JPH0994826A - Manufacture of randomly oriented fiber reinforced resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber reinforced resin sheet by making the orientation of fibers in a web completely random by forming the flow of dispersion liquid. in the countercurrent direction to the making surface of a moving porous support. SOLUTION: When the making surface 3a of a mesh conveyer belt the downstream side of which is sealed is slanted at an elevation angle, dispersion liquid supplied into a head box 2 flows rapidly toward the upstream side on the surface of a seal part 9 including the liquid which has reached the end part of the downstream side of the making surface 3a to generate a countercurrent so that fibers in the dispersion liquid are stuck randomly to the making surface. In this process, it is extremely effective for the randomization of the fibers to make the inclination 10 deg. or more. The proceeding speed (or making speed) of a mesh belt 3 can be increased with the increase in the inclination so that the productivity of a web tends to improve.

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 fiber reinforced resin sheet produced from a dispersion liquid containing reinforcing fibers and a thermoplastic resin, and in particular, it promotes randomization of fiber orientation and is light in weight. Has high mechanical strength isotropically in the direction,
In addition, the present invention relates to a method for producing a randomly oriented fiber-reinforced resin sheet that exhibits excellent moldability for a large thin product.

[0002]

2. Description of the Related Art As a means for imparting high strength and high rigidity while making the most of the molding characteristics of a thermoplastic resin, a composite technology by adding high modulus fibers is known. The fiber-reinforced thermoplastic resin composite material obtained is used as a material for various structural members that are required to be lightweight and have high rigidity and high strength. These materials are usually molded into a predetermined shape after being heated to a temperature equal to or higher than the melting point of the thermoplastic resin that is the matrix, and particularly a plate or sheet suitable for molding using a press machine or molding of large-sized parts. The shape-like material is called stampable sheet, and its excellent mechanical strength, molding processability, and mass productivity have led to an increase in demand centering on automobile structural members and interior materials.

There is a wet method (paper making method) as a typical method for producing a conventional stampable sheet. This is to disperse discontinuous fibers and a thermoplastic resin in a surfactant-containing aqueous medium containing microbubbles, and make the dispersion on a porous support (so-called wire mesh, hereinafter mesh belt). A non-woven web is prepared by the method described above, and the web is heated and pressed and then solidified to produce a stampable sheet (Japanese Patent Laid-Open No. 60-158227, Japanese Patent Publication No. 2-4842).
No. 3), which has attracted particular attention in recent years because it is possible to easily manufacture an ultralight and highly rigid expansive material.

[0004]

For example, in a stampable sheet used for a rear package of an automobile part, an integrally molded ceiling material, etc., in addition to its characteristics of light weight and high strength,
Isotropic mechanical strength is required. In order to fully exhibit these properties, it is necessary to randomly orient the reinforcing fibers.

However, in the case of the above-mentioned conventional technique for making a stampable sheet, when the mixture of the reinforcing fiber and the thermoplastic resin is made on the mesh belt, basically, the dispersion liquid of both is made to make the mesh belt. Since the fibers flow in the advancing direction with respect to the surface, the stripped reinforcing fibers are inevitably oriented in the advancing direction of the papermaking surface along the flow direction. For this reason, it is difficult to completely randomize the orientation of the fibers in the mixture of both materials (called the web) that has been removed, and it is unidirectional, resulting in the manifestation of mechanical strength anisotropy in the stampable sheet. There is a problem.

Therefore, the present invention has been made in view of such conventional problems, and by controlling the flow direction of the dispersion liquid supplied to the papermaking surface of the mesh belt,
It is an object of the present invention to provide a method for producing a randomly oriented fiber reinforced resin sheet, which is capable of completely randomizing the orientation of fibers in a web and imparting isotropy to the mechanical properties of the sheet.

[0007]

The invention according to claim 1 of the present invention, which achieves the above object, provides a paper-making surface of a porous support for moving a dispersion containing discontinuous reinforcing fibers and a thermoplastic resin. In the method for producing a randomly oriented fiber-reinforced resin sheet for continuously forming a sheet-shaped web while supplying, the flow of the dispersion liquid is formed in a countercurrent direction with respect to the paper-making surface of the moving porous support. It is characterized by.

According to a second aspect of the present invention, a sheet-like web is continuously formed while supplying a dispersion containing discontinuous reinforcing fibers and a thermoplastic resin to the moving surface of a porous support. In the method for producing a randomly oriented fiber-reinforced resin sheet, most of the supply flow rate of the dispersion liquid is sucked in the first half of the liquid contact length with the dispersion liquid of the porous support papermaking surface. is there.

Here, the majority of the supply flow rate of the dispersion liquid can be at least about 90% (claim 3). The invention according to claim 4 of the present invention is the invention according to claim 2 or 3, wherein the papermaking surface of the porous support is inclined in the traveling direction so as to form an elevation angle with respect to the horizontal plane. It is a feature.

Here, the magnitude of the elevation angle can be specifically at least about 10 ° (claim 5).
Further, the invention according to claim 6 of the present invention is the invention according to claims 1 to 5, wherein the dispersion is used to cover the papermaking surface of the porous support that moves, and the upstream part, the midstream part, and It can be supplied from any of the downstream parts toward the most upstream part of the paper making surface.

Thus, in the method for producing a randomly oriented fiber reinforced resin sheet according to the present invention, the dispersion liquid is supplied in the countercurrent direction to the paper making surface of the mesh belt so that the moving direction of the paper making surface of the mesh belt is changed. The flow direction of the dispersion becomes opposite. This causes an effect that the reinforcing fibers in the dispersion liquid are inverted when they land on the papermaking surface, but the reinforcing fibers are randomly deposited in the process. That is, countercurrentization of the dispersion flow is the key to randomizing the fiber orientation.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As the discontinuous reinforcing fibers used in the present invention, inorganic fibers such as glass, metal and carbon fibers or organic fibers having a fiber length of several millimeters to several tens of millimeters are used alone or in combination. Used in combination with more than one type.
If the fiber length is too short, a sufficient reinforcing effect cannot be obtained. On the other hand, if the fiber length is too long, the fluidity during molding becomes low.

As the thermoplastic resin, polyethylene, polypropylene, polyamide, polyester, polystyrene, vinyl chloride resin or the like is used alone or in combination of two or more in the form of powder, fiber, flakes or the like.

The weight ratio of reinforcing fiber to thermoplastic resin is 20.
Used from / 80 to 70/30. If the reinforcing fibers are excessively blended, it becomes difficult to uniformly impregnate the thermoplastic resin into the fibers, and the fluidity tends to decrease during molding. On the other hand, if the reinforcing fibers are blended too small, the reinforcing effect will be reduced.

Embodiments of the present invention will be described below in comparison with a conventional case with reference to the drawings. FIG. 1 shows an outline of the manufacturing process of the randomly oriented stampable sheet of the present invention. Glass fiber (hereinafter G
Polypropylene (hereinafter, referred to as PP) as a thermoplastic resin is added to water containing a surfactant in the dispersion tank 1 at a predetermined ratio, and stirred to foam and disperse air fine bubbles. Prepare the liquid.

This foamed dispersion (hereinafter, simply referred to as a dispersion) is fed into the head box 2. Head box 2
A mesh belt 3, which is an endless belt-shaped porous support that rotates in one direction, and a suction box 4 that is in contact with the back surface of the mesh belt 3 are disposed in the lower part of the. As shown by 4a to 4f in FIG. 1, the suction box 4 is divided into six small chambers from the upstream side to the downstream side, and each chamber is kept at a negative pressure. A suction valve V for controlling the amount of foam liquid suction (amount of drainage) is installed in each chamber.

The dispersion liquid sent to the head box 2 is supplied to the upper surface (paper-making surface) 3a of the moving mesh belt 3, and the foam liquid is sucked and removed by the suction box 4, and the discontinuous reinforcing fiber GF and the thermoplastic resin. The particles PP are placed on the paper-making surface 3a of the mesh belt 3 to make the web W. The web W is dried by the dryer 5 and wound into a coil if necessary. The dried web W is heated and pressed by the hot press 6 and then cooled and solidified to form a dense sheet.

The stampable sheet manufacturing method of the present invention comprises:
The flow direction of the dispersion liquid in the headbox 2 (FIG. 2, solid line arrow symbol f _L ) is in the opposite direction (countercurrent) to the traveling direction of the papermaking surface 3a of the mesh belt 3 (broken line arrow symbol f _B ). The basic idea is to As a result, the reinforcing fibers GF in the dispersion liquid are reversely mounted, and the fibers GF are prevented from being uniformly aligned in the traveling direction of the papermaking surface 3a, and randomization is promoted.

By the way, in the case of the conventional wet process for manufacturing a stampable sheet shown in FIG. 3, the flow direction (f _L ) of the dispersion liquid in the head box 2 is the traveling direction (f _B ) of the papermaking surface 3 a of the mesh belt 3. And the reinforcing fibers GF in the dispersion liquid are naturally oriented in the traveling direction of the papermaking surface 3a without being inverted.

As a means for achieving the countercurrent relationship between the flow of the dispersion liquid and the traveling direction of the papermaking surface 3a of the mesh belt in the present invention, the papermaking surface 3a of the mesh belt is used for the majority of the supply flow rate of the dispersion liquid. It is effective to suction in the first half of the length in contact with (hereinafter referred to as the liquid contact length, which corresponds to almost the entire length of the head box 2).

More specifically, it can be said that at least about 90% of the flow rate of the dispersion liquid is preferably suction filtered at a portion within the upstream half of the length of the papermaking surface 3a in contact with the dispersion liquid. Paper-making start portion of the paper-making surface 3a (that is, the paper-making surface 3a
In the uppermost part of the), a virgin surface where no web is present always appears, and the dispersion liquid in the head box 2 moves to the virgin surface because the liquid resistance is minimal, and tends to be sucked there. Occurs. Therefore, the majority of the flow rate of the dispersion liquid (at least about 90%) is sucked within the upstream half of the length of the papermaking surface 3a in contact with the dispersion liquid, and the suction on the downstream side is almost suppressed. The countercurrent to the paper making surface 3a is promoted, and the random landing of the fibers can be reliably achieved.

However, in this case, the lower limit value of 90% of the flow rate of the dispersion liquid does not have a strict critical meaning that the randomization of the fibers can no longer be obtained if the lower limit value of the dispersion liquid is less than this value. . The same applies to the fact that suction is carried out within the upstream half of the papermaking surface of the mesh belt, and randomization of the fiber orientation is not realized if the upstream half is exceeded. Regarding this point, it is necessary to consider the relationship with the fiber orientation index described below.

That is, as an evaluation of the orientation of the fibers of the stampable sheet, the orientation index Jm value (reference: "Measurement of fiber orientation angle distribution using fiber shadow information of long fiber aggregates" Yaguchi / Kikai)・ Koshimoto, Hojo, Tamagawa; 39th Joint Conference on Plastic Working, No. 233, 1988) can be used. This is to obtain the fiber orientation angle distribution by image-processing the density information of the soft X-ray photograph of a sample such as a stampable sheet in which fibers are extremely difficult to identify.

Here, the orientation index Jm is a parameter indicating the degree of fiber orientation. Jm = + 1 is a unidirectional orientation of all the reinforcing fibers in the reference axis direction. 0 is a completely random orientation. -1 is a total reinforcement in the direction orthogonal to the reference axis. Indicates that the fibers are unidirectionally oriented.

The material whose fiber orientation is unidirectional means that the orientation index Jm is 0.35 or more. When Jm is in this range, in a typical fiber-reinforced thermoplastic resin composite material, the ratio of mechanical properties between the principal axis direction of fiber orientation and the direction orthogonal thereto becomes 3 or more. Therefore, Jm is 0.35
The product sheet described above may be considered as a material that can be used as a virtually unidirectional material that has anisotropy in mechanical properties such as bending strength and tensile strength.

In the present invention, based on this fact, a stampable sheet having a Jm value of −0.1 to 0.1 is defined as a random material. If the Jm value is within this range, the ratio of mechanical properties such as bending strength and tensile strength of the product sheet has been clarified to be in the range of 0.8 to 1.3. Jm is -0.1 to 0.
This is because a stampable sheet having a value of 1 can be said to be a random orientation material having substantially isotropic mechanical properties.
In other words, the absolute value of the orientation index Jm within 0.1 is a practically almost perfect random material,
Even if Jm0.1 + α, which exceeds the range to some extent, it may be acceptable as a random material in actual use. In that case, the flow rate of the dispersion liquid may be less than 90%, which is at least 9% of the flow rate of the dispersion liquid in the present invention.
The value 0% is not strictly critical,
There is room for some variation depending on the specifications required for random product products.

The condition that suction is performed within the upstream half of the papermaking surface also means that the stampable sheet exhibiting an absolute value of the orientation index Jm of 0.1 or less can be efficiently produced. Therefore, similarly to the limitation of the flow rate of the dispersion liquid, it can be said that the limitation range of the suction area can be changed according to the allowable range of the value of the orientation index Jm in actual use of the stampable sheet.

The total flow rate of the dispersion liquid, that is, 100%
It is also within the scope of the present invention to suck the paper in the front half of the papermaking surface. However, even in that case, the latter half of the papermaking surface is in contact with the liquid although suction of the dispersion is not performed. Such a state occurs, for example, when the dispersion liquid is supplied into the head box 2 from the upstream at a high flow rate, or conversely when the dispersion liquid is supplied from the downstream. When the flow velocity is high, a part of the dispersion reaches the non-suctioned second half of the papermaking surface and then flows back to the first half.
Due to the reverse flow, the fiber orientation is randomized. When it is supplied from the downstream of the head box 2, the entire dispersion liquid flows backward in the non-suctioned second half part against the progress of the paper making surface, and the fiber orientation becomes random.

On the other hand, when the whole of the dispersion liquid is sucked in the front half of the paper making surface while the dispersion liquid hardly reaches the latter half of the paper making surface, the filtration area of the paper making surface is simply halved. No backflow of the dispersion liquid to the papermaking surface occurs. Therefore, randomization of fibers cannot be achieved. Further, it is practically too low in productivity to suck most of the flow rate of the dispersion liquid in an area much smaller than half of the papermaking surface 3a, for example, an extremely narrow area such as a few% on the upstream side, which is practically used. Can not serve.

To set the suction flow rate and suction area of the papermaking surface in the present invention, the suction box 4 is partitioned into a plurality of sections in the traveling direction of the papermaking surface 3a of the mesh belt, and a suction valve V is provided for each section. This can be done by adjusting the valve opening. By adjusting the suction valve V of a specific section in the range of fully open to fully closed, the substantial suction amount of the section can be freely adjusted. For example, the suction valve V of the half section on the downstream side of the suction box 4 can be adjusted.
By closing the sheet to a state close to the fully closed state and substantially sealing the downstream papermaking surface 3a, 90% or more of the flow rate of the dispersion liquid can be easily sucked in the upstream half of the papermaking surface 3a of the mesh belt. .

The randomization of the fibers of the stampable sheet in the present invention is achieved more reliably by controlling the dispersion liquid flow rate and the papermaking surface as described above, and by making the papermaking surface 3a an upward slope (elevation angle) in the traveling direction. can do. That is, as schematically shown in FIG. 2, when the papermaking surface 3a of the mesh belt whose downstream side is sealed is tilted at an elevation angle in the traveling direction, the dispersion liquid supplied into the head box 2 is located downstream of the papermaking surface 3a. As a result of rapidly flowing toward the upstream side on the surface of the sealing portion 9 including the portion having reached the tip of the side, a countercurrent is generated,
The fibers in the dispersion are randomly placed on the papermaking surface. It was experimentally confirmed that the inclination angle in this case is extremely effective for randomization when the angle is 10 ° or more (described later). The larger the inclination angle, the mesh belt 3
It is possible to increase the progressing speed (that is, the papermaking speed) of the web and the productivity of the web tends to be improved. The upper limit of the inclination angle is 90 °, but it is preferably 45 ° from the practical viewpoint.

In the above description, as a method of greatly suppressing the suction amount on the downstream side of the papermaking surface, the case has been described in which the opening degree of the suction valve V in the downstream section of the suction box 4 is adjusted. However, in addition to this, for example, the opening of the suction port of the section on the downstream side of the suction box 4 may be closed.

Next, the production method of the present invention and its effects will be specifically described by way of examples.

[0034]

EXAMPLES Examples 1 to 5 and Comparative Examples 1 to 3
In the above, the dispersion liquid was supplied to the head box 2 from the most upstream part of the head box 2 as indicated by an arrow I in FIG.

(Example 1) In the process shown in FIG. 1, a 0.08% by weight aqueous solution of sodium dodecylbenzenesulfonate as a surfactant was stirred in a dispersion tank 1 to form a foaming liquid, and the foaming liquid had a diameter of 11 μm. Then, 0.2% by weight of glass fiber having an average length of 13 mm and 0.3% by weight of granular polypropylene having an average particle size of 0.9 mm were added, stirred and dispersed to prepare a foam dispersion liquid.

This dispersion is sent to the head box 2 and the papermaking surface 3a of the mesh belt 3 (effective papermaking width 1600 m
m) at a feed rate of 2400 l / min. The inclination angle of the papermaking surface 3a was set to 15 °, and the papermaking speed (belt moving speed) was 2 m / min.

Also, by closing the suction valves V of the three downstream side (4d, 4e, 4f in FIG. 2) of the six small chambers of the suction box 4, the fourth to sixth suctions are almost suppressed. Most of the supply flow rate of the dispersion liquid (90% in this embodiment) is sucked by the papermaking surface 3a of the upstream half. That is, the suction amount distribution in the suction box 4 (unit is volume%, hereinafter referred to as vol%) is 4a to 4c.
To 90 vol% and 4d to 4f to 10 vol%.

Under the above conditions, a web having a basis weight of 1000 g / m ² was produced. After drying the obtained web, 210
Heated and pressurized under conditions of ℃ and 5 kg / cm ² , then 20
A dense stampable sheet was obtained by cooling and solidifying under conditions of ° C and 5 kg / cm ² . The orientation of the fibers of the obtained sheet was evaluated by the Jm value.

Soft X-ray photography of the sheet obtained above is carried out,
The orientation index Jm was determined from the image analysis of the film. Table 1 shows the results.

[0040]

[Table 1] Example 2 Except that the inclination angle of the papermaking surface 3a of the mesh belt 3 was set to 20 ° and the papermaking speed was set to 4 m / min.
A stampable sheet was manufactured under the same conditions as in Example 1,
The fiber orientation was evaluated. The results are shown in Table 1.

Example 3 Papermaking surface 3 of mesh belt 3
A stampable sheet was manufactured under the same conditions as in Example 1 except that the inclination angle of a was set to 25 ° and the papermaking speed was set to 6 m / min, and the fiber orientation was evaluated. The results are shown in Table 1.

(Example 4) Papermaking surface 3 of mesh belt 3
A stampable sheet was manufactured under the same conditions as in Example 1 except that the inclination angle of a was set to 30 ° and the papermaking speed was set to 9 m / min, and the orientation of the fibers was evaluated. The results are shown in Table 1.

(Example 5) Papermaking surface 3 of mesh belt 3
A stampable sheet was produced under the same conditions as in Example 1 except that the inclination angle of a was 35 ° and the papermaking speed was 12 m / min, and the orientation of the fibers was evaluated. The results are shown in Table 1.

Comparative Example 1 Papermaking surface 3 of mesh belt 3
The dispersion liquid supplied on the first side of the suction box 4
-Embodiment except that the sixth small chambers (4a to 4f) are uniformly sucked (the suction valve V has the same opening degree) and the inclination angle of the papermaking surface 3a is 0 ° (horizontal). A stampable sheet was produced under the same conditions as in Example 1, and the orientation of the fibers was evaluated. The results are shown in Table 1.

Subsequently, the head box 2 in the present invention
2, the method of supplying the dispersion liquid from the upstream portion of the head box 2 as indicated by the arrow I _u and the method of supplying the dispersion liquid from the middle portion of the head box 2 as the arrow I _m. An experiment conducted by adopting any one of the methods of supplying from the midstream portion of the head box 2 as indicated by the arrow I _d will be described.

Example 6 In the process shown in FIG. 1, a 0.08 wt% aqueous solution of sodium dodecylbenzenesulfonate as a surfactant was stirred in a dispersion tank 1 to form a foaming liquid, and the foaming liquid had a diameter of 13 μm. Then, 0.2% by weight of glass fiber having an average length of 13 mm and 0.3% by weight of granular polypropylene having an average particle size of 0.9 mm were added, stirred and dispersed to prepare a foam dispersion liquid.

This dispersion is sent to the head box 2 and the papermaking surface 3a of the mesh belt 3 (effective papermaking width 400 mm).
Above, 4f out of 6 small chambers of suction box 4
Flow rate 3 from above the chamber toward the papermaking surface directly above chamber 4a
It was supplied at 60 l / min. That is, the inclination angle of the papermaking surface 3a is set to 0 ° (horizontal), and the papermaking speed (belt moving speed) is set to 3 m / min. It was supplied as arrow code Id.

Further, by closing each of the three suction valves V on the downstream side of the six small chambers of the suction box 4, suction of the 4d to 4f chambers is almost suppressed, and most of the supply flow rate of the dispersion liquid is suppressed. (90% in this example) was sucked by the papermaking surface 3a of the upstream half. That is, the suction amount distribution in the suction box 4 (unit is volume%, hereinafter v
ol%) is 90 vol% in rooms 4a to 4c, 4
It was adjusted to be 10 vol% in the d room to the 4f room.

Under the above conditions, a web having a basis weight of 1000 g / m ² was produced. After drying the obtained web, 21
Heat and pressurize at 0 ° C. and 5 kg / cm ² and then 20
A dense stampable sheet was obtained by cooling and solidifying under conditions of ° C and 5 kg / cm ² . The orientation of the fibers of the obtained sheet was evaluated by the Jm value.

A soft X-ray image of the sheet obtained above is taken,
The orientation index Jm was determined from the image analysis of the film. The results are shown in Table 2.

[0051]

[Table 2] (Example 7) A stampable sheet was manufactured under the same conditions as in Example 6 except that the inclination angle of the papermaking surface 3a was set to 10 °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Embodiment 8) The inclination angle of the papermaking surface 3a is set to 20.
A stampable sheet was manufactured under the same conditions as in Example 6 except that the temperature was set to °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Example 9) The inclination angle of the papermaking surface 3a was set to 30.
A stampable sheet was manufactured under the same conditions as in Example 6 except that the temperature was set to °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Embodiment 10) Suction box 4-6
The opening degree of each suction valve V of each small chamber is adjusted so that 60% of the supply flow rate of the dispersion liquid is sucked by the papermaking surface 3a of the upstream half, and the suction flow rate in the suction box 4 is 4a. Room-4c room 60 vol%, 4d-4f
It was adjusted to 40 vol% in the room. Other than that,
A stampable sheet was manufactured under the same conditions as in Example 9,
The fiber orientation was evaluated. Table 2 shows the results.

(Embodiment 11) The dispersion liquid sent from the dispersion tank 1 was used for 4 d of the six small chambers of the suction box 4.
Supply from above the chamber toward the papermaking surface 3a directly above the chamber 4a, that is, from the dispersion liquid supply port arranged in the middle stream portion of the head box 2 as indicated by arrow Im in FIG.
In addition, a stampable sheet was manufactured under the same conditions as in Example 6 except that the inclination angle of the papermaking surface 3a was set to 10 °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Example 12) The inclination angle of the papermaking surface 3a was set to 2
A stampable sheet was manufactured under the same conditions as in Example 11 except that the setting was 0 °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Example 13) The inclination angle of the papermaking surface 3a was set to 3
A stampable sheet was manufactured under the same conditions as in Example 11 except that the setting was 0 °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Embodiment 14) 6 of suction box 4
By adjusting the opening of each suction valve V of each small chamber, 80% of the supply flow rate of the dispersion liquid is sucked by the papermaking surface 3a of the upstream half, and the suction flow rate distribution in the suction box 4 is 4a chamber. Example 1 except that it was adjusted to 80 vol% in the 4c chamber and 20 vol% in the 4d to 4f chambers.
A stampable sheet was manufactured under the same conditions as in Example 3, and the orientation of fibers was evaluated. Table 2 shows the results.

(Example 15) The dispersion liquid sent from the dispersion tank 1 was treated with 4a out of the 6 small chambers of the suction box 4.
Supply from above the chamber toward the papermaking surface 3a immediately above the chamber 4a, that is, from the dispersion liquid supply port arranged in the upstream portion of the head box 2 as indicated by arrow Iu in FIG.
Moreover, the inclination angle of the papermaking surface 3a is set to 15 °, and the papermaking speed is set to 2 m /
A stampable sheet was manufactured under the same conditions as in Example 6 except that the setting was made to be min, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Example 16) The inclination angle of the papermaking surface 3a was set to 20.
Except that the papermaking speed was set to 4 m / min.
A stampable sheet was manufactured under the same conditions as in Example 15 to evaluate the fiber orientation. Table 2 shows the results.

(Example 17) The inclination angle of the papermaking surface 3a was set to 25.
Except that the papermaking speed was set to 6 m / min.
A stampable sheet was manufactured under the same conditions as in Example 15 to evaluate the fiber orientation. Table 2 shows the results.

(Example 18) The inclination angle of the papermaking surface 3a was set to 30.
Except that the papermaking speed was set to 9 m / min.
A stampable sheet was manufactured under the same conditions as in Example 15 to evaluate the fiber orientation. Table 2 shows the results.

(Example 19) The inclination angle of the papermaking surface 3a was set to 35.
The orientation of the fibers was evaluated by producing a stampable sheet under the same conditions as in Example 15 except that the papermaking speed was set to 12 ° and the papermaking speed was set to 12 m / min. Table 2 shows the results.

Comparative Example 2 The dispersion prepared in the same manner as in Example 6 was sent to the head box 2 and, as shown in FIG. 3, six small chambers of the suction box 4 were placed on the papermaking surface 3a of the mesh belt 3. From the upstream side of room 4a
It was supplied at a supply flow rate of 360 l / min so that a liquid flow was formed in the traveling direction of the mesh belt papermaking surface on the papermaking surface immediately above the chamber a. The inclination angle of the papermaking surface 3a was set to 0 ° (horizontal), and the papermaking speed (belt moving speed) was 3 m / min.

Further, chambers 4a to 4 of the suction box 4
The suction was made evenly in each of the small chambers of the f chamber. That is, the suction amount distribution in the suction box 4 is
50vol% in 4c room, 50vol% in 4d-4f rooms
Was adjusted so that

Under the above conditions, a web having a basis weight of 1000 g / m ² was made into a paper, and the obtained web was dried, heated and pressed under the same conditions as in Example 6, and then cooled and solidified to give a dense stampable sheet. Was manufactured to evaluate the fiber orientation. Table 2 shows the results.

(Comparative Example 3) The inclination angle of the papermaking surface 3a was set to 10
A stampable sheet was manufactured under the same conditions as in Comparative Example 2 except that the temperature was set to °, and the orientation of the fibers was evaluated. Table 2 shows the results.

(Comparative Example 4) The suction amount distribution in the suction box 4 is 85 vol% in the chambers 4a to 4c, and in the chamber 4d.
A stampable sheet was produced under the same conditions as in Comparative Example 2 except that the volume was adjusted to 15 vol% in the 4f chamber and the inclination angle of the papermaking surface 3a was set to 15 °, and the fiber orientation was evaluated. Table 2 shows the results.

From the results shown in Table 2, the dispersion liquid was supplied from any one of the downstream part, the midstream part and the upstream part of the headbox toward the most upstream papermaking surface of the mesh belt, and preferably the papermaking surface. Is inclined at least 10 degrees (when the dispersion liquid is supplied from the downstream portion of the head box, the inclination angle may be 0 °), and preferably the majority of the dispersion liquid supply flow rate (at least 90 vol%).
If it is 60 °%, it may be 60 vol%) in the front half (upstream side) of the papermaking surface of the mesh belt to produce a countercurrent in the traveling direction of the mesh belt. It is clear that a stampable sheet having an orientation index Jm of 0.1 or less that can be used as a random material can be reliably obtained.

[0070]

As described above, according to the first aspect of the present invention.
In the invention described, when the sheet-shaped web is formed by the wet method, the flow of the dispersion liquid is formed in the countercurrent direction with respect to the paper-making surface of the porous support, so that the reinforcing fibers in the dispersion liquid are The tendency that the porous support is aligned in the traveling direction is hindered, and as a result, the orientation of the reinforcing fibers is randomized.

In the invention according to claim 2 or 3, when the sheet-shaped web is made by the wet method, most of the supply flow rate of the dispersion is determined by the length of contact with the dispersion on the paper-making surface of the porous support. Since the suction is performed in the first half of the, the dispersion liquid flows backward from the second half of the papermaking surface to promote countercurrent of the liquid in the suction part in the first half, and as a result, the orientation of the reinforcing fibers is randomized. can get.

In the invention according to claim 4 or 5, the papermaking surface of the porous support is inclined so as to form an elevation angle with respect to the horizontal plane, so that the counterflow of the dispersion liquid on the papermaking surface is further promoted. The effect that the randomization of the reinforcing fibers is further promoted is obtained.

However, even when the paper-making surface of the porous support is horizontal, the effect of randomizing the orientation of the reinforcing fibers by supplying the dispersion liquid from the downstream part of the paper-making surface toward the most upstream part is obtained. can get.

Further, in the inventions according to the above-mentioned claims 1 to 5, the orientation of the reinforcing fibers is obtained regardless of whether the dispersion liquid is supplied from the upstream portion, the midstream portion or the downstream portion of the head box. Can be randomized (claim 6
Invention described).

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a method for producing a randomly oriented fiber reinforced resin sheet of the present invention.

FIG. 2 is a schematic view of a main part for explaining the operation of the method of the present invention.

FIG. 3 is a schematic diagram showing an example of a conventional method for producing a fiber-reinforced resin sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dispersion tank 2 Head box 3 Porous support (mesh belt) 3a Paper making surface 4 Suction box W Web

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 101: 12 105: 12 (72) Inventor Yuichi Uchida 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made by Kawasaki (72) Inventor, Osamu Nishimura, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Pref. Technical Research Institute of Iron Co., Ltd.

Claims (6)

[Claims] 1. A method for producing a randomly oriented fiber-reinforced resin sheet, in which a sheet-shaped web is continuously produced while supplying a dispersion containing discontinuous reinforcing fibers and a thermoplastic resin to the paper-making surface of a moving porous support. In, the flow of the dispersion liquid,
A method for producing a randomly oriented fiber-reinforced resin sheet, which is characterized in that it is formed in a countercurrent direction with respect to the paper-making surface of the moving porous support. 2. A method for producing a randomly oriented fiber-reinforced resin sheet, wherein a sheet-shaped web is continuously made into paper while supplying a dispersion containing discontinuous reinforcing fibers and a thermoplastic resin to the paper-making surface of a moving porous support. 2. The random-oriented fiber-reinforced resin sheet according to claim 1, wherein most of the supply flow rate of the dispersion liquid is sucked in the first half of the contact length with the dispersion liquid on the paper making surface of the porous support. Manufacturing method. 3. The method for producing a randomly oriented fiber-reinforced resin sheet according to claim 2, wherein the majority of the supply flow rate of the dispersion liquid is at least about 90%. 4. The production of a randomly oriented fiber reinforced resin sheet according to claim 1, wherein the paper-making surface of the porous support is inclined in the traveling direction so as to form an elevation angle with respect to the horizontal plane. Method. 5. The elevation magnitude is at least about 10 °.
The method for producing a randomly oriented fiber-reinforced resin sheet according to claim 4. 6. The dispersion liquid is supplied from any one of an upstream part, a midstream part and a downstream part of a head box covering the paper making surface of the moving porous support toward the most upstream part of the paper making surface. The method for producing a randomly oriented fiber-reinforced resin sheet according to any one of claims 1 to 5, characterized in that.