METHOD FOR PREPARING HIGH MOLECULAR WEIGHT EPOXY RESINS CONTAINING HYDROLYZED GLYCIDYL GROUPS

Abstract: High molecular weight epoxy resins containing hydrolyzed epoxy groups are prepared by reacting (A) a low molecular weight epoxy resin and (B) a hydroxyl-containing compound in the presence of (C) water (D) a hydrolysis catalyst and (E) a catalyst for effecting the reaction between (A) and (B).

Description: METHOD FOR PREPARING HIGH MOLECULAR WEIGHT EPOXY RESINS CONTAINING ΞYDROLYZΞD GLYC DYL GROUPS The present invention relates to a process. for preparing hydrolyzed epoxy resins. High molecular weight polyepoxide resins have been made more reactive by blending with a hydrolyzed or partially hydrolyzed low molecular weight or high molecular weight epoxy resin as disclosed by Walker in U.S. 3,632,336. Hydrolyzed and partially hydrolyzed epoxy resins have been prepared by dissolving the epoxy resin to be hydrolyzed in an inert organic solvent, admixing the resultant solution with a dilute aqueous solution of an acid catalyst, heating to a temperature of from 50°C to 374°C, washing to remove the acid catalyst and distilling the solvent to recover the hydrolyzed epoxy resin product. Such process is disclosed by Walker in U.S. 3,405,093, U.S. 3,632,836 and U.S. 3,787,508. Such process requires the necessity for removing and recovering an organic solvent therefrom, Q_-.PI A-. WlrO particularly when it is desired to employ the epoxy resins in the high molecular weight form such as in powder coatings, molding powders, epoxy ester resins for coatings, adhesives and the like. The present invention provides a process for preparing high molecular weight epoxy resin compositions containing hydrolyzed epoxy groups during the preparation of the high molecular weight epoxy resin in the absence of an organic solvent. Such a process is obviously desirable from an environmental standpoint. The present invention pertains to a process for preparing high.molecular weight epoxy resin compo¬ sitions containing at least one hydrolyzed glycidyl group which process comprises reacting in the absence of an inert organic solvent and a nonionic dispersant (A) at least one low molecular weight epoxy resin having an average of more than one glycidyl . group per molecule; (B) at least one compound having an average of more than one hydrαxyl group per molecule and (C) water in an amount essentially stoichiometric with the number of glycidyl groups to be hydrolyzed; said reaction being conducted in the presence of (D) a catalytic quantity of a catalyst for effecting the reaction between components (A) and (B); and optionally , (E) a catalytic quantity of a catalyst for reacting component (C) with a glycidyl group with the proviso that when component (Ξ) is not employed, the anount of water employed is in excess of that anount theoretically required to totally hydrolyze all of the epoxy groups of the epoxy resin produced from the reaction between components (A) and (B), and adding the step of removing the excess water. In the process of the present invention, components (D) and (Ξ) may be added sequentially. Such a process is characterized in that components (A), (B) and (C) are mixed and reacted in the presence of a catalytic quantity of component (E) at an atmospheric pressure and at a temperature below the boiling point of water for a time at which the * percent epoxide value of the reaction mixture remains substantially constant; thereafter adding a catalytic quantity of component (D) and continuing the reaction at a temperature of from 25°C to 300°C for a time at which the percent epoxide value of the reaction mixture remains substantially constant. For the purposes herein, the terms low molecular weight and .high molecular weight are relative in that it is meant that the high molecular weight epoxy resin has an average molecular weight: greater than that of the low molecular weight epoxy resin. By the term hydrolyzed glycidyl group,, it is meant the group represented by the formula H H H I t ! -C-C—C-H t t t H OH OH Suitable low molecular weight epoxy resins include, for example, glycidyl ethers of polyhydric aliphatic, cycloaliphatic and aromatic compounds, O PI V/IPO glycidyl esters of polycarboxylic acids, and mixtures thereof. Particularly suitable are the glycidyl ethers of polyhydric aromatic compounds such as phenols, bisphenols and phenol-aldehyde resins. Most par-icularly suitable low molecular weight epoxy resins which can be employed herein include those represented by the formulas wherein A is a divalent hydrocarbon group having from ■ one to 8 carbon atoms, -0-, -S-, -S-S-, 0 0 0 II II II -S-, -S- or -C-; each X and X' is independently II 0 hydrogen, bromine, chlorine- or a hydrocarbon group having from 1 to 8 carbon atoms; n has a value of zero or 1; n' has an average value less than 0.9, preferably less than 0.2 and most preferably from 0.001 to 0.15 and n" has a value of from 0.001 to 5, preferably from 0.1 to 2.5. Suitable compounds having an average of more than one hydroxyl group per molecule which can suitably - be employed herein include, for example, aliphatic, cycloaliphatic and aromatic compounds having a plurality of hydroxyl groups. Suitable aliphatic hydroxyl-containing compounds include, for example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyoxypropylene glycols, glycerine, pentaerythritol, neopentyl glycol, and dibromoneopentyl glycols. Particularly suitable dihydric phenols which can be employed herein include those represented by the formulas wherein A, X, X' , n and n" are as defined above. Suitable catalysts which can be employed as component (Ξ) in the process of the present invention when component (3) is an aromatic hydroxyl-containing compound include any catalyst which will catalyze the reaction between a vicinal epoxy group and a phenolic hydroxyl group. Such catalysts include, for example, those disclosed in U.S. Pat. Nos. 3,306,872; 3,341,580; 3,379,684; 3,477,990; 3,547,881; 3,637,590; 3,843,605; 3,948,855; 3, 56,237; 4,048,141; 4,093,650; 4,131,633; 4,132,706; 4,171,420; and 4,177,216. Particularly preferred catalysts are those quaternary phosphonium and animonium compounds such as, " for example, ethyltriphenylphosphonium chloride, ethyltri- phenylphosphonium bromide, ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium acetate, ethyltri- ' phenylphosphonium diacetate (ethyltriphenylphosphonium acetate•acetic acid complex), tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tetrabutyl¬ phosphonium iodide, tetrabutylphosphonium acetate, tetrabutylphosphonium diacetate (tetrabutylphosphonium acetate* acetic acid complex-), butyltriphenylphosphonium tetrabromobisphenate, butyltriphenylphosphonium bis- phenate, butyltriphenylphosphonium bicarbonate, ethyl¬ triphenylphosphonium bisphenate, benzyl rimethylammonium chloride and tetram thy1ammonium hydroxide. Suitable catalysts which can be employed as component (Ξ) when component (3) is an aliphatic- or cycloaliphatic-containing hydroxyl compound include the Lewis acids such as, for -example, boron trifluoride, stannic chloride, aluminum chloride, ferric chloride, aluminum bromide, zinc chloride, silicon tetrachloride, titanium chloride, and mixtures thereof. The quantities of epoxy resin and hydroxyl- containing co ounds emϋloyed are that recruired to obtain the desired molecular weight and are usually employed in such quantities as will provide an epoxide:total phenolic hydroxyl ratio of from 40:1 to 1.2:1, preferably from 10.:1 to 1.5:1. The quantity of catalyst component (D) employed depends upon the particular reactants and catalyst being utilized and is usually in the range of from 0.1 to 10 millimoles, preferably from 0.2 to 6 millimoles per equivalent of the epoxide reactant. Higher .quan- titles of catalyst are desired when higher molecular weight products are to be prepared- The temperature at which the reaction can be conducted depends upon the particular reactants and catalysts employed but usually ranges from 25°C to 300°C, preferably from 90°C to 250°C. The higher the temperature and the higher the concentration of catalyst, the less time that is required for the reaction to reach a specific degree of completion. When excess water is employed in the process, the amount not reacted can be removed by any suitable means such as, for example, vacuum distillation, molecular sieves, or inert gas purge at elevated temperatures; however, it is preferred to remove the excess water by vacuum distillation. When a hydrolysis catalysis is not employed, the extent of hydrolysis depends upon the reaction conditions and amount of water. However, at constant reaction conditions, the greater the excess quantity of water the greater the hydrolysis. Suitable hydrolysis catalysts for reacting water with a glycidyl group include any suitable acid or base catalyst. Particularly suitable are the acids disclosed in U.S. Patent 3,405,093. The catalyst for the hydrolysis reaction can be employed in any suitable quantity which catalyzes the reaction which is usually from 0.01 to 20, preferably from 0.1 to 0.7 percent by weight based upon the amount of low molecular weight epoxy resin. The theoretical percent epoxide is calculated by the following formula THEORETICAL % EPOXIDE = 43 ° Q Wr jg S ^ W t O E^ ΞqER = epoxide equivalents from the epoxy resin. ΞqOΞ = hydroxyl equivalents from the hydroxyl- -containing compound. wtER = weight of epoxy resin employed. wtOH = weight of hydroxyl-containing compound employed. Theoretical EEW is calculated by the following formula A3 Theoretical EEW = a % / E _,-poxi.d_.e -E,xpressed as a Fraction Theoretical 100% hydrolysis is calculated by determining what amount of water is required to theoret¬ ically hydrolyze the remaining epoxide content of the resin resulting from the reaction of (A) and (3). Thus, EqΞ 2 0 (equiv. Ξ 2 0) = ΞqER - ΞqOΞ for 100% hydrolysis theoretically. Employing the above formula, the theoretical quantity of water for 100% hydrolysis for Example 1 is calculated as follows: ΞqΞ 2 0 = 4.197 - 1.997 = 2.2. The percent hydrolysis is determined as follows: % <•, -hyd ■_rol-ysis = TPE A & 3-—- T?E A,' 3 & D x ,10 Λ 0 Λ TPE A & 3 wherein: TPE A & 3 = theoretical % epoxide after reaction of A'& B TPE A, B Se D ~ theoretical % epoxide after reaction of A, B & D The following examples are illustrative of the invention but are not to be construed as to limiting the scope of the invention in any manner. EXAMPLES 1-5 A series of high molecular weight epoxy resins were prepared by adding to a Parr autoclave reactor the indicated quantities of a diglycidyl ether of bisphenol A having an epoxide equivalent weight (SEW) of 184, bisphenol A, water and as a catalyst for the reaction between the epoxy resin and bisphenol A, ethyltriphenylphosphonium acetate-acetic acid complex as a 70% solution in methanol. The reaction was con- ducted at 120°C for 2 hours at autogenous pressure, after which the unreacted water was removed by vacuum stripping at 190°C for 30 minutes. The quantities of catalyst in each instance was 0.5 grams of the 70% solution. The quantities of reactants and results are given in the following Table I. TABLE I COMPONENT AND EXAMPLE EXAMPLE EXAMPLE EXAMPLE EXAMPLE PRODUCT PROPERTY 1 2 3 4 5 EPOXY RESIN (ER) grams 772.3 752.2 752.7 752.9 816.8 equiv. 4.197 4.088 4.091 4.092 4.439 BISPHENOL A (BPA), grams 227.7 247.8 247.8 247.8 185.2 equiv. 1.997 • 2.174 2.174 2.174 1.625 WATER (W), grams 55 55 71.6 90.1 109.9 equiv. 3.056 3.056 3.978 5.006 6.106 EQUIV. RATIO, EP/BPA/W 1/.476/- 1/.532/- 1/.531/- 1/.531/- 1/.366/- .728 .748 .972 1.223 1.376 THEORETICAL AMOUNT OF WATER TO HYDROLYZE 100% OF EPOXY * GROUPS, equiv. 2.2 1.914 1.917 1.918 2.814 EXCESS WATER, equiv. 0.056 1.142 2.061 3.080 3.292 THEORETICAL EEW/% EPOXIDE 456/9.43 525/8.19 525/8.19 525/8.19 354/12.15 ACTUAL EEW/% EPOXIDE 492/8.74 618/6.96 713/6.03 902/4.77 1117/3.85 % HYDROLYSIS 7 15 26 41 68 EXAMPLES 6-9 A series of high molecular weight epoxy resins were prepared by adding to a Parr autoclave reactor the indicated quantities of a diglycidyl ether of bisphenol A having an epoxide equivalent weight (EEW) of 184, bisphenol A, water, as a catalyst for reacting the epoxy resin with bisphenol A, ethyltri¬ phenylphosphonium acetate ♦ acetic acid complex as a 70% solution in methanol and as a catalyst for hydrolysis, oxalic acid dihydrate. The reaction temperatures and times were between 120° and 140 β C for one hour and 190°C for one hour followed by the application of a vacuum for 30 minutes to remove any unreacted matter. ' The quantities of reactants and results are given in the following Table II. TABLE II COMPONENT AND EXAMPLE EXAMPLE EXAMPLE EXAMPLE PRODUCT PROPERTY 1 2 3 4 EPOXY RESIN (ER) grams 857.3 057 020 790.3 equiv. 4.659 4.650 4.457 4.295 BISPHENOL A (BPA), grams 145 150 100 209.7 equiv. 1.272 1.316 1.579 1.039 WATER (W) # grams 27.5 10 10 9.22 equiv. 1.520 0.556 0.556 0.512 EQUIV. RATIO, EP/BPA/W 1/.273/.328 1/.203/.119 1/.354/.125 1/.428/.119 THEORETICAL EEW 1 557 365 436 521 , ACTUAL EEW 574 303 446 510 % HYDROLYSIS (THEORETICAL) 45 17 20 21 % HYDROLYSIS (actual 2 ) 40 21 22 21 VISCOSITY @ 150°C, centistokes 260 00 100 355 (m 2 /S x 10 3 ) (0.260) (0.000) (0.100) (0.355) 1 The theoretical EEW includes the reaction with water. 2 The actual % hydrolysis was determined by change in % epoxide. ΞXAMPLΞ 10 The hydrolysis reaction was carried out at atmospheric conditions when the temperature for reaction was below the boiling point of water. A reaction mixture was prepared containing 174 g. , 1 eq, of a diglycidyl ether of bisphenol A having an EEW of 174; 57 g., 0.5 eq, of bisphenol A; 1.8 g. , 0.20 eq, of "water and 0.02 moles of oxalic acid. When reacted together at 80°C for 45 minutes, the reaction mixture contained 0.90 eq. of epoxy. Then 0.478 g. , 084 moles, of ethyltriphenylphosphonium acetat •acetic acid complex as a 70% solution in methanol was added and the regular resin advancement was carried out to yield a solid - resin having 7.4% epoxide.

Claims: CLAIMS 1. A process for preparing a high molecular weight epoxy resin composition containing at least one hydrolyzed glycidyl group characterized by reacting in the absence of an inert organic solvent and a nonionic dispersant (A) at least one low molecular weight epoxy resin having an average of more than one glycidyl group per molecule; (3) at least one compound having an average of more than one hydroxyl group per molecule; and (C) water in an amount stoichiometric with the number of glycidyl groups to be hydrolyzed; said reaction being conducted in the presence of (D) a catalytic quantity of a catalyst for effecting the reaction between components (A) and (3) and optionally (Ξ) a catalytic quantity of a catalyst for reacting component (C) with a glycidyl group with the proviso that when component (Ξ) is not employed, the amount of water employed is in excess of that amount theoretically required to totally hydrolyze all of the epoxy groups of the epoxy resin produced from the reaction between components (A) and (3), and adding the step of removinσ the excess water. o...?ι 2. The process of Claim 1 characterized in that components (A), (B) and (C) are mixed and reacted in the presence of a catalytic quantity of Component (E) at atmospheric pressure and at a temperature below the boiling point of water for a time at which the percent epoxide value of the reaction mixture remains substan¬ tially constant; thereafter adding a catalytic quantity of component (D) and continuing the reaction at a temperature of from 25°C to 300°C for a time at which the percent epoxide value of the reaction mixture remains substantially constant. 3. The process of either of Claims 1 or 2 character ized in that component (A) is a glycidyl ether of an aromatic hydroxyl-containing compound; component (3) is an aromatic hydroxyl-containing compound; component (D) is a phosphonium compound and components (A) and (3) are present in quantities which provide an epoxy:hydroxyl ratio of from 1.2:1 to ' 40:1. 4. The process of Claim 3 characterized in that component (A) is a diglycidyl ether of a polyhydric phenol represented by the formulas or wherein A is a divalent hydrocarbon group having from one to 8 carbon atoms, -0-, -S-, -S-S-, 0 0 0 II II II . -S- , -S- or -C- ; each X and X ' is independently II 0 hydrogen, bromine, chlorine or a hydrocarbon group having from 1 to 8 carbon atoms; n has a value of zero or 1 and n' has an average value of less than 0.9 and component (3) is represented by the formulas X 1 or wherein each A, X, X' and n are as defined above and components (A) and (3) are employed in quantities such that the epoxide:hydroxyl ratio is from 1.5:1 to 10:1. 5. The process of Claim 4 characterized in that component (A) is an epoxy resin represented by formula II wherein n f has an average value of less than 0.2 and component (3) is a hydroxyl-containing compound repre¬ sented by formula V. 6. The process of Claim 5 characterized in that each X and X 1 is independently hydrogen, chlorine or bromine; each n has a value of 1 and n' has an average value of from 0.001 to 0.15. 7. The process of Claim 6 characterized in that component (A) is a diglycidyl ether of bisphenol A; component (3) is bisphenol A; catalyst (E) is oxalic acid and catalyst (D) is ethyltriphenylphosphonium acetate•acetic acid coπrolex

Inventors: CAVITT MICHAEL B, DAVIS RHETTA Q, MCCRARY AVIS L, STEVENS MICHAEL G
Applicants: DOW CHEMICAL CO, DOW CHEM CO
Application year: 1981
Main classification: C08G59
IPC codes: C08G59, C09D163, C09J163