JPH0747614A - Core for molding rubber - Google Patents

Abstract

PURPOSE:To develop a material for a core having heat resistance capable of withstanding vulcanization, flexibility capable of pulling out the core and durability withstanding repeated use. CONSTITUTION:A core for molding a rubber product having a hollow shape (e.g. hose or tube) is composed of a block copolymer elastomer of polyoxytetramethylene glycol and tetramethylene glycol 2,6- naphthalenedicarboxylate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a durable core for use in producing a rubber hollow molding. More specifically, when using a polyester elastomer obtained from polytetramethylene glycol, 2,6-naphthalenedicarboxylic acid and tetramethylene glycol, it is excellent in durability and is used for molding a hollow rubber product using a core inside. Regarding the core to be used.

[0002]

2. Description of the Related Art When molding a rubber hollow molded product such as a hose or a tube, a raw rubber is wrapped around the surface of a core and crosslinked by vulcanization or the like, and then the hose or tube is molded except the core. Things are often done. The core is required to be flexible and elastically recoverable, and durable enough to be repeatedly used after pulling out the core after vulcanization.

However, no material that satisfies these requirements has been found and durability is insufficient, but polyoxytetramethylene glycol (also referred to as polytetramethylene glycol), terephthalic acid and tetramethylene are used due to other properties. Polyester elastomers derived from glycols have been used.

[0004] However, the conventional core material lacks durability enough to withstand repeated use, and the cause of deterioration of the material core due to repeated use cannot be determined, and attempts for improvement have not been successful.

[0005]

The object of the present invention is to have durability and hardness and flexibility that can be used as a core, when it is used as a core for making a hollow molded article of rubber as described above. It is to provide a material that can be easily molded into a core shape and easily peels off from rubber.

[0006]

[Means for Solving the Problems] As a result of repeated studies to find a method for solving the above problems, the present inventors have found that terephthalic acid used in a conventional polyester elastomer is replaced with 2,6-naphthalene. A core using a polyester elastomer changed to a dicarboxylic acid has been found to be able to solve the problems and has reached the present invention.

That is, according to the present invention, when molding a hollow rubber product using a core inside, which comprises a polyester elastomer obtained from polytetramethylene glycol, 2,6-naphthalenedicarboxylic acid and tetramethylene glycol The core to be used.

Here, the polytetramethylene glycol is a compound in which tetramethylene glycol having an average molecular weight of 500 to 3000 is condensation-polymerized and has a hydroxyl group at the terminal, and other components are copolymerized with this. May be. Examples of the copolymerization component include components such as oxyethylene glycol and oxypropylene glycol.

This polytetramethylene glycol is 30
Used to be contained in the polyester elastomer in an amount of not less than wt%, preferably 40 to 70 wt%. When the amount of polytetramethylene glycol is large, it is not preferable because it is too soft and the strength is low. On the other hand, if the amount is too small, it is too hard and it is difficult to pull out the core when the core is pulled out.

Further, polytetramethylene glycol,
The polyester elastomer obtained from 2,6-naphthalenedicarboxylic acid and tetramethylene glycol is obtained by using the above-mentioned polytetramethylene glycol, 2,6-naphthalenedicarboxylic acid and tetramethylene glycol,
A polyester obtained in the same manner as a normal polyester polymerization reaction, but other than this, a copolymerization component generally used as a component of the polyester such as other dicarboxylic acid or diol of less than 30 mol% as a copolymerization component. The ingredients can be applied.

The polyester elastomer as the core of the present invention has an intrinsic viscosity of 0.8 or more, preferably 1.0 or more. When the intrinsic viscosity is low, the strength of the core becomes low, which is not preferable.

It goes without saying that the polyester elastomer of the present invention may contain a stabilizer, a colorant, a reinforcing material and the like in addition to the above polymers.

The polyester elastomer thus obtained is molded into a core shape and used for molding rubber. In molding the rubber, for example, raw rubber containing a reinforcing material, a filler, a cross-linking agent and the like is wound around the core, heated and crosslinked, and then the core is pulled out to obtain a rubber molded product. In this withdrawing process, water may be press-fitted between the rubber and the core. Since the core is often used under such usage conditions, the shape of the core is often a round bar. When the polyester elastomer of the present invention is used, this round bar is molded by a method similar to the usual extrusion molding of thermoplastic resin.

The rubber molded into such a hollow shape is
It is generally called a rubber, for example, a type that includes butadiene, isoprene, chloroprene and the like, and is of a type in which a double bond is cross-linked by using sulfur or a sulfur compound or a radical initiator. These rubbers contain what is generally called an anti-aging agent, but the effect of the present invention is greater when these rubbers are contained. In particular, when an amine-based antioxidant is contained, the present invention is preferable because the effects such as durability are enhanced.

[0015]

INDUSTRIAL APPLICABILITY The core of the present invention has excellent durability when used as a core for cross-linking and molding rubber, and thus can be repeatedly used. It has the advantage that the surface properties of rubber are also good.

Further, it is a feature of the present invention that since it is thermoplastic, it can be easily formed into a core by extrusion molding, has high heat resistance and can be subjected to treatment such as vulcanization at high temperature.

[0017]

The present invention will be described in detail with reference to the following examples. In the examples, "part" means "part by weight".

[0018]

Example 1 50 parts of dimethyl 2,6-naphthalenedicarboxylate, 30 parts of tetramethylene glycol and 50 parts of polytetramethylene glycol having an average molecular weight of about 1000 were subjected to transesterification reaction in the presence of a catalyst and then polycondensation reaction under reduced pressure. Thus, a polyester elastomer having an intrinsic viscosity of 1.24 was obtained.

This polyester elastomer was melt extruded into a round bar having a diameter of 6 mm.

On the other hand, 100 parts of natural rubber and 5 parts of zinc oxide,
Stearic acid 2 parts, sulfur 2.8 parts, di-2-benzothiazyl sulfide 1 part and Antigen P (Sumitomo Chemical Co., Ltd.) 1
The parts were kneaded in advance, wound on the round bar to a thickness of 5 mm, and then vulcanized at 145 ° C. for 15 minutes.

When the round bar was pulled out while water was press-fitted between the rubber and the round bar of the vulcanized molded product, the round bar was easily pulled out, and the rubber surface after being pulled out was also clean.

As a result of repeating the use of the drawn round bar as a core for molding rubber again, no damage was observed after 20 times.

[0023]

Comparative Example 1 Dimethyl terephthalate was used in place of dimethyl 2,6-naphthalenedicarboxylate of Example 1,
A round bar was prepared in the same manner as in Example 1 using a polyester elastomer having an intrinsic viscosity of 1.35, which was manufactured in the same manner as in Example 1, and was used to mold rubber. As a result of repeated use by repeated use, molding could be performed in the same manner as in Example 1 for the first time, but fractured at the 10th time.

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Claims (1)

[Claims] 1. A polycondensation product of 2,6-naphthalenedicarboxylic acid and tetramethylene glycol, which is a core used for molding a hollow rubber product and which contains polyoxytetramethylene glycol as a polyether component. A rubber molding core made of a polyester elastomer containing as a polyester component.