CA2151745A1

CA2151745A1 - Process for producing a high molecular weight epoxy resin

Info

Publication number: CA2151745A1
Application number: CA002151745A
Authority: CA
Inventors: Toshiaki Ogiwara
Original assignee: Individual
Current assignee: Dow Chemical Co
Priority date: 1993-10-15
Filing date: 1994-10-06
Publication date: 1995-04-20
Also published as: CZ156295A3; AU7930194A; KR950704391A; RU95113592A; JPH07109331A; WO1995010556A1; PL309390A1; EP0677073A1; CN1115577A; BR9406155A

Abstract

The present invention provides a process for producing a high molecular weight epoxy resin by polymerizing an epoxy resin having an average epoxide group number of two per molecule with a divalent phenol compound in the presence of a glycol ether having no hydroxyl group in .alpha.-position as a solvent. The preferable glycol ethers used in the present invention include propyleneglycol ethers such as propyleneglycol methylether, propyleneglycolmethylether acetate, propylenepglycol propylether and propyleneglycol monobutylether.

Description

~ WO 95/10556 PCT/US94/11349 21~17~5 PROCESS FOR PRODUCII\JG A HlGrl MOLECULAR WEIGHT EP~XY RESIN

The present inventlon relates to a process for producing a high molec~lar welgntepoxy resin usefui for adhesives, Insulating mater als, paints and other coatings moldmgs and 5 the like, and more particularly relates to a process for producing a high molecular welgtlt epo~y resi n i n shorter ti me.
A high molecular weight epoxy resin Is produced by reactmg a bifunctional epoxy resin having relatively low molecularweight with a divalent phenol compound. This process ,s generally called an nadvancement" process Regarding the advancement process, for example, 10 Japanese patent publ ication Kokoku 28-4494 d iscloses a process usi ng no sol vent for polymerization. However, the advanced res~ n made by that process has an average molecular weight of only about 11,000.
Other advancement processes, which use a solvent for polymerizatjon, are described in Japanese Kokai 04-12124, 54-52200,60-118757, 60-144323 and 6n-114324. In these publications, the preferred solvents include methylethyl ketone. methylisobutyl ketone, cyclohexane, ethyleneglycol monoethylether, ethyleneglycol monomethylethe- and 1~1, N-dimethyl acetamide.
However, when the high molecuiarweight epoxy resin is produced by uslng a low boiiing point solvent such as methylethyl ketone, the reaction time becomes qulte ong and a 20 great amount of a catalyst is required, because a reaction temperature cannot be ra;sed Wtlen a high boiling point solvent such as ethyleneglycol ethylether, ethyleneglycol buty'ethel~ or N, N-dimethyl acetamide is used, the polymerization can be carried out at a high temperature so that polymerizatlon time can be shortened somewhat. However, in terms of productlvity, ;l would be desirable to complete the higher molecular weight polymerizatlon In an even shorter 25 ti me.
The purpose of the present invention is to provide a process to produ~e a higher molecularweightepoxyresininshortertimebyusingasolventhavinghighernon-toxlcity.
As the result of research and development to solve the above-ment~oned problems, the inventor discovered that glycol ethers which contain a prirnary hydro)~yl group 30 withrespecttoethergroupsorotherhydroxylgroupsmayreactwithanepo~t,degroupinan epoxy resin. That reaction terminates the epoxy resin chain and prevents high mo,ecular weight polymerization.
Q Accordingly, the present Invention provides a process for producmg a high molecular weight epoxy resin by reacting:
J 35 (1) an epoxy resin which contains on average more than 1 and less than 3 epoxlde groups per molecule with (2) a divalent phenolic compound which contains on average more than 1 and ess than 3 phenollc hydroxyl groups per molecule WO 95tlO556 2 15 1 7 ~ ~ PCT/US9~/11349 ~

characterized in that the reaction takes place in the presence of a giycolether solvent having no primary hydroxyl groups.
The present invention is particularly described below.
The epoxy resin (hereinaft'er bifunctional epoxy resin) to be used m the present5 invention includes any compound substantially having an average of more than 1 and less than 3 epoxide groups per molecule. The average number of epoxide groups per molecule is preferably more than 1.8 and less than 3, more preferably less than 2 1, and most preferably about 2. The bifunctional epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, bisphenol S type epoxy resins, alicyclic epoxy resins, aliphatic linear type epoxy resms, diglycidyl ethers of divaler~t phenols, diglycidyl ethers of divalent alcohols, halides thereof, hydrogenated thereof and the like. Sald epoxy resins may be used individually, or as any combination thereof. Among said epoxy resins, the preferable epoxy resi ns i ncl ude bisphenol A type epoxy resi ns and bisphenol F type epoxy resins. Additionally, the reaction mixture may further contain an additional epoxy component other than the bifunctional epoxy resin, such as a minor arnount of epoxy novolac resin, as long as a resultant product has desired properties.
An epoxy resin as a raw material of the present invention is, without intending to be limited, usually a relatively low molecular weight epoxy resin. The bifunctional epoxy resin preferably has an epoxy equivalent weight of 170-400 and more preferably 175-250. It 20 preferably has a number average molecular weight of 340-1000 and more preferably 350-500.
In the present invention, for example, D.E.R. '~ 331 L, D.E.R.~ 383J, D.E.R."' 661 (Trademarks of The Dow Chemical Company) may be used as commercialized epoxy resins.
The divalent phenols in the present invention are used as a chain extender for the polymerization of the epoxy resin, and may be any of phenol compounds having on average 25 more than 1 and less than 3 phenolic hydroxyl groups, preferably havlng on average 1.8 to 2.1 phenolic hydroxyl groups, most preferably substantially about two phenolic hydroxyl groups.
The divalent phenols include, for example, monocyclic divalent phenols such as hydroquinone, resorcinol and catechol, polycyclic divalent phenols such as bisphenol A, bisphenoi F, bisphenol AD, bisphenol S, halogenated versions thereof, alkyl substituted versions thereof and~he like.
30 The above-mentioned compounds are used individually, or as any combination thereof Among the above-mentioned divalent phenols, the preferable phenols used in the present invention are bisphenol A, and bisphenol F. Additionally, the reaction mlxture may further contai n a phenol component other than the divalent phenols, such as a novolac res; n or a triphenol resln, as long as a resultant product has desired properties.
The equlvalent ratio of epoxide group: phenolic hydroxyl group is usually 0.7 to1.4: 1 and preferably O 9 to 1.1: 1 If the equivalent ratio is less than 0.7, or more than 1.4, the imbalance in stoichiornetry may redl~ce the molecular weight achieved during advancement.

~C)WO 95/10556 2 1 51 7 ~ 5 PCT/US94/11349 In the present invention, the solvent contains glycolethers having no primary hydroxyl groups, i.e. hydroxyl groups bonded to a primary carbon atom. The glycolethers include propyleneglycol ethers having a hydroxyl in ~3-position. The propyleneglycol ethers in the present invention are able to dissolve raw materials such as the epoxy resins and the 5 phenols, and include, for example, propyleneglycol methylether, propyleneglycolmethylether acetate, propyleneglycol propylether, propyleneglycol monobutylether and the like The preferable propyleneglycol ether is propyleneglycol monobutylether The glycol ether solvent preferably has a boiling point higher than 140C and morepreferablyhigherthanl65C. Themaximumboilingpointisnotcritical,butitis 10 preferably no higher than 300C For the purpose of dissolving the advanced resin, another solvent, for example, such as ketone solvents, amide solvents, ether solvents or aromatic solvents may be added after the advancement is completed.
The solvent content is preferably 10% to 50% of the reaction mixture, and, more preferably 20% to 40% of the reaction mixture. If the solvent content is less than 10%, the viscosity of the resin may quickly build to high for effective agitation. On the other hand, lf the solvent content is more than 50%, the reaction rate may be too slow.
The polymerization of the present invention is preferably carried out using a catalyst. The catalysts include, for example, imidazoles such as 2-methyl imidazole, tertiary amines such as triethyl amine, tripropyl amine and tributyl amine, phosphonium salts such as 20 ethyltriphenylphosphonium chloride, ethyltriphenylphosphonium bromide and ethyltriphenylphosphonium acetate, ammonium salts such as benzyltrimethylammonium chloride and benzyltrimethylammonium hydroxide. Suitable catalysts for the present invention are highly active catalysts capable to be used in higher temperature, preferably phosphorous catalysts, especially phosphonium salts such as ethyltriphenylphosphonium 25 acetate. The catalyst concentration is preferably 0.001 to 10 percent by weight, and more preferably 0.01 to 5 percent by weight, based on the reactant solids. If the advanced epoxy resin is intended for food can coating applications, the concentration of the catalyst is most preferably less than 0.25 percents by weight.
In the present invention, the polymerization reaction is carried out at a rather30 high temperature which is lower than both of the boiling point of the polymerization solvent and the decomposition temperature of the polyrnerization catalyst. The temperatu~e of the advancement reaction is preferably 100 to 250C and more preferably at 120 to 200C. The reaction time is preferably 1 to 12 hours and more preferably 3 to 7 hours Tne polymerization reaction may be carried out by a continuous process or a batch process, under atmospheric 35 pressure, higher pressure or reduced pressure.
The advanced epoxy resin made by the process of the present inventior preferably has a weight average molecular weight of 20,000 to 200,000, and more preferably 50,000 to 150,000 The molecular we~ght aistribu~lon ~Mv~,~Mn) of the advanced resi n ~s W0 95/10556 2 ~ 5 PCT/US94/11349 0 preferably 2 to 15 and more preferably 4 to 11. Furthermore, the process of the present invention can be used, under preferred conditions and using preferred reagents, to produce an epoxy resin having more than 50,000 (and preferably more than 70,000) weight average moiecular weight in 3 to 7 hours.
The high molecular weight epoxy resin produced by the process of the present invention may be used as adhesives, insulating materials, moldings solution and powder coatings and the like, and preferably used as paints, more preferably used as paints for metal can coating.
EXAMPLES
The present invention is particularly illustrated by the following examples. In the examples, "parts" means''partsbyweightU.

Examples 1-2 and Comparative Examples A-D:
A series of reaction mixtures were made which contained the following components:
(1) aliquidepoxyresinwithanepoxyequivalentweightofabout180,inthe quantities shown in Table 1;
(2) bisphenol A in the quantities shown in Table 1;
(3) aboutO.18%(basedonsolidresin)ofethyltriphenylphosphoniumphosphateas catalyst; and 20 (4) the solvent and quantity of solvent shown in Table 1 Each mixture was reacted for 4 or 7 hours at about 170C. A sample of the resulting advanced resin was recovered, and its weight average molecular weight was measured by gel permeation chromatography using polystyrene standards. The results are shown in Table 1. The Comparative Examples are not examples of the present invention ~ W09S/lOSS6 PCT/US94/11349 215~7~5 .., . o o ~ o ~ o o o o ~ Lo~ u~ o o L

.~ I~ o ~ o o o 0 G ~ m o r~
L

~ O -- Lf) ~ ~ ~ o -- Ln L

a~
~ ' E ~ ~ o 0 o o ": ~ Ln ~D.

_ ~ o ~ o o E ~ D o -- ,~ o ~ LX

~ ~o o -- I` ~ I
LX

E L E o ,~ ou WO 9S/lOS56 2~ 5 PCT/US9~/11349 Abbreviation in Table 1 shows the following compound respectiveiy LER: Bisphenol A type epoxy resin BIS-A: Bisphenol A
PnB: Propyleneglycol monobutylether ETPPA: Ethyltriphenylphosphonium acetate ETPPP: Ethyltriphenylphosphonium phosphate EVALUATION RESULT
Comparing Example 1 with Comparative Example A-C, the high molecular weight 10 polymerizationto 129~oooofawei9htavera9emolecularwei9htwasavailableby4-hour polymerization according to the process of the present invention. However, in the polymerization carried out at substantially the same conditions except the solvent used in Comparative Example A-C, the high molecular weight polymerization only to 45,000-56,000 of a wei ght average mol ecu lar weig ht was avai labl e. Therefore, it was fou nd that the present invention remarkably enables to a high molecular weight polymerization at the same condition as known process.
Comparing the result of Example 2 with Comparative Example D, Example 2 achieved an about 3-time high molecular weight polymerization in weight average molecular weight, comparing to Comparative Example D, at substantially the same conditions even 20 though the reaction activity was decreased because of the use of ethyltriphenylphosphonium phosphate as polymenzation catalyst. Therefore, it was found that the present inventlon remarkably enables to a high molecular weight polymerization in the same conditions as known process.
As described above, according to the process of the present invention, a higher 25 molecular weight epoxy resln can be produced in shorter time comparing to a prior process using the currently used polymerization solvent.

Claims

WHAT IS CLAIMED IS:

1. A process for producing a high molecular weight epoxy resin by reacting.
(1 ) an epoxy resin which contains on average more than 1 and less than 3 epoxide groups per molecule with (2) a divalent phenolic compound which contains on average more than 1 and less than 3 phenolic hydroxyl groups per molecule characterized in that the reaction takes place in the presence of a glycolether solvent having no primary hydroxyl group 2. The process according to Claim 1 wherein the glycolether is a propyleneglycolether.
3. The process according to Claim 2 wherein the glycolether is a propyleneglycolmonobutylether.
4. The process according to any of Claim 1 to 3 wherein the reaction is carried out in the presence of a catalyst.
5. The process according to any of Claim 1 to 3 wherein the reaction is carried out in the presence of a phosphorous compound as a catalyst.
6. The process according to any of Claim 1 to 3 wherein the reaction is carried out at a temperature of 120-200°C.
7. The process according to any of Claim 1 to 3 wherein the reaction is carried out at a temperature of 120-200°C in the presence of a catalyst.
8. The process according to any of Claim 1 to 3 wherein the reaction is carried out at a temperature of 120-200°C in the presenee of a phosphorous compound as a catalyst.
9. A high molecular weight epoxy resin produced by the process according to

Claim 1.