JPS5947079B2 - sheet - Google Patents

Description

[Detailed description of the invention] The present invention relates to sheets.

More specifically, it is a sheet with improved mechanical properties such as strength and elongation, excellent heat resistance, electrical insulation impregnation properties, and is made of specific pulp particles and short aromatic polyamide fibers. The sheet is characterized in that short fibers having a dry heat shrinkage rate of 10% or more and short fibers having a dry heat shrinkage rate of less than 10% at 300° C. are mixed in a specific ratio.

Conventionally, natural pulp is the most well-known pulp particle used in paper, and paper made from natural pulp is often used as electrically insulating paper. However, paper made from natural pulp has the major drawback of lacking heat resistance, and its heat resistance is far from the heat resistance required to reduce the size and weight of electrical equipment such as electric motors and transformers. Recently, pulp particles obtained from synthetic polymers have attracted attention as a material for electrically insulating paper because of their excellent heat resistance and electrical insulation properties.

For example, in Japanese Patent Publication No. 43-20421, 110~
A high temperature resistant sheet-like structure suitable for electrical insulation comprising 90% by weight of granular mica and 90-10% by weight of substantially unfused aromatic polyamide fibrids. 210-9
A high temperature resistant sheet-like structure consisting of 0% by weight granular mica, 90-10% by weight aromatic polyamide fibrids, and up to 30% by weight aromatic polyamide fibers.

It is written about.

Although the sheet-like structure described herein has excellent high temperature resistance, its mechanical properties such as strength and elongation are not sufficient. Furthermore, Japanese Patent Publication No. 49-42852 describes a method for improving the quality of high temperature resistant aromatic polyamide paper by immersing it in a sorbate solution. This sorbate solution consists of dimethyl-sulfoxide, N
3N-dimethylformamide, N,N-dimethyl-acetamide, N-methyl-2-pyrrolidone, while the inert diluent used at the same time is selected from the group of toluene, acetone, methyl ethyl ketone. Such a diluent consists of an organic solvent and, during processing,
This is not preferable because the inert diluent evaporates significantly and the concentration of the treatment liquid changes greatly.

In addition, we have conventionally used the pulp particles and aromatic polyamide
In order to obtain a sheet consisting of short fibers, undrawn yarn was stretched in boiling water at 360°C as aromatic polyamide short fibers.
Only short fibers with a dry heat shrinkage rate of less than 10% at 300°C obtained by heat treatment at a high temperature of It wasn't. In order to eliminate such drawbacks, the inventors of the present invention made extensive studies and found that in 10 sheets of pulp particles made of mica particles and an aromatic polymer and aromatic polyamide short fibers, 300 sheets of aromatic polyamide short fibers were used. By mixing short fibers with a dry heat shrinkage rate of 10% or more at °C and short fibers with a dry heat shrinkage rate of less than 10% in a specific ratio, it is possible to obtain products with improved mechanical properties such as strength and elongation. The present invention was completed in 15 cases. That is, the present invention provides a sheet made by mixing mica particles, pulp particles consisting of a heat-resistant and solvent-soluble aromatic polymer, and aromatic polyamide short fibers, making paper, and heating under pressure. In,
The aromatic polyamide short fibers are a mixture of short fibers having a dry heat shrinkage rate of 10% or more at 300°C and short fibers having a dry heat shrinkage rate of less than 10% at 300°C, and Mixing of short fibers with a dry heat shrinkage rate of 10% or more 25% of the total amount of short fibers in the sheet is within the range shown by diagonal lines in Figure 1 (however, points P, Q, R, S,
The coordinates of T are P (5%, 5%), Q (20%, 5%),
R (70%, 15%), S (70%, 90%), T (5
0%, 90%), (5%, 15%) (30%).

In the present invention, the heat-resistant and solvent-soluble aromatic polymer used has a solubility of at least 3% by weight or more, preferably 7% by weight or more at room temperature, and a stable solution. 35 refers to a polymer having the ability to form a pool and include the following.

Aromatic polyamide (1) A condensation polyamide of a highly active derivative of an aromatic dicarboxylic acid, preferably an acid halide, and a diamine having an aromatic ring.

For example, dicarboxylic acids such as terephthalic acid and isophthalic acid, diamines such as metaphenylene diamine, 4,4'
It may be a homopolymer consisting of a type of diamine using -diaminodiphenyl ether, 4,4'-diaminodiphenylmethane xylene diamine, N-methyl-paraphenylene diamine, etc., and a dicarboxylic acid component and a diamine. One or both of the components may be a copolymer consisting of two or more kinds of compounds. Typical examples include polymetaphenylene isophthalamide, polymethaxylene terephthalamide, a copolymer of metaphenylene diamine, isophthalic acid, and terephthalic acid, and poly-N-methylparaphenylene terephthalamide. .

(2) A polyamide in which an aminocarboxylic acid having an aromatic ring is preferably activated and condensed.

For example, the aminocarboxylic acid may be a homopolymer of only one type of aminocarboxylic acid such as para- or meta-aminobenzoic acid or para-aminomethylbenzoic acid, or a copolymer of two or more types of aminocarboxylic acids. A typical example is a condensate of para-aminobenzoic acid. (3) A polyamide obtained by copolymerizing the above (1) and (2).

A typical example is a polyamide obtained by condensing three components: metaphenylene diamine, isophthalic acid chloride, and para-aminobenzoic acid chloride hydrochloride. 2
Nitrogen-containing polyheterocyclic compound (1) Aromatic polyamideimide Ill Consists of a group selected from -N=N-, -Si-, and -P-0.

Here, R is an organic group having 1 to 10 carbon atoms, Y and Y' may be the same or different, and each is a hydrocarbon group having 1 to 6 carbon atoms, 1 halogen atom,
Alkoxy group having ~3 carbon atoms, Arylexy group having 1 to 3 carbon atoms, 2
Carbalkoxy group having ~10 carbon atoms, 1-5
is at least one selected from alkoxycarbonyl groups having carbon atoms.

m and n may be the same or different and are from 0 to 3.The polyamideimide of the above formula is composed of at least 70 mol%, preferably 85 mol% or more, and in particular, X is -CH2-,
-0-1SO2-, Y, and Y' are preferably a methyl group, a halogen atom, or a methoxy group, and M and n are preferably 0 or 1.

The polyamideimide contains up to 30 mol%, especially up to 15 mol%, of repeating units.

where R is an alkylene group having 2-15 carbon atoms. {,1,} or It is.

Polyamidebenzimidazole, aromatic polyimide, aromatic polyamide, polyazole such as polyoxazole, polyoxadiazole, polythiazole, polythiadiazole, polybenzazole such as polybenzimidazole, polybenzothiazole, polybenzoxazole, polyhydantoin, polyparaban It may also contain acids, polyquinazolinediones, polyquinazolones, polyquinoxalines, and polyoxazinones.

(2) Polyazole For example, polyoxazole, polyoxadiazole, polythiazole, polythiadiazole (3) Polybenzazole For example, polybenzimidazole, polybenzothiazole, polybenzoxazole (4) Polyhydantoin, polyparabanic acid, poly Quinazolinedione, polyquinazolone (5) polyquinoxaline,
Polyoxazinone 4 Precursor of nitrogen-containing polyheterocyclic compound (?) A polymer having units represented by the formula -HN-δU, -Nu.

(Precursor of polyamideimide) (2) Aromatic polyhydrazide (3) Aromatic polyamide hydrazide A polyamide hydrazide having a unit represented by the formula -δuδ-NHNH-.

These may have an inert substituent such as a methyl group, an alkoxyl group, or a halogen atom.

Precursors obtained by copolymerizing these precursors with aromatic dicarboxylic acids such as isophthalic acid and terephthalic acid, benzophenonetetracarboxylic anhydride, pyromellitic anhydride, etc. can also be used.

4 Aromatic polyether polyphenylene oxide, polyarylene oxide Mica particles contained in the pulp particles used in the present invention include muscovite, sericite, soda mica, rhodochite,
Examples include phlogopite, Chinwald mica, biotite, and synthetic mica.

The particle size of such mica particles is 6 by the Andreasenpipette method.
It is desirable that it be thinner than the equivalent of 0 mesh.

The amount of mica particles in the pulp particles used in the present invention is preferably 50 to 90% by weight. The amount of mica particles is 5
If the amount is less than 0% by weight, the effect of adding mica particles will not be very noticeable, and heat resistance and impregnation properties will not be good. Mica particle amount is 90
If the amount is more than % by weight, physical properties such as strength will be poor. Further, the amount of pulp particles in the sheet is required to be 30 to 95% by weight of the sheet.

The amount of pulp particles is 30 weight? If the amount is less, the dielectric breakdown voltage and strength and elongation of the paper will be low, which is not desirable.

(Region a in Figure 1) If the amount of pulp particles is more than 95%, the impregnating property etc. will be poor (Region b in Figure 1) The sheet in area c in Figure 1 is unfavorable as it has poor strength and elongation, especially elongation.

Also, the sheet in the d region has a dry heat shrinkage rate of 10 at 300°C.
% or more of short fibers is too small to improve mechanical properties such as strength and elongation.

When producing the pulp particles used in the present invention, a mixed solution obtained by adding and mixing mica particles to a solution in which the above polymer is dissolved may be used, or mica particles may be mixed when dissolving the raw material in a solvent. After that, the polymerized solution may be used.
A method can be applied in which a liquid mixture containing the polymer and mica particles is introduced into a precipitant and precipitated as fine particles to form pulp particles.

The solvent used in the above method includes a water-soluble solvent that dissolves the polymer and does not act on the mica particles;
For example, inorganic solvents such as sulfuric acid, hydrogen fluoride, fuming sulfuric acid, fluorosulfuric acid, chlorosulfuric acid, polyphosphoric acid, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide hexamethylphosphoric acid, etc. Organic solvents such as Ruamide, Tetramethylurea and the like are suitable.

Furthermore, a solvent system can be used in which the solubility of the polymer is increased by adding an inorganic salt such as lithium chloride or calcium chloride to the above-mentioned organic solvent.

The concentration of the polymer in the solution varies depending on the type of polymer and the degree of polymerization of the polymer, but is preferably approximately 2 to 15% by weight.

In addition, the precipitant used in the above method is preferably a liquid or solution that is miscible with the solvent of the polymer solution but is a non-solvent for the polymer. When an organic solvent is used as the solvent. The precipitating agent that can be used in It may be an aqueous solution in which it is dissolved.

n represents an integer of 1 to 4.

These salts include, for example, calcium chloride, lithium chloride, sodium chloride, magnesium chloride, zinc chloride,
Strontium chloride, aluminum chloride, tin chloride,
Examples include nickel chloride, calcium bromide, calcium nitrate, zinc nitrate, aluminum nitrate, sodium acetate, potassium thiocyanate, calcium thiocyanate, and especially calcium chloride, lithium chloride, aluminum chloride,
Examples include calcium thiocyanate and sodium acetate.

Among these, calcium chloride monoaqueous precipitants are preferred because they are easy to handle and inexpensive.

Among these various precipitants, aqueous precipitants are particularly preferred. During the production of the above-mentioned pulp particles, the precipitant is stirred at high speed to remove the solvent from the introduced solution and at the same time to produce a shearing or beating action. It is preferable to make paper from the above-mentioned pulp particles and short fibers by a wet process using a fourdrinier type or cylinder type paper making machine, as in the case of conventional paper making from natural pulp.

The short fibers used are fibers made of the aromatic polyamide mentioned above, and usually have a fineness of 0.5 to 10 and a denier fiber of 1 to 2.
It is desirable that the fineness is 1.0 to 2.0.
0 denier and a fiber surface of 3 to 81n are particularly preferred.

There is no problem in using a mixture of materials with different fiber surfaces.

Normally, in the production of aromatic polyamide fibers, a solution of an aromatic polyamide polymer is extruded into a coagulation bath, wet-spun, and stretched in boiling water (first stage stretching) to orient the molecular chains. Stretching and/or heat treatment (second-stage stretching, heat treatment) is performed on a hot plate or the like to promote crystallization and produce a product. At this time, by adjusting the first and second stage stretching ratios and the temperature of the second stage stretching heat treatment, the dry heat shrinkage rate at 300°C used in the present invention is 10% or more. and less than 10% yarn can be obtained. Furthermore, yarns that have been subjected to only the first-stage drawing and no second-stage drawing heat treatment, or completely undrawn yarns that have been extruded into a coagulation bath and then washed with water, can also be used at 300°C in the present invention.
It can be used as a fiber with a dry heat shrinkage rate of 10% or more.

It is also possible to use a mixture of two or more types of short fibers having a dry heat shrinkage rate of 10% or more at 300°C and one type or two or more types of short fibers having a dry heat shrinkage rate of less than 10%.

After the sheet obtained as described above is dried, excellent physical properties can be imparted by heating it under pressure using a hot press or a hot roll.

The temperature of the hot press or hot roll varies somewhat depending on the crystallinity of the pulp particles and short fibers, degree of polymerization, etc., but is 140 ° C.
320°C is suitable. The sheet according to the present invention has excellent mechanical properties such as tensile strength and elongation, and as a result has excellent heat resistance and
Taking advantage of its flame retardant and electrically insulating properties, it is not only effectively used as electrically insulating materials and electrically insulating paper, but also as wall covering materials and structural materials.

A method for measuring the main characteristic values in the present invention will be explained.

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

Example 1 (Manufacture of pulp particles) 940 parts of N-methyl-2-pyrrolidone was prepared by cooling 60 parts of polymetaphenylene isophthalamide powder with a logarithmic viscosity of 1.8 obtained by an interfacial polycondensation method to 5°C. After dispersing the polymer in the polymer, 111 parts of mica powder having a particle diameter of 400 to 1,000 mesh as measured by the acidorean pipette method was mixed therein, and then heated to about 40 DEG C. to completely dissolve the polymer.

On the other hand, the concentration of N-methyl-2-pyrrolidone, which is a mixture of N-methyl-2-pyrrolidone and water as a precipitant, is 20.3
Three types of precipitants were prepared at 0.40% by weight. Diameter 40 as a precipitant device? ! A pipe agitation type continuous precipitator was used, which consisted of a combination of &WL's cylindrical stator and a turbine blade type two-blade rotor, and was equipped with a precipitant, a solution supply port, and a discharge port for the pulp particle slurry after precipitation. , the polymer solution was simultaneously supplied at a flow rate of 0.8 kg/-8 kg of precipitant/77 Zm, and the pulp particle slurry was taken out from the outlet.

At this time, the temperature of both the precipitant and the solution was adjusted to 30°C. Also, the rotation speed of the rotor is 9000r. p. It was set as m. The obtained pulp particle slurry is placed in a centrifuge, and after removing most of the precipitant as a slurry, ion-exchanged water is supplied,
Washed thoroughly. Pulp particles were thus obtained, consisting of about 65% by weight of mica particles and about 35% by weight of polymethaphenylene isophthalamide, in which the mica particles were coated and interconnected with polymethaphenylene isophthalamide.
(Production of short fibers) 20.5 parts of the same polymetaphenylene isophthalamide powder used in producing pulp particles was mixed with N-methyl-
A spinning stock solution prepared by dissolving 79.5 parts of 2-pyrrolidone was extruded into a coagulation bath containing 235% by weight of Cacl and 28% by weight of Zncl and adjusted to 60°C.

The fibers obtained by extruding into a coagulation bath were washed with water, stretched 2.7 times in boiling water (first stage stretching), and then dried and stretched 1.3 times on a hot plate at 330°C. While heat treatment (
2nd stage stretching heat treatment) and then rolled up.

The dry heat shrinkage rate of this fiber at 300°C was 4.5%. (Fiber B) Meanwhile, in the same manner as above, 2
．． After stretching to 7 times, roll it with a drying roller and then roll it up for 30 minutes.
A fiber with a dry heat shrinkage rate of 73% at 0°C was obtained (fiber A
) (Production of Sheet) Pulp particles 2.169 (solid matter) obtained previously and the polymethaphenylene isophthalamide fiber 0.459 (in the sheet) having a single fiber fineness of 1.8 denier cut into a length of 51 m Contains 20% total short fiber distribution.

Paper was made from the aqueous dispersion using a Tatsupi standard sheet machine, dried and then pressed at 300° C. and 200 kg/Cd to obtain a sheet with a thickness of about 120 μm. At this time,
Tests were carried out by varying the proportions of short fibers A1 and short fibers B in the total short fibers (0.54 f1) in the sheet, and the results shown in Table 1 below were obtained. In Table 1, f;. Nos. 3 and 4 were sheets of the present invention, which had good tensile strength and elongation and dielectric breakdown voltage.

When the sheets of Matani 3 and 4 were left in air at 40° C. for 7 days, the above-mentioned performance hardly changed, the degree of coloring was very small, and the heat resistance was good. On the other hand, ▲1, 2, and 5 are comparative examples, and 1 and 2 are cases in which the proportion of fiber A in the total short fibers is too high, and the elongation is low.

Also, ▲5 is a case where all the short fibers are composed of only fiber B, and the tensile strength is inferior to the sheet of the present invention. Example 2 Preparation of Polymer Solution Trimellitic anhydride and 4-4! in N-methyl-2-pyrrolidone. After reacting and dehydrating diaminodiphenylmethane at a molar ratio of 2:1, trimellitic anhydride and 4-
4'-diphenylmethane diisocyanate was added and reacted in a molar ratio of 2:3 to form a polyamide (logarithmic viscosity 0.81
) was obtained.

(Solution A) Separately, 115 parts of ion-exchanged water was added to 1423 parts of N-methyl-2-pyrrolidone, and then 232 parts of mica powder with a particle size equivalent to 400 to 1000 mesh measured by the Andreasen pipette method was added, and then T - Stirred for 40 minutes using a K homomixer (manufactured by Tokushu Kika Kogyo).

(Mixed solution B) Next, 500 parts of solution A was added to 770 parts of mixed solution B1, stirred until uniform, and polyamide-imide, N
-Methyl-2-pyrrolidone A solution consisting of water and mica was obtained.

(Solution C) Preparation of precipitant N-methyl-2-pyrrolidone and water are mixed to give an N-methyl-2-pyrrolidone concentration of 70% by weight? A precipitant was made.

Production of Pulp Particles The solution is transferred to a conduit stirring type continuous precipitator, which consists of a combination of a stator with a baffle and a turbine blade rotor, and is equipped with a precipitant, a solution supply port, and a discharge port for the pulp particle slurry after precipitation. C.O. 8kg/WL, precipitant 8
kg/day and the pulp particle slurry was taken out from the outlet.

At this time, the temperature of the precipitant was adjusted to 34°C and the temperature of solution C was adjusted to 30°C. Further, the rotation speed of the rotor was set to 7100 rpm. The obtained pulp particle slurry is put into a centrifuge.
+Cll”;1101:FO/. IVIV/? /U ゝ/u ▲6, 7, 8, 9 are the sheets of the present invention, ▲10 to 1
4 is a comparative example.

Although the level of strength and elongation varies depending on the total amount of short fibers in the sheet, it is clear that the strength and elongation of the sheet of the present invention is superior when comparing sheets with the same total amount of short fibers. .

▲10, 11, and 13 are cases where the proportion of short fibers A in all short fibers is too high, and the elongation of the sheet is poor in all cases.

▲12 is the case of short fiber B only, with strong elongation☆I11$J, Kudan F5-1q Hapar ``Soil Pshi IJwo 1194ιFhi9
I, November? VAIυ,v'v A sheet was obtained in the same manner as in Example 2 from an aqueous dispersion of short fibers obtained by cutting the above four types of fibers into lengths of 7 mm and the same pulp particles as used in Example 2.

*Most of the precipitant was taken out as a filtrate. Next, ion-exchanged water was supplied to perform thorough washing. Papermaking From an aqueous dispersion containing the pulp particles thus obtained and the same short fibers A) and short fibers B as used in Example 1 in various proportions, paper was made using a Tatsupi standard sheet machine, and after drying, A sheet with a thickness of about 110 μm was obtained by hot pressing.

NaK r+Cll”;1101:FO/. IVIV/? ``Re'' /U ゝ/u ☆Both degrees are inferior.

In addition, ▲14 was a case where the total amount of short fibers was too large, the strength and elongation were low, and the dielectric breakdown voltage was also unsatisfactory. Example 3 In the production of short fibers in Example 1, the short fibers were stretched 2.7 times in boiling water, then dried with a drying roller, and then heat treated while being stretched 1.3 times while varying the temperature of the plate. 300
The following four types of fibers having different dry heat shrinkage rates at °C were obtained.

A sheet was obtained in the same manner as in Example 2 from an aqueous dispersion of short fibers obtained by cutting the above four types of fibers into lengths of 7 mm and the same valve particles as used in Example 2.

At this time, the total amount of short fibers in the sheet was set at 30%, and the composition of the total short fibers was varied.

The results are shown in Table 3. Sheets 15, 16, and 17 are sheets of the present invention and are shown as comparative examples.

r;. Compared to No. 18, the tensile strength and elongation are superior.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the range of the preferred total amount of short fibers in the sheet and the preferred amount of short fibers having a dry heat shrinkage rate of 10% or more at 300'C relative to the total short fibers.

Claims (1)

[Claims] 1. A sheet formed by mixing mica particles, pulp particles consisting of a heat-resistant and solvent-soluble aromatic polymer, and aromatic polyamide short fibers, making paper, and heating under pressure. A mixture of short fibers having a dry heat shrinkage rate of 10% or more at 300°C and short fibers having a dry heat shrinkage rate of less than 10% at 300°C is used as the fiber, and the dry heat shrinkage rate at 300°C is 10%. % or more of the short fibers in the sheet relative to the total short fiber mixture in the sheet (however, the coordinates of points P, Q, R, S, T, and V are P (5%, 5%), (20%, 5%), R (70%,
15%), S (70%, 90%), T (50%, 90%
), V (5%, 15%).