JPH1166964A - Fire resistant insulating tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tape excellent in strength, insulating performance, heat resistance, surface smoothness, airtightness and handling performance by constituting a fire resistant insulating tape for a fire resistant insulating layer of a fire resistant conductor where a fire resistant insulating layer, an insulating layer and an outside covering layer are arranged in order on the outside of a conductor, out of fiber having a flat cross section, mica and a binder, and specifying its composition rate. SOLUTION: A heat resistant insulating tape is composed of fiber A having a flat cross section, mica B and a binder C, and in its rate, when the total of A and B is denoted by 100 pts.wt., A is 10 to 60 pts.wt., and B is 40 to 90 pts.wt., and C is 3 to 20 pts.wt. to the total 100 pts.wt. of A and B. Inorganic flat fiber is mixedly combed with the mica as a basic skeleton, and is turned into a sheet by an inorganic binder, and when a fire resistant insulating layer and a reinforcing layer are collectively molded, since a mica scale and skeleton fiber are oriented in a surface shape to a high degree by a singular cross-sectional shape of the flat fiber, a sheet having high strength and high density while being a thin type, can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire-resistant insulating tape.

[0002]

2. Description of the Related Art According to standards (notified by the Fire and Disaster Management Agency), fire-resistant electric wires are heated to 840 ° C. in 30 minutes, and maintain a withstand voltage characteristic of 600 V AC and an insulation resistance of 0.4 MΩ or more during that time. In order to pass this standard, even if the plastic layer (insulating layer) such as polyvinyl chloride, which normally covers the outside of the wire, is thermally decomposed at high temperature and its conductive decomposed matter is generated, the above electrical characteristics of the wire A refractory insulating layer must be provided so that

Hitherto, as a structure of a fire-resistant electric wire, a structure in which a fire-resistant insulating layer and an outer coating are sequentially provided outside a conductor, or a structure in which a fire-resistant insulating layer, an insulating layer, and an outer coating are sequentially provided, and the like have been adopted. Usually, an inorganic material such as mica or ceramic is used as a component to be a fire-resistant insulating layer. Since these inorganic materials have a melting temperature of about 1200 ° C. or higher, it is possible to maintain insulation by contact to the end under fire.

[0004] In particular, mica is a layered inorganic compound, and thus a sheet produced using the same has a high degree of airtightness because mica particles are plane-oriented. When mica is used as a fire-resistant layer, it remains even if the insulation layer and sheath layer (external coating) are melted and burned down in a fire, blocking the approach and contact of conductive gas such as HCl gas to the conductor surface. To maintain insulation and maintain the power transmission capability of the conductor.

However, since mica is a layered inorganic compound, it is brittle once formed, and it is difficult to form a solid sheet-like refractory insulating layer. Further, mica itself does not have the strength required in the process. So far, various ideas have been devised. Many of them are obtained by laminating laminated mica and a sheet as a reinforcing material to form a composite tape. Many attempts have been made to use a glass fiber woven fabric or a glass fiber nonwoven fabric as a reinforcing layer.

For example, in Japanese Patent Application Laid-Open No. 58-82413, a thread of a thermoplastic resin is adhered at regular intervals on a plurality of glass fibers arranged in parallel, and its contacts are bonded at regular intervals. A mica foil tape is attached via a system adhesive, and the conductor is further covered with a polyethylene tape or a polyester nonwoven fabric to form a fire-resistant insulating layer.

In Japanese Utility Model Application Laid-Open No. 57-147512, a plurality of glass threads in which a refractory insulating layer is aligned in the longitudinal direction are joined and supported on a support tape (reinforcing layer) made of plastic fiber, and mica is provided on the support. A fireproof electric wire characterized by being formed by winding an attached mica composite tape is described.

Further, Japanese Utility Model Application Laid-Open No. 58-88717 and Japanese Utility Model Application Laid-open No. 63-13615 show a composite tape obtained by laminating a fire-resistant insulating layer formed of laminated mica and a glass fiber non-woven fabric provided integrally therewith as a reinforcing layer. And a fire-resistant electric wire on which an insulating layer and a coating layer are formed.

The common feature of these conventional techniques is that mica is bonded to another sheet and reinforced to form a composite tape. However, in order to take such a structure, prepare a refractory insulating layer and a reinforcing layer respectively,
It is necessary to make a composite tape in advance by laminating these, which has the disadvantage of increasing the number of steps. At the same time, the structure of the composite tape becomes complicated and its thickness becomes relatively large.

[0010] The thickness of the composite tape has a great influence on the workability in the production of fire-resistant electric wires. When the composite tape is thicker, it becomes more rigid, so the slight gap in the overlapping part that occurs when the tape is wound around the conductor reduces airtightness, reduces fire-resistant insulation, and may result in conductivity during a fire. Come.

However, if the composite tape is made thinner and supple to solve this problem, it is necessary to reduce the thickness of the mica layer or the reinforcing layer, so that the airtightness or strength of the composite tape may be impaired. Sex comes out. As a result, the composite tape has reduced insulating properties in the event of a fire, or cannot cope with high-speed winding around a conductor.

More fundamentally, the woven or nonwoven fabric used for the reinforcing layer of the insulating layer has a considerably lower density, a higher porosity, and a rougher surface than a dense fire-resistant insulating layer composed of mica. Therefore, if such a reinforcing layer and a fire-resistant insulating layer are bonded to form a composite tape, the fire-resistant insulating layer cannot continuously cover the surface in a tape overlapping portion generated at the time of winding around a conductor. That is, the reinforcing layer is sandwiched between the refractory insulating layers in the tape overlapping portion, resulting in impaired airtightness.

[0013] The same applies to the case where the reinforcing layer is present between the first layer and the second layer when the composite tape is wound twice around the conductor. That is, the first reinforcing layer is present between the first fire-resistant insulating layer and the second fire-resistant insulating layer, and the fire-resistant insulating layer is not continuous in the thickness direction. The conductive gas that has broken through the refractory insulating layer of the layer easily diffuses through the first reinforced layer having a high porosity,
It can reach the tape overlapping portion of the second layer of the refractory insulating layer. As a result, even if the composite tape is double-wound, the insulating effect on the conductive gas is still incomplete.

[0014]

Therefore, the following items can be considered as conditions required for this fire-resistant insulating tape.・ Sufficient strength ・ Excellent insulation ・ Excellent heat resistance ・ Flexible and excellent surface smoothness ・ Thin and highly airtight ・ Simple handling and few steps An object of the present invention is to solve the above problems.

[0015]

That is, the present invention relates to a fire-resistant insulating tape for a fire-resistant insulating layer of a fire-resistant wire, in which a fire-resistant insulating layer, an insulating layer, and an outer coating layer are sequentially provided outside a conductor,
The fire-resistant insulating tape is composed of a fiber (A) having a flat cross section, a mica (B), and a binder (C), and the proportion thereof is as follows, when the total of (A) and (B) is 100 parts by weight.
(A) is 10 to 60 parts by weight, (B) is 40 to 90 parts by weight,
Also, for a total of 100 parts by weight of (A) and (B),
(C) is a fire-resistant insulating tape characterized in that it is 3 to 20 parts by weight. Further, the present invention relates to the fire-resistant insulating tape according to the above invention, wherein the fiber having a flat cross section is an inorganic fiber having a fiber cross section having a ratio of major axis / minor axis of 2 or more. In the present specification, the “fiber having a flat cross section” is hereinafter referred to as “flat fiber”. In the present specification, the composite tape refers to a conventional type of fire-resistant insulator in which a mica layer, which is a fire-resistant insulating layer, and a reinforcing layer are bonded, and a fire-resistant insulating tape is a fire-resistant insulating layer, which is a fire-resistant insulating layer. This refers to a new type of refractory insulator in which the mica layer and the flat fiber as the reinforcing layer are integrally formed by blending.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied the use of inorganic flat fibers as a basic skeleton as a basic skeleton, mixed with mica, and made a sheet with an inorganic binder or the like to form a refractory insulating layer and a reinforcing layer at one time. Since the mica scales and skeletal fibers are highly plane-oriented due to the unique cross-sectional shape of the flat fibers, they are joined with a large contact area to form a thin, high-strength, high-density sheet. When used as a fire-resistant insulating tape, it is easy to handle because it is molded in a single piece, and the number of processes is small.The airtightness after winding the tape is very high because the front and back surfaces are covered with dense mica. The present invention has been found to be more pliable than a relatively rigid woven or nonwoven fabric, and to have sufficient insulation and excellent heat resistance.

The most important feature of the present invention is that the skeletal fiber mixed with mica has a flat cross section. That is,
The flat fibers do not disturb the plane orientation of the mica foil in the mica foil that settles horizontally during wet papermaking, but rather participate in that orientation and are plane-oriented in the same direction, forming a strong airtight and strong sheet. You can do it. On the other hand, when making a nonwoven fabric with ordinary circular cross-section fibers, mica and skeletal fibers are not plane-oriented.

The fire-resistant insulating tape according to the present invention has a thickness of 20 to 600 μm as a nonwoven fabric obtained by mixing flat fibers and mica.
It is preferred that When a non-woven fabric having a thickness exceeding 600 μm is formed, the thinness of the fire-resistant insulating tape is lost, resulting in lack of flexibility.
If it is less than μm, the strength corresponding to high-speed winding is lost.

In the present invention, the amount of flat fibers is 10 to 60 when the total of flat fibers and mica is 100 parts by weight.
Parts by weight. This is because at least 10 parts by weight is necessary to fulfill the function as a skeleton, and if it exceeds 60 parts by weight, the amount of mica will be relatively small, so that the airtightness will decrease. is there.

The cross-sectional shape of the flat fibers used in the present invention corresponds to the one having a large contact area when the fibers overlap. For example, a high flat fiber as disclosed in Japanese Patent Publication No. 4-13300 or a fiber having a cocoon-shaped cross section as disclosed in Japanese Patent Publication No. 4-32775 is suitable. In a nonwoven fabric made using flat fibers, the fibers are plane-oriented with the major axis being horizontal, and the fibers intersect at a high density to obtain a high-density sheet.

The major axis and the minor axis of the cross section of the flat fiber used in the present invention are not particularly limited, and any fibers having a major axis and a minor axis in the cross section may be used. Is preferably 2 or more.
When the aspect ratio is less than 2, the effect of thinning the flat fibers is not exhibited.

The thickness of the flat fibers is not particularly limited, but is preferably 1.8 to 30 μm in terms of a fiber having a circular cross section. When a thick fiber having a low flattening rate is used, the shape effect of the flattened fiber is not exhibited, so that the layer is not plane-oriented with mica and the sheet becomes rigid, which is not preferable. Also, if too thin fibers are used, the strength decreases, and it is not possible to cope with high-speed winding, which is not preferable.

The material of the flat fibers may be any non-flammable and heat-resistant inorganic material, and glass for electrical insulation is suitable. Other materials having electrical insulation, for example, ceramic, alumina, titanium oxide, silica, Mullite, magnesia,
Fiber such as zirconia can be used, and other materials can also be used.

In the present invention, the amount of mica is 40 to 90 parts by weight when the total of the flat fibers and the mica is 100 parts by weight. If the mica content is less than 40 parts by weight, the amount of flat fibers relatively increases, and the airtightness that can be expected by mixing mica is impaired. This is because the sheet itself becomes fragile and the sheet itself becomes brittle.

The mica used in the present invention is an inorganic layered compound, and corresponds to natural mica or synthetic mica scales. As natural mica, muscovite, soda mica,
Examples include phlogopite, biotite, scale mica, and the like, and synthetic mica includes fluorphlogopite, tetrasilicic mica, teniolite, and the like, and other inorganic layered compounds can be used in some cases.

In the present invention, besides mica, flat fibers, and a binder used for forming a fire-resistant insulating tape, other materials can be mixed for a special effect. However, the composition ratio of the material should not be more than 20 parts by weight when the whole is 100 parts by weight. That is, if such an additive increases, the bonding due to the plane orientation of mica and flat fibers is inhibited, and the thinning, which is a feature of the present invention,
This is because high strength and confidentiality are lost.

In the present invention, the ratio of the binder to the flat fibers must not be too large. In terms of constitution, it is preferable to form a sheet with 3 to 20 parts by weight of an organic or inorganic binder based on 100 parts by weight of the total of the flat fibers and mica. This is because if the binder exceeds 20 parts by weight, the flexibility of the sheet is reduced, and the object of the present invention is not achieved. If the amount of the binder is less than 3 parts by weight, sufficient sheet strength cannot be obtained, so that it is impossible to cope with high-speed winding.

Organic and inorganic binders such as PVA, vinylon, heat-fusible olefin resin, silicone resin, low-melting glass, colloidal silica, and alumina emulsion are applicable as binder materials, but other binders are also used. It is possible. It is also possible to form a sheet by partially heat-sealing the fibers.

In order to produce the fire-resistant insulating tape of the present invention, a non-woven fabric sheet is prepared by wet-making a mixed slurry of flat fibers and mica, and a binder is added to the sheet. Methods for adding the binder include internal addition, impregnation, coating,
There are methods such as spraying. The nonwoven fabric sheet upon addition of the binder is preferably dry, but may contain moisture. Note that a method in which a binder is added to the slurry may be used.

[0030]

Next, the present invention will be described specifically with reference to the following examples.

Example 1 30 parts by weight of flat glass fiber chopped strand made of E glass (produced by Nitto Boseki Co., Ltd., flatness ratio 5.2, fiber diameter φ10 μm (in terms of circular cross section fiber, fiber length 13 mm)) and synthetic non-swelling phlogopite 70 parts by weight of mica scales (SiO ₂ 40-50%, MgO 25-
35%, Al ₂ O ₃ 6 to 15%, K ₂ O 5 to 10%, F 5 to 10%) by wet method to form a mixed sheet, and based on 100 parts by weight of the dry weight of the mixed sheet. Then, the wet paper was impregnated with 10 parts by weight of an organosilane resin adhesive as an inorganic binder.
It was dried and consolidated at 165 ° C to obtain a fire-resistant insulating tape. The fire-resistant insulating tape has a basis weight of 100 g / m ² and a thickness of 210 μm. This refractory insulating tape was wound in two layers at high speed at a tape winding speed of about 22 m / min in 1/2 lap with a copper conductor having an outer diameter of 2.0 mm.

Example 2 The flat glass fiber chopped strand 30 made of E glass was used instead of the flat fiber made of E glass of Example 1 as the flat fiber.
Parts by weight (Nittobo Co., Ltd., flatness ratio 2.5, fiber diameter φ10μm
A fire-resistant insulating tape was manufactured in the same manner as in Example 1 except that (a fiber having a circular cross section) and a fiber length of 13 mm were used. The fire-resistant insulating tape has a basis weight of 100 g / m ² and a thickness of 220 μm. This refractory insulating tape was wound in two layers at a high speed at a tape winding speed of about 22 m / min in 1/2 lap with a copper conductor having an outer diameter of 2.0 mm.

Comparative Example 1 For comparison, a glass fiber woven fabric having a thickness of 130 μm was prepared.
The same mica scales (molded as mica aggregates) having the thickness of 120 μm as in the example were bonded with an organosilane resin adhesive, and dried and bonded at 165 ° C. to form a composite tape.
The weight ratio of the glass fiber woven fabric, mica, and adhesive is shown in Table 1. This composite tape was wound in two layers at high speed at a tape winding speed of about 22 m / min in 1/2 lap with a copper conductor having an outer diameter of 2.0 mm in the same manner as in the example.

Comparative Example 2 For comparison, a glass fiber non-woven fabric having a thickness of 100 μm (using a glass fiber having a circular cross section) was prepared, and the same mica scale (as molded mica) having a thickness of 120 μm was used as an organometallic nonwoven fabric. The composite tape was adhered with a silane-based resin adhesive and dried and adhered at 165 ° C. The weight ratio of the glass fiber woven fabric, mica, and adhesive is shown in Table 1. This composite tape was wound in two layers at high speed at a tape winding speed of about 22 m / min in 1/2 lap with a copper conductor having an outer diameter of 2.0 mm in the same manner as in the example.

Comparative Example 3 E-glass circular cross section glass fiber chopped strand 30
Parts by weight (Fiber diameter φ9μm, fiber length 13 manufactured by Unitika Ltd.)
mm) and 70 parts by weight of the same mica flakes as in the example were wet-processed to form a mixed sheet, and the dry weight of the mixed sheet
100 parts by weight of the wet paper was impregnated with 10 parts by weight of an organosilane resin adhesive as an inorganic binder.
Drying and consolidation at ℃ to make a fire-resistant insulating tape. The fire-resistant insulating tape has a basis weight of 100 g / m ² and a thickness of 340 μm. This refractory insulating tape was wound in two layers at a high speed at a tape winding speed of about 22 m / min in 1/2 wrap around a copper conductor having an outer diameter of 2.0 mm.

The thus prepared Examples 1 and 2,
The adhesiveness of the overlapping portions of the composite tapes of Comparative Example 1, Comparative Example 2, and Comparative Example 3 and the fire-resistant insulating tape was compared. In the case of Comparative Example 1, since the glass fiber woven fabric was used, the step due to the reinforcing layer was conspicuous due to the effect of the weave, and the finish lacked in density. In the case of Comparative Example 2, since the glass fiber non-woven fabric was used, the flatness as a sheet was relatively good, and the flexibility and cushioning property were improved. And adhesion was incomplete. In the case of Comparative Example 3, since the glass fiber and the mica were mixed, there was no gap at the overlapping portion of the refractory insulating tape, but the nonwoven fabric itself had a low density.

On the other hand, in Example 1, since a sheet integrally formed by blending flat fibers and mica is used, a structure in which the overlapping portions of the refractory insulating tape are continuous is provided. For this reason, the adhesiveness and the airtightness were far superior to those of the comparative example, and it was shown that high-speed and dense tape winding was possible. Since the sheet is very thin, has high smoothness and is strong, there is no problem even if it is wound twice. Further, since the flattening ratio of Example 2 was small, the flattening effect was less than that of Example 1.

Next, these Examples 1, 2 and Comparative Examples
1, 0.8 m on the products of Comparative Examples 2 and 3 by extrusion
With a m-thick polyethylene insulation layer and a 1.5-mm-thick polyvinyl chloride sheath,
The fire resistance test described in No. was conducted. Example 1, Example 2, Comparative Example
1, Comparative Example 2, 15 minutes after the start of the fire test of each wire of Comparative Example 3,
Table 1 shows the insulation resistance values after 30 minutes.

[0039]

[Table 1]

As a result of the fire resistance test, it was found that the decrease in the insulation resistance value with time was smaller in each example than in each comparative example. This is because the HCl gas generated by the burning of the polyvinyl chloride coating used for the sheath layer invades from the slight gap in the overlapping part generated when winding the fire-resistant insulating tape,
Although it is due to the occurrence of the conductivity, the results in Table 1 show that Comparative Example 1 and the airtighter example than Comparative Example 2 most effectively block the invasion of the conductive gas. I support that. Comparative Example 3 was a mixture of glass fiber and mica.However, the presence of the main fiber having a circular cross-section caused the mica scale to lose its orientation, reduce the sheet density, and penetrate the conductive gas, resulting in an insulation resistance value. Seems to have decreased.

[0041]

【The invention's effect】

The inorganic fiber mixed sheet of the present invention has a large contact area between flat fibers and mica or flat fibers and greatly improves the dry paper strength of the sheet itself. A thin integrally molded refractory insulating tape can be obtained. In the case of the flat fiber and the mica-mixed sheet having an aspect ratio of 5.2, the thickness is reduced by 32% and the strength is reduced by 1.8% in comparison of the same rice tsubo of the circular cross-section fiber and the mica-mixed sheet.
Double.

As described above, since the sheet in which the flat inorganic fibers and the mica are mixed can be made thinner than before, the volume occupied by the fire-resistant insulating tape can be reduced.
Useful for thinning wires and saving space. Alternatively, when used as a fire-resistant insulating tape having the same thickness as a conventional composite tape, it is possible to incorporate a sheet that is stronger and has a higher reinforcing effect. In general, the improved sheet strength
Even a thinner fire-resistant insulating tape than before can be used for high-speed winding on a conductor, leading to an improvement in productivity. The most distinctive feature of the integrally formed fire-resistant insulation layer is that the upper and lower layers become continuous at the overlapping part that occurs when the fire-resistant insulation tape is wrapped around the conductor, and the fire of the fire-resistant layer increases the airtightness of the fire-resistant insulation layer. The ability to block conductive gas at the time of generation is improved, and the fire-resistant insulation is greatly improved.

Surface Smoothness and Flexibility The refractory insulating tape of the present invention not only has a large contact area between fibers, but also has few fibers oriented three-dimensionally in the Z-axis direction. This is because the fibers exhibit plane orientation during papermaking. Therefore, the number of fibers protruding from the surface of the nonwoven fabric like a bump is significantly reduced as compared with a fire-resistant insulating tape using glass fibers having a circular cross section. For this reason, in a process such as tape winding, the smoothness when overlapping portions or two layers are wound is good, so that remarkable progress in workability and airtightness can be seen as compared with the related art. In addition, flat fibers are more pliable and more flexible in spite of being a strong sheet because they are more easily bent by a force in the Z-axis direction than fibers having a circular cross section. Therefore, even at the time of high-speed tape winding, the sheet can sufficiently follow the speed, and the winding of the fire-resistant insulating tape is performed uniformly.

Insulation and heat resistance The inorganic fiber sheet according to the present invention can have an insulation resistance of about 10 ¹⁰ Ωcm by using glass for electric insulation as a material, and has sufficient insulation ability for electric wires. . Also, since it is an inorganic material, it does not soften up to at least around 600 ° C, and is sufficiently resistant to some fires. When the temperature is equal to or higher than the softening temperature, the softened glass fills the gaps of the mica, so that the strength is reduced but the airtightness is maintained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electric wire according to an example of the present invention and a comparative example.

[Explanation of symbols]

In the figure, 1 is a polyvinyl chloride sheath layer, 2 is a polyethylene insulating layer, 3 is a composite tape or a fire-resistant insulating tape winding layer (fire-resistant insulating layer), and 4 is a conductor.

Claims (2)

[Claims] 1. A fire-resistant insulating tape for a fire-resistant insulating layer of a fire-resistant wire, in which a fire-resistant insulating layer, an insulating layer, and an outer coating layer are sequentially provided outside a conductor, wherein the fire-resistant insulating tape is a fiber having a flat cross section. (A), mica (B), and binder (C)
And the ratio is the sum of (A) and (B) being 100
(A) is 10 to 60 parts by weight, and (B) is 40 parts by weight.
To 90 parts by weight, and the total of (A) and (B) is 100
(C) 3 to 20 parts by weight with respect to parts by weight. 2. The fire-resistant insulating tape according to claim 1, wherein the fiber having a flat cross section is an inorganic fiber having a fiber cross section having a ratio of major axis / minor axis of 2 or more.