DE2229907A1 - LIQUID HARDENING AGENTS FOR EPOXY RESINS - Google Patents

Description

2229907 FARBENFABRIKEN BAYER AG

Fr / Pk LEVERKUSEN-Bayeiwerk Central area Patents, trademarks and licenses

June 19, 1972

Liquid hardeners for epoxy resins

The invention relates to liquid mixtures of cyclic dicarboxylic anhydrides which are used as hardeners for polyepoxides be used.

It is known to use liquid dicarboxylic acid anhydrides as curing agents for polyepoxides. For example, dodecenyl succinic anhydride was made recommended for this purpose. This curing agent has the disadvantage of being relatively small Heat resistance of the hardened polyepoxides.

Another liquid hardening agent is methylendomethylene tetrahydrophthalic anhydride known. A disadvantage of this compound is its high viscosity in relation to others liquid hardeners.

Furthermore, methyl hexahydrophthalic anhydride is used as a liquid hardening agent. The high price.

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Isomerized methyl tetrahydrophthalic anhydride has also been suggested as a curing agent. This substance tends to however, after prolonged standing for crystallization, in addition one has to synthesize as in the case of methylhexahydrophthalic anhydride use expensive isoprene that is not always available in pure form.

Mixtures of the isomers of tetrahydrophthalic anhydride only remain liquid for a few days at room temperature (about 20 ^° C.); then they crystallize. The same applies to mixtures of the isomer mixture of tetrahydrophthalic anhydride and hexahydrophthalic anhydride. Depending on the mixing ratio, tetrahydrophthalic anhydride, hexahydrophthalic anhydride or the very sparingly soluble hexahydrophthalic acid always contained in the latter compound crystallize out. Even completely acid-free mixtures of tetrahydrophthalic anhydrides and hexahydrophthalic anhydride show, even after brief contact with the air, which is unavoidable when handling the product, cloudiness and crystallization which can be attributed to precipitating hexahydrophthalic acid. (See British patent specification 914 463 and German laid-open specification 1 917 519).

It was an object of the present invention to provide curing agents for polyepoxides which are liquid and light are accessible and result in curing products with good application properties.

The object was achieved in that mixtures of isomeric tetrahydrophthalic anhydrides and methylhexahydr © phthalic anhydride were produced and used for curing the polyepoxides.

The present invention thus provides a process for the preparation of polyadducts by reacting

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Polyepoxides with mixtures of anhydrides of cyclic dicarboxylic acids, optionally in the presence of curing accelerators, plasticizers, Elastifiziermitteln, fillers, dyes, diluents, pigments and reinforcing materials, characterized in that the mixture of isomerized Tetrahydrophthalsäureanhydriden is having a melting point range of about 5-60 ⁰ C and methylhexahydrophthalic anhydride .

Preferably, the mixture of the dicarboxylic acid of 40-95 wt .-%, in particular 50-70 wt .-% is isomerized Tetrahydrophthalsäureanhydriden having a melting point of about 5-60 ⁰ C and 5-60 wt .-%, in particular 15-50 wt. -96 of methylhexahydrophthalic anhydride.

The curing agents according to the invention are liquid at room temperature and have very low freezing points, show no signs of crystallization after standing for several weeks and can be exposed to air for several hours without showing any crystallization or turbidity. For example, solidifies a mixture of about 70 wt .-% isomerized Tetrahydrophthalsäureanhydriden (melting point 38 ⁰ C) and about 30 wt .-% methylhexahydrophthalic anhydride at about -10 ⁰ C.

The isomeric tetrahydrophthalic anhydrides are generally prepared from butadiene and maleic anhydride, which, after a Diels-Alder reaction, react to give 44-tetrahydrophthalic anhydride. Δ 4-tetrahydrophthalic anhydride can also be converted in a known manner by heating with acidic catalysts into a mixture of the isomers distinguished by the different position of the double bond (ME Bailey and ED Amstutz, Journal of the American Chemical Society, Vol. 78, 1956, III, P. 3828 ff). Mixtures of isomers which are characterized by a melting point between 5 and 60 ° C. are suitable for further use in the production of the liquid curing agent according to the invention.

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Commercially available goods can be used as methylhexahydrophthalic anhydride, as produced by the Diels-Alder reaction of isoprene and maleic anhydride and subsequent hydrogenation.

It is particularly advantageous to use a methyl hexahydrate phthalic anhydride of which about 40-60% by weight, preferably about 50% by weight, consists of the cis-cis-cis and about 40-60% by weight . -%, preferably about 50 wt .-? 6, consists of the cis-cis-trans isomers. This mixture of isomers can be obtained from the products obtained after the hydrogenation specified above by heating in the presence of basic or acidic catalysts at temperatures above 160 ° C.

By stirring with methylhexahydrophthalic anhydride a mixture with a proportion of 5 to 60 percent by weight methylhexahydrophthalic anhydride, preferably 15 to Percent by weight, for example, the claimed liquid curing agent can be obtained very easily.

As polyepoxides, those aliphatic, cycloaliphatic, aromatic or heterocyclic compounds "denotes that on average have more than one epoxy group contained per molecule.

The polyepoxide compounds to be used can be polyglycidyl ethers of polyhydric phenols, for example from pyrocatechol, resorcinol, hydroquinone, from 4,4'-dihydroxydiphenyl methane, from 4,4'-dihydroxy-3,3'-dimethyldiphenylmethane, from 4., 4'- dihydroxydiphenyldimethylmethane, from 4,4'-Dihydroxydiphenylmethylmethan, of 4,4'-dihydroxydiphenyl cyclohexane, of 4,4 · -dihydroxy-3, 3 '-dimethyldiphenylpropan, from 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl sulfone of from Tris (4-hydroxyphenyl) methane, from the chlorination and bromination products of the aforementioned diphenols, from novolaks (ie from conversion

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products of mono- or polyhydric phenols with aldehydes, especially formaldehyde, in the presence of acidic catalysts), from diphenols, which by esterification of.2 moles of the sodium salt of an aromatic oxycarboxylic acid with one mole of a Dihaloalkane or dihalo dialkyl ethers were obtained (see British patent specification 1 017 612), from polyphenols, those resulting from the condensation of phenols and long-chain halogen paraffins containing at least 2 halogen atoms (see British Patent 1,024,288).

The following may also be mentioned: polyepoxide compounds based on aromatic amines and epichlorohydrin, e.g. N-di- (2,3-epoxypropyl) -aniline, N, N'-dimethyl-N, N'-diepoxypropyl-4,4'-diamino-diphenylmethane, N, N'-tetraepoxypropyl-4,4'-diaminodiphenylmethane, N-Diepoxypropyl-4-aminophenyl glycidyl ether (see British patents 772 830 and 816 923).

The following are also possible: glycidyl esters of polyvalent aromatic, aliphatic and cycloaliphatic carboxylic acids, for example phthalic acid diglycidyl ester, adipic acid diglycidyl ester and glycidyl esters of reaction products of 1 mole of an aromatic or cycloaliphatic dicarboxylic acid anhydride and 1/2 mol of a diol or l / n mol of a polyol with η hydroxyl groups or diglycidyl hexahydrophthalate, which can optionally be substituted by methyl groups.

Glycidyl ethers of polyhydric alcohols, for example from 1,4-butanediol, 1,4-butenediol, glycerol, trimethylolpropane, Pentaetythritol and polyethylene glycols can also be used. Of further interest are triglycidyl isocyanurate, Ν, Ν'-Diepoxypropyloxamid, Polyglyeidylthioether from polyvalent thiols, such as from bismercaptomethylbenzene, diglycidyl trimethylene trisulfone.

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Finally, are epoxidation products of polyunsaturated Compounds called, such as vegetable oils and their conversion products, epoxidation products of Di- and polyolefins, such as butadiene, vinylcyclohexene, 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, polymers and

■ s

Copolymers that still contain epoxidizable double bonds contain, e.g. based on polybutadiene, polyisoprene, butadiene-styrene copolymers, divinylbenzene, dicyclopentadiene, unsaturated polyesters, as well as epoxidation products from olefins, which are produced by Diels-Alder addition are accessible and are then converted into or from polyepoxides by epoxidation with per compounds Compounds which contain two cyclopentene or cyclohexene rings linked via bridging atoms or bridging atom groups. In addition, there are polymers of unsaturated monoepoxides called, for example of methacrylic acid glycidyl ester or allyl glycidyl ether.

The following polyepoxide compounds or mixtures thereof are preferably used for the process according to the invention: polyglycidyl ethers of polyhydric phenols, in particular of bisphenol A; Polyepoxy compounds based on aromatic amines, especially bis- (N-epoxypropyl) -aniline, N, N ^f -dimethyl-N, N -diepoxypropyl-4,4 * -diamino-diphenylmethane and N-diepoxypropyl-4- aminophenyl glycidyl ether; Polyglycidyl esters from cycloaliphatic dicarboxylic acids, in particular hexahydrophthalic acid diglycidyl esters and polyepoxides from the reaction product of η moles of hexahydrophthalic anhydride and 1 mole of a polyol with η hydroxyl groups (n = integer from 2-6), in particular of 3 moles of hexahydrophthalic acid anhydride and one mole of 1,1-hexahydrophthalic propane anhydride .

Liquid polyepoxides are also preferably used or low viscosity diepoxides such as bis (nepoxpropyl) aniline or add vinyl cyclohexene diepoxide to increase viscosity

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of already liquid polyoxides to be reduced even further or to convert solid polyepoxides into liquid mixtures.

The hardening takes place by mixing the polyepoxides with the liquid hardening agent according to the invention and, if necessary, others Additives and heating to higher temperatures.

The mixing ratio is expediently chosen so that there is approximately one anhydride group per epoxy group; it can, depending on the desired properties of the polyadducts, more or less liquid hardening agent (about 0.1 to 2 mol of anhydride groups per epoxy group) can also be used. It is also possible to add other other carboxylic acid anhydrides or other hardening agents.

The curing can be carried out at temperatures of about 60 ^° C. to 250 ^° C., preferably at 80 ^° C. to 180 ^° C.

Curing can also occur at any point in time Cooling down to room temperature, for example, is interrupted and continued at a later point in time. Will be expedient the time at which the reaction is interrupted is chosen so that that obtained on cooling to, for example, room temperature Mixture is in the B-stage, i.e. is solid, and when heated later to the temperature of the final hardening becomes liquid again or becomes deformable under pressure. The application of this last-mentioned procedure is special advantageous when laminates, molding compounds and coating compounds, e.g. after the fluidized bed sintering process.

You can add fillers, pigments, dyes, reinforcing materials, such as glass fibers, fabrics or plasticizers as well as mixtures of the above-mentioned additives in order to

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to influence shafts of the polyadducts. The polyadducts Other materials that are important for their function, such as metal parts that carry current or voltage, can also be used Contains components, cast or inserted.

You can also optionally solvents, pigments, coloring and Apply a polyepoxide-hardener mixture containing fillers to various substrates, e.g. by spatula, Brush, dip or spray, and then carry out the crosslinking reaction by heating.

Conventional catalysts such as boron trifluoride adducts or tert. Amines can also be used in amounts of 0.1 to 5% by weight, based on the resin-hardener mixture.

A preferred embodiment of the invention The method consists in that the polyepoxide-Andrisch mixture plasticizers such as polyalkylene polyols, in particular polyalkylene diol, polyalkylene triols or mixtures thereof with molecular weights of about 200 to 4500, preferably from 500 to 2000 are added. This plasticizer can be up to 50% by weight, preferably 2-15 wt .-? 6, based on the anhydride mixture.

The moldings, coatings, bonds, impregnations and films produced by the claimed process have excellent mechanical properties such as high impact and flexural strength at the same time high heat resistance. Because of their good dielectric properties, they are used as electrical insulating materials excellently suited. Shaped bodies in the present application are also understood to mean shaped structures, which are made from casting compounds, molding compounds, laminate molding compounds and glass fiber reinforced laminating resins permit. Such molded bodies are, for example, mechanical and electrical construction elements.

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The technical progress of the carboxylic acid anhydride mixtures according to the invention from isomerized tetrahydrophthalic acid hydrides and methylhexyhydrophthalic anhydride compared to the isomerized tetrahydrophthalic anhydrides (cf. “British Patent No. 914 463) is, on the one hand, a significant improvement in the mechanical properties of the hardening products of a polyepoxide hardening product bisphenol a (epoxide equivalent 185) according to example 4 of British Patent specification 930 kp / cm and the Wärmformbeständigkeit 59 ° C, while isomerized under the same conditions, an inventive anhydride mixture of 60 wt .-% of tetrahydrophthalic anhydride and 40 wt -.% methylhexahydrophthalic anhydride (about 50 wt % cis-cis-cis and 50% by weight cis-cis-trans methylhexahydrophthalic anhydride; cis-trans Iomerism in relation to the methyl group) Flexural strength of approx. 1400 kp / cm and a heat resistance from 117 ° C. On the other hand, the anhydride mixtures according to the invention remain liquid at room temperature (previously tested storage time = 1 year), while the anhydrides according to British patent 914 463 solidify after a few days at room temperature (cf. British patent 914 463, page 2, lines 39-41) .

The percentages given in the examples relate to weight.

Example 1 ;

100 weight Tle.i44-tetrahydrophthalic anhydride are melted at 120 ⁰ C and at this temperature with 1 part by weight Phosphorus pentoxide mixed. While stirring in a stream of nitrogen, the mixture is heated to 200 ° C. for 5 hours and then distilled at 1 torr. The pale yellowish distillate was liquid for several days at room temperature, then gradually crystallized and could be settled by heating

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melted at 3O ⁰ C again. It consists of about 10% from ² -, 20%,
anhydride.

ά ² -, 20% Δ ⁴ -, 30% Λ ¹ - and 40% A ³ tetrahydrophthalic acid

50 wt. Tie. this substance are at 50 ⁰ C once with 50 wt. TIn. Hexahydrophthalic anhydride and once with 50 wt. TIn. Methylhexahydrophthalic anhydride (50% by weight cis-cis-cis isomer) mixed. After cooling to room temperature, the mixture with hexahydrophthalic anhydride is cloudy and has sediment, while the mixture with methylhexahydrophthalic anhydride is completely clear and without sediment.

Example 2 ;

4th
200 weight tie. Δ -Tetrahydrophthalic anhydride are melted at 120 ° C. and at this temperature with 2 wt. Phosphorus pentoxide mixed, then heated to 230 for 30 minutes under nitrogen.

70 parts of the mixture of isomers thus obtained are mixed with 30 parts of methylhexahydrophthalic anhydride (according to Example 1) mixed, then the mixture is distilled at 1 torr.

A clear, almost colorless distillate is obtained which is completely clear and even after standing for 2 hours in an open vessel remains without crystallization symptoms.

Are 70 parts of the isomer mixture obtained according to the above procedure with 30 parts of hexahydrophthalic anhydride (instead of 30 parts of methylhexahydrophthalic anhydride) mixed and the mixture obtained is distilled at 1 Torr, an initially clear distillate is obtained, which after Standing in an open vessel for 2 hours is severely clouded.

Example 3 ;

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200 parts by weight. 4 -Tetrahydrophthalic anhydride are with

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Long heated to 195 ⁰ C and then distilled .in a vacuum at 1 Torr. 190 g of distillate are obtained, which is slightly yellow in color and crystallizes after a short time ^{on storage at 0 ° C.} The isomer mixture now present in solid form can be completely liquefied again at 45.degree.

40 parts by weight. this mixture is once with 60 wt. TIn. Methylhexahydrophthalic anhydride (45% by weight of cis-cis-cis isomer) mixed (mixture A), on the other hand with 60% by weight of tin. Hexahydrophthalic anhydride (mixture B). After standing for 3 days at ⁰ ° C., mixture A is still liquid without any signs of crystallization, while mixture B has crystallized.

Example 4 :

100 parts by weight. of a polyepoxide (epoxide equivalent 185) made from 4,4'-dihydroxydiphenyldimethylmethane and epichlorohydrin have 84 wt. of the mixture of 50 wt. tin described in Example 1. Mixture of the isomers of tetrahydrophthalic anhydride and 50 parts by weight. Methylhexahydrophthalic anhydride (48% by weight cis-cis-cis and 52% by weight cis-cis-trans methylhexahydrophthalic anhydride) and 1 part by weight. Dimethylbenzylamine at 20 ⁰ C mixed.

The reactive liquid mixture obtained in this way has a viscosity of 1400 cP ^{at 20 ° C.} By heating to 80 ^° C. for 4 hours, it hardens to a transparent, yellowish-colored plastic, which is then ^{tempered at 120 °} C. for 15 hours. The determination of the mechanical strengths gave the following values: Flexural strength DIN 53 452 1400 kp / cm ² Compressive strength DIN 53 454 1450 kp / cm ² Tensile strength DIN 53 455 830 kp / cm ² Dimensional stability DIN 53 458 124 ⁰ C in the heat
(Martens)

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Example 5 :

DIN 53 452 700 kp / cm DIN 53 454 2450 kp / cm DIN 53 458 205 ⁰ C DIN 53 480 KA 3c

100 weight parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate having an epoxy equivalent of 135 »were mixed with 95 parts by weight Tin of a mixture of 50 wt .-% isomerized tetrahydrophthalic anhydrides having a melting point of 48 ⁰ C and 50 wt. -% methylhexahydrophthalic anhydride (content of cis-cis-cis-isomers of 53%), one part by weight of benzyldimethylamine, 350 parts by weight Tln quartz flour and 10 parts by weight Tln brown iron oxide was heated to 60 ° C and in a hot metal mold of 8O ⁰ C poured. Then 6 hours at 80 ⁰ C and 15 hours at 18O ⁰ C was cured. A homogeneous, bubble-free molding was obtained which had the following physical properties:

Flexural strength
Compressive strength

Dimensional stability
in the warmth

Tracking resistance

The molded body can be used to produce post insulators for high voltage, switch parts and to enlarge components how capacitors are used.

Example 6 ;

100 weight parts of bis (N-2,3-epoxypropyl) aniline (epoxy equivalent 125) were mixed by weight Tlen-mentioned in Example 5 Anhydridgemisches at room temperature with 120 and cured for 24 hours at 120 ⁰ C.

The molding had the following properties:

Flexural strength DIN 53 452 1100 kp / cm ² Compressive strength DIN 53 454 1520 kp / cm ² Dimensional stability

in the heat DIN 53 458 135 C dielectric strength DIN 53 481 220 kV / cm

Tracking resistance DIN 53 480 KA 3c

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The hardenable casting resin compound can be used, for example, for impregnating paper wound capacitors and for impregnating electrical coils are used.

Example 7 ;

100 parts by weight of diglycidyl hexahydrophthalate (epoxide equivalent 175) were mixed with 93 parts by weight of the anhydride mixtures mentioned in Example 5. and 1.9 weight parts of dimethylbenzylamine were mixed at room temperature and at first for 4 hours at 80 ⁰ C and subsequently cured for 15 hours at 120 ° C. The following physical values were determined on a test body.

Flexural strength compressive strength

Dimensional stability in the heat

Tracking resistance

The molding materials are used for the production of weatherproof transducers. Overhead line insulators and weatherproof Coating compounds suitable for metal objects.

Example 8 :

100 parts by weight of the polyepoxide according to Example 4 and 100 parts by weight of a mixture of 85 parts by weight of the anhydrous mixture according to Example 4 and 15 parts by weight of a polypropylene glycol with a molecular weight of 2000, which is derived from propylene glycol 1.2 as Start component and propylene oxide was prepared as an attachment component, and 2 weight parts of dimethylbenzylamine are mixed at room temperature and cured for 5 hours at 80 ⁰ C and then 15 hours at 120 ° C. The following values were measured on a test body:

DIN 53 452 1470 ο
kp / cm DIN 53 454 1430 kp / cm DIN 53 458 98 ⁰ C DIN 53 480 KA 3c

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DIN H 452 1350 2229907 ρ
kp / cm KA 3c Flexural strength DIN 53 453 31 cm / kg / cm Impact strength DIN 53 455 784 kp / cm tensile strenght DIN 53 455 6.5 % Elongation at break DIN 53 458 95 ⁰ C Dimensional stability
in the warmth DIN 53 481 230 kV / cm Breakthrough
strength DIN 53 480 Leakage current
strength 53

The molding material is particularly suitable for molded parts that are exposed to high impact, bending and stretching loads and must also have a high degree of dimensional stability in terms of heat and rigidity.

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Claims (4)

Claims ; I _{7 A} process for the preparation of polyadducts by reacting polyepoxides with mixtures of anhydrides of cyclic dicarboxylic acids, optionally in the presence of curing accelerators, plasticizers, elasticizers, fillers, dyes, pigments, diluents and reinforcing materials, characterized in that the mixture of isomerized tetrahydrophthalic anhydrides with a range of melting points from about 5 to 60 ⁰ C and methylhexahydrophthalic anhydride. 2. The method according to claim 1, characterized in that the mixture of 40-95 wt .-% isomerized tetrahydrophthalic anhydrides and 5-60% by weight methyl hexahydrophthalic anhydride consists. 3. The method according to claim 1-2, characterized in that the mixture of cyclic dicarboxylic anhydrides in addition to 50 wt .-%, based on the mixture of the curing agent, of polyalkylene glycols with molecular weights of contains about 200 to 4000. 4. A liquid curing agent for polyepoxides from mixtures of the isomers of the tetrahydrophthalic anhydride having a melting point range of about 5 to 60 ⁰ C and cyclic dicarboxylic acid anhydrides, characterized by a content of 5 to 60 wt .- # methylhexahydrophthalic anhydride. Le A 14 499 - 15 - 309882/0775