CA1203943A

CA1203943A - Process for preparing epoxy resins employing a phosphonium trifluoroacetate catalyst

Info

Publication number: CA1203943A
Application number: CA000431038A
Authority: CA
Inventors: George A. Doorakian; Marsha A. Paul; Adolphus V. Gist
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1982-06-23
Filing date: 1983-06-23
Publication date: 1986-04-29
Also published as: IT1203707B; EP0111562A1; IT8321737A0; ES523550A0; WO1984000171A1; EP0111562A4; ES8504222A1

Abstract

ABSTRACT OF THE DISCLOSURE
This invention is directed to a process for advancing epoxy resins in molecular weight by reacting (A) an epoxy resin which is a glycidyl ether of a dihydric phenol or thiphenol having an average of more than one glycidyl ether group per molecule with (B) a dihydric phenolic or thiophenolic compound in the presence of catalytic quantities of (C) a phosphonium catalyst. The invention is characterized by employing as the catalyst, component (C), a phosphonium trifluoro-acetate salt.
The process of this invention produces an advanced epoxy resin wherein the difference obtained by subtracting the percent epoxide obtained by analysis from the theoretical percent epoxide is from 0.5 to 4, often from 1 to 2. The advanced epoxy resins prepared by the process of this invention are suitable for use in preparing electrical laminates.

Description

94~3 PROCESS FOR PREPARING
ADVANCED EPOXY RESINS EMPLOYING
A PHOSP~ONIUM TRIFLUOROACETATE CATALYST

Epoxy resins have heretofore been advanced in the presence of phosphonium catalysts disclosed by Mark F. Dante et al. in U.S. 3,477,990 dated November 11, 1969; William O. Perry in Canadian 893,191 dated February 15, 1972, and William O. Perry in U.S.
3,948,855 dated April 6, 1975. However, the quantities of catalyst employed were that which would provide a resin having a percent epoxide value sufficiently close to the theoretical epoxide value that no improvement in properties were envisioned.

U.S. Patents 4,325,918 (Donald A. Luke, et al.
dated April 20, 1982) and 4,370,465 (Ross C. Whiteside, Jr., et al. dated January 25, 1983) disclose the prepara-tion of advanced epoxy resins having improved physical properties by employing a sufficient quantity of a phos-phonium catalyst such that the resultant advanced epoxy resin had a percent epoxide lower than the theoretical percent epoxide value The process of the present invention produces advanced epoxy resins having a percent epoxide value lower than the theoretical percent epoxide and a desir-ably lower color than the color produced by those advanced epoxy resins produced by the process described in US. Patents 4,325,918 and 4,370,465. The difference O
30,527A-F l obtained by subtracting the percent epoxide obtained by analysis from the theoretical percent epoxide i5 from 0.5 to 4, often from 1 to 2. The advanced epoxy resins prepared by the process of this invention are suitable for use in preparing electrical laminates.

The present invention pertains to a process for advancing epoxy resins in molecular weight by reacting (A) an epoxy resin which is a glycidyl ether of a dihydric phenol or thiophenol having an average of more than one glycidyl ether group per molecule with (B) a dihydric phenolic or thiophenolic compound in the presence of catalytic quantities of (C) a phosphonium catalyst, wherein the improvment comprises employing as the catalyst, component O a phosphonium ~rifluoro-acetate salt.

Suitable glycidyl ethers of a dihydr1c phenolwhich can be employed in the present invention include those represented by the formula H2C-CH-CH2 (A)x Z-CH2-CH-CH Z
X X n X O
~}( A ) ~s~Z-CH2 CH2 X
wherein A is a divalent hydrocarbon group having from 1 O O
to 8 carbon atoms, -So, -S-S-, -O-, -C-, US-, or 30,527A-F -2-3~3 -S-; each X is independently hydrogen, chlorine, bromine or a hydrocarbon group having from 1 to 10 carbon atoms; each Z is independently 0 or S; x has a value of zero or one and n has a value such that the EEW is from 156 to 400, preferably from 177 to 190, calculated on the basis of X being hydrogen.

Particularly suitable are the diglycidyl ethers of bisphenol A and tetrabromobisphenol A.

Suitable dihydric phenolic or thiophenolic compounds include, or example, catechol, hydrog~linone, resorcinol and bisphenols such as those represented by the formula ; HZ Ax 2H

wherein A, I, Z and x are as defined above.

Particularly suitable dihydric phenolic compounds are bisphenol A and tetrabromo bisphenol A.

The phosphonium trifluoroacetate salt catalysts employed herein can be in essentially pure form or they can be prepared in situ without purification other than filtration of solid precipitated by-products of the reaction between a tetrahydrocarbyl phosphonium compound and trifluoroacetic acid or a salt thereof.

.
.

30,527A-F -3-_g _ Suitable phosphonium compounds which can be employed herein include, for example, those compounds having at least one phosphonium cation group repre-sented by the formula R
R P-R
R
wherein each R is independently a hydrocarbyl or substi-tuted hydrocarbyl group having from 1 to 20, preferably from 1 to 6, carbon atoms or substituted hydrocarbyl groups. It is preferred that at least one, preferably two and most preferably three, of the R groups be an aromatic group i.e., an aryl group or an alkaryl group such that the phosphorus atom is attached directly to the aromatic ring of such aryl or alkaryl group.

By the term hydrocarbyl, it is meant that the groups can be alkyl, aryl, alkaryl, or aralkyl and the :~ 20 alkyl can ye either cyclic or acyclic. By substituted hydrocarbyl it is meant that the hydrocarbyl groups can contain one or more substituent groups such as, for : example, Cl, Br, I, NO2, and mixtures thereof.

I; The R groups can contain any substituent group which will not deactivate the catalyst under the conditions in which they are employed.

It is preferred that the phosphonium cation contain at least one aromatic ring and at least one alkyl group attached directly to a phosphorous atom.

30, 527A-F -4-., I, 39~3 --5~

Suitable anions include the halides, such as, for example, Cl, Br, and I, as well as carboxylates, dicarboxylates, phosphates, nitrates, sulfates, nitrites, sulfites, borates, chromates, and mixtures thereof.

The dihydric phenol and the glycidyl ether of a dihydric phenol are employed in quantities such that the theoretical percent epoxide of the resultant product has the desired value.
.. . .
The quantity of catalyst will of course vary depending upon the particular catalyst employed; however, for most catalysts, from 0.1 to 1.5, preferably from 0.2 to 0.8l parts ox catalyst by weight per 100 parts by weight of glycidyl ether of dihydric phenol can be employed.

The reaction conditions employed to prepare :~ the advanced epoxy resins can vary, but temperatures of rom 100C to 200C, preferably from 1~0C to 160C, are suitable Lower temperatures usually require longer reaction times whereas higher temperatures usually require shorter reactlon times.

:; The pressure employed is not particularly important and can be from about 1 mm Hg vacuum to 100 I: : psig (O.l to 791 kPa). however, it is usually preferxed to employ~pressures of from 5 psig to 20 psig (136 to : 25 239 kPa~.

: Any of the well known curing ayents can be employed in the pr.esent invention to cure the epoxy resins. Such curing agents include, for example, amines, amides, guanidines, phenollc hydroxyl-containing 30,527A-F -5-materials, carboxylic acids, carboylic acid anhydrides, imidazoles, biguanides, and mixtures thereof.

Particulary suitable curing agents include, for example, guanidines such as for example, dicyan-diamide and tetramethyl guanidine and biguanides suchas 1,6-xylene biguanide, polyhydric phenols, and mix-tures thereof.

The quantity of curing agent employer depends upon the particular curing agent employed and the properties desired in the resultant cured resin, all of which is well known by those persons reasonably skilled in the art and discussed in HANDBOOK OF EPOXY RESINS, by Lee and Neville, McGraw Hill, 1967.

The theoretical percent epoxide is calculated by the following formula THEORETICAL PERCENT EPOXIDE =

EqER = epoxide equivalents from the epoxy resin.
EqDHP = phenolic hydroxyl equivalents from the dihydric phenol.
WtER = weight of epoxy resin employed.
WtDHP = weight of dihydric phenol employed.

The actual percent epoxide was determined experimentally by titration with perchloric acid in glacial acetic acid by the liberation of hydrogen bromide generated by the addition of tetraethylammoni bromide in glacial acetic acid using crystal violet as an indicator. The epoxy groups react stoichiometrically with hydrogen bromide generated from the reactlon of 30,527A-F -6-,, ~L~:03~3 perchloric acid with te-trae-thyl ammonium bromlde. When the epoxy groups haze been reacted, the free hydrogen bromide causes the crystal violet to change color.

The phosphonium trifluoroaceta~e salts employed as epoxy advancement catalysts in the examples (Table It were prepared by the synthetic procedures described . schematically below.
Procedure A ...
CF3CO2H'' 03P-Alkyl - 03P Alkyl + H20 + C02 ~3 5 Procedure B
DOWER ion exchange resin 03P Alkyl r~Sln [eQH~ >~3P-Alkyl CF3CO2H
Bre CH30H L OH
f 03P-Alkyl H20 20 - CF3Co29 Procedure C
:
CF3C02H _ _ 03P-Alky~ >03P-Alkyl + 2CH3C2H
e CH30H
: 25 CH3C02 CH3C02H CF3C0 : Procedure D
al 2AgO2CCF3 0 ~3 03P-CH2CH2P03 > 03PCH2CH2P03 -t 2AgBr~
e CH30H
302 Br 2CF3C0 .
Trademark o The Dow Chemical Company 30, 527A-F -7 The procedure (A) described above was employed to prepare the catalyst employed in Examples 1-5.

The procedure (B) described above was employed to prepare the catalyst employed in Examples 6, 7, 8, 10, 11 and 12.

The procedure (C) described above was employed to prepare the catalyst employed in Comparative Experi-menus A, B and C.

The procedure (D) described above was employed to prepare the catalyst employed in Example 9.

GENERAL PROCEDURE FOR RESIN PREPARATION
To a reaction vessel equipped with a means of pressure regulation, stirring, temperature control and indication of nitrogen purge was chargPd the desired weight of the specified low molecular weight diglycidyl ether of a dihydric phenol and the desired weight of the specified dihydric phenol or thiophenol. The mixture was heated at a rate of 5C/minute (0.083C/s) with a constant 1Ow ox N2 over the reactants, unless otherwise indicated. When the temperature of the mixture reached 60C, the desired amount of the speci-fied phosphonium salt dissolved in methanol was added.
The mixture was heated at the desired reaction condi-tions (specified as A or B in Table I) to give the resultant product. The reaction condition (A) consists of heating the reaction mixture for one hour (3600 s) at the temperatures of 130C, 140C, 150C and finally at 160C for 2 hours (7200 s). The reaction (B) was heated directly to 150C with an exotherm occurring followed by post heating at 160C for 3 hours (10800 s).

30,527A-F -8-~L203943 REACTANTS FOR RESIN ADVANCEMENT

EPOXY RESIN A was a liquid diglycidyl ether of -bisphenol-A having an average epoxide equivalent weight of 179.9, percent epoxide of 23.90.

EPOXY RESIN B was a liquld diglycidyl ether of bisphenol-A having an average epoxide equivalent weight of 18~.6, percent epoxide of 22.8.

EPOXY RESIN C was a liquid diglycidyl ether of

2,2' diallyl bisphenol-A having an average epoxide equivalent weight of 227.5, percent epoxide of 18.9.

i~CH2C~1~2 1 CH2cH=cH2 - 2 .
DIHYDRIC PHENOL ox THIOPHENOL A was tetrabromobis-phenol-A, a dihydric phenol, having a phenolic hydroxyl equivalent weight of 272 and percent bromine content of 58.85 percent.

DIHYDRIC PHENOL or THIOPHENOL B was bisphenol-A, a dihydric phenol, having a phenolic hydroxyl equivalent : weight of 114.

DIHYDRIC PHENOL_or THIOPHENOL C was 2,2'diallyl bisphenol-A, a dihydric phenol, having a phenolic hydroxyl equivalent weight of 155.

:

30,527A-F ~9-.,~

3~3 O OH
i L C~2cH=cH2 _ 2 DIHYDRIC PHENOL or THIOPHENOL D was 4,4'-phenoxybenzene _ .... ..
dithiol, a dihydric thiophenol, having a thiophenolic thiol equivalent weight of 118.

O SH

DI~YDRIC PHENOL or THIOPHENOL E was 4,4'sulfonyldiphenol, a dihydric phenol, having a phenolic hydroxyl equivalent weight of 125.

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Claims

CLAIMS:

1. A process for advancing epoxy resins in molecular weight by reacting (A) an epoxy resin which is a glycidyl ether of a dihydric phenol or thiophenol having an average of more than one glycidyl ether group per molecule with (B) a dihydric phenolic or thiophenolic compound in the presence of catalytic quantities of (C) a phosphonium catalyst, characterized by employing as the catalyst, component (C), a phosphonium trifluoro-acetate salt.

2. The process of Claim 1 characterized in that the catalyst is formed in situ from trifluoroacetic acid or a salt thereof and a phosphonium compound having a halide, carboxylate, dicarboxylate, carboxylate?carboxylic acid complex, phosphate, nitrate, sulfate, nitrite, sulfite, borate or chromate as the anion.

3. A process of Claim 2 characterized in that the catalyst is prepared in situ from trifluoro-acetic acid and ethyltriphenyl phosphonium acetate?acetic acid complex salt.