CS243851B1 - Activated acid-base catalyst - Google Patents

Abstract

Activated acid-base catalyst for the crosslinking reaction of epoxy resins with polycarboxylic acid anhydrides, transportable by the interaction of (2,5-dihydroxybenzene)triphenylphosphonium inner salt with phthalic or maleic anhydride in a weight ratio of 2.3:1 to 1:4.

Description

(54) Activated acid-base catalyst

Activated acid-base catalyst for cross-linking epoxy resins with polycarboxylic acid anhydrides transportable by the interaction of (2,5-dihydroxybenzene) triphenylphosphonium inner salt with phthalic anhydride and / or. maleic acid in a weight ratio of 2.3: 1 to 1: 4.

The invention relates to an activated latent acid-base catalyst for crosslinking reactions of epoxy resins with polycarboxylic anhydrides.

A number of adhesives are used in technical practice. AO 237 035 describes a process for the production of a structurally rigid thermosetting adhesive, particularly suitable for electrotechnical applications, manufactured using a latent catalyst in the form of a quaternary phosphine inner salt. However, the handling of this very fine catalyst, which is sparingly soluble in most solvents, is inconvenient and difficult to dispense and disperse perfectly in the adhesive. These problems are overcome by the activated catalyst prepared according to the invention, since after activation they form long-term storage solutions, easily miscible with the components of the structurally rigid thermosetting adhesive.

The present invention is based on an activated latent acid-base catalyst for the crosslinking reaction of epoxy resins and polycarboxylic acid anhydrides formed by the interaction of (2,5-dihydroxybenzene) triphenylphosphonium inner salt with phthalic acid or malelic anhydride in a weight ratio of 2.3: 1 to 1: 4.

Preparation of (2,5-dihydroxybenzene) triphenylphosphonium inner salt by reaction of triphenylphosphine

with benzoquinone can be carried out in aromatic, resp. an ethereal solvent (J. Amer. Chem. Soc.

78, 5,614 (1956)). This adduct is either dried or merely freed from the major part of the solvent and allowed to interact with phthalic anhydride; maleic anhydride, usually in a weight ratio of 2.3: 1 to 1: 4. The activation is preferably carried out in a hydroxylated solvent, preferably ethylene glycol, at a temperature of 10 to 80 ° C, preferably 20 to 50 ° C, under normal or slightly elevated pressure. Upon completion of the interaction, a solution is formed which can be used directly as a catalyst for the cross-linking reaction and has a shelf life of several months.

The presence of phthalic anhydride, respectively. maleic, is required, in the absence of the hydroxylated solvent, only a heterogeneous mixture is formed, not an activated catalyst.

The following examples characterize the catalyst of the invention without limiting or limiting it.

Example 1

13.7 g of benzoquinone dissolved in 200 ml of toluene were allowed to react with 35 g of triphenylphosphine dissolved in 200 ml of toluene for 10 days, then the adduct was filtered off, washed 3 times with 200 ml of toluene and dried under high vacuum at 60 ° C for 6 hours. There was thus obtained (2,5-dihydroxybenzene) triphenylphosphonium salt in a yield of 69%. Its absorption spectrum in 95% aqueous ethanol showed a maximum at 267 µm and in its infrared spectrum bands ascribed to this compound were found in J. Amer. Chem. Soc. 78, 5,614 (1956)).

Example 2 g of the triphenylphosphine-benzoquinone reaction product described in Example 1 was activated by treatment with 40 g of phthalic anhydride dissolved in 700 ml of ethylene glycol. After 2 hours, a reddish-brown catalyst solution was formed, which was used in the manufacture of the structurally rigid thermosetting adhesive of AO 237 035, producing an adhesive having the same properties as a powdered, non-activated catalyst, but handling fine powder of toxic catalysts. dispersing the catalyst in the reaction mixture.

Example 3

Example 2 was repeated except that g maleic anhydride was used instead of phthalic anhydride. Again, when applied according to AO 237 035, the reaction time required to disperse the catalyst in the reaction mixture was substantially reduced and the work with fine dust of the phosphonium inner salt was avoided and the physical properties of the resulting adhesive were not adversely affected.

Example 4

In the absence of phthalic or maleic anhydride, 10 g of (2,5-dihydroxybenzene) triphenylphosphonium salt was not dissolved in 1000 ml of ethylene glycol. Due to the heterogeneity of the mixture, accurate dosing of the phosphonium salt into the adhesive was impossible.

Claims (1)

SUBJECT VYNALEZU Activated acid-base catalyst for the crosslinking reaction of epoxy resins with polycarboxylic acid anhydrides obtainable by interaction (2,5-dihydroxybenzene, triphenylphosphonium inner salts with phthalic anhydride or maleic acid in a weight ratio of 2.3: 1 to 1 and 4).