JP2015028132A - Epoxy resin composition for cast molding, mold product for high voltage equipment using the same and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for cast molding capable of producing a homogeneous molded body having high electrical insulation properties and high toughness, with excellent molding properties, and having quick curability within a casting temperature range, while securing a long pot life.SOLUTION: An epoxy resin composition for cast molding includes: a bisphenol type epoxy resin; an acid anhydride hardening agent; a hardening accelerator; and an inorganic filler. The hardening accelerator includes three kinds of hardening accelerators having different reaction activity initiation temperature. The amount of the inorganic filler is 40-85 wt.% based on the total resin composition.

Description

  The present invention relates to an epoxy resin composition for cast molding, a molded product for high-voltage equipment using the same, and a method for producing the same.

  Epoxy resins are molded products for high voltage equipment due to their excellent heat resistance, chemical resistance, insulation and adhesion, for example, mold transformers, vacuum circuit breakers, switchgears for insulation equipment, and air in pipelines. It is used for parts such as an insulating member such as an insulating support for an electric power transmission device and other electric devices, an insulating spacer between electric members, or a bushing. However, with the recent advancement of needs, an epoxy resin having a higher function is demanded. In particular, from the viewpoint of increasing work efficiency, rapid curability in the casting temperature range (110 to 160 ° C.) has become a major issue, and the emergence of an epoxy resin material that can cope with this is strongly demanded.

  For the reasons described above, from the viewpoint of cost reduction by improving productivity, the problem of achieving rapid curing and short-time curing of the epoxy resin, which is a cast insulating resin, is extremely important. Studies of resin compositions that increase the curing speed without change are underway.

  Therefore, as a method for containing a highly reactive curing agent, for example, Patent Document 1 discloses an epoxy resin containing an epoxy resin, an alkanolamine compound, and an amine compound having two or more amino groups in one molecule. A composition is disclosed, and Patent Document 2 discloses an epoxy resin composition containing a finely powdered imidazole compound composition and an epoxy resin. The epoxy resin composition of Patent Document 1 is characterized in that the curing rate is high in all temperature ranges and low temperature curability is also exhibited. In addition, the epoxy resin composition of Patent Document 2 is characterized in that the curing speed is dramatically increased around 140 ° C., and the composition is cured in about 1 minute.

JP 2007-246601 A JP 2010-180162 A

However, in high-voltage equipment applications, it is necessary to mix and mix in the temperature range of 50 ° C to 80 ° C, and the resin composition is heated to 110 ° C or higher (casting temperature). It takes several minutes to several tens of minutes to inject into the mold. Therefore, the epoxy resin composition of Patent Document 1 has a problem that the degree of freedom in working time is low and the pot life is short. Further, the epoxy resin composition of Patent Document 2 is cured at the time of injection, and there is a problem that a desired molded product cannot be obtained. Further, the epoxy resin composition of Patent Document 2 has a problem that since the curing reaction rapidly proceeds at 110 ° C. or higher, the internal heat generation is large, and the molded product is likely to have shape abnormalities such as sink marks and voids.
Further, as in these prior arts, by using a primary amine, secondary amine, or imidazole compound as a curing agent, it is possible to increase the curing rate or to exhibit room temperature curability. However, epoxy resin compositions using these curing agents can be used for applications such as adhesives, civil engineering, and construction because their electrical insulation properties decrease due to moisture absorption, but are suitable for insulating members for high-voltage equipment. Absent. In high voltage equipment applications, it can be said that the acid anhydride curing agent is excellent in terms of insulation reliability, and it is essential to increase the curing rate of the epoxy resin composition containing the acid anhydride curing agent.
Accordingly, the present invention has been made to solve the above-described problems, and is a bisphenol-type epoxy resin that has a long track record as a casting resin for high-voltage equipment parts or structures, and acid anhydrides. In epoxy resin compositions that contain a hardener, it ensures both long life (pot life) required for casting operations and internal heat generation that causes molding abnormalities. Cast molding epoxy resin composition capable of shortening the casting molding cycle time by selectively increasing the curing rate in the casting temperature range (110 ° C. to 160 ° C.) which is the set temperature of the mold for molding. The purpose is to provide goods.

  The present inventors have long used an epoxy resin composition containing a bisphenol type epoxy resin, an acid anhydride curing agent, an inorganic filler, and three types of curing accelerators having different reaction activation start temperatures. Discovering that the curing rate in the casting temperature region (110 ° C. to 160 ° C.) can be selectively increased while achieving both time (pot life) and suppression of internal heat generation during curing, and the present invention is completed. It came to.

That is, the present invention is a cast molding epoxy resin composition in which a bisphenol-type epoxy resin, an acid anhydride-based curing agent, a curing accelerator, and an inorganic filler are mixed, and the curing accelerator is A curing accelerator (A) having a reaction activation start temperature not higher than the resin mixing temperature, and a latent curing accelerator having a reaction activation start temperature within a range of ± 20 ° C. with respect to the set temperature of the casting mold ( C) and a latent curing accelerator (B) having a reaction activity start temperature exceeding the resin mixing temperature and lower than the reaction activity start temperature of the latent cure accelerator (C), An epoxy resin composition for cast molding, characterized in that the amount is 40% by weight or more and 85% by weight or less based on the whole resin composition.
The present invention also provides the cast molding epoxy resin composition comprising the acid anhydride curing agent, the curing accelerator (A), the latent curing accelerator (B), and the latent curing accelerator ( C) and a mixture comprising the other components were prepared by mixing, and this cast molding epoxy resin composition was injected into the mold at a pressure of 1 kg / cm ² or more and 20 kg / cm ² or less. It is the manufacturing method of the molded product for high voltage apparatuses characterized by forming by carrying out.
Moreover, this invention is a molded product for high voltage apparatuses characterized by being obtained by an above-described manufacturing method.

  According to the present invention, while having both a long pot life and suppression of internal heat generation at the time of curing, it has high curability in the casting temperature range, excellent moldability, and has high electrical insulation and high toughness. It is possible to provide an epoxy resin composition for cast molding that can provide a simple resin molded product. Since the casting molding cycle time can be shortened by using the epoxy resin composition for casting molding of the present invention, the productivity of the molded product can be increased.

It is a figure which shows the investigation method of the reaction activity start temperature of the hardening accelerator in embodiment of this invention. It is a figure which shows the relationship between the heating time when the resin composition which mix | blended the accelerator (1-3 types) is heated at 130 degreeC, and the resin internal temperature of center part. It is a figure which shows the relationship between the heating time when a resin composition which mix | blended the accelerator (1-3 types) was heated at 130 degreeC, and a cure rate. It is a figure which shows the relationship between the heating time when the resin composition which adjusted the quantity of accelerator was heated at 130 degreeC, and a cure rate. It is a figure which shows the pot life of the epoxy resin composition obtained in Examples 1-2 and Comparative Examples 1-4. It is a figure which shows the cure rate of the epoxy resin composition obtained in Examples 1-2 and Comparative Examples 1-4. It is a figure which shows the cure rate of the epoxy resin composition obtained in Examples 3-5.

Embodiment 1 FIG.
The epoxy resin composition for cast molding according to the embodiment of the present invention is a mixture of a bisphenol type epoxy resin, an acid anhydride curing agent, a specific curing accelerator, and an inorganic filler, By selectively increasing the curing rate in the casting temperature range (110 ° C. to 160 ° C.) while achieving both a long pot life (pot life) and suppression of internal heat generation during curing, the resin composition gold It is characterized by shortening the casting molding time of mold injection → primary curing → mold release.

  As the bisphenol type epoxy resin used in the embodiment of the present invention, known ones can be used. Specific examples of the bisphenol type epoxy resin include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, brominated bisphenol A type epoxy resin, brominated bisphenol F type epoxy resin, and brominated bisphenol AD. Type epoxy resin. These bisphenol-type epoxy resins may be used alone or in combination of two or more. Among these, a bisphenol type epoxy resin that is liquid at 60 ° C. or lower is preferable because it can be uniformly mixed with other raw materials such as a curing agent, and among them, an epoxy equivalent of 100 g / eq or more and 300 g / eq or less is particularly preferable. A bisphenol-type epoxy resin having is preferable. In addition, even if it is a solid epoxy resin at 60 degrees C or less, if it melt | dissolves in the epoxy resin or acid anhydride type hardening | curing agent which is liquid at 60 degrees C or less, it is possible to use together. In addition, an epoxy resin other than the bisphenol type epoxy resin, for example, an alicyclic epoxy resin, a brominated alicyclic epoxy resin, a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, a bromine, and the like within the range not impairing the effects of the present invention. Phenol novolac epoxy resin, brominated cresol novolac epoxy resin, hydrogenated bisphenol A epoxy resin, heterocyclic epoxy resin such as triglycidyl isocyanate and hydantoin epoxy may be used in combination.

As the acid anhydride curing agent used in the embodiment of the present invention, a known carboxylic acid anhydride can be used. Specific examples of the acid anhydride-based curing agent include, for example, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol trimellitic anhydride, biphenyltetracarboxylic anhydride Aromatic carboxylic acid anhydrides such as products, anhydrides of aliphatic carboxylic acids such as azelaic acid, sebacic acid, dodecanedioic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, chlorendic anhydride, highmic acid anhydride Product (nadic acid anhydride), alicyclic carboxylic acid anhydrides such as hydrogenated nadic acid anhydride, and acid anhydrides having substituents such as alkyl groups in the structure of these acid anhydrides. These acid anhydride curing agents may be used alone or in combination of two or more. Among these acid anhydride-based curing agents, acid anhydride-based curing agents that are liquid at 60 ° C. or lower are preferable because they are easily mixed uniformly with other raw materials such as epoxy resins. In particular, many alkyl group-substituted products are liquid at room temperature and are effective in terms of uniform mixing. For example, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic acid anhydride, hydrogenation Methyl nadic acid anhydride, trialkyltetrahydrophthalic acid anhydride, and dodecenyl succinic acid anhydride are preferred.
The compounding amount of the acid anhydride curing agent is usually equivalent to the equivalent ratio of carboxyl group to the epoxy group of the bisphenol type epoxy resin (including the epoxy group of the epoxy resin when using an epoxy resin other than the bisphenol type epoxy resin) , 0.3 to 1.5, and preferably 0.5 to 1.2. When the blending amount of the acid anhydride curing agent is less than the amount in which the equivalent ratio of the carboxyl group to the epoxy group of the epoxy resin is 0.3, the heat resistance may be inferior, whereas the amount to be 1.5 If it is large, the pot life may be shortened.

As the curing accelerator used in the embodiment of the present invention, any compound can be used as long as the reaction activity start temperature satisfies a predetermined condition and has an action of promoting the curing of the acid anhydride curing agent. Specific examples of curing accelerators include tertiary amines, tertiary amine salts, boric acid esters, Lewis acids, organometallic compounds, organophosphorus compounds, quaternary ammonium salts, quaternary phosphonium salts, amine complexes. , Imidazole compounds, and compounds containing transition metals such as titanium and cobalt. From these, three types of curing accelerators having different reaction activity start temperatures are selected and blended into the epoxy resin composition. When (A), (B) and (C) are used in order from the lowest reaction activity start temperature, (A) is a curing accelerator having a reaction activity start temperature below the resin mixing temperature when kneading the raw materials. And (C) is a latent curing accelerator having a reaction activation start temperature within a range of ± 20 ° C. with respect to the set temperature of the casting mold corresponding to the curing temperature, and (B) is It is a latent curing accelerator having a reaction activation start temperature that exceeds the resin mixing temperature and is lower than the reaction activation start temperature of the curing accelerator (C). These curing accelerators may be selected from those that do not inhibit each other's reaction activity.
Moreover, the compounding quantity of these hardening accelerators totals (A)-(C), and when the epoxy resin other than bisphenol type epoxy resin is used together with 100 weight part of bisphenol type epoxy resin (the epoxy resin is also included) ) Is preferably 0.01 parts by weight or more and 3.0 parts by weight or less, and more preferably 0.02 parts by weight or more and 2.0 parts by weight or less. If the blending amount of the curing accelerator is less than 0.01 parts by weight with respect to 100 parts by weight of the bisphenol type epoxy resin, the effect of promoting the curing reaction may be inferior. Life may be shortened. In addition to the above-described three types of curing accelerators, other curing accelerators may be added in order to finely adjust the curing acceleration.

  Also, by increasing the blending amount of the latent curing accelerator (C) over the blending amount of the latent curing accelerator (B), the reaction rate in the low temperature region is increased by adding the latent curing accelerator (C). And the influence on the decrease in pot life can be suppressed.

  The reaction activation start temperature of the curing accelerator can be known by investigating the temperature at which the viscosity of the resin is increased and the heat generation temperature of the resin. For example, as shown in FIG. 1, the viscosity in a viscoelastic spectrum (temperature-viscosity curve) of a resin mixture obtained by mixing an epoxy resin and an acid anhydride curing agent and a resin mixture obtained by adding a curing accelerator to the resin mixture. It can be found by comparing the rising curves. As can be seen from FIG. 1, in the resin mixture to which the curing accelerator is added, the inflection point of the increase in viscosity is shifted to a lower temperature side than the resin mixture to which the curing accelerator is not added, and the temperature corresponding to the inflection point is The reaction activation temperature is reached. The reaction activation start temperature of the curing accelerator does not have a unique value, but varies depending on the type and amount of the epoxy resin, the curing agent, the inorganic filler, and other additives. .

  When the resin composition mixed in the temperature range of 50 ° C. to 80 ° C. is injected into a casting mold preheated in the casting temperature range (110 ° C. to 160 ° C.), the heat from the mold In response, the temperature rises gradually. By adding three kinds of curing accelerators (A), latent curing accelerators (B) and latent curing accelerators (C) having different reaction activation start temperatures, (A) It is activated in the order of (B) and (C), and exhibits catalytic action. As a result, the reaction-promoting action derived from each accelerator progresses stepwise, thereby increasing the reaction rate and suppressing the rapid resin curing (polymerization) reaction, increasing internal heat generation during curing. Can be suppressed. In molding by pressure gel casting, if the resin internal temperature at the time of curing is below the mold set temperature + 70 ° C. (measured in a resin with a thickness of 100 mm), it is possible to prevent the occurrence of shape abnormality (sink) in the molded product. Tend. Considering the variation at the time of casting, it is more preferable that the resin internal temperature at the time of curing is set to the mold setting temperature + 60 ° C. or less in order to prevent sink marks.

  Resin composition containing only one kind of accelerator so that the pot life at 60 ° C. is 2 hours or more, and resin composition containing two kinds of accelerators having different reaction activation start temperatures Or after mixing the resin composition (this invention) which mix | blended three types of accelerators from which reaction activity start temperature differs at 60 degreeC, it puts into a metal container with a diameter of 100 mm and a height of 200 mm, and heats when it heats at 130 degreeC The relationship between time and the resin internal temperature at the center is shown in FIG. In the case of a general fast-curing resin in which the amount of a curing accelerator having a reactive activity at a low temperature is increased, a tendency specific to rapid curing in which the resin internal temperature rises in a short time is observed, but the resin internal temperature is 230 ° C. As a result, sink marks are generated in the molded product, or a viscosity increase due to a rapid reaction causes a shape abnormality in which voids remain inside or on the surface. In addition, in the case of a general fast-curing resin, an increase in viscosity is observed from the beginning of heating, and it can be indirectly seen that the pot life is short. When two kinds of accelerators having different reaction activity starting temperatures were used, one inflection point was present in the rising curve of the resin internal temperature, and three kinds of accelerators having different reaction activity starting temperatures were used. In the case (the present invention), there are two inflection points in the rising curve of the internal temperature of the resin, and it can be seen that curing is accelerated step by step. From the behavior of the resin internal temperature, it can be seen that the curing rate increases even when two kinds of accelerators are used, but significantly increases when three kinds of accelerators are used. In addition, the resin composition containing three types of accelerators has the same maximum resin internal temperature as the resin composition containing one or two types of accelerators. Thus, it can be seen that a resin internal temperature (die set temperature + 70 ° C. or lower) that can prevent sink marks is secured. Furthermore, it can be seen indirectly that a resin composition containing three kinds of accelerators has a small increase in viscosity at the beginning of heating and a long pot life (pot life). It takes several minutes to complete the resin filling into the mold set at the high primary curing temperature. If the viscosity increase due to curing is high during filling, insufficient filling or shape abnormality occurs. Therefore, a material design having a retarding property of curing such that the curing rate of the resin (= increase rate of internal heat generation) is small until the filling of the mold is completed and increases after completion of the filling is necessary. That is, the resin composition containing the three types of accelerators (invention) can reduce the curing rate during filling by adjusting the amount of the accelerator, such as reducing the amount of the low-temperature activity accelerator. As described above, it is possible to develop a retarding property that is not found in general fast-curing resins, and to make it difficult for shape abnormality to occur during molding.

  In addition, the casting process of the casting mold epoxy resin composition includes (1) injection of the epoxy resin composition into the casting mold, (2) primary curing, and (3) casting mold. And (4) secondary curing. In the secondary curing, molds that have been released from molds are put in a heating oven in a lump, and heat-treated at a temperature equal to or higher than the primary curing temperature (setting temperature of the casting mold), and completely cured. The secondary curing conditions are the primary curing temperature or higher and the thermal decomposition temperature of the epoxy resin or lower, that is, 110 to 180 ° C., until the resin composition is completely cured. The heating time may be a time for completing the curing, but preferably 5 hours to 24 hours. (1) to (3) are casting molding cycles. To shorten the cycle time, it is effective to shorten the primary curing time. When the ratio of the glass transition point after primary curing to the glass transition point of the molded product after secondary curing is the curing rate (%) [= glass transition point after primary curing / glass transition point after secondary curing × 100]. The degree of cure after primary curing required for releasing from the casting mold is preferably 50% or more, and preferably 60% or more to prevent deformation during the mold release operation.

  Resin composition containing only one kind of accelerator so that the pot life at 60 ° C. is 2 hours or more, and resin composition containing two kinds of accelerators having different reaction activation start temperatures Or after mixing the resin composition (this invention) which mix | blended three types of accelerators from which reaction activity start temperature differs at 60 degreeC, it puts into a metal container with a diameter of 100 mm and a height of 200 mm, and heats when it heats at 130 degreeC FIG. 3 shows the relationship between time and the cure rate at the center. In the resin composition containing one or two kinds of accelerators, there is a difference in the time to reach the maximum value of the curing rate, but there is no significant difference in the value. On the other hand, in the resin composition (invention) containing three kinds of accelerators, the curing rate curve is shifted to the short time side and the high curing rate side as a whole, and the tendency of monotonous increase is maintained. . This means that the rapid increase in viscosity is suppressed, and it has the effect of preventing void defects in the molded product, while shortening the curing time and curing while ensuring a long pot life (pot life). This indicates that it is possible to achieve both an increase in rate.

Moreover, as shown in FIG. 4, it reacts at low temperature with the resin composition which mix | blended two types of promoters from which reaction activity start temperature differs so that the pot life at 60 degreeC may be 2 hours or more. As can be seen from the comparison between the resin composition having an increased amount of the curing accelerator having an activity and the resin composition having an increased amount of the curing accelerator having a reaction activity at a high temperature, the accelerator having a reaction activity at a low temperature or a high temperature. Even if the amount is adjusted, the maximum value of the curing rate does not increase, and the curing rate tends to increase remarkably in a region where the heating time is short. This means that the viscosity of the resin increases rapidly, which makes it difficult for voids contained in the resin to escape, resulting in defects that remain on the surface and inside of the molded product, and the pot life (pot life). ) Is not preferable.
As described above, by using three kinds of accelerators having different reaction activation start temperatures as in the present invention, casting can be performed while achieving both a long pot life (pot life) and suppression of internal heat generation during curing. It is possible to provide a homogeneous resin molded product that has rapid curability in the temperature region and excellent moldability, and has high electrical insulation and high toughness.

  In the epoxy resin composition for cast molding according to the embodiment of the present invention, 40 wt% or more and 85 wt% or less of the inorganic filler is blended with respect to the entire resin composition, and therefore, the viscosity is high at room temperature and mixing Can not do it. Therefore, the resin composition is surely injected to a level at which the viscosity of the resin composition can be injected into the casting mold, specifically, 40000 mPa · s or less, especially to the details of the casting mold having a complicated structure. When suppressing the generation of voids on the surface of the molded product or inside, it is preferable to lower it to 20000 mPa · s or less, and it is necessary to set the resin mixing temperature so as to ensure the viscosity. The set resin mixing temperature is preferably 50 ° C. or higher and 80 ° C. or lower in order to ensure the pot life of the resin composition.

  Since it is necessary to select a curing accelerator (A) that is in an active state at the above resin mixing temperature, it is preferable to select a curing accelerator having a reaction activation start temperature of 70 ° C. or lower. Since the curing accelerator (A) has an action of accelerating the polymerization reaction of the epoxy resin at the resin mixing temperature, the polymerization reaction of the epoxy resin proceeds during the mixing operation, and the viscosity increases. It is preferable to secure 2 hours or more from the mixing operation to the injection operation into the casting mold. For example, when the resin mixing temperature is 60 ° C., the pot life of the epoxy resin composition is defined as the time from the start of mixing at 60 ° C. until the viscosity of the epoxy resin composition doubles. The Since the curing accelerator (A) is reactive at the time of resin mixing, increasing the blending amount increases the viscosity at the time of mixing and shortens the pot life (pot life). Therefore, the blending amount of the curing accelerator (A) is preferably set to an amount within a range where this pot life can ensure 2 hours or more. Since the curing accelerator (A) has a function of advancing the polymerization reaction of the epoxy resin at a low temperature, the epoxy resin composition is activated at the time of mixing. Therefore, since the polymerization proceeds before the epoxy resin composition is injected into a casting mold heated to 110 ° C. or higher, since a rapid polymerization reaction does not occur after the injection, the amount of heat generation is reduced. It plays a role in suppressing the occurrence of abnormalities (sink marks and voids) in the molded product.

  The latent curing accelerator (C) is a compound whose reaction activity initiation temperature is within a range of ± 20 ° C. with respect to the set temperature (corresponding to the curing temperature) of the casting mold. This temperature range is close to the temperature of the heated casting mold, and selectively and effectively increases the curing rate of the epoxy resin composition in the casting temperature region. In order to increase the curing rate more selectively, a latent curing accelerator (C) having a reaction activation start temperature within a range of ± 10 ° C. with respect to the set temperature of the casting mold may be selected. Moreover, before the latent curing accelerator (C) is activated, the polymerization reaction of the epoxy resin composition has already proceeded considerably due to the activation of the curing accelerator (A) and the latent curing accelerator (B). . That is, most of the reactive groups involved in the polymerization are consumed and the curing rate is high. Due to the polymerization reaction due to the promoting action of the curing accelerator (A) and the latent curing accelerator (B), the molecular chain is long, so the electron density of the remaining reactive groups is considerably reduced, and the activity is remarkably high. It is falling. The latent curing accelerator (C) is active in such a situation, thereby promoting the polymerization of the remaining reactive groups and increasing the curing rate in a short time. The suitable range of the reaction activation start temperature of the latent curing accelerator (C) is 110 ° C. or higher and 160 ° C. or lower which is a general curing temperature of an epoxy resin composition containing an epoxy resin and an acid anhydride curing agent. It is. Further, in addition to making a clear difference in function with the latent curing accelerator (B), it does not cause an increase in reaction rate and a decrease in pot life in the low temperature region, so that the latent curing accelerator (C) and It is preferable that the difference in reaction activity start temperature with the latent curing accelerator (B) is 10 ° C. or more.

  The latent curing accelerator (B) has a reaction activity initiation temperature that exceeds the resin mixing temperature and is lower than the reaction activity initiation temperature of the latent curing accelerator (C). An epoxy resin composition heated to the resin mixing temperature is injected into a casting mold heated to a curing temperature (casting temperature) and molded. The set temperature of the casting mold is finely adjusted depending on the type of epoxy resin composition and the thickness of the molded product, but it is generally used for epoxy resin compositions containing an epoxy resin and an acid anhydride curing agent. In particular, it is within the range of 110 ° C. or higher and 160 ° C. or lower. Accordingly, the upper and lower limits of the reaction activation start temperature of the latent curing accelerator (B) vary depending on the resin mixing temperature and the setting temperature of the casting mold, but the preferred range of the reaction activation start temperature is 70 ° C. It is 110 degrees C or less. Since the curing accelerator (A) is active at the resin mixing temperature, the curing reaction is promoted at the time of resin mixing, but the latent curing accelerator (B) is a casting mold heated to 110 ° C. or higher. It plays the role of promoting the curing reaction after the epoxy resin composition is injected into the mold. When the latent curing accelerator (B) becomes reactive, the epoxy resin composition has already been cured (polymerized) due to the reactive activity of the curing accelerator (A). is decreasing. Since the molecular weight is increased by polymerization, the remaining reactive groups have a reduced electron density and a low activity, but the latent curing accelerator (B) is activated to increase the curing rate. it can. Since the activation temperature of the curing accelerator (A) is different from the activation temperature of the latent curing accelerator (B), the polymerization is accelerated in stages, and the latent curing accelerator (B) is activated. In this case, since a rapid polymerization reaction does not occur, the curing rate can be increased while suppressing a rapid increase in the internal temperature of the resin. In order to make a clear difference in the function with the curing accelerator (A), it is preferable that the difference in reaction activity start temperature between the curing accelerator (A) and the latent curing accelerator (B) is 10 ° C. or more.

  As the three types of curing accelerators used in the embodiment of the present invention, that is, the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C), the following compounds are listed. Of these, those having a reaction activity start temperature satisfying a predetermined condition may be appropriately selected.

  Examples of the tertiary amine include lauryl dimethylamine, N, N-dimethylcyclohexylamine, N, N-dimethylbenzylamine, N, N-dimethylaniline, (N, N-dimethylaminomethyl) phenol, 2,4. , 6-Tris (N, N-dimethylaminomethyl) phenol, 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), 1,5-diazabicyclo [4.3.0] nonene-5 ( DBN).

  Examples of the tertiary amine salt include the above-mentioned tertiary amine carboxylates, sulfonates, and inorganic acid salts. Examples of the carboxylate include salts of carboxylic acids having 1 to 30 carbon atoms (particularly 1 to 10 carbon atoms) such as octylate (particularly salts of fatty acids). Examples of the sulfonate include p-toluenesulfonate, benzenesulfonate, methanesulfonate, and ethanesulfonate. Typical examples of the tertiary amine salt include salts of 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) (for example, p-toluenesulfonate, octylate). .

  Examples of borate esters include trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and cyclic borate ester compounds.

  The Lewis acid may be a compound having a property of accepting an electron pair (including a transition metal compound), but in addition to boron, aluminum, gallium, indium, thallium, titanium, zinc, tin, scandium, ytterbium, A compound containing any element of vanadium, chromium, manganese, cobalt, nickel, iron, and copper is preferable as a characteristic.

  Examples of the organometallic compound include zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, aluminum acetylacetone complex, and the like.

  Examples of the organic phosphorus compound include tetraphenylphosphonium / tetraphenylborate and triphenylphosphine.

  Examples of quaternary ammonium salts include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, and tetrabutyl bromide. Examples include ammonium, tetrabutylammonium iodide, triethylbenzylammonium chloride, triethylbenzylammonium bromide, triethylbenzylammonium iodide, triethylphenethylammonium chloride, triethylphenethylammonium bromide, triethylphenethylammonium bromide, and the like.

  Examples of the quaternary phosphonium salt include tetrabutylphosphonium chloride, tetrabutylphosphonium iodide, tetrabutylphosphonium acetate, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, tetraphenylphosphonium iodide, ethyltriphenylphosphonium chloride, odor Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium acetate, ethyltriphenylphosphonium phosphate, propyltriphenylphosphonium chloride, propyltriphenylphosphonium bromide, propyltriphenylphosphonium iodide, butyltriphenyl chloride Examples thereof include phosphonium, butyltriphenylphosphonium bromide, and butyltriphenylphosphonium iodide.

  Examples of the amine complex include a boron halide amine complex which is a complex of a boron halide and an amine compound such as boron trifluoride, boron trichloride and boron tribromide. Examples of the amine compound include aliphatic tertiary amines such as trimethylamine, tri-n-propylamine, N, N-dimethyloctylamine and N, N-dimethylbenzylamine, and aromatics such as N, N-dimethylaniline. Tertiary amines, 1-alkylated substituted or unsubstituted imidazole or pyridine heterocyclic tertiary amines such as monoethylamine and n-hexylamine primary aliphatic amines, benzylamine and other aromatic rings Aliphatic primary amines containing, aromatic primary amines such as aniline, secondary amines such as piperidine, and the like. Representative examples of the boron halide amine complex include boron trifluoride monoethylamine complex, boron trifluoride diethylamine complex, boron trifluoride isopropylamine complex, boron trifluoride chlorophenylamine complex, boron trifluoride-tri Allylamine complex, boron trifluoride benzylamine complex, boron trifluoride aniline complex, boron trichloride monoethylamine complex, boron trichloride phenol complex, boron trichloride piperidine complex, boron trichloride dimethyl sulfide complex, boron trichloride N, N -A dimethyloctylamine complex, a boron trichloride N, N-dimethyldodecylamine complex, a boron trichloride N, N-diethyldioctylamine complex, etc. are mentioned.

  Examples of imidazole compounds include 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1- Benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,4-diamino-6 (2′-methylimidazole (1 ')) Ethyl-s-triazine, 2,4-diamino-6 (2'-undecylimidazole (1')) ethyl-s-triazine, 2,4-diamino-6 (2'-ethyl, 4-methyl) Imidazole (1 ′)) ethyl-s-triazine, 2,4-diamino 6 (2′-methylimidazole (1 ′)) ethyl-s-triazine isocyanuric acid adduct, 2-methylimidazole isocyanuric acid 2: 3 adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-3 , 5-dihydroxymethylimidazole, 2-phenyl-4-hydroxymethyl-5-methylimidazole, 1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethylimidazole and the like.

Among the above compounds, as the curing accelerator (A), a tertiary amine having a reaction activation start temperature at 70 ° C. or lower can be used more preferably. The latent curing accelerator (B) includes tertiary amine salts, quaternary ammonium salts, quaternary phosphonium salts, imidazole compounds, and boron halides having a reaction activation start temperature of 70 ° C. or higher and 110 ° C. or lower. Those selected from the group consisting of amine complexes can be used more preferably. Further, as the latent curing accelerator (C), tertiary amine salts, quaternary ammonium salts, quaternary phosphonium salts, imidazole compounds and halogens having a reaction activation start temperature at 110 ° C. or higher and 160 ° C. or lower are used. Those selected from the group consisting of boron bromide amine complexes can be used more preferably.
In particular, the latent curing accelerator (B) and the latent curing accelerator (C) can be selected from different types of groups, and high curing acceleration can be obtained by giving a clear difference in reactivity depending on temperature. . For example, as the latent curing accelerator (B), a tertiary amine salt, a quaternary ammonium salt, a quaternary phosphonium salt, and an imidazole compound having a reaction activation start temperature at 70 ° C. or higher and 110 ° C. or lower are used. As the latent curing accelerator (C), it is more preferable to use a boron halide amine complex having a reaction activation start temperature at 110 ° C. or higher and 160 ° C. or lower.

As an inorganic filler used for embodiment of this invention, the well-known material used for the epoxy resin composition for cast molding can be used. Specific examples of the inorganic filler include, for example, silica (crystalline silica and fused silica), alumina, talc, clay, calcium carbonate, calcium silicate, titanium dioxide, silicon nitride, aluminum hydroxide, aluminum nitride, boron nitride, and glass. , Barium sulfate, magnesia, beryllium oxide, mica, magnesium oxide and the like. The shape of the inorganic filler is preferably crushed or spherical, but may be substantially spherical, aggregated, scaly, fibrous, milled fiber, whisker or the like. These inorganic fillers may be used alone or in combination of two or more. Among inorganic fillers, silica powder, alumina powder, magnesia powder, short glass fibers, and glass beads can be preferably used because they have high electrical insulation.
The blending amount of the inorganic filler should be an amount that can be uniformly mixed at a resin mixing temperature that can secure a pot life of the resin composition of 2 hours or more in a range of 40 wt% to 85 wt% with respect to the entire resin composition. However, it is preferably 50% by weight or more and 70% by weight or less based on the entire resin composition. When the blending amount of the inorganic filler is less than 40% by weight, the mechanical strength of the molded product is inferior. On the other hand, when it exceeds 85% by weight, the resin component cannot be uniformly mixed and the reproducibility of the molded product characteristics cannot be obtained. .

  Moreover, you may add a thermoplastic resin, a rubber component, various oligomers, etc. to an epoxy resin composition in order to improve the crack resistance of the molded product obtained, or to improve impact resistance. Specific examples of the thermoplastic resin include butyral resin, polyamide resin, aromatic polyester resin, phenoxy resin, MBS resin (methyl methacrylate / butadiene / styrene copolymer), ABS resin (acrylonitrile / butadiene / styrene copolymer), It can be modified with acrylic resin, silicone oil, silicone resin, silicone rubber, fluororubber and the like. Various plastic powders, various engineering plastic powders, and the like may be added to the epoxy resin composition.

  Furthermore, an anti-settling agent and a dispersant for preventing settling in an epoxy resin composition of an adhesion imparting agent and a coupling agent, an inorganic filler, and a solid powder for improving adhesiveness, and preventing generation of voids. Antifoaming agents, paint fixing agents, antioxidants, flame retardants, colorants, thickeners, thickeners, surfactants, and the like may be added to the epoxy resin composition.

  The epoxy resin composition for cast molding according to the embodiment of the present invention can be manufactured using a mixing device having a temperature control function. If a mixing device such as a forced mixing mixer, a self-revolving mixer, or a universal mixer is used, the resin component and the inorganic filler can be uniformly mixed. The resin mixing temperature may be a temperature at which the pot life, which is the time until the viscosity of the epoxy resin composition for casting molding doubles, can be secured for 2 hours or more, but is 50 ° C. or more and 80 ° C. The following is preferred. The viscosity of the epoxy resin composition is preferably 40000 mPa · s or less at the mixing temperature. When the viscosity of the epoxy resin composition is higher than 40000 mPa · s, the epoxy resin composition is not injected to the details of the casting mold, and a desired molded product cannot be obtained. The viscosity of the epoxy resin composition can be lowered by blending a lower viscosity epoxy resin. In order to judge the suitability of the epoxy resin composition, in particular, the viscosity at 60 ° C. is 40,000 mPa · s or less, particularly 20000 mPa · s or less is preferable to suppress generation of voids on the surface or inside of the molded product, and the pot life at that temperature It is recommended that the value be 2 hours or longer.

  In order to suppress generation of voids in the molded product, the mixed epoxy resin composition is preferably subjected to a vacuum degassing treatment at a mixing temperature before being cast into a mold. The epoxy resin composition after the vacuum degassing treatment is injected into a casting mold heated to 110 ° C. to 160 ° C., which is the temperature at which the curing reaction of the epoxy resin composition proceeds, and then the pressure gelation method or vacuum casting Molding is performed by the mold method. The set temperature of the casting mold is preferably in the range of 110 ° C. or higher and 160 ° C. or lower. However, when the temperature is high, the curing time is shortened, but shape abnormalities such as sink marks and voids tend to occur. In the vacuum casting method, since the vacuum state is maintained at a high temperature, the liquid raw material constituting the epoxy resin composition may volatilize. Therefore, the set temperature of the casting mold is more preferably 130 ° C. or higher and 140 ° C. or lower from the viewpoint of suppressing shape abnormality and preventing raw material volatilization. In addition, secondary curing after mold release from the casting mold is performed at a temperature equal to or higher than the set temperature of the casting mold, and there is no adverse effect such as deformation or deterioration of the molded product. Although it may be temperature, it is preferably 200 ° C. or lower.

  The change in the curing rate of the epoxy resin composition can be grasped by measuring the gelation time with a gel time tester. If the difference between the gelling time at the set temperature of the casting mold and the gelling time at a temperature 10 ° C. lower than the set temperature of the casting mold is 5 minutes or more, the molded product will sink. And shape abnormalities such as voids are unlikely to occur. Since the sample amount when measuring with a gel time tester is as small as 1 g, the curing time that can be released when casting with an actual casting mold is expected to be about 2 to 3 times the gelling time. There is a need. Further, in order to shorten the casting molding cycle time within 20 minutes, it is preferable that the gelation time at the set temperature of the casting mold is 3 minutes or more and 10 minutes or less.

In order to ensure the pot life of the epoxy resin composition, it comprises an acid anhydride curing agent, a curing accelerator (A), a latent curing accelerator (B), and a latent curing accelerator (C) before use. It is good to divide and store in two, a mixture and a mixture composed of other components. At the time of use, these mixtures are mixed with a mixing device to prepare an epoxy resin composition for cast molding, and the cast epoxy resin composition is cast at a pressure of 1 kg / cm ² or more and 20 kg / cm ² or less. Then, it is poured into a casting mold preheated to a set temperature and molded. In addition to preventing molding abnormalities such as voids (bubbles) in the molded product and the occurrence of sink marks, pressure is applied until the resin component in the casting mold completely gels for the purpose of increasing production efficiency. It is preferable to form by a pressure gelation method in which the material is continuously added and solidified in a short time. The pressure gelation method can control the reactivity of the epoxy resin composition and can suppress the occurrence of molding abnormality.

  Further, as a molding method other than the pressure gelation method, the epoxy resin composition is injected in a reduced pressure state into a casting mold preheated to a set temperature in a sealed container, and then no pressure is applied. A vacuum casting method for curing in a curing furnace may be employed. Even in the vacuum casting method, it is possible to prevent the inclusion of voids (bubbles) in the molded product. When a vacuum casting method is employed as a molding method for the epoxy resin composition for casting molding according to the embodiment of the present invention, a significant improvement in productivity as in the pressure gelling method cannot be expected. Compared to the case of molding the epoxy resin composition, the effect of shortening the molding time due to an increase in the curing rate can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by these. Examples 1 and 2 and Comparative Examples 1 to 4 are examples in which the composition was adjusted assuming that the curing time at a casting temperature of 130 ° C. (setting temperature of the casting mold) was shortened. is there. Examples 3-5 use bisphenol-type epoxy resins and acid anhydride curing agents different from those in Examples 1-2 to selectively increase the curing time at a casting temperature of 130 ° C to 150 ° C. This is an example of composition adjustment.

[Example 1]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as acid anhydride curing agent: 85.5 parts by weight, fused silica as inorganic filler: 150 parts by weight, 2,4,6-Tris (N, N-dimethylaminomethyl) phenol (reactive at room temperature) as curing accelerator (A): 0.2 part by weight, as latent curing accelerator (B) Octylate of 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) (reaction activation starting temperature is about 100 ° C.): 0.3 part by weight, and latent curing accelerator (C) Boron trifluoride monoethylamine complex as (reaction activity start temperature is about 120 ° C.): 0.2 parts by weight is mixed at 60 ° C. for 15 minutes, and then vacuum degassed to form an epoxy resin composition for cast molding It was prepared. The viscosity change of this epoxy resin composition at 60 ° C. was as shown in FIG. 5, and the time until the viscosity doubled (pot life) was 4.3 hours.

  Moreover, about the epoxy resin composition of Example 1, the gelation time at the time of setting a shaping | molding temperature to the temperature of 90-150 degreeC was measured with the gel time tester (No.153 by Yasuda Seiki Seisakusho). The measurement results are shown in FIG. This gel time tester is a device that measures the gelation time of a thermosetting resin composition. The rotor that rotates in a test tube containing the thermosetting resin composition generates a certain amount of torque that accompanies the gelation. The time until it falls off via the coupling mechanism is measured as the gelation time. The mold release time in the cast molding operation does not match the gelation time at that temperature and differs depending on the thickness of the molded product, but empirically 1.5 times to 2 times the gelation time. It tends to be about 5 times longer.

  As FIG. 6 shows, the temperature change (gelation curve) of the gelation time about the epoxy resin composition of Example 1 is about 120 degreeC or more, and the gelation rate is Comparative Examples 1-4 mentioned later. The inflection point (about 127 ° C.) is slightly higher than the reaction activation start temperature of the latent curing accelerator (C), and near the casting temperature ( 125 to 150 ° C.), the reaction was selectively accelerated. It can be seen that this gelation behavior is different from the behavior in which the gelation time monotonously decreases as in the comparative example. Further, the gelation time at 130 ° C., which is the casting temperature, is 8 minutes, which is significantly shorter than the comparative example described later.

Cast molding was carried out using the epoxy resin composition of Example 1. That is, the epoxy resin composition of Example 1 was poured at a pressure of 5 kg / cm ² into a casting mold heated to 130 ° C. while maintaining the temperature at 60 ° C., and 15 minutes by the pressure gelation method. After heat-curing and releasing from the casting mold, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. It was confirmed that there were no shape abnormalities such as voids and sink marks in the molded product. Thus, by using the epoxy resin composition of Example 1, a primary curing time of around 60% was obtained as compared with an epoxy resin composition of a comparative example described later while securing a pot life of 2 hours or more. It was possible to shorten it.

[Example 2]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as acid anhydride curing agent: 85.5 parts by weight, fused silica as inorganic filler: 150 parts by weight, 2,4,6-Tris (N, N-dimethylaminomethyl) phenol (reactive at room temperature) as curing accelerator (A): 0.2 part by weight, as latent curing accelerator (B) 1-cyanoethyl-2-methylimidazole (reaction activity start temperature is about 100 ° C.): 0.2 part by weight, and boron trifluoride monoethylamine complex (reaction activity start temperature as latent curing accelerator (C)) Is about 120 ° C.): 0.4 parts by weight were mixed at 60 ° C. for 15 minutes, and then vacuum degassed to prepare an epoxy resin composition for cast molding. The difference from Example 1 is that the blending amount of the latent curing accelerator (C) is larger than the blending amount of the latent curing accelerator (B). The change in viscosity of this epoxy resin composition at 60 ° C. was as shown in FIG. 5, and the time until the viscosity doubled (pot life) was 4.0 hours.

  For the epoxy resin composition of Example 2, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 6, the temperature change of the gelation time for the epoxy resin composition of Example 2 is that the gelation rate has rapidly increased from around 125 ° C., and the inflection point is also 130 ° C. The behavior was clearly present at 3 ° C. higher than Example 1. The gelation time at 130 ° C., which is the casting temperature, was 6 minutes, which was 2 minutes shorter than Example 1.

Cast molding was performed using the epoxy resin composition of Example 2. That is, the epoxy resin composition of Example 2 was poured at a pressure of 5 kg / cm ² into a casting mold heated to 130 ° C. while maintaining the temperature of 60 ° C., and 12 minutes by the pressure gelation method. After heat-curing and releasing from the casting mold, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. It was confirmed that there were no shape abnormalities such as voids and sink marks in the molded product. From this, by controlling the compounding ratio of the latent curing accelerator (B) and the latent curing accelerator (C), the inflection point of the gel time change can be controlled and the reaction rate in the casting temperature range. It was found that selectivity can be improved.

[Comparative Example 1]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as acid anhydride curing agent: 85.5 parts by weight, and fused silica as inorganic filler: 150 parts by weight Were mixed at 60 ° C. for 15 minutes, and then vacuum degassed to prepare a cast molding epoxy resin composition. The difference from Example 1 is that the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C) were not added. The change in viscosity of this epoxy resin composition at 60 ° C. is as shown in FIG. 5, and the time until the viscosity doubles (pot life) is 6 hours, which is enough time for the casting operation. there were.

  With respect to the epoxy resin composition of Comparative Example 1, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 6, the gelation curve of the epoxy resin composition of Comparative Example 1 was a behavior that monotonously decreased with increasing temperature. The gel time at a casting temperature of 130 ° C. was 35 minutes.

Cast molding was performed using the epoxy resin composition of Comparative Example 1. That is, while keeping the epoxy resin composition of Comparative Example 1 at a temperature of 60 ° C., it was poured into a casting mold heated to 130 ° C. at a pressure of 5 kg / cm ² and heat-cured by a pressure gelation method. As a result, 80 minutes were required for curing to a state where the mold could be released. After mold release, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. Since the curing rate was slow and the temperature rise due to heat generation during curing was relatively small, no abnormalities of voids or sink marks were observed in the molded product after release.

[Comparative Example 2]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as acid anhydride curing agent: 85.5 parts by weight, fused silica as inorganic filler: 150 parts by weight, Octylate of 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) (reaction activity starting temperature is about 100 ° C.): After mixing 0.7 parts by weight at 60 ° C. for 15 minutes Then, vacuum degassing was performed to prepare an epoxy resin composition for casting molding. The difference from Example 1 is that, instead of the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C), 1,8− as the latent curing accelerator (B) is used. Only dioctabicyclo [5.4.0] undecene-7 (DBU) octylate was added. The viscosity change of this epoxy resin composition at 60 ° C. is as shown in FIG. 5, and the time until the viscosity doubles (pot life) is 3.5 hours, which is sufficient for the casting operation. There was time.

  For the epoxy resin composition of Comparative Example 2, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 6, the gelation curve of the epoxy resin composition of Comparative Example 2 is a behavior that monotonously decreases with temperature in the same manner as in Comparative Example 1, and clearly changes as in the Examples in the casting temperature region. There were no inflection points, and a significant improvement in reactivity in the casting temperature region was not obtained. The gelation time at 130 ° C., which is the casting temperature, was 22 minutes.

Cast molding was performed using the epoxy resin composition of Comparative Example 2. That is, while maintaining the epoxy resin composition of Comparative Example 2 at a temperature of 60 ° C., it was poured into a casting mold heated to 130 ° C. at a pressure of 5 kg / cm ² , and heat-cured by a pressure gelation method. As a result, it took 48 minutes to cure to a state where it could be released. After mold release, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. Since there was a lot of temperature rise due to heat generation during curing, sink marks in the molded product after mold release were observed.
As in this comparative example, when only one type of curing accelerator is added, the polymerization reaction proceeds at a stroke when the reaction activation start temperature is reached, so that sudden heat generation is likely to occur. This heat generation accelerates the curing reaction. Depending on the shape and thickness of the molded product, abnormal shapes such as sink marks and voids are caused in the molded product.
On the other hand, when a curing accelerator having a reaction activity starting temperature different from low temperature, medium temperature and high temperature is added in a formulation that can ensure a pot life of 2 hours or more as in the examples, the curing accelerator functions from the low temperature side. However, since the resin temperature gradually rises and the polymerization reaction of the resin gradually proceeds, the temperature rise due to heat generation during curing is suppressed.

[Comparative Example 3]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as an acid anhydride curing agent: 85.5 parts by weight, fused silica as an inorganic filler: 150 parts by weight, 2 , 4,6-Tris (N, N-dimethylaminomethyl) phenol (reactive at room temperature): 0.5 part by weight, and 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) Octylate (reaction activity start temperature is about 100 ° C.): 0.5 part by weight was mixed at 60 ° C. for 15 minutes, and then vacuum degassed to prepare an epoxy resin composition for cast molding. The difference from Example 1 is that instead of the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C), the reaction rate in the casting temperature region is increased, so that the curing acceleration It is that only the agent (A) and the latent curing accelerator (B) were added in an amount within a range where the pot life can be secured. The change in viscosity at 60 ° C. of this epoxy resin composition is as shown in FIG. 5, and the time until the viscosity doubles (pot life) is 2.0 hours, which is a level at which the casting operation can be performed. there were.

  For the epoxy resin composition of Comparative Example 3, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 6, the gelation curve of the epoxy resin composition of Comparative Example 3 is a behavior that monotonously decreases with temperature, and there is no clear inflection point as in the example in the casting temperature range. The remarkable reactivity improvement in the casting temperature region was not obtained. The gel time at a casting temperature of 130 ° C. was 17 minutes.

Cast molding was performed using the epoxy resin composition of Comparative Example 3. That is, the epoxy resin composition of Comparative Example 3 was poured at a pressure of 5 kg / cm ² into a casting mold heated to 130 ° C. while maintaining the temperature of 60 ° C., and heat-cured by a pressure gelation method. As a result, it took 40 minutes to cure to a state where the mold could be released. After mold release, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. The molded product was excellent in that the curing exothermic temperature was suppressed by the addition of the curing accelerator (A), and the molded product released from the mold had no shape abnormality.
As in this comparative example, when the two types of curing accelerator (A) and latent curing accelerator (B) were optimized within a range where a pot life of 2 hours at 60 ° C. could be secured, It is not possible to achieve mold release in such a short time (15 minutes).

[Comparative Example 4]
Bisphenol A type epoxy resin (epoxy equivalent: 190 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as acid anhydride curing agent: 85.5 parts by weight, fused silica as inorganic filler: 150 parts by weight, 2,4,6-tris (N, N-dimethylaminomethyl) phenol (reactive at room temperature): 0.2 part by weight, and boron trifluoride monoethylamine complex (reaction activity starting temperature is about 120 ° C. A): After mixing 0.5 parts by weight at 60 ° C. for 15 minutes, vacuum degassing was performed to prepare an epoxy resin composition for cast molding. The difference from Example 1 is that instead of the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C), the curing accelerator (A) and the latent curing accelerator (C ) Only. The viscosity change of this epoxy resin composition at 60 ° C. is as shown in FIG. 5, and the time until the viscosity doubles (pot life) is 4.8 hours, which is sufficient for the casting operation. There was time.

  For the epoxy resin composition of Comparative Example 4, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 6, the gelation curve of the epoxy resin composition of Comparative Example 4 is a behavior that monotonously decreases with temperature, and there is no clear inflection point as in the example in the casting temperature region. The remarkable reactivity improvement in the casting temperature region was not obtained. The gelation time at the casting temperature of 130 ° C. was 19 minutes, and it did not become short despite the increase in the latent curing accelerator (C).

Cast molding was performed using the epoxy resin composition of Comparative Example 4. That is, while keeping the epoxy resin composition of Comparative Example 4 at a temperature of 60 ° C., it was injected at a pressure of 5 kg / cm ² into a casting mold heated to 130 ° C. and heat-cured by a pressure gelation method. As a result, it took 47 minutes to cure to a state where the mold could be released. After mold release, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. The molded product was excellent in that the curing exothermic temperature was suppressed by the addition of the curing accelerator (A), and the molded product released from the mold had no shape abnormality.
When two types of curing accelerator (A) and latent curing accelerator (C) are added as in this comparative example, the temperature of the epoxy resin composition injected into the casting mold is gradually increased. Although the reaction activation start temperature of the latent curing accelerator (C) is high, the polymerization of the epoxy resin at the time of the temperature rise is slow, and release in a short time (15 minutes) as in Example 1 is achieved. I can't do it.

[Comparative Example 5]
In place of 85.5 parts by weight of methyltetrahydrophthalic anhydride of Example 1, 20 parts by weight of polyethylene polyamine was mixed at 60 ° C., and gelled in the middle of mixing to form an epoxy resin composition for cast molding. The product could not be prepared. This is because the room temperature curable aliphatic amine is used as the curing agent, so that the curing speed is dramatically increased, but the exothermic reaction is high and the pot life is remarkably shortened. The epoxy resin composition as in this comparative example is not suitable for molding applications for high voltage equipment that requires a certain working time.

Example 3
Bisphenol A type epoxy resin (epoxy equivalent: 210 g / eq): 100 parts by weight, methyl nadic anhydride as an acid anhydride curing agent: 80 parts by weight, fused silica as an inorganic filler: 130 parts by weight, curing accelerator N, N-dimethylcyclohexylamine (reactive at room temperature) as (A): 0.3 part by weight, 1-benzyl-2-methylimidazole (reaction activity start temperature as latent curing accelerator (B)) Is about 80 ° C.): 0.2 part by weight, and boron trifluoride diethylamine complex as the latent curing accelerator (C) (reaction activation start temperature is about 125 ° C.): 0.5 part by weight After mixing at 60 ° C. for 15 minutes, vacuum degassing was performed to prepare an epoxy resin composition for cast molding. When the change in viscosity at 60 ° C. of this epoxy resin composition was measured, the time until the viscosity doubled (pot life) was 4 hours.

  For the epoxy resin composition of Example 3, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 7, the temperature change of the gelation time for the epoxy resin composition of Example 3 is a clear inflection point near the reaction activation start temperature (130 ° C.) of the latent curing accelerator (C). The gelation time at 140 ° C., which is the casting temperature, was 6 minutes.

Cast molding was performed using the epoxy resin composition of Example 3. That is, the epoxy resin composition of Example 3 was poured at a pressure of 8 kg / cm ² into a casting mold heated to 140 ° C. while maintaining the temperature at 60 ° C., and 10 minutes by the pressure gelation method. After heat-curing and releasing from the casting mold, secondary curing was performed at 155 ° C. for 12 hours to obtain a molded product. When the molded product was observed, it was confirmed that there were no shape abnormalities such as voids and sink marks.

Example 4
Bisphenol F type epoxy resin (epoxy equivalent: 170 g / eq): 100 parts by weight, methyltetrahydrophthalic anhydride as an acid anhydride curing agent: 80 parts by weight, crystalline silica as an inorganic filler: 150 parts by weight, curing acceleration N, N-dimethylbenzylamine as an agent (A) (reactive at room temperature): 0.1 part by weight, tetraphenylphosphonium bromide as a latent curing accelerator (B) (reaction activity start temperature is about 90 ° C.): 0.2 part by weight, and boron trichloride N, N-diethyldioctylamine complex as the latent curing accelerator (C) (reaction activation start temperature is about 125 ° C.): 0.3 After mixing parts by weight at 60 ° C. for 15 minutes, vacuum degassing was performed to prepare an epoxy resin composition for cast molding. When the change in viscosity at 60 ° C. of this epoxy resin composition was measured, the time until the viscosity doubled (pot life) was 5 hours.

  For the epoxy resin composition of Example 4, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 7, the temperature change of the gelation time for the epoxy resin composition of Example 4 is a clear inflection point near the reaction activation start temperature (128 ° C.) of the latent curing accelerator (C). The gelation time at 140 ° C., which is the casting temperature, was 6 minutes.

Cast molding was performed using the epoxy resin composition of Example 4. That is, the epoxy resin composition of Example 4 was poured at a pressure of 10 kg / cm ² into a casting mold heated to 140 ° C. while maintaining the temperature at 60 ° C., and 10 minutes by the pressure gelation method. After heat-curing and releasing from the casting mold, secondary curing was performed at 145 ° C. for 16 hours to obtain a molded product. When the molded product was observed, it was confirmed that there were no shape abnormalities such as voids and sink marks.

Example 5
Bisphenol AD type epoxy resin (epoxy equivalent: 175 g / eq): 100 parts by weight, trialkyltetrahydrophthalic anhydride as an acid anhydride curing agent: 85 parts by weight, alumina as an inorganic filler: 300 parts by weight, curing acceleration (N, N-dimethylaminomethyl) phenol (reactive at room temperature) as agent (A): 0.1 part by weight, 1-cyanoethyl-2-methylimidazole as latent curing accelerator (B) The reaction activation start temperature is about 100 ° C.): 0.2 part by weight, and boron trichloride monoethylamine complex as the latent curing accelerator (C) (reaction activity start temperature is about 125 ° C.): 0. After mixing 3 parts by weight at 60 ° C. for 15 minutes, vacuum degassing was performed to prepare an epoxy resin composition for cast molding. When the change in viscosity of this epoxy resin composition at 60 ° C. was measured, the time until the viscosity doubled (pot life) was 4.5 hours.

  For the epoxy resin composition of Example 5, the gelation time was measured in the same manner as in Example 1. The measurement results are shown in FIG. As shown in FIG. 7, the temperature change of the gelation time for the epoxy resin composition of Example 5 is a clear inflection point near the reaction activation start temperature (125 ° C.) of the latent curing accelerator (C). The gelation time at a casting temperature of 140 ° C. was 7 minutes.

Cast molding was performed using the epoxy resin composition of Example 5. That is, the epoxy resin composition of Example 5 was poured at a pressure of 4 kg / cm ² into a casting mold heated to 140 ° C. while maintaining the temperature at 60 ° C., and 15 minutes by the pressure gelation method. After heat-curing and releasing from the casting mold, secondary curing was performed at 150 ° C. for 16 hours to obtain a molded product. It was confirmed that there were no shape abnormalities such as voids and sink marks in the molded product.

Example 6
An insulating rod in which an electrode was embedded was molded under the casting conditions of the epoxy resin composition of Example 1. The secondary curing time after mold release was 16 hours at 135 ° C. Using this insulating rod, the breakdown electric field was measured and found to be 60 kV / mm, which was equal to or higher than that of a general-purpose casting resin for high-voltage equipment. In addition, after conducting a heat cycle test (100 ° C. to −30 ° C., 100 cycles), it was confirmed that there was no cracking and that there was no change in molding properties such as insulation properties, mechanical properties, and heat resistance properties. Proven to be a long-term reliable cast insulator.

Example 7
An insulating spacer was molded using the epoxy resin composition of Example 5 and casting conditions. The secondary curing time after mold release was 20 hours at 150 ° C. Using this insulating spacer, SF ₆ decomposition gas resistance was evaluated. In the evaluation, after SF ₆ was sealed in a discharge vessel, continuous discharge was performed for 5 hours using a needle-to-plate electrode, and then the surface resistance was measured according to JIS K6911. It was found that there was almost no decrease in surface resistance and SF ₆ decomposition gas resistance was exhibited.

Claims (11)

A cast molding epoxy resin composition in which a bisphenol type epoxy resin, an acid anhydride curing agent, a curing accelerator, and an inorganic filler are mixed,
The curing accelerator is a curing accelerator (A) having a reaction activity start temperature not higher than the resin mixing temperature, and the reaction activity start temperature is in the range of ± 20 ° C. with respect to the set temperature of the casting mold. The latent curing accelerator (C) and the latent curing accelerator (B) whose reaction activity initiation temperature exceeds the resin mixing temperature and is lower than the reaction activity initiation temperature of the latent curing accelerator (C). The amount of the inorganic filler is 40% by weight or more and 85% by weight or less based on the entire resin composition.   The reaction activity starting temperature of the curing accelerator (A) is 70 ° C. or lower, the reaction activity starting temperature of the latent curing accelerator (B) is 70 ° C. or higher and 110 ° C. or lower, and the latent curing accelerator ( The reaction activity start temperature of C) is 110 ° C. or higher, the reaction activity start temperature difference between the curing accelerator (A) and the latent curing accelerator (B), and the latent curing accelerator (B) and the above The epoxy resin composition for cast molding according to claim 1, wherein a difference in reaction activity start temperature with the latent curing accelerator (C) is 10 ° C. or more.   The curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C) are a tertiary amine, a tertiary amine salt, a boric acid ester, a Lewis acid, an organometallic compound. 3. An epoxy resin for cast molding according to claim 1, wherein the epoxy resin is selected from the group consisting of organic phosphorus compounds, quaternary ammonium salts, quaternary phosphonium salts, amine complexes and imidazole compounds. Composition.   The curing accelerator (A) is a tertiary amine, and the latent curing accelerator (B) and the latent curing accelerator (C) are tertiary amine salts, quaternary ammonium salts, The epoxy resin composition for cast molding according to any one of claims 1 to 3, wherein the epoxy resin composition is selected from the group consisting of a quaternary phosphonium salt, an imidazole compound and a boron halide amine complex.   The total amount of the curing accelerator (A), the latent curing accelerator (B) and the latent curing accelerator (C) is 0.01 parts by weight or more and 3 parts by weight with respect to 100 parts by weight of the bisphenol type epoxy resin. It is 0.0 weight part or less, The epoxy resin composition for cast molding as described in any one of Claims 1-4 characterized by the above-mentioned.   The amount of the latent curing accelerator (C) is larger than the amount of the latent curing accelerator (B), and the casting mold epoxy according to any one of claims 1 to 5, Resin composition.   The said inorganic filler is selected from the group which consists of a silica powder, an alumina powder, a magnesia powder, a glass short fiber, and a glass bead, For the cast molding as described in any one of Claims 1-6 characterized by the above-mentioned. Epoxy resin composition.   When the pot life is defined as the time until the viscosity of the epoxy resin composition for cast molding doubles under heating at 60 ° C., the pot life is 2 hours or more. The epoxy resin composition for cast molding according to any one of claims 1 to 7. The epoxy resin composition for cast molding according to any one of claims 1 to 8, wherein the acid anhydride curing agent, the curing accelerator (A), the latent curing accelerator (B), and the The mixture was prepared by mixing a mixture composed of the latent curing accelerator (C) and a mixture composed of other components, and the epoxy resin composition for cast molding was 1 kg / cm ² or more and 20 kg / cm ² or less. A method for producing a molded product for a high-voltage device, wherein the molding is performed by pouring into a mold with pressure.   The method for producing a molded product for a high voltage device according to claim 9, wherein the pressure is continuously applied until the resin in the mold is completely gelled.   A molded product for high-voltage equipment, which is obtained by the production method according to claim 9 or 10.

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