JPS63211351A - Conductive reinforcing sheet material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to conductive reinforcing sheet materials, and more specifically to fiber reinforced plastics (hereinafter simply referred to as "FRP") and fiber reinforced concrete. (hereinafter simply referred to as rFRCJ), it is possible to obtain a high-strength fiber-reinforced material with extremely little directionality, and because it is electrically conductive, it also has electromagnetic shielding performance and antistatic performance. This invention relates to a conductive reinforcing sheet material.

[Prior Art] By reinforcing a matrix such as synthetic resin or concrete with fiber materials such as glass fiber or carbon fiber, high performance and high a! Various types of composite materials have been developed to obtain high-performance composite materials, and these can be used as lightweight, high-strength, high-elastic, and highly functional materials to replace metal materials such as light alloys or architectural structural materials such as concrete. , has become increasingly important in recent years.

Conventionally, inorganic fibers such as glass, carbon, and boron have been mainstream as these reinforcing fiber materials, but in recent years, new technological developments have led to the use of organic fibers such as aramid, linear polyethylene, and polyvinyl alcohol. Various methods are being considered. In addition, the forms of these fiber materials include:
Thread-like body made of continuous filaments, sheet-like body made of continuous or cut fibers, or fiber length 0ars
Short fibers, granular, flake-like dispersions, etc. are known.

Among these materials, sheet-like materials common to the present invention include woven fabrics made of various raw materials, sheets obtained by wet-forming short fibers, and chopped strand mats made by accumulating and fixing cut glass fibers. It has been known.

On the other hand, with the development of electronics, various electromagnetic shielding technologies have been studied, and metal materials are often used in the form of sheets, 1 mm, or powder, and conductive carbon fibers are often used. Jitsukai Showa 59-
No. 37792, Japanese Unexamined Patent Publication No. 59-47797, and the like disclose shielding materials that utilize conductive fibers similarly to the present invention.

[Problems to be Solved by the Invention] Of the reinforcing sheet materials, the above-mentioned woven fabrics are excellent in that they can yield high-strength products, but they have high processing costs and are poor in economic efficiency, and they also cannot be used with resins, concrete, etc. There are disadvantages such as changes in the content of the matrix and poor impregnability.
There is a large difference in mechanical properties between the lateral direction and the diagonal direction, resulting in poor uniformity. Sheets made by wet papermaking have very short short fiber lengths, so they are inferior in mechanical properties such as flexural strength, and are also inferior in matrix impregnability, making it easy for air bubbles to occur, which poses problems in product quality control. was there.

The above-mentioned chopped strand mat made of glass fiber has no directionality like textiles, has excellent matrix content change and impregnability, and is low cost.
It is considered to be suitable as a reinforcing sheet material, except that the product strength is slightly lower than that of woven fabrics.

However, due to its high rigidity, glass fibers cause irritation to the human body, which is unique to glass, and also have the drawback of easily generating dust due to fiber breakage when molding, etc. Alternatively, there were problems such as inferior safety.

There are no fiber materials other than glass fibers, especially organic synthetic fibers, that are comparable to the chopped strand mat.The reason is that non-glass fibers, such as carbon fibers, are It is difficult to cut the tow and dust is easily generated, or even if it is possible to cut it, it is difficult to form it into a sheet, and in the case of other inorganic fibers, it is difficult to obtain fibers with a length of about 50 nuw. This is thought to be because it is difficult. On the other hand, in the case of 81 fibers,
This is presumed to be because it was considered difficult to form a sheet while leaving the fibers in a converged state.

On the other hand, regarding the electromagnetic wave shielding function, when the metal materials mentioned above are used, they have excellent shielding performance, but they do not serve as reinforcement materials for FRP or FRC, and on the contrary, they cause a decrease in strength, and moreover, only products with high weight can be obtained. If carbon fiber is used, it is considered to be a suitable material because it has excellent reinforcing properties and also has a shielding effect, but like glass fiber, it has poor workability. In addition, carbon fiber usually has a resistivity exceeding 102Ω・cam, making it difficult to obtain sufficient conductivity.For this reason, the raw material is expensive, so it can only be used in limited applications. Ta.

Therefore, in the present invention, the m fiber length of the organic system is 25 to 150.
Utilizing +u+ fibers, it has strength comparable to or even exceeding that of glass fiber chopped strand mats, which could not be obtained conventionally, and durability that cannot be obtained with glass fibers. The purpose of the present invention is to provide a conductive reinforcing sheet material at a low cost that imparts various properties such as alkalinity and lightness to a product, and has excellent conductivity and also has an excellent electromagnetic wave shielding effect.

[Means for Solving the Problems] The present invention provides a group of opened stable fibers (A) with a fiber length of 25 to 150 m5+, and a group of unspread stable fibers in which a plurality of fibers exist in a convergent state. In a reinforcing sheet material made of synthetic fibers in which (B) and each other are bonded together by adhesive fibers (C), 50% by weight or more of all the fibers constituting the sheet material have a specific resistance of 10- 1Ω
Conductive synthetic m fibers of less than 30 cm, and less than 30% by weight of non-conductive adhesive fibers, are interposed in the conductive reinforcing sheet material.

[Function] The present invention utilizes organic stable fibers having a fiber length of 25 to 150 a+m. These fibers may be anything that has the property of reinforcing the matrix, such as aramid fibers, vinylon fibers, linear polyethylene fibers, polyester fibers, polyamide fibers, etc., but in order to obtain sufficient reinforcing action, it is necessary to It is preferable to use high-strength fibers with a fiber strength of 5 g/denier or more, preferably 6 g/denier or more. Especially, strong vinylon fibers and aramid fibers are suitable for FRP, and for FRC,
Vinylon fibers are considered suitable.

The purpose of the present invention is to obtain a sheet material that has reinforcing and conductive properties, so the above stable fibers are
Conductive treatment is performed. As the conductive treatment, any well-known conductive method such as metal plating, metal spraying, or chemical treatment such as dyeing with a metal compound can be applied. The most advantageous method is plating, which provides good conductive properties. Although the metal materials used for these platings can be selected arbitrarily, nickel is the most suitable because the plating process is easy and there is no change in electrical performance over time due to rust etc. I can say that.

In order for a sheet material composed of these electrically conductive stable fibers to have an electromagnetic wave shielding function, it is necessary that the resistivity of the stable fibers is less than QlΩ·cm, and Preferably 10-3Ω・C1
It is desirable that the value is 1 or less in order to obtain an excellent shielding function.

These fiber materials have the effect of reinforcing the matrix, increasing mechanical properties such as bending strength, and imparting high strength and high elasticity to the product.They also provide electrical conductivity to the sheet material, providing excellent dual-magnetic shielding performance and It has two important functions: the function of imparting antistatic properties.

Next, to explain the necessity of the unopened fiber group (B) in which a plurality of fibers are present in a converged state and the means for obtaining this structure, which is the gist of the present invention, crimped fibers are used. When a nonwoven fabric is formed by a conventional fiber opening method such as carding, substantially all the fibers are spread without convergence of each single fiber, resulting in a homogeneous nonwoven fabric. In general, unlike the purpose of the present invention, when the sheet is not made into a composite with the matrix, all the fibers are dispersed very evenly, so the nonwoven fabric has no directionality and has uniform strength throughout, which is preferable. Remaining converged fibers are not preferable because the strength becomes non-uniform.

However, the present inventors have found that when forming a composite with a matrix and obtaining conductive performance as the purpose of the present invention, the remaining convergent Il fibers increase the sheet density and reduce the number of fibers in the matrix. The filling amount will be increased, and as a result,
We discovered that there is no risk of short circuits or poor conductivity due to poor contact between conductive fibers, and the rigidity of the convergent fibers is an essential requirement for providing products with high strength and high elasticity. By proactively retaining unspread fibers in a converged state, which had been thought to be undesirable, a sheet material for electrically conductive reinforcement was completed that yielded a high-performance product.

Next, some examples of means for making these converging unspread fibers remain in the sheet are as follows: using at least 5 offi ffi% or more of non-crimped stable fibers in the total constituent fibers; There is a method of forming a sheet by a well-known card method or random method by causing a fiber opening failure, and after treating the tow with adhesive or wax in advance, cutting it into a predetermined size, and then cutting the tow in a converged state. Possible methods include forming a sheet by a card method using raw materials containing tow, or intentionally creating an unspread state by increasing the clearance of a fiber opening machine.

However, it is most advantageous to use non-crimped fibers because it is possible to stably produce sheets without directionality in a uniformly dispersed state using existing equipment as is. In other words, when non-crimped fibers are mixed with crimped adhesive fibers and spread using a well-known device such as a card, substantially all of the adhesive fibers are spread uniformly, and the entire sheet is uniformly bonded. The crimping of the bonded fibers causes the non-crimped fibers to be partially opened, resulting in a opened stable group (A) and an unopened stable group (B).
) can be obtained with extremely uniform distribution. Moreover,
Since the unspread fiber group (B) is uniformly dispersed throughout the sheet and arranged in multiple directions, it has uniform conductivity in all directions, and has excellent conductivity with extremely high strength and high elasticity and no directionality. A sheet material for gender reinforcement can be obtained.

When using these non-crimped fibers, the blending amount can be set arbitrarily depending on the intended use of the product, but it is preferable to contain at least 50% by weight to ensure that the unopened fiber group has good persistence and that the product It is desirable because it can improve performance, and it is considered more preferable to contain 65 to 97% by weight for FRP and 50 to 90% by weight for F'RC.

Next, the adhesive fibers that are blended to maintain the sheet shape can be selected as appropriate depending on the use and purpose for which the sheet material of the present invention is used. Any material that exhibits adhesive properties by being E-enablized or melted may be used. These fiber materials include suspended wave fibers such as polyolefin, polyester, polyamide, vinyl chloride, or composite fibers of these, water-soluble polyvinyl alcohol fibers, dimethylformamide-soluble aramid fibers, etc. Solvent-soluble fibers can be used, and FR from the viewpoint of workability etc.
For P use, composite fibers of suspended polyethylene-vinyl acetate copolymer and polypropylene are used, and for FRC use, water-soluble polyvinyl alcohol fibers are used to improve workability such as opening. is high, has excellent adhesive strength, and
This is advantageous because moldability is also improved due to relaxation of the bond.

These adhesive fibers maintain the sheet shape and improve workability, and also have the effect of preventing cotton from falling during fiber opening, but since the sheet is not used alone, it is difficult to process the process up to the matrix impregnation process. It is sufficient if the shape retention effect is sufficient to ensure workability, and if the blending ratio is high,
Although it increases the shape retention of the sheet, it may reduce the quality of the product, so it is desirable that the amount is the minimum necessary, within the range of 3 to 30% by weight.

In particular, when the amount of adhesive fibers is 15% or less, preferably 10% on a side, the bonding force between the fibers is small and the bonding between the fibers can be released with a small amount of force, which improves the formability of the sheet. Furthermore, because the blending ratio of non-crimped fibers as reinforcing and conductive materials is high, even when three-dimensional molding is performed with an area increase rate of several hundred percent, sufficient conductive and reinforcing effects can be maintained. Therefore, sheet materials with a low blending ratio of these adhesive fibers are considered to be optimal materials for sheet molding.

In addition, in the case of a heavy sheet with a sheet weight exceeding 2008/m2, 20 to 200 sheets are processed using a needle punch machine, etc. before the sheet is bonded with adhesive fibers, or when the adhesive fibers have become selvable. If a light needle pricking process of about /cm2 is performed, a sheet with excellent shape retention that does not cause delamination can be obtained, and the product performance can be improved by further reducing the amount of adhesive fiber blended. This is a suitable method.

The conductive reinforcing sheet material of the present invention will be described in more detail below, but the present invention is not limited to the following examples.

[Example] Nickel-plated non-crimped vinylon fiber (2 denier, 51n+m length, specific resistance 6.OX 10-3Ω・c
m) Composite fiber (l,
5 denier, 44 mm length, bonding temperature +10°C) and 7% by weight were uniformly blended, and a stable fiber group opened by the carding method and an unopened fiber group in which multiple fibers existed in a converged state were prepared. A mixed 100 g 10+2 wave was prepared.

This web is heated at a temperature of 120°C with the fusing open to melt the low melting point component of the composite fiber, and then crimped at room temperature to a temperature below the melting point of the low melting point component of the composite fiber. The fibers were bonded together to obtain a conductive reinforcing sheet material according to the present invention.

During the production process, there were no problems with workability such as web formation, and there was virtually no occurrence of cotton drop, and the obtained sheet was composed of spread vinylon fibers converged throughout. Unspread vinylon fibers are evenly scattered and the sheet is extremely homogeneous.
H-123N) by hand layup method to approx. 9003
/i2 impregnated, this was similarly formed into two rA layers, and after curing at room temperature, after-curing was performed at a temperature of 60°C for 5 hours to form a conductive reinforcement according to the present invention having a weight of about 2,000 g/m2. A plate-shaped FRP was created using the sheet material used for this purpose (Example 1).

In order to evaluate the performance of this product, the surface resistivity of the sheet material used and the obtained FRP were measured according to the JISK-7203 bending test method for hard plastics.
The flexural strength and flexural modulus of the sample were measured, and the results are shown in Table 1.

In addition, as another embodiment, the above-mentioned resin-impregnated two-layer sheet was molded and cured into a dome shape using a pressurized and heated press device (Example 2). The dispersion rate was about 200%, the moldability was good, and the sheet material of the present invention was in an extremely uniform dispersion state.

This molded FRP was also subjected to surface resistivity and bending tests for molded sheet material only, and the results are shown in Table 1.

In addition, for comparison with these, a glass fiber chopped strand mat of 1008/m2 was used instead of the conductive reinforcing sheet material of the present invention, and the same resin as in Example 1 was used to obtain the same thickness. When FRP was produced in this way, two mats did not have the same thickness; three mats were required to achieve the same thickness, and the product was about 20% heavier.

Regarding this, the same test as in the example was conducted, and the results are shown in Table 1.

As is clear from Table 1, FRP using the conductive reinforcing sheet material of the present invention has excellent conductive performance, and has a higher fiber content than that using the conventional glass chopped strand mat. A product with the same thickness can be obtained with less weight, and it is also slightly lighter than the comparative example, and has high strength and elastic modulus, and has significantly better mechanical properties and economical efficiency than conventional products. It was excellent.

Table 1 [Effects] The conductive reinforcing sheet material of the present invention can produce chopped strand mats with high performance and low cost, which were conventionally obtained only with glass fibers, but can also be produced with a-fiber materials. In addition, it is made electrically conductive.

Therefore, FRPi% is lighter than glass fiber and has high strength and high elasticity! It is possible to obtain products with alkali resistance and electromagnetic shielding properties that cannot be obtained with glass fibers, at a much lower cost than before, and with much better workability than before, and at the same weight as glass fibers. It is possible to obtain products with higher performance than those made from fibers.

Therefore, the conductive reinforcing sheet material of the present invention has all the functions essentially required as a reinforcing sheet material, has excellent conductivity, and has excellent productivity, economy, versatility, etc. It is extremely useful and provides products that cannot be obtained conventionally.

Claims (5)

[Claims] (1) A group of opened stable fibers (A) with a fiber length of 25 to 150 mm and a group of unspread stable fibers (B) in which multiple fibers exist in a converged state are mixed, and between each fiber In a reinforcing sheet material made of synthetic fibers bonded by adhesive fibers (C), 50% by weight or more of all the fibers constituting the sheet material are conductive synthetic fibers with a specific resistance of less than 10^-^1 Ω cm. A conductive reinforcing sheet material comprising less than 30% by weight of non-conductive adhesive fibers. (2) The reinforcing sheet material according to claim 1, wherein the fiber groups (A) and (B) are stable fibers without crimp. (3) The conductive reinforcing sheet material according to claims 1 and 2, wherein the fiber groups (A) and (B) are high-strength fibers with a single fiber strength of 5 g/denier or more. (4) Fiber groups (A) and (B) have a specific resistance of approximately 10^-
The conductive reinforcing sheet material according to claims 1 to 3, wherein the conductive reinforcing sheet material is nickel-plated vinylon fiber with a thickness of 3 Ω·cm, and the adhesive fiber is a composite fiber of polyethylene-vinyl acetate copolymer and polypropylene. (5) The conductive reinforcing sheet material according to claim 1, which is easily moldable and comprises 90 to 97% by weight of fiber groups (A) and (B) and 10 to 3% by weight of adhesive fibers.