JPS61109205A - Electrically insulating cement material and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an asbestos material having machinability as an electrical property that can replace Type 1 asbestos cement F board (commonly known as Heminod) for electrical insulation specified in JIS C2210. The present invention relates to a cementitious electrical insulating material free of additives and a method for producing the same.

Conventional technology JISC22! Hemit, an asbestos-cement board for electrical insulation specified in 1), is made by molding asbestos using Portland cement/F as a binding material, and is used in various electrical equipment as an insulating material that can be machined and has good heat resistance. has been done. However, this heminode contains about tO of asbestos.
Since it contains asbestos of 1,000% asbestos, it generates asbestos dust during machining, which is harmful to health. Therefore, it is desirable to develop a technology to manufacture an insulating material that can replace Hemi-7 without using Asbestos. ing.

The solution that Bunmei is trying to solve is to manufacture cementitious insulation materials without using asbestos.
! As with the case of replacing IL fibers, it is not so easy.

In other words, in the case of electrical insulating materials, although there are alternative fibers that can ensure strength and heat resistance, using only those fibers will inevitably lead to deterioration in at least one of the electrical properties and machinability. For example, if pulp is used instead of asbestos, the arc resistance deteriorates as the amount of pulp increases, so from the viewpoint of electrical properties it is necessary to keep the pulp at 4 to 6 wt. 1%. Products with this proportion are rigid and difficult to machine, making them unsuitable for use as insulating materials.

The purpose of the present invention is to solve the above-mentioned problems in producing cementitious electrical insulating materials without using asbestos, and to produce cementitious electrical insulating materials that do not contain asbestos but have a quality equivalent to Hemit. The purpose is to provide a manufacturing method.

Means for Solving the Problems As a result of intensive research, the above object has been achieved in the present invention as detailed below.

First of all, the first aspect of the present invention is a product containing 10 to 40% by weight of talc powder and having a density of 1.6 to 2.0 g/c+s'' that does not contain asbestos.
The present invention provides an electrically insulating material made of a cementitious molded body. The second aspect of the present invention, which provides an advantageous manufacturing method for the above-mentioned insulating material, is an insulating material that is made of cement or an inorganic binder mainly composed of cement, reinforcing fibers that do not contain asbestos, and a mineral-free filler. Water is added to the molding material, which is talcum powder, which accounts for at least a part of the ``trade agent'' or ~40% by weight of the entire molding material, and the final density is 1.6~2.08. It is characterized in that it is dehydrated and molded in such a manner that a molded product of Cl is obtained, and then cured in an autoclave.

A major feature of the insulating material according to the present invention is that it contains talc powder as described above, but the reason why the above problem can be solved by this method is unclear. First, talc powder combined with a cementitious matrix by autoclave curing is
It acts as a solid lubricant between the cutting surface and the tool even after turning into chips, preventing the propagation of cracks that occur during cutting and keeping them in the cutting area, improving free-cutting properties. Realize. In addition, the affinity between the cementitious matrix and the talc powder is large, making it easy to achieve the required strength. Therefore, the amount of reinforcing organic fibers such as pulp that deteriorate electrical properties can be reduced. The orientation increases the diffusion resistance of hygroscopic moisture and suppresses a decrease in insulation resistance in a humid atmosphere.

The production of the cementitious electrically insulating material according to the production method of the present invention can be carried out in general in accordance with the conventional method for producing asbestos cement boards for electrical insulation, except for using the raw materials as described above. As the cement, in addition to ordinary Portland cement, early strength Portland cement, blast furnace cement, 7-ly 7-tsutsu cement, alumina cement, etc. can be used. In addition, 1 () to ordinary Portland cement
70% by weight of silicic raw materials, such as silica, amorphous silicic acid (such as silica flour, floidal silicate, diatomaceous earth, etc.), is mixed in so that it reacts with the lime liberated from the cement. It's okay. This not only increases the strength of the product, but also improves its electrical insulation. As reinforcing fibers, pulps of softwood, hardwood, hemp, etc., especially bleached kraft pulp of softwood, are suitable, but in addition to these, small amounts of glass fiber, rayon, aramid fiber, acrylonitrile fiber, vinylon fiber, etc. can be used in combination. Good too. However, excessive use of pulp and organic fibers must be avoided since this causes a decrease in arc resistance as described above. A preferred blending ratio is 2 to 5% by weight based on the total molding material. An appropriate filler is selected in consideration of its influence on the electrical properties of the product, and in addition to talcum powder, wollastonite, mica, chloride, serpentine powder, etc. can be used.

Talc powder, an essential ingredient, accounts for 10-4% of the weight of the total molding material.
0% by weight is used, and when it is less than 10% by weight, the required machinability is not achieved, and when it is more than 4° ()% by weight, the mechanical strength is insufficient. In the case of all filfi fillers, the total amount of fillers is about 10 to 50% by weight of the total molding material.

There is no limit to the method of molding the above-mentioned ffl-forming molding material, but when molding by press molding method, approximately 0.8 to 3.0 @
A certain amount of water is added and kneaded, and preferably a polymer flocculant is added thereto to flocculate the powder raw material, which is then dehydrated and press-molded. In this case, the final density of the molding press is 1.
It is usually selected in the range of 100 to 200 KH7cm'' so as to obtain a molded product of 6 to 2, Qg, 'c+a'. If the product density does not reach the above range, the strength, dielectric breakdown strength and resistance to corrosion will be insufficient. On the other hand, if it is a high-density product with a broom rating exceeding 2.0, it becomes difficult to use it mechanically.

The dehydrated molded product is transferred to an autoclave after 1iii) 1 age at room temperature according to the conventional method of autoclave curing, and then aged under a water vapor pressure of at least 61.5 KB7cII', preferably about 4 to 9 KFi)' cm: Open at 14:00 and heat for preferably 7 to 0 hours. If the autoclave curing layer 1' is too mild, it will give a product with insufficient strength and electrical properties, but if it is too harsh, it will deteriorate the machinability.

Effects of the Invention According to the present invention, there is provided a cementitious electrical insulating material that does not contain asbestos but has electrical properties, machinability, and heat resistance equivalent to or better than conventional asbestos cement boards for electrical insulation. Therefore, this completely solves the problem of health hazards caused by asbestos dust in manufacturing and machining processes.

The particularly excellent performance of the cementitious electrical insulating material according to the present invention is that it does not easily deteriorate its insulation properties due to moisture absorption, and this feature makes it possible to manufacture electrical equipment with highly reliable insulation properties. .

unconstitutional The present invention will be described below with reference to Examples and Comparative Examples.

The method of characteristic testing in each example is as follows.

Arc resistance 1 Volume resistivity Rv + Surface resistivity RsJIS
According to K 6911. However, the measurement conditions for Rv and Rs are 2.
The temperature was 5°C, 190%RH, and 90 hours.

Hole listening & testing diameter Loa - 1 rotation speed 26Orpm, feed speed 4f)w
Using a +a/+nin drill, the graphite plate is swung downwards, and the hole 1λI is drilled to measure the size of the chipping of the sample caused by the penetration of the drill.

Cutting test diamond segment saw (Mitsubishi/-t:/[AlR
85, outer diameter 356+nm, tooth thickness 2.6mm), rotation speed 130rl1m, feed rate 20 (11) mm/
Dry cut at min. and measure the size of the chip on the sample cut.

Comprehensive T Rating The above hole drilling test and cutting test are good if the size of chipping is 0.5 square or less in both cases, poor if 1.5 inch is drilled from either side, and poor in other cases. I rate it as somewhat good.

Examples 1-3. Comparative Examples 1 to 7 After kneading the molding material with twice the amount of water, the surface pressure was 160 Kg.
1'cta' (However, only Comparative Example 1 is 1 f) OKH/
'cw') into a plate shape with a thickness of 312.5mm,
Next, autoclave 11 years old (9Kg7cm'x 7
Hr).

Table 11 shows the material formulations and product characteristics in 12 examples of 'jt-rolling with various changes in the material formulations in the above manufacturing method.

In addition, for the products of Example 2 and Comparative Example 1,
Changes in volume resistivity Rv and surface resistance (+r<S) over time of +t7 were investigated when placed in a furnace temperature and humidity chamber at 0% RH.The results are shown in Figures 1 and 2.

-3]

[Brief explanation of the drawing]

11'! + Figure and Figure 2 show the changes over time in volume resistivity Rv and surface resistivity Rs for the products of Example 2 and Comparative Example 1 when placed in a constant temperature and humidity chamber at 25°C and 90% RH. There is a graph t' showing the results of examining .

Claims (4)

[Claims] (1) An electrically insulating material consisting of a cementitious molded body containing 10 to 40% by weight of talc powder, free of asbestos, and having a density of 1.6 to 2.0 g/cm^3. (2) Talc consisting of cement or an inorganic binder mainly composed of cement, reinforcing fibers that do not contain asbestos, and an inorganic filler, in which at least a portion of the inorganic filler accounts for 10 to 40% by weight of the total molding material. Water is added to the powdered molding material and kneaded to give a final density of 1.6 to 2.
A method for producing a cementitious electrical insulating material, which comprises dehydrating and molding under conditions such that a molded product with a density of 0 g/cm^3 is obtained, and then curing in an autoclave. (3) The manufacturing method according to claim 2, wherein the inorganic binder whose main component is cement is a mixture of cement and silica or amorphous silicic acid. (4) The manufacturing method according to claim 2, in which 2 to 5% by weight of pulp is used as the reinforcing fiber based on the total molding material.