JPH0489226A - Manufacture of rubber hose - Google Patents

Abstract

PURPOSE:To make the drawing process of a mandrel easily by extrusion molding a rubber material blended with the specified polymer content under the specified temperature, inserting the mandrel into the material, heating and vulcanizing, making the same shrunk mainly in the length direction to form a rubber hose, and then drawing out the mandrel therefrom. CONSTITUTION:As a blended rubber material, a material with 45wt.% or more of polymer content is used. The same is extruded in the extrusion process under the temperature of 70 deg.C or under. Thus, extrusion distortion in the length direction is made extremely large by extruding under the low temperature, and the material can be shrunk by 7-8% or more in the length direction at the time of vulcanization. Then, a mandrel of given bent shape is inserted into an extruded body. The body is vulcanized in the vulcanizing process usually at 150-160 deg.C, and the extruded body is vulcanized to form a rubber hose of curved shape retaining the shape of the mandrel. Said vulcanization is carried out for approximately 20-60 minutes similarly to the processes heretofore available. Then, the mandrel is drawn out of the rubber hose. At that time, as the rubber hose is prevented from getting shrunk in the diameter direction, the same can be drawn out extremely easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of manufacturing a rubber hose, and more particularly to a method of manufacturing a rubber hose, in which a mandrel is inserted into an unvulcanized extruded product and the mandrel is removed after vulcanization.

[Prior Art] When producing a bent hoss having a large diameter, such as a diameter of 13 mm or more, a mandrel having a predetermined bent shape is inserted into an extruded cylindrical extrudate, and then heated and vulcanized. This is done by fixing the bent shape and finally pulling out the mandrel. Here, in order to follow the shape of the mandrel and have an accurate shape, the inner diameter of the extruded body is made approximately 3% smaller than the outer diameter of the mandrel.

Therefore, when inserting the mandrel, the extruded body is inserted while expanding its diameter.

[Problems to be Solved by the Invention] By the way, rubber has the property of shrinking during vulcanization. This shrinkage occurs both in the lengthwise direction and in the radial direction, but the radial shrinkage is particularly problematic. That is, when the extruded body is inserted into the mandrel, the diameter of the extruded body is expanded, and internal stress that tends to reduce the diameter is accumulated. This internal stress is released during vulcanization. In addition, the heat during vulcanization causes the hose to contract roughly in the radial direction, which causes the vulcanized rubber hose to stick tightly to the mandrel surface, increasing tension, and requiring a great deal of effort to pull it out during the process of handling the mandrel. are doing.

This required a large amount of man-hours, resulting in low productivity and an increase in costs.

The present invention was made in view of these circumstances, and
The purpose is to facilitate the process of handling the mandrel.

[Means for solving the problem] The method for manufacturing a rubber hose of the present invention that solves the above problem includes:
Compound rubber material with a polymer content of 45% by weight or more at 70'C
An extrusion process in which an extruded body is formed by extrusion molding at the following temperature, an insertion process in which a mandrel is inserted into the extruded body, and the extruded body with the mandrel inserted is heated to vulcanize and shrink mainly in the length direction. a vulcanization process to make a rubber hose; a process of handling a mandrel from the vulcanized rubber hose;
It is characterized by being more.

One feature of the present invention is that a compound rubber material having a polymer content of 45% by weight or more is used. When the polymer content is less than 45% by weight, it becomes difficult to improve the mandrel drawing process. If it is 45% by weight or more, extrusion distortion will increase in the extrusion process,
As will be described later, radial contraction can be suppressed.

It should be noted that if the polymer content is 50% by weight or more, the cost will increase and the moldability will deteriorate, which is not preferable.

As polymers, NR, NBR, SBR, BRlI
Conventional rubber materials such as IR and EPDM can be used. Further, as compounds other than the bottomer, fillers such as carbon black and calcium carbonate, vulcanization accelerators, and softeners such as process oil can be used in the same manner as in the past.

Another feature of the present invention is that the extrusion process is performed at a temperature of 70° C. or lower. By extruding at such a low temperature, the extruder becomes extremely large in the longitudinal direction, and can be shrunk by 7 to 8% or more in the longitudinal direction during vulcanization. If the extrusion temperature exceeds 70'C, it becomes difficult to improve the mandrel handling process due to the small size of the extruder. In addition, even if the temperature is 70℃ or less, 60℃
If it is lower than 'C, the extrusion process itself becomes difficult, which is not preferable.

The mandrel insertion step is a step of inserting a mandrel having a predetermined bent shape into the extrusion body, and can be performed in the same manner as in the past.

In the vulcanization process, the extrudate is usually vulcanized at 150 to 160°C, and the extruded body is vulcanized in the same manner as in the past to form a bent rubber hose that maintains the shape of the mandrel. This vulcanization is carried out for about 20 to 60 minutes as in the conventional case.

Then the mandrel is handled rather than the rubber hose. At this time, since the rubber hose is prevented from contracting in the radial direction, it can be handled very easily.

[Function] In the method for manufacturing a rubber hose of the present invention, the polymer content is 4
It is 5% by weight or more, which is higher than the conventional 35% by weight, and the extrusion temperature is 70°C or lower, which is lower than the conventional 100 to 120'C. Therefore, extremely high extrusion strain remains in the extruded body.

In particular, because the extrusion temperature is low, the extrusion resistance is high and high strain remains in the length direction.

This distortion is exposed by heating during the vulcanization process, and the material contracts by the amount of distortion during vulcanization. At this time, it contracts significantly in the length direction by about 8% or more, and in the radial direction by about 3%. On the other hand, due to the force of contraction in the length direction, a force of diameter expansion acts in the radial direction. Therefore, the force of expanding the diameter due to contraction in the length direction opposes the force of decreasing the diameter due to contraction in the radial direction, and as a result, there is almost no contraction in the radial direction. Therefore, the tension force on the mandrel becomes extremely small or zero, and the work of handling the mandrel becomes extremely easy.

[Example] The following will be explained in detail with reference to Examples.

A compounded rubber material having a composition of 45% by weight of a polymer (EPDM), 35% by weight of carbon black, and the remainder a plasticizer, a vulcanizing agent, and a vulcanization accelerator is kneaded and supplied to an extrusion molding machine.

(Extrusion Step) The compounded rubber material is extruded into a cylindrical shape using an extrusion molding machine at a temperature of 70° C., and then immediately aramid fibers are wound into a spiral shape to form a reinforcing layer. Then, an outer skin layer was extruded on the surface of the reinforcing layer using the same compounded rubber material at a temperature of 70°C, and an inner diameter of 2
An extruded body having a diameter of 9.4 mm and an outer diameter of 38 mm is formed.

(Insertion Step) An iron mandrel bent into a predetermined shape and having a diameter of 3 Qmm is inserted into the center hole of the extruded body. Since the outer diameter of this mandrel is 0.6 mm larger than the inner diameter of the extruded body, the mandrel is inserted while the extruded body is expanded in diameter.

(Vulcanization Step) Next, the extruded body into which the mandrel has been inserted is placed in a vulcanization can, and heated at 160° C. for 30 minutes to be vulcanized.

At this time, the extruded body contracts about 8% in the length direction, and the inner diameter is 3Q.
The diameter was expanded to mm. Therefore, there was no strain on the mandrel, and the mandrel could be pulled out very easily in the next handling process.

(Conventional example) A compounded rubber material consisting of 35% by weight of a polymer (EPDM), 40% by weight of carbon black, and the remainder a plasticizer, a vulcanizing agent, and a vulcanization accelerator was extruded at a temperature of 120°C. An extrudate of similar shape was formed. Then, a mandrel was inserted in the same manner and the vulcanization process was performed in the same manner. However, in the drawing process, the rubber hose adheres closely to the mandrel and is under great strain, making it extremely difficult to handle. Incidentally, when the shape of the rubber hose was measured after handling, it was found that it had shrunk by about 2% in the length direction and had an inner diameter of 28.5 mm, which was Q, 9 mm smaller than the extruded body.

[Effects of the Invention] That is, according to the method for manufacturing a rubber hose of the present invention, handling of the mandrel becomes extremely easy, reducing man-hours and improving productivity, thereby reducing production costs. .

Patent applicant: Toyoda Gosei Co., Ltd.

Claims (1)

[Claims] (1) Compound rubber material with a polymer content of 45% by weight or more
An extrusion process in which an extrudate is formed by extrusion molding at a temperature of 0°C or less, an insertion process in which a mandrel is inserted into the extrudate, and the extrudate into which the mandrel is inserted is heated and vulcanized to mainly elongate the extrudate. A method for manufacturing a rubber hose, comprising: a vulcanization step of shrinking the hose in the horizontal direction to form a rubber hose; and a drawing step of pulling out the mandrel from the vulcanized rubber hose.