DE1296341B - Process for the production of electrical insulators consisting of a core and a jacket - Google Patents

Description

The core-sheath construction comes particularly in the manufacture of Outdoor post insulators and fire-proof and explosion-proof insulators of great importance for pits. This is mainly because there is hardly any cast resin molding material that meets the requirements, especially with regard to the surface properties or weather resistance (xenon test, ionization test, fade-ometer test), arc resistance, Resistance to tracking current, resistance to embers as well as mechanical and electrical resistance equally fulfilled and competitively priced with ceramic materials or glass is.

Cast resin components have already been proposed to remedy this deficiency to be provided with a coating of highly fluorinated plastic compounds.

This is intended to protect the component against deterioration of the electrical Surface resistance must be protected from the effects of the weather. The production however, such a coating is relatively difficult. Mainly because the highly fluorinated plastic compounds stick with difficulty.

When the coating is sintered onto the core, such high temperatures must therefore be required are used, which are already in the critical temperature range of Oießharzformstoffe lie.

In addition, there are cast resin insulating bodies built up in layers became known, the individual layers of which are only distinguished by the type and amount of filler differentiate. For the production of these layers a process has become known, at which z. B. the first core poured into a mold, hardened and further Sheathed forms. This process is also relatively cumbersome and time-consuming and therefore expensive. In addition, there is hardly an intimate jointless connection in this way of the individual layers.

The invention relates to a method for producing from core and sheath existing electrical insulators made of curable resin compounds in one Casting mold and is characterized in that a) a first liquid to form the shell Cast resin compound used with a filler content of at least 60 percent by weight which, when cured, have optimal electrical surface properties having, preferably a mixture of a cycloaliphatic epoxy resin or an unsaturated polyester resin with a suitable hardener and with aluminum oxide trihydrate as a filler, b) this first casting resin compound on the inner surface of the casting mold for so long is rotated until one increases against the mold wall or the outer surface of the jacket Compression of the filler occurs, the casting mold for the duration of this rotation process with their central resp.

The axis of rotation is placed horizontally and during the rotation the first casting resin compound is converted into a dimensionally stable state, depending on of their type through partial polymerization, partial polyaddition and / or partial polycondensation, c) the rotation is ended and the mold is placed perpendicular with its central axis is, d) for core formation the stationary and vertically placed casting mold with a second liquid resin compound is filled before the on their Inner surface Layer of the first casting resin has reached its hardened state, as second casting resin compound is chosen which in the cured state a has high mechanical strength, preferably a mixture of an epoxy resin based on bisphenol-A with a suitable hardener and filler, e.g. B. quartz flour, e) the body produced in this way is removed from the mold and, if still necessary, fully cured will.

By means of the method according to the invention, it is possible to make a Core and sheath existing insulator in practically a single casting and hardening process to manufacture. Only a single mold is needed. Their occupancy time can be kept very short. After the coat layer has gelled and hardened, the Casting can already be removed from the mold, even if its core is still liquid. Accordingly can reduce the mold occupancy time and thus the manufacturing process, in particular through Acceleration of gelation and hardening of the top layer can be further shortened. Highly reactive casting resin compounds, especially cycloaliphatic polyepoxides or unsaturated ones During curing, polyesters have exothermic reaction temperatures that are so high that there is a risk of stress cracking, especially for larger castings. This led to the realization that large insulating bodies can only be used with a highly reactive one first casting resin composition can produce if the second casting resin composition of less Reactivity is. By postponing the gelation of the two mixtures (Core, shell) the exothermic reaction can be controlled favorably, whereby the The risk of cracking in the first casting resin compound is avoided.

The production of single or multi-layer hollow bodies in a rotary process has long been known. Next is a method of making double-walled Thermal vessels become known, in which the walls made of thermoplastic material Formed in rotation or centrifugal casting and the gap with foamed plastic is filled out. In all of these known applications of the rotational molding process However, the processing of filler-containing casting compounds is dispensed with because the filler is almost always heavier than the binder and therefore due to centrifugal forces is driven off to the outside, so that an outwardly increasing filler compression arises.

This is precisely what the invention makes use of, since it has been found that Filler densities on insulating jacket surfaces affect the electrical surface properties usually improve.

Another known method of making a multilayer Body made of polymerizable casting resin compositions differs from that according to the invention Method, inter alia, basically in that in this known method each layer is cured before the subsequent layer is poured on, whereas in the case of the subject matter of the invention, the core material before the shell layer has completely cured is applied, d. H. as long as there are still reactive components in the shell compound available.

In the method according to the invention, the casting mold is preferably in front andlor during the application of the first casting resin compound to a temperature warmed, in which this resin compound gels accelerated. Known by this per se Measure, the mold occupancy time can be significantly reduced.

The first casting resin compound is preferably one with a high viscosity used, in particular with a viscosity which is higher than that of the second casting resin compound.

According to a further variant, the two casting resin compounds are related their specific weights so coordinated that the specific weight of the first casting resin compound is equal to or preferably greater than that of the second Cast resin compound.

The viscosity and "or the specific gravity of the two casting resin compounds can at least additionally due to the type and / or amount of the added filler be matched. It should be noted, however, that the type of filler and quantity also influence the mechanical and electrical properties of the insulator. This will be explained in more detail later.

The proportion by volume of the first cast resin compound in the total volume of the insulator is selected according to the desired jacket thickness. Preferably the volume of the jacket or the first resin compound is determined so that it about a third of the total volume.

The electrical and mechanical properties of the jacket and core are primarily determined by the resin used.

The first casting resin compound (jacket) is preferably a cycloaliphatic Epoxy resin material selected, in particular one which is a resin component Cycloaliphatic polyepoxy compound with an average of more than one 1,2-epoxy group per mole, as a curing agent a cycloaliphatic polycarboxylic acid anhydride and as Filler preferably aluminum oxide trihydrate and / or an alkaline earth metal sulfate or carbonate. Such resin compounds result in excellent electrical properties Surface properties, especially high weather resistance, arc resistance, Resistance to tracking current and fire resistance.

On the other hand, unsaturated polyester resins can also be used to form the shell are used, they also give good surface properties.

An epoxy resin is preferably used as the casting resin of the second casting resin compound based on bisphenol A are used, in particular those which are used as resin components one by condensation in the presence of alkali of an epihalohydrin with a The polyglycidyl ether or polyphenol produced, as a hardener a di- or polycarboxylic acid anhydride and preferably contains quartz powder as filler. Preferably a polyglycidyl ether selected which is a solid fusible at room temperature Resin represents. These epoxy resins produce high mechanical and electrical strengths.

As already mentioned, the mechanical and electrical properties depend also strongly depends on the filler used. Have as a filler for the cladding layer in particular aluminum oxide trihydrate and / or alkaline earth metal sulfates or carbonates or the like. Proven. In addition to quartz powder, other mineral ones are also used as core fillers Fillers in question.

Example 1 In a kept at room temperature, with release agent 100 parts of the pretreated post insulator mold were prepared as follows first casting resin mass introduced: In 100 parts 3, 4-Epoxyhexahydrobenzal-3 ', - 4'-epoxy-1', 1'-bis (oxymethyl) cyclohexane with an epoxy content of 6,2 epoxy equivalents 25 parts of "polypropylene glycol P-425" of a polypropylene glycol are produced per kilogram at 800 C with an average molecular weight of 425 and 12 parts of a sodium alcoholate (Accelerator) made by dissolving 0.82 parts of sodium metal at about 1200 C is prepared in 100 parts of 2,4-dioxy-3-oxymethylpentane, and 340 parts of aluminum oxide trihydrate intimately mixed and finely dispersed with 75 parts of hexahydrophthalic anhydride and 6 parts Silicon dioxide mixed (casting resin mixture 1).

After this first casting resin mass by tilting and rotating the mold was distributed as evenly as possible on the inner surfaces, 200 parts of the Second casting resin mass produced as follows in a free jet into the center of the mold or poured between the still uncured first mass adhering to their walls.

100 parts of a polyglycidyl ether resin which is solid at room temperature with an epoxy content of 2.55 epoxy equivalents per kilogram produced by Reaction of epichlorohydrin with bis (4-hydroxyphenyl) dimethyl methane in the presence of alkali at 145 to 1500 C were with 180 parts of a commercially available silicon dioxide with grain sizes 10 to 40 A (quartz powder) and dissolving 30 parts of phthalic anhydride mixed at 125 to 1350 C. This was followed by at a temperature of 1200.degree cured for 24 hours.

The post insulator produced in this way is characterized by excellent mechanical strength and shows, even when under tension, an extraordinary one Weather resistance. According to DIN 53484 for arc resistance (VDE 0303 part 5), the high level L 4 and the tracking resistance (VDE 0303 part 1) T5 reached. According to VDE 0302, a glow resistance was determined for the jacket surface measured at level 4.

Example 2 In a preheated to 1000 C and treated with release agent Post insulator mold was 100 parts of the first made as follows Cast resin compounds at room temperature are introduced.

To 100 parts of a commercially available unsaturated polyester by condensation of 5 moles of isophthalic acid, 1 mole of phthalic anhydride, 6 moles of maleic anhydride and 12.5 moles of propylene glycol (acid number 25) containing 30% styrene 50 parts of a flexibilizing unsaturated polyester, produced by Condensation of 1.3 mol of ethylene glycol, 2 mol of diethylene glycol, 1 mol of maleic anhydride, 1.5 mol of phthalic anhydride and 0.5 mol of adipic acid (SZ 20), which is also 30% styrene contains, as well as 300 parts of aluminum oxide trihydrate, 3 parts of benzene peroxide 50% and 0.5 parts of a 50 / above solution of diethyl aniline in dibutyl phthalate -given and intimately mixed at room temperature.

The support insulator casting mold placed practically horizontally on driven rollers, on which two concentric circular flanges were screwed, were now with rotated such a speed that the casting resin mass by the centrifugal force was evenly distributed and adhered to the inner surface of the mold. After about For 30 minutes, the first casting resin compound had gelled so far that it was now vertical Asked form as described in Example 1 second casting resin in the same Way as in Example 1 could be poured. Subsequently, a Cured at a temperature of 1200 C for 24 hours.

The post insulator produced in this way is characterized by excellent mechanical strength and shows, even when under tension, an extraordinary one Weather resistance. According to DIN 53484 for arc resistance (VDE 0303 part 5), the high level L 4 and the tracking resistance (VDE 0303 part 1) T5 reached.

Example 3 100 parts of a first casting resin mixture, consisting of 100 parts of a polyglycidyl ether resin based on bisphenol A which is liquid at room temperature with an epoxy content of 5.2 equivalents per kilogram, 80 parts of hexahydrophthalic anhydrite, 80 parts of the polypropylene glycol P-425 mentioned in Example 1, 525 parts of aluminum oxide trihydrate, 55 parts of chalk flour and 1 part of the hardening accelerator 2,4,6-tris (dimethylaminomethyl) phenol were intimately mixed at 100 to 1200 C and in a preheated to 1200 C and Cast with release agent treated post insulator casting mold.

The support insulator casting mold placed practically horizontally on driven rollers, on which two concentric circular flanges were screwed, were now with rotated such a speed that the casting resin mass by the centrifugal force was evenly distributed on the inner surface of the mold and adhered. After about For 30 minutes, the first casting resin compound had gelled so far that it was now vertical Asked form filled in 200 parts of the second casting resin composition prepared as follows became.

100 parts of a polyglycidyl ether resin which is solid at room temperature with an epoxy content of 2.55 epoxy equivalents per kilogram, manufactured by Reaction of epichlorohydrin with bis (4-hydroxyphenyl) dimethyl methane in the presence of Al kali at 145 to 1500 C were with 180 parts of a commercially available silicon dioxide with grain sizes 10 to 40 es (quartz flour) and dissolving 30 parts of phthalic anhydride mixed at 125 to 1350 C.

This was followed by at a temperature of 1200 C for 24 hours hardened.

The post insulator produced in this way is characterized by excellent mechanical strength and exhibits extraordinary strength even when under tension Weather resistance. According to DIN 53484 for arc resistance (VDE 0303 parts 5), the high level L 4 and the tracking resistance (VDE 0303 part 1) T5 reached. According to VDE 0302, a glow resistance was determined for the jacket surface measured at level 4.

Claims: 1. Process for the production of core and shell existing electrical insulators made of curable resin compounds in a casting mold, characterized in that a) a first liquid casting resin compound for the formation of the jacket with a filler content of at least 60 percent by weight is used, which has optimal electrical surface properties in the cured state, preferably a mixture of a cycloaliphatic epoxy resin or an unsaturated one Polyester resin with a suitable hardener and with aluminum oxide trihydrate as filler, b) this first casting resin compound is rotated onto the inner surface of the casting mold for so long, until an increasing compression of the mold wall or the outer surface of the jacket Filler occurs, the mold for the duration of this rotation process is placed horizontally with its central or axis of rotation and during the Rotation the first casting resin mass is converted into a dimensionally stable state, depending on their type by partial polymerization, partial polyaddition and / or partial polycondensation, c) the rotation is ended and the mold is placed perpendicular with its central axis is, d) for core formation the stationary and vertically placed casting mold with a second liquid casting resin is filled before the one located on its inner surface Layer of the first casting resin has reached its hardened state, as second casting resin compound is chosen which in the cured state a has high mechanical strength, preferably a mixture of an epoxy resin based on bisphenol-A with a suitable hardener and filler, e.g. B. quartz flour, e) the body produced in this way is removed from the mold and, if still necessary, fully cured will.

Claims (1)

2. The method according to claim 1, characterized in that in per se in a known manner, the casting mold before and / or during the application of the first casting resin compound is heated to a temperature at which this resin compound gels accelerated. 3. The method according to claim 1, characterized in that the first Cast resin compound such a high viscosity is used. 4. The method according to any one of the preceding claims, characterized in, that the specific weight of the first casting resin composition is equal to or greater than that of the second casting resin compound. 5. The method according to claim 4, characterized in that the specific Weights of the two resin compounds due to the size of the filler parts at least can also be voted on. 6. The method according to any one of the preceding claims, characterized in, that a cycloaliphatic polyepoxy compound is used as the resin component for the first casting resin compound with an average of more than one 1,2-epoxy group per mole, as preferred curing agent is a cycloaliphatic die or polycarboxylic acid anhydride and preferably aluminum oxide trihydrate and / or alkaline earth metal sulfate as filler or carbonate is chosen. 7. The method according to any one of the preceding claims, characterized in, that for the second casting resin as a resin component by condensation in the presence of alkali of an epihalohydrin with a die or poly- phenol produced polyglycidyl ether, a die or polycarboxylic acid anhydride as hardener and preferably quartz powder as filler is chosen. 8. The method according to any one of the preceding claims, characterized in, that the quantities of the two casting resin masses introduced into the casting mold are so aligned be matched that the volume of the first resin compound is about one third of the Total volume of the molded body is.