JP2535418B2 - Heat-resistant paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is excellent in electrical insulation, dimensional stability and flexibility used for adhesive tape substrates, insulating materials for transformers or high voltage cables, etc. Regarding heat-resistant paper.

<Prior Art> As a F-type heat-resistant paper conventionally used as a base material for adhesive tapes, insulating materials for transformers or high-voltage cables, etc., synthetic paper made of 100% wholly aromatic polyamide (hereinafter referred to as all-aramid paper. For example, Nomex 410 ) Is most often used. As described in JP-B-35-11851, JP-B-36-16460 and JP-B-37-5732, after mixing the aromatic polyamide fibrid and the aromatic polyamide short fibers, a hot press calendering process is carried out. It is a class H heat-resistant paper formed by pressing.

However, this all-aramid paper lacks flexibility (winding property) when wound around a coil or a cable.

Further, as a publicly known technology concerning heat-resistant paper of class E or more as an electric insulating material, a printed circuit laminate is disclosed in Japanese Patent Publication No. 52-
27189, Japanese Patent Publication Sho 56
-1792 and Japanese Patent Application Laid-Open No. 60-126400 are known as heat-resistant papers, both of which are a mixture of aromatic polyamide fibers and polyester fibers. However, since all of them are a mixture of only fibers, there is a drawback that a satisfactory electric breakdown voltage cannot be obtained.

As a synthetic paper, a mixture of aromatic polyamide fibrid with polyester short fibers is also known (JP-A-47).
-23602 publication).

However, this synthetic paper has a high dry heat shrinkage and lacks dimensional stability.

<Object of the Invention> An object of the present invention is to improve the flexibility, electrical insulation, and dimensional stability of the mixed paper having heat resistance of class E or more as described above.

That is, it is to provide a Class F heat-resistant paper having excellent electrical breakdown strength, flexibility, and good thermal dimensional stability.

<Structure of the Invention> That is, the present invention relates to a synthetic paper comprising aromatic polyamide pulp particles, aromatic polyamide short fibers, and polyester short fibers, the aromatic polyamide pulp particles 30 ~
80% by weight, 10-60% by weight of aromatic polyamide short fibers, 10-60% by weight of polyester short fibers, the electrical breakdown strength is 18 KV / mm or more, and the dry heat shrinkage ratio at 200 ℃ is 2.0. It is a heat-resistant paper whose content is less than or equal to%.

The aromatic polyamide used in the present invention is a conventionally known (a) condensation polyamide of a dicarboxylic acid having an aromatic ring and a diamine having an aromatic ring (b) a condensation obtained by condensing an aminocarboxylic acid having an aromatic ring Polyamide (c) Examples include polyamides obtained by copolymerizing the above (a) and (b).

Aromatic polyamide pulp is known, for example, in Japanese Examined Patent Publication No. 35-11.
It is described in Japanese Patent No. 851 and Japanese Patent Publication No. 37-5732. Especially poly (m-phenylene isophthalamide)
Is preferred.

The aromatic polyamide short fibers are also preferably poly (m-phenylene isophthalamide). As the form of the short fibers, those having a single yarn fineness of 20 denier or less and a fiber length of 3 to 20 mm are preferable.

The polyester fiber is a polyester containing a known dicarboxylic acid as a dibasic acid component and an aliphatic alicyclic or aromatic glycol or a polyoxyalkylene glycol such as polyethylene glycol as a glycol component. Copolyesters obtained by combining one or more of these dibasic acid components or glycol components may be used. A particularly preferable example is polyethylene terephthalate. Ordinary fiber additives may be used. Further, a polyester fiber containing a low melting point component may be used.

The polyester fiber of the present invention is preferably a short fiber having a single yarn fineness of 20 denier or less and a fiber length in the range of 3 to 20 mm as the fiber form, but it may be composed of only drawn yarn and may be composed of both drawn yarn and undrawn yarn. It may be configured. Further, in order to obtain good electric insulation properties, it is preferable to be composed only of undrawn yarn.

When the aromatic polyamide pulp particles are less than 30% by weight, the dielectric breakdown strength is low, and when it exceeds 80% by weight, the dry heat shrinkage ratio is high. 10% by weight of aromatic polyamide short fibers
If less than 60% by weight, the dry heat shrinkage will be high
If it exceeds, the dielectric breakdown strength becomes low. Furthermore, when the polyester short fiber content is less than 10% by weight, it lacks flexibility,
If it exceeds 5% by weight, heat resistance becomes poor.

The electric breakdown strength was measured according to JIS-C-2111.

The dry heat shrinkage ratio at 200 ° C. was measured by the following method. First, a square sheet of 10 cm in height and 10 cm in width is sampled and put in a hot air dryer at 200 ° C ± 2 ° C (Tabai's New Perfect Oven PHH-200 type) without tension.
After 30 minutes, put the sample area to S ₁ (cm ² ). This test is repeated 5 times, the dry heat shrinkage ratio (area shrinkage ratio) is calculated by the following formula, and the average value is shown.

Dry heat shrinkage (%) = {(10 ² −S ₁ ) / 10 ² } × 100 The heat-resistant paper of the present invention is preferably subjected to hot-press calendering after paper-making drying. It is preferable that the temperature is 100 kg / cm or more and the temperature is 130 ° C. or more.

The heat-resistant paper of the present invention can be used as a base material for pressure-sensitive adhesive tapes and electric insulation applications that require F-type heat resistance. Furthermore, by laminating and heat-pressing this heat-resistant paper, it can be used as a F-type heat-resistant board Can be used.

<Effect of the Invention> The heat-resistant paper of the present invention is a Class F heat-resistant paper excellent in electrical insulation, thermal dimensional stability and flexibility.

It is suitable for use in fields requiring heat resistance, electrical insulation, thermal dimensional stability, and flexibility, such as adhesive tape substrates, transformers, and high voltage cable insulation.

<Example> Next, the present invention will be described in more detail with reference to examples.
In the examples, measured values other than the electric breakdown strength and dry heat shrinkage were evaluated by the following methods.

(1) Weighing: Measured according to JIS-P-8124.

(2) Thickness: Measured according to JIS-C-2111.

(3) Flexural rigidity: A pure bending tester KES-FB2 (manufactured by Kato Tech Co., Ltd.) was used to hold a square sample measuring 2.5 cm in length and 2.5 cm in width on a chuck at 1 cm intervals to perform pure bending with constant velocity curvature. The test was carried out in the range of 0 to 120 degrees, and the bending rigidity per unit length (g · cm ² / cm) was evaluated.

(4) Long-term heat resistance: According to the heat resistance test method in IEC Publication 216, it was displayed in the material heat resistance category of IEC publication 85.

Examples 1 to 4 and Comparative Examples 1 to 6 Polymetaphenylene isophthalamide polymers having an intrinsic viscosity [η] of 1.45 produced by the interfacial polymerization method described in JP-A-47-10863 are N-methyl-2. -Preparation of a spinning dope by dissolving in a solvent consisting of pyrrolidone at a concentration of 20.5% by weight, according to the wet spinning method described in JP-B-48-17551, using this spinning dope, a spinning hole having a pore diameter of 0.07 mm is 1000
Calcium chloride concentration 45%, temperature 9 from 0 spinnerets
Spinning was carried out in a coagulation bath consisting of an aqueous calcium chloride solution at 0 ° C.

The coagulated unstretched fibers are removed from the coagulation bath when they are drawn out.
It contained 45% by weight of solvent.

The undrawn fiber is washed with a 60 ° C warm water bath to reduce the solvent content to 8% by weight, then drawn 2.4 times in a 94 ° C warm water bath, dried at 130 ° C, and heated at 350 ° C. The above was stretched 1.75 times to obtain a papermaking fiber. Further, this was cut into a length of 6 mm to obtain polymetaphenylene isophthalamide short fibers for papermaking having a single yarn fineness of 2 denier and a fiber length of 2 mm.

On the other hand, as the polyester short fibers, undrawn polyethylene terephthalate single fibers having a single yarn fineness of 1.1 denier and a fiber length of 5 mm were used, and they were mixed and disaggregated with a pulper at a concentration of 1% together with the polymetaphenylene isophthalamide short fibers.

 The mixed pulp was manufactured by the following method.

First, polymetaphenylene isophthalamide was produced by the interfacial polymerization method described in JP-B-47-10863.
This polymer had an intrinsic viscosity (IV) of 1.35 measured by dissolving it in N-methyl-2-pyrrolidone, and the polymer contained no inorganic salt at all. This polymer is N-methyl-2-
It was dissolved in pyrrolidone to a polymer concentration of 12.5% by weight. On the other hand, water was added to N-methyl-2-pyrrolidone to prepare an aqueous solution (concentration: 30% by weight), which was used as a precipitant.

The polymer solution and the precipitant were charged into a chamber having a polymer solution inlet, a precipitant inlet, and a slurry outlet, a rotor mounted in the chamber, and an inner wall of the chamber, as described in JP-A-52-15621. The mixture was injected from each injection port using a sedimentation device comprising a stator fixed to the above, and the rotor was rotated at high speed to pulp.

Using the obtained pulp, a pulper, a high-speed disintegrator and a disc refiner were used to prepare an aqueous slurry having a slurry concentration of 0.3% and a Canadian standard freeness of 110 ml.

Then, the short fiber mixed slurry and the pulp slurry were mixed at a mixing ratio as shown in Table 1, and hand-made by a square type sheet machine having a length of 25 cm and a width of 25 cm. Then the temperature 230
It was calendered under the conditions of ℃ and pressure of 200Kg / cm.

 The properties obtained are shown in Table 1.

As shown in Table 1, Example 1 has electrical insulation, heat resistance,
The dimensional stability and flexibility were extremely good.

In addition, Examples 2 to 4 were also good as shown in Table 1.

In Comparative Example 1, the electrical insulation breakdown strength was inferior to that in Examples 2 and 4 because the pulp mixing ratio was low.

In Comparative Example 2, the dry heat shrinkage ratio was higher than that in Example 3 because the pulp mixing ratio was high, and the dimensional stability was poor.

In Comparative Example 3, since the mixing ratio of the aromatic polyamide short fibers was low, the dry heat shrinkage ratio was higher than in Examples 3 and 4, and the dimensional stability was poor.

In Comparative Example 4, since the mixing ratio of the aromatic polyamide short fibers was high, the electric breakdown strength was inferior to that in Example 2 and the flexibility was also lacking.

In Comparative Example 5, the mixing ratio of the polyester unstretched short fibers was low, so that the bending rigidity was higher than in Examples 2 and 3, and the flexibility was lacking.

In Comparative Example 6, the long-term heat resistance was inferior to that in Example 4 because the mixing ratio of the polyester unstretch reduction ratio was high.

Claims (1)

(57) [Claims] 1. A synthetic paper comprising aromatic polyamide pulp particles, aromatic polyamide short fibers and polyester short fibers, wherein the polyester short fibers are selected from the group consisting of polyester drawn yarn, undrawn yarn or low melting point polyester drawn yarn. 1 or more polyester short fibers, which are mixed in the range of 30 to 80% by weight of aromatic polyamide pulp particles, 10 to 60% by weight of the aromatic polyamide short fibers, and 10 to 60% by weight of the polyester short fibers, Electrical breakdown strength is 18KV / mm
As described above, the Class F heat-resistant paper is characterized in that the dry heat shrinkage at 200 ° C. is 2.0% or less.