JPH0987992A - Mica sheet manufacturing method - Google Patents

Abstract

(57) Abstract: A method for producing a uniform mica sheet having excellent electric insulation, heat resistance and mechanical strength is provided. SOLUTION: Synthetic fluoromica and micro glass fiber are aggregated by using an aggregating agent, and then the solid content concentration of the aggregate is diluted to 0.01 to 2%, and papermaking is carried out by a wet papermaking method. And a method for producing a mica sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a uniform mica sheet having excellent electric insulation, heat resistance and mechanical strength.

[0002]

2. Description of the Related Art Conventionally, as an inorganic sheet made of layered silicate, a mixed paper made of synthetic montmorillonite sol described in JP-B-52-18399, JP-B-54-15.
Inorganic sheet obtained by adding inorganic fiber to montmorillonite sol described in JP-A-043, sheet comprising sodium tetrasilicon mica described in JP-A-35-6874, JP-A-55-
A sheet made of mica and glass described in Japanese Patent No. 142539 and a sheet made of vermiculite described in Japanese Patent Application Laid-Open No. 53-3918 are disclosed.

However, since these sheets are manufactured by coating or flow spreading the sol, it is difficult to achieve both the fluidity and the coating property of the sol, and the obtained sheet is uneven.
There were problems that the layer could not be thinned, bubbles were mixed in, and the strength was weak.

On the other hand, the inventors of the present invention previously disclosed in Japanese Patent Laid-Open No. 7-73.
No. 766 filed a patent application for a method for producing a mica sheet. The method for producing a mica sheet in the same item is a method in which only synthetic fluoromica is dispersed in water, a coagulant is added to dilute it to a predetermined concentration, and then wet papermaking is performed. However, even the mica sheet produced by using the method of the same item is not satisfactory in terms of strength, brittleness and the like.

On the other hand, in the case of producing a sheet using natural mica as a raw material, it is known that natural mica is dispersed in water and produced by a wet papermaking method. However, natural mica is a synthetic fluoromica used in the present invention. Compared to
Since the self-bonding force of the natural mica itself is weak, the strength of the obtained sheet is extremely reduced. Furthermore, when an adhesive is added to make a sheet to supplement the strength, the strength is improved to some extent, but the electrical insulation, heat resistance, etc. are significantly reduced, and the strength, electrical insulation, and heat resistance are reduced. It was very difficult to obtain a sheet that satisfies both the requirements for sex.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a uniform mica sheet which is excellent in electric insulation, heat resistance and mechanical strength.

[0007]

Means for Solving the Invention As a result of intensive studies for solving the above-mentioned problems, the present inventors have disperse synthetic fluoromica and micro glass fiber in water, and add a coagulant to the dispersion. Addition to form an aggregate of the synthetic fluoromica and the micro glass fiber, then diluting the solid content concentration of the aggregate from 0.01% to 2%, and using a diluted liquid to make a paper by a wet papermaking method. Or by dispersing the synthetic fluoromica in water, adding an aggregating agent to the dispersion to form an aggregate of the synthetic fluoromica, and then mixing the microglass fiber into the aggregate, Further, by diluting the solid content concentration to 0.01 to 2% and making a paper by a wet papermaking method using the diluted liquid, it is possible to produce a uniform mica sheet excellent in electric insulation, heat resistance and mechanical strength. Find out, Invention has been reached.

The present invention will be described in detail below.

In the mica sheet of the present invention, the synthetic fluoromica and the micro glass fiber are dispersed in water as described above, and an aggregating agent is added to the dispersion to form an aggregate of the synthetic fluoromica. , The solid content concentration of the aggregate is 0.01
It is manufactured by a wet papermaking method using a liquid diluted from 2% to 2%.

Alternatively, synthetic fluoromica is dispersed in water, and an aggregating agent is added to the dispersion to form an aggregate of the synthetic fluoromica, and then microglass fiber is mixed with the aggregate, and It is produced by diluting the solid content concentration to 0.01 to 2% and making a paper by a wet paper making method using the diluted liquid.

As the synthetic fluoromica used in the present invention, any synthetic fluoromica produced by either the melting method or the solid phase reaction method can be used.
Synthetic swelling fluoromica obtained by heat treatment of talc and alkali silicofluoride or a mixture of alkali fluorides described in Japanese Patent No. 49415 is preferable in terms of purity and mechanical strength.

Further, in order to impart various functions such as coloring, non-swelling property, antibacterial property and hygroscopicity to the synthetic swelling fluoromica, the interlayer ion of the synthetic swelling fluoromica is an inorganic cation. An exchanged synthetic fluorine mica ion exchange product may be used. As a method of ion-exchange the synthetic swelling fluoromica with an inorganic cation, after dispersing the synthetic swelling fluoromica in water, in addition to a method of mixing and stirring a solution containing a predetermined inorganic cation, First, there is a method in which a sheet is made of synthetic swelling fluoromica by the method described in the present invention, and then the sheet is immersed in water or an organic solvent containing an inorganic cation.

The average particle size of the synthetic fluoromica used in the present invention is not particularly limited, but is preferably 0.5 to 50 μm, more preferably 1 to 10 μm. If the average particle size is less than 0.5 μm, not only will the particles of the wire pass through the eyes of the wire even if they are agglomerated with a coagulant during wet papermaking, but the water will also get clogged with the wires of the paper machine. Does not become a sheet without pulling. On the other hand, if it exceeds 50 μm, the binding force between particles in the case of being a sheet is not sufficient and, as a result, not only a sheet having low mechanical strength but also the size of flocs after aggregation is large. It becomes too uneven and the sheet becomes uneven.

The micro glass fiber used in the present invention is an ultrafine glass fiber produced by a steam spraying method, a spinning method, a flame insertion method, a rotary method or the like, and its average fiber diameter is generally 5 μm or less. Pointing to something.
The average fiber diameter of the micro glass fibers is not particularly limited, but fibers having a smaller average fiber diameter can produce a more uniform sheet.

The weight ratio of the synthetic fluoromica to the micro glass fiber in the present invention is preferably 20/80 to 80/20. When the amount of the synthetic fluoromica is less than 20 parts by weight, the binding force in the sheet by the synthetic fluoromica becomes small and the strength becomes very weak. Further, if it exceeds 80 parts by weight, it becomes very brittle, and especially the bending strength is significantly reduced.

Examples of the cationic coagulant used in the present invention include organic coagulants such as polyethyleneamine, cationic polyacrylamide, polythiourea acetate and polyvinylpyridine hydrochloric acid, and inorganic coagulants such as aluminum sulfate. Examples thereof include ferric sulfate, ferric chloride, calcium chloride and basic aluminum chloride.

Although any of these organic coagulants and inorganic coagulants may be used, among the inorganic coagulants, an inorganic polyvalent cationic coagulant containing an aluminum atom is more preferable. , Aluminum sulfate (sulfate band), aluminum chloride, basic aluminum chloride, polyaluminum hydroxide, etc. are commercially available.

Examples of the anionic flocculant used in the present invention include organic flocculants such as sodium alginate, carboxymethyl cellulose, sodium polyacrylate,
Anionic polyacrylamide etc. are mentioned.

The inverse polymer emulsion type flocculant used in the present invention is a so-called water-in-oil type polymer dispersion obtained by emulsion-polymerizing a hydrophilic monomer in a hydrophobic organic dispersion medium. Examples of the monomer include acrylamide, an acrylic acid salt, a vinyl monomer having a sulfonate group, an acrylic acid quaternary ammonium group ester, and a diallyldimethylammonium salt, and various monomers may be used alone or according to anionic or cationic use. It is used after being copolymerized. An example of this reverse-phase polymer emulsion type flocculant is AC from Mitsui Cyanamid Co., Ltd.
It is sold under the trade name of CURAC.

As the aggregating agent used in the present invention, either a cationic aggregating agent or an anionic aggregating agent may be used. The cationic aggregating agents may be used alone or in combination of two or more, or a cationic aggregating agent may be used. It is more preferable to use both and an anionic flocculant together.

Among the cationic flocculants, an inorganic polyvalent cationic flocculant containing an aluminum atom is more preferable because it can easily form a strong aggregate.

When the cationic coagulant and the anionic coagulant are used in combination, it is preferable to first coagulate with the cationic coagulant and then strongly coagulate with the anionic coagulant. 1 for each cationic and anionic flocculant
One kind may be used, but two or more kinds may be used in combination.
When a cationic flocculant and an anionic flocculant are used in combination, an organic flocculant is preferable. Among the organic flocculants, the reverse phase polymer emulsion type flocculant has a relatively large floc and has a large floc. It is more preferable because it can be easily controlled.

The amount of the aggregating agent used in the present invention varies depending on the concentration of the synthetic fluoromica dispersion and the type of the aggregating agent to be added, but is generally 0.0 with respect to the synthetic fluoromica.
1-5% is preferred. Here, if it is less than 0.01%, the aggregation of the synthetic fluoromica is not sufficient, and if it is more than 5%, it may be redispersed after the aggregation.

In the present invention, the concentration of the water-dispersed slurry of synthetic fluoromica and microglass fiber during wet papermaking is preferably 0.01 to 2%. Here, if the slurry concentration is less than 0.01%, the water is not sufficiently drained during papermaking, and as a result, no sheet is formed, or only a sheet having a very low basis weight is formed. On the other hand, when it is higher than 2%, the fluidity of the slurry is deteriorated, and only a very nonuniform sheet is formed.

As a method of adjusting the slurry concentration of the synthetic fluoromica and the micro glass fiber, the synthetic fluoromica or the synthetic fluoromica and the microglass fiber are aggregated in an adjusting tank and then adjusted to a predetermined concentration in a chest tank. , A method such as adjusting the concentration to a predetermined concentration by adding water between the chest tank and the head box after aggregating synthetic fluoromica or synthetic fluoromica and micro glass fiber in the adjustment tank or chest tank. Although any method can be considered, there is no particular limitation on the adjusting method.

In the slurry of the synthetic fluoromica in the present invention, if necessary, inorganic pigments, inorganic fibers other than micro glass fibers, inorganic binders, organic pigments, organic dyes, organic fibers, organic binders, surfactants, You may add additives, such as an antistatic agent, an antioxidant, and a defoaming agent.

The wet papermaking according to the present invention may be carried out according to a usual papermaking method. For example, as the papermaking machine to be used, a fourdrinier paper machine, a cylinder papermaking machine, a combination machine combining two or more kinds, and an inclined type papermaking machine. A paper machine or the like is used.

The basis weight of the mica sheet according to the present invention is preferably ²⁰ to 300 g / m ² . If the basis weight of the mica sheet is less than 20 g / m ² , a uniform sheet is obtained by the wet papermaking method.
When it is difficult to obtain the sheet weight and the basis weight is more than 300 g / m ² , the flexibility of the sheet is lost and the sheet becomes a board shape.

[0029]

EXAMPLES The present invention will be described below in detail with reference to examples, but the contents of the present invention are not limited to the examples. In addition, "parts" means parts by weight.

The physical properties of the mica sheets obtained in Examples and Comparative Examples were measured by the following methods. The results are shown in Table 1.

<Tensile Strength> Tensile strength is JIS
-It carried out using the Tensilon testing machine according to the method prescribed | regulated to P8116. The width of the sample was 25 mm.

<Folding endurance> For the folding endurance, 1
When it was folded back to 80 degrees and returned to the original state again, the judgment was made according to the following criteria. Did not cut at the folding mouth: ○, did not cut but some cracks were observed:
△, cut: ×.

<Dielectric Breakdown Strength> The dielectric breakdown strength is AST
According to the method defined in M-D149, the measurement was performed using a dielectric breakdown strength measuring device.

<Flame Retardancy> The flame retardancy is JIS-L1091.
In accordance with the method (A-4 method, vertical method) stipulated in 1., it was performed using a combustion test apparatus.

Example 1 98 parts of a 1% aqueous dispersion of a synthetic swelling fluoromica (made by Corp Corp.) and micro glass fiber (Schuller, # 110) in a weight ratio of 50/50 were mixed with 0.1% aluminum sulfate. 2 parts of the aqueous solution was gently added, mixed and stirred.
At the time of stirring, the stirring was adjusted so that floc-like aggregates of synthetic swelling fluoromica and micra glass fiber were formed, and care was taken so that the flocs were not destroyed by strong stirring. Next, water was added to the slurry containing the synthetic swelling fluoromica and the micro glass fiber so that the solid content concentration was 0.0.
The slurry was adjusted to 5% to obtain a papermaking slurry. Using this slurry with a cylinder paper machine, the basis weight is 100 g /
to prepare a mica sheet of m ^2. The physical properties of the produced mica sheet were measured, and the results are shown in Table 1.

Example 2 To 49 parts of a 1% aqueous dispersion of synthetic swelling fluoromica (manufactured by Corp Chemical), 2 parts of a 0.1% aqueous solution of aluminum sulfate was gently added, mixed and stirred. At the time of stirring, the stirring was adjusted so that a floc-like aggregate of the synthetic swelling fluoromica was formed, and care was taken so that the flocs were not destroyed by the strong stirring. Next, micro glass fiber (Schull
ER Co., # 110) 1% aqueous dispersion 49 parts, and then water to adjust the solid content concentration of the slurry consisting of synthetic swelling fluoromica and micro glass fiber to 0.05%. To obtain a papermaking slurry. Using this slurry, a mica sheet having a basis weight of 100 g / m ² was produced with a cylinder paper machine. The physical properties of the produced mica sheet were measured, and the results are shown in Table 1.

Example 3 As an aggregating agent, an anionic reverse phase polymer emulsion (ACCURAC303ES, manufactured by Mitsui Cyanamide)
A mica sheet was prepared in the same manner as in Example 1 except that was used, and the physical properties of the mica sheet were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 As a coagulant, basic aluminum chloride (manufactured by Mizusawa Chemical Co., Ltd.,
A mica sheet was prepared in the same manner as in Example 1 except that polyaluminum chloride PAC) was used, and the physical properties of the mica sheet were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 5 A mica sheet was prepared in the same manner as in Example 1 except that a cationic reverse phase polymer emulsion (MG1024, manufactured by Mitsui Cyanamid Co., Ltd.) was used as the coagulant.
The physical properties of the mica sheet were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 6 100 parts of a 1% aqueous dispersion of a synthetic swelling fluoromica (made by Corp Chemical) and a micro glass fiber (Schuller # 110) in a weight ratio of 50/50 was added to a cationic reverse phase polymer emulsion type. Gently add 2 parts of a 0.1% liquid of a flocculant (MG1024, manufactured by Mitsui Cyanamid Co., Ltd.), mix,
It was stirred. Further, 15 parts of a 0.1% liquid of anionic reversed-phase polymer emulsion type flocculant (ACCURAC303ES, manufactured by Mitsui Cyanamid) was gently added, mixed and stirred. At the time of stirring, the stirring was adjusted so that large floc-like aggregates of the synthetic swelling fluoromica and the micro glass fiber were formed, and care was taken so that the flocs were not destroyed by the strong stirring. Next, water was added to adjust the solid content concentration of the slurry to 0.5% to obtain a synthetic swelling fluoromica papermaking slurry. Using this slurry, a mica sheet having a basis weight of 100 g / m ² was produced with a cylinder paper machine.

Example 7 The weight ratio of synthetic fluoromica to microglass fiber was 85 /
A mica sheet was prepared in the same manner as in Example 1 except that the number was changed to 15. The physical properties of the mica sheet were measured in the same manner as in Example 1, and the results are shown in Table 1. Also, the detachment on the wire and the water-draining property at the time of fluoromica paper making were observed. Although the detachment on the wire was not a problem, the water-draining was a little bad.

Example 8 The weight ratio of synthetic fluoromica to microglass fiber was 15 /.
A mica sheet was produced in the same manner as in Example 1 except that the value was 85, and the physical properties of the mica sheet were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 9 A mica sheet was produced in the same manner as in Example 1 except that the concentration of the aggregate slurry of synthetic fluoromica and microglass fiber was 0.01%. The physical properties of the sheet were measured, and the results are shown in Table 1.

Example 10 A mica sheet was produced in the same manner as in Example 1 except that the concentration of the aggregate slurry of synthetic fluoromica and micro glass fiber was set to 1.8%, and the mica was prepared in the same manner as in Example 1. The physical properties of the sheet were measured, and the results are shown in Table 1.

Comparative Example 1 A mica sheet was prepared in the same manner as in Example 1 except that no coagulant was used for preparing a papermaking slurry of synthetic fluoromica and microglass fiber. Sometimes all of them passed through the wire and it was impossible to make mica sheet.

Comparative Example 2 A mica sheet was prepared in the same manner as in Example 1 except that the concentration of the papermaking slurry of synthetic fluoromica and microglass fiber was changed to 0.005%. The produced mica sheet had many pinholes and could not be said to be a good mica sheet. The physical properties of the mica sheet were measured in the same manner as in Examples, and the results are shown in Table 1. Further, the desorption and water-draining property on the wire during fluoromica paper making were observed, but synthetic fluoromica was often desorbed on the wire and it was difficult to form a mica sheet.

COMPARATIVE EXAMPLE 3 A mica sheet was prepared in the same manner as in Example 1 except that the concentration of the aggregate slurry of synthetic fluoromica and micro glass fiber was 2.5%. Was measured, and the results are shown in Table 1. The obtained sheet had poor uniformity and very poor texture.

Comparative Example 4 A mica sheet was produced in the same manner as in Example 1 except that the sheet was produced only from synthetic fluoromica, but the strength of the wet paper on a paper machine was weak and it was difficult to form a sheet. . Also,
Folding resistance was weak and it was difficult to collect it as a roll.

Comparative Example 5 A mica sheet was prepared in the same manner as in Example 1 except that the sheet was prepared from only micro glass fibers, but there was no binding force between the sheets and it was difficult to form a sheet.

[0050]

[Table 1]

[0051]

By the method for producing a mica sheet of the present invention, it is possible to produce a uniform mica sheet having excellent electric insulation, heat resistance and mechanical strength.

Claims (7)

[Claims] 1. Synthetic fluoromica and microglass fiber are dispersed in water, and an aggregating agent is added to the dispersion to form an aggregate of the synthetic fluoromica and microglass fiber,
Next, a method for producing a mica sheet, which comprises diluting the solid content concentration of the aggregate to 0.01 to 2% and making a paper by a wet paper making method using the diluted liquid. 2. Synthetic fluoromica is dispersed in water, an aggregating agent is added to the dispersion to form an aggregate of the synthetic fluoromica, and then microglass fiber is mixed with the agglomerate. A method for producing a mica sheet, which comprises diluting a solid content concentration to 0.01 to 2% and making a paper by a wet papermaking method using the diluted liquid. 3. The method for producing a mica sheet according to claim 1, wherein the weight ratio of the synthetic fluoromica and the micro glass fiber is 20/80 to 80/20. 4. The method for producing a mica sheet according to claim 1, 2 or 3, wherein the aggregating agent comprises at least one kind of anionic or cationic aggregating agent. 5. The method for producing a mica sheet according to claim 4, wherein the coagulant comprises at least one inorganic polyvalent cationic coagulant containing an aluminum atom. 6. The method for producing a mica sheet according to claim 4, wherein the flocculant is an anionic or cationic reverse phase polymer emulsion. 7. The method for producing a mica sheet according to claim 4, wherein the flocculant is a combination of at least one anionic reverse phase polymer emulsion and at least one cationic reverse phase polymer emulsion. .