DE2064071C3 - Curable molding compound - Google Patents

Description

20th

The invention relates to molding compositions based on thermosetting synthetic resins for the Production of heat-resistant molded parts are particularly suitable.

Powder of calcined petroleum coke (the term "calcined" means that the coke has ^{been freed from all constituents that can be volatilized up to 1200 0} C at high temperatures) on the one hand has been successful in improving the chemical resistance of cold-curing resole-based products On the other hand, they have been used as fillers for the production of molding compounds for molded parts that are corrosion-resistant and are therefore primarily used in chemical apparatus engineering. The known molding compounds containing petroleum coke are, however, only cured in the cold. They are processed into filter, diffusion plates or the like. Rather, the method is limited in terms of shape

According to DE-OS 19 16 975, oleophilic graphite, which has a specific surface area of at least 20 m ² / g, is used as filler in order to reduce the electrical resistance of the molding compounds.

The invention relates to molding compositions based on thermosetting synthetic resins in the form of melamine-phenol resins with a phenol content of up to 20% by weight, polydiallyl phthalate, epoxy resins, unsaturated polyesters and / or acrylate resins containing hydroxyl or amide groups, characterized in that they contain as fillers at least 4 and "ö at most 50, preferably 15 to 35% by weight, based on the total mass, graphite with a specific surface area of 3 - 5 m ² / g, coke or carbon black with a purity of at least 99%. From These molding compositions can be used to produce molded parts which ^{withstand thermal stress for several days, for example in air at 280 °} C., without practically changing the shape, surface and initial flexural strength. In addition, moldings of the most varied shapes can be produced with these molding compositions Invention therefore also provides the use of the molding compositions for producing moldings, the above 200 ⁰ C, preferably above 250 ° C, resistant.

The coke used according to the invention can be obtained from residues from the large-scale distillation of crude oil and coal tar (petroleum or coal tar pitch coke). Suitable carbon blacks are of aromatic components removed gas and lamp blacks, in particular chemically inert carbon blacks such as carbon black, graphitized used Such carbon blacks may have been previously heated, for example under exclusion of air to temperatures of more than 2000 ⁰ C under a packed bed of coke. Coke is preferably used as filler. The fillers have a purity of at least 99%, & h. they have a content of at least 99% elemental carbon. They behave in the considered temperature range from 200 to over 3000 ⁰ C chemically completely indifferent. Since the fillers according to the invention have a relatively low density, they can be easily incorporated into the resin used in each case.

The fillers are expediently in finely divided form, e.g. B. used as a powder with a grain size of 1 μ to 1000 μ, preferably from 10 to 200 μ The specific surface area can be 3 to 5 m ² / g for the coke types mentioned. The thermal expansion coefficient of these carbon types may be 8 to 9 χ 10- ⁶ / ° C, the thermal conductivity of 6 to 12 cal / cm sec "C (coke) and the pore volume from about 3 to 5% (graphite and coke), respectively. If carbon black is used this expediently has a particle size between 0.08 μ to 0.15 μ and an inner surface of 10 to 15 m ² / g. For graphite, the thermal conductivity is 300 to 600 cal / cm sec "C.

Suitable unsaturated polyester resins are those of the customary structure of saturated and / or unsaturated Diols, e.g. ethylene glycol, propanediol-1,2 or -13, butanediol-1,3 or -1,4, neopentylglycol, 1,4-dimethylolcyclohexane, aromatic diols, such as p-xylylene glycol, methylene propane-1,2-diol, butyne- (2) -diol-1,4 and saturated and unsaturated dicarboxylic acids, e.g. B. fumaric acid or its ester, maleic acid or its Anhydride and ester, succinic acid, adipic acid, suberic acid, sebacic acid, cyclohexane-l ^ -dicarboxylic acid, Phthalic acid, isophthalic acid, terephthalic acid.

Suitable melamine-phenolic resins are those that by known processes from melamine, phenols and aldehydes, e.g. B. formaldehyde, acetaldehyde, furfural, Isobutyraldehyde, unsaturated and / or saturated mono- and dialdehydes, such as acrolein, glyoxal, Crotonaldehyde, and which contain a maximum of 20% phenol.

Suitable epoxy resins are those based on epichlorohydrin and diphenylolpropane and / or methane or higher molecular weight aliphatic compounds, in which the oxirane grouping by subsequent Oxidation was introduced. These can contain up to 20% by weight of phenolic resins, resols and / or novolaks, z. B. those based on phenols and derivatives, e.g. B. phenol, diphenylolpropane or -methane, cresol, xylene, Resorcinol on the one hand and the aldehydes mentioned above.

The curable acrylate resins used according to the invention can be made from copolymers of acrylamide with other acrylic and / or methacrylic acid compounds, preferably acrylic and / or methacrylic acid, or with an alkylene oxide, e.g. B. ethylene oxide, propylene oxide or the like can be produced.

For the preparation of the acrylate resins suitable acids are, for. B, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid as well as half esters of -unsaturated dicarboxylic acids with mono- and / or polyhydric alcohols, for example mosobutyl maleate, mono- (/? - hydroxyethyl) maleate, each separately alone or in a mixture with each other. Suitable ester components of the acrylate resins are, for example, neutral esters of -unsaturated mono- and / or dicarboxylic acids with mono- and / or polyhydric alcohols, e.g. B.
Acrylic acid ethyl ester,
Butyl acrylate,
2-ethylhexyl acrylate,

Methacrylic acid methyl ester, is

Butyl methacrylate,
Ethylene glycol monoacrylic acid ester,
Propylene glycol monoacrylic acid ester,
Ethylene glycol monomethacrylic acid ester,
Propylene Glyfcc '.- monomaleic acid ester, propylene glycol monofumaric acid ester,
Trimethylolpropane monoacrylic acid ester
and the same,

in each case on their own or in a mixture with one another. AJs The acrylate resins contain amide components, preferably acrylic or methacrylic acid amides or their Alkylol derivatives, for example methylolamides. The alkylolamide groups can also be etherified, for example in the form of Methoxygnippen. The curing of such acrylate resins can either only in the warmth and / or in the presence of curing catalysts such as phosphoric acid, toluenesulfonic acid or chloroacetic acid.

For hardening molding compounds based on unsaturated polyesters are useful peroxides, such as

Benzoyl peroxide tert-butyl perbenzoate,
tert-butyl peracetate di-tert-butyl peroxide,
tert-butyl peroctoate, dicumyl peroxide,
tert-butyl perisononanoate,

2,5-dimethyl-2,5-di- (tert-butylperoxy) -hexane and
2,5-dimethyl-2,5-di- (tert-butylperoxy) -hexyne,
used, the peroxide content being about 1 to 3% by weight, based on the total amount.

Molding compounds based on epoxy resins can be used primarily with acid anhydride, as with anhydride of phthalic acid and its partially and totally hydrogenated homologues, pyromellitic dianhydride, 3,6-endomethylene-zd-tetrahydrophthalic acid, Nadic or methylnadic anhydride of the formula so

HC

Il

R-C

H, H,

> —C

Il
ο

(R = H or methyl)

Hexachlorendomethylenetetrahydrophthalic anhydride and maleic anhydride as well as with amines or Amides, e.g. B. ethylenediamine, diethylenetriamine, m-phenylenediamine, 4,4'-diaminediphenylmethane. Dicyandiamide, Amides of long-chain fatty acids, BFr-amine complexes, 2-methylimidazole, dimethylbenzylamine or the like are crosslinked, the proportion of hardeners depending on the nature of the epoxy resins can be varied. These hardeners are generally used in equimolecular amounts, based on the epoxy groups, implemented.

In the production of the molding compounds, for. B. by kneading, a fairly high friction is observed as a result of the use of the fillers according to the invention, which can be varied by using lubricants. This is in many cases, e.g. B. in injection molding processing advantageous.

Suitable lubricants are, for example, higher fatty acids such as stearic acid, metal salts, especially calcium, Aluminum and / or zinc salts of a higher fatty acid, preferably with 16 to 22 carbon atoms and especially stearic acid, fatty acid derivatives in the form of esters, amides, imides, nitriles and / or sulfonates, z. B. also ester waxes of montan acids. Here derivatives of saturated and / or unsaturated fatty acids, the long-chain radical of which has 16 to 24 carbon atoms contains, can be used. In addition, high-molecular substances with molecular weights of 5000 to 50,000, for example silicones or aliphatic compounds such as polyethylene, polypropylene and Suitable for polyisobutylene The friction is thus due to mutual coordination of the amount of elementary Carbon and that of the lubricant controllable. The amount of lubricant is generally 0.1 to 1 % By weight, based on the total mass. At higher carbon contents it is because of the high Friction of the carbon is useful to increase the amount of lubricant up to 2% by weight. Instead of Uniform compounds can of course always also be used in the manufacture of the resins or as additives Mixtures are used.

Due to the thermal stability of the molding compounds, the molding time can be shortened because of the improved thermal conductivity of the fillers the possibility of processing the molding compounds higher temperature - but within the hardening temperature of the synthetic resins - this is the case This fact causes an improved material flow due to the lower viscosity at higher temperatures is effected. This results in a higher throughput

You can also use the synthetic resin in water and / or conventional organic without adverse results Solvent solvents and then the fillers used according to the invention and optionally asbestos and / or add glass fibers or melt the resin first and then the carbons and the Mix asbestos fibers. In addition to the fillers used according to the invention and optionally asbestos and / or glass fibers, the masses can also contain other fillers and / or reinforcing materials, such as Kaolin, talc, wollastonite, but the proportion of carbon in these substances should be at least 20% by weight of the total amount of filler and reinforcing material. Other common additives, such as calcium carbonate, Calcium magnesium carbonate, aluminum oxide, aluminum hydroxide, magnesium oxide, can be found in the Masses to be included.

The molding compositions according to the invention can be used for the production of moldings that can withstand high thermal loads, z. B. those with perfect closed

Surface, especially for electrotechnical purposes, use, since the electrical properties of the products made from the molding compounds as a result of the Carbon-encapsulated insulating synthetic resins are good. In particular, the molding compounds are used for production of isolators, switches, regulators and other electrical components but it is also suitable possible to manufacture moldings that come into contact with corrosive liquids, z. B. vessels, pipes, laminated bodies, parts of heatable or heatable devices, e.g. B. heating plates, bodies or the like.

In the following examples, parts are always parts by weight.

example 1

20 parts of an unsaturated polyester resin made from phthalic anhydride, 1,2-propanediol and maleic anhydride in a molar ratio of 2: 5: 3 are mixed with 14 parts of dicumyl peroxide, 1.5 parts of zinc stearate, 5 parts of triallyl cyanurate, 20 parts of cut glass fiber with a cutting length of 3 mm , 32 parts of kaolin and 20 parts of calcined coal tar pitch coke powder with a grain size of up to 450 μ are mixed well with one another in a premixer for 15 minutes and then ^{homogeneously plasticized in an extruder up to 100 °} C. A soft plastic material is obtained which is at a temperature of at least 140 ^° C. and can be processed under a minimum pressure of 150 kg / cm ² to form molded parts which are thermally stable ^{up to 280 ° C.}

Example 2

A solution of 300 parts of polydiallyl phthalate in 700 parts of acetone is homogenized to a highly viscous mass with 20 parts of tert-butyl perbenzoate, 15 parts of zinc stearate, 350 parts of calcined petroleum coke powder with a particle size of up to 450 μ and 315 parts of kaolin. The mixture obtained is homogenized in a drying oven in 10 minutes freed from the acetone at 80 ° C. A solid, hard product is obtained which is ground in a mill of known design. Moldings obtained therefrom according to the compression molding or injection molding, are after four hours of storage at 280 ⁰ C in air intact

Example 3

22 parts of an epoxy resin made from epichlorohydrin and dipheaylolpropane in a molar ratio of 3: 2 and with one-m epoxy content of 450 parts of oxirane group, 3 parts of diaminodiphenylmethane; Parts zinc stearate, 40 Parts powdery calcined petroleum coke and 35 parts Glass fibers with a cutting length of 6 mm are mixed well with one another in a premixer and then mixed together Injection-molded or plasticized in a heated extrusion press to a homogeneous mass Injection-molded standard bars of dimensions 150 χ 12 χ 10 mm made from this molding compound are according to four hours of thermal exposure in a heating chamber at 300 ° C in air intact ΐ.

The moldings produced according to Examples 1 to 3 were tested The results are shown in the table below.

Physical characteristics Examples 2 3 1 650 850 Flexural Strength, kp / cm ² 700 4.5-5 15-20 Impact strength, kpcm / cm ² 8-10 1.2-1.5 15-20 Notched impact strength, kpcm / cm ² 8-10 125 130 Dimensional stability according to Mariens, C 145 3 2 Resistance to embers, VZ 3 25th 70 Water absorption, mg " ^Λ 65 ΙΟ ¹³ 10 " Surface resistance ¹ , VZ 10 ¹² 10 ¹⁴ 10 ^M. Specific volume resistance, £ 2 cm 10 ¹⁴ 0.01 0.01 Hall. Loss factor, tg » 0.02 example 5 Example 4

220 parts of a 60% strength aqueous solution of a melamine resin, prepared in a molar ratio of melamine : Formaldehyde such as 1: 2 and 400 parts of a 70% strength acetone solution of a copolymer from methacrylic acid methyl ester and acrylamide, polymerized in a molar ratio of 3: 1, 250 parts of petroleum coke powder with a grain size of up to 450 μ and 320 Parts of short fiber asbestos (fiber length 0.1 to 0.5 mm), 15 parts of zinc stearate and 18 parts of one Ester wax mixed as a lubricant at room temperature and after removal of the solvent ground.

Molded parts, dl ·; were produced by the compression molding process, show, after a four-hour thernvschen load at "80 ⁰ C no external changes.

60 parts of a 60% aqueous solution of a melamine resin prepared with the molar ratio

5-, melamine to formaldehyde like 1: 2 and 5fiO parts one 50% solution of a copolymer of methyl methacrylate and oxyethyl methacrylate (Reaction product of methacrylic acid and ethylene oxide) i · ι molar ratio 1: 1 in acetone with 250 parts of powdered calcined petroleum coke with a grain size of up to 450 μ, 320 parts of short-fiber asbestos (Fiber length 0.1 to 0.5 mm), 15 parts of zinc stearate and 18 parts of an ester wax as a lubricant Mixed at room temperature and after removing the

Ground solvent.

In the compression molding process from this molding compound Herge provided moldings remain after a four-hour period thermal BeansDruchune at 280 ° C intact.

7 8

. . (Fiber length 0.1-0.5mm), 15 parts of zinc stearate and 15

Example b parts of a partially saponified ester wax are in one

340 parts of a melamine powder resin, prepared in a powder mixer for 15 minutes and then mixed on a

Melamine: formaldehyde molar ratio as 1: 2.60 parts of the double rolling mill homogenized,

of a phenol novolak (molar ratio phenol: formal-> Molded parts produced by injection molding

dehydration 1: 0.8), 200 parts of petroleum coke powder of the grain size after four hours of thermal exposure

Qe up to 450 μ, as well as 370 parts of short-fiber asbestos at 280 ° C in air do not show any external changes.

Claims (1)

Patent claims: 1. Molding compositions based on thermosetting Synthetic resins in the form of melamine-phenolic resins with a phenol content of up to 20% by weight, polydiallyl phthalate, epoxy resins, unsaturated Acrylate resins containing polyesters and / or hydroxyl or amide groups, thereby characterized in that they are at least 4 and at most 50, preferably 15 to as fillers 35% by weight, based on the total mass, of graphite with a specific surface area of 3-5 mVg, coke or soot with a purity of at least 99%. Z Use of the molding compositions according to claim 1 for the manufacture of molded parts, the above 200 ⁰ C, preferably above 250 ° C, resistant.