JP4475240B2 - Epoxy resin composition for obtaining molded article for cutting and molded article for cutting - Google Patents

Description

  The present invention relates to an epoxy resin composition and a molded product thereof, and more particularly to an epoxy resin composition containing phlogopite as a filler and a molded product excellent in cutting workability obtained therefrom.

  Epoxy resin compositions containing inorganic fillers such as silica, talc, mica, clay, and wollastonite are excellent in heat-resistant dimensional stability and electrical insulation. It is widely used as a sealing material for coils or as a molding material for various structural parts (for example, Patent Documents 1 to 4). Among these, mica is particularly excellent in terms of heat-resistant dimensional stability and heat-resistant strength characteristics.

  Conventionally, a molded product obtained from an epoxy resin composition containing the inorganic filler has often been used as it is after being molded. However, in recent years, a structural part having a complicated shape has been demanded. Therefore, after the forming process, a cutting process using a cutting tool such as a blade or a drill is often performed.

  When cutting a molded product obtained from an epoxy resin composition containing a conventional inorganic filler, the cutting tool will wear out if the cutting is repeated with the same cutting tool. There was a need to do. In particular, when the content ratio of the inorganic filler is large and high-precision cutting is required, the replacement frequency of the cutting tool becomes high, the replacement work is complicated, and a consumable cutting tool is not available. There is a problem that the cost of the cutting process is increased due to the increase.

  Of the various inorganic fillers, a molded product obtained from an epoxy resin composition containing talc having a relatively low Mohs hardness is preferable in terms of solving the problems in the cutting process, In terms of strength characteristics, it was insufficient compared to mica.

Therefore, a molded article made of an epoxy resin composition that solves the above-mentioned machinability problem is required in a molded article made of an epoxy resin composition containing mica having excellent heat-resistant dimensional stability and heat-resistant strength characteristics as an inorganic filler. It was done.
JP-A-6-80861 Japanese Patent Laid-Open No. 5-214073 JP-A-6-184407 JP 2000-53843 A

  In view of the above problems, the present invention reduces the wear of a cutting tool and reduces the cutting cost in a molded article made of an epoxy resin composition containing mica excellent in heat-resistant dimensional stability and heat-resistant strength characteristics. It is an object of the present invention to provide a molded article made of an epoxy resin composition that can be used.

The epoxy resin composition of the present invention is an epoxy resin composition for obtaining a molded article for machining, and contains phlogopite as a filler, and the content ratio of the phlogopite is 30 to 80% by mass, The total content of feldspar and pyroxene contained in the phlogopite is 0.5% by mass or less. An epoxy resin composition containing mica as such an inorganic filler, using phlogopite as the mica, and further using phlogopite with a total content of feldspar and pyroxene of 0.5% by mass or less A molded article made of a resin composition has heat-resistant dimensional stability and heat-resistant strength characteristics, and further reduces the wear of the cutting tool during the cutting process and can reduce the cutting cost (hereinafter referred to as this characteristic). Also simply called machinability).

In addition, as the epoxy resin composition, the content of the phlogopite is 30 to 80% by mass, and further, 40 to 70% by mass. It is preferable from the point of being excellent in balance with machinability.

  The molded product for cutting formed by molding the epoxy resin composition is a molded product having excellent heat-resistant dimensional stability and heat-resistant strength characteristics, and also excellent in cutting workability.

  A molded article comprising the epoxy resin composition of the present invention is excellent in heat-resistant dimensional stability and heat-resistant strength characteristics, and excellent in cutting workability.

  The present invention will be specifically described below.

  The epoxy resin composition in the present invention is an epoxy resin composition containing phlogopite as a filler, and the total content of feldspar and pyroxene contained in the phlogopite is 0.5% by mass or less. It is a feature.

  The epoxy resin used in the present invention is not particularly limited as long as it has an average of two or more epoxy groups in one molecule. Specifically, for example, cresol novolac type epoxy resin, bisphenol A Type epoxy resin, bisphenol F type epoxy resin, epoxy resin such as phenol novolac type epoxy resin, and halogen derivatives thereof are used. These may be used alone or in combination of two or more.

  The epoxy resin composition of the present invention usually contains a curing agent and a curing accelerator.

  Examples of the curing agent include phenol novolac resins, acid anhydrides, and imidazole compounds.

  Examples of the curing accelerator include imidazole compounds, tertiary amines, quaternary ammonium salts, phosphines, phosphonium salts, and the like.

  Although the usage-amount of the said hardening | curing agent changes with kinds of hardening | curing agent, specifically, for example, 0.7-1.2 equivalent with respect to 1 equivalent of epoxy groups in an epoxy resin, Furthermore, 0. It is preferable to use it so that it may become about 8-1.0 equivalent.

  Especially as an epoxy resin used in this invention, what used the phenol novolak resin as a hardening | curing agent for the cresol novolak-type epoxy resin is preferable from the point from which the molded object with high heat resistance (Tg) is obtained.

  The phlogopite used in the present invention is characterized in that the total content of feldspar and pyroxene contained in the phlogopite is 0.5 mass% or less.

  Since phlogopite is a natural mineral, in addition to mica having a Mohs hardness of 2 to 2.5, which is the main component, kaolinite having a Mohs hardness of 2.5 and sepiolite having a Mohs hardness of 2 to 2.5 as impurities. Wollastonite with a Mohs hardness of 4.5 to 5 and feldspar and pyroxene with a Mohs hardness of 6 to 6.5 are contained.

  In the present invention, by the method of removing impurities by specific gravity difference such as air classification, the ratio of mica, which is the main component, is increased so that the total content of feldspar and pyroxene with high Mohs hardness is 0.5% by mass or less. Use purified one. Specifically, as a method of reducing the content of feldspar and pyroxene in the phlogopite by the wind classification, phlogopite containing a large amount of pyroxene having high specific gravity on the windward side by scattering the phlogopite in a certain direction by wind force. In addition, phlogopite containing a large amount of feldspar with low specific gravity on the leeward side can be separated and purified.

  When a molded product made of an epoxy resin composition using phlogopite with a high total content of feldspar and pyroxene is cut with a cutting tool such as a blade or a drill, the life is shortened due to wear of the cutting tool. For this reason, the replacement frequency increases, and the epoxy resin may thermally expand due to frictional heat during cutting, which may affect dimensional stability. In the molded article made of the epoxy resin composition used in the present invention, the use of phlogopite with a low total content of feldspar and pyroxene reduces the wear of the cutting tool and generates frictional heat. Can be suppressed.

  The total content of feldspar and pyroxene contained in the phlogopite is 0.5% by mass or less, preferably 0.10% or less, and the lower limit is as close to 0% as possible in the manufacturing process. Is more preferable. When the said content rate exceeds 0.5 mass%, there exists a tendency which cannot fully maintain cutting workability.

  The total content of feldspar and pyroxene in such phlogopite can be measured by the following method.

  That is, a phlogopite sample is weighed (for example, about 2 g) and then put into a 50 mL container. Then, 40 mL of 1,1,2,2-tetrabromoethane is added to the container and stirred, and left to stand for 2 hours or more. At this time, in 1,1,2,2-tetrabromoethane, the components contained in the phlogopite settle according to the specific gravity, but the specific gravity of the layer in which mica and feldspar exist (2.55-2. 85), the pyroxene precipitates at the bottom of the container because the specific gravity of the pyroxene (3.2 to 3.9) is higher.

  The pyroxene precipitated at this time is taken out and washed with acetone, and the mass of pyroxene is measured.

  Next, 2.3 mL of toluene is further added to the remaining liquid from which the pyroxene is removed, and the mixture is stirred and allowed to stand for 2 hours or more. At this time, the specific gravity of the mixed solution composed of 1,1,2,2-tetrabromoethane and toluene is about 2.75 to 2.80. At this time, the specific gravity of feldspar (2.55 to 2.76) is lower than the specific gravity of mica (2.85) in the mixed solution composed of 1,1,2,2-tetrabromoethane and toluene. Therefore, the layer containing feldspar exists in the surface layer of the mixed solution.

  Then, the layer containing feldspar is collected, washed with acetone, dried, and the mass of feldspar is measured.

  In this way, the masses of feldspar and pyroxene were measured, and the mass of feldspar and pyroxene contained in the phlogopite by the formula of (massite of pyroxene + mass of feldspar) / (mass of phlogopite) × 100 (%). The content can be calculated.

  The content ratio of the phlogopite contained in the epoxy resin composition of the present invention is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. If the content is too high, the machinability tends to be poor, and if it is too low, the heat-resistant dimensional stability tends to decrease.

  In the epoxy resin composition of the present invention, in addition to the above-mentioned components, as long as the effects of the present invention are not impaired, other inorganic fillers and organic fillers, release agents, colorants, You may contain a flow regulator, a ultraviolet absorber, antioxidant, etc.

  The epoxy resin composition of the present invention can be obtained by premixing the above various raw materials with a blender such as a Henschel mixer, kneading with a melt kneader such as a hot roll or an extruder, and cooling and grinding. Can do.

  The obtained epoxy resin composition can be molded and cured by using a known molding method such as compression molding or transfer molding.

  And the molded product obtained by the molding is a molded product that is excellent in heat-resistant dimensional stability and heat-resistant strength characteristics and also excellent in machinability, for example, production of various epoxy resin molded products to be machined, More specifically, it is preferably used for applications such as slip ring insulation materials for in-vehicle alternators (generators).

  The present invention will be described more specifically with reference to examples. The present invention is not limited to the examples.

  First, a method for calculating the content of feldspar and pyroxene contained in phlogopite will be described.

  About 2 g of a preliminarily weighed phlogopite sample is put in a 50 mL container, and further 40 mL of 1,1,2,2-tetrabromoethane is added and stirred, and the phlogopite sample is then added to the 1,2,2, After dispersing in 2-tetrabromoethane, the mixture was allowed to stand for 2 hours or more. At this time, in 1,1,2,2-tetrabromoethane, components contained in phlogopite settle according to the specific gravity, but compared with the specific gravity of mica and feldspar (2.55 to 2.85). Since pyroxene had a high specific gravity (3.2 to 3.9), pyroxene precipitated at the bottom of the container.

  Then, leave only the precipitated pyroxene in the container, transfer 1,1,2,2-tetrabromoethane and other components to another container, wash the pyroxene precipitated in the container with acetone and dry it. The mass of pyroxene was measured after removal.

  Next, 2.3 mL of toluene was added to 1,1,2,2-tetrabromoethane and other components transferred to another container, stirred and dispersed, and allowed to stand for 2 hours or more. At this time, in toluene / 1,1,2,2-tetrabromoethane, components contained in phlogopite settle according to the specific gravity, but compared to the specific gravity of mica (2.85), Since the specific gravity (2.55 to 2.76) was low, the feldspar floated in the upper layer.

  And the upper feldspar was collected, washed with acetone, dried and taken out, and the weight of feldspar was measured.

  Then, the ratio of the sum of the pyroxene mass and the feldspar mass to the mass of the original phlogopite sample is given by (massite pyroxene mass + feldspar mass) / (mass phlogopite sample) × 100 (%) Asked.

Example 1
O-cresol novolac type epoxy resin (Dai Nippon Ink Co., Ltd. N695, softening point 94-98 ° C., epoxy equivalent 210-230 g / eq) 19 parts (mass part, the same applies hereinafter), novolac type phenol resin (Matsushita Electric Works, Ltd.) 9 parts by softening point 90-110 ° C., weight average molecular weight about 3000), phlogopite prepared by air classification to 0.5% by mass (Suzolite Mica 60S manufactured by Kuraray Trading Co., Ltd.) 69 parts, calcium stearate (manufactured by Tamnan Chemical Co., Ltd., melting point 149-155 ° C., passing through 300 mesh 96%), 2 parts, imidazole (manufactured by Shikoku Kasei Co., Ltd., Sumicure C11-Z, melting point 69) ~ 74 ° C, purity 96% or more, moisture content 0.5% or less) 1 part premixed for 1 minute with a blender, then resin temperature 100 ~ Were kneaded by the biaxial kneader at a kneading time of 3 minutes at 10 ° C., cooled milled, granulated, to obtain an epoxy resin composition.

  Next, the obtained epoxy resin composition was subjected to compression molding under the conditions of a mold temperature of 170 ° C., a mold pressure of 30 MPa, and a curing time of 90 seconds to obtain tensile test pieces, bending test pieces, and specific gravity measurement test pieces according to JIS6911. Molded.

  Using the obtained various test pieces, a drill wear test, a linear expansion coefficient, and a molded product strength were measured by the following evaluation methods.

(Drill wear test)
Using a pneumatic drill with a tensile test piece fixed to a vise and a new drill blade (φ2.5mm, SKD) attached to a 6.5mm thick chuck holding part of the tensile test piece, drilling is performed at 0.2MPa. went.
The drilling process was repeated with the same drill blade, the time required for the hole to penetrate was measured, and the number of drillings reached when the required time exceeded 5 seconds was evaluated.

(Heat-resistant dimensional stability)
Using a test piece for measuring specific gravity, the temperature was raised with a horizontal thermal dilatometer (Delight Meter DLY9400 manufactured by ULVAC-RIKO, Inc.), and the slope was calculated from 80 to 120 ° C.

(Bending strength)
The bending strength was measured according to JIS6911.
Moreover, the moldability of the obtained epoxy resin composition was evaluated by an extrusion flowability test according to JIS K 6911 under the conditions of a sample amount of 45 g, a resin temperature of 160 ° C., and a cylinder pressure of 18.4 MPa.
Further, in order to visually observe the amount of impurities contained in the phlogopite, after forming a flat test piece having a thickness of 0.2 mm by compression molding, a visible light is transmitted, and the flat test piece has a diameter of 35 mm. The number of foreign substances considered to be feldspar and pyroxene present in the range was visually counted.

  The results are shown in Table 1.

(Examples 2-6 and Comparative Examples 1-3)
An epoxy resin composition and a molded product were obtained and evaluated in the same manner as in Example 1 except that the epoxy resin composition having the composition shown in Table 1 was used. The results are shown in Table 1.

  From the results of Table 1, in the evaluation of the drill wear test of the molded products obtained from the epoxy resin compositions of Examples 1 to 6 in which the total content of feldspar and pyroxene in phlogopite is 0.50% by mass or less, In both cases, the drilling time reached when the time required for the hole to penetrate exceeds 5 seconds is 42 times or more, and the wear of the drill is suppressed, but the total content of feldspar and pyroxene in the phlogopite In the evaluation of the molded products obtained from the epoxy resin compositions of Comparative Examples 1 to 3 having a rate exceeding 0.50% by mass, it is found that the number of times is 28 times or less, and the wear of the drill is likely to proceed.

Claims (3)

An epoxy resin composition for obtaining a molded article for machining ,
Contains phlogopite as a filler,
The content ratio of the phlogopite is 30 to 80% by mass,
An epoxy resin composition, wherein the total content of feldspar and pyroxene contained in the phlogopite is 0.5 mass% or less.   The epoxy resin composition according to claim 1, wherein a content ratio of the phlogopite is 40 to 70% by mass. The molded article for cutting formed by shape | molding the epoxy resin composition of any one of Claim 1 or Claim 2.