JP2641314B2 - Electrical insulating paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric insulating paper having excellent surface smoothness and heat resistance used for insulating a transformer or a high-voltage cable.

<Prior art> Conventionally, in fields where heat resistance, electrical insulation, and flexibility (easiness of winding around coils, cables, etc.) are required, such as insulating paper for transformers or high-voltage cables, various films and Various types of synthetic papers are used, and electric insulating papers are often used particularly from the viewpoint of flexibility. Above all,
Synthetic paper made of 100% aromatic polyamide by DuPont (Nom
ex410) is most often used. This Nomex410
JP-B-35-11851, JP-B-36-16460 and JP-B-37-5732 mix an aromatic polyamide fibrid and an aromatic polyamide staple fiber, and then perform hot-press calendering. It has excellent heat resistance, electrical insulation and flexibility.

However, this Nomex410 contains relatively crystalline oriented aromatic polyamide staple fibers, and these staple fibers are easily exposed as fuzz on the synthetic paper surface, and are therefore used for transformers and high-voltage cables. In this case, electric field concentration is caused at the fluff portion, and discharge occurs.

In order to improve this, a technique has been proposed in which an aromatic polyamide fibrid and an aromatic polyamide short fiber having low crystal orientation are mixed, and then subjected to hot-press calendering so as to exhibit surface smoothness. No. 01-55015).

On the other hand, as a measure for reducing the fluff generated after the friction, a technique of mixing polytamphenphenylene isophthalamide pulp with polyparaphenylene terephthalamide pulp has been proposed (Japanese Patent Application No. 02-12892).

This invention reduces the number of fluffs generated after friction on the synthetic paper surface by 10
~ 30 / 25cm ²
Since fuzz occurs at about / 25 cm ^2, there is a risk of dielectric breakdown due to local discharge.

<Object of the Invention> An object of the present invention is to solve the problem of generation of fluff of the heat-resistant electrical insulating paper as described above.

That is, an object of the present invention is to provide an electric insulating paper which is excellent in heat resistance and electric insulating properties and has extremely little fluff even when the surface is rubbed.

<Constitution of the Invention> That is, the present invention relates to "a synthetic paper composed of 100% by weight of polymetaphenylene isophthalamide pulp and having a basis weight of 10 g / m ² or more, and 10 to 80 parts of polymetaphenylene isophthalamide pulp.
Wt% and polymetaphenylene isophthalamide staple fiber
Laminated with synthetic paper consisting of 90 to 20% by weight, hot-pressed at 180 ° C or higher, the number of fluffs generated after surface friction by JIS-L-0823 method is 10 / 25cm ² or less Electrical insulating paper ".

Polymetaphenylene isophthalamide pulp is known, for example, described in JP-B-35-11851 and JP-B-37-5732, and the form of polymetaphenylene isophthalamide staple is a single fiber fineness. Those having a denier of 20 or less and a fiber length of 20 mm or less are preferred.

Synthetic paper containing 100% by weight of polymetaphenylene isophthalamide pulp has a basis weight of 10 g / m ² or more. If it is less than 10g / m ^2,
After surface friction, the polymetaphenylene isophthalamide pulp is peeled off, and the underlying polymetaphenylene isophthalamide staple fibers cause fluff.

The lower layer of synthetic paper composed of polymetaphenylene isophthalamide pulp and polymetaphenylene isophthalamide short fiber has a polymetaphenylene isophthalamide pulp content of 10 to 80% by weight. If the mixing ratio of polymetaphenylene isophthalamide pulp is less than 10% by weight,
If the strength of the lower layer side synthetic paper is remarkably reduced and lamination is impossible, if the content is more than 80% by weight, the tear strength is reduced, the dimensional stability is poor and the practicality is lost.

The laminating method may be mixed papermaking, calendar lamination, or flat plate press laminating. In the case of mixed papermaking, thereafter, hot pressing is performed at a temperature of 180 ° C. or more. Also, in the case of calender lamination, hot pressing at 180 ° C. or more is required as lamination conditions. The hot-pressing method may be processing by a calender roll or flat plate pressing.

If the processing temperature is lower than 180 ° C., the adhesion between the upper layer of polymetaphenylene isophthalamide pulp 100% by weight and the lower layer made of polymetaphenylene isophthalamide pulp and polymetaphenylene isophthalamide short fiber becomes insufficient, and after the paper surface friction, Fluff frequently.

The method of rubbing the paper surface and the number of fluffs generated after rubbing are determined by the following methods.

(Method of abrading the paper surface and measuring the number of fluff after the abrasion) In accordance with JIS L-0823, using a friction tester type II [manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.], using a gold cloth No. 3 cloth, 500 g for the friction body
Under a load of 60 reciprocations per minute at a reciprocating speed of 100% by weight of polymetaphenyleneisophthalamide pulp
Rub 00 times.

The number of fluffs generated on the paper surface after friction was visually measured in an area of 25 cm ² . The same measurement was performed for five samples, and the average value was shown.

<Effect of the Invention> The electrical insulating paper of the present invention has excellent heat resistance and electrical insulating properties.
Further, the generation of fluff after surface friction is extremely small.

 Therefore, there is little danger of electric field concentration, local discharge, and the like.

It is suitable for applications requiring heat resistance, electrical insulation, and surface smoothness, such as insulating paper for transformers or high-voltage cables.

<Example> Next, the present invention will be described in more detail with reference to examples.
In the examples, measured values other than the number of fluff after friction were evaluated by the following methods.

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

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

(3) Dielectric breakdown strength: Measured according to JIS-C-2111.

(4) Heat absorption rate: A sample of 1 cm in width and 10 cm in width was dried using a dryer (PHH-100 type) manufactured by Tabai Espec Co., Ltd. for 250
The heat shrinkage of the vertical and horizontal axes after the treatment at 10 ° C. for 10 minutes was calculated by the following equation. The average value of the vertical and horizontal values is shown.

Heat shrinkage _{(%) = {(l 0} -l 1) / l 0} × 100 ( Note) l _0: before shrinkage sample length l _1: sample length after shrinkage (5) Tear strength: JIS-P It was measured according to −8113, and the average value of the length and width was shown.

Examples 1 to 5 and Comparative Examples 1 to 5 A polymetaphenylene isophthalamide pulp slurry for blending was produced by the following method.

First, polymetaphenylene isophthalamide was produced by the interfacial polymerization method described in JP-B-47-10863.
This polymer has an intrinsic viscosity (IV) of 1.35 as measured by dissolving in N-methyl-2-pyrrolidone, and contains no inorganic salt in the polymer. Was dissolved in N-methyl-2-pyrrolidone to give 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, an aqueous slurry having a slurry concentration of 0.3% and a Canadian standard freeness of 110 ml was prepared using a pulper, a high-speed dissociator and a disc refiner.

The polymetaphenylene isophthalamide short fiber for blending was produced by the following method.

A polymetaphenylene isophthalamide polymer having an intrinsic viscosity [η] of 1.45 prepared by the interfacial polymerization method described in JP-A-47-10863 was dissolved in a solvent comprising N-methyl-2-pyrrolidone at a concentration of 20.5% by weight. To prepare a spinning dope, and using this spinning dope, according to the wet spinning method described in JP-B-47-17551, a spinning hole having a hole diameter of 0.07 mm is used.
Calcium chloride concentration 45%, temperature 9 from 0 spinnerets
Spinning was performed in a coagulation bath consisting of an aqueous solution of calcium chloride at 0 ° C.

The coagulated undrawn fiber is pulled out of the coagulation bath
It contained 45% by weight of solvent.

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

Next, the pulp slurry and the short fibers were mixed at a mixing ratio as shown in Table 1 to form an upper layer sheet and a lower layer sheet using a round net 2-bat paper machine.

Then, under the conditions of temperature and pressure of 200 kg / cm as shown in Table 1,
Calendered.

 The properties obtained are shown in Table 1.

As shown in Table 1, Example 1 was extremely excellent in performance without generation of fuzz after friction.

In addition, Examples 2 to 5 were also good as shown in Table 1.

In Comparative Example 1, the short fibers were mixed in the upper layer.
As shown in the table, fluff after rubbing occurred frequently and was poor.

In Comparative Example 2, since the basis weight of the upper layer was low, the pulp portion of the upper layer was peeled off after rubbing, and the mixed short fibers of the lower layer became fuzzy and frequently occurred.

In Comparative Example 3, since the lower layer had a low pulp mixing ratio, lamination was impossible due to insufficient strength of the lower layer sheet.

In Comparative Example 4, since the lower layer had a high pulp content, the tear strength was low and the dimensional stability was poor.

In Comparative Example 5, since the calender temperature was low, the adhesion between the upper layer and the lower layer was insufficient, the pulp portion of the upper layer was peeled off after rubbing, and the mixed short fibers of the lower layer became fluffy, resulting in multiple defects.

Claims (1)

(57) [Claims] 1. A synthetic paper comprising 100% by weight of polymetaphenylene isophthalamide pulp having a basis weight of 10 g / m ² or more, 10 to 80% by weight of polymetaphenylene isophthalamide pulp, and 90 to 20% by weight of polymetaphenylene isophthalamide short fiber. % Synthetic resin paper, and hot-pressed at 180 ° C. or more, and the number of fluffs generated after surface friction is 10/25 cm ² or less.