JPS5952291B2 - Manufacturing method of polyamide resin roll - Google Patents

Description

[Detailed description of the invention] The present invention provides a polyamide resin roll with a core.

It relates to a method of manufacturing at low cost with high productivity. Rolls made of polyamide resin alone are used in places with light loads, but cannot be used in places with high loads because the strength of the rolls is low, causing problems such as the rolls bending or breaking at the bearing and fern attachment parts. Na.

stomach. Therefore, methods such as shrink-fitting a polyamide resin hollow body onto a metal core (shrink fit method) or integrally molding it with a metal core (casting method) in the manufacturing method of monomer casting nylon hollow bodies are used. It is being However, in the case of the above-mentioned shrink fit method, the inner surface of the polyamide resin hollow body is expected to have a tightening margin of about 0.5%, and in addition to the cost of precision processing, the shrink fit processing cost is not only high, but also The only disadvantages are that the work is complicated and productivity is low, and in the case of the casting method, internal air bubbles and local depressions occur at the part that contacts the core metal surface, and distortions during polymerization remain as they are. However, there are problems such as the need to heat all of the core metal, resulting in low productivity and high costs. The present inventors have arrived at the present invention as a result of intensive studies aimed at solving the above-mentioned conventional problems and providing an inexpensive and highly productive method for manufacturing polyamide resin rolls. In this method, a metal core having an outer diameter approximately equal to the inner diameter of the hollow body is inserted into a high-temperature monomer-casting nylon hollow body immediately after molding, and the hollow body is polymerized and cooled to reduce its diameter and become hollow. The method of manufacturing a polyamide resin roll is characterized in that the inner surface of the roll is closely bonded to the outer surface of the metal core.

In the method of the present invention, a nylon hollow body is molded by a monomer casting method so that the inner diameter is the same size or larger than the outer diameter of a metal core, and immediately after the molding is completed, monomer casting is performed at a higher temperature than the mold. The nylon hollow body is taken out and the metal core is inserted into it using an insertion device.

When the roll is then cooled to room temperature in this state, the nylon hollow body contracts and the core metal is tightened to produce an effect similar to shrink fitting, making it possible to manufacture a polyamide resin roll with excellent quality and strength. Note that as the above-mentioned metal core metal, a metal core metal with a flat surface or a metal core metal with a knurled or grooved surface is suitable. The monomer casting method used in the method of the present invention usually involves mixing and heating a monomer (ε-prolactam in the case of nylon 6), a polymerization initiator, and an alkali metal catalyst.
This is a method in which polymerization and molding are carried out simultaneously under atmospheric pressure by injecting into a mold heated to 80°C, and since polymerization is an exothermic reaction, the internal temperature of the molded product during polymerization reaches a high temperature of around 200°C.

A nylon hollow body that has undergone initial shrinkage due to high-temperature initial polymerization immediately after molding by such a method undergoes two types of shrinkage: thermal shrinkage due to cooling and polymerization shrinkage due to the progress of the polymerization reaction while further polymerizing and cooling to room temperature. Since two contractions occur, the contraction rate is usually 3 to 6 in the radial direction of the hollow body.
Therefore, when inserting a metal core into a nylon hollow body, the inner diameter of the hollow body can be made larger (about 2 to 5% during cooling), taking into account heat shrinkage and polymerization shrinkage due to cooling.
Insertion of the metal core can be made that much easier.

Moreover, if the inner diameter is made to be about the same as that of the metal core, the interference will be large and a very strong tight fit will be possible. The method for manufacturing a polyamide resin roll of the present invention described in detail above is superior to the conventional shrink fitting method and casting method described above in the following points.

That is, compared to the manufacturing method using the shrink fit method: (a) Processing of the inner surface of the polyamide resin hollow body and shrink fitting process are not required, and the process can be manufactured at low cost.

(Opening) The tightness can be 4 to 10 times that of shrink fitting, so it is less susceptible to dimensional changes due to thermal expansion and water absorption.

(c) High productivity.

Comparing with the casting manufacturing method, (d) In the case of hot insertion of the metal core in the method of the present invention,
The high-temperature nylon hollow body immediately after molding by the monomer casting method has already undergone initial shrinkage due to initial polymerization, and there is less distortion than a casting roll, and there is no inclusion of air bubbles or depressions on the inner surface of the hollow body. Stable and high quality rolls can be obtained.

(E) It is not necessary to heat the core metal, and it can be manufactured at low cost.

(to) High productivity. However, as described above, the long product having a metal core covered with polyamide resin, which can be produced with higher productivity and lower cost than ever before by the present invention, can be cut to a predetermined length and machined. , wheels, gears, etc.

These wheels, gears, etc. made of polyamide resin not only have mechanical strength comparable to those made of metal, but also have special performance not found in metal, and have high industrial utility value. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A high-temperature monomer-casting nylon hollow body with an outer diameter of 125 mmφ, an inner diameter of 99 mmφ, and a length of 900 mm immediately after completion of molding by the monomer casting method, and a hollow body with an outer diameter of 98 mmφ and a length of 750 mm. A pipe-shaped rope was quickly inserted using an insertion device and cooled to room temperature.

In this case, the inner diameter of the portion of the nylon hollow body not in contact with the core metal was shrunk to 94 mmφ. Therefore, in the portion where the nylon hollow body was in contact with the core metal, a polyamide resin roll having a tightening margin of 4.1% and which was sufficiently usable for practical use was obtained. Example 2 A core metal whose circumferential surface was knurled with a pitch of 1 mm on the circumferential surface of a cylindrical rope with an outer diameter of 40 mmφ and a length of 300 mm was placed in a high-temperature monomer casted nylon hollow body ( When the roll was quickly press-fitted into a roll (outer diameter: 65 mmφ, inner diameter: 41 mmφ, length: 300 mm) using an insertion device and cooled to room temperature, a polyamide resin roll that could be used for practical purposes was obtained.

Claims (1)

[Claims] 1. A metal core having an outer diameter approximately equal to the inner diameter of the hollow body is inserted into a high-temperature monomer-casting nylon hollow body immediately after molding, and the hollow body is polymerized and cooled to reduce its diameter and form a hollow body. A method for producing a polyamide resin roll, characterized in that the inner surface of the roll is tightly bonded to the outer surface of the metal core.