WO2001021687A1

WO2001021687A1 - Solvent composition

Info

Publication number: WO2001021687A1
Application number: PCT/US2000/024915
Authority: WO
Inventors: Martin F. Hill; Rene R. Blank; Alan R. Goodson; Manuela Ehreiser
Original assignee: The Dow Chemical Company
Priority date: 1999-09-23
Filing date: 2000-09-08
Publication date: 2001-03-29
Also published as: KR20020033191A; AU7370500A; EP1230293A1; CN1373785A; JP2003510388A

Abstract

A solvent composition which comprises a) a glycol monoether or diether, b) a protic liquid other than a glycol monoether or diether; and c) an organic liquid containing an amide or carboxyl group, is particularly useful as a diluent for epoxy resins, curing agents for an epoxy resin, curing catalysts, and/or cure inhibitors.

Description

SOLVENT COMPOSITION

The present invention relates to a solvent composition and to the use of the solvent composition as a diluent for one or more epoxy resins and/or one or more curing agents for epoxy resins and/or one or more curing catalysts and/or one or more cure inhibitors .

Background of the Invention

It is a well known technique to utilize an organic solvent for reducing the viscosity of liquid epoxy resins or liquid curing agents therefor or to solubilize solid resins and/or curing agents in organic solvents in order to facilitate the handling of the epoxy resins and/or of the curing agents.

Excellent solvents for curing agents for epoxy resins, such as dicyandiamide, are dimethyl formamide and methyl glycol. However, the use of dimethyl formamide or methyl glycol has raised industrial hygiene concerns.

Accordingly, one object of the present invention is to find new solvents which are useful for dissolving epoxy resins, curing agents for epoxy resins, curing catalysts or cure inhibitors or which are useful for reducing the viscosity of such compounds.

Known uses of epoxy resins are among others the production of electrical laminates, glass laminates and coatings. In a typical procedure a solution of an epoxy resin in an organic solvent, such as a ketone, and a solution of a curing agent for an epoxy resin, such as dicyandiamide, are combined to produce an epoxy resin composition which is used in various applications. When using known solvents for dicyandiamide, such as propylene glycol monomethyl ether, often difficulties have been experienced in keeping dicyandiamide in solution after the dicyandiamide solution has been mixed with the epoxy resin solution.

Accordingly, a preferred object of the present invention is to find new solvents in which curing agents for an epoxy resin, such as dicyandiamide, are sufficiently soluble even after the curing agent solution has been mixed with an epoxy resin solution.

Summary of the Invention

One aspect of the present invention is a solvent composition which comprises:

a) a glycol monoether or diether and

b) an organic low molecular weight compound containing a carbonate group.

Another aspect of the present invention is a composition which comprises one or more compounds selected from i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors in a solvent composition indicated above.

Yet another aspect of the present invention is a method of preparing a composition comprising one or more compounds selected from i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors, in a solvent composition by contacting one or more such compounds with

a) a glycol monoether or diether and

b) an organic low molecular weight compound containing a carbonate group.

Yet another aspect of the present invention is the use of a) a glycol monoether or diether and b) an organic low molecular weight compound containing a carbonate group as a diluent for one or more compounds selected from i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors.

Detailed Description of the Invention

The solvent composition of the present invention preferably comprises a) at least 45 percent, preferably at least 50 percent, more preferably at least 60 percent, and most preferably from 60 to 90 percent, of a glycol monoether or diether; and

b) from 1 to 30 percent, preferably from 1 to 25 percent, more preferably from 1 to 20 percent, most preferably from 5 to 15 percent, of an organic low molecular weight compound containing a carbonate group and; optionally

c) up to 25 percent, preferably up to 20 percent, more preferably from 2 to 15 percent, most preferably from 5 to 12 percent, of a protic liquid other than a glycol monoether or diether, based on the total weight of a) , b) and c) .

Component a) of the solvent composition is a glycol monoether or a glycol diether or a mixture of one or more monoethers and/or diethers. The monoethers are preferred over the diethers.

Preferred glycol monoethers are the propylene or butylene glycol monoethers, most preferably ethers represented by Formula I

RiO - (CH₂ - CHR³0)_n - R₂ (I)

wherein

one of the substituents R_x and R₂ is an alkyl group having from 1 to 12, preferably from 1 to 6 , more preferably from 1 to 4 carbon atoms and the other of the substituents R_ and R₂ is hydrogen,

R³ in each occurrence independently is ethyl or, preferably, methyl and

n is from 1 to 4, preferably 1, 2 or 3.

The alkyl groups may be branched or unbranched. Exemplary of the alkyl groups are methyl, ethyl, n-propyl, isopropyl, the butyl groups, such as n-butyl or isobutyl, and the pentyl , hexyl, octyl , decyl or dodecyl groups . Of the propyl and butyl groups n- propyl and n-butyl are preferred. Preferably, one of the substituents R_ and R₂ is methyl or n-butyl. Preferred monoethers of Formula I are propylene glycol n-butyl ether, dipropylene glycol methyl ether, dipropylene glycol n-butyl ether and, most preferably, propylene glycol methyl ether.

The corresponding propylene or butylene glycol diethers wherein both substituents R_x and R₂ are an alkyl group are also useful .

Component b) of the solvent composition is an organic low molecular weight compound containing a carbonate group. By the term "low molecular weight" as used herein is meant a molecular weight of up to 200, preferably of up to 150, most preferably up to 120. A useful component b) is for example ethylene carbonate or butylene carbonate. The preferred component b) is propylene carbonate.

The optional component c) of the solvent composition is a protic liquid, other than a glycol monoether or diether, or a mixture of two or more such protic liquids. By "liquid" is meant a compound that is liquid at room temperature and atmospheric pressure. The most preferred protic liquid is water. Other protic liquids are alcohols or glycols, such as methanol, ethanol, ethylene glycol or propylene glycol .

If component b) of the solvent composition is propylene carbonate or butylene carbonate, it is advisable to include component c) , preferably water, in the solvent composition of the present invention. If component b) of the solvent composition is ethylene carbonate, the solvent composition is an excellent solvent for a curing agent, such as dicyandiamide, with or without component c) .

Depending on the intended use of the solvent composition of the present invention, it preferably contains one or more other solvents in addition to components a) , b) and c) , preferably ketones, such as acetone, methyl ethyl ketone or methyl isobutyl ketone; or amides, such as dimethyl formamide. Their amount also depends on the intended use of the solvent composition.

If the solvent composition of the present invention is used for diluting an epoxy resin, the total amount of the components a) , b) and c) generally amounts to at least 40 percent, preferably at least 50 percent, more preferably at least 60 percent and the amount of one or more other solvents is generally up to 60 percent, preferably up to 50 percent, more preferably up to 40 percent, based on the total weight of the solvents in the solvent composition.

If the solvent composition is used as a diluent for a curing agent for an epoxy resin, a curing catalyst or a cure inhibitor, the total amount of the components a) , b) and c) generally amounts to at least 60 percent, preferably at least 75 percent, more preferably at least 90 percent and the amount of one or more other solvents is generally up to 40 percent, preferably up to 25 percent, more preferably up to 10 percent, based on the total weight of the solvents in the solvent composition.

Most preferably, the solvent composition of the present invention substantially consists of the components a) , b) and c) .

The solvent composition may comprise other additives, such as viscosity modifiers, for example N-methyl pyrrolidone, thickeners, for example high molecular weight polyalkylene glycols, or plasticizers, for example dioctyl phthalate or chlorinated paraffin. If present, their amount preferably is from 0.1 to 20 percent, more preferably from 1 to 10 percent, based on the total weight of components a) , b) and c) .

The solvent composition of the present invention may comprise solid particles, such as a filler. However, the solvent composition does not comprise more than 150 percent, preferably not more than 100 percent of solid particles, based on the total weight of components a) , b) and c) . Useful fillers include organic and inorganic fillers, such as melamin resins, wood fillers, carbon black or graphite, talc, calcium carbonate, phosphates, such as ammonium polyphosphate, flyash, aluminium trihydroxide, magnesium hydroxide, glass fibers, marble dust, cement dust, clay, feldspar, silica or glass, fumed silica, alumina, magnesium oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium dioxide, titanates, glass microspheres or chalk. Useful fire retardant fillers and additives, such as sulfur compounds, phosphorus compounds, boron compounds, silicon compounds and polynuclear aromatic compounds are for example described in "International Plastics Flammability Handbook" by Jϋrgen Troitzach, 1983, ISBN 0-02-949770-1 Macmillan Publishing Co., Inc., New York pages 46 to 53 and "Ullmann's Encyclopedia of Industrial Chemistry" Vol. All pages 124 to 126.

The solvent composition of the present invention can be produced in a known manner. Generally the components of the solvent composition are mixed in the ratios indicated above at a temperature of from 1°C to 80°C, preferably from 15°C to 40°C, until a homogeneous mixture is obtained.

The solvent composition of the present invention is very useful as a diluent for one or more compounds selected from i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors. The diluent can act as a means for reducing the viscosity of one or more liquid compounds or as a solvent .

Preferably, a curing agent for an epoxy resin, optionally a curing catalyst and optionally a cure inhibitor is diluted with the solvent composition of the present invention. This blend is preferably mixed with an epoxy resin which is diluted with an organic solvent.

Curing agents for epoxy resins, commonly also called epoxy hardeners, are well known in the art. Useful classes of curing agents are for example amides, acid anhydrides, such as styrene/maleic anhydrides, boron trifluoride complexes, dicyandiamide, substituted dicyandiamides, polyester resins, novolacs or phenolic hardeners, that is compounds containing more than one aromatic hydroxyl group. Another class of curing agents well known in the art comprises prereacted adducts of epoxy resins with amines or anhydrides or dicyandiamide or phenolic resins. Preferred phenolic hardeners are described on pages 6 to 8 of European patent specification 0,240,565. Other known curing agents are primary or secondary amines, hydrazides or hydrazine, preferably the multifunctional, more preferably the di- to hexafunctional primary amines, amides and hydrazides. Such curing agents are listed in column 5, lines 47 to 68 and column 6, lines 14 to 19 of U.S. Patent 4,789,690.

Further useful curing agents are listed on page 11, lines 41-58 and page 12, lines 1-40 of the published European patent application EP-A-0 , 458 , 502. Other preferred curing agents are derivatives of cyanamide or dicyanamide, dihydroxy phenols, biphenols, halogenated bisphenols, alkylated bisphenols, trisphenols, phenol-aldehyde resins, halogenated phenol-aldehyde novolac resins, alkylated phenol-aldehyde novolac resins, hydrocarbon-phenol resins, hydrocarbon-halogenated phenol resins, hydrocarbon-alkylated phenol resins or a combination of two or more thereof .

The solvent composition of the present invention is particularly useful for dissolving a dicyandiamide, such as a substituted dicyandiamide or non-substituted dicyandiamide (cyanoguanidine) . The solvent composition of the present invention is also useful for dissolving substituted dicyandiamides, such as dicyandiamides wherein some, but not all, hydrogens bonded to a nitrogen are replaced by alkyl, preferably C^-alkyl, more preferably methyl, ethyl or the propyl groups; or by aryl, preferably benzyl, more preferably 2-methylbenzyl . Preferably, the dicyandiamide carries only one of the above-listed substituents. Most preferably, the dicyandiamide is not substituted.

The solvent composition of the present invention is useful for dissolving one or more of the above-mentioned curing agents for epoxy resins. The term "a curing agent" as used herein also comprises mixtures of two or more compounds which act as a curing agent for an epoxy resin.

Preferably from 1 to 20 percent, more preferably from

2 to 15 percent, most preferably from 3 to 12 percent of a curing agent is dissolved in the solvent composition, by the weight of the solvent composition. It is to be understood that the solubility of the curing agent in the solvent composition of the present invention depends on various factors, such as the type of the curing agent, the specific composition of the solvent composition and the amounts and types of compounds which may additionally be dissolved in the solvent composition, such as a curing catalyst or a cure inhibitor. The solubility of a specific curing agent in a specific solvent composition of the present invention can be evaluated by series trials .

Curing catalysts or curing accelerators which increase the speed of reaction between the curing agent and the epoxy resin are also well known in the art. Preferred are tertiary amine- containing or heterocyclic amine containing compounds. Some curing catalysts may have an effect as a curing agent per se, such as benzoguanamidine, imidazoles, benzodimethylamine, metaphenolene diamine, or N,N,N' ,N' -tetramethyl-1, 3-butadiamine . Preferred imidazoles are 2-methyl imidazole, 2-ethyl-4-methyl-imidazole or 2-phenylimidazole. 2-Methyl imidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole are the most preferred curing catalysts. Other curing catalysts which may be dissolved in the solvent composition of the present invention are heterocyclic nitrogen compounds, phosphines, sulfides or ammonium, phosphonium or sulfonium containing compounds. Such curing catalysts are listed on page 12, lines 41 to 50, on pages 13 to 16 and on page 17, lines 1 to 22 of the published European patent application EP-A-0 , 458 , 502. The solvent composition of the present invention is useful for dissolving one or more of the above-mentioned curing catalysts . The term "a curing catalyst" as used herein also comprises mixtures of two or more compounds which influence the speed of reaction between an epoxy resin and an epoxy hardener.

If the solvent composition is used for dissolving a curing catalyst, generally from 0.1 to 40 percent, preferably from 0.5 to 35 percent, more preferably from 1 to 20 percent and most preferably from 2 to 12 percent of a curing catalyst is dissolved in the solvent composition, by the weight of the solvent composition. It is to be understood that the solubility of the curing catalyst in the solvent composition of the present invention depends on various factors, such as the type of curing catalyst, the amount and type of curing agent which is optionally present in the solvent composition, the specific composition of the solvent composition and the amounts and types of compounds which may additionally be dissolved in the solvent composition. The solubility of a specific curing catalyst in a specific solvent composition of the present invention can be evaluated by series trials . In the case of imidazoles such as

2-methylimidazole, preferably from 1 to 20, more preferably from 2 to 12 percent of an imidazole is dissolved in the solvent composition, by the weight of the solvent composition.

Useful cure inhibitors are boric acid, metaboric acid, boric acid anhydride or maleic acid or a mixture of (meta) boric acid (anhydride) with at least one acid having a weak nucleophilic anion, such as fluoroboric acid (HBF₄) . Cure inhibitors are described on page 17, lines 18 to 50 and page 18, lines 1 to 38 of the published European patent application EP-A-0 , 458 , 502. If a cure inhibitor is dissolved in the solvent composition, it is preferably dissolved in the solvent composition in an amount of from 0.1 to 12 percent, more preferably from 0.5 to 6 percent, most preferably of from 1 to 4 percent , by the weight of the solvent composition. If the solvent composition of the present invention comprises substantial amounts of a curing agent, for example between 3 and 12 percent of dicyandiamide, the solubility of the curing catalyst and/or the cure inhibitor in the solvent composition is generally smaller, usually between 0.1 and 3 percent, typically between 0.5 and 2 percent, based on the weight of the solvent composition.

The desired amount of curing agent (s) and/or curing catalyst (s) and/or cure inhibitor (s) is added to the solvent composition and the resulting mixture is preferably stirred until a clear solution is obtained. The compounds to be dissolved can be added together or alternatingly to the solvent composition of the present invention. Alternatively, each compound can be dissolved individually in the solvent composition and the resulting solutions can be combined if desired. Preferred compositions of the resulting solutions of the present invention are described above.

According to another aspect of the invention, one or more compounds selected from curing agents for an epoxy resin, curing catalysts, and cure inhibitors are first dissolved in component a) or component b) and optionally another solvent of the solvent composition and component b) or a) is subsequently added. For example, dicyandiamide is preferably first dissolved in a glycol monoether or diether a) and the optional component c) and at a later stage component b) is added.

Another preferred aspect of the present invention is an epoxy resin composition comprising an epoxy resin and preferably one or more compounds selected from curing agents for an epoxy resin, curing catalysts and cure inhibitors, in a solvent composition described further above.

The epoxy resin composition can be prepared in a known manner. According to a preferred method, an above-described solution of a curing agent and/or a curing catalyst and/or a cure inhibitor in the solvent composition of the present invention is mixed with an epoxy resin. Typically the epoxy resin is diluted with a solvent. Although the solvent for the epoxy resin can be added simultaneously or after the epoxy resin has been mixed with the solution of the curing agent, curing catalyst and/or cure inhibitor, the epoxy resin is preferably pre-mixed with the solvent. The epoxy resin solution is then mixed with the solution of the curing agent, curing catalyst and/or cure inhibitor for producing an epoxy resin composition which is typically designated in the art as "one-component epoxy resin composition" .

The epoxy resin composition may comprise a wide variety of epoxy resins, provided that they are curable, preferably with dicyandiamide. Curable epoxy resins are well known in the art. Illustrative examples of epoxy resins useful herein are described in The Handbook of Epoxy Resins by H. Lee and K. Neville, published in 1967 by McGraw-Hill, New York, in appendix 4-1, pp. 4 through 56, and U.S. Patent Nos . 2,633,458; 3,477,990; 3,821,243; 3,970,719; 3,975,397; 4,071,477; and 4,582,892, and GB Patent Specification No. 1,597,610.

Useful solvents or diluents for the epoxy resin are well known in the art. Preferred examples are 2-methyl-pentanediol- (2,4), toluene, o-dichlorobenzene, cyclohexanone, cyclohexanol or, more preferably, a ketone, such as acetone, methyl ethyl ketone or methyl isobutyl ketone. Mixtures of different solvents are also useful for dissolving the epoxy resin. Preferably, the epoxy resin is dissolved in one, two, three or more of the components of the solvent composition of the present invention. Generally, from 50 to 95 percent, preferably from 60 to 90 percent, more preferably from 70 to 85 percent epoxy resin is dissolved in or diluted with a suitable solvent, based on the total weight of epoxy resin and solvent.

The epoxy resin composition preferably comprises from

0.05 to 10 percent, more preferably from 0.1 to 6 percent, most preferably from 0.5 to 4 percent of a curing agent , such as dicyandiamide, based on the weight of the epoxy resin. The epoxy resin composition preferably also comprises from 0.01 to 4 percent, more preferably from 0.05 to 2 percent of a curing catalyst, such as a 2-methylimidazole, based on the weight of the epoxy resin. The epoxy resin composition may comprise a cure inhibitor, such as boric acid, for modifying the curing catalyst. The amount of such cure inhibitor, if present, preferably is up to 4 percent, more preferably up to 2 percent, based on the weight of the epoxy resin.

In the epoxy resin composition the total weight of the components i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors is generally from 35 to 95 percent, preferably from 45 to 75 percent, more preferably from 50 to 70 percent, based on the total weight of components i) to iv) and the solvent present in the epoxy resin composition.

The entire amount of the solvent in the epoxy resin composition may consist of the solvent composition of the present invention. However, the epoxy resin composition may also comprise other solvents, such as larger amounts of ketones than recommended for the solvent composition of the present invention. Generally from 25 to 100 percent, preferably from 40 to 100 percent, more preferably from 40 to 60 percent of the solvent present in the epoxy resin composition originates from the solvent composition of the present invention, the residual amount being a known solvent or diluent for epoxy resins, such as a ketone. The epoxy resin compositions are useful for various known applications, for example for preparing electrical laminates, and coatings. At least the preferred embodiments of the epoxy resin composition are homogeneous and generally have a viscosity that is low enough to allow a good impregnation of a reinforcing material, such as glass roving or reinforcing mats to produce reinforced epoxy compositions which cure upon heating. Techniques of impregnating reinforcing materials with epoxy resin compositions and curing the epoxy resin compositions are well known in the art.

The composition comprising one or more compounds selected from i) epoxy resins, ii) curing agents for an epoxy resin, iii) curing catalysts, and iv) cure inhibitors in the solvent composition of the present invention may comprise further components in addition to those mentioned above. For example, the composition may comprise solid particles, such as a filler. A filler which increases the fire retardant properties of the composition is particularly useful. However, the composition does not comprise more than 50 percent, preferably not more than 30 percent, most preferably not more than 25 percent of solid particles, based on the total weight of the composition.

The term "comprising" as used herein means "including" . The term "comprising" is not to be understood to mean "consisting of".

The present invention is further illustrated by the following examples which should not be construed to limit the scope of the present invention. All parts and percentages are by weight unless otherwise mentioned.

Examples 1 to 8 and Comparative Examples A to C

Solutions of dicyandiamide ( "DICY" ) in various individual solvents and solvent compositions are prepared. The concentrations are listed in Table I below. The produced solutions are visually inspected at room temperature (RT) whether they are clear. Clear solutions are designated as "Y" (Yes) . Those that are not clear are designated as "N" (No) in Table I below. The solutions that are clear at room temperature are tested whether they remain clear after they have been stored at 5°C for 24 hours.

Furthermore, Table I lists whether the solutions contain harmful or toxic chemicals, as defined by the EU criteria, which is a Classification according to Annex I of Council Directive 67/548/EEC (Dangerous Substances Directive) .

Table I

wt.-% DICY, based on total amount of solvents

The DICY (dicyandiamide) solutions in Examples 2 to 8 in Table 1 are clear and do not contain harmful or toxic chemicals as defined by the above-mentioned EU criteria. The same is true for Comparative Example B. However, as illustrated by Comparative Examples O and P in Table 4 below, a solvent composition comprising propylene glycol methyl ether and water without the presence of a carbonate is sensitive towards changes in the chosen epoxy resin. The comparison between Examples 1 and 5 illustrates that advantageously a third component c) , such as water, is included in the solvent composition of the present invention if the solvent composition comprises propylene carbonate.

Examples 9 to 20 and Comparative Examples D to P

Solutions of dicyandiamide ( "DICY" ) in various individual solvents and solvent compositions are prepared. The solutions are blended with an epoxy resin solution. In Examples 9 to 13 and Comparative Examples D to J the epoxy resin is dissolved in propylene glycol methyl ether or ethylene glycol methyl ether. In Examples 14 to 18 and Comparative Examples K and L the epoxy resin is dissolved in methyl ethyl ketone. In Examples 19 and 20 and Comparative Examples M to P the epoxy resin is dissolved in acetone.

With the exception of Example 20 and Comparative Example P a brominated epoxy resin in methyl ethyl ketone is used which is commercially available under the trademark D.E.R. 539 EK80 from The Dow Chemical Company. In Example 20 and Comparative Example P a brominated epoxy resin in acetone is used which is commercially available under the trademark D.E.R. 592 A80 from The Dow Chemical Company.

The compositions of the final blends are listed in Tables 2 to 4 below. If the produced blend is clear and homogeneous at room temperature, it is classified as being compatible with the epoxy resin and is designated as "Y" . Otherwise, for example if the resulting blend is turbid or contains two phases, it is designated as "N" . Laminates are produced and visually inspected as to whether dicyandiamide crystals are visible and if yes, to what extent. The laminates are classified as unacceptable laminate^" quality ("U"), acceptable laminate quality ("ACC"), standard laminate quality ("ST"), and superior laminate quality) ( "SUP" ) .

Furthermore, Tables 2 to 4 list whether the solutions contain harmful or toxic chemicals, as defined by the EU criteria, which is a Classification according to Annex I of Council Directive 67/548/EEC (Dangerous Substances Directive) .

Table II

- " means: not tested

Table III

- " means : not tested

Table IV

means : not tested

Contains D.E.R. 592 A80 (Trademark) instead of D.E.R. 539 EK80 (Trademark)

The compositions of Examples 10 to 13, 19 and 20 are all compatible with the epoxy resin, that means that these formulations are clear and homogeneous, even in the absence of dimethyl formamide, which is classified as harmful or toxic by the above- mentioned EU criteria.

The comparison between Examples 9 and 10 illustrates that advantageously a third component c) , such as water, is included in the solvent composition of the present invention if the solvent composition contains propylene carbonate. Examples 11 and 12 illustrate that the compositions are compatible with the epoxy resin with or without a third component c) , such as water, if the solvent composition contains ethylene carbonate.

Examples 14 to 18 illustrate that it is advisable to keep the water content within the more and most preferred range, that means from 2 to 15 percent, most preferably from 5 to 12 percent, based on the total weight of propylene glycol methyl ether (component a) , propylene carbonate (component b) , and water (component c) , if the epoxy resin is dissolved in methyl ethyl ketone. The compositions of Comparative Examples D-M and P are either not compatible with the epoxy resin or contain dimethyl formamide, which is classified as harmful or toxic by the above- mentioned EU criteria.

The composition of Comparative Examples O and P is sensitive towards changes in the chosen epoxy resin. While the composition of Comparative Example 0 is compatible with the D.E.R. 539 EK80 (Trademark) epoxy resin, the corresponding composition of Comparative Example P is not compatible with the D.E.R. 592 A80 epoxy resin. The comparison between Examples 19 and 20 illustrates that the solvent composition of the present invention, specifically the solvent composition comprising propylene glycol methyl ether, propylene carbonate and water, is compatible with two different types of epoxy resins.

Claims

CLAIMS :

1. A solvent composition comprising

a) a glycol monoether or diether and

b) an organic low molecular weight compound containing a carbonate group .

2. The solvent composition of Claim 1 additionally comprising c) a protic liquid other than a glycol monoether or diether.

3. The solvent composition of Claim 1 or Claim 2 wherein component a) is a propylene or butylene glycol monoether represented by Formula I

RjO - (CH₂ - CHR³0)_n - R₂ (I)

wherein

one of the substituents R_ and R₂ is an alkyl group having from 1 to 12 carbon atoms and the other of the substituents R_x and R₂ is hydrogen,

R in each occurrence independently is methyl or ethyl and

n is from 1 to 4.

4. The solvent composition of Claim 3 wherein in Formula I one of the substituents R_± and R₂ is an alkyl group having from 1 to 4 carbon atoms and the other of the substituents R_ and R₂ is hydrogen, R³ in each occurrence is methyl and n is 1, 2 or 3.

5. The solvent composition of any one of Claims 1 to 4 wherein component b) is butylene carbonate, propylene carbonate or ethylene carbonate.

6. The solvent composition of any one of Claims 2 to 5 wherein component c) is water.

7. The solvent composition of any one of Claims 1 to 6 comprising a) a propylene glycol monoether, b) propylene carbonate and c ) water .

8. The solvent composition of any one of Claims 1 to 6 comprising a) a propylene glycol monoether and b) ethylene carbonate .

9. The solvent composition of any one of Claims 2 to 8 comprising at least 45 percent of component a) ,

from 1 to 30 percent of the component b) and

from 0 to 25 percent of component c) , based on the total weight of a) , b) and c) .

10. A composition comprising one or more compounds selected from

i) epoxy resins,

ii) curing agents for an epoxy resin,

iii) curing catalysts, and

iv) cure inhibitors,

in a solvent composition set forth in any one of claims 1 to 9.

11. A method of preparing a composition comprising one or more compounds selected from

i) epoxy resins,

ii) curing agents for an epoxy resin,

iii) curing catalysts, and

iv) cure inhibitors,

in a solvent composition by contacting one or more such compounds with a) a glycol monoether or diether and

b) an organic low molecular weight compound containing a carbonate group .

12. Use of

a) a glycol monoether or diether and

b) an organic low molecular weight compound containing a carbonate group

as a diluent for one or more compounds selected from

i) epoxy resins,

ii) curing agents for an epoxy resin,

iii) curing catalysts, and

iv) cure inhibitors.