JPH09109310A - Manufacture of molded sheet material, fiber reinforced molded sheet material manufactured thereby, and front core of safety shoes using the material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber reinforced molded sheet material which does not lower moldability and has high strength. SOLUTION: A molded sheet material in which pellets prepared by cutting a rod in which a bundle of reinforcing monofilaments is impregnated with a resin, or chips prepared by cutting a plate in which a cloth woven with the reinforcing fibers is impregnated with the resin are collected and heat-pressed. Since the content of the reinforcing fibers is large in the sheet material, high strength is obtained. Since the resin of smaller molecular weight is used, the fluidity is not lowered. Therefore, a product of high strength is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded sheet material, a fiber reinforced molded sheet material produced by the method, and a toecap of a safety shoe using the same.

[0002]

2. Description of the Related Art Glass fibers used as reinforcing fibers for synthetic resin molded products include short fibers and long fibers. In the case of molded products using long fibers, the fibers are dispersed in a synthetic resin matrix in different directions. Known are random mat-shaped products, cross-matted products in which long fibers are woven, and unidirectional mat-shaped molded products in which long fibers are aligned in one direction. Among these molded products, short-fiber or long-fiber random mat-shaped products have low impact strength and therefore do not satisfy the conditions of JIS standard required as a toecap of safety shoes, for example. On the other hand, long-fiber cross-matt or unidirectional mat-shaped molded products have poor flowability and thus have a problem of moldability. Even if they are molded, they may not be manufactured without secondary processing. There was a problem that would be high.

For example, as shown in the explanatory view of the cross section of FIG. 4, a resin safety shoe toecap material certified and used in JIS standard has two cross layers 1 in the center and moldability and fluidity on the surface. It has an integral structure with a random layer (skin layer) for improving the property. (I) The shoe tip core is of L grade (for light work): Compressive strength-4
50kg or more, S class (for normal work): Compressive strength-1,1
There is more than 00kg. When manufacturing resin toecaps: L class: 2-3 cross layers, S class: 4 cross layers
It is necessary to properly use the one that contains ~ 8 pieces. Of course, the S class with many cloths improves the rigidity of the material itself, but the insertability into the mold deteriorates and the moldability and fluidity are better than the L class. Inferior defective rate is also high.

(Ii) Toecap materials are classified into L-class and S-class, and the number of cloths in the reinforcing layer is larger in the S-class than in the L-class, which naturally increases the cost. (Iii) Polyamide, which has good adhesion to reinforcing fibers, is used as the matrix (base material) of the material, and the content of reinforcing fibers is as high as 48 to 54%, and the polyamide itself absorbs water and is filled in a mold during molding. If the raw material of the material is not accurately set, the skin layer loses the flow balance with respect to the core layer, causing welds in the molded product, and lowering the strength of the toecap. This appears because the strength is reduced due to water absorption and the strength of the molded product becomes uneven.

[0005]

DISCLOSURE OF THE INVENTION The present invention, when used in the production of safety shoe toecaps and the like, has a good moldability and a method for producing a molded sheet material capable of producing a product having high strength, a molded sheet material. And, it is intended to provide a toecap of a safety shoe using the same.

[0006]

The constitution of the present invention for solving the above problems is a method for producing a molded sheet material as set forth in the claims, and a fiber-reinforced molded sheet material produced by the method. And the toecap of safety shoes. That is, the manufacturing method of the molded sheet material of the present invention,
First, a composite molding material containing reinforcing fibers arranged in a specific direction, for example, pellets obtained by cutting synthetic resin impregnated in unidirectional reinforcing fiber material or woven reinforced fiber material is impregnated with synthetic resin. A cut sheet obtained by cutting the cut product is assembled and heated and pressed to produce a molded sheet material.

The molded sheet material produced by the above method has a reinforcing fiber material content of 55 to 80 wt%. Further, it is necessary that the molecular weight of the resin is 1,000 to 25,000. The resin is a thermoplastic resin selected from polyamide, polybutylene terephthalate, and polyphenylene sulfide, and the reinforcing fiber is preferably selected from glass fiber, carbon fiber, aramid fiber, and metal fiber. is there. The toecap of the safety shoe of the present invention is produced by heating and press-molding such a fiber-reinforced molded sheet material. The method for producing the molded sheet material of the present invention will be described in detail with reference to FIG. 1. A bundle or mat of reinforcing fibers aligned in one direction is impregnated with a synthetic resin to form a rod or plate (FIG. 1a).

This rod or plate has a predetermined size, that is, a length of 3 to 50 mm, a width of 1 to 40 mm and a thickness of 0.1.
Cut to size in the range of 10 mm into pellets or cuts (Fig. 1b). The pellets or cut pieces thus produced are collected and arranged in a predetermined thickness (FIG. 1c).
It is heated and pressed to obtain a molded sheet material in which reinforcing fibers are arranged in a random plane direction (Fig. 1d, e). This material has reinforced fibers arranged in all directions in a plane, that is, at random, and its content is large. Therefore, if a toecap for shoes is made using this material, a toecap with high impact strength and compression strength can be obtained. .

A conventional random mat, that is, a material in which reinforcing fibers are mixed with a synthetic resin and dispersed randomly and uniformly, for example, a pencil corresponding to the reinforcing fibers is randomly placed in a box. It can be said that the material is filled with synthetic resin, whereas this material is made into a random shape after the synthetic resin is filled into the gap where the reinforcing fiber pencils are aligned in one direction. Since it can be compared, the content of reinforcing fibers is relatively high. Therefore, since the fluidity of the material becomes insufficient, a resin having a small molecular weight, that is, a resin having a molecular weight of 10,000 to 25,000 is used to maintain the fluidity, and the molded product has a high strength. If the molecular weight is less than 10,000, the physical properties of the resin itself, which plays a role of an adhesive for reinforcing fibers, deteriorates and the strength of the composite material as a whole decreases. If the molecular weight exceeds 25,000, the fluidity deteriorates. .

Further, as is clear from FIG. 3 that the content of the reinforcing fiber is less than 55 wt%, it becomes difficult to achieve the in-house standard strength of 1,500 kg (JIS standard 1,100 kg × safety factor) of the S class toecap. , 80 wt%, the amount of resin becomes relatively small, and at the same time, the adhesive effect to the reinforcing fibers also decreases, the strength of the composite material itself decreases, and the reinforcing fibers increase, resulting in poor moldability. The types of the resin matrix and the reinforcing fibers forming the composite material composed of the resin and the reinforcing fibers are as follows.

Resin (matrix: matrix) -polyamide (nylon 6, nylon 66, nylon 12), polypropylene (PP), polycarbonate (PC), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyether There may be mentioned thermoplastic resins such as ether ketone (PEEK), of which nylon 6, polybutylene terephthalate (PB)
T) and PPS are preferred because of their low viscosity and ease of molding. -Type of reinforcing fiber-glass fiber (GF), carbon fiber (CF), aramid fiber, metal fiber, etc. can be mentioned.

The heating temperature for heating and pressurizing this composite material to form a fiber reinforced sheet is 210 ° C to 350 ° C. If the temperature is below 210 ° C, it will take time for the resin to melt,
Or, some resin may not melt depending on the type of resin. 3
If the temperature exceeds 50 ° C., the thermal deterioration of the resin causes a large difference in the physical properties of each material. Also, the pressure to pressurize is 10 kg.
/ Cm ^{2 to} 80 kg / cm ² . If it is less than 10 kg / cm ² , voids (air bubbles) containing air are generated due to insufficient pressure, and if it exceeds 80 kg / cm ² , excessive pressure is applied to the sheet material, causing warpage of the sheet material due to internal stress, strain or plate. Non-uniform thickness occurs.

When the toe core of a safety shoe is molded by using the molded sheet material thus produced, it is not necessary to use the materials for L grade and S grade respectively as in the conventional case, and L grade,
It can be used as a common material for S grade, and it can be a reliable product with stable strength. By using the molded sheet material of the present invention for the random layer (skin layer) of FIG. 4, and further interposing a cross layer (reinforcing layer) in the random layer,
A molded sheet material having higher strength can be provided.

[0014]

[Examples] The results of testing a toecap made of nylon 6 containing glass fiber, which is the most popular material as a composite material for the toecap of safety shoes, are shown below. However, the conventional materials shown in Table 1 below have the structure shown in FIG. 4, and as the cross layer 1, a polyamide resin layer containing a special woven glass fiber; 8 ply (layer) is used, and the skin layer 2 is used.
45% of long glass fibers with a length of 2 inches
It uses a composite material of nylon 6 containing. The material of the present invention shown in the following table is a molded sheet material made of nylon 6 containing 70 wt% of glass fiber having a length of 25.4 mm, and its manufacturing conditions are as follows.

Cut piece size for sheet material: 10 (W)
X 25.4 (L) x 0.15 (t, mm) unidirectional material, sheet mold dimensions and mold temperature; 150 x 300 x 3
(T, mm), 250 ° C., sheet molding pressure; 25 (kg / cm ² ) molding time; 30 (minutes)

[0016]

[Table 1]

As is clear from the results shown in Table 1, the material of the present invention has good moldability and fluidity, and the strength of the molded product is stable. If the toe box absorbs water due to perspiration of the foot, the compressive strength is lowered. As the water absorption rate increases, the strength decreases. The result is as shown in FIG. Water absorption rate (%)
Comparing the strengths of the conventional material and the material of the present invention, the strength of the material of the present invention is remarkable as compared with the conventional material because the resin content is small and the reinforcing fibers are large. FIG. 3 shows the relationship between the glass fiber content and the strength (compressive strength) of the toecap in the toecap made of the glass fiber reinforced molded sheet material.

The materials and their molding conditions are as follows.・ Material: Glass fiber (length 25.4 mm) / PA6, thickness 3 mm sheet ・ Molding condition: Sheet preheating condition, 370 ° C. × 210 seconds Mold temperature 130 ° C. Molding pressure 550 kg / cm ^{2 As} is clear from FIG. By using the fiber-reinforced molded sheet of the present invention, a toecap having much higher compression strength than the toecap of conventional safety shoes can be produced.

[0019]

As described above, the fiber-reinforced molded sheet produced by the method of the present invention has high strength and excellent moldability. Therefore, the toecap of the safety shoe made of this molded sheet has extremely high compression strength.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a manufacturing process of a molded sheet material of the present invention,

FIG. 2 is a graph showing the relationship between the water absorption rate of the safety shoe toecap and the strength (compression strength),

[Fig. 3] Glass fiber content and strength of the toecap (compression strength)
A graph showing the relationship with

FIG. 4 is an explanatory view of a cross section of a row of toecaps for safety shoes.

[Explanation of symbols]

 1 Cross layer (reinforced layer) 2 Random layer (skin layer)

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Claims (10)

[Claims] 1. A method for producing a molded sheet material, which comprises cutting a composite molding material containing reinforcing fibers arranged in a specific direction into a predetermined shape, assembling it into a flat shape, and heating and pressing. . 2. The method for producing a molded sheet material according to claim 1, wherein the reinforcing fiber materials contained in the composite molding material are arranged in one direction or are woven. 3. The method for producing a molded sheet material according to claim 1 or 2, wherein the composite molding material is in the form of pellets or sheets. 4. A cut piece of the composite molding material has a length of 3 to 50 m.
m, width 1-40 mm, thickness 0.1-10 mm, The manufacturing method of the molded sheet material in any one of Claims 1-3 characterized by the above-mentioned. 5. The molded sheet according to claim 1, wherein a heating temperature is 210 to 350 ° C. and a pressure is 10 to 80 kg / cm ² when the molded sheet material is manufactured. Material manufacturing method. 6. A fiber reinforced molded sheet material, wherein the content of the reinforced fiber material is 55 to 80 wt%. 7. A resin having a molecular weight of 1,000 to 25,000.
7. The fiber-reinforced molded sheet material according to claim 6, which is 0. 8. The resin is a thermoplastic resin selected from polyamide, polybutylene terephthalate, and polyphenylene sulfide, and the reinforcing fiber is glass fiber, carbon fiber,
The fiber-reinforced molded sheet material according to claim 6 or 7, which is a fiber selected from aramid fibers and metal fibers. 9. The fiber-reinforced molded sheet material according to claim 6, wherein the reinforcing fiber material is woven or knitted. 10. A toecap for safety shoes, which is produced by heating and press-molding the fiber-reinforced molded sheet material according to claim 6.