JPH0673894B2 - Method for producing oriented fiber reinforced elastic sheet and its forming die - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an oriented fiber-reinforced elastic sheet and a molding die therefor.

(Prior Art) Generally, a sheet material in which short fibers are oriented in the thickness direction is
It is known that it is excellent in elastic properties as a vibration isolator, surface friction properties and friction resistance properties as a sliding material. Therefore, it is desired to develop a method for easily producing a sheet material in which short fibers are oriented in the thickness direction.

As a method of orienting short fibers in the sheet thickness direction, for example, as described in JP-B-58-29231, a composite of an extrudable polymer and discontinuous fibers, a surface of the central mandrel and an outer die. Has a channel of curved cross section formed between the surface of the member and Ao / A
i is about 2 or 2 and Wo / Wi / Ro / Ri is 2 or 2 or more (where Ao is the area of the channel outlet, Ai is the area of the channel inlet, Wo is the width of the channel at the outlet, Wi Is the width of the channel at the inlet, Ro is the average radius of the channel outlet, and Ri is the average radius of the channel inlet.) The radial component of fiber orientation exceeds the circumferential component of fiber orientation by extrusion through a die. It is known that an extruded hose is formed, and it is conceivable that the hose produced by the method is cut open to form a sheet.

Further, as described in, for example, JP-A-60-219034, a sheet in which short fiber groups are oriented and embedded in the elastic sheet in the sheet longitudinal direction is cut in the sheet width direction in a direction perpendicular to the sheet surface. There is also known a method for producing a sheet by forming a band-shaped small piece group, arranging cut surfaces of the band-shaped small pieces on both upper and lower surfaces, and joining side surfaces of adjacent band-shaped small pieces.

(Problems to be Solved by the Invention) However, when the former hose is cut open to manufacture a sheet, a step of cutting the hose into a sheet shape is required, and since the diameter of the hose is limited, You can't get a wide sheet. In addition, when the hose is cut open into a sheet shape, the orientation of the short fibers is disturbed due to the difference in inner and outer circumferences of the hose, and a sheet having a stable elastic modulus (spring constant) cannot be obtained.

Further, in the latter, in order to increase the degree of orientation of the short fibers, the elastic sheet in which the short fiber group is oriented and embedded in the longitudinal direction of the sheet needs to have a thickness of about 0.6 to 1 mm. The work of cutting the sheets to form small strips and joining them is extremely troublesome and cannot be mass-produced.

It is an object of the present invention to provide a method for producing an oriented fiber-reinforced elastic sheet and a forming die thereof, which can easily produce an oriented fiber-reinforced elastic sheet in which short fibers are oriented in the sheet thickness direction. It is a thing.

(Means for Solving the Problem) The invention of claim (1) is a method for producing an oriented fiber-reinforced elastic sheet, comprising extruding an elastomer containing 25% by volume or less of short fibers to form an oriented fiber-reinforced elastic sheet. In the method, the triangle-shaped flow rate adjusting section disposed upstream of the flow path of the elastomer makes the flow of the elastomer uniform in the width direction, and then by the weir section disposed downstream of the flow rate adjusting section, The flow of elastomer is squeezed into a thin strip in the thickness direction, and then the elastomer flow is released and extruded through an outlet opening that is large in a rectangular shape to orient short fibers in the thickness direction. The configuration.

The invention according to claim (2) is a molding die for a distributed fiber-reinforced elastic sheet, which is used for molding an oriented fiber-reinforced elastic sheet by extruding an elastomer containing 25% by volume or less of short fibers, A flow rate adjusting section is provided in the passage through which the elastomer flows so that the elastomer flows uniformly in the width direction, and a weir section is provided downstream of the flow rate adjusting section. It is characterized in that the relationship of Wo / Wi ≧ 2 l ≧ 3 Wo 0.3 mm ≦ Wi ≦ 5 mm is established between the vertical gap Wi formed by the portion and the distance l from the dam portion to the outlet.

(Operation) According to the invention of claim (1), by the triangular island-shaped flow rate adjusting unit arranged on the upstream side of the flow path through which the elastomer flows,
The flow of the elastomer becomes uniform in the width direction, and then the weir portion arranged downstream of the flow rate adjusting unit narrows the flow of the elastomer in the thickness direction so as to form a thin band. At this time, a shearing force acts on the elastomer passing through the weir, and the short fibers mixed with the elastomer are oriented in the flow direction. After that, the flow of the elastomer is extruded through the outlet opening that is largely opened in a rectangular shape,
The short fibers are oriented in the thickness direction. Through this exit,
When a thin elastomer in which the short fibers are oriented in the flow direction is extruded, the flow of the elastomer expands and changes in the vertical direction, and the short fibers mixed with the elastomer are also oriented in the vertical direction.

According to the invention of claim (2), the elastomer flowing uniformly in the width direction through the flow rate adjusting portion is subjected to a shearing force when passing through the dam portion, and the short fibers mixed with the elastomer flow. Oriented in the direction. When the thin elastomer in which the short fibers are oriented in the flow direction passes through the weir, the flow of the elastomer changes to a vertical flow, and the short fibers mixed with the elastomer are also oriented in the thickness direction.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 to 3 showing a molding die for an oriented fiber reinforced elastic sheet, 1 is a molding die attached to the tip of a well-known extruder, and includes an upper member 2, a lower member 3, and left and right lateral members. The rubber flow path 6 having the substantially rectangular cross-section formed by them has an enlarged sloped portion 6a whose cross-sectional area gradually expands in the lateral direction and a downstream side of the enlarged sloped portion 6a. And has an opening 6b having a maximum cross-sectional area and having a large rectangular opening.

The lower member 3 is provided with a triangular island-shaped rubber flow adjusting portion 7 that protrudes upward and uniformly expands the rubber flow in the left-right direction (width direction) at a portion corresponding to the enlarged slope portion 6a of the rubber flow path 6. It is set up.

In the upper member 2 corresponding to the opening 6b of the rubber flow path 6 downstream of the rubber flow adjusting unit 7, a weir is formed between the lower member 3 and the lower member 3 so as to form a uniform rectangular rectangular gap 8 in the left-right direction. The portion 9 is provided so as to project downward, and the dam portion 9 narrows the rubber flow in the vertical direction (thickness direction) so as to form a thin band.

Vertical flow of the gap 8 formed by the weir portion 9
Wi and the vertical flow Wo of the gap between the opening 6b of the rubber flow path 6
And the ratio is 2 or more, that is, Wo / Wi ≧ 2, and the vertical length of the gap 8 formed by the weir portion 9
Wi should be in the range of 0.3 to 5 mm, that is, 0.3 mm ≦ Wi ≦ 5 mm, preferably 0.5 to 1 mm. The vertical length Wi of the gap 8 formed by the weir 9 is 0.3.
The reason why the range is up to 5 mm is that if it is shorter than 0.3 mm, not only the extrusion pressure rises unnecessarily, but also rubber clogging occurs, and if it is longer than 5 mm, it will be in the vertical direction (sheet thickness direction). This is because the degree of orientation of the short fibers is reduced.

In addition, the distance l from the weir 9 to the opening end of the opening 6b
Is required to be at least 3 times the vertical length Wo of the gap of the opening 6b, that is, l ≧ 3 Wo, preferably 5 to 10 times. this is,
If it is not more than 3 times, a sheet having a stable thickness cannot be obtained, and if it exceeds 10 times, the short fibers oriented in the sheet flow direction increase due to the orientation tendency of the short fibers on the sheet surface. Because.

Further, the shape of the weir portion 9 is not particularly specified, but the upstream side surface 9a is an inclined surface so that the pressure loss is small, and the downstream side surface 9b is most efficiently arranged in the vertical direction (sheet thickness direction). Tilt angle θ to
It is desirable that the angle is 20 ° to 25 °.

According to the evaluation by the swelling method with toluene,
As shown in the figure, it is understood that the orientation rate Hz of the short fibers in the sheet thickness direction has a peak value when the inclination angle θ is 25 ° or less.

According to the above-mentioned structure, the rubber flow passes through the rubber flow adjusting portion 7 in the inclined widening portion 6a of the rubber flow passage 6 and uniformly spreads in the left-right direction, and reaches the opening 6b. The weir 9 causes a shearing force to act on the rubber flow that has spread evenly in the left-right direction, and the short fibers mixed in the rubber material are oriented in the rubber flow direction.

Then, when the rubber material having the short thickness in the vertical direction in which the short fibers are oriented in the rubber flow direction completely passes through the dam portion 9, the cross-sectional area of the rubber flow path 6 is expanded, and the length in the vertical direction is long. Therefore, the rubber flow changes in the vertical direction (thickness direction), and the short fibers mixed in the rubber are also oriented in the vertical direction (thickness direction) due to the change in the flow.

At this time, the distance l from the weir 9 to the opening end of the opening 6b is
By setting it to 3 Wo or more, a back pressure that changes the rubber flow in the vertical direction by passing through the weir 9 is applied by the frictional force between the wall surface of the rubber flow path 6 and the rubber material.

As the elastomer constituting the rubber material, natural rubber, styrene butadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, crosslinked elastomers such as urethane rubber and polyolefin-based, polyester-based, polyether-based, polyamide-based, It is appropriately selected from thermoplastic elastomers such as polyurethane. Further, a reinforcing agent, a filler, a softening agent, a crosslinking agent, a crosslinking accelerator, a crosslinking acceleration aid, an antiaging agent,
A general elastomer compounding / additive such as a tackifier, an antistatic agent and a kneading adhesive can be arbitrarily selected.

If the mixing amount of the above short fibers exceeds 25% by volume, molding by extrusion becomes difficult, so it is necessary to be 25% by volume or less, and as the short fibers, aliphatic polyamide, aromatic polyamide, polyester, Acrylic, acetylated polyvinyl alcohol, men, silk, wool, pulp, synthetic fibers such as rayon, natural fibers and semi-synthetic fibers, and steel,
It is appropriately selected from metal fibers such as stainless steel and copper. Also, if necessary, the surface of the short fibers may be epoxy,
Adhesion treatment is performed with isocyanate, rezocine formalin latex (RFL), chlorinated rubber adhesive, etc.

The shape of the short fibers is arbitrary, but if the fiber length / fiber diameter ratio (L / D) is too large, it is difficult to disperse the fibers in the rubber material. The effect on application is reduced. From this point, it is desirable to use L / D between 10 and 1000 and fiber length of 50 mm or less.

Subsequently, a specific example will be described.

Well-known rubber compounds were mixed by a closed kneader, and nylon 66 fibers cut into a length of 3 mm by a roll were mixed by 15% by volume. The mixture was rolled with a roll and then formed into a ribbon shape.

A molding die having a size structure of Wi = 0.5 mm, Wo = 5 mm, and 1 = 40 mm is used, and a rubber flow adjusting section is arranged upstream of the dam section. This forming die was attached to an extruder head, and after preheating with the extruder to a predetermined temperature, the above mixture was supplied to form a sheet.

After the sheet thus obtained was vulcanized by press vulcanization, the vulcanized product was immersed in a solvent (toluene), and the linear expansion coefficient in each direction of the three-dimensional axis when equilibrium swelling was measured. . Then, when the orientation rate of the short fibers in the sheet thickness direction was calculated by the following formula, it was 67.3%.

The orientation rate Hz in the sheet thickness direction was calculated by the following formula.

Hz-{(1 / Vz) / (1 / Vx + 1 / Vy + 1 / Vz)} × 100 where Hz: orientation ratio of short fibers in the sheet thickness direction Vx, Vy, Vz: solvent linear expansion in the three-dimensional axial directions Furthermore, the upper and lower surface layers 0.5 mm of the vulcanized sheet were removed by buffing, and as a result of obtaining the orientation ratio in the sheet thickness direction in the same manner as described above, it was confirmed that it was 80.5%. Was done. Therefore, the upper and lower surface layers of the sheet have a large fiber orientation component in the rubber flow direction. By removing the upper and lower surface layers having a large fiber orientation component in the rubber flow direction, the sheet inner layer excluding the upper and lower surface layers is removed. It was confirmed that the short fibers were oriented in the sheet thickness direction with a high orientation rate.

When the sheet manufactured in this manner is used as a vibration isolator, depending on the application, it can often be used with the surface layer held.

In addition, since the elastic properties of the sheet inner layer portion, in which the short fibers are oriented in the thickness direction and has many components, have different elastic properties between the thickness direction and the other directions as described above, it is possible to use them to compress and shear. It is possible to manufacture vibration-damping materials having different damping characteristics of (3) without incorporating a shape factor.

Further, since short fibers are evenly projected on the surface where the upper and lower surface layers of the sheet are removed by buffing, the coefficient of friction can be controlled by the blending amount of the short fibers and the abrasion resistance can be greatly improved. Therefore, it can be used as a sliding material, particularly as a sliding material such as a frictional force imparting mechanism such as a brake, a clutch, a torque limiter, and a lever operating force adjusting mechanism.

Furthermore, by winding the above-mentioned sheet around the shaft member to be the shaft core to form a roll, vulcanizing it, and then buffing the roll outer peripheral surface uniformly, short fibers are compressed elastically in the radial direction. Since it is possible to manufacture a high roll and reduce the friction coefficient of the roll surface, it is possible to reduce the deviation of the belt by using the roll as a driven roll for driving the belt. It is also possible to produce rolls with very improved wear resistance.

Therefore, in the sheet thickness direction, it is possible to produce a sheet in which most of the mixed short fibers are oriented, using the molding die described above, simply by passing an elastomer containing short fibers, The manufacturing process is simplified and is very suitable for mass production. Similarly, since the processing man-hours can be greatly reduced, the above-mentioned sheet can be manufactured at low cost, and since the molding die can continuously produce the product, it is possible to produce a product with stable quality and improved reliability. it can.

(Effect of the Invention) As described above, in the invention of claim (1), the flow of the elastomer in which the short fibers are mixed is passed through the thin gap in the vertical direction, and then the flow of the elastomer is expanded in the vertical direction. By doing so, the short fibers oriented in the flow direction due to the gap become oriented in the vertical direction due to expansion, and it is possible to manufacture a sheet in which the short fibers are oriented in the thickness direction.

According to the invention of claim (2), as described above, the sheet in which the short fibers are oriented in the vertical direction can be formed only by passing the flow of the elastomer mixed with the short fibers through the passage.

[Brief description of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a front view of a forming die, Fig. 2 is a longitudinal sectional view of the same, Fig. 3 is a transverse sectional view of the same, and Fig. 4 is an explanatory view of an inclination angle of a weir. FIG. 5 is a diagram showing the relationship between the inclination angle of the weir and the orientation rate in the sheet thickness direction. 1 ... Molding die 5 ... Rubber flow adjusting part (flow rate adjusting part) 6 ... Rubber flow path (passage) 6b ... Opening part (outlet part) 8 ... Gap 9 ... Weir part

Claims (2)

[Claims] 1. A method for producing an oriented fiber-reinforced elastic sheet, comprising extruding an elastomer containing 25% by volume or less of short fibers to form an oriented fiber-reinforced elastic sheet. A triangular island-shaped flow rate adjustment unit is provided to make the elastomer flow uniform in the width direction, and then a weir section disposed downstream of the flow rate adjustment unit adjusts the elastomer flow to a thin strip shape in the thickness direction. In the production of an oriented fiber-reinforced elastic sheet, which is characterized in that short fibers are oriented in the thickness direction by squeezing in and then extruding by releasing the flow of an elastomer through an outlet portion which is largely opened in a rectangular shape. Method. 2. A molding die for an oriented fiber reinforced elastic sheet, which is used for forming an oriented fiber reinforced elastic sheet by extruding an elastomer containing 25% by volume or less of short fibers, wherein a passage through which the elastomer flows. Is provided with a flow rate adjusting section for allowing the elastomer flow to flow uniformly in the width direction, a weir section is provided downstream of the flow rate adjusting section, and is formed by the vertical gap Wo of the outlet and the weir section. Vertical gap
A molding die for an oriented fiber-reinforced elastic sheet, characterized in that the relationship Wo / Wi ≧ 2 l ≧ 3 Wo 0.3 mm ≦ Wi ≦ 5 mm is established between Wi and the distance l from the weir to the outlet.