NZ206674A - Hardening phenol-formaldehyde resoles with hardener solutions containing alkyl esters of toluenesulphonic acid - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £06674 . N ■ I 2-06674 n> Priority Date(s): . .?/? Complete Specification Filed: rV;/A.?A Class: Qlj X/A..

J"'*."".""" [23 JAN W Publication Date: P.O. Journal, No: . ..J*U NO DRAWiMGS Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "PROCESS FOR HARDENING PHENOLIC RESINS" -I-,WE SOCIETE CHIMIQUE DES CHARBONNAGES SAf a French company, of Tour Aurore - Place des Reflets 92080 La Defense France, hereby declare the invention, for which -f/we pray that a patent may be granted to -nte-/us, and the method by which it is to be performed, to be particularly described in and by the following statement 2/ 0fC/9fi3^ ** r *// -l- ffelfowed by page I A.) 2.06-3 74 - 1 <kr- The present invention relates to a novel process for hardening phenolic resins. More especially, it relates to a process for hardening phenol-formaldehyde resols.

It is known to harden phenolic resols by addition 5 of strong acids. As acids it is for example possible to use hydrochloric acid, sulphuric acid, phosphoric acid, trichloroacetic acid and sulphonic acids, these various acids being used individually or as mixtures. Most commonly, these acids are employed in the form of aqueous 10 solutions, at concentrations varying between 20 and 60X.

For certain applications, the phenolic resins are hardened directly in the presence of reinforcing agents. The reinforcing agent used is in the form of fibres such as cellulosic fibres or glass fibres, of a nonwoven, for 15 example made from a high molecular weight polyester or from polyvinyl chloride, of a glass mat or of a woven fabric, for example made of an aromatic polyamide, glass or asbestos. After hardening of the phenolic resin, the composite material obtained is subsequently after-cured at a tempera-20 ture which is in general about 90°C. In the production of these composite materials, it is sometimes essential to be able to slow down the hardening of the phenolic resin. As examples of materials where it is preferred to slow down the hardening of the phenolic resin there may be 25 mentioned the production of phenolic prepregs and the production of phenolic materials prepared by filament winding.

The equipment used for the production of this latter type of material schematically consists of an impregnating trough containing the phenolic resin and its : 2 : 2 01> b 7 \ hardener, in which the glass fibres are impregnated. After impregnation, the fibres are drained and then wound around a mandrel. It is therefore essential that the phenolic resin should not harden too rapidly, so as to avoid the loss of substantial amounts of resins.

To solve this problem, the concentration of the acid hardener solution can be reduced and aqueous solutions having an acid concentration of less than 20% can be used. In that case, substantial amounts of water are entrained, which effectively slow down the hardening reaction but produce the disadvantage of imperfections in the hardened products (blisters and micro-pitting). It has been proposed to replace the water entirely by organic solvents in order to obtain dilute acid solutions. In that case, excessive amounts of solvents are retained in the finished products and in particular cause a worsening of the mechanical properties of these products, which most commonly manifests itself through crazing. Moreover, the use of these solvents presents storage problems and toxicity problems, which can only be solved by the use of expensive equipment. From an economic point of view, it is therefore of no value to use catalysts rich in organic solvent.

Attempts have therefore been made to find latent hardeners which adequately slow down the hardening of the phenolic resins without inhibiting it completely, and which contain acceptable amounts of solvents.

The present invention relates to a process for hardening phenol-formaldehyde resols with hardener solutions consisting optionally of acid and solvent, characterized in that these hardener solutions contain at least one alkyl V 206674 r, . - 3 - ester of a toluenesulphonic acid.

According to another characteristic of the process of the invention, the hardener solutions consist solely of an alkyl ester of a toluenesulphonic acid or of a mixture 5 of an alkyl ester of a toluenesulphonic acid, an organic solvent and concentrated sulphuric acid or an aromatic sulphonic acid. The amounts of the various constituents' , by weight are as follows: between 30 and 100/parts of the ester and by weight between 0 and 70 parts/'of a mixture of the acid, and the per hundred-parts of hardener solution by weight solvent/in the proportions of 50 to 702 /of acid and 30 to by weight -**"n 502/of solvent. Solutions of the ester alone are used if high pot lives are desired. If resins having less high pot lives are required, catalyst solutions consisting of mixtures of ester, solvent and acid are used. 15 The alkyl esters used in the composition of the hardener solutions are preferably methyl and ethyl esters of ortho- and para-to luenesu Iphonic acids. The organic solvent which may be used according to the invention consists of compounds possessing an alcohol group, such as 20 methanol, ethanol, propanol and isopropanol as well as polyols such as glycerol, dipropylene glycol and triethy- { ^ lene glycol. As the sulphonic acid which may be used according to the invention there may be mentioned, without implying a limitation, para-toluenesuIphonic acid, ortho-25 toluenesulphonic acid, benzenesu Iphonic acid and xylenesul-phonic acids.

The amounts of hardeners used are those conventionally employed for hardening resols. These amounts are between 4 and 25% by weight relative to the we^Kh"t of h; 2 9 APR 1986^1 resol and preferably between 6 and 12%. The resols used are the known resols prepared by condensing formaldehyde with phenol in the presence of an alkaline catalyst. These resols may optionally contain additives such as plasti-5 cizers, surfactants, fillers etc.

The hardening process of the present patent appLi- . cation is very suitable for use in certain processes for* producing phenolic prepregs as well as in processes for producing composite materials employing an apparatus wherein 10 the phenolic resin, to which its hardening catalyst has been added, is stored in a trough through which glass fibres travel constantly and thus become impregnated with phenolic resin. In general, the process of the invention is suitable for all techniques where it is necessary that 15 the phenolic resin should have a prolonged pot life but should also be hardenable by heat.

The examples which follow illustrate the present invention: EXAMPLE 1 100 parts by weight of a resol having the following characteristics are used: molar ratio formaldehyde/phenol = 1.5 solids content: 72% viscosity: 10 poises (1 Pa.s) reactivity: 115°C (according to a method which consists in determining the exothermic peak of a resin to which 10% of sulphuric acid and ethanol have been added). 6 parts by weight of a hardener having the following composition are added at ambient temperature: 2 0 6 $ 74 49% by weight of para-toluenesulphonic acid 2^% by weight of isopropanol * by weight of the methyl ester of para-toluenesulphonic ac i d.

The pot life of the resin at 20°C is 1 hour 30 minutes.

EXAMPLE 2 Example 1 is repeated, employing, at ambient temperature, the same amount of hardener as described in 10 Example 1, but using a phenolic resin which has the same characteristics as the resin previously used except that the reactivity is 83°C.

The pot life is 2 hours.

Comparative example 15 Example 2 is repeated, but replacing the hardener according to the invention by a known aqueous solution consisting of 60 parts by weight of para-toluenesulphonic acid.

On using 6 parts by weight of this catalyst with 20 the same resin as in Example 2, at ambient temperature, the pot life obtained is only 20 minutes.

EXAMPLE 3 Example 1 is repeated, using the resin of Example 1 but employing, per 100 parts by weight of phenoLic resin, 25 6 parts by weight of a catalyst consisting of: 21 parts by weight of para-toluenesulphonic acid 9 parts by weight of isopropanol 70 parts by weight of the methyl ester of para-to luenesu Iphonic ac i d.

The pot Life of the resin is 6 hours.

Comparative example On replacing the hardener of Example 3 by a known hardener consisting of an aqueous solution of para-toluene-5 sulphonic acid, a pot Life of the resin of 12 minutes is obtained.

EXAMPLE 4 Example 1 is repeated using the same resol as in Example 1 but employing various amounts of catalyst solu-10 tions consisting solely of the methyl ester of para- toluenesulphonic acid. The table below shows the amounts of catalyst employed per 100 parts of phenolic resin and the pot lives of the resin at 20°C.

Amount of the ester (parts by weight) 5 10 15 Pot Life 90 hours 24 hours 10 hours By way of comparison, the same resin hardened with the same amounts of a 60% strength aqueous solution of para-toluenesulphonic acid gives the following pot lives: 20 Amount of acid solution.. 5 10 15 Pot Life 16 min 6 min 3 min EXAMPLE 5 The mixture of resin and catalyst described in Example 1 is placed in the trough of an installation suit-25 able for the impregnation of glass fibres. This installation comprises a resin impregnation trough, a draining device and a device for guiding the impregnated glass fibres towards a mandrel.

The glass fibres are impregnated in the trough and ** .3 are then wound up on a mandrel. After winding is complete, the mandrel is placed in an oven at 65°C for 30 minutes. EXAMPLE 6 to 3 parts by weight of a mixture obtained from 21 parts of concentrated sulphuric acid, 49 parts of triethylene glycol and 30 parts of dipropylene glycol there are added To 100 parts by weight of the resin used in Example 1 10 there are added 10 parts by weight of the catalyst composition prepared above. The pot life of the resin is 5 hours at 20°C. The production of a laminate in a press requires a hardening time of 20 minutes at 80°C. The baking of a drop of resin on a Maquenne block at 80°C is 15 1 minute 30 seconds.

The same resin, with addition of 10 parts by weight (per 100 parts by weight of resin) of a known catalyst consisting of concentrated sulphuric acid (21 parts), triethylene glycol (49 parts) and dipropylene glycol (30 20 parts) has a pot life of 5 minutes at 20°C. Production of s Laminate, in a press, using this catalyst-containing resin requires a hardening time of 10 minutes at 80°C. The hardening time of a drop of resin on a Maquenne bLock at 80°C is 30 seconds.

EXAMPLE 7 A known catalyst is prepared by mixing 70 parts of benzenesu Iphon ic acid and 30 parts of dipropylene glycol.

From this known catalyst, the catalyst used for carry ing out the process of the invention is prepared by adding The following catalyst composition is prepared: 7 parts of the ethyl ester of para-toluenesulphonic acid r>; 7 parts by weight of the ethyl ester of para-toluenesulphonic acid to 3 parts by weight of the known catalyst prepared above. The table which follows shows the results obtained with the same resin as that used in Example 1: 5 Phenolic resin (parts by weight) 100 100 Known catalyst 10 Catalyst used according to the invention 10 Pot life (resin) 1 minute 43 minutes Baking on a Maquenne block at 80°C 30 seconds 1 minute 30 seconds Hardening in a press (80°C) 10 minutes 20 minutes : 9 :

Claims (6)

WHAT WE CLAIM IS;
1. -1. Process for hardening phenol-formaldehyde resols with hardener solutions consisting .optionally of acid and solvent, characterized in that these hardener solutions contain at least one alkyl ester of a toluenesulphonic acid.
2. 2. Process according to claim 1, characterized in that the hardener solutions are constituted solely of an alkyl ester of a toluenesulphonic acid.
3. 3. Process according to claim 1, characterized in that the solutions contain an alkyl ester of a toluenesulphonic acid, an organic solvent and toluenesulphonic acid or concentrated sulphuric acid.
4. 4. Process according to claim 3 as appendant on claim 1, characterized in that the solutions consist of 30 to 100 parts by weight of ester and 0 to 70 parts by weight of the mixture of acid and solvent per hundred parts of hardener solution.
5. 5. Process according to claims 1, 3 and 4, characterized in that the acid and the solvent are used in proportions of between 50 to 701 by weight of acid and 30 to 50% by weight of solvent.
6. 6. Process for hardening resols with hardener solutions as claimed in claim 1 substantially as herein particularly described with reference to any one of the Examples.