CA2152428A1

CA2152428A1 - Epoxy resins, their preparation, and use

Info

Publication number: CA2152428A1
Application number: CA002152428A
Authority: CA
Inventors: Uwe Neumann; Michael Hoenel
Original assignee: Individual
Current assignee: Solutia Germany GmbH and Co KG
Priority date: 1994-06-30
Filing date: 1995-06-22
Publication date: 1995-12-31
Also published as: DE59510871D1; ATE261464T1; EP0698630B1; AU688900B2; KR960000944A; CN1127264A; EP0698630A1; JPH08100047A; AU2332695A

Abstract

Epoxy resins including bisphenol compounds which are attached, at least one of the aromatic rings of the bisphenols and by way of in each case a linear or branched, substituted or unsubstituted alkylene radical, to at least one aryl radical, are useful, for example, in coating and molding compositions.

Description

EPOXY RESINS, T~EIR PREPARATION, AND USE

Background of the Invention Field of the Invention The present invention relates to epoxy resins composed of aralkylated diphenols and diepoxides or of aralkylated diphenols and epichlorohydrin, to processes for their preparation, and to methods for their use.

Description of Related Art Resins having epoxide groups are generally known.
See, for example, H. Lee, K. Neville in "Handbook of Epoxy Resins," Reissue 1982, McGraw-Hill Book Company, New York; C. A. May in "Epoxy Resins," Marcel Dekker, Inc. New York and Basel, 1988. They can be prepared, for example, by reacting polyhydric phenols with epichloro-hydrin in the presence of sodium hydroxide solution or byaddition of bisphenols onto bisepoxides. These relatively low molecular weight reactive resins are very widespread in materials applications, since a high degree of variability in the pattern of properties can be obtained by modification of the epoxy and phenol basic structures.
The known, commercially available epoxy resins are insoluble, or insufficiently soluble, in aromatic solvents, and are only soluble in the considerably more expensive aliphatic esters and ethers, such as, for example, butyl acetate, methoxypropanol, ethylene glycol monobutyl ether, and diethylene glycol dimethyl ether.

Summary of the Invention It is therefore an object of the present invention to provide epoxy resins which are soluble in aromatic solvents, such as xylene or toluene, while retaining the outstanding level of properties of the known epoxy resins.

It is also an object of the invention to provide methods of making and using such epoxy resins.
It is possible in accordance with the invention to achieve these and other objects by replacing at least a part of the bisphenols which are customarily used to prepare the epoxy resins, by aralkylated bisphenols.
Accordingly, there is provided in accordance with the present invention, an epoxy resin comprising a bisphenol compound which is attached, at at least one of the aromatic rings of the bisphenol and by way of in each case a linear or branched, substituted or unsubstituted, alkylene radical, to at least one aryl radical, such that the bisphenol compound is aralkylated.
In accordance with the invention, there also is provided a two-stage process for the preparation of a modified epoxy resin, which comprises reacting, in the first stage, a bisphenol component with an alkenylaromatic component in the presence of a weak acid, optionally adding a further quantity of the same or of a different bisphenol component, and then reacting the product with an epoxide component.
In accordance with the invention, there also is provided a one-stage process for the preparation of a modified epoxy resin, which comprises reacting a mixture of an aralkylated bisphenol component and a nonaralkylated bisphenol component with an epoxide component.
There also is provided a method of using the composition, for example, in coating, adhesive, molding, and construction resins.
Further objects, features, and advantages of the present invention will become apparent from the detailed description of preferred embodiments which follows.

Detailed Description of the Preferred Embodiments The present invention provides epoxy resins comprising bisphenol compounds to which are attached aryl radicals. The aryl radicals are attached to at least one 21524~8 of the aromatic rings of the bisphenols by way of in each case a linear or branched, substituted or unsubstituted alkylene radical. That is, the bisphenols are aralkylated. The proportion of these aralkylated bisphenol compounds may be varied as desired and is, in accordance with the invention, generalIy between 10 and 90%, preferably between 20 and 80% and, with particular preference, between 30 and 70% of the overall mass of bisphenol compounds which are employed to prepare the epoxy resin. The remaining proportion of bisphenols are the nonaralkylated bisphenols conventionally employed in epoxy resins.
Similarly, it is possible to employ, in combination with the above-mentioned proportions of aralkylated bisphenols, aliphatic diols instead of, or in addition to, the unsubstituted bisphenols. It is also possible to replace a small proportion, for example, up to 5% of the quantity of material, of the bisphenols and/or of the diepoxide compounds by polyphenols having three or more hydroxyl groups and/or polyepoxide compounds containing three or more epoxide groups in the molecule. Similarly, a small proportion, for example, up to 5~ of the quantity of material, of the bisphenols and/or of the diepoxide compounds can be replaced by monohydric phenols and/or monoepoxides.
The bisphenol compound of the epoxy resin may carry any desired number of aralkyl radicals. The invention provides, in particular, epoxy resins in which some of the bisphenol compounds carry on average one aralkyl radical. The proportion of these monosubstituted bisphenol compounds is generally between 10 and 90~, preferably between 20 and 80% and, with particular preference, between 30 and 70% of the overall mass of bisphenol compounds which are employed to prepare the epoxy resin.
A useful synthesis method of the aralkylated bisphenols which are employed for the epoxy resins according to the invention is described in the simultaneously filed German Patent Application P 44 36 097.5, and the corresponding U.S. application, filed simultaneously herewith, U.S. Attorney Docket No.
16878/620; both of which are hereby incorporated by reference in their entireties.
Any desired bisphenol compound or mixture of such compounds can be used. The bisphenols which are suitable include, for example, reaction products of dihydroxy aromatic compounds with aromatic compounds which carry an alkenyl group. In these compounds the alkenyl group may also be part of a fused-on cycloaliphatic ring which contains an endocyclic or exocyclic double bond. The aralkylation is in this case preferably carried out such that the bisphenol employed carries, after the reaction, on average one aralkyl radical. Examples of suitable bisphenols include reaction products of aralkyl compounds and one or more of bisphenol A, bisphenol F, the isomeric dihydroxybenzenes and dihydroxynaphthalenes, dihydroxydiphenyl ether, dihydroxybenzophenone, and dihydroxydiphenyl sulfone.
Suitable alkenylaromatic compounds include any of those known. They generally have 8 to 15 carbon atoms and contain at least one aromatic ring and preferably exactly one alkenyl group. Examples include styrene and its homologs, isopropenylbenzene, indene and diphenyl-ethylene. The alkenyl group may be linear or branched, and it may contain one or more alkyl substituents of 1 to 4 carbon atoms each. Suitable substituents include methyl, ethyl, propyl, i-propyl and the butyl isomers.
The reaction of the aralkylated bisphenol component, if desired in a mixture with unmodified bisphenols, to give the corresponding epoxy resins can be carried out in a number of ways, as is known to the person skilled in the art including:
1.) Chain-extending addition (Taffy process) with epichlorohydrin as epoxide component, where the excess of epichlorohydrin can be used to control the average molecular mass of the reaction product. If desired, the product can be built up further by subsequent addition of bisphenols.

2.) Reaction with bisepoxides tdiglycidyl ethers), and also with mixtures of different diglycidyl ethers as epoxide component, a so-called "advancement" reaction. The molecular mass of the diglycidyl compounds in this case is preferably on average from 100 to 525 g/mol per epoxide group.
Regardless of the method used, the aim is to have a residual content of epoxide groups in the resin which corresponds to an epoxide equivalent weight (molecular mass divided by number of epoxide groups) of from 180 to 5000 g/mol, preferably from 230 to 2000 g/mol.
The diglycidyl ethers which are suitable for the invention include any known in the art, and generally have a number-average molecular mass (Mn) of from about 300 to 7000 g/mol and an epoxide equivalent weight of from about 150 to 3500 g/mol.
Examples of useful epoxy resins include reaction products of epichlorohydrin or methylepichlorohydrin with one or more of bis(hydroxyphenyl)methane (bisphenol F), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 1,4-butanediol, 1,6-hexanediol, bis(hydroxymethyl)-cyclohexane, polyoxypropylene glycol having an average molecular mass of from 200 to 4000 g/mol, dihydroxybenzo-phenone, dihydroxynaphthalene, and/or resorcinol.
Any desired diepoxides can be used. Diepoxides of appropriate molecular mass are prepared either by selecting the proportions of bisphenol and epichloro-hydrin or by reacting the monomeric diglycidyl compounds with further bisphenol while adding catalysts such as Lewis acids, Lewis bases, or phosphonium salts. In the context of the invention, it is also possible to employ the above-described aralkylated bisphenols in the synthesis of the diglycidyl compounds.
A detailed listing of suitable epoxide compounds useful in the present invention can be found in the handbook "Epoxidverbindungen und Harze" [Epoxide 215242g compounds and resins] by A.M. Paquin, Springer Verlag, Berlin 1958, chapter IV, and in the handbooks mentioned above, each of which is incorporated by reference.
The modified epoxy resins according to the invention can be prepared in any desired manner. For example, they can be prepared by a two-stage process in which, in the first stage, a nonaralkylated bisphenol component is reacted with the alkenylaromatic component in the presence of weak acids at temperatures of from, for example, 100 to 160C, preferably from 120 to 155C. In the second stage, the product is reacted with an epoxide component, and in this case both of the process variants mentioned above can be employed. Weak acids are those acids where, in an aqueous solution containing 0,1 mol of acid per n litres of water (where n denotes the number of acid hydrogen atoms) less than 1 per cent of this acid is dissociated into ions at room temperature (20C).
In a one-stage process for the preparation of the modified epoxy resins, a mixture of an aralkylated and a nonaralkylated bisphenol component is reacted with an epoxide component for a suitable time and at a suitable temperature to give the modified epoxy resin.
As the bisphenol component, the above-mentioned bisphenols can be employed individually or in a mixture.
In the context of the invention, the term "bisphenol component" also embraces the addition of tri- or poly-hydric phenols and of monohydric phenols in a small quantity to the bisphenols. The quantity added is in each case generally less than 5%, preferably less than 2%, based on the quantity of material of the bisphenol component.
The modified epoxy resins according to the invention can be used in any desired application, for example, for the production of casting resins, adhesives, and injection molding compounds, and also as construction resins, if desired in combination with conventional inert fillers such as chalk, kaolin, sawdust, mica or glass beads, or with fibrous reinforcers such as glass, aramid, carbon or metal fibers.

, 2152428 The invention is further described with reference to the following examples. These examples are for illustrative purposes only, and do not further limit the invention.
In the examples which follow, all indications of content, parts and percentages are by mass, unless expressly stated otherwise.

Example 1 A bisphenol F 200 g (1.0 mol) B oxalic acid dihydrate 2.2 g C boric acid 1.15 g D styrene 104 g (1.0 mol) E Beckopox EP 140 #613.S g (3.35 eq) F triphenylphosphine 2.1 g 15 # Beckopox~ EP 140 is a liquid resin from Hoechst AG
based on bisphenol A.

B and C are added to A under nitrogen at 120C.
Then D is added at initially 120C in such a way that the temperature of the ensuing exothermic reaction is maintained at between 120C and 160C by the rate of dropwise addition. When the addition is complete the reaction mixture is maintained at 160C for two hours, during which the degree of reaction is checked on the basis of determination of the solids content (2 g of substance/2 g of xylene; 1 h at 160C in a circulating-air oven). The mixture is cooled to 120C and then E is added, followed by F. In the course of the ensuing reaction, the temperature rises to 160-170C. The reaction mixture is maintained at 160C until the theoretical epoxide equivalent weight is reached. An epoxy resin having the following properties is produced.

Epoxide equivalent weight 670 to 690 g/mol Viscosity at 25C/40% strength in butyldiglycol 480 to 510 mPa.s 21524~8 Example 2 A bisphenol A 228 g (1.0 mol) B oxalic acid dihydrate 4.2 g C boric acid 1.15 g D styrene 208 g (2.0 mol) E epichlorohydrin ` 650 g F tetramethylammonium chloride 2.1 g G deionized water 2.1 g H deionized water 10 g I deionized water 460 g J xylene 500 g K 10% phosphoric acid see text B and C are added to A under nitrogen at 160C.
Then D is added at initially 160C in such a way that the temperature of the ensuing exothermic reaction is maintained at between 155C and 165C by the rate of dropwise addition. When the addition is complete the reaction mixture is maintained at 160C for two hours, during which the degree of reaction is checked on the basis of determination of the solids content (2 g of substance/2 g of xylene; 1 h at 160C in a circulating-air oven). The addition of further quantities of oxalic acid may be necessary. After cooling to 100C the melt is taken up in E, followed by F dissolved in G at 60C.
The mixture is stirred at 70C for 60 minutes and then H is added over 120 minutes at 80C and at about 500 hPa in such a way that simultaneous azeotropic removal of water takes place. Epichlorohydrin is then distilled off under vacuum and with the temperature being raised (maximum temperature: 120C, reduction of the pressure to 50 hPa = 50 mbar). After leaving the reaction mixture for 30 minutes at 120C and 50 hPa, H is added over 30 minutes under the same conditions. The mixture is cooled to below 100C, the vacuum is removed, I is then added and the mixture is stirred intensively at 95OC for 15 minutes. The aqueous phase is separated off.
Based on the measured content of hydrolyzable chlorine, one and a half times the quantity of 4% strength sodium 215242~

g hydroxide solution is added with stirring. Stirring is continued for 90 minutes at 90C. The mixture is dissolved in J and the aqueous phase is separated off.
A pH of between 6.0 and 7.2 is established with K, water is removed under azeotropic conditions, about 50 ml of xylene are also stripped off, and the mixture is filtered. The solvent is removed under vacuum (up to 50 hPa) and at a maximum temperature of 150C. An epoxy resin having the following properties is produced.

Epoxide equivalent weight290 to 295 g/mol Total chlorine content < 0.4%
Content of hydrolyzable chlorine< 0.1%
Viscosity at 25C 55,000 mPa.s Example 3 A resorcinol 110 g (1.0 mol) B oxalic acid dihydrate 2.2 g C boric acid 1.15 g D styrene 130 g (1.25 mol) E Beckopox EP 140 #580 g (3.17 eq) F triphenylphosphine 1.5 g # Beckopox~ EP 140 is a liquid resin from Hoechst AG
based on bisphenol A.

B and C are added to A under nitrogen at 120C.
Then D is added at initially 120C in such a way that the temperature of the ensuing exothermic reaction is maintained at between 120C and 130C by the rate of dropwise addition. When the addition is complete the reaction mixture is maintained at 160C for two hours, during which the degree of reaction is checked on the basis of determination of the solids content (2 g of substance/2 g of xylene; 1 h at 160C in a circulating-air oven). The mixture is cooled to 120C and then E is added, followed by F. In the course of the ensuing reaction, the temperature rises to 160-170C. The reaction mixture is maintained at 160C until the 21~24~.~

theoretical epoxide equivalent weight is reached. An epoxy resin having the following properties is produced.

Epoxide equivalent weight715 to 745 g/mol Viscosity at 25C/40% strength in butyldiglycol `720 to 750 mPa.s Example 4 A bisphenol A 228 g (1.0 mol~
B oxalic acid dihydrate 2.2 g C boric acid 1.15 g D styrene 104 g (1.0 mol) E epoxy resin from Example 2744 g (2.54 eq) F triphenylphosphine 5.0 g B and C are added to A under nitrogen at 160C.
Then D is added at initially 160C in such a way that the temperature of the ensuing exothermic reaction is maintained at between 155C and 165C by the rate of dropwise addition. When the addition is complete the reaction mixture is maintained at 160C for two hours, during which the degree of reaction is checked on the basis of determination of the solids content (2 g of substance/2 g of xylene; 1 h at 160C in a circulating-air oven). Subsequent additions of oxalic acid may be necessary. The mixture is cooled to 120C and then E is added, followed by F in two or more portions. In the course of the ensuing reaction, the temperature rises to 160-170C. The reaction mixture is maintained at 160C
until the theoretical epoxide equivalent weight is reached. An epoxy resin having the following properties is produced.

Epoxide equivalent weight2000 to 2400 g/mol Viscosity at 25C/40% strength in butyldiglycol2100 to 3000 mPa.s Example 5 A bisphenol F 200 g (1.0 mol) 21~242~ `

B oxalic acid dihydrate 2.2 g C boric acid 1.15 g D indene 116 g (1.0 mol) E Beckopox EP 140 #608 g (3.32 eq) F triphenylphosphine 4.1 g # Beckopox~ EP 140 is a liquid resin from Hoechst AG
based on bisphenol A.

B and C are added to A under nitrogen at 120C.
Then D is added at initially 120C in such a way that the temperature of the ensuing exothermic reaction is maintained at between 120C and 160C by the rate of dropwise addition. When the addition is complete the reaction mixture is maintained at 160C for two hours, during which the degree of reaction is checked on the basis of determination of the solids content (2 g of substance/2 g of xylene; 1 h at 160C in a circulating-air oven). The mixture is cooled to 120C and then E is added, followed by F. In the course of the ensuing reaction, the temperature rises to 160-170C. The reaction mixture is maintained at 160C until the theoretical epoxide equivalent weight is reached. An epoxy resin having the following properties is produced.

Epoxide equivalent weight 705 to 735 g/mol Viscosity at 25C/40% strength in butyldiglycol 550 to 580 mPa.s While several embodiments of the invention have been described, it will be understood that it is capable of further modifications, and this application is intended to cover any variations, uses, or adaptations of the invention, following in general the principles of the invention and including such departures from the present disclosure as to come within knowledge or customary practice in the art to which the invention pertains.

Claims

1. An epoxy resin comprising a bisphenol compound which is attached, at at least one of the aromatic rings of the bisphenol and by way of in each case a linear or branched, substituted or unsubstituted, alkylene radical, to at least one aryl radical, such that the bisphenol compound is aralkylated.

2. An epoxy resin as claimed in claim 1, comprising an aralkylated bisphenol compound in a proportion of between 10 and 90% of the overall mass of bisphenol compound which is employed to prepare the epoxy resin.

3. An epoxy resin as claimed in claim 1, comprising an aralkylated bisphenol compound in a proportion of between 30 and 70% of the overall mass of bisphenol compound which is employed to prepare the epoxy resin.

4. An epoxy resin as claimed in claim 1, comprising an aralkylated bisphenol compound which carries on average one aralkyl substituent per mole of bisphenol compound.

5. An epoxy resin as claimed in claim 4, wherein the proportion of bisphenol compounds which carry one aralkyl substituent is between 10 and 90% of the overall mass of bisphenol compound which is employed to prepare the epoxy resin.

6. An epoxy resin as claimed in claim 1, wherein the aralkyl substituent is selected from aralkyl radicals having 8 to 15 carbon atoms.

7. An epoxy resin as claimed in claim 1, wherein the aralkyl substituent is selected from styrene and its homologs, isopropenylbenzene, indene, and diphenyl-ethylene.

8. An epoxy resin as claimed in claim 1, wherein the aralkyl substituent comprises styrene.

9. An epoxy resin as claimed in claim 1, which has an epoxide equivalent weight of from 180 to 5,000 g/mol.

10. An epoxy resin as claimed in claim 4, wherein the proportion of bisphenol compounds which carry one aralkyl substituent is between 30 and 70% of the overall mass of bisphenol compound which is employed to prepare the epoxy resin.

11. An epoxy resin as claimed in claim 1, wherein the epoxy resin comprises an epichlorohydrin as epoxide component.

12. An epoxy resin as claimed in claim 1, wherein the epoxy resin comprises a diglycidyl ether as epoxide component.

13. An epoxy resin as claimed in claim 2, comprising nonaralkylated bisphenol compound in a proportion of 10 and 90% of the overall mass of bisphenol compound which is employed to prepare the epoxy resin.

14. A two-stage process for the preparation of a modified epoxy resin, which comprises:
reacting a bisphenol component with an alkenyl-aromatic component in the presence of a weak acid, optionally adding a further quantity of the same or of a different bisphenol component, and reacting the product with an epoxide component.

15. A one-stage process for the preparation of a modified epoxy resin, which comprises reacting a mixture of an aralkylated bisphenol component and a non-aralkylated bisphenol component with an epoxide component.

16. A modified epoxy resin prepared by a process as claimed in claim 14.

17. A modified epoxy resin prepared by a process as claimed in claim 15.

18. An adhesive comprising an epoxy resin as claimed in claim 1.

19. An injection molded article comprising an epoxy resin as claimed in claim 1.

20. A construction resin comprising an epoxy resin as claimed in claim 1 and one or more of fiber reinforcements and inert fillers.