.
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