JP3279796B2 - Sheet-shaped wholly aromatic polyamide molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel sheet-like wholly aromatic polyamide molded article and a method for producing the same. More specifically, it has heat resistance, excellent mechanical properties, dimensional stability, and flame retardancy, good electrical insulation, especially good corona resistance, and excellent surface smoothness and moldability. The present invention relates to a sheet-like wholly aromatic polyamide molded product suitable for use as an electrical insulating material and a method for industrially producing the same.

[0002]

2. Description of the Related Art In recent years, electrical equipment, especially transformers, electric motors,
As a result of the demand for higher capacity and smaller size of closed-system heat-generating devices such as converters, a wholly aromatic polyamide sheet-like molded product called aramid sheet or aramid board will be used as an insulating material with better heat resistance. Became.

[0003] However, in fields where a high level of electrical insulation, such as ordinary aramid sheets and aramid boards, is required to surpass the durability (particularly corona resistance) of organic electrical insulation materials, large natural mica, which is an inorganic substance, is used. Although stripped products have been used, high-quality and large-sized natural mica has a limited amount of production and is expensive, and in addition, stripped products have poor flexibility, and thus have various problems in moldability. Was.

[0004] Instead of such a natural mica stripping product, a small amount of polymer fibrid is uniformly mixed with finely divided aggregated mica as an easily available raw material to form a paper, which is then subjected to a heat and pressure treatment to provide a reinforcing material. (Japanese Patent Application Laid-Open Nos. Sho 57-149703 and 57-1673)
No. 74, etc.). However, the sheet bonded to the reinforcing material by such a heat and pressure treatment is difficult to exhibit the required strength and lacks flexibility, so that it cannot sufficiently meet the complicated processing demands of electric and electronic parts. was there.

There has also been proposed an attempt to obtain a high-temperature-resistant sheet-like structure from a entangled mixture of granular mica and substantially unfused wholly aromatic polyamide fibrid (Japanese Patent Publication No. 43-20421). JP-A-1129097). However, in this method, among the mixed mica particles, those having a relatively small particle diameter are difficult to be trapped by the wholly aromatic polyamide fibrid, so that they are easily dropped off during the heat compression molding after the sheet is formed. There was a problem of causing variations.

It is also possible to form a so-called mica-containing pulp in which mica particles are covered and connected with a wholly aromatic polyamide, and to form a sheet aimed at improving oil impregnating property from the mica particles and the wholly aromatic polyamide fibers. It is known (see JP-B-52-35763, JP-B-53-7961 and U.S. Pat. No. 4,060,451). This mica-containing pulp is excellent in adhesiveness to a wholly aromatic polyamide fiber and can be expected to prevent fine mica particles from falling off, but is disadvantageous in practical use because a complicated pulp-containing pulp production step is required.

[0007]

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a sheet-like wholly aromatic polyamide molded article suitable as an electrical insulating material having good mechanical (mechanical) properties and moldability. Is to provide. Another purpose is
In such a molded product, improved electrical insulation, especially improved long-term durability under a constant load voltage, which is important for practical use, so-called corona resistance, and surface smoothness based on an effect of preventing fine mica particles from falling off were realized. It is to provide a sheet-like wholly aromatic polyamide molded product. Another object is to stably introduce inorganic mica particles into a sheet-like wholly aromatic polyamide molded article, thereby having flame retardancy, and an electrical insulating material having a small dimensional change due to temperature change and moisture absorption. To provide a sheet-like wholly aromatic polyamide molded article useful as a material.

It is still another object of the present invention to provide a method for efficiently producing the above sheet-like wholly aromatic polyamide molded article.

[0009]

SUMMARY OF THE INVENTION The above-mentioned object is achieved by the following method.
From an aqueous dispersion containing 0% by weight of mica particles and 90 to 10% by weight of a wholly aromatic polyamide stock (i.e., wholly aromatic polyamide fibrids or both thereof and wholly aromatic polyamide fibers) as main components. A sheet-like molded product obtained by wet molding, which is prepared by adding a nonionic polymer flocculant to the above aqueous dispersion at the time of wet molding, and has a corona durability (load voltage of 20 KV / mm, AC frequency of 1, 000H
This is achieved by the sheet-like wholly aromatic polyamide molded article of the present invention, wherein z) is at least 150 minutes.

The sheet-like wholly aromatic polyamide molded product is preferably prepared from an aqueous dispersion mainly containing 10 to 90% by weight of mica particles and 90 to 10% by weight of a wholly aromatic polyamide paper stock. In wet-molding the sheet-like material, preferably, a mica particle using a surface-treated with a silane coupling agent, and, by adding a nonionic polymer flocculant to the aqueous dispersion, heat resistance,
It is manufactured by a method of obtaining a sheet-like wholly aromatic polyamide molded article having excellent mechanical properties, dimensional stability, flame retardancy, electrical properties, surface smoothness and the like.

Hereinafter, the method of the present invention will be described in detail.

In the present invention, the mica used as one of the raw materials does not necessarily have to be a single plate-like material. "It doesn't matter. The type of mica may be any of muscovite, sericite, phlogopite, biotite and the like as long as it does not contain magnetic foreign matter (for example, iron powder) or large foreign matter (for example, silica particles).
Among these, glued mica of muscovite is particularly practical.

According to the present invention, it is possible to make full use of the aggregated mica having a wide particle size distribution, which is one of the advantages of the present invention. That is, when wet-forming a sheet from mica particles and a wholly aromatic polyamide stock, even if it contains fine particles (powder) that pass through a 250-mesh sieve, for example, the electrical characteristics of the obtained molded product (Especially corona resistance) does not deteriorate.

Of course, there is a method of removing mica having a particle size smaller than a certain limit beforehand in order to prevent fine mica particles from falling off. However, for industrial implementation, a separate separation step is required. In view of the fact that the treatment of the remaining fine powder mica becomes a problem, the steps become complicated and the cost is disadvantageous.

[0015] The amount of mica particles added is 10 to 9 based on the total components of the sheet including the wholly aromatic polyamide stock.
It must be 0% by weight. If it is less than 10% by weight, the effect of adding mica is not sufficient, and if it exceeds 90% by weight, the mechanical strength and electrical properties of the obtained molded product are undesirably reduced. The preferred range of the added amount of mica particles is 30 to 70% by weight.

[0016] The other raw material, "wholly aromatic polyamide paper stock", is dispersed in water, then paper-formed and dried.
If necessary, it is defined as a raw material from which a sheet-like wholly aromatic polyamide molded article can be manufactured by thermocompression bonding or preforming with a wire mesh mold, followed by drying and thermocompression bonding. The constituent component is specifically a fibrid of a wholly aromatic polyamide (pulp-like particles obtained by precipitating a solution of a wholly aromatic polyamide in a coagulation bath to which a shearing force is applied, for example, Japanese Patent Publication No. 35-11851). And the fiber.

That is, the wholly aromatic polyamide stock used in the present invention is composed of wholly aromatic polyamide fibrids and wholly aromatic polyamide fibers added as needed. Fibrids are often beaten to the extent that they do not interfere with drainage during wet molding from an aqueous dispersion,
It is preferable from the viewpoint of improving the mechanical and electrical properties of the obtained molded product. The preferred freeness range varies depending on the basis weight of the molded product, the mixing ratio of the mica particles, the fineness distribution, and the like, but it is preferably within a range of 80 to 200 ml in Canadian standard freeness (CSF).

The compounding ratio (content) of the wholly aromatic polyamide stock to all the constituent components of the sheet-like molded product is 90 to 90%.
10% by weight. If the compounding ratio exceeds 90% by weight, the obtained molded product has insufficient electrical insulation. On the other hand, if the content is less than 10% by weight, the mechanical properties and electrical insulation of the molded product are impaired, which is not preferred. A preferred compounding ratio of the wholly aromatic polyamide stock is 70 to 30% by weight.

In the above-mentioned paper stock, it is preferable to use a wholly aromatic polyamide fiber in addition to the wholly aromatic polyamide fibrid, because the mechanical properties of the obtained molded article are improved. The amount of fibers is suitably not more than 30% by weight of all components of the molded product. If the fiber content exceeds 30% by weight, the electrical insulation is impaired, which is not preferred. A more preferable range of the fiber amount is 5 to 20% by weight.

As such wholly aromatic polyamide fibers,
Those manufactured by any of dry spinning, wet spinning and semi-dry semi-wet spinning can be used. Usually fineness 0.1
Short fibers having a denier of 10 to 10 and a length of 3 to 20 mm are preferably used.

The wholly aromatic polyamide mentioned here is a general term for polymers in which an amide bond (—NH—CO—) is directly bonded to an aromatic ring. In the present invention, as the wholly aromatic polyamide, 80 mol% or more, particularly 90 mol% of the repeating unit is used.
A polymer consisting of m-phenylene isophthalamide of the following formula (I), a polymer consisting of p-phenylene terephthalamide of the following formula (II), and / or p-phenylene terephthal of the following formula (II) in which at least mol% is present. Amide and the following formula (II
A copolymer comprising 3,4'-diphenylether terephthalamide of I) is preferably used.

[0022]

Embedded image

Of course, a small amount of other copolymer components may be introduced as long as the basic physical properties of these polymers are not significantly impaired.

However, in the present invention, the poly (m
-Phenyleneisophthalamide) fibrids and fibers are preferably used. As the poly (m-phenylene isophthalamide) fiber, a fiber that has been subjected to a drawing heat treatment is generally used, but a fiber that is not subjected to a heat treatment after drawing may be used.
It is also possible to mix a small amount (for example, 20% by weight or less, particularly 10% by weight or less, of the entire stock) with another polymer (such as polyethylene terephthalate) as the stock.

As described above, a sheet-like molded article of a wholly aromatic polyamide containing mica particles has been well known, but as a result of the study of the present inventors, mica particles having a wide particle size distribution have been obtained. After dispersing a wholly aromatic polyamide paper stock in water at a predetermined ratio, when performing paper shaping by a paper machine or preforming by a wire mesh form, a small amount of a nonionic polymer flocculant is coexistent in the aqueous dispersion. And the mica mixing effect is significantly enhanced, and a corona durability of 150 minutes or more (load voltage 20 KV / mm, AC frequency 1,100), which cannot be achieved with the conventional mica particle-containing wholly aromatic polyamide sheet-like molded product.
0 Hz) can be realized.

Preferred examples of the nonionic polymer flocculant include, for example, "Acofloc (registered trademark) N-100" and "Acofloc (registered trademark)" manufactured by Mitsui Cyanamid.
102 ", Konan Floc (registered trademark) ZH-760 of Konan Chemical Industry Co., Ltd.," Cliff Rock (registered trademark) PN-162 "and" Cliff Lock (registered trademark) PN-131 "of Kurita Industry Co., Ltd. , Diafloc Co., Ltd. “Acrypers (registered trademark)”, Sumitomo Seika Co., Ltd. “P
EO-PF "and polyacrylamide or polyethylene oxide-based polymer compounds.

In the present invention, the amount of the nonionic polymer coagulant added to the aqueous dispersion for molding depends on the solid content of the aqueous dispersion, but is usually 0.01 to 100 pp.
m or 0.0 with respect to solid content (sheet component)
It is in the range of 5 to 1.0% by weight. Below this lower limit, the effect of adding the nonionic polymer flocculant is not sufficiently exhibited. On the other hand, if the ratio exceeds the upper limit, the viscosity of the aqueous dispersion is remarkably increased, so that the drainage property is deteriorated and the electrical properties of the obtained molded product are deteriorated. A more preferred range is 0.1 to 20 ppm based on water. The nonionic polymer flocculant can be used without problems for a wide range of pH water (pH 3 to 10).

In a preferred embodiment of the present invention, the mica particles are preliminarily subjected to a silane coupling treatment, and then subjected to wet forming of a sheet.

As a method of treating the surface of the mica particles with the silane coupling agent, a method known per se can be used. For example, a method of dipping the mica particles in an aqueous solution or an organic solvent solution containing the silane coupling agent. An ordinary method such as a method of applying the solution to the mica particles by spraying is applied. In this case, if mica particles dispersed in advance in a size suitable for wet molding are used, the surface treatment can be performed efficiently.

As the silane coupling agent to be used,
Alkoxysilane-based coupling agents are preferred. In this case, there is no particular limitation on the number of alkoxy groups substituted on the silicon atom.

The amount of the silane coupling agent used to treat the surface of the mica particles (the amount of the silane coupling agent added to the treatment solution) depends on the amount of silanol groups present on the surface of the mica particles, the mica to be treated. It can be determined by the surface area of the particles, the type of silane coupling agent used, etc.,
Practically, 0.001 to 1 with respect to the mica particles to be treated.
A range of 0% by weight is preferably selected. Since the silane coupling agent is usually applied in a state of being diluted with an aqueous solution or an organic solvent, a method of adjusting the concentration of the silane coupling agent in the solution is simply adopted. A preferred concentration is 0.01 to 5% by weight when the medium to be subjected to silane coupling treatment is an aqueous solution, and 0.01 to 50% by weight when the medium is diluted with an organic solvent.

In the case of silane coupling treatment,
The pH of the medium can be adjusted as needed.

The sheet-shaped molded product of the present invention comprises mica particles which have been subjected to silane coupling treatment (or untreated), fibrids adjusted to a desired freeness, and a distribution amount of fibers falling within the above-mentioned range. In a state where the nonionic polymer flocculant is added to the aqueous dispersion containing the wholly aromatic polyamide paper stock,
The wet molding is performed, and a sheet-like molded product is formed.

As a means for wet molding, a papermaking method or a pulp molding method is employed. Specifically, in order to produce the sheet-like aramid molded article of the present invention, for example, a predetermined amount of the mica aggregate subjected to a silane coupling treatment is placed in an appropriate water and slowly stirred to be dispersed in fine particles. On the other hand,
For the wholly aromatic polyamide stock, a fibrid adjusted to have a desired freeness by a known method and a predetermined amount of fiber to be added as needed are taken in a chest (tank with a stirrer) provided with water. . Next, the mica dispersion water is transferred to this chest and stirred well. A predetermined amount of the nonionic polymer flocculant is preferably added in this chest. In the case of addition during papermaking, it may be added continuously to the transport aqueous dispersion in the subsequent step, or may be added to the first mica dispersion water. This polymer flocculant is
Usually, since it is commercially available as a solid or concentrated aqueous solution, it is convenient in production to adjust the aqueous solution to a concentration of 1 to 5% by weight before use.

For papermaking, any of ordinary circular net, short net, and long net paper machines can be used. The wet web (wet paper) thus obtained is dehydrated and dried to form a paper-like sheet. If necessary, after laminating a plurality of such sheets, the sheets can be heated and pressed to enhance the adhesion between the materials constituting the sheets. The preferable pressure for the heating and pressurizing treatment is a surface pressure of 10 to 100 kg / cm ² and a linear pressure of 1
0 to 500 kg / cm can be mentioned, and a preferable temperature is 230 to 330 ° C.

As another example of wet molding, there is a so-called pulp molding method. In this case as well, after molding by the pulp molding method, heating and pressing can be performed within the above-mentioned pressure temperature range.

When a three-dimensional (three-dimensional) sheet-like molded product is required, for example, an appropriate amount of the contents is taken from the above-mentioned chest into a large container, and a wire netting form equipped with a suction device is put into the container and subjected to suction molding. Alternatively, a method of preforming by a so-called pulp molding method, followed by drying and then compression molding with a mold having a predetermined shape may be adopted. The optimum temperature and pressure at this time vary depending on the constituents of the slurry, but are respectively about 230 to 330 ° C. and a surface pressure of 10 to 100 kg / cm ² .

By the above method, the desired sheet-like wholly aromatic polyamide molded product is efficiently and economically produced.

According to the present invention, the mica having a wide range of particle size distribution can be used. That is, when the mica is dispersed in water and mixed with a wholly aromatic polyamide paper material, the mica is passed through a 250-mesh sieve. The characteristic feature is that even if such a fine powder is contained, the electrical properties of the molded product, in particular, the corona durability are not impaired. When using those with a wide particle size distribution, there is a convenient way to cut mica with a particle size below a certain limit in advance, but at the time of industrial production, a fractionation process is necessary, Considering the problems described above, the process becomes complicated and disadvantageous in cost.
In the present invention, there is no need for this, which is industrially advantageous.

The agglomerating effect of the mica fine powder can be observed not only with the nonionic polymer flocculant but also with the anionic polymer flocculant and the cationic polymer flocculant, but the latter two impair the electrical characteristics. Not suitable.

Thus, the sheet-like molded product of the present invention has a corona durability of 150 minutes or more as measured by the method described below.
Preferably, the time is 300 to 700 minutes, and the corona resistance is significantly improved as compared with the case where the nonionic polymer flocculant is not used.

Further, the fluctuation of the corona durability is small, and the fluctuation rate measured by the method described later is within the range of 30% or less. Further, the surface smoothness is also good, and shows a value of 6.5% or more when expressed by Beck smoothness.

The thickness and basis weight of the sheet-like molded product of the present invention can be arbitrarily selected according to the intended use, but usually the thickness is 0.05 to
1.0 mm, preferably 0.1-0.5 mm, basis weight 50-1
000 g / m ² , preferably in the range of 100 to 500 g / m ² .

[0044]

According to the present invention as described above, electrical characteristics,
A sheet-like wholly aromatic polyamide molded article having excellent heat resistance, mechanical properties, dimensional stability, flame retardancy, and the like is provided. Further, among the electrical properties of the molded article, the corona resistance,
The average value of the corona durability is improved, and there is a unique effect that the variation is reduced, and the electric insulation (dielectric breakdown voltage) is also improved. In practice, since the design of the electrical insulating material is made in consideration of the lower limit value of the variation, not the average value of the performance, the molded product according to the present invention is particularly useful for improving the reliability of the material.

Further, the molded article according to the present invention has an advantage that surface smoothness, dimensional stability, and moldability are good. Accordingly, molded articles such as paper, sheet, board and the like according to the present invention are particularly useful as electric insulating materials.

Moreover, in the present invention, relatively inexpensive "mica mica" can be used without sieving.
Another advantage is that the desired molded product can be obtained very economically.

The above effects are particularly remarkable when mica particles are previously treated with a silane coupling agent. Although the basis for the synergistic effect of the combined use of the silane coupling treatment of mica particles and the addition of the nonionic polymer flocculant to the aqueous dispersion is not always clear, the capture of the mica particles by the nonionic polymer flocculant is not clear. The effect is promoted and the electrical properties and mechanical properties of the sheet-like wholly aromatic polyamide molded article as described above are improved as a result of the interaction between the wholly aromatic polyamide stock and the mica particles being enhanced by the silane coupling treatment. It is estimated to be.

[0048]

Next, the present invention will be described in detail with reference to examples and comparative examples. However, they do not limit the content of the present invention at all. Each characteristic value shown in the examples is a value obtained by the following measurement method. It is to be noted that simply “parts” indicates parts by weight. (A) Breakdown voltage (BDV): conforms to JIS-C2111. It was measured by AC voltage (unit: KV / mm). (B) Corona durability: 20 ° C., 65% RH, frequency 1,
Under 000 Hz and AC voltage of 20 KV / mm load voltage, the time (unit: minute) until 5 out of 10 test pieces break down.
Indicated by (C) Corona durability fluctuation rate: In the above corona durability test, the difference between the second sample destruction time (first is excluded because other factors are easy to enter) and the fifth sample destruction time (corona durability) is corona. It was divided by the durability and expressed as a percentage (unit;%). (D) Surface smoothness: Measured according to a measurement method using a JIS-P8119 (1976) Beck tester (unit:
Seconds).

Examples 1 to 3 and Comparative Examples 1 to 3 (a) Preparation of fibers and fibrids Poly (m-phenylene isophthalamide) produced by an interfacial polymerization method based on the method of Japanese Patent Publication No. 47-10863
A polymer (intrinsic viscosity of 1.35 measured by dissolving in N-methyl-2-pyrrolidone) was dissolved in N-methyl-2-pyrrolidone to prepare a dope. This dope was extruded through a spinning nozzle having a large number of arranged pores into a coagulating liquid composed of an aqueous solution of an inorganic salt to form a yarn. This was washed with water, stretched and heat-treated, and then wound up to obtain a fiber. This fiber has a fineness of 2.0
Denier, strength: 5.8 g / de, elongation: 40%.
The fiber was cut into 6 mm.

On the other hand, a shear field (mixing of water and N-methyl-2-pyrrolidone) produced by rotating a metal cylinder (rotor) having projections into which a dope of poly (m-phenylene isophthalamide) prepared separately was produced. (Filled with liquid) to coagulate and precipitate the polymer to form a fibrid.
After washing the fibrid with water, beating it in the usual way,
The Canadian standard freeness (CSF) was 170 ml.

These fibers and fibrids were used for papermaking.

(A) Particle Size Distribution of Mica Particles The whole amount of the mica particles passed through a 16-mesh sieve using a wet sieve method, a distribution peak was present around 60 mesh, and 7% of the 250-mesh sieve passed 7%. CZ
2T) was subjected to this experiment.

(C) Preparation of sheet Fibrid (P) and fiber (F) prepared in (A) above
And a total of 75 parts of the mica particles (M) described in (a) above, with a blending ratio (weight ratio) of P / F / M = 60/1.
0/30 (Example 1), P / F / M = 40/10/50
(Example 2), P / F / M = 20/10/70 (Example 3).

Next, 0.075 parts (0.1% by weight based on the total amount of the raw materials) of polyacrylamide (trade name “Acrypers” manufactured by Diafloc) were added as a nonionic polymer flocculant to these aqueous dispersions. And stirred at room temperature for about 1 minute. Acrypers nonionic polymer flocculant
Is a 1% aqueous solution, and 0.1% as an agent component (non-aqueous component).
% By weight.

This dispersion slurry was formed on a round paper machine having a paper width of 60 cm, dried with a Yankee dryer at 130 ° C., and wound up on a roll (papermaking speed 2 m / min). Immediately after taking out the sheet from these two rolls and passing through the preheating layer at 290 ° C., the sheet is passed through two metal rolls having a set temperature of 300 ° C. and a linear pressure of 200 kg / cm, and is subjected to laminating calendering (processing speed 2 m / min) A paper-like sheet was obtained. Table 1 below shows the sheet properties in each case.

For comparison, exactly as in Examples 1-3,
However, papermaking and calendering were performed without adding a nonionic polymer flocculant (Comparative Examples 1 to 3). The sheet properties in these cases are also shown in Table 1.

[0057]

[Table 1]

These experiments confirmed the effect of the addition of the nonionic polymer flocculant.

[Examples 4 to 8, Comparative Example 4] (d) Preparation of sheet A total of 75 parts of the same fibrids and mica particles as used in Examples 1 to 3 were mixed in the mixing ratio (weight ratio) shown in Table 2 below. )
Was dispersed in water about 600 times so that Next, 0.15 parts (0.2% by weight based on the total amount of the raw materials) of a nonionic polymer flocculant “Acrypers” was added to each aqueous dispersion, and the mixture was formed in the same manner as in (C) of Examples 1 to 3. Dry,
Wound on a roll. Next, laminating calendering was performed by the same method to produce a sheet (Examples 4 to 5).
8). Table 2 shows the sheet properties in each case.

For comparison, a similar experiment was conducted for the case where no mica particles were contained (Comparative Example 4). Table 2 shows the results.
It is described together.

[0061]

[Table 2]

From these experiments, it was found that the amount of mica particles to be added to the electrical insulation, particularly the corona durability, was 10 to 90% by weight, preferably 30 to 70% by weight.

[Examples 9 to 11] In Examples 1 to 3, polyethylene oxide (trade name “PEO-PF”) was used instead of polyacrylamide (“Acrypers”) as the nonionic polymer flocculant. Co., Ltd.)
Papermaking, drying and calendering were performed in exactly the same manner except that 1% by weight was used. Table 3 shows the results.

[0064]

[Table 3]

From these experiments, it was confirmed that polyethylene oxide was also extremely effective in improving the electrical insulation of mica-mixed paper.

The above Examples 1 to 11 were replaced with Comparative Examples 1 to
By contrast with No. 4, the surface smoothness is improved by the addition of a coagulant in the case of mica-mixed paper, and in the case of 100% aramid paper containing no mica (Comparative Example 4), a remarkable effect is obtained. It is understood that it is not allowed.

Examples 12 to 14 (e) Preparation of fibrids and fibers Polymers of poly (m-phenylene isophthalamide) were produced by an interfacial polymerization method based on the method of Japanese Patent Publication No. 47-10863. The intrinsic viscosity of this polymer measured by dissolving it in N-methyl-2-pyrrolidone is 1.35 and does not contain inorganic salts.

The polymer was made into fibers based on a wet spinning method using a calcium chloride aqueous solution described in JP-B-48-17551 and using a coagulation bath. The fiber stretched in boiling water and further stretched on a hot plate had a tensile strength of 4.5 g / de and an elongation of 18%. This was cut to a length of 6 mm.

Similarly, the above polymer was converted to N-methyl-2-
The fibrid was dissolved in pyrrolidone, and a fibrid was prepared using a precipitation apparatus (150 mm in diameter) described in JP-A No. 52-15621, in which a shear force was applied by combining a stator and a rotor. This was beaten with a disc refiner. The resulting fibrid has a freeness of 11 Canadian freeness.
It was 0 ml.

(F) Particle size distribution of mica particles As in Examples 1 to 3, the whole amount passed through a 16-mesh sieve by a wet sieving method, a distribution peak existed at around 60 mesh, and the amount passed by a 250-mesh sieve was 7%. % Of hard-fired mica (Nippon Mica Seisakusho, CZ2T) was used in this experiment.

(G) Silane Coupling Treatment of Mica Particles 0.38 parts of the mica aggregates described in (f) and 100 parts of water were mixed and dispersed in a pulper. To this was added 0.01 part of N- (triethoxysilylpropyl) urea (2.6% by weight with respect to mica), which was a silane coupling agent, and the mixture was gently stirred for 1 hour. The mica particles were subjected to the next step.

(H) Preparation of sheet-like molded product The poly (m-phenyleneisophthalamide) fibrid (P) and fiber (F) prepared in the above (e) were subjected to the silane coupling treatment in the above (g). A total of 75 parts of the mica particles (M) obtained were mixed in a blending ratio (weight ratio) of P / F
/ M = 60/10/30, P / F / M = 40/10/5
0 and about 60 so that P / F / M = 20/10/70
It was mixed and dispersed in 0 times water. Next, 0.075 parts (1.7 ppm in water, 0.1% by weight based on solid content) of polyacrylamide ("Acrypers" (registered trademark) manufactured by Diafloc) was added as a nonionic polymer flocculant. And stirred. In addition, for "Acrypers", a method of adding a required amount of a previously prepared 1% aqueous solution was employed.

The dispersion slurry was formed at a rate of 2 m / min by a fourdrinier paper machine, dried by a Yankee dryer at 130 ° C., and wound around a roll. Sheets were taken out from the two rolls, and two sheets were laminated and calendered under the conditions of a temperature of 300 ° C. and a linear pressure of 200 kg / cm. Table 4 shows the physical properties of the obtained sheet-like molded products.

[0074]

[Table 4]

Example 15, Comparative Example 5 The same method as in Examples 12 to 14 was used except that the silane coupling agent was changed to trimethoxysilylpropyldiethylenetriamine.
Papermaking under conditions, raw material composition (weight ratio) is P / F / M = 40
/ 10/50 sheet, and the obtained sheet is 25
Two sheets were laminated and calendered at 0 ° C. and 150 kg / cm.

For comparison, papermaking was carried out by the same method and under the same conditions as described above, but without the use of the silane coupling agent treatment and the use of the polymer flocculant, and similarly calendered (Comparative Example 5).

Table 5 shows the results of both.

[0078]

[Table 5]

[Example 16] In the same manner as in Example 15, after the silane coupling agent solution treatment,
The mica particles which were not dried at 2 ° C. for 2 hours were subjected to papermaking to produce a sheet-like molded product. Its raw material composition,
Table 6 shows the amount of the silane coupling agent used, the amount of the coagulant used, the basis weight and the thickness of the sheet, and the like. Table 7 shows the physical properties of the obtained sheet.

[0080]

[Table 6]

[0081]

[Table 7]

Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI // D01F 6/60 371 D01F 6/60 371A (56) References JP-A-48-100451 (JP, A) JP-A-52-99304 ( JP, A) JP-A-1-104900 (JP, A) JP-A-61-86473 (JP, A) JP-A-2-142015 (JP, A) JP-A-58-36299 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) D21H 11/00-27/42 D21J 1/00-7/00

Claims (13)

(57) [Claims] 1 to 10% by weight of mica particles and 90 to 1% by weight
A sheet-like molded product obtained by wet molding from an aqueous dispersion containing 0% by weight of a wholly aromatic polyamide paper stock as a main component, containing a nonionic polymer flocculant and having a corona durability. A sheet-like wholly aromatic polyamide molded article, wherein the degree (load voltage 20 KV / mm, AC frequency 1,000 Hz) is 150 minutes or more. 2. The wholly aromatic polyamide paper stock is wholly aromatic polyamide fibrid and wholly aromatic polyamide fiber,
The sheet-like wholly aromatic polyamide molded article according to claim 1, wherein the content of the wholly aromatic polyamide fiber is 30% by weight or less based on all the constituent components of the sheet-like molded article. 3. The wholly aromatic polyamide is substantially poly (m
The sheet-form wholly aromatic polyamide according to claim 1 or 2, which is -phenyleneisophthalamide), poly (p-phenyleneterephthalamide) and / or copoly (p-phenylene / 3,4'-diphenylether terephthalamide). Moldings. 4. The sheet-like wholly aromatic polyamide molded article according to claim 1, wherein the nonionic polymer flocculant is substantially a polyacrylamide and / or a polyethylene oxide compound. 5. The sheet-like wholly aromatic polyamide molded article according to claim 1, wherein the mica particles are subjected to a silane coupling treatment. 6. The sheet-like wholly aromatic polyamide molded product according to claim 1, wherein the variation rate of the corona durability is within 30%. 7. The sheet-like wholly aromatic polyamide molded article according to claim 1, which is hot-pressed after wet molding. 8. A composition comprising 10 to 90% by weight of mica particles and 90 to 1% by weight.
In wet-forming a sheet from an aqueous dispersion mainly containing 0% by weight of a wholly aromatic polyamide paper stock, a nonionic polymer flocculant is added to the aqueous dispersion at a ratio of 0.01 to 100 ppm. And forming the sheet-like wholly aromatic polyamide molded product into a sheet by a papermaking method or a pulp molding method. 9. The method for producing a sheet-like wholly aromatic polyamide molded product according to claim 8, wherein mica particles which have been previously surface-treated with a silane coupling agent are used. 10. The method for producing a sheet-like wholly aromatic polyamide molded article according to claim 8, wherein the nonionic polymer flocculant is a polyacrylamide and / or a polyethylene oxide compound. 11. A wholly aromatic polyamide fibrid and a wholly aromatic polyamide fiber are used as a wholly aromatic polyamide stock, and a wholly aromatic polyamide fiber is used in an amount of 30% with respect to all components of a sheet-like wholly aromatic polyamide molded product. The method for producing a sheet-like wholly aromatic polyamide molded product according to claim 8, which is used at a ratio of not more than% by weight. 12. Mica particles and a wholly aromatic polyamide paper material are dispersed in water, then wet-molded into a sheet, dried, and, if necessary, laminated two or more sheets, and then heated and pressed. The method for producing a sheet-like wholly aromatic polyamide molded product according to any one of claims 8 to 11, characterized in that: 13. The heating and pressurizing is performed at a temperature of 230 to 330 ° C.
The method is carried out under a linear pressure of 10 to 500 kg / cm.
A method for producing the sheet-like wholly aromatic polyamide molded article according to the above.