PROCESS FOR PREPARING ADVANCED EPOXY RESINS EMPLOYING A PHOSPHONIUM TRIFLUOROACETATE CATALYST

Abstract: 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. The invention is characterized by employing as the catalyst, component (C), a phosphonium trifluoroacetate salt. The process of this invention produces an advanced epoxy resin wherein the difference obtained by substracting the present 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: -l- PROCESS FOR PREPARING ADVANCED EPOXY RESINS EMPLOYING A PHOSPHONIUM TRIFLUOROACETATE CATALYST Epoxy resins have heretofore been advanced in the presence of phosphonium catalysts disclosed by Dante in U.S. 3,477,990 and Perry in Canadian 893,191 and U.S. 3,948,855. However, the quantities of catalyst employed were that which would provide a resin having a percent epoxide value sufficiently close to the theo¬ retical epoxide value that no improvement in properties were envisioned. U.S. Patent Nos. 4,325,918 and 4,370,465 disclose the preparation of advanced epoxy resins having improved physical properties by employing a sufficient quantity of a phosphonium catalyst such that the resultant advanced epoxy resin had a percent epoxide value 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 desirably lower color than the color provided by those advanced epoxy resins produced by the process described in U.S. Patent Nos. 4,325,918 and 4,370,465. 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. 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 (C), a phosphonium trifluoro- acetate salt. Suitable glycidyl ethers of a dihydric phenol which can be employed in the present invention include those represented by the formula wherein A is a divalent hydrocarbon group having from 1 0 0 to 8 carbon atoms, -S-, -S-S-, -0-, -C-, -S-, or O PI 0 II -S-; each X is independently hydrogen, chlorine, bromine II ° 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, for example, catechol, hydroquinone, resorcinol and bisphenols such as those represented by the formula wherein A, X, 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. 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 I 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 al aryl 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 alkyl can be 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, N0 2 , and mixtures thereof. 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. OMPI Sty y , WIPO 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 0.8, parts of 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 from 100°C to 200°C, preferably from 120°C to 160°C, are suitable. Lower temperatures usually require longer reaction times whereas higher temperatures usually require shorter reaction times. The pressure employed is not particularly important and can be from about 1 mm Hg vacuum to 100 psig (0.1 to 791 kPa). However, it is usually preferred to employ pressures of from 5 psig to 20 psig (136 to 239 kPa). Any of the well known curing agents can be employed in the present invention to cure the epoxy resins. Such curing agents include, for example, amines, amides, guanidines, phenolic hydroxyl-containing 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 such as 1,6-xylene biguanide, polyhydric phenols, and mix¬ tures thereof. The quantity of curing agent employed 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 = 43 °wtER q + R tDHp DHF ^ 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 tetraethylammonium bromide in glacial acetic acid using crystal violet as an indicator. The epoxy groups react stoichiometrically with hydrogen bromide generated from the reaction of oiesi perchloric acid with tetraethyl ammonium bromide. When the epoxy groups have been reacted, the free hydrogen bromide causes the crystal violet to change color. The phosphonium trifluoroacetate salts employed as epoxy advancement catalysts in the examples (Table I) were prepared by the synthetic procedures described schematically below. Procedure A φ CF 3 C0 2 H Θ 0 3 P-Alkyl > ø 3 P-Alkyl + H 2 0 + C0 2 Procedure B 0 3 P-Alkyl + H 2 0 CF 3 C0 2 θ Procedure C CF 3 C0 2 H 0 3 P-Alkyl 0 3 P-Alkyl + 2CH 3 C0 2 H ft CH 3 OH CH 3 C0 2 -CH 3 C0 2 H CF 3 C0 2 θ Procedure D θ Φ Φ 0 3 P 0 3 PCH 2 CH 2 P0 3 + 2AgBr- Trademark of The Dow Chemical Company 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¬ ments 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 charged 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 5°C/minute (0.083°C/s) with a constant flow of N 2 over the reactants, unless otherwise indicated. When the temperature of the mixture reached 60°C, 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 130°C, 140°C, 150°C and finally at 160°C for 2 hours (7200 s). The reaction (B) was heated directly to 150°C with an exotherm occurring followed by post heating at 160°C for 3 hours (10800 s). OMPI 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 liquid diglycidyl ether of bisphenol-A having an average epoxide equivalent weight of 188.6, 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. DIHYDRIC PHENOL or 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. O PI :o DIHYDRIC PHENOL or THIOPHENOL D was 4,4'-phenoxybenzene dithiol, a dihydric thiophenol, having a thiophenolic thiol equivalent weight of 118. DIHYDRIC PHENOL or THIOPHENOL E was 4,4 « sulfonyldiphenol, a dihydric phenol, having a phenolic hydroxyl equivalent weight of 125. -» 2 TABLE I EXAMPLE REACTANTS NUMBER OR PHENOLIC OR THIO- COMP.EXPT. EPOXY RESIN PHENOLIC COMPOUND LETTER CATALYST, phr type/grams/equiv type/grams/equi . 1 0 3 ,EtPΦCF 3 C0 2 θ , 0.8 A/112.33/0.624 B/38.8/0.340 2 0 3 ,EtPΦCF 3 C0 2 θ , 0.43 B/200/1.060 A/82.8/0.304 3 3 ,EtPΦCF 3 C0 2 θ , 0.43 B/200/1.060 A/82.8/0.304 A* 0 3 ,EtPΦCH 2 C0 2 θ •CH 3 C0 2 H B/200/1.060 A/82.8/0.304 + 0.42 H0 2 CC0 2 H B* 0 3 ,EtPΦCH 2 C0 2 θ« CH 3 C0 2 H B/200/1.060 A/82.8/0.304 + 0.42 H0 2 CC0 2 H 4* 0 3 ,EtPΦCH 3 C0 2 θ•CH 3 C0 2 H B/200/1.060 A/82.8/0.304 + , 0.42 CF 3 C0 2 H C 0 3 ,EtPΦCH 3 C0 2 θ-CH 3 C0 2 H, 0.4 A/6/0.0334 B/3 .54/0.0311 5 0 3 ,EtPΦCF 3 C0 2 θ , 0.5 A/6/0.0334 B/3 .54/0.0311 6 0 3 ,EtPΘCF 3 C0 2 θ , 0.4 A/6/0.0334 D/3 .16/0.0268 TABLE I (continued) NUMBER OR ADVANCED RESIN PRODUCT COMP.EXPT. REACTION % EPOXIDE GARDNER LETTER CATALYST, phr CONDITIONS ! THEORY EXPERIMENTAL COLOR 1 0 3/ EtPΦCF 3 C0 2 θ , 0.8 B 8.0 6.1 <1 2 0 3 ,EtPΦCF 3 C0 2 θ , 0.43 A 11.5 10.0 1 3 0 3 ,EtPΘCF 3 C0 2 θ , 0.43 A 11.5 10.0 1 w/air atm A* 0 3 ,EtPΦCH 2 C0 2 θ -CH 3 C0 2 H A 11.5 10,0 2 + 0.42 H0 2 CC0 2 H B* 0 3 ,EtPΦCH 2 C0 2 •CH 3 C0 2 H A 11.5 10.0 4 + , 0.42 w/air atm H0 2 CC0 2 H 4* 0 3 ,EtPΦCH 3 C0 2 θ •CH 3 C0 2 H A 11.5 9.70 + , 0.42 CF 3 C0 2 H C 0 3 ,EtPΦCH 3 C0 2 θ -CH 3 C0 2 H, 0.4 A 1.0 1.9 2 5 0 3 ,EtPΦCF 3 C0 2 θ , 0.5 A 1.0 0.0 <1 6 0 3 ,EtPΦCF 3 C0 2 θ , 0.4 B 3.0 0.8 <1 . TABLE I (continued) EXAMPLE REACTANTS NUMBER OR PHENOLIC OR THIO- COMP.EXPT. EPOXY RESIN PHENOLIC COMPOUND LETTER CATALYST, phr type/grams/equiv type/grams/equi . 0 3 ,n-BuPΦCF 3 C0 2 θ, 0.6 C/6/0.0264 B/l.12/0.0098 8 0 3 MePΦCF 3 C0 2 θ, 0.35 C/6/0.0264 C/2.27/0.0146 9 0 3 ,CH 3 (CH 2 ) 15 ΦPCF 3 C0 2 θ, 0.45 C/6/0.0264 A/2.75/0.0101 10 0 3 ,PCH 2 CH 2 P0 3 2CF 3 C0 2 Θ , 0.8 A/6/0.0334 A/3.23/0.0119 D 0 3 ,EtPΦ _θ~0 2 CCQ 2 H, 0.4 A/6/0.0334 A/3 .23/0 .0119 TABLE I (continued) EXAMPLE NUMBER OR ADVANCED RESIN PRODUCT COMP.EXPT. REACTION % EPOXIDE GARDNER LETTER CATALYST, phr CONDITIONS THEORY EXPERIMENTAL COLOR 7 0 3 ,n-BuPΦCF 3 C0 2 θ, 0.6 B 10.0 7.3 1 8 0 3 ,MePΦCF 3 C0 2 θ, 0.35 B 6.0 4.1 1 9 0 3 ,CH 3 (CH 2 ) 15 PΦCF 3 C0 2 θ, 0.45 B 8.0 5.9 <1 10 0 3 ,PCH 2 CH 2 P0 3 2CF 3 C0 2 Θ , 0.8 B 10.0 7.6 <1 D 0 3 ,EtPΦ θ 0 2 CC0 2 H, 0.4 B 10.0 8.7 TABLE I (continued) EXAMPLE REACTANTS NUMBER OR PHENOLIC OR THIO- COMP.EXPT. EPOXY RESIN PHENOLIC COMPOUND LETTER CATALYST, phr type/grams/equiv type/grams/equiv. E 0 3 ,EtP Θ I θ , 0.5 A/6/0.0334 B/3.54/0.0311 F 0 3 ,EtPΦBr θ , 0.7 A/6/0.0334 A/3.23/0.0119 G 0 3 ,MePΦI θ , 0.8 A/6/0.0334 B/3.54/0.0311 H 0 3 ,n-BuPΦBr θ , 0.6 A/6/0.0334 B/2/0.0175 I 0 3/ CH 3 (CH 2 ) 15 PΦBr θ , 0.4 A/6/0.0334 B/3.30/0.0289 J 0 3 ,PCH 2 CH 2 P0 3 2Br θ , 0.8 A/6/0.0334 B/2/0.0175 K 0 3 ,EtPΦHC0 2 θ , 1.52 A/112.19/0.624 B/38.8/0.340 L 0 3 ETPΦH 2 P0 4 θ , 0.5 A/6/0.0334 A/3.23/0.0119 TABLE I (continued) EXAMPLE NUMBER OR ADVANCED RESIN PRODUCT COMP.EXPT. REACTION % EPOXIDE GARDNER LETTER CATALYST, phr CONDITIONS THEORY EXPERIMENTAL COLOR E 0 3 ,Etp Θ I θ , 0.5 B 1.0 2.1 3 F 0 3 ,EtPΦBr θ , 0.7 B 10.0 10.4 3 G 0 3 ,MePΦI θ , 0.8 B 1,0 2.3 4 H 0 3 ,n-BuPΦBr θ , 0.6 B 8.0 8.2 3 I 0 3 ,CH 3 (CH 2 ) 15 PΦBrθ, 0.4 B 2.0 2.3 2 J 0 3 ,PCH 2 CH 2 P0 3 2Brθ, 0.8 B 8.0 * 7.8 4 K 0 3 ,EtPΦHC0 2 θ , 1.52 B 8.0 6.4 5 L 0 3 ETPΦH 2 P0 4 θ , 0.5 B 10.0 9.4 2 TABLE I (continued) EXAMPLE REACTANTS NUMBER OR PHENOLIC OR THIO- COMP.EXPT. EPOXY RESIN PHENOLIC COMPOUND LETTER CATALYST, phr type/grams/equiv type/grams/equiv. M A, 0.3 A/6/0.0334 B/2/0.0175 11* 0 3 ,n-BuPΦBr C/6/0.0264 B/l.12/0.00982 + , 0.6 CF 3 C0 2 H *The two catalyst components were employed to prepare the catalyst in situ and were employed on a stoichiometric basis. . TABLE I (continued) EXAMPLE NUMBER OR ADVANCED RESIN PRODUCT COMP.EXPT. REACTION % EPOXIDE GARDNER LETTER CATALYST, phr CONDITIONS THEORY EXPERIMENTAL COLOR 11* 0 3 ,n-BuPΦBr B 10.0 7.5 + , 0.6 CF 3 C0 2 H *The two catalyst components were employed to prepare the catalyst in situ and were employed on a stoichiometric basis.

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.

Inventors: DOORAKIAN GEORGE A, GIST ADOLPHUS V, PAUL MARSHA A, DOORAKIAN, GEORGE, A., GIST, ADOLPHUS, V., PAUL, MARSHA, A.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1983
Main classification: C08G59
IPC codes: C08G59