JPS6055292B2 - Rubber mandrel for rubber hose manufacturing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to improvements in rubber mandrels for manufacturing rubber hoses.

[Prior art]

Conventionally, when a rubber hose is molded and vulcanized, an iron mandrel has been inserted into the rubber hose for the purpose of regulating the inner diameter.

However, iron mandrels are not flexible and are therefore not suitable as mandrels for manufacturing long rubber hoses.

Therefore, in the production of long rubber hoses, instead of iron mandrels, synthetic resin mandrels (particularly nylon mandrels) with appropriate rigidity and flexibility or rubber mandrels with wire cord cores are used.

However, synthetic resin mandrels have a large thermal deformation and deformation occurs due to heating during rubber hose vulcanization, and the disadvantage is that the rubber hose product moves from the axial center position during vulcanization, resulting in uneven thickness of the rubber hose product after vulcanization is completed. There is.

Further, while a rubber mandrel is suitable as a mandrel because it has little deformation due to heat, it has the disadvantage that the inner rubber layer of the rubber hose product deteriorates early, causing oil leakage.

As a result of intensive research on the deterioration phenomenon of the inner rubber layer of rubber hose products, we found that this deterioration phenomenon occurs because the rubber mandrel is made of the same material as the inner rubber of the rubber hose product.
During vulcanization of the unvulcanized rubber hose, the vulcanizing agent migrates from the rubber mandrel vulcanizate side to the inner rubber layer side of the rubber hose, or the vulcanizing agent that migrates from the inner rubber layer side of the rubber hose to the rubber mandrel side further It has been found that this is due to reverse migration from the rubber mandrel side to the inner rubber layer of the rubber hose, and emulsion polymerization type synthetic rubber is particularly effective in preventing the reverse migration of the vulcanizing agent. The following findings were obtained. '[Problem to be solved by the invention] This invention was invented based on the above knowledge, and its purpose is to quickly deteriorate the inner rubber layer of rubber hose products and cause oil leakage. The purpose is to provide a rubber mandrel for manufacturing rubber hoses that does not cause such problems, and more specifically, one of its purposes is to provide a rubber mandrel that causes less migration of vulcanizing agent from the rubber mandrel side to the inner rubber layer side of the rubber hose. The other thing is,
To provide a rubber mandrel which receives a vulcanizing agent into the rubber mandrel and prevents it from moving back even if a vulcanizing agent migrates from the inner rubber layer of a rubber hose to the rubber mandrel side.

[Means for solving problems]

In order to achieve such an object, the rubber mandrel for manufacturing rubber hoses according to the present invention combines a rubber compound based on natural rubber or emulsion polymerization type synthetic rubber with a thiazole accelerator, a sulfur vulcanization system, and a resin vulcanization system. It was constructed by vulcanization using a sulfur-based or peroxide-based vulcanization system.

As the emulsion polymerization type synthetic rubber, for example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), etc. can be used, and solution polymerization type styrene butadiene rubber (SBR), isobutylene isoprene rubber i (IIR), ethylene propylene diene monomer rubber (EPDM), isoprene rubber (■R), or butadiene rubber (BR) cannot achieve the object of the present invention.

In addition, as the vulcanization system used in the present invention, a vulcanization system using a combination of a thiazole vulcanization accelerator, which is an organic vulcanization accelerator, and sulfur, a resin vulcanization system, or a peroxide vulcanization system is used. Often, other vulcanization systems cannot achieve the objectives of the present invention.

Furthermore, in the present invention, it is not effective to apply the above-mentioned rubber and vulcanization system to a rubber mandrel individually, and the object of the present invention can only be achieved by combining the above-mentioned rubber and vulcanization system. It is.

[Example] Next, in Examples, three specific aspects and effects will be compared and displayed.

Rubbers currently widely used as compound compositions for rubber mandrels, namely natural rubber, SBR (emulsion polymerization type), SB
R (solution polymerization type), NBR (solution polymerization type), I
IR (solution polymerization type), EPDM (solution 4/liquid polymerization type), commonly used vulcanization systems such as thiuram accelerator and sulfur, thiazole accelerator and sulfur, resin vulcanization, peroxide vulcanization. For each combination, the outer diameter is 12W with the following formulation! A rubber mandrel of T was obtained by extrusion molding and leaded vulcanization (150° C. x 6 powder vulcanization).

Compounds for rubber mandrelsOn the other hand, for the inner rubber layer of rubber hoses,
The formulation has already been determined according to the required characteristics and cannot be changed significantly, and most of them are based on NBR (due to oil resistance), and the following combination of thiuram accelerator and sulfur is used. I followed him.

As a compounding test method for the inner rubber layer of the rubber hose, an unvulcanized inner rubber tube with a thickness of 3.5 TIrm was extruded and coated on the rubber mandrel with an outer diameter of 127 nwt using a crosshead extruder, and the rubber mandrel and the unvulcanized The inner rubber tube was attached tightly.

After that, leaded vulcanization was performed and the unvulcanized inner surface rubber tube was vulcanized, and a breakage evaluation sample was taken from the vulcanized inner surface rubber tube using a No. 3 dumbbell, and a tensile test was performed using the JIS K63Ol method. The quinone status of the parallel section of the dumbbell sample was determined. Next, use the following 3 evaluation criteria:
The test results are shown in each stage. 1...
... No cracks 2 ... Occurrence of few cracks 3 ... Occurrence of many cracks [Effects of the Invention] As explained above, the rubber mandrel according to the present invention has the following properties:
The base material is natural comb or emulsion polymerization type synthetic rubber, and it is composed of a combination of this base material, a thiazole accelerator, and a sulfur vulcanization system, a resin vulcanization system, or a peroxide vulcanization system. The migration of the vulcanizing agent from the rubber mandrel side to the inner rubber layer of the rubber hose is prevented, and the vulcanizing agent that has migrated from the inner rubber layer of the rubber hose to the rubber mandrel side further migrates back to the inner comb layer side of the rubber hose. be prevented.

Therefore, according to the rubber mandrel according to the present invention, it is possible to obtain an excellent rubber hose with no deterioration of the inner rubber layer and no oil leakage.

Claims (1)

[Claims] 1 A rubber compound based on natural rubber or emulsion polymerization type synthetic rubber is combined with a thiazole accelerator and a sulfur vulcanization system.
A rubber mandrel for manufacturing a rubber hose, characterized in that it is vulcanized by a resin vulcanization system or an oxide vulcanization system.