JP2004202982A - Method for manufacturing transmission belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a transmission belt in which a tubular molded article having no weld line wherein a short fiber is oriented to the peripheral direction is prepared by extrusion, this article is cut into a wide sheet and then the wide sheet is applyed to a pressed rubber sheet. <P>SOLUTION: The method for manufacturing a transmission belt comprises the following processes: (1) a rubber 15 containing a short fiber is kneaded by an extruding screw and moved without preventing the fluidization and without changing the flowing direction to pass through a rubber path way 18 in a circular expansion die 5, whereby a tubular molded article 10 having no weld line wherein a short fiber is oriented to the peripheral direction is molded by extrusion, (2) the tubular molded article 10 is cut open along the extrusion direction to form a rubber sheet 22 wherein the short fiber is oriented in a width direction, and this rubber sheet 22 is cut along the longitudinal direction by a predetermined length to form a pressed rubber sheet 54 and (3) a molded belt 55 is manufactured in a mold 50, after vulcanization and grinding, to finish a belt sleeve having rib parts. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a power transmission belt, and more specifically, extrudes a tubular molded body having no weld line in which short fibers are circumferentially oriented while passing through a rubber passage of an expansion die, and cuts out the molded body. The present invention relates to a method of manufacturing a power transmission belt in which a wide sheet is applied to a compressed rubber sheet.
[0002]
[Prior art]
Conventionally, as a method of orienting the short fibers in a certain direction in the unvulcanized rubber, the unvulcanized rubber containing the short fibers is put into a pair of calender rolls having different rotation speeds in a rolled sheet manufacturing step, and the rolled sheet is rolled. The short fibers in the rubber sheet were oriented in the rolling direction of the sheet and cut according to the belt width to be formed. After that, several rolled sheets cut in the laminating step are stacked and laminated to a predetermined thickness, and then, in the winding step, the laminate in which short fibers are oriented in the width direction is wound around a forming drum and used for manufacturing a power transmission belt. I was
[0003]
That is, in a method of manufacturing a V-ribbed belt or a low-edge V-belt transmission belt, one or more sheets of cover canvas and an adhesive rubber layer are wound around the peripheral surface of a cylindrical forming drum, and a cord made of a cord is placed thereon. Was spirally spun, and a compressed rubber layer was sequentially wound thereon to obtain a laminate, which was then vulcanized to form a belt sleeve. The compression rubber layer used here had a thickness of three to four sheets laminated together, and the short fibers oriented in the sheet width direction were wound around a molding drum.
[0004]
However, if the thickness of the rolled sheet is not reduced, the short fibers cannot be sufficiently oriented in the sheet rolling direction. Was.
[0005]
As a method of improving this, it has been proposed to use a sheet made of a short fiber-containing rubber composition by an expansion die for a power transmission belt. For example, Patent Document 1 discloses an expansion having a V-rib portion forming groove. A cylindrical rib rubber tube is extruded by an extruder provided with a die at an outlet portion, a V-ribbed belt molded body is molded on a die using a sheet obtained by cutting the rib rubber tube, vulcanized, and the V-rib of the belt molded body is vulcanized. It is disclosed that a rib surface of a portion is ground to produce a V-ribbed belt.
[0006]
[Patent Document 1]
JP-A-8-74936
[Problems to be solved by the invention]
However, even in the method using a conventional expansion die, for example, when using a material having a strong adhesiveness such as chloroprene and a high shear stress, the surface layer, particularly the outer peripheral layer, is large between the die inner peripheral surface and the die. The surface of the rubber surface became rough because frictional force was generated and it did not flow smoothly. For this reason, the adhesion between the matrix rubber and the fibers is poor, and the orientation is also poor. In practice, it has sometimes been difficult to use the matrix for the compressed rubber layer of the power transmission belt. Further, in order to extrude the short-fiber-containing rubber composition by molding an accurate V-rib portion with an expansion die, it was necessary to improve the compounding.
[0008]
In addition, the expansion die is composed of an outer die, an inner die, and a center block, and has a structure in which these members are mechanically fixed to a spider shaft attached to the extruder, so that the flow of rubber is hindered by the spider shaft. In addition, it has been difficult to increase the discharge amount of the cylindrical molded body by reducing the internal pressure. Moreover, the flowing rubber in the two rubber passages was wound around the spider shaft near the entrance of the die and abutted, and a weld line was generated at this portion. That is, it becomes a region where the short fiber-mixed rubber plastically flows in the clockwise direction and the counterclockwise direction or a region where the rubber hardly flows, the short fibers are randomly oriented, the orientation is poor, and the thickness is thinner than other regions. In other words, the area was defective in quality.
[0009]
The present invention pays attention to such a problem, and as a result of diligent research, extruded a cylindrical molded body without weld lines in which short fibers are oriented in the circumferential direction, and applied a wide sheet cut into a compressed rubber sheet. It is an object of the present invention to provide a method for manufacturing a transmission belt.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 of the present application is directed to a power transmission belt having a rubber layer in which a core wire is embedded along the belt longitudinal direction, and a rib portion extending in the belt longitudinal direction adjacent to the rubber layer. In the manufacturing method of
A weld in which the short fiber mixed rubber kneaded by the extrusion screw is moved without obstructing the flow and without changing the flow direction, and the short fibers are circumferentially oriented while passing through the rubber passage of the annular expansion die. Extrusion molding into a cylindrical molded body without lines,
After cutting the cylindrical molded body along the extrusion direction into a single rubber sheet with the short fibers oriented in the width direction, the rubber sheet is cut by a predetermined length along the length direction and compressed. Into a rubber sheet,
A method for manufacturing a power transmission belt, comprising forming a belt molded body by winding at least a core wire and the above-mentioned compressed rubber sheet around a molding mold, vulcanizing the resultant, and then finishing the belt sleeve having a rib portion by polishing.
[0011]
In this production method, the short fiber-mixed rubber kneaded by the extrusion screw moves in the cylinder without flow inhibition and without changing the flow direction, so that no weld line is generated in the cylindrical molded body, Therefore, the entire width of the cut sheet can be used for the compressed rubber sheet of the power transmission belt, so that a low-cost method of manufacturing a power transmission belt is provided.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the present invention, one rubber sheet in which short fibers are oriented in the width direction is first produced. Examples of the method include an extrusion method and a calendering rolling method. Here, the extrusion method will be described. In this extrusion method, 10 to 40 parts by mass of short fibers are previously added to 100 parts by mass of a polymer by an open roll and kneaded, and then the kneaded masterbatch is once released, and cooled to 20 to 50 ° C. Prevent rubber scorch.
[0013]
When 1 to 10 parts by mass of a softening agent is added, the short fibers and the rubber are well blended, and not only the dispersion in the rubber is improved, but also the short fibers themselves are prevented from becoming entangled and becoming floc. In other words, the softener penetrates into the short fibers and acts as a lubricant to loosen the entanglement of the elementary fibers, prevents the short fibers from becoming cotton-like, and reduces the familiarity between the short fibers and the rubber. It improves and the dispersion of short fibers improves.
Subsequently, as shown in a schematic diagram of an apparatus for extruding a rubber sheet containing short fibers in FIG. 1, the master batch is kneaded in a state where the temperature is usually adjusted to 40 to 100 ° C. by an extrusion screw 4 of a cylinder 3 in an extruder 2. After that, the short fiber-mixed rubber 15 is located at a position facing the cylinder 4 and is located on the same central axis. The short fiber is extruded into a cylindrical molded body 10 in which the short fibers are circumferentially oriented while passing through the rubber passage 8 of the environmental expansion die 5. For this reason, there is no obstacle such as a spider in the rubber passage 18, no weld line is generated in the cylindrical molded body, and the internal pressure of the cylinder is reduced to increase the discharge amount of the cylindrical molded body. Fiber orientation can be improved.
[0015]
The inner die 7 is mechanically fixed to a support member 17 arranged outside the extruder 1, and the rubber passage 18 between the inner die 7 and the extrusion screw 4 is a space in which only the short fiber-mixed rubber exists. The die 7 and the tip end of the extrusion screw 4 are located at positions facing each other and on the same central axis. For this reason, the short fiber mixed rubber 15 kneaded by the extrusion screw 4 does not suffer from flow inhibition in the rubber passage 18 and moves smoothly without changing the flow direction. Is extruded into a cylindrical molded body 10 in which the short fibers are circumferentially oriented.
[0016]
The shape of the inner die 7 gradually increases in diameter from the distal end portion 20 toward the discharge port 9, and the taper angle θ is 30 ° ≦ θ ≦ 80 °. The rubber channel inlet diameter is 20 to 120 mm, the rubber channel outlet diameter is 100 to 440 mm, and the expansion ratio (rubber channel outlet diameter / rubber channel inlet diameter) is set to 1.5 to 12.5. Is done. If it is less than the set range, the circumferential stretching near the discharge port 9 of the inner die 7 is small, and the short fibers are less likely to be circumferentially oriented in the inner and outer layers of the thick cylindrical molded body 10. On the other hand, if the setting range is exceeded, the stretching in the circumferential direction becomes too large, and if the extrusion pressure is inferior, the tubular molded body 10 is easily torn.
[0017]
Thereafter, the cylindrical molded body 10 without a weld line continuously extruded has a thickness of 1 to 10 mm in which short fibers are uniformly oriented in the circumferential direction from the inner layer to the outer layer as shown in FIG. The rubber sheet 22 is cut into one piece while being cut at one place by the cutting means 12, and then the rubber sheet 22 is cut at a predetermined interval.
[0018]
Examples of the rubber used here include natural rubber, butyl rubber, styrene-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, alkylated chlorosulfanated polyethylene, hydrogenated nitrile rubber, hydrogenated nitrile rubber, and unsaturated carboxylic acid metal salt. And a rubber material such as an ethylene-α-olefin elastomer composed of ethylene-propylene rubber (EPR) or ethylene-propylene-diene monomer (EPDM) alone, or a mixture thereof. Examples of the diene monomer include dicyclopentadiene, methylene norbornene, ethylidene norbornene, 1,4-hexadiene, cyclooctadiene, and the like.
[0019]
The rubber is made of fibers such as aramid fiber, polyamide fiber, polyester fiber, and cotton, and the length of the fiber varies depending on the type of the fiber. Short fibers of about 1 to 10 mm are used. Polyamide fiber, polyester fiber, and cotton having a size of about 5 to 10 mm are used. The addition amount is 10 to 40 parts by weight based on 100 parts by weight of the rubber.
[0020]
Further, a softener, a reinforcing agent composed of carbon black, a filler, an antioxidant, a vulcanization accelerator, a vulcanizing agent and the like are added to the rubber of the present invention.
[0021]
Examples of the softener include plasticizers for general rubbers, for example, phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP), adipates such as dioctyl adipate (DOA), and dioctyl sebacate (DOS). It includes sebacate-based phosphates such as tricresyl phosphate, and general petroleum-based softeners.
[0022]
Subsequently, as shown in FIG. 3, a synthetic fiber such as polyester, nylon, aramid, and vinylon, a natural fiber such as cotton, a plain woven canvas, a knitted fabric, and the like made of a mixed yarn thereof are formed on the molding mold 50 as a belt constituent member. A cover cloth 51, an adhesive rubber sheet 52, a cord 53 made of a fiber cord, and a compressed rubber sheet 54 obtained by cutting the rubber sheet 22 into a predetermined length are wound around a belt molded body for a V-ribbed belt by a sewing machine joint. 55. Of course, in the present invention, the cover cloth 51 may not be used.
[0023]
When a belt molded body for a double-ribbed belt is finished, a compressed rubber sheet, an adhesive rubber sheet, a core wire, an adhesive rubber sheet, and a compressed rubber sheet are wound on the molding mold as belt constituent members. To
[0024]
Then, the belt molded body 55 thus obtained is vulcanized to obtain a belt sleeve. Next, the belt sleeve is hung on a driving roll and a driven roll, is run under a predetermined tension, and is further moved so that the rotated grinding wheel 57 is brought into contact with the running belt sleeve 54 to thereby compress the compressed rubber sheet 54. A plurality of V-groove portions 56 are ground on the surface at one time. The belt sleeve 54 obtained in this manner is removed from the driving roll and the driven roll, and the belt sleeve is run around the other driving roll and the driven roll, cut to a predetermined width by a cutter, and cut into individual V-shapes. Finish with ribbed belt.
[0025]
When a double-ribbed belt is formed, the other surface is also ground to form a rib groove. This method can be performed according to, for example, Patent Registration No. 2762238.
[0026]
As the cord 53, a rope made of polyethylene terephthalate fiber, polyester fiber having ethylene-2,6-naphthalate as a main constituent unit, or polyamide fiber is used, and is subjected to an adhesion treatment for the purpose of improving the adhesion to rubber. Is done. As such an adhesive treatment, it is common to immerse the fiber in resorcin-formalin-latex (RFL solution) and then heat and dry to form an adhesive layer uniformly on the surface. However, without being limited to this, there is a method of performing a pretreatment with an epoxy or isocyanate compound and then treating with an RFL solution.
[0027]
The adhesive rubber sheet 52 is obtained by removing short fibers from the rubber compound of the compressed rubber sheet 54.
[0028]
As shown in FIG. 4, the obtained V-ribbed belt 70 has a substantially triangular cross-section in which a core wire 71 is embedded in an adhesive rubber 72 and extends below a compression rubber layer 75 as an elastic layer in the belt longitudinal direction. It has a plurality of ribs 74 and a cover cloth 76 on the back of the belt.
[0029]
【The invention's effect】
As described above, in the invention according to the present invention, the short fiber-mixed rubber kneaded by the extrusion screw is moved without obstructing the flow and without changing the flow direction, and is passed through the rubber passage of the annular expansion die. While short fibers were extruded into a cylindrical molded body oriented in the circumferential direction, the cylindrical molded body was cut along the extrusion direction to form a single rubber sheet in which the short fibers were oriented in the width direction. Thereafter, the rubber sheet was cut by a predetermined length along the length direction to obtain a compressed rubber sheet, and at least the core wire and the compressed rubber sheet were wound around a molding mold to produce a belt molded body, which was then vulcanized. After that, there is a method of manufacturing a power transmission belt, which finishes a belt sleeve having a rib portion by polishing, in which a short fiber mixed rubber kneaded with an extrusion screw is not subjected to flow inhibition in a cylinder. And to move without changing the flow direction, the cylindrical molded body without weld lines occur, there is a great advantage of being able to use the full width of the sheet were dissected for its compression rubber sheet of the transmission belt.
[Brief description of the drawings]
FIG. 1 is a schematic view of an extruder used in a method for producing a rubber sheet containing short fibers according to the present invention.
FIG. 2 is a schematic view showing a state in which an extruded cylindrical molded body is cut straight into a rubber sheet containing short fibers, and then a compressed rubber sheet.
FIG. 3 is a cross-sectional view showing a state in which a V-shaped groove is ground on a belt sleeve produced on a molding mold.
FIG. 4 is a sectional view of a V-ribbed belt obtained by the manufacturing method of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 extruder 2 extruder 3 cylinder 4 extrusion screw 5 annular expansion die 6 outer die 7 inner die 8 rubber passage 10 cylindrical molded body 12 cutting means 15 short fiber mixed rubber 18 rubber passage 22 rubber sheet 50 molding mold 51 cover cloth 52 Adhesive rubber sheet 53 Core wire 54 Compressed rubber sheet

Claims (1)

In a method for manufacturing a power transmission belt having a rubber layer in which a cord is embedded along the belt longitudinal direction and a rib portion extending in the longitudinal direction of the belt adjacent to the rubber layer,
A weld in which the short fiber mixed rubber kneaded by the extrusion screw is moved without obstructing the flow and without changing the flow direction, and the short fibers are circumferentially oriented while passing through the rubber passage of the annular expansion die. Extrusion molding into a cylindrical molded body without lines,
After cutting the cylindrical molded body along the extrusion direction into a single rubber sheet with the short fibers oriented in the width direction, the rubber sheet is cut by a predetermined length along the length direction and compressed. Into a rubber sheet,
At least the core wire and the above-mentioned compressed rubber sheet are wound around a molding mold to produce a belt molded body, and after vulcanization, the resultant is finished into a belt sleeve having a rib portion by polishing.
That the transmission belt manufacturing method.

Images