DE2534693A1 - HEAT-TURNABLE, SOLID EPOXY RESIN COMPOSITES - Google Patents

Description

SCHERING AKTIENGESELLSCHAFT

Heat-curable, solid epoxy resin compounds

Addendum to patent (patent application P 21 66 606)

Subject of the main patent (patent application

P 21 66 606) are thermosetting, solid epoxy resin compounds made from

a) liquid di- and / or polyglycidyl ethers of di- and / or polyphenols or from liquid mixtures of these glycidyl ethers with up to 20% by weight , based on the total epoxy resin component, of mono- or diglycidyl compounds, namely glycidyl ethers of mono- or polyvalent Phenols or alcohols or glycidyl esters of mono- or polybasic carboxylic acids

and from

b) anhydrous monomeric cyanamide in amounts of 0.3 to 0.6 mol per epoxy equivalent -

and from

c) accelerators, especially tertiary amines, and optionally from

d) fillers and / or reinforcing agents, in particular fibers or fabrics with, if appropriate, pigments and auxiliaries

by converting to the B state in the temperature range of

INSPECTED

approx. 20 C to approx. 130 C with subsequent cooling.

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The above given from monomers! Cyanamide and liquid epoxy resins However, formulated systems show a relatively high reactivity or a strong temperature dependence of the reactivity. So In the case of impregnation processes, the temperature in the soaking tubs must be kept below 25 C as far as possible, especially at higher temperatures above 40 C, the rapidly increasing exothermicity only with greater effort is to master. Similar exothermic problems arise when in this prior art Solid binders for adhesives, powder coatings and the like. Manufactured in continuous mass production in the B-stage i.e. in systems in which no or only small amounts of heat-absorbing fillers are used.

It has now been found that by combining solid epoxy resins binders thermosetting with cyanamide and accelerators are obtained which on the one hand do not have the above-mentioned problems and on the other hand have a range of properties, which makes them suitable for areas of application that were closed to the previously known binders of this type.

The further development of the thermosetting, solid epoxy resin compounds

according to main patent (patent application P 21 66 606)

is that instead of the

liquid di- and / or polyglycidyl ethers of di- and / or polyphenols or the liquid mixtures of these glycidyl ethers with up to 20% by weight , based on the total epoxy resin component, of mono- or diglycidyl compounds, namely the glycidyl ethers of mono- or polyhydric phenols or alcohols, or glycidyl esters of one or more ^{valent carboxylic} To§ 8 8 6/0 9 9 5

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according to the present invention 2 5 3 A 6 9

solid epoxy resins, made from bisphenols and epichlorohydrin, with epoxy equivalent weights of approx. 400 to approx. 1200

be used.

According to the invention, the temperature range for the transfer to the B-state can be extended to approx. 130 C to approx. 160 C. The thermosetting, solid epoxy resin compositions according to the invention can be used as binders for adhesives, laminates, molding compositions and powder coatings.

Experience has shown that the implementation of epoxy groups with NH or Hardening agents containing NH groups are greatly accelerated by the presence of alcoholic or phenolic OH groups, Surprisingly, however, the hydroxyl groups, some of which are contained in substantial amounts in solid epoxy resins, do not appear to have any accelerating effect on the reaction of epoxy groups with cyanamide. In fact, the opposite is true. It was z. B. Surprisingly found that solid epoxy resins with cyanamide and tertiary amines at z. B. 70 to 100 C can be processed in co-kneaders without problems with regard to the exotherm.

Similar surprising results were obtained with impregnation baths observed. A homogeneous mixture of liquid epoxy resin, cyanamide and small amounts of tertiary amine, as used for the impregnation of glass fabrics, is spontaneously left to stand at room temperature after about 4 hours React through decomposition. In contrast, it shows a homogeneous mixture of a 75% solution of a solid epoxy resin

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in acetone, cyanamide and tertiary amine only a barely noticeable rise in temperature, even if the amount of tertiary Amine is chosen as a relatively high accelerator. After initially observing a certain increase in viscosity after a few hours is, moreover, the viscosity of such a binder solution changes only slightly in the following days.

According to the preceding statements, it is now particularly surprising that according to the invention storage-stable binders can be produced in the B-stage, which at relatively low temperatures of z. B. 110-130 C in a short time, ie within z. B. can be cured up to 30 minutes. Binders that allow such curing conditions have been used for a long time, for. B. sought as adhesives or for so-called fiber-reinforced adhesive prepregs, with which temperature-sensitive substrates such as wood, pretreated polyethylene, ABS plastics (acrylonitrile-butadian-styrene polymers), rigid polyurethane foam and the like. Glued or without the use of additional adhesives with a fiber reinforcement can be provided. According to the invention, not only can heat-curable binders be obtained which meet the requirement for rapid curing at relatively low temperatures, but at the same time a good bond with these substrates, which are critical in terms of adhesive technology, is also achieved.

The thermosetting binders according to the invention can also be used with advantage in z. B. fiberglass fabrics made prepregs are used, from which z. B. base materials for printed circuits can be obtained. Compared to the classic binders for this sector made of solid epoxy resins and dicyandiamide, according to the invention,

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borrowed amounts of solvents can be saved, moreover becomes an excellent interlaminar composite as well as an excellent Copper adhesion achieved.

The binders according to the invention can also be used in other areas of application, such as B. molding compositions, powder coatings are used with advantage.

The thermosetting binders according to the invention are z. B. received, adding solid epoxies, cyanamide and accelerators if appropriate together with fillers, pigments and the like as well as other auxiliaries at temperatures between approx. 60 and approx. 130.degree intimately mixed in the melt and then cooled in a stage prior to the gelation of the melt. About the The selected temperature and residence time can influence the flow behavior or the degree of pre-reaction can be regulated. If desired, can a grinding or granulating process can be connected.

Optionally, solid epoxy resins, cyanamide and accelerators can be used be dissolved in inert solvents, in particular ketones, esters and / or aromatic hydrocarbons. The solution can fillers, dyes, pigments and other auxiliaries are also added will. After applying the solution to substrates to be bonded or coated or after fibrous materials, such as. B. glass fabric, have been impregnated with the solution, the solvent or solvents are preferably removed with the application of heat (up to approx. 160 C) evaporated, whereupon substrates or prepregs coated with the binder according to the invention are obtained.

The solid epoxy resins used according to the invention are known in the art Way either directly from bisphenols, especially di-

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phenylolmethane or diphenylolpropane and epihalohydrins ^ especially epichlorohydrin. You can also from the diglycidyl ethers of bisphenols by reaction with others Kengen of bisphenols in the stoichiometric deficit according to the two-step indirect synthesis (see e.g. H. Lee and K. Neville, Handbook of Epoxy Resins (1967), 2-6 to 2-9). The bisphenols used to produce the epoxy resins can also be used to achieve flame-retardant properties be substituted by halogen atoms, in particular bromine, on the nucleus.

According to the invention, solid epoxy resins with mean epoxy equivalent weights between 400 and 1200 used, which have 2 epoxy groups per molecule. To the heat resistance or chemical resistance of the cured binders according to the invention to increase, small amounts, i. H. up to 15 percent by weight glycidyl ether of novolaks, the "Contain more than 2 epoxy groups per molecule (cf. e.g. H. Lee and K. Neville, see above 2-10 to 2-11).

The amount of anhydrous monomeric cyanamide given above corresponds, expressed in percent by weight, approximately to an amount of up to 7 percent by weight, based on epoxy resins used; preferably 2 to 5 percent by weight is used.

As far as solvents, especially ketones, are used in production the binders according to the invention are also used, the cyanamide in z. B. the same amount of solvent at room temperature be solved. Such solutions of the cyanamide can be obtained by adding small amounts of stabilizers, such as those used, for. Am the German patent application P 24 59 752 are described, are stabilized.

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According to the invention, the basic accelerators used are, in particular, tertiary amines or similarly acting compounds, such as are customary in the epoxy resin sector in conjunction with other hardening agents. From the large number of tertiary amines that can be used, some particularly favorable and easily accessible ones are mentioned below; Triethylamine, diethylmethylamine, tributylamine, Ν, Ν'-tetramethylethylenediamine, dimethyl- and diethylethanolamine, benzyldimethylamine, (dimethylaminomethyl) phenol, tri- (dimethylaminomethyl) phenol and the like. Tertiary amines can also be converted in situ from primary or secondary amines be formed with epoxy compounds and be effective. as
Imidazole and its alkyl or aryl derivatives have proven particularly favorable in the latter case.

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SCHERING AG -8- 2 5 3 A 5 9 example 1

100 parts by weight of a solid epoxy resin based on diphenylolpropane and epichlorohydrin, which has an epoxide value of 0.11, are dissolved in 30 parts by weight of methyl ethyl ketone with heating solved. The solution is at about 23 C with a hardener solution of 3.2 parts by weight of cyanamide and 6 parts by weight of methyl ethyl ketone offset. Then 1.5 parts by weight of benzyldimethylamine stirred in and with the accelerated resin hardener solution obtained in this way, glass roving fabric with a weight per unit area of 320 g soaked. The impregnated fabric web is sent through a drying tower with a dwell time of 3 minutes at 125 C, whereupon a storage-stable prepreg in the B-stage is obtained.

Three layers of this prepreg are heated at 125 C under a special

2
Fish pressed pressure of 10 Kp / cm for 15 minutes. The laminate obtained has flexural strength in the longitudinal direction

2
of 7500 Kp / cm.

If you have a film made of acrylonitrile / butadiene / styrene copolymer, as is customary as a top layer in the ski industry, such good adhesion is achieved that when trying to peel off the foil, breakage occurs in the foil.

Example 2

100 parts by weight of a commercially available diglycidyl ether based on diphenylolpropane and tetrabromodiphenylolpropane, which has an epoxide value of 0.186 and a bromine content of 23 % , are dissolved in parts by weight of acetone. The solution is at room temperature

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(23 C) with a hardener solution of 4.0 parts by weight of cyanamide, 8 parts by weight of acetone and 0.05 part by weight of 2-ethylhexanoic acid added as a stabilizer. The resin / hardener solution obtained can be used for several weeks.

The stabilized resin / coloring solution is 0.8 parts by weight Benzyldimethylamine added and to impregnate a symmetrical

2 glass fiber fabric with a weight per unit area of 200 g / m is used. The soaked fabric web is sent through a drying tower at 155 ° C. with a residence time of 5 minutes. That way will a dry prepreg is obtained in which the binder is in the B-stage.

Eight layers of this prepreg are placed under a specific pressure

ty

of 40 Kp / cm pressed for one hour at 160 ° C. The laminate obtained

2 shows a flexural strength of 6500 Kp / cm, a good behavior in

Solder bath at 260 C and is self-extinguishing. Example 3

100 parts by weight of a ground, solid epoxy resin based on diphenyiolpropane and epichlorohydrin, which has an epoxy value of 0.11 is mixed with 1 part by weight of benzyldimethylamine and 18.5 parts by weight of titanium dioxide pigment in a high-speed mixer mixed. Finally, 3 parts by weight of cyanamide are incorporated.

The powder mixture is passed through a continuous co-kneader with a residence time of approx. 2 minutes. The inlet temperature in the kneader is 60 - 65 C, the temperature in the Middle 78-80 C and the outlet temperature of the mass 96 C.

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The pre-reacted mass exiting as a tape is then ground to a grain size smaller than 90 μ and used as an adhesive powder Bonding of sandblasted test panels according to DIN 53283 under

2
a pressure of about 3 kp / cm is used. After curing for 15 minutes at 130 C or 15 minutes at

2 2

150 C the tensile shear strength is 2.4 Kp / mtn or 3.2 Kp / mm

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Claims (3)

SCHERING AG -11- 25 34 6 claims 1.) Heat-curable, solid epoxy resin compositions made from a) solid epoxy resins, made from bisphenols and epichlorohydrin, with epoxy equivalent weights of approx. 400 to approx. 1200 and off b) anhydrous monomeric cyanamide in amounts of 0.3 to 0.6 mol per epoxide equivalent and off c) accelerators, especially tertiary amines, and optionally from d) fillers and / or reinforcing agents, in particular fibers or fabrics with optionally pigments and Auxiliary materials by converting to the B-stage in the temperature range from approx. 20 ° C. to approx. 130 ° C. with subsequent cooling. 2.) Heat-curable, solid epoxy resin compositions according to claim 1, characterized in that the transition to the B-stage has been carried out in the temperature range from approx. 130 ° C. to approx. 160 ° C. 3.) Use of the thermosetting, solid epoxy resin compositions according to claims 1 and 2 as binders for adhesives, laminates, Molding compounds and powder coatings. 609886/0995