CA2054212C

CA2054212C - Method for polymerization of epoxide compounds

Info

Publication number: CA2054212C
Application number: CA002054212A
Authority: CA
Inventors: Axel Bottcher; Egon Uhlig; Manfred Fedtke; Manfred Doring; Klaus Dathe; Bernd Nestler
Original assignee: Bakelite AG
Current assignee: Hexion Specialty Chemicals AG
Priority date: 1990-03-09
Filing date: 1991-03-06
Publication date: 1997-02-11
Anticipated expiration: 2011-03-06
Also published as: WO1991013925A1; KR970001539B1; JPH05504593A; DE59104812D1; LV10116A; EP0518908A1; GR920300130T1; ES2036162T1; BR9104778A; EP0518908B1; CA2054212A1; JP3215106B2; ES2036162T3; LV10116B; KR920701297A; ATE119174T1

Abstract

The present invention relates to a polymerization process by means of a Lewis base that initiates the reaction. This process is characterized in that an epoxide compound, for example, diglycidyl ether of bisphenol-A, is mixed with a metal complex compound having the general formula MLx8y , or M [SR]x BZ , wherein M represents a metal ion, L represents a ligand, SR an acid radical ion of an inorganic acid, B is a Lewis base, x is a natural number analogous to the valency of the metal ion, y is a natural number and z is a natural number greater than 6, and that thermal energy is supplied.

Description

2~54212 The present invention relates to a polymerization process of epoxidic compounds by means of a Lewis base that initiates the reaction. Because of the kind of reaction mechanism said process allows the polymerization of the epoxidic compounds to be so carried out that universally applicable adhesive, laminate and moulding materials for medical science, for the protection of the environment, particularly for the adjustment of adhesive parts in the optical industry, can be produced.

Furthermore, the solvent-free production of epoxy-resin compounds is thus realized. These epoxy-resin compounds are applicable, e.g. in moulding and laminated materials, as well as universally but particularly in medicine, in the protection of the environment and in the optical industry.

However, this polymerization process is particularly suitable in the production of prepegs and laminates with epoxy-resin as binder, particularly for the production of base materials for high-grade electric circuit boards and for high-quality composite materials.

It is known that Lewis bases, as for example imidazoles are very reactive initiators of polymerization reactions of materials containing epoxide and oxirane groups (Ricciardi, F. et al., J. Polym. Sci. Polym. Ehem.
Ed. 1983, 21, 1475-90, Farkas A. et al., J. Appl. Polym.
Sci. 1968, 12, 159-68). It has been found that the disadvantage of these solutions lies in the substantial increase in temperature during the polymerization process resulting in undesired discoloration of the polymerization materials and in inhomogeneities within the polymerization materials.

DE-OS 2,810,428 describes a method of modifying the strong reactivity of the Lewis bases applied t8 ~e~
polymerizable epoxide compounds by adding solvents "from the group methanol, ethanol or mixtures thereof".

The problems caused by these solvents are the requirement of additional process steps in order to remove the solvent after the polymerization and the formation of quality-reducing pockets in the polymer that increase the water absorption of the polymer.

In the U.S. Patent 3,638,007, 3,792,016, and 4,101,514 and in the DEPS 2,300,489 imidazole metal compounds are tested for their effect as Lewis base for the reactive induction of polymerization reactions.
These compounds represent very stable coordination polymers and, for these reasons, they split off imidazole only at relatively high temperatures, where upon the imidazole displays its action as Lewis base. At temperatures lower than 170C no accelerating effect on the epoxide monomers is observed.

The problem encountered in polymerization reactions with epoxides at these high temperatures lies in the formation of ring cleavage products that cause a poor network structure and thus negative polymer properties, such as shrinkage characteristics, water absorption, etc.

The temperatures can be reduced by the application of auxiliary bases and the activating effect can thus be controlled.

However, the application of these auxiliary bases has the following disadvantages:
- high expenditure since these auxiliary bases are very costly, - the possibility that the auxiliary bases per se react with the epoxide systems. 2 0 5 ~ 2 i 2 The use of imidazole complexes of a great variety of metal salts, for example, CuCl2, CUS04, NiCl2 and CoCl2, that contain 1 to 6 moles of imidazole per mole of metal, salt, as latent initiators is described in the U.S.
Patent 3,677,978.

The disadvantages are:
- the high gelling temperature of approximately 160 to 260C resulting in homogeneities and black coloration, - the non-homogeneous solubility of the polymerizing reaction mixture.

The use of imidazole complexes and of an additional nitrogen-containing compound for the hardening of epoxide resins is described in the U.S. Patent 3,553,166 as well.
The required processing temperature also is about 180C.

It is also known to convert imidazoles into latent hardeners and initiators by salt formation with different acids, such as polycarboxilic acid (US-PS 3,746,686), isocyanuric acid (DE-PS 2,811,764), phosphoric acid (US-PS 3,632,427, 3,642,698 and 3,635,894). The special problems of these processes are as follows:
- the high toxic effect of the imidazole compounds, - the premature termination of the polymerization due to the present of anions and, associated therewith, an increased proportion of monomers in the polymer and the presence of parameters such as exudation and increased water absorption.

From DE-PS 2,019,816 and US-PS 4,127,275 the use of acetyl acetonate complexes for the polymerization of epoxide compounds even in the presence of carboxylic anhydrides is known. The disadvantage of these solutions 20542 1 ~

lies in the high processing temperature that exceed 150C.

Apart from the above-mentioned problems with polymerization reactions with epoxides at these high temperatures it means that said process results in enormous processing cost restricting substantially the range of application.

DE-PS 2,525,248 describes, for example, the use of Cr(acac)3, wherein acac represents acetyl acetonate, as hardening system for epoxide resin materials. The disadvantage lies in that an unstable hydrogen compound must be present in addition to the oxirane oxygen compound in order to attain the polymerization or curing.
A further disadvantage of these mixtures lies in that frequently the polymerization starts directly following the addition of the hardener. Thus, polymers having good storage properties cannot be guaranteed.

The general problem due to the use of imidazoles as initiator lies, for example, in that complete hardening occurs immediately upon its application regardless of whether it is applied in a free form or in the bonded form. Therefore, there always exists two states of the resin material, the non-crosslinked state on the one hand and the completely cross-linked state on the other. In fact this assures the use as moulding and laminated material having optimal gelling times, which can also be varied depending on the kind of imidazole used. However it is not possible to attain a reaction phase of slow hardening upon adding the initiator and, associated therewith, to insert an individual processing phase, for example, an adjusting phase on fitting the parts to be joined, prior to the actual hardening phase.

205~2 1 2 It is the aim of the present invention to provide a process for the polymerization of epoxide compounds by means of a Lewis base, i.e., a process that allows the production of environment-friendly non-toxic epoxide resin materials, at a favorable cost, that is based on metal complexes. Said epoxide compounds must have favorable gelling times.

The present invention is based on the aim of providing a process for the polymerization of epoxide compounds by means of a Lewis base as initiator. This process realizes the latent initiation of the polymerization by thermal cleavage of the initiator from the complex at temperatures lower than 140C.

According to the present invention the aim is achieved by a process for the polymerization of epoxide compounds by means of a Lewis base that initiates the reaction in the 100 parts by weight of the epoxide compound are reacted with 0.1 to 50 parts by weight, preferably l to 10 parts by weight of a metal complex compound having the general formula MLXBy, or M CSR~X B~ .

wherein 205~212 - M represents a metal ion, - L represents a ligand, - SE represents and acid radical ion, - B represents a Lewis base, - x represents a natural number in the range of 1 to 8, - y represents a natural number in the range of 1 to 5, - z represents a natural number in the range of 7 to 8 and that energy is supplied.

According to the process of the present invention epoxide compounds containing more than one epoxide compound may be used as epoxide compounds.

Preferred epoxide compounds are polyphenol-glycide either, for example, epoxidized novolaks or the reaction products of epichlorohydrin and bisphenol A or bisphenol F. That kind of epoxy resins have an epoxide equivalent of 160 to 500. Said poly-functional epoxide compounds (this term also includes epoxy resins) can be polymerized individually or in mixture by means of the present process, when required in the presence of solvents. They can also be applied in mixture with monoepoxides (so-called reactive diluents).

Fundamentally any metal ion may serve as metal but primarily the ions of the second and third main group of the periodic system of the elements and the metal ions of the elements of the odd series.

Preferred metal ions are cobalt, nickel, iron, zinc or manganese ions. Ligands (L) are either chelate-forming ligands or any aliphatic or aromatic carboxy,lic acid. Chelate-forming ligands are organic compounds containing two atom groupings which act as electron donors. Examples are dioximes, alpha- and B- hydroxy-carbonyl compounds or even enolizable 1,3-diketones.

-2o~212 Preferred chelate ligands are acetyl acetone, benzoyl acetonate or dipivaloyl methane.

Any acid radical of an inorganic acid may serve as acid radical ion.

Any nucleophilic molecule or ion having a lone-pair electron is suitable as Lewis bases (B) for the metal complex compounds to be applied according to the present invention. Examples are pyridine or imidazole compounds, ethers including cyclic ethers, as for example, tetrahydrofuran, alcohols, ketones, thioether or mercaptanes.

However, in the complexes according to the formula MLXBy Lewis bases can also be CH-acidic compounds which are present as Lewis bases, i.e., CH-acidic compounds in which a proton is split off. Examples of the CH-acidic Lewis bases are CH-acidic pyridine, malonic diester or dinitrile, acetoacetic ester, cyanoacetic ester or nitromethane.

The charge equalization of the metal cations of the metal complex compounds to be applied can be caused by the ligands as well as by ionic Lewis bases. In this case it is understood that the number of charge-carrying ligands, particularly of the organic or inorganic acid radicals decreases when the complex contains ionic Lewis basis.

An additional feature of the complexes applied according to the present invention lies in that the CH-acidic Lewis bases are linked to the metal -chelate compound via nitrogen and/or oxygen and/or sulphur and/or phosphorus atoms and hydrogen bridges.

- 20~42i~
These metal complex compounds are obtained in a conventional manner by reacting the corresponding metal salts with the desired ligands and Lewis bases.

The following metal complexes are particularly suitable metal complex compounds:
bis(acetylacetonato)-cobalt-II-diimidazole, bis(acetylacetonato)-nickel-II-diimidazole, bis(acetylacetonato)-zinc-II-diimidazole, bis(acetylacetonato)-manganise-II-diimidazole, bis(acetylacetonato)-iron-II-diimidazole, bis(acetylacetonato)-cobalt-II-didinethyl imidazole, bis(acetylacetonato)-cobalt-II-dibenzimidazole, bis(acetonate)-cobalt-II-diimidazole, bist2-ethylhexanato]-cobalt-II-diimidazole, and bis(salisylaldehydo)-cobalt-II-diimidazole.

According to the present invention the complexes are mixed with the epoxide compounds at a temperature lower than the initiation temperature, i.e., preferably in the range of room temperature to 50C.

In this range the mixtures have good storage properties and can be processed into moulding or casting materials, adhesive mixtures or prepegs.

The epoxide compound is cured by supplying energy while the temperature rises above the initiation temperature of the complexes.

The energy may be supplied in the form of thermal energy, light, microwaves, radiation, laser energy, etc.
The advantages of the present invention lie substantially in that - there is provided a possibility of dissolving the 205~212 metal complex in the polymerizable epoxide compound or in the polymerizable epoxide mixture, at a temperature below that initiating the polymerization, - homogeneous polymer materials are thus forming, - when using benzoyl acetonate or dipivaloyl methane as ligands the polymer materials can be transparent and when using acid ions, such as sulphates, nitrates, halides, phosphates, etc., they can be colored, - no solvents for moderating the reactivity of the Lewis bases are required.
- additional process steps for the removal of the solvent are thus not required, - thus no property-reducing bubbles are formed in the polymer, - no increased water absorptivity of the polymer associated therewith can be detected, - no toxic effect is detected in the imidazole compounds which are toxic per se and act as initiators in the present case, - the cleavage of the Lewis base - metal compound occurs at temperatures above room temperature, preferably at temperatures between 60 and 140C, - even these "one-component systems" consisting of monomers and a metal complex can be stored and moulded for an unlimited time at the polymerization-initiating temperature and are hardened only upon reaching the initiation temperature.

The application of the metal complexes with the polymerizable compound can be carried out with or without the addition of further additives (for example, hardeners) i.e., the polymer mixtures are multivariable.

The start of the polymerization, i.e., the initiation temperature, can be determined by the selection of the ligands, by the selection of the Lewis 20~4212 bases and by the selection of the acid radical ions.
Complexes with anions react at lower temperatures than complexes with chelate ligands. The application of substituted Lewis bases, for example, alkylated imidazoles, also has an effect on the initiation temperature which will be lower than in the case when imidazole is used as Lewis base.

The polymerization initiation temperature can be varied within wide limits by suitably selecting the complexes according to the type of the ligands, Lewis bases and metal.

Surprisingly the reaction between the initiator and the polymerizable compound proceeds at distinctly lower temperatures than would have been expected on account of the complex decomposition temperatures known from the literature.

Furthermore, as compared with the use of pure Lewis bases, such as imidazole, in the polymerization of epoxide compounds by means of the metal complex compounds applied according to the present invention a reduced water absorbing capacity and acetone absorption are attained in addition to optimal gelling times.

The application of substituted Lewis bases, for example, alkylated imidazoles, also has an effect on the initiation temperature which will be lower than in the case when imidazole is used as Lewis base.

Further advantages of the process according to the present invention lie in that the polymerization preferably occurs at temperatures of between 60 and 140C, that these "one component systems" can be moulded below the polymerization temperature after an arbitiarily 2o5~212 long storage time and are cured only on reaching the inititation temperature and that no toxic effect can be detected in those imidazole compounds which are toxic per se and act as initiators in the present case.

With the solution of this problem it has become possible to produce, at a favorable cost, environment-friendly and non-toxic latent epoxy resin materials having optimal gelling times, i.e., epoxy resin compounds based on metal complex compounds.

These mixtures contain 100 parts by weight of the epoxide compound and 0.01 to 50 parts by weight, preferably 1 to 10 parts by weight of a metal complex compound having the general formula x y ~ or CSR]X 8~

wherein - M represents a metal ion, - L represents a ligand, - SR represents an acid radical ion, - B represents a Lewis base, - x represents a natural number ranging from 1 to 8, - y represents a natural number ranging from 1 to 5, and - z represents a natural number ranging from 7 to 8.

On account of their properties these mixtures - when required upon addition of conventional fillers and additives - are suitable for the production of adhesives and sealing compounds. They serve as binders for moulding materials, particularly for large moulded parts which are hardening free from stress.

20~212 Despite the ions-containing metal complex compounds the epoxide compounds polymerized according to the present invention have outstanding electrically insulating properties. Therefore, the mixtures are suitable for the production of high-grade electric printed circuit boards and as binders for sealing compounds, particularly in the fields of electrote~-hn;cs and electronics.

EXAMPLES

The present invention will be explained hereafter by means of various practical examples.

For carrying out the tests 1 mole of the epoxide compound was mixed with 0.05 mole of the respective metal complex compound, at room temperature. The mixture was divided: The gelling time was determined with lOOg of the mixture as in DIN 16945, Section 6, 3 (process A).

In order to determine the absorption of water and that of acetone, a portion of the mixture was poured as test specimens and polymerized.

The rest of the mixture was stored at room temperature. After a storage time of more than 6 months no polymerization could be detected.

The results have been compiled in the Table hereafter. 9 ~.
In the table 9 represents imidazole, MJ represents 2-methylimidazole, RT represents room temperature Tg (in the Examples 6 to 8) represents the glass transition temperature, determined according to DIN 16946 For the individual tests the Table lists 20 5 42 12 - the epoxide compounds used in the individual tests, - the metal complex compounds used in the individual tests with the gelling times attained by them as a function of the temperature, - the water absorption of the polymerized epoxide compounds in percent report heating for 2 hours at 100C.

The acetone absorption in percent upon heating for 4 hours at boiling temperature.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for polymerizing an epoxide compound using a metal complex, wherein the polymerization is effected with 0.01 to 50 parts by weight of the metal complex per 100 parts by weight of the epoxide compound, and wherein the metal complex is selected from:
MLXBy and M[SR]xBz wherein:
M represents a metal ion of Groups II or III and the sub-groups thereof of the Periodic Table;
L represents a chelating ligand selected from the group consisting of a dioxime, .alpha.- and .beta.-hydroxycarbonyl compounds, and an enolizable 1,3-diketone;
B represents a Lewis base other than a polvalent phenolic compound;
SR represents an acid residue ion of an inorganic acid;
x, for Lx, is one or 2, and for [SR]X, is an integer of from one to 8;
y is an integer of from one to 5; and z is 7 or 8.

2. The process of claim 1, wherein the metal complex comprises a benzoyl acetonate or dipivaloyl methane ligand.

3. The process of claim 1, wherein M is selected from the group consisting of Co, Ni, Fe, Zn and Nn.

4. The process of claim 1, wherein B is selected from the group consisting of pyridine, imidazole, tetrahydrofuran, alcohols, ketones, thioethers and mercaptans.

5. The process of claim 1, wherein B is selected from the group consisting of CH-acidic pyridine, malonic acid diesters, malonic acid dinitriles, acetoacetic esters, cyanoacetic esters and nitromethane.

6. A polymerizable mixture comprising per 100 parts by weight of an epoxide compound 0.01 to 50 parts by weight of a metal complex as defined in any one of claims 1 to 5.

7. The mixture of claim 6, comprising 1 to 10 parts by weight of the metal complex.

8. Use of the mixture of claim 6, for the manufacture of adhesive and sealing materials.

9. Use of the mixture of claim 6, as a binding agent in moulding materials.

10. Use of the mixture of claim 6, as a binding agent for casting materials in the electric or electronic fields.

11. Use of the mixture of claim 6, for the manufacture of electronic printed circuit boards.

12. Use of the mixture of claim 6, for the manufacture of high performance composite materials.