JPH0424457B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to 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 "FRC"). The present invention relates to a non-glass reinforcing sheet material from which a high-strength fiber-reinforced material with extremely little directionality can be obtained. [Prior art] Various methods have been developed to obtain high performance and highly functional composite materials by reinforcing matrices such as synthetic resins and concrete with fibrous materials such as glass fiber and carbon fiber. Instead of metal materials or building structural materials such as concrete,
In recent years, its importance has been increasing as a highly functional material that is lighter, has higher strength, and has higher elasticity. Conventionally, inorganic fibers such as glass, carbon, and boron have been the mainstream for these reinforcing fiber materials, but with new technological developments in recent years, organic fibers such as aramid, linear polyethylene, and polyvinyl alcohol are also being used. Various methods are being considered. In addition, the forms of these fiber materials include filaments made of continuous long fibers, sheets made of continuous or cut fibers, short fibers with a fiber length of 10 mm, and dispersions such as granules and flakes. 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 strands made by accumulating and fixing cut glass fibers. Matsuto is known. [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 matrix content and poor impregnation properties, and there is also a large difference in mechanical properties in the vertical, horizontal, and diagonal directions, resulting in poor uniformity. Sheets produced by wet papermaking have very short short fiber lengths, so they are inferior in mechanical properties such as bending strength, and are also inferior in matrix impregnation, making them prone to air bubbles, which poses problems in product quality control. It was hot. The chopped strand mat made of glass fibers described above has no directionality like woven fabrics, has excellent matrix content change and impregnability, and is low cost, so it is slightly more expensive than woven fabrics. It is considered to be suitable as a reinforcing sheet material, except for the fact that the product strength is low. However, nothing comparable to the chopped strand mat using fibers other than glass fiber has been found. The reason for this is that non-glass fibers, such as carbon fibers, are difficult to cut into bundled tows and tend to generate dust, or even if they can be cut, it is difficult to form them into sheets. This is thought to be because it is difficult to obtain fibers with a length of about 50 mm in the case of other inorganic fibers.
On the other hand, in the case of organic fibers, it is presumed that it is difficult to form them into a sheet while leaving the fibers in a converged state. Therefore, in the present invention, the non-glass fiber length is 25
Using fibers of 150mm to 150mm, it has a strength comparable to or even exceeding that of glass fiber chopped strand mats, which could not be obtained conventionally, and which cannot be obtained with glass fibers. The object of the present invention is to obtain a reinforcing sheet material that can impart various properties such as alkali resistance and light weight to products. [Means for solving the problem] A group of unopened staple fibers with a fiber length of 25 to 150 mm without crimps, and a group of unopened staple fibers without crimps in which a plurality of fibers exist in a converged state. but
They are mixed at a composition ratio of 20:70 to 80:10, each fiber is bonded by crimped adhesive fibers, and at least 30% by weight of all fibers are non-crimped fibers. The present invention relates to a non-glass reinforcing sheet material characterized in that adhesive fibers having shrinkage account for 2 to 50% by weight of the total constituent fibers. [Function] The present invention utilizes non-glass staple fibers having a fiber length of 25 to 150 mm. These fibers include inorganic fibers such as carbon fibers and metal fibers, aramid fibers, polyvinyl alcohol fibers,
Any synthetic fibers such as linear polyethylene fibers may be used as long as they have the property of reinforcing the matrix, but carbon fibers or aramid fibers are particularly suitable for FRP, and vinylon fibers are suitable for FRC. Conceivable. These fibrous materials reinforce the matrix and
It has the effect of increasing mechanical properties such as bending strength and imparting high strength and high elasticity to products. Next, to explain the need for multiple fibers to exist in a converged state, which is the gist of the present invention, and the means for obtaining this structure, we will explain the need for a plurality of fibers to exist in a converged state and the means for obtaining this structure. When a nonwoven fabric is formed by the opening means, substantially all the fibers are opened without convergence of each single fiber,
It becomes a homogeneous non-woven fabric. In general, unlike the purpose of the present invention, when the sheet is not made into a composite with a 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 as the purpose of the present invention, the remaining convergent fibers are
By increasing the sheet density, increasing the amount of fiber filling in the matrix, and the rigidity of the convergent fibers,
We discovered that these are essential requirements for providing products with high strength and high elasticity, and by proactively retaining unspread fibers in a converged state, which was previously thought to be undesirable, we were able to obtain high-performance products. This is a completed reinforcing sheet material. Next, some examples of means for making these converging unopened fibers remain in the sheet are as follows. Possible methods include a method of causing fiber opening defects in the fibers and forming a sheet using the well-known card method or random method, or a method of intentionally causing an unspread state by increasing the clearance of the fiber opening machine, etc. It is most advantageous to use non-crimped fibers because it is possible to stably produce sheets with no directionality in a uniformly dispersed state using existing equipment. Moreover, when a sheet is formed using non-crimped fibers, the unopened fibers are uniformly dispersed throughout the sheet and are arranged in multiple directions.
An excellent reinforcing sheet material with extremely high strength, high elasticity, and no directionality can be obtained. When using these non-crimped fibers, the blending amount can be set arbitrarily depending on the purpose of the product, but it is preferable to contain at least 30% by weight to ensure that the unopened fiber group has good persistence and that the product It is desirable because it can improve performance, especially 65 to 95% by weight for FRP and 40 to 80% by weight for FRC.
It is considered suitable to contain % by weight. The composition ratio of the opened staple fiber group and the unopened staple fiber group must be in the range of 20:70 to 80:10, and if the amount of unopened staple fiber is less than this, sufficient bending will occur. Strength and flexural modulus cannot be obtained, and if the amount of unopened staple fibers is larger than this, the web formability will be poor, resulting in a non-uniform sheet material. A particularly desirable composition ratio range of the opened staple fiber group and the unopened staple fiber group is 40:50 to 70:20. Next, the crimped adhesive fibers that are blended to maintain the sheet shape will be explained. This can also be selected as appropriate depending on the use and purpose for which the sheet material of the present invention is used. Any material may be used as long as it can be plasticized or melted with a solvent or heated to exhibit adhesive properties. These fiber materials include polyolefin, polyester,
Thermoplastic fibers such as polyamide-based, vinyl chloride-based, or composite fibers thereof, and solvent-soluble fibers such as water-soluble polyvinyl alcohol fibers and dimethylformamide-soluble aramid fibers can be used, and from the viewpoint of workability etc. It is advantageous to use polyolefin composite fibers for thermoplastic fibers, and polyvinyl alcohol fibers for solvent-soluble fibers. 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 use until the matrix impregnation process. It is sufficient to have a shape-retaining effect to ensure workability.If the blending ratio is high, the shape-retaining property of the sheet increases, but it may reduce the quality of the product. It is desirable that the minimum amount is within the range of %. In addition, in the case of a heavy sheet with a sheet weight exceeding 200 g/m ² , it is necessary to process the sheet with a needle punch machine etc. for a 200
By performing a light needle pricking process of approximately ² cm2, a sheet with excellent shape retention and no delamination can be obtained, and the product performance can be improved by further reducing the amount of adhesive fiber blended. Since it is possible, it can be said to be a suitable means. The reinforcing sheet material of the present invention will be explained in more detail below, but the present invention is not limited to the following examples. [Example] 90% by weight of non-crimped carbon fibers with a fiber length of 51 mm and a fiber diameter of 7 μm were mixed with crimped polyolefin composite fibers (2 denier, 51 mm length), and processed by the carding method. A web of 450 g/m ² was formed in which a group of opened staple fibers and an unopened fiber group in which a plurality of fibers were present in a converged state were mixed. Approximately 50
After needle-pricking the fibers/cm ² , the composite fibers are heated in a fusing oven to melt the low melting point components of the composite fibers, and then compressed at room temperature or at a temperature below the melting point of the low melting component of the composite fibers. Each fiber was bonded to each other to obtain a reinforcing sheet material according to the present invention. During the production process, there were no problems with workability such as web formation and needle stickability, and there was virtually no occurrence of cotton shedding, and the obtained sheet contained unopened carbon fibers converged throughout. The fibers were scattered and extremely homogeneous. About 450 g/m ² of the obtained sheet was coated with unsaturated polyester resin [manufactured by Dainippon Ink Co., Ltd., trade name Polylite FH-123N] by hand lay-up method.
A reinforcing material according to the present invention having a weight of approximately 6000 g/m ² was impregnated with 2500 g/m 2 , laminated in two layers in the same manner, and cured at room temperature, and then after-cured at a temperature of 60°C for ⁵ hours. We created FRP using sheet materials. The bending strength and bending elastic modulus of this product were measured according to JIS K-7203 bending test method for hard plastics, and the results are shown in Table 1. For comparison, a glass fiber chopped strand mat of 450 g/m ² was used in place of the reinforcing sheet material of the present invention, and the same resin as in the example was used to obtain the same thickness. Create FRP in
The same tests as in the examples were conducted and the results are also shown in Table 1. As is clear from Table 1, FRP using the reinforcing sheet material of the present invention has less than half the fiber content and the same thickness compared to that using conventional glass chopped strand mats. is obtained, and it is much lighter than the comparative example.
In addition, it had high strength and elastic modulus, and was significantly superior in mechanical properties and economical efficiency to conventional products.

[Table] The relationship between the blending amount of unopened staple fibers and the flexural strength and flexural modulus of fiber-reinforced plastics obtained using each reinforcing sheet material is described below. The data here are based on the examples, and by changing the carding conditions, the amount of the unopened staple fiber group of carbon fibers in the examples was changed to 10%, 20%, 30%, 50%.
%, 7%. The amount of unopened staple fiber in the above example corresponds to 20%.

[Table] As shown above, the flexural strength and flexural modulus increase as the amount of unspread staple fibers increases, but as the proportion of unspread staple fibers increases, the flexural strength and flexural modulus decrease. The rate of increase is slow. Moreover, as the amount of unopened staple fibers increases, the web forming properties deteriorate and adhesive fibers become difficult to disperse uniformly, so it is quite difficult to use 70% in actual production. Considering the strength required for the fiber-reinforced plastics to be produced and the productivity of the reinforcing sheet material, the amount of unopened staple fibers is preferably in the range of 10 to 70%, preferably 20 to 50%. [Effects] The reinforcing sheet material of the present invention enables high-performance and low-cost chopped strand mats, which were conventionally obtained only from glass fibers, to be made from other fiber materials. This is what I did. For this reason, for example, in the case of sheet materials mainly made of carbon fiber, FRP products can be obtained that are lighter than glass fiber, yet have high strength and high elasticity, and have alkali resistance and electromagnetic shielding properties that cannot be obtained with glass fiber. It is possible to obtain products with excellent properties at a much lower cost than before, or by using synthetic fibers such as aramid fibers and polyvinyl alcohol fibers, workability is much better than before, and at the same weight, glass fibers can be obtained. It is possible to obtain a product with far higher performance than that produced by conventional methods. Therefore, the reinforcing sheet material of the present invention has all the functions essentially required as a reinforcing sheet material, and is highly useful with excellent productivity, economy, versatility, etc. It is.

Claims (1)

[Claims] 1 A non-crimped, opened staple fiber group with a fiber length of 25 to 150 mm and a non-crimped, unopened staple fiber group in which multiple fibers exist in a converged state are mixed in a ratio of 20:70 to 80:10. The composition ratio is mixed, and each fiber is bonded by crimped adhesive fibers,
A non-glass reinforcing sheet material characterized in that at least 30% by weight of the total fibers are non-crimped fibers, and crimped adhesive fibers account for 2 to 50% by weight of the total constituent fibers. .