JP6796935B2 - Manufacturing method of rod-shaped molded product - Google Patents

Description

The present invention relates to a method for producing a rod-shaped molded product.

Although resin bolts are advantageous in terms of weight reduction, they are not sufficient in terms of strength as compared with metal, so the strength is increased by blending a fibrous filler with resin.
When a fibrous filler is blended into a rod-shaped molded body such as a resin bolt to increase the strength, it is important that the fibers are contained in a state of being oriented in the length direction.
However, when a normal injection molding method is applied, the fibers of the surface layer portion of the rod-shaped molded product are oriented in the length direction, but the central portion is randomly present, so that the degree of orientation as a whole is low and sufficient. Cannot give strength.

Patent Documents 1 and 2 describe resin bolts in which fibers are oriented parallel to the axial direction by injection molding using a mold composed of a specific combination of a fixed mold and a movable mold, and a method for manufacturing the same. Has been done.

Japanese Unexamined Patent Publication No. 7-293534 Japanese Unexamined Patent Publication No. 7-293535

An object of the present invention is to provide a method for producing a rod-shaped molded product capable of obtaining a rod-shaped molded product having a high degree of orientation of the fibrous filler in the long axis direction.

The present invention is a method for producing a rod-shaped molded product, which comprises a step of injection molding a thermoplastic resin composition containing a fibrous filler into a mold.
The rod-shaped molded product has a circular or polygonal cross-sectional shape in the width direction, including a portion having a uniform outer diameter.
The dimensions of the rod-shaped molded product and the dimensions of the gate when the thermoplastic resin is injected into the mold satisfy the relationship of the following formulas (I) to (IV), and the fibers contained in the rod-shaped molded product. A method for producing a rod-shaped molded product, wherein the weight fiber length (Iw) is 0.5 mm or more.
8 ≦ D ≦ L (I)
1 ≦ L / D ≦ 20 (II)
S / 10 ≦ SG ≦ S (III)
D / 10 ≤ NG ≤ 4 (IV)
[The meanings of the symbols in the formula are as follows.
S: Cross-sectional area of rod-shaped molded product (mm ² )
D: Diameter (mm) when the cross-sectional shape of the rod-shaped molded body is circular, or diameter (mm) of the inscribed circle when the cross-sectional shape of the rod-shaped molded body is polygonal.
L: Length of rod-shaped molded product (mm)
SG: Total gate area (mm ² )
NG: Number of gates]

According to the production method of the present invention, it is possible to obtain a rod-shaped molded product having a high degree of orientation of the fibrous filler in the long axis direction and high bending strength.

(A) is a perspective view of a rod-shaped molded product obtained by the production method of the present invention, and (b) is a bottom view of (a). (A) is a perspective view of a rod-shaped molded product of another embodiment obtained by the production method of the present invention, and (b) is a bottom view of (a). (A) is a perspective view of a rod-shaped molded product of still another embodiment obtained by the manufacturing method of the present invention, and (b) is a bottom view of (a). (A) to (c) are plan views of the gate leading to the cavity in the mold used in the manufacturing method of the present invention. (A) is a perspective view of a long screw bolt obtained by the manufacturing method of the present invention, and (b) is a perspective view of a full screw hexagon bolt obtained by the manufacturing method of the present invention.

The rod-shaped molded body that can be manufactured by the method for producing a rod-shaped molded body of the present invention includes a portion having a uniform outer diameter, and has a cross-sectional shape in the width direction of a circle, an ellipse, a polygon, or the like. The polygon may or may not be a regular polygon.
The rod-shaped molded product may have a uniform outer diameter over the entire length direction, or may include a portion having a large outer diameter or a portion having a small outer diameter. The portion having a large outer diameter or the portion having a small outer diameter may be located at one end or both ends of the rod-shaped molded product, or may be located at an intermediate portion of the rod-shaped molded product.

<Thermoplastic resin composition containing a fibrous filler>
The thermoplastic resin composition used in the production method of the present invention contains a thermoplastic resin, a fibrous filler, and if necessary, a known additive for resin.
The thermoplastic resin is not particularly limited and can be selected according to the application, and is a polyolefin such as polyamide, polyethylene or polyprene, a polyester such as thermoplastic polyurethane (TPU) or PBT, PPS or ABS resin. It can be selected from styrene-based resins such as, and various polymer alloys.

The fibrous filler is not particularly limited and can be selected according to the application, and is selected from glass fiber, carbon fiber, inorganic fiber (excluding glass fiber), organic fiber, metal fiber and the like. be able to.
The content of the fibrous filler is preferably 10 to 60 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

Known additives include mold release agents, antistatic agents, flame retardants, colorants, plasticizers, softeners, dispersants, stabilizers (hindard phenolic antioxidants, phosphorus-based antioxidants, sulfur-based additives). Examples include antioxidants such as antioxidants, ultraviolet absorbers, heat stabilizers, etc.), antiblocking agents, crystal nucleation growth agents, fillers (granular fillers such as silica and talc), lubricants, etc. ..

The resin composition containing the fibrous filler used in the present invention preferably contains a resin-impregnated fiber bundle obtained by impregnating a bundle of fibrous filler with a thermoplastic resin and cutting it in the range of 6 to 50 mm.
The resin-impregnated fiber bundle has a length of 6 to 30 mm after bundling the fibrous filler in a state of being aligned in the length direction, impregnating the bundle of the fibrous filler with the thermoplastic resin in a molten state, and integrating them. It is preferably cut into pieces.
The length of the fibrous filler contained in the resin-impregnated fiber bundle is the same as the length of the resin-impregnated fiber bundle.
The diameter of the resin-impregnated fiber bundle is preferably in the range of 0.8 to 3 mm.

As the fibrous filler contained in the resin-impregnated fiber bundle, one having a fiber diameter (single thread diameter) of 6 to 30 μm can be used.
Since the fiber diameter varies depending on the type of fiber, the number of fibers constituting the fiber bundle can be selected according to the type of fiber.
For example, when glass fiber (fiber diameter 17 μm ) is used as the fibrous filler, 100 to 30,000 fibers are preferable, 500 to 20,000 fibers are more preferable, and 1,000 to 10,000 fibers are more preferable.
Further, for example, when carbon fibers (fiber diameter 7 μm ) are used as the fibrous filler, 1000 to 40,000 fibers are preferable, more preferably 5,000 to 35,000 fibers, and further preferably about 1,000 to 30,000 fibers.

The resin-impregnated fiber bundle can be produced by a well-known manufacturing method using a die. For example, in addition to paragraph number 7 of JP-A-6-313050 and paragraph number 23 of JP-A-2007-176227, JP-A-6-2344 (Manufacturing method and molding method of resin-coated long fiber bundle), JP-A-6-114832 (Fiber-reinforced thermoplastic resin structure and manufacturing method thereof), JP-A-6-293023 (Length) (Method for producing fiber-reinforced thermoplastic resin composition), JP-A-7-205317 (Method for taking out fiber bundles and method for producing long-fiber reinforced resin structure), JP-A-7-216104 (Method for producing long-fiber reinforced resin structure) (Method for manufacturing products), JP-A-7-251437 (Method for manufacturing long-fiber reinforced thermoplastic composite material and manufacturing equipment), JP-A-8-118490 (Method for manufacturing cross-head die and long-fiber reinforced resin structure) ) Etc. can be applied.
As the resin-impregnated fiber bundle, Plastron (registered trademark) containing various thermoplastic resins sold by Daicel Polymer Co., Ltd. and fibrous fillers such as glass fiber, carbon fiber, stainless fiber, and aramid fiber. You can also use the series.

<Manufacturing method of rod-shaped molded product>
Method for manufacturing a rod shaped molded product of the present invention uses a thermoplastic resin composition containing a fibrous filler (resin-impregnated fiber bundle above), when prepared by applying a known injection molding method, wherein The dimensions of the rod-shaped molded product and the dimensions of the gate when the thermoplastic resin is injected into the mold satisfy the relationship of the following formulas (I) to (IV).

8 ≦ D ≦ L (I)
1 ≦ L / D ≦ 20 (II)
S / 10 ≦ SG ≦ S (III)
D / 10 ≤ NG ≤ 4 (IV)
[The meanings of the symbols in the formula are as follows.
S: The cross-sectional area (mm ² ) of the rod-shaped molded body, and when the rod-shaped molded body has a uniform outer diameter, it is the cross-sectional area of the uniform outer diameter portion, and the rod-shaped molded body has a head and a thread. When is, it is the cross-sectional area of the threaded portion.
D: Diameter (mm) when the cross-sectional shape of the rod-shaped molded body is circular, or diameter (mm) of the inscribed circle when the cross-sectional shape of the rod-shaped molded body is polygonal.
L: Length of rod-shaped molded product (mm)
SG: Total gate area (mm ² )
NG: Number of gates]

S, D, and L in the above formula will be described.
The rod-shaped molded product obtained by the production method of the present invention has a uniform outer diameter as shown in FIGS. 1 to 3, and also includes a portion having a large outer diameter as shown in FIG. 5 (b). The cross-sectional shape in the width direction is circular (FIGS. 1 and 5) or polygonal (FIGS. 2 and 3).
When the cross-sectional shape in the width direction is a polygon, it is an equilateral triangle (FIG. 2), a square (FIG. 3), a regular pentagon, a regular hexagon, a regular octagon, or the like.

The rod-shaped molded body 1 shown in FIGS. 1 (a) and 1 (b) is a cylinder having a length L, and the bottom surfaces 2 and 3 are circular and have a diameter D.
The rod-shaped molded body 11 shown in FIGS. 2A and 2B is a triangular prism having a length L, the bottom surfaces 12 and 13 are equilateral triangles, and the diameter of the inscribed circle is D.
The rod-shaped molded body 21 shown in FIGS. 3A and 3B is a square pillar having a length L, the bottom surfaces 22 and 23 are regular quadrangles, and the diameter of the inscribed circle is D.

SG and NG in the above formula will be described.
FIGS. 4A to 4C show a state in which two gates 31, 32, three gates 31 to 33, and four gates 31 to 34 are provided in a portion leading to the cavity in the mold. There is.
SG is the total area of the plurality of gates.
NG is 1 to 4, and in FIG. 4, NG is 2, 3 or 4.
The shape of the gate is not particularly limited, but is preferably circular or oval, but more preferably circular.
The gates may be arranged so that the gates are spaced apart from each other.
When there are two gates as shown in FIG. 4A, it is preferable that the two circular gates 31 and 32 are arranged so that the centers of the two circular gates 31 and 32 are located on the same straight line (diameter) passing through the center O.
Further, the two circular gates 31 and 32 are preferably formed in the range of 0.1r to 0.9r when the radius from the center O is r.

As shown in FIG. 4B, when there are three gates, the lengths of the three lines connecting the center and the center O of the three circular gates are the same with the center O as the base point, and the center O and the three lines are the same. It is preferable that the lines are arranged so that the angles of the lines are the same (120-).
Further, the three circular gates 31 to 33 are preferably formed in the range of 0.1r to 0.9r when the radius from the center O is r.

As shown in FIG. 4C, when there are four gates, the lengths of the four lines connecting the centers and the centers O of the four circular gates are the same with the center O as the base point, and the four lines are the same as the center O. It is preferable that the lines are arranged so that the angles of the lines are the same (90 degrees ).
Further, the four circular gates 31 to 34 are preferably formed in the range of 0.1r to 0.9r when the radius from the center O is r.

In the production method of the present invention, if the above formulas (I) to (IV) are satisfied, the injection pressure, injection speed, holding pressure, back pressure, mold temperature, etc. at the time of injection molding include the fibrous filler. It can be carried out under the same conditions as when a known thermoplastic resin composition is used.

By applying the production method of the present invention, the degree of orientation of the fibrous filler in the length direction of the rod-shaped molded product can be increased.
Here, the "degree of orientation" is the ratio (mass%) of the fibrous filler oriented in the length direction to the fibrous filler contained in the rod-shaped molded product, and in the present invention, the orientation is described. The degree is evaluated by the bending strength of the rod-shaped molded product.
In the case of a rod-shaped molded product having the same dimensions, the greater the amount of fibrous filler oriented in the length direction, the greater the bending strength.

Further, by applying the production method of the present invention, it is possible to obtain a rod-shaped molded product having a weight fiber length (Iw) of the contained fibers of 0.5 mm or more, preferably 0.8 mm or more. When the fiber length remaining inside the rod-shaped molded body is shortened, it becomes difficult to orient the fiber in the length direction, so that the bending strength is reduced.

<Bolt manufacturing method>
By applying the method for producing a rod-shaped molded body of the present invention described above, a long screw bolt as shown in FIG. 5 (a), which partially includes a portion having a large outer diameter, is shown in FIG. 5 (b). In addition to bolts such as full-thread hexagon bolts, wood screws and the like can be manufactured.
The long screw bolt 40 shown in FIG. 5A has a thread 41 on the entire peripheral surface, and contains a fibrous filler in a state of being oriented in the long axis direction. Note that D is the diameter of the bottom surface 42.
The full-threaded hexagon bolt 45 shown in FIG. 5B has threads 46 from below the head 47 to the entire peripheral surface, and at least the inside where the threads 46 are formed is filled with fibrous material. The material is contained in a state of being oriented in the axial direction. Note that D is the diameter of the bottom surface 48.

(1) Weight fiber length (weight average fiber length)
The rod-shaped molded products obtained in Examples and Comparative Examples were measured by the following method described in paragraph No. 0063 of JP2013-121988A.
About 3 g of a sample was cut out from the rod-shaped molded product and heated at 650 ° C. to incinerate the fiber. The weight average fiber length was calculated from a part of the extracted fibers (500 fibers). As the calculation formula, [0044] and [0045] of JP-A-2006-274061 were used.

(2) Bending strength The bending strength of the rod-shaped compacts obtained in Examples and Comparative Examples was measured under the following conditions.
Measuring equipment: Autograph AG2000 (manufactured by Shimadzu Corporation)
Test speed: 2 mm / min
Distance between fulcrums: 40 mm

Example 1, Comparative Examples 1-5
In Examples 1 and Comparative Examples 1 and 2, a resin-impregnated fiber bundle (Plastron MXD-GF50-02; 2.8 mm in diameter) composed of 50% by mass of polyamide MXD6 and 50% by mass of long glass fibers as a thermoplastic resin composition. , 9 mm long columnar shape; Daicel Polymer Co., Ltd. was used.
The length of Plastron MXD-GF50-02 and the length of the glass fiber contained in it are the same.
In Comparative Examples 3 to 5, as the thermoplastic resin composition, a columnar pellet (Plastron MXD-SGF50; a cylindrical shape having a diameter of 2.0 mm and a length of 4 mm; Polymer Co., Ltd. was used.

Using each composition of Example 1 and Comparative Examples 1 to 5, injection molding was performed under the following conditions to obtain a round bar having a diameter (D) of 12 mm and a length (L) of 80 mm. The residual fiber length and bending strength of the obtained round bar were measured. The results are shown in Table 1. 〇 indicates that equations (I) to equations (IV) are satisfied, and ・ indicates that equations (I) to equations (IV) are not satisfied.
(Injection molding conditions)
Injection molding machine: J150EII of Japan Steel Works
Cylinder temperature: 280 ° C
Back pressure: 2 MPa
Mold temperature: 160 ° C

The same composition was used in Example 1 and Comparative Example 1, but since Comparative Example 1 did not satisfy the formula (III), the residual fiber length was shortened, and the difference in the residual fiber length was the degree of orientation. It is recognized that there was a difference and a difference in bending strength.
In Example 1 and Comparative Example 2, the residual fiber length was longer in Comparative Example 2, but the fact that Comparative Example 2 did not satisfy the formula (IV) resulted in a difference in the degree of orientation and a difference in bending strength. It is recognized as a thing.
In Comparative Examples 3 to 5, since short fibers are used, the residual fiber length is short and the degree of orientation is low, so that the bending strength is also low.

Example 2, Comparative Examples 6 and 7
In Examples 2 and Comparative Examples 6 and 7, a resin-impregnated fiber bundle (Plastron PAX-GF40-02; diameter 2.2 mm) composed of 60% by mass of polyamide MXD6 and 40% by mass of long carbon fibers as a thermoplastic resin composition was used. , 9 mm long cylindrical shape; Daicel Polymer Co., Ltd. was used.
The length of Plastron PAX-GF40-02 and the length of carbon fiber contained are the same.

Using each of the compositions of Example 2 and Comparative Examples 6 and 7, injection molding was performed under the following conditions to obtain a round bar having a diameter (D) of 12 mm and a length (L) of 80 mm. The residual fiber length and bending strength of the obtained round bar were measured. The results are shown in Table 2. 〇 indicates that equations (I) to equations (IV) are satisfied, and ・ indicates that equations (I) to equations (IV) are not satisfied.
(Injection molding conditions)
Injection molding machine: J150EII of Japan Steel Works
Cylinder temperature: 280 ° C
Back pressure: 2 MPa
Mold temperature: 160 ° C

The same composition was used in Example 2 and Comparative Example 6, but the residual fiber length was shortened because Comparative Example 6 did not satisfy the formula (III), and the difference in the residual fiber length was the degree of orientation. It is recognized that there was a difference and a difference in bending strength.
In Example 2 and Comparative Example 7, the residual fiber length was longer in Comparative Example 7, but the fact that Comparative Example 7 did not satisfy the formula (IV) resulted in a difference in the degree of orientation and a difference in bending strength. It is recognized as a thing.

Example 3, Comparative Examples 8 and 9
In Examples 3 and Comparative Examples 8 and 9, as a thermoplastic resin composition, a resin-impregnated fiber bundle (Plastron PPS-GF40-01; diameter 2.2 mm, length) composed of 50% by mass of PPS and 50% by mass of long glass fibers. 9 mm cylindrical shape; Daicel Polymer Co., Ltd. was used.
The length of Plastron PPS-GF40-01 and the length of carbon fiber contained are the same.

Using each of the compositions of Example 3 and Comparative Examples 8 and 9, injection molding was performed under the following conditions to obtain a round bar having a diameter (D) of 12 mm and a length (L) of 80 mm. The residual fiber length and bending strength of the obtained round bar were measured. The results are shown in Table 3. 〇 indicates that equations (I) to equations (IV) are satisfied, and ・ indicates that equations (I) to equations (IV) are not satisfied.
(Injection molding conditions)
Injection molding machine: J150EII of Japan Steel Works
Cylinder temperature: 320 ° C
Back pressure: 2 MPa
Mold temperature: 170 ℃

The same composition was used in Example 3 and Comparative Example 8, but the residual fiber length was shortened because Comparative Example 8 did not satisfy the formula (III), and the difference in the residual fiber length was the degree of orientation. It is recognized that there was a difference and a difference in bending strength.
In Example 3 and Comparative Example 9, the residual fiber length was longer in Comparative Example 9, but the fact that Comparative Example 9 did not satisfy the formula (IV) resulted in a difference in the degree of orientation and a difference in bending strength. It is recognized as a thing.

The rod-shaped molded product obtained by the method for producing a rod-shaped molded product of the present invention can be used as bolts such as various pins, various wood screws (counterhead or round head), long screw bolts, hexagon bolts, and full screw hexagon bolts. it can.

1,11,21 Rod-shaped molded body 31,32 Gate 40,45 Bolt

Claims (4)

A method for producing a rod-shaped molded product, which comprises a step of injection molding a thermoplastic resin composition containing a fibrous filler into a mold.
The thermoplastic resin composition containing the fibrous filler contains a resin-impregnated fiber bundle obtained by cutting a bundle of fibrous filler impregnated with resin in the range of 6 to 30 mm.
The rod-shaped molded product has a circular or polygonal cross-sectional shape in the width direction, including a portion having a uniform outer diameter.
A method for producing a rod-shaped molded product, wherein the dimensions of the rod-shaped molded product and the dimensions of the gate when injecting the thermoplastic resin into the mold satisfy the relationship of the following formulas (I) to (IV).
8 ≦ D ≦ L (I)
1 ≦ L / D ≦ 20 (II)
S / 10 ≦ SG ≦ S (III)
D / 10 ≤ NG ≤ 4 (IV)
[The meanings of the symbols in the formula are as follows.
S: The cross-sectional area (mm ² ) of the rod-shaped molded body, and when the rod-shaped molded body has a uniform outer diameter, it is the cross-sectional area of the uniform outer diameter portion, and the rod-shaped molded body has a head and a thread. When is, it is the cross-sectional area of the threaded portion.
D: Diameter (mm) when the cross-sectional shape of the rod-shaped molded body is circular, or diameter (mm) of the inscribed circle when the cross-sectional shape of the rod-shaped molded body is polygonal.
L: Length of rod-shaped molded product (mm)
SG: Total gate area (mm ² )
NG: Number of gates] The thermoplastic resin is selected from polyamide, polyolefin, thermoplastic polyurethane (TPU), polyester, PPS, and styrene resin, and the fibrous filler is glass fiber, carbon fiber, organic fiber, metal fiber, or inorganic. The method for producing a rod-shaped molded product according to claim 1, which is selected from fibers (excluding glass fibers). The method for producing a rod-shaped molded product according to claim 1 or 2, wherein the weight average fiber length of the fibers contained in the rod-shaped molded product is 0.8 mm or more. The method for producing a rod-shaped molded product according to any one of claims 1 to 3, wherein the rod-shaped molded product has a circular cross section in the width direction and has a thread on the peripheral surface.

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