Method for manufacturing fiber reinforced elastic sheet, apparatus for manufacturing the same and mold to be used

Abstract: A method for manufacturing a fiber reinforced elastic sheet by extruding and processing an elastomer containing staples by 25 volume % or less. The elastomer, which uniformly flows in a sheet width direction, passes through a slight clearance (6a) of a molding dice in the vertical direction of the sheet, and then the elastomer flow is enlarged in the vertical direction of the sheet. A flow adjustment portion (7) is provided in a passage of the elastomer to flow uniformly in the sheet width direction, and a weir portion (9) is provided on the downstream side of the flow adjustment portion. A clearance Wo of an outlet in the vertical direction of the sheet, a clearance Wi formed by the weir portion in the vertical direction of the sheet and a distance ℓ between the weir portion and the outlet have the relationship of Wo / Wi ≧ 2 ℓ ≧ 3Wo 0.3 mm ≦ Wi ≦ 5 mm.

Description: The invention relates to a method for manufacturing a fiber reinforced elastic elastomer according to the preamble of claim 1 and to an apparatus according to the preamble of claim 2. US-A-4,057,610 discloses a hose reinforced with discontinuous fibers oriented in the radial direction and a method for preparing such a hose by extrusion, wherein a hollow cylindrical die is used in which a mandrel is arranged. One embodiment of the known die is provided with a mandrel in the hollow-cylindrical die, wherein a weir is provided in the ring channel of the die. According to another embodiment, the ring channel of the die is enlarged in such a way that the diameter of the mandrel is reduced and in the same way the diameter of the hollow-cylindrical die is enlarged. It is an object of the present invention to easily manufacture a fiber-reinforced elastic hose in which staples or discontinuous fibers, respectively, are oriented in the circumferential direction. This object is achieved by the features in the characterising part of claim 1 and of claim 2. The cylindrical staple complex elastomer extruded from the ring groove of the expansion die is unpressurized and is gradually extended circumferentially, so that the staples of the staple complex elastomer are circumferentially oriented, while being extruded through the ring groove of the expansion die. Consequently no shrinkage is caused, so that the circumferential orientation coefficient can be increased. The invention is described in more detail in connection with the drawing, wherein the single figure shows a section view of an expansion die. Indicated at 41 is an enlargement adaptor which is connected to an expansion die 31. The enlargement adaptor 41 is formed such that a cylindrical staple complex elastomer E extruded from the expansion die 31 flows along an outer peripheral surface 41a. The cylindrical staple complex elastomer E is further extended circumferentially by the enlargement adaptor 41. The outer peripheral surface 41a of the enlargement adaptor 41 has a diameter increased with a suitable slope coaxially with a ring groove 32 of the expansion die 31. The staple complex elastomer E is circumferentially extended by the enlargement adaptor 41, so that the circumferential staple orientation coefficient of the staple complex elastomer E is further increased as compared with the case where only the expansion die 31 is utilized. The outer peripheral surface 41a of the enlargement adaptor 41 has almost the same diameter as the inner diameter of the outlet of the ring groove 32 of the expansion die 31, and is coaxial with the ring groove 32 of the expansion die 31. The enlargement adaptor 41 has a taper portion 41A and a constant diameter portion 41B. The taper portion 41A is linearly slanted in the direction in which the diameter is gradually increased. The constant diameter portion 41B has the same diameter as the maximum outer diameter of the taper portion 41A and is continuously provided on the taper portion 41A. The enlargement adaptor 41 may have any structure in which the staple complex elastomer E is gradually extended circumferentially. In Fig. 13, when a maximum diameter D and an axial length L of the enlargement adaptor 41 are increased, the cylindrical staple complex elastomer E may circumferentially be shrunk so as not to be extruded. Accordingly, it is necessary to determine the maximum diameter D and axial length L of the enlargement adaptor 41 depending on the rubber compound of the staples, the temperature at the time of extrusion, viscosity, the thickness of the cylindrical staple complex elastomer E, extruding speed and the like. With the above-mentioned structure, the staple orientation is carried out in the following two stops so that the staple complex elastomer is molded. (1) First step The fiber orientation coefficient in the circumferential direction (in the direction of Y) is set to 80 to 85 % by the expansion die 31. The cylindrical staple complex elastomer E exits from the extruder and is shaped to have a cross section corresponding to the outlet of the extruder. Then, the cylindrical staple complex elastomer E enters the ring groove 32 of the expansion die 31 through an inlet 32A (sectional area : mi) of the expansion die 31, and thereafter flows circumferentially toward an outlet 32B (sectional area : mo). Accordingly, the staples of the staple complex elastomer E are gradually extended circumferentially according to the relationship of mo > mi even if they are oriented in any direction at the inlet 32A. However, the orientation is disturbed owing to the flow resistance of the expansion die 31, or the elastomer does not flow uniformly in the passage. Consequently, the staples are not completely oriented circumferentially. The cylindrical staple complex elastomer E is circumferentially shrunk by about 2 to 2.5 % on the basis of (the diameter of the inner die 31B of the expansion die 31 + sheet thickness) x 2π. Consequently, the circumferential orientation of the staples is disturbed. Immediately after a cylinder is extruded from the outlet, the die is swelled owing to the residual stress which is caused by the internal pressure and temperature during extrusion. Thus, the cylinder tends to be circumferentially shrunk so that the orientation is disturbed. As a result. Ro / Ri reaches the limit of 7.0. If Ro / Ri is smaller than 7.0, there appear orientation components other than the circumferential direction. If Ro / Ri = 7.0, the orientation coefficients are as follows. X direction : 10 to 15 % Y direction : 80 to 85 % Z direction : 5 to 10 % (2) The orientation coefficient increased by the enlargement adaptor 41 The cylindrical staple complex elastomer E, which is extruded with the staples oriented circumferentially, is further extended circumferentially (in the direction of Y) by the enlargement adaptor 41 so as to improve the circumferential orientation. The orientation coefficient is changed depending on an extension coefficient as shown in Table 3. Extension coefficient Orientation coefficient X direction Y direction Z direction 0 % 10 to 15 % 80 to 85 % 5 to 10 % 1.0 9 to 12 83 to 87 4 to 5 2.5 2 to 3 90 to 92 2 to 3 5.0 1 to 2 93 to 99 1 to 2 The staple complex elastomer E is gradually enlarged by the enlargement adaptor 41. Consequently, the circumferential shrinkage is successively removed. In the case where the staple complex elastomer E is extruded at an extension coefficient of, for example, 2.5 %, it is circumferentially shrunk when existing from the expansion die 31. As a result, there can be formed the cylindrical staple complex elastomer E having no shrinkage. Thus, the circumferential staple orientation coefficient can be improved by combining the expansion die 31 and the enlargement adaptor 41. Consequently, there can be obtained the same effect as in a well-known calendering method. By way of example, the staple complex elastomer E can fully function as the bottom rubber of a transmission belt. There will be described tests for the ratio of the axial length L to the maximum diameter D of the enlargement adaptor 41. 〈〈 Staple complex rubber compound used for extrusion 〉〉 chloroprene rubber 100 part by weight FEF carbon 40 S. A. 1 MgO 5 ZnO 5 age resistor 3 nylon staple (3 mm) 10 cellulose fiber 10 Total 174 part by weight 〈〈 Extruder used for tests 〉〉 L / D = 12, D = 90 mm 〈〈 Enlargement adaptor 〉〉 Expansion die : the outer diameter of an inner die is 200 mm. The thickness of the extruded rubber sheet is 3.0 to 5.5 mm. 〈〈 Extension coefficient, L / D of the enlargement adaptor and extruding behavior of the staple complex rubber 〉〉 Extension coefficient L/D Sheet thickness Extruding behavior 0 % 70/200 3.0 mm L≧70, failure 1.25 55/202.5 3.0 L≧60, failure 5.5 L≧65, failure 2.5 50/205 3.0 L≧50, failure 5.5 L≧55, failure 5.0 50/210 3.0 L≧45, failure 5.5 L≧50, failure 40/215 - failure Examples of the thermoplastic material are a thermoplastic resin such as polyvinyl chloride or polyethylene, a thermoplastic elastomer such as olefine, ester, ether, amide or urethane, crosslinking rubber such as natural rubber, stylene-butadien rubber or chloroprene rubber, and their compounds. Examples of the staple are a natural fiber such as cotton, wool or pulp, a synthetic fiber such as polyester, nylon or aramide, a semisynthetic fiber such as rayon, an inorganic fiber such as ceramic, and a metallic fiber. If fiber capacity exceeds 40 volume %, the friction coefficient between the staples and molding passage wall is decreased and fluidity is lowered. Consequently, the staple orientation is blocked in the length direction of the sheet surface layer so that the orientation is lowered. It is desired that the staple length is half of the sheet thickness or less.

Claims: A method for manufacturing a fiber reinforced elastic elastomer wherein a staple complex elastomer (E) mixed with staples is circumferentially extended and extruded through a ring groove (32) of an expansion die (31) so as to circumferentially orient the staples, the expansion die (31) having an inner peripheral surface, an outer peripheral surface and the ring groove (32) which is provided between the inner and outer peripheral surfaces and is substantially filled with the staple complex elastomer (E), characterized in that the inner peripheral surface of the expansion die (31) is extended by an outer peripheral surface of an enlargement adaptor (41), which has a larger diameter than the ring groove (32), whereby the cylindrical staple complex elastomer (E) extruded from the ring groove (32) of the expansion die (31) is unpressurized and is gradually extended circumferentially. An apparatus for manufacturing a fiber reinforced elastic elastomer wherein a staple complex elastomer (E) mixed with staples is circumferentially extended and extruded through a ring groove (32) of an expansion die (31) so as to circumferentially orient the staples, the expansion die (31) having an inner peripheral surface, an outer peripheral surface and the ring groove (32) which is provided between the inner and outer peripheral surfaces and is substantially filled with the staple complex elastomer (E), characterized in that an enlargement adaptor (41) is connected to the outlet side of the expansion die (31), the enlargement adaptor being coaxial with the ring groove (32), wherein the outer peripheral surface of the enlargement adaptor (41) has a diameter which is increasing with a suitable slope starting from the inner diameter of the ring groove (32). Apparatus according to claim 2, wherein the enlargement adaptor (41) has a taper portion (41A) followed by a constant diameter portion (41B). Apparatus according to claim 3, wherein the constant diameter portion (41B) has the same diameter as the maximum outer diameter of the taper portion (41A).

Inventors: SHIOYAMA TSUTOMU, TAJIMA YOSHITAKA, UMEDA ARAO, SHIOYAMA, TSUTOMU,, TAJIMA, YOSHITAKA,, UMEDA, ARAO, UMEDA, ARAO,
Applicants: BANDO CHEMICAL IND, BANDO CHEMICAL INDUSTRIES, LIMITED
Application year: 1991
Main classification: B29C47
IPC codes: B29C47