CA1085418A - Latent catalysts for promoting reaction of expoxides with phenols and/or carboxylic acids - Google Patents

ABSTRACT

This invention concerns a process comprising reaction of a vicinal epoxide with a phenolic compound, a carboxylic acid, or a carboxylic acid anhydride in presence of a catalyst corresponding to the formula wherein each R is a C1-20 aliphatic hydrocarbyl rad-ical, R' is hydrogen or a C1-20 hydrocarbyl radical, R" represents hydrogen, C1-20 alkyl, or C1-20 alkoxy-carbonyl, and n is 0 to 20. The invention also concerns a composition comprising an epoxy resin containing an average of ore than one vicinal epoxy group par molecule and a catalyst as defined above. These catalysts are effective for selectively promoting the desired reac-tions to give high yield of products generally having excellent color. They are especially useful when pro-duction of high molecular weight products is desired.
The catalysts are substantially unreactive with epoxy resins at ambient temperatures and axe thus useful for preparation of precatalzed epoxy resin compositions.

10~5418 This invention pertains to a proce~s for - reaction of vicinal epoxides and phenols, carboxylic acids, or anhydrides of such acids, and an epoxy resin composition. Such reactions are commercially important in that functional monomers (e.g. hydroxy-ethyl acrylate), hydraulic fluids (e.g. 2-phenoxy-ethanol~ and high molecular weight linear or cross--linked epoxy resins are thus produced.
The reactions between epoxides and phenols, carboxylic acids or anhydrides in presence of cata-lysts are known.
It is known that (1) a catalyst is required to attain a satisfactory reaction rate and (2) those skilled in the art recognize that the reaction be-tween epoxides and phenols is not, mechanistically speaking, the same as the reaction between epoxides and carboxylic acids (or anhydrides) due to the dif-~, ferences in products. Substantially linear polymers are produced by reacting epoxy resins with poly-functional phenols in the presence of a catalyst, whereas cross-linked polymers are produced by re-acting the same epoxy resins with a polycarboxylic acid tor anhydride) in the presence of the same catalysts. The reactive species which catalyzes the reaction is therefore believed to be differ-~` ent in each instance. Thus, compounds which cata-lyze one reaction would not necessarily be expec-ted to catalyze the other.
Several problems have been encountered in using many of the prior art catalysts. In many ~' ~

16,973~-F -1-, 1~5~

; instances, the catalysts react with the epoxy reac-tant and thus ~reclude the option of marketing a blend comprising an epoxy resin and a catalyst;
this blend is commonly referred to as a "precata-lyzed epoxy resin". In other instances, the p~ob-; lem associated with the prior art catalysts is selectivity; i.e. the catalysts simultaneously promote the reaction between the epoxy reactant and the phenolic hydroxyl group (or acid group) on the reactant and the aliphatic hydroxyl group(s) on the product giving branched or cross-linked polymers rather than the desired linear polymers.
In still other instances, the reaction rate is un-; satisfactory and/or the product is highly colored ;~ 15 and therefore unsatisfactory for many uses and/or the product was contaminated with corrosive anions ; (e.g. chloride) and is therefore unacceptable for electrical encapsulation (potting).
Canadian Patent No. 893,191 discloses the use of triphenyl(2-carboxyethyl)phosphonium hydroxide ~ inner salt as catalyst for reaction of epoxides with ; phenols.
The present invention provides the process which comprises reacting (a) a vicinal epoxide with (b) a phenolic compound, a carboxylic acid, a car-boxylic acid anhydride, or a mixture thereof in the presence of a catalyst corresponding to the formula (R)3P -CH(CHR')nCOO~
R"

"

16,973B-F -2-10~ L8 ..
.
wherein each R represents an alkyl radical containing from 1 to 6 carbon atoms, R' and R" represent hydrogen atoms and n represents 0, 1 or 2.
The catalysts most preferred are tri-n-butyl(2-carboxymethyl)phosphonium ( hydroxide inner salt and the corresponding (2-carboxyethyl) compound.
This invention further provides an epoxy resin composition which comprises an epoxy resin con-taining an average of more than one vicinal epoxy group per molecule and a catalyst as defined above.
' The catalysts concerned herein are effective in selectively ,~ catalyzing the desired reaction, and the products are obtained in high yields and are of generally excellent color.
The catalysts also are unreactive with epoxy resins at conventional storage temperatures. As a result, precatalyzed epoxy resins can be produced by merely blending the catalysts with the epoxy resins.
' In addition, it has been found that use of the present catalysts for reaction of epoxy resins with phenols can produce surprisingly higher molecular weight products than can be obtained using the triphenyl(2-carboxyethyl)phosphonium hydroxide inner salt disclosed in the above Canadian patent.

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The above catalys~s are particularly use-ful in catalyzing the reaction between vicinal epo-xides and phenols, carboxylic acids, or anhydrides.
In this utility, the amount used can be varied over a wide range. Generally, however, they are used in a small but catalytic amount, as for example in amounts of from 0.001 to 10 percent by weight, based on the combined weight of reactants. Preferably, the cata-' lyst is included in amounts of from 0.05 to 5 percent by weight.
As stated above, the reactants used are well known classes of compounds.
The vicinal epoxides, for example, are organic compounds bearing one or more vicinal epoxy groups. The alkylene oxides of from 2 to 24 carbon , atoms, the epihalohydrins, and the epoxy resins are ~ perhaps the best known and most widely used members t of the genus. Ethylene oxide, propylene oxide, 1,2--butylene oxide, and epichlorohydrin are the preferred ` 20 monoepoxid~s. There are two preferred subclasses of r epoxy resins. The first subclass corresponds to the ~r general formula ~i --CH2CHCH2 O--CH2CHCH~ O--CH2CHCH2 ~ ~ CH2 _ ~ _ CH2 ~
~,'' _ _ n wherein R is hydrogen or an alkyl radical and n is from 0.1 to 10, preferably from 1 to 2. The second subclass corresponds to the general formula i 16,973B-F -4-., .

~5~18 CH2-CH-CH2-O- ~ -A- ~ >-O-CH2-C~I-CH2 R2 Rl wherein R~ Rl, R2 and R3 are independently selected from hydrogen, bromine and chlorine and wherein A is an alkylene (e.g. methylene) or alkylidene (e.g. iso-propylidene) group having from 1 to 4 carbon atoms, O O O
.. .. ..
-S-, -S-S-, -S-, -S-, -C-, or -O-.
.. ..
''' 10 ` The phenols are organic compounds having s one or more hydroxyl groups attached to an aromatic .~ nucleus. This class of compounds thererore includes ~ phenol, alpha- and beta-naphthol, o-, m-, or p-chloro-; 15 phenol, alkylated derivatives of phenol (e.g. o-methyl-, 3,5-dimethyl-, p-t-butyl-, and E~nonylphenol), and other monohydric phenols as well as polyhydric phenols, such as resorcinol or hydroquinone. The polyhydric phenols bearing from 2 to 6 hydroxyl groups and having from 6 to 30 carbon atoms are particularly useful in the re-action with epoxy resins to form high molecular weight resins (linear or cross-linked) useful in coatings.
Particularly preferred polyhydric phenols are those corresponding to the formula R R R R
; 25 ~ ~
HO - ~ - X- ~ - OH

R R R

wherein R is hydrogen, halogen (fluoro, chloro or bromo), or hydrocarbyl, and X is selected from oxygen, 16,973B-F -5-sulfur, -SO-, -So2-, bivalent hydrocarbon radicals containing up to 10 carbon atoms, and oxygen, sulfur and nitrogen-containing hydrocarbon radicals, such as -OR'O-, -OR'OR'O-, -S-R'-S-, -S-R'-S-R'-S-, -OSiO-, . o o o o O o ,1 ,. .. .. .. ..
-oSiOSio-, -O-C-R'-C-O-, -C-O-R'-O-C-, -S-R'-S-, or -SO2-R'-SO2- radicals wherein R' is a bivalent hydro-carbon radical. 4,4'-Isopropylidenediphenol (i.e.
bisphenol A) is the most preferred phenol.
The organic carboxylic acids and anhydrides are likewise well known. The acids bear one or more carboxyl groups on the organic nucleus. The anhy-drides are prepared from such carboxylic acids by the removal of water therefrom in an intra- or inter-molecular condensation. This class of compounds therefore includes acetic, propionic, octanoic, ~ stearic, acrylic, methacrylic, oleic, benzoic, ph-i thalic, isophthalic, maleic, succinic, adipic, ita-conic, polyacrylic and polymethacrylic acids, and anhydrides thereof, such as acetic anhydride, phtha-lic anhydride, or hexahydrophthalic anhydride.
There are two subclasses of carboxylic acids and anhydrides that are particularly import-; ant based on their reaction with epoxy resins.
' 25 The reaction of ethylenically unsaturated monocarboxylic acids with epoxy resins produces 1: ~
hydroxy-substituted esters or polyesters which are particularly useful in the preparation of coatings ; or adhesives. Acrylic and methacrylic acid are ., .
16,973B-F -6-~..

; particularly useful in this reqard. Accordingly, the ethylenically unsaturated monocarboxylic acids are a preferred subclass of acids.
The second preferred subclass of acids is comprised of members which are useful in cross-link-ing epoxy resins. The members of this subclass are normally di- or tribasic acids, or anhydrides thereof, and are preferably liquid or low-melting solids, such as succinic, maleic or hexahydrophathalic acid or anhydrlde.
The ratio of vicinal epoxide reactant to phenol, carboxylic acid, or anhydride reactant can vary ovex a wide range depending upon the product desired. For example, if a product terminated with a phenolic ether group is desired, ob~iously one would employ an excess of phenol in the process, etc.
In many instances the reactants are liquid and no solvent or diluent is needed. In other cases, how-ever, where one or both of the reactants are solid or viscous liquids, an inert solvent or diluent can be used advantageously. Suitable such inert solven~s or diluents are known to those skilled in the art and include ketones (such as acetone or methyl ethyl ke-tone), and hydrocarbons (such as benzene, toluene, xylene, cyclohexane, or ligroin~.
Generally, the reaction mixture is warmed at temperatures in the range of from 50C to 225C
(preferably 100-175C) until an exotherm begins and, 16,973B-F -7-~ 5~18 ., after the exotherm has peaked, substantially warmed in the same range for an additional time to assure , substantially complete reaction. Atmospheric or superatmospheric pressures (e.g. up to about 200 psig, 14 kg./cm.2 gauge) are common.
The products are generally known compounds in industry. The particular product produced will vary in properties depending upon the selection and ratio of reactants used in the process. The fol-~, 10 lowing discussion will illustrate the types of products which can be produced.
The products produced by reacting an epoxy resin with a phenol in the presence of the catalysts are phenolic ethers bearing one or more aliphatic secondary hydroxyl groups. Such aliphatic hydroxyl groups are formed in the ring-opening reaction be-tween the epoxy and phenolic hydroxyl groups. Ad-~ ditionally, the reaction products bear a terminal i epoxy group~s) or a phenolic hydroxyl group (5) de-pending upon the ratio of reactants. Consequently, they are reactive intermediates which can be cured (cross-linked) with many polyfunctional curing agents to form hard, insoluble solids which are useful coat-ings. The cured products (particularly those of high molecular weight) are useful as surface coatings, adhesive layers in laminates, coatings on filament windings, or in structural binding applications.
The products prepared from halogenated (particu-larly brominated) phenols are particularly useful .

16,973B-F -8-..

in flameproofing applications, since they tend to be self-extinguishing. Thus, they are useful in forming cured coatings for wood paneling and as , adhesive layers in wood laminates~
~he products produced by reacting an epoxy resin with a monocarboxylic acid (or anhydride of such acid) have terminal ester groups and are use-ful in coatings, adhesives, reinforced plastics, or moldings. The products formed by reacting epoxy resins with polycarboxylic acids, or anhydrides thereof, are cross-linked, insoluble resins use-ful in coatings.
Functional monomers can be produced by reacting a C2 to C4 alkylene oxide with acrylic or methacrylic acid. Hydraulic fluids can be pre-; pared by reacting a lower alkylene oxide with a i phenol in substantially equimolar amounts. Non-ionic surfactants can be prepared by reacting an alkylated monohydric phenol with a C2 to C4 alkyl-ene oxide, or mixture of such alkylene oxides.
Other useful products can be similarly prepared by the reaction of vicinal epoxides with `~ phenols and/or carboxylic acids (or anhydrides) in the presence of the catalysts.
The catalysts wherein R" is hydrogen can be prepared from a compound corresponding to the formula ; (R)3P -CH(CHR')nCOOH

by heating to a temperature sufficient for decarboxyla-tion. For example, heating 116 g. of tri-n-butyl(1,2--dicarboxyethyl)phosphonium hydroxide inner salt at ' .

16,973B-F -9-1~5418 70C under a vacu~ of 0.1 mm. ~Ig for about 15 hours gave 100 g. of tri-n-butyl(2-carboxyethyl)phosphonium ; hydroxide inner salt, a white, hygroscopic, crystal-line solid melting at 175-177C.
%C ~rI %p ;~, Calculated 65.66 11.39 11.29 Found 65.97 11.48 10.93 The catalysts also can be prepared by treating a phosphonium chloride corresponding to the formula ,~ (R)3P -CH(CHR')nCOOH C1 , Rn r with a strong base anion exchange resin in methanol.
!'~ The phosphonium chloride can be prepared by reaction '~ 15 of a tertiary phosphine of the formula (R)3P with an appropriate omega~chloroalkanoic acid.
, Alternatively, the compounds can be prepared by reacting an appropriate phosphine with a chloro- or , bromo-substituted carboxylic acid followed by treatrnent with a base.
~ ;.
The following examples illustrate the in-vention.
Example 1 Tri-n-butyl(2-carboxyethyl)phosphoni~n hydroxide inner salt was added at a 0.15 weight per-cent catalyst concentration to an aliquot of a mix-ture consisting of a liquid epoxy resin (100 parts by weight) having an EEW of 172-176 and hexahydro-phthalic anhydride (80 parts by weight). The ~ ~, 1., 1.,, .~
, 16,973B-F -10 10~5 :.
catalyzed mixture was formed by preheating the epoxy re3in and anhydride components separately to 70C
and then blending such components and the particu-lar catalyst with efficient stirring. The catalyzed mixture was degassed under vacuum. Gel time at 110C
was le~s than one hour. The remainder of the cata-lyzed mixture was poured into a mold and heated 2 hours at 110C and 2 hours at 150C thus producing a colorless, cross-linked sheet casting having the following properties.
Tensile yield strength 12500 psi (875 kg./cm. ) (ASTM D638-68) Flexural strength 21800 psi (1526 kg./cm.2) (ASTM D-790) % Elongation 4.8 (ASTM D638-68) Other species of the present catalysts can be similarly used. In addition, the above anhydride can be replaced with other anhydrides of organic car-boxylic or polycarboxylic acids as defined above. For example, maleic anhydride could be used in the above reaction leading to cross-linked products. Alter-natively, acrylic or methacrylic acid could be used in the above reaction leading to epoxy resins termi-nated with a free-radical or thermally polymerizable vinyl groups. Such compounds ~re likewise useful coating material.
Ex~mple 2 Phenol and ethylene oxide (1.05 mole/mole of phenol) were charged to a reaction vessel under ; sufficient pressure to maintain the reactants in ; substantially liquid phase at 150C. To this was . . .
16,973B-F -11-:.

5'~18 added 0.1 weight percent of tri-n-butyl(2-carboxy-ethyl)phosphonium hydroxide inner salt and the re-action mixture heated with stirring for 3.5 hours ~ at 150C. m e reaction mixture was cooled and the ; 5 volatiles removed under vacuum. The liquid residue by analysi~ contained 89.9 weight percent 2-phenoxy-ethanol and 6.7 weight percent 2-(2-phenoxyethoxy)-ethanol. Conversion of phenol was 97.6%.
' Example 3 Acrylic acid (1.8 g.; 0.025 m~le), E~t-l, -butylphenyl glycidyl ether (5.15 g.; 0.025 mole) ; and 0.15 weight percent (10.4 milligrams~ of tri-¦` -n-butyl(2-carboxyethyl)phosphonium hydroxide inner salt were mixed in a reaction vessel and heated at 110-120C for 5.5 hours. The extent of the reac-tion was measured by titration for unreacted acid and the product identified by IR analysis. The desired product, C4Hg-C6H4~OCH2CH(OH)CH2O~C(O)CHsCH2, was obtained in about 97 percent yield, based on theory.

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1 16,973B-F -12-

1. The process which comprises reacting (a) a vicinal epoxide with (b) a phenolic compound, a carboxylic acid, a carboxylic acid anhydride, or mixture thereof in the presence of a catalyst corresponding to the formula wherein each R represents an alkyl radical containing from 1 to 6 carbon atoms, R' and R" represent hydrogen atoms and n represents 0, 1 or 2.

2. The process claimed in claim 1 wherein the catalyst is tri-n-butyl (2-carboxyethyl)phosphonium hydroxide inner salt or tri-n-butyl(2-carboxy-methyl)phosphonium hydroxide inner salt.

3. The process claimed in claim 1 or 2 wherein the catalyst is employed in an amount of from 0.001 to 10 percent by weight based on the combined weight of the reactants.

4. The process claimed in Claim 2 wherein the catalyst is employed in an amount of from 0.05 to 5 weight percent based on the combined weight of the reactants.

5. The process claimed in Claim 1 wherein the reaction is carried out at a temperature within the range of from 50 to 225°C.

6. The process claimed in Claim 4 wherein the reaction is carried out at a temperature within the range of from 100 to 175°C.

7. The process claimed in Claim 1 wherein the epoxide is an epoxy resin containing an average of more than one vicianl epoxy group per molecule.

8. The process claimed in Claim 7 wherein the epoxy resin is a liquid product from reaction of bisphenol A with an epihalohydrin.

9. The process claimed in Claim 8 wherein reactant (b) is bisphenol A.

10. An epoxy resin composition which comprises an epoxy resin containing an average of more than one vicinal epoxy group per molecule and a catalyst for re-action of the epoxy resin with a phenolic compound, a carboxylic acid, or a carboxylic acid anhydride, said catalyst being a phosphonium hydroxide inner salt corresponding to the formula wherein each R represents an alkyl radical containing from 1 to 6 carbon atoms, R' and R" represent hydrogen atoms and n represents 0, 1 or 2.

11. A composition as claimed in claim 10 wherein the catalyst is tri-n-butyl(2-carboxyethyl)-phosphonium hydroxide inner salt or tri-n-butyl (2-carboxymethyl)phosphonium hydroxide inner salt.

12. A composition as claimed in claim 11 wherein the epoxy resin is a product from reaction of bisphenol A with an epihalohydrin.

13. A composition as claimed in claim 10 which contains, in addition, a phenolic compound, a carboxylic acid, or a carboxylic acid anhydride.

14. A composition as claimed in Claim 12 which contains, in addition, bisphenol A.

15. A composition as claimed in Claim 13 or 14 wherein the catalyst is present in an amount of from 0.001 to 10 percent by weight based on the combined weight of the other named components.

16. A composition as claimed in Claim 13 or 14 wherein the catalyst is present in an amount of from 0.05 to 5 percent by weight based on the combined weight of the other named components.