DE1570607A1 - Process for the production of foamed epoxy resins - Google Patents

Description

Process for the production of foamed epoxy resins It is known that di- or polyepoxy compounds can be converted into hard, infusible and insoluble resins by the action of Si: bs tanks, which are capable of reacting with the reactive epoxy groups by crosslinking. These substances or harders include, among others. Polycarboxylic acids or their functional derivatives, aliphatic and aromatic amines, inorganic acids and Friedel-Crafts catalysts. However, while sufficient hardening with basic compounds is only achieved with the particularly reactive polyethers and esters of glyoid, it is possible to harden the less reactive epoxidized aliphatic and cycloaliphatic di- and polyolefins with acidic hardeners, especially with polycarboxylic anhydrides. It was found that the use of rigid or bulky anhydrides led to poxy resins with increased heat resistance, which became increasingly important in machine, aircraft and rocket construction, but mainly in electrical engineering. Thus, hexahydrophthalic anhydride (I) and methylnadiesic anhydride (II) are introduced, which gave resins with increased heat resistance.

The use of the even more effective acid anhydride (III) and pyromellitic anhydride (IV) are, however, opposed by the great practical difficulties resulting from the high melting points.

To dissolve the last-mentioned hardeners (II) and (IV) in the Epoxy resin requires so high temperatures that a satisfactory service life the Gie @ resin mixtures are not given.

To create starter foams on the basis of acid hardened Epoxy resins have not yet become known to a process of practical importance. On the one hand, the high curing temperatures and slow curing prohibit the Use of the common halogen-containing, volatile propellants, on the other hand is obtained through the use of easily decomposable polycarboxylic acids. like acbnitic acid. only to foamed resins with a density of 150-200 g / l.

The use of solid blowing agents such as azo-bis-isobutyronitrile is necessary difficult catalytic control of anhydride hardening at the point of decomposition the azo compound and a thorough mixing below 100 ° C and also leads to foamed resins with low thermal resistance. their densities 200 g / l not fall below.

The invention relates to a method for producing foamed Epo. oxide resins, characterized in that polyepoxide compounds with the addition of maleic anhydride and # -pyrones of the general formula (V) where R1, R2, R3 and R4 denote hydrogen, lower alkyl, aryl, carboxyl, carballcoxyl, halogen or alkoxyl, alone or in combination with other carbocyclic anhydrides, in the presence or absence of the curing of catalysing substances to temperatures between 80 and 250 ° C, preferably 105-200 ° C heated.

In general. it is advisable to add 0.5-1.3 per mole of epoxy group preferably 0.5-1.0 mol of malcic anhydride and 0.25-1.3, preferably 0.6- 1.0 moles of α-pyrone or α-pyrone derivative to be used in suitable In some cases, however, it is entirely possible to use other amounts of hardener.

Surprisingly, the known Diels-Alder reaction between maleic anhydride and α-pyrones of the above general formula runs according to the equation even in the melt of the polyepoxide compound in the selected temperature range at such a high rate. that it can compete with the anhydride curing of the polyepoxide compound.

Depending on the choice of reaction temperature, the pyrone derivative and the Presence or absence of Katalyestoren, which the anhydride hardening or catalyze this and the Diels-Alder reaction, the carbon dioxide escapes the thin-fluid melt or drives it up to form a foam. flas procedure is in this way extraordinarily versatile and allowed by its use of the low-melting maleic anhydride without any technical difficulties from foamed epoxy resins increased heat resistance.

The process, the bulky and high-melting anhydride hardener during to build up the hardening itself also brings great technical advantages because on the one hand the love of circumstances Dissolution process of the anhydride high temperatures and, on the other hand, the technically easily accessible, low melting islaleic anhydride is used. The propellant is thereby of supplied to the crosslinker itself, so foaming takes place without the addition of solvents, which reduce the heat resistance, or solids which are poor Allow to spread in the epoxy-anhydride melt.

Suitable α-pyrones of the formula (V) are, for example: 5-methyl- -pyron, the 5-ethyl-α-pyrone; 4,6-dichlorocumalic acid, 4,6-dichlorocumalic acid ethyl ester, α-pyrone-6-carboxylic acid, 6-methyl-α-pyrone-3,5-dicarboxylic acid ethyl ester, 4,6-diphenyl-α-pyrone; 4,5,6-triphenyl C-pyrone, 3-methyl-6-hydroxy-α-pyrone, 5-ethoxy-α-pyrone-6-carboxylic acid, 3-methoxy-i-pyrone-6-carboxylic acid, 3-hydroxy-6-methyl-α-pyrone. This list is incomplete and serves only for illustration the variety of possible derivatives of pyron.

Preference is given to using pyrons which satisfy the general formula (IX): where R1 = B or CH3; R2 = HXCOOH, COO - @@ kyl; R3 = H or CH3, R4 = H, Cl or Br. Examples include α-pyrone, 4,6-dimethyl-α-pyrone,, cumalin @ aurs, ethyl cumalate, methyl cumalate, 3-chloroumalic acid, methyl 3-chloro-cumalate . -Pyron resp.

-Pyronderivatc can be used individually or in the form of mixtures with one another be used.

The polyepoxides used as starting materials are those which can be hardened with anhydrides. Preferred polyglycidyl ethers are those made from polyhydric phenols such as resorcinol, pyrocatechol, hydroquin or polynuclear phenols such as bis- (4-hydroxyphenyl) -1,1-ethane, bis- (4-hydroxyphenyl) -1,1-isobutane, 1,5 -Dihydroxy-naphthalene and novolaks with a molecular weight of 270-1000 are produced by reaction with epichlorohydrin, 1 but in particular polyglycidyl ethers of bis (4-hydroxyphenyl) -2,2-propane, especially compounds of the general formula (X) with n = 0 - 20.

Polyglycidyl ethers of polyvalent aliphatic can also be used or cycloaliphatic alcohols, e.g. trimethylolpropane, glycerol1 or Hexites, 1, i-bishydroxymethyl-ti3-cyclohexene or propylene oxide addition products on trimethylblpropane or pentaerythritol. Also to be mentioned are telomerizates of Allyl glycidyl ethers with compounds containing at least one olefinic double bond such as butadiene, styrene or vinyl acetate.

Furthermore, according to the invention, aliphatic epoxides can be foamed, which result from epoxidation of unsaturated hydrocarbons, ethers, acetals, esters, Acylamines, urethanes, amides or ureas with the usual epoxidizing agents, such as.

Peracetic acid. Mention may be made, for example, Butadiene epoxide telomerizates, telomeric polybutadiene epoxide, epoxidized fatty acid esters of polyhydric alcohols, cycloaliphatic diepoxides such as vinylcyclohexene-3-diepoxide, cyclooctadiene-1,5-diepoxide, cyclododecatriene diepoxide, dicycyclopentadiene hexoxides of the unsubstituted or unsubstituted cycloaliphatic epoxides of the formula in which the cycloaliphatic epoxides of the formula are unsubstituted or substituted cycloaliphatic epoxides or the cycloaliphatic epoxides of the formula desubstituted or polycyclic epoxides of cycloaliphatic diepoxides such as vinyl cyclohexene-3-diepoxides (XI) R = H- or C113 and the 5,211, O-tricyclodecenyl radical of the formula (XII) and especially the substituted or unsubstituted cyclo- $ hexenyl radical of the formula (XIII) R = H or CH3 with one another via hydrocarbon bridges which can be interrupted one or more times by ether, acetal, ester, acylamine, urethane, amide or urea groups or are directly connected via these. Examples include polyepoxides of the lower homopolymers of vinylcyclohexene; 3: 4-Ep.oxyhexaliydrobenzyl-3: 4-epoxyhexahydrobenzoate N: N-bis- (3: 4-epoxy-hexahydrobenzyl) -formamide, N: N'-diacetyl-N: N'-bis- (3: 4- epoxy-hexahydrobenzyl) ethylenediamine; 3: 4-Epoxyhexahydrobenzyl-3 4-epoxy-cyclohexyl carbamate 3: 4-Epoxy-cyclohexyl-1,1-bisoxymethyl-3: 4-epoxy-hexahydrobenzyl acetal; Bis (3: 4-epoxy-2, 5-endomethylene-cyclohexyl) phthalate; 3: 4-epoxy-2, 5-endomethylene-cyclohexyl-3: 4-epoxy-hexahydl-obenzoa t 0, 0 -bis- (2: 3-epoxy-tricyclo-5: 2: 1: 0-decyl) - ethandiol-1,2; 0, 0'-bis (2: 3-epoxy-tricyclo-5: 2: 1: 0) -2,2'-dihydroxy-ethyl ether.

Esters of glycide with epoxidized unsaturated ones are also suitable Fatty acids, as well as 3: 4-epoxy-lexahydrobenzoic acid.

Polyglycidyl esters of die and polycarboxylic acids may also be mentioned.

Weakly basic epoxides, such as those produced by the reaction of epichlorohydrin are accessible with aniline or N, N'-dimethyl-4,4'-diaminodiphenylmethane, can can also be used for foaming; especially as catalytically effective, reactive diluents.

The execution of the reaction is highly dependent on the type of polyepoxide and the substituents on the α-pyrone. All components are put together and melted in the temperature range between 70 and 105 ° C and homogeneously with one another mixed. The low viscosity melt can in the absence of free carboxyl groups or basic agents, such as amines, can be kept at 100 ° C. for any length of time. Included the first stage of the Diels-Alder reaction, the formation of the monoadduct, has already occurred without affecting the viscosity significantly changes. In attendance of known, the anhydride curing of epoxides catalyzing Verbinjdungen, the Hydroxyl, carboxyl, mercaptyl, amino, but advantageously tertiary amine groups the dropping time is limited but still sufficient for processing. When raising the temperature in the range from 120 to 140 ° C, in which the decarboxylation of the Diels-Alder monoadduct with the formation of the reactive cyclohexadiene system subsequent exotic addition of maleic anhydride occurs, steps the anhydride hardening continues so quickly that the carbon dioxide foams the throws up a hardening mixture. By adding pore regulators, e.g. let In this way, foams with a uniform pore structure are obtained. Miss these compounds, which catalyze the anhydride hardening, can be added catalytic amounts of amine, minin-perfluoride complex, mercapto compound or polyol shortly before foaming, with a rise in temperature, hardening and expansion of the foam be coordinated. If this addition is omitted, the liquid can be removed from the liquid Reaction mixture by heating to 135 to 140 ° C most of the carbon dioxide First drive out, after adding the catalyst then pour and form a foam find high density.

Post-curing of the foams takes place in that for anhydride curing in the general usual range between 150 and 2000 C.

The foaming can also take place in the presence of inert substances such as fillers. These include, for example, gravel, fiberglass etc. in question.

The foams obtained in this way are distinguished by a level not previously achieved Heat resistance and can be used as insulating materials in a variety of ways, e.g. in aircraft construction and in electrical engineering.

In the following examples, parts are parts by weight and percentages Weight ¢ percent.

Example 1: de 28.5 parts of a diglycidyl ether on the Besis of Bisphenol-A becomes epoxy equivalent 190 and 75.0 parts epoxy equivalent 500 with 27.45 parts of maleic anhydride, 21.45 parts of isodehydracetic acid and 0.90 parts a pore regulator based on siloxane is transformed into a clear melt and then Held at 105 ° C for 10 minutes, then poured into a preheated mold and at 160 ° C foamed. The semi-rigid foam obtained in this way is post-cured at 160.degree. C. for 14 hours. A solid, fine-pored foam with a density of 67 g / l is obtained 8 hours of treatment at 2000C shows no external signs of change, Example 2: 57.0 parts of a diglycidyl ether based on bisphenol A from Epoxy equivalent is 190 along with 27.45 parts of maleic anhydride, 21.45 Parts of isodehydracetic acid and 0.60 parts of a pore regulator fused and 10 Maintained minutes at 105-110 ° C, then 0.50 parts of a with stirring 10% solution of the cyclohexylamine-boron trifluoride complex in 1,4-butanediol added, Immediately poured into the mold and sealed at 140 ° C. Then 12 hours hardened at 1800C. A brittle, firm and fine-pored foam is obtained. which has a density of 59 g / l and 51% closed pores. After 8 hours Heating at 2000C shows no signs of visible change.

Example 3: 104 parts of a diglycidyl ether based on disphenol-A with an epoxide equivalent of 190 are anhydride with 47.1 1 parts of maleic acid, 44.1 Parts isodehydracetsäureäthylester and 1.5 Share a pore regulator fused and held at 105 ° C for 10 minutes. Then 1.0 parts of a 10% solution of benzyldimethylamine in 1,4-butanediol and heated to 128 ° C heat. After pouring into a preheated mold, it is foamed at 1500C, 4 Leave at this temperature for hours and then at 170 for a further 12 hours C hardened. A fine-pored, solid foam with a density of g / l, the Has 23% closed pores and no signs after 8 hours of heating at 200 ° C the change shows.

Example 4: 29 parts of 3: 4-epoxyhexahydrobenzyl-3: 4-epoxyhexahydrobenzoate of the epoxide equivalent of 145 are 17.6 parts of maleic anhydride, 13.5 parts Cumalic acid ethyl ester and @, 25 parts of a pore regulator fused and at 70 ° C. 0.30 parts of a 10% solution of benzylamine boron trifluoride in 1,4-butanediol added and heated to 11,000. At this temperature, foaming occurs. After 12 hours Post-curing at 7500C gives a foam with a density of 62 gll, which is over 50 % closed pores and no visible change when heated to 180 ° C shows.

Example 5: 52.0 parts of a diglycidyl ether based on bisphenol-A with an epoxide equivalent of 190, with 23.6 parts of maleic anhydride, 45.5 Parts of ethyl 3-chloro-cumalate and 0.75 parts of a pore regulator fused and held at 105 ° C for 10 minutes. Then 0.50 parts of a 10% strength Stirred solution of benzyldimethylamine in 1,4-butanediol and heated to 130.degree. After pouring into a mold, it is foamed at 15,000, 4 hours at this temperature held and cured for a further 12 hours at 1700C. A fine-pored one is obtained Foam with a density of 53 g / l, showing no signs of change when heated to 2000C having.

Example 6: 39 parts of a diglycidyl ether based on bisphenol-A with an epoxide equivalent of 190 and 13 parts of a diglycidyl ether of N, N'-dimethyl-diaminophenylmethane the epoxide equivalent of 195 is combined with 23.6 parts of maleic anhydride and 22 parts of ethyl isodehydracetate and 0.75 parts of a pore regulator fused at 70 ° C, and heated up Foamed at 120 ° C, cured for 4 hours at 150 ° C, 12 hours at 180 ° C. It arises a fine-pored foam with a density of 63 g / l.

Claims (6)

Patent claims: 1) Process for the production of foamed epoxy resins, characterized in that polyepoxy compounds with the addition of maleic anhydride and α-pyrones of the general formula (V) are used. wherein R1, R2, 113 and R4 can be hydrogen, lower alkyl of C1-C10, aryl, carboxyl, carbolkoxyl, halogen, hydroxyl or alkoxyl, alone or in combination with other carbocyclic anhydrides in the presence or absence of catalytic amounts of substances accelerating the curing Temperatures between 80 and 2500C, preferably 100-2000C, heated. 2) Process according to claim 1, characterized in that @ polyepoxide compounds with the addition of male insturearihydride and t-pyrones of the general formula (VIII) where R1 is hydrogen, methyl; R2 is hydrogen, carboxyl or carbalkoxyl; R3 is hydrogen or methyl; R4 can be hydrogen, chlorine or bromine, heated alone or in combination with other carbocyclic anhydrides in the presence or absence of catalytic amounts of substances which accelerate the curing to temperatures between 80 and 250 ° C, preferably 100-200 ° C. 3) Process according to claim 1 and 2, characterized in that one catalytic amounts of amines, preferably tertiary amines, gusetzt. 4) method nncli claim 1 and 2, characterized in that one adds catalytic amounts of the boron trifluoride-amine complex. 5) Method according to claim 1 - 4, characterized in that the polyepox id compounds glycidyl ethers of the general Formula (x) 3 0} crIg CH -CII- CII 0 OCII -CII-CH2-O- 0C11 -CiJ-CiJ 2 2 2 2 0 1! n113 L 3 (x) used with n = 0 - 20. 6) Process according to claim 1 to 1l, characterized in that one uses cycloaliphatic epoxides as polyepoxide compounds.