JPH0274548A - Production of heat insulation-resistant sheet - Google Patents

Abstract

PURPOSE:To improve heat insulation resistance at relatively low temperature by blending specific powder with aluminum orthophosphate ethanol complex (APHE) as a binder and heat-treating. CONSTITUTION:Scaly or fibrous powder (A) having >=10 aspect ratio is obtained by selecting from mica such as fluophlogopite [KMg3(A>=Si3)O12.F2], silica fibers having 5mum average diameter, etc. Then APHE [AlPO4 HCl(C2H0OH)4] (B) as a binder is dissolved in an organic solvent such as ethanol to give a binder solution (C). Then a collected mica sheet prepared by making the component A into paper is impregnated with the solution C by dipping method to give an impregnated sheet (D). Then the component D is dried and heated to 50-200 deg.C and treated in such a way that the component A becomes 55-99wt.% total sheet weight to produce a heat insulation-resistant sheet having 20-500mum thickness of film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-resistant insulating sheet used for insulating materials for electrical and electronic equipment, flexible printed circuit boards, flame-retardant paper, wall covering materials, and the like.

BACKGROUND OF THE INVENTION Conventional heat-resistant insulating sheets mainly use natural mica or synthetic mica as a filler, and as an organic binder for forming the sheet, Japanese Patent Laid-Open No. 48-7
073, JP-A-52-36141, JP-A-57-82
Various types have been used, such as those disclosed in No. 598. In addition, as an inorganic binder, for example,
Colloidal silica, colloidal alumina, shown in JP-A-48-7009 [iJ], and phosphate glass having BaO.P2O as a basic component are disclosed.

In addition, as a method for manufacturing Maiga sheets using aluminum phosphate, there are
080, JP-A-54-11Ei007, JP-A-55-
23042, JP-A-57-11259g, etc. Mainly, methods such as those found in JP-A-54-116007J, etc., involve mixing alumina sol and phosphoric acid, impregnating the mixture, and reacting at high temperatures to form aluminum phosphate.
[As seen in JP-A-55-23042J, etc., a method using aluminum phosphate such as aluminum monophosphate is known.

Problems to be Solved by the Invention All of the conventionally disclosed methods using aluminum phosphate as a binder require a heating temperature of 300°C in order to harden the binder and form a sheet with a predetermined strength.
It requires a higher temperature. Therefore, there were problems such as the need for dedicated heating equipment and the time required for the process.

Means for Solving the Problems The present inventor focused on the property of aluminum orthophosphate ethanol complex represented by the chemical formula of AgPO-HCl(C2H50H)4 to vitrify at low temperature, and arrived at the invention of using it as a binder. It was. That is, the present invention provides a method for producing a heat-resistant insulating sheet comprising a scale-like or fibrous powder and a binder, in which a scale-like or fibrous powder having an aspect ratio of 10 or more and an aluminum orthophosphate ethanol complex (hereinafter referred to as API) as a binder are used. Abbreviated as E > Ai) PO
The present invention provides a method for producing a heat-resistant insulating sheet characterized by using 4HCΩ (CH0H)4, and a method for producing a heat-resistant insulating sheet in which the above-mentioned scale-like powder is natural mica or synthetic mica powder.

In the case of scaly powder, the aspect ratio refers to the value obtained by dividing the diameter of the powder by its thickness, and in the case of fibrous powder, it refers to the value obtained by dividing the length in the long direction of the powder by the width or diameter in the short axis direction. . The aspect ratio of the scaly powder or fibrous powder such as mica used in the present invention is 10 or more. The role of these fillers is that in the case of scaly powder, the wide surfaces of the scales are closely linked together, and in the case of fibrous powder, the powders intertwine with each other to create a skeletal structure and reinforce the sheet. It is thought that it will be effective. To this end, the scaly or fibrous powder used as the filler in the present invention must have an aspect ratio of 10 or more to function, and as a result, the sheet will not have high mechanical properties. Although it may be desirable to increase the aspect ratio, it is difficult to produce fillers with an aspect ratio of 300 or more.

The types of mica that can be used include phlogopite (KMg
Natural mica such as (Ail S i ) O・(OH) 2), muscovite, and biotite may be used, or fluorine phlogopite (K
Synthetic mica represented by Mg3 (AgS13)012F2) may also be used. However, in order to take advantage of the heat resistance of the binder of the present invention at 1000° C. or higher, fluorine phlogopite is preferable.

In addition to mica, scaly powders that can be used in the present invention include hexagonal boron nitride, graphite, molybdenum disulfide, etc., and fibrous powders include A/I/Mina fibers, silica fibers, and carbonized silicon whiskers, etc. The particle size of these fillers that can be used in the present invention is preferably one having an average diameter of 5 tIn or more.

The conventional binder, aluminum phosphate compound, is
Even if you try to melt it, it will decompose before it melts, making it impossible to create glassy aluminum phosphate.

The APHE used as a binder in the present invention is made into a glassy state starting from a low temperature, and when aluminum trichloride (Al2CN5) and phosphoric acid (H3PO4) are reacted in ethanol at a temperature below 0°C, AD P04 H is produced. A crystalline precipitate with a chemical composition of (1!-(C2H50H)4) is obtained.

This precipitate has a strange structure in which cubes made of aluminum, oxygen, and phosphorus atoms are connected via alcohol molecules. It begins to harden at temperatures above 50°C, and when heated slowly to approximately 100°C, the alcohol disappears and crosslinks between cubes are formed, resulting in a glass-like aluminum phosphate with a three-dimensional lattice of aluminum, oxygen, and phosphorus. Can be done.

The glassy aluminum phosphate obtained in this way is 16
It begins to decompose at around 00°C, but can withstand temperatures below that temperature.

Glassy aluminum phosphate is inert and insoluble in liquids, but the original ethanol-containing precipitate is soluble in both water and organic solvents at room temperature. The solution concentration is not particularly specified, but it is desirable to be as high as possible within the range of dissolution.
It is usually used in a concentration range of 10 to 50 wt%.

A solution is prepared by dissolving APHE used as a binder in an organic solvent such as ethanol, methanol, butanol, isopropyl alcohol, acetone, or methyl ethyl ketone.

Next, a sheet is made using mica or the like as a filler, but in order to make it, the raw material mica powder is made into paper, and a sheet made of mica alone is made in advance.

In that case, the papermaking method is a normal method, for example,
This is done using a fourdrinier type, circular wire type, etc. paper machine. The sheet thus obtained, the assembled mica base, is impregnated with the solution. The impregnation method may be a dip method, a spray coating method, a roll coating method, a brush coating method, or the like. Then, the sheet impregnated with the binder solution is
By drying and heat-treating, the organic solvent contained in the APHE solution is scattered, and the ethanol molecules constituting APHE are desorbed and condensed, turning into aluminum phosphate glass that serves as a binder.

The dry heat treatment temperature is 50 to 200°C, preferably 100°C.
~150°C is suitable. Below 50"C, the drying speed is slow and inefficient, and if it exceeds 200"C, curing has already been completed, so it is meaningless.In this way, a mica-based heat-resistant insulating sheet containing aluminum phosphate as a binder is produced. It will be done.

In addition to the above-mentioned method of impregnating the sheet after papermaking, scaly or fibrous powder as a filler is added to APH.
After the slurry dispersed in the organic solvent solution of E is spread on a release film by a doctor blade method, a roll coater method, a calendar method, etc., the solvent is distilled and a dry heat treatment is performed under the same conditions as above. A sheet is obtained by peeling it off from the release film.

At this time, the slurry may be dispersed using a general dispersing machine such as a ball mill, a vibration mill, a medium stirring mill, or a planetary mill.

The preferable thickness of the sheet formed by the above-mentioned various methods and heat-treated is 20 to 500 mm.

When sheeting is done by papermaking method, the aspect ratio of the filler is 50.
The above is preferable, and the doctor blade method, roll coater
In the case of a coater method such as a method, it is preferably 20 or more.

In addition, the appropriate mixing ratio of the filler is in the range of 55 to 99 when the weight of the entire heat-resistant insulating sheet is 100. If the mixing ratio is less than 55, the skeletal structure of the sheet will not be sufficient and the mechanical properties If the mixing ratio exceeds 99%, it will not have any effect as a binder, and the strength of the heat-resistant insulating sheet will be lost.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Commercially available synthetic mica powder (manufactured by Otake Ceram, average particle size 2
50μ, aspect ratio 110) 6g in 1g of water
After stirring and dispersing for a minute, a 159φ9 wet sheet was made using a standard sheet machine (manufactured by Kumagai Riki Kogyo). The obtained wet sheet was heated to 105℃ in a hot air dryer.
After drying for 2 hours, a laminated mica sheet with a thickness of 75 m was obtained. This assembled mica sheet was coated with 30vt9 of aluminum orthophosphate ethanol complex (APHE).
6. After immersing in the ethanol solution for 15 seconds and pulling it out,
Drying and heat treatment were performed at 120° C. for 10 hours in a hot air dryer.

The thus obtained insulating sheet had a thickness of 86 μs and a smooth surface. In addition, a test piece with a width of I5U and a length of 60mm was cut from this sheet, and its tensile strength was measured using a tensilon measuring machine, and it was as strong as 1.5kg/mj.
It was also flexible. In addition, the insulation resistance value is 2, OXLO13
The value was as high as Ω·(1). Further, when this sheet was subjected to thermal analysis using a differential thermal balance, it was confirmed that there was no change in weight or differential heat up to at least 980° C., and that the sheet was stable.

Examples 2 to 6 Table 1 shows the characteristic values of various sheets prepared according to Example 1 by changing the type of mica used as a reinforcing filler and the type of APHE solution.

(Leaving space below) Example 7 After dissolving 300 g of APHE in 570 cc of ethanol, 225 g of hexagonal boron nitride powder with an average particle size of 9- and an aspect ratio of 20 was added, pre-prepared for 30 minutes in a laboratory stirrer, and further It was placed in an alumina pot mill with an internal volume of 6 g, and 2.4 g of alumina balls with a diameter of 20 mmφ were added thereto. The mixture was mixed for 24 hours.

The slurry thus obtained was formed into a sheet using a doctor blade type sheet forming machine by setting a wet sheet thickness of 125 μs, and subjected to dry heat treatment at 105° C. for 3 hours to obtain a sheet with a film thickness of 48 tm. In addition, when the tensile strength was measured in the same manner as in Example 1, it was as strong as IJkg/-.
It is flexible, and the insulation resistance value is 5, I Xl013Ω・
It was a high value.

Effects of the Invention The present invention makes it possible to produce an insulating sheet with excellent heat resistance using aluminum phosphate as a binder made from an aluminum orthophosphate ethanol complex without the need for high-temperature treatment of 300°C or higher, which was required for conventional products. , 200
Heat treatment at low temperatures below ℃ has made it possible to manufacture heat-resistant insulating sheets using mica as a practical reinforcing filler.

Claims (2)

[Claims] (1) In a method for producing a heat-resistant insulating sheet consisting of a scale-like or fibrous powder and a binder, an aluminum orthophosphate ethanol complex AlPO_4.HCl (C
_2H_5OH)_4 A method for producing a heat-resistant insulating sheet. (2) The method for producing a heat-resistant insulating sheet according to item 1, wherein the scaly powder is natural mica or synthetic mica powder.