JP2020015282A - Manufacturing method of composite material - Google Patents

Abstract

To provide a manufacturing method of a composite material by uniformly spraying a crushed material including a carbon fiber and a thermoplastic resin.SOLUTION: The manufacturing method of a composite material A includes a step of spraying an aggregate Y of a crushed material X including a carbon fiber having a weight average fiber length Lwx of 1 mm or over and a thermoplastic resin, followed by heating solidification, wherein the manufacturing method of the composite material A is characterized by that a variation coefficient of a basis weight of the sprayed aggregate Y is within 40%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a composite material using a crushed material obtained by crushing a carbon fiber composite material.

BACKGROUND ART Fiber-reinforced plastics containing carbon fibers have been developed in various fields because of their light weight and high mechanical properties. For example, Patent Document 1 describes a carbon fiber reinforced plastic including a plurality of small pieces including an aggregate of carbon fibers and a matrix resin. By molding with a small piece of 1 cm ² to 50 cm ^2, it is described that can produce flowability of good moldings. Patent Document 2 describes a crushed material transport pipe that pneumatically transports a crushed glass product. Patent Literature 3 describes a technique of winding sand from a supply hopper through a screen.

JP 2013-018859 A Japanese Patent Publication No. 01-009061 JP 04-215863A

  However, in the invention described in Patent Document 1, it is necessary to arrange small pieces one by one after cutting the stampable sheet, and it takes too much time to arrange the small pieces. Further, the arranged small pieces are only one layer, and even if the molded body is manufactured by pressing this, there is no carbon fiber bridging between the small pieces, and the mechanical properties between the small pieces are extremely weak. .

  In Patent Document 2, although an air stream is used to transport a crushed glass product, studies for pneumatic transport of a crushed composite material containing carbon fibers are insufficient.

  In the invention described in Patent Literature 3, since sand is wound, no case of winding a crushed material containing carbon fibers has been found, and it is difficult to spray an irregularly shaped crushed material.

  Therefore, the present invention provides a method for uniformly scattering a crushed material containing carbon fibers and a thermoplastic resin to produce a composite material.

In order to solve the above problems, the present invention provides the following means.
1. A method of manufacturing a composite material A by spraying an aggregate Y of crushed materials X containing carbon fibers having a weight average fiber length Lwx of 1 mm or more and a thermoplastic resin, and then heating and solidifying the composite material A. A method for producing a composite material A, wherein the basis coefficient of variation of Y is within 40%.
2. 2. The method for producing a composite material A according to 1 above, wherein the crushed material X having spines having a length of 1 mm or more occupies 30% or more of the aggregate Y.
3. 3. The production method according to 1 or 2, wherein the composite material A is produced by spraying the aggregate Y of the crushed materials X from the vibrating feeder.
4. A method of manufacturing the composite material A by storing the assembly Y in a hopper and spraying the assembly Y from a hopper discharge port, wherein a tapered pipe having an air injection port is provided at a lower portion of the hopper, and the composite material A is discharged from the hopper discharge port. The method for producing a composite material A according to any one of the above 1 or 2, wherein the aggregate Y is blown with air in a tapered pipe to homogenize the aggregate Y, and then the aggregate Y is sprayed on a belt conveyor.
5. The aggregate Y is stored in a hopper, the crushed material X is discharged from a hopper discharge port to a rotating roller provided at a lower portion of the hopper, and the aggregate Y of the crushed material X is sprayed from the rotating roller to a belt conveyor. Or a method for producing the composite material A according to any one of 2.
6. 6. The method for producing the composite material A according to 4 or 5, wherein the aggregate Y is scattered by arranging at least three or more hoppers in the width direction of the belt conveyor to obtain a composite material A having a width of 1 m or more.
7. On the aggregate Z containing carbon fibers having a weight average fiber length Lwz and a thermoplastic resin, the aggregate Y is dispersed and heated and solidified to form a layer constituting a laminate with the composite material B derived from the aggregate Z. The manufacturing method according to any one of the above items 1 to 6, which manufactures the composite material A.

  ADVANTAGE OF THE INVENTION According to this invention, since a crushed material can be uniformly scattered and a crushed material can be laminated | stacked on several layers and a composite material can be manufactured, when shape | molding using this, a molded object with favorable mechanical physical properties can be manufactured.

The schematic diagram which shows the structure of the cutting machine 200 used for manufacture of the assembly Y of the crushed material X. The schematic diagram of the dispersion | spreading method of the assembly Y using a vibrating feeder. The schematic diagram of the dispersion | spreading method of the assembly Y using a rotating roller.

[Carbon fiber]
Examples of the carbon fiber used in the present invention include polyacrylonitrile (PAN) -based carbon fiber, petroleum / coal pitch-based carbon fiber, rayon-based carbon fiber, cellulose-based carbon fiber, lignin-based carbon fiber, and phenol-based carbon fiber. However, in the present invention, any of these carbon fibers can be suitably used. Among them, in the present invention, it is preferable to use polyacrylonitrile (PAN) -based carbon fiber from the viewpoint of excellent tensile strength. The carbon fiber used in the present invention may have a sizing agent attached to the surface.

[Carbon fiber length]
The crushed material X in the present invention contains carbon fibers having a weight average fiber length Lwx. The weight average fiber length Lw is preferably from 1 mm to 50 mm, more preferably from 1 mm to 30 mm, even more preferably from 1 mm to 20 mm.

  When Lwx is 50 mm or less, the fluidity of the composite material A does not easily decrease, and a press-formed body having a desired shape can be easily obtained at the time of press-forming. Further, when Lwx is 1 mm or more, it is preferable that the mechanical strength of the obtained press-formed body does not easily decrease.

  The carbon fibers contained in the crushed material X may be different from each other. In other words, the carbon fibers contained in the crushed material X may have a single peak in the distribution of the weight-average fiber length, or may have a plurality of peaks. In addition, carbon fibers contained in an injection-molded body or an extruded body are generally obtained through a kneading step sufficient to uniformly disperse the carbon fibers in an injection-molded body. The weight average fiber length is less than 1 mm.

[Average fiber length]
The average fiber length of the carbon fiber can be determined, for example, by measuring the fiber length of 100 fibers randomly extracted from a molded product to a unit of 1 mm using a caliper or the like, and based on the following equation (1). .
Assuming that the fiber length of each carbon fiber is Li and the measured number is j, the number average fiber length (Ln) and the weight average fiber length (Lw) are generally obtained by the following equations (1) and (2). Can be
Ln = ΣLi / j Equation (1)
Lw = (ΣLi ² ) / (ΣLi) Equation (2)
When the fiber length is constant, the number average fiber length and the weight average fiber length have the same value. The extraction of the carbon fibers from the composite material A can be performed, for example, by performing a heat treatment at about 500 ° C. × 1 hour and removing the resin in a furnace.

[Thermoplastic resin]
The thermoplastic resin (thermoplastic matrix resin) used in the present invention is not particularly limited, and a resin having a desired softening point or melting point can be appropriately selected and used. As the thermoplastic resin, one having a softening point in the range of 180 ° C. to 350 ° C. is usually used, but is not limited thereto.

[Coefficient of variation of the basis weight of the scattered aggregate Y]
The variation coefficient of the basis weight of the scattered aggregate Y in the present invention is 40% or less. The coefficient of variation of the basis weight of the assembly Y in the present invention is calculated by the equation (a) when the entire area in the plane of the dispersed assembly Y is divided at a pitch of 25 mm × 25 mm. For example, in the case where the section of the scattered aggregate Y is 100 mm × 100 mm, it is defined by the variation coefficient measured by dividing the area into 16 sections of 4 × 4.

Coefficient of variation of dispersed aggregate = 100 × standard deviation of total weight / average value of total weight Formula (a)
By setting the variation coefficient of the basis weight of the aggregate Y to 40% or less, it is possible to reduce shaping unevenness and mechanical characteristic unevenness at the time of molding of the composite material A formed by heating at a small pitch. Even in a molded article having a complicated shape, excellent moldability and mechanical properties can be exhibited.

[Crushed material X]
There is no particular limitation on the method for producing the crushed material X. For example, a molding material of a carbon fiber reinforced thermoplastic resin or a scrap obtained in the process of producing a molded body is used. The use of offcuts (hereinafter, sometimes simply referred to as offcuts) produced during the production or molding of molding materials or molded articles can reduce production costs and contribute to resource saving and global environmental conservation. The molding material and the molded body before crushing are not particularly limited. For example, a composite material containing 10 to 70 wt% of carbon fibers described in JP-A-2011-178890 and JP-A-2011-178889, Various materials such as those described in JP-A-2011-241338 in combination with a directional carbon fiber reinforced composite material can also be used.

[Example of manufacturing crushed material X]
FIG. 1 is a schematic diagram showing a structure of a cutting machine 200 used for manufacturing an aggregate Y of crushed materials X according to the embodiment. Cutting machine 200 is a commercially available plastic cutting machine. The broken material, waste material, and manufacturing waste material (101 in FIG. 1) of the molding material or the molded body are supplied to the cutting machine 200 and cut.

  By appropriately changing the cutting blade dimensions, the cutting blade interval, the pulverizing time, and the number of revolutions of the cutting machine 200 and measuring the volume distribution of the cut pieces, the condition that the volume of the cut pieces 102 enters the preferable size of the crushed material X is obtained. Can be adjusted. Further, the cut pieces 102 are passed through a filter 210, and cut pieces having a certain particle size or less are collected as crushed materials X. The cut pieces 102 that do not pass through the filter 210 are supplied to the cutting machine 200 again to perform cutting. Thus, by adjusting the opening area of the filter 210, the crushed material X can be obtained. Regarding the aggregate Y of the crushed materials X, it is preferable that the diameter of the minimum circumscribed circle of the plane having the largest area among the planes of the crushed materials X is 5 to 25 mm. The size of the crushed material X is preferably 1 to 20 mm or less in diameter, more preferably 3 to 15 mm.

[Surface roughness of crushed material]
When the cutting material is cut by the cutting blade of the above-described cutting machine 200, among the surfaces of the crushed material X, there is at least one crushed surface having a surface roughness (Rz) of 500 μm or more.
When the surface roughness (Rz) is large, the crushed materials X are entangled in the aggregate Y, and it is difficult to uniformly scatter the crushed materials X by a normal spraying method. By using the preferred method for producing the composite material A in the present invention, even the aggregate Y of the crushed materials X, which has a larger problem, can be uniformly dispersed.

[Spike of crushed material X]
The cutting blade of the above-described cutting machine 200 becomes hot when used continuously. When the cut material is cut with a hot cutting blade, the thermoplastic resin contained in the cut material is melted, and a crushed material X having spines is manufactured.
When the crushed material X having the barbs having a length of 1 mm or more occupies 30% or more of the aggregate Y, since the barbs of the crushed material X are entangled in the aggregate Y, it is difficult to uniformly scatter with the normal spraying method. By using the preferred method of manufacturing the composite material A according to the present invention, even the aggregate Y of the crushed material X having thorns can be uniformly dispersed.
It is preferable that the crushed material X having barbs having a length of 1 mm or more occupy 40% or more of the aggregate.

[Method of dispersing aggregate Y (using vibratory feeder)]
In the dispersion of the aggregate Y in the present invention, it is preferable to produce the composite material A by spraying the aggregate Y of the crushed material X from the vibrating feeder. FIG. 2 is a schematic diagram showing a method of dispersing the aggregate Y using a vibrating feeder. Since the aggregate Y is scattered on the belt conveyor 302 while vibrating in the vibrating feeder 301, the weight coefficient of variation of the easily scattered aggregate Y can be 40% or less.

  In addition, if two or more vibrating feeders are arranged in the machine direction (MD), even if the weight of the aggregate Y sprayed for the first time is uneven, the weight of the aggregate Y is uniform by the second spray of the aggregate Y. Be transformed into On the other hand, by arranging two or more vibrating feeders in the width direction and reducing the scatter width per unit, the basis weight unevenness of the aggregate Y is also improved.

[Method of spraying aggregate Y (spraying from hopper)]
When the aggregate Y is put into the hopper and the aggregate is sprayed from the hopper discharge port, the crushed materials are entangled or struck in the hopper, so that the crushed material is uniformly and continuously discharged from the discharge port. difficult. Therefore, in the present invention, it is preferable to employ the following method.

1. In the present invention, the method of manufacturing the composite material A by storing the aggregate Y in the hopper and spraying the aggregate Y from the hopper discharge port in the present invention, wherein a tapered pipe having an air injection port is provided at a lower portion of the hopper, It is preferable that the assembly discharged from the hopper discharge port is blown with air in a tapered pipe to make it uniform, and then sprayed on a belt conveyor.
Preferably, compressed air is blown into the air inlet, and the flow rate of the compressed air is preferably 10 NL / min or more and 1000 NL / min or less.
By blowing air on the aggregate Y, the aggregate Y of the crushed material X that is unevenly deposited in the hopper can be made uniform.

2. Use of Rotary Roller In the present invention, the aggregate Y is stored in a hopper (for example, 403 in FIG. 3), and the crushed material X is transferred from a hopper discharge port (for example, a clearance 405 in FIG. 3) to a rotary roller provided below the hopper. It is preferable to discharge and spray the aggregate Y of the crushed material X from the rotating roller to the belt conveyor. At this time, the size of the supply port at the lower part of the hopper is preferably 150 mm or less. If it is 150 mm or less, it is preferable because the aggregate Y of the crushed material X in the hopper is discharged while being pulled out by the rotating roller.

2.1 Rotary Roller The peripheral speed of the rotary roller is not particularly limited, but is preferably 1 m / min or more, more preferably 2 m / min or more.
The roller surface preferably has grooves or projections at intervals of 50 mm or less, and the roller surface may be subjected to graining of 100 mesh or less. Further, it is preferable that the roller surface has a matte finish having a surface roughness Ra (arithmetic average roughness) of 3 μm or more and 15 μm or less. The surface roughness Ra is more preferably 3 μm or more and 10 μm or less, and still more preferably 4 μm or more and 6 μm or less.

3. When the aggregate Y is sprayed from a plurality of hoppers, it is preferable that at least three or more hoppers are arranged in the width direction of the composite material to spray the aggregate Y.
By arranging small hoppers in the width direction, it is possible to reduce the amount of the crushed material X entangled in the hopper, and it is possible to evenly distribute the aggregate Y discharged from the hopper.

[Manufacture of laminated body]
A laminate Y of a composite material A and a composite material B derived from the aggregate Z is sprayed on the aggregate Y on the aggregate Z containing the carbon fibers having the weight average fiber length Lwz and the thermoplastic resin, and solidified by heating. May be manufactured. Here, Lwz> Lwx.

[Volume ratio of carbon fiber]
The carbon fiber volume ratio (Vf) of the carbon fibers contained in the crushed material X can be obtained by the following equation (3).
The carbon fiber volume ratio is not particularly limited, but the carbon fiber volume ratio (Vf) is preferably from 10 Vol% to 60 Vol%, more preferably from 20 Vol% to 50 Vol%, even if it is from 25 Vol% to 45 Vol%. Is more preferred.
Carbon fiber volume ratio (Vf) = 100 × carbon fiber volume / (carbon fiber volume + thermoplastic resin volume) Equation (3)
In the present invention, a carbon fiber volume fraction Vf _x crushing material X, and the carbon fiber volume fraction Vf _B of the composite material B from assembly Z is that satisfy the relationship of Vf _x ≦ Vf _B, the production process preferable.

When used in excised as crushed material X by crushing a composite material B comprising carbon fibers and a thermoplastic resin, Vf X ₌ Vf _B becomes, after crushed scraps of the composite material B, further adding a thermoplastic resin If it produces a crushed material X Te becomes _Vf X <Vf _B. That is, if a manufacturing method that satisfies Vf _X ≦ Vf _B is adopted, the scraps left after cutting out the composite material B can be efficiently used.

[Production of composite material A]
The composite material A heats the aggregate Y assembled on the belt conveyor (for example, 302 in FIG. 2 and 402 in FIG. 3) to melt the thermoplastic resin, melt-bond the aggregates Y, and solidify by cooling. Obtained.

101: Broken material, waste material, manufacturing waste material of molding material or molded body 102: Cut piece 200: Cutting machine 210: Filter Y: Assembly Y
301: Vibratory feeder 302: Belt conveyor 401: Rotary roller 402: Belt conveyor 403: Hopper 404: Gate 405: Clearance 406: Crushed material X

Claims (7)

  A method of manufacturing a composite material A by spraying an aggregate Y of crushed materials X containing carbon fibers having a weight average fiber length Lwx of 1 mm or more and a thermoplastic resin, and then heating and solidifying the composite material A. A method for producing a composite material A, wherein the basis coefficient of variation of Y is within 40%.   The method for producing a composite material A according to claim 1, wherein the crushed material X having barbs having a length of 1 mm or more occupies 30% or more of the aggregate Y.   The manufacturing method according to claim 1, wherein the composite material A is manufactured by spraying the aggregate Y of the crushed materials X from the vibrating feeder.   A method of manufacturing the composite material A by storing the assembly Y in a hopper and spraying the assembly Y from a hopper discharge port, wherein a tapered pipe having an air injection port is provided at a lower portion of the hopper, and the composite material A is discharged from the hopper discharge port. The method for producing a composite material A according to any one of claims 1 and 2, wherein the aggregate Y is blown with air in a tapered pipe to homogenize, and then the aggregate Y is sprayed on a belt conveyor.   The aggregate Y is stored in a hopper, the crushed material X is discharged from a hopper discharge port to a rotating roller provided at a lower portion of the hopper, and the aggregate Y of the crushed material X is sprayed from the rotating roller to a belt conveyor. (2) A method for producing the composite material A according to any one of (2).   The method for producing a composite material A according to claim 4 or 5, wherein the assembly Y is scattered by arranging at least three or more hoppers in the width direction of the belt conveyor to obtain a composite material A having a width of 1 m or more.   On the aggregate Z containing carbon fibers having a weight average fiber length Lwz and a thermoplastic resin, the aggregate Y is dispersed and heated and solidified to form a layer constituting a laminate with the composite material B derived from the aggregate Z. The method according to claim 1, wherein the composite material A is manufactured.

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