JP5767528B2 - PTFE and modified PTFE film processing method and medical rubber plug manufacturing method - Google Patents

Description

The present invention relates to a PTFE film for laminating, for example, a rubber molded product and a method for producing a medical rubber stopper laminated with a PTFE film.

  For example, a function required for a rubber member used for a (medical) rubber stopper of a container filled with pharmaceuticals or the like is to maintain a sealed state, and specifically, there is a risk of ingress of gas or microorganisms from the outside. It is said that there is no. For this function, it is common practice to use butyl rubber, which has a low gas permeability, as a raw material, and to fill a gap with a container into which microorganisms may enter using stress due to rubber elasticity.

However, since butyl rubber itself is a highly sticky raw material and is used in a compressed state due to rubber elasticity, the movement in a state of being in close contact with a container or the like is not smooth, and when used for sliding parts It is very difficult.
To solve this problem of poor slidability, silicone oil is applied to the sliding surface (Patent Documents 1 and 2). However, in recent years, there is a concern about the influence of silicone oil on chemicals, and there are many cases where the application of silicone oil is restricted.

JP-A-10-201844 JP 2003-190285 A

  As a means for improving the slidability without applying silicone oil, a method of laminating a film having good slidability on the surface of the rubber member is conceivable. As a film to be laminated, a film made of a fluororesin is preferable because it has good slidability, chemical stability, and high heat resistance, and a polytetrafluoroethylene (PTFE) film is particularly preferable. It is done.

Apart from the problem of slidability, there is also a demand to avoid contact between the rubber member and the chemical solution. This is to prevent elution from the rubber member into the chemical solution or entry from the chemical solution into the rubber member.
In order to prevent the chemical liquid from coming into contact with the surface of the rubber member, a method of laminating with a film or the like that does not have a chemical liquid permeability can be considered. For this purpose, a film made of a fluororesin such as PTFE is considered preferable because it is chemically stable and has high heat resistance.

As a process for producing a rubber member laminated with a PTFE film, a flat unvulcanized rubber sheet and a PTFE film are laminated and molded into a three-dimensional rubber plug shape while performing vulcanization adhesion by rubber press molding. Is expected. In such molding, the surface area of the film usually changes before and after molding.
When a laminate product is actually molded by rubber press molding, when the surface area of the PTFE film increases, the PTFE film is stretched according to the increased surface area, and the thickness of the PTFE film after molding is stretched (area A decrease corresponding to the degree of increase is observed.

  However, it is known that a PTFE film crystallizes by being stretched to generate voids called microvoids (small voids). Further, it is known to become a porous film. These voids adversely affect the sealing properties required for the rubber member. Further, when the rubber member and the chemical solution are used for an application, the contact between the rubber member and the chemical solution cannot be prevented, and the presence of voids is not preferable.

The present invention has been made in view of the above problems, PTFE film voids hardly occur in the rolled Shin processing, and to provide a processing method of the modified PTFE film, and a manufacturing method of a medical rubber stopper.

The processing method of the PTFE and modified PTFE film according to the present invention includes a heating step of heating the PTFE or modified PTFE film to the melting point or higher, and the film heated to the melting point or higher at a cooling rate of 10 ° C./min or more. And a cooling step for cooling across the melting point. And the said heating process and cooling process are performed by pinching both surfaces of the said film with an iron plate.

The method for producing a medical rubber plug according to the present invention includes a heating step of heating a PTFE or modified PTFE film to a melting point or higher, and the film heated to the melting point or higher at a cooling rate of 10 ° C./min or more. It comprises a cooling step of cooling across the melting point and a step of vulcanizing and molding the cooled film with a rubber member. The heating step and the cooling step are performed by sandwiching both surfaces of the film with iron plates.

In any method, the thickness of the film before the heating step is preferably 0.05 mm or more and 0.3 mm or less.

ADVANTAGE OF THE INVENTION According to this invention, the rubber plug for medical treatment with few gaps of the film of PTFE and modified PTFE and the laminated PTFE film in which voids are less likely to be generated by stretching treatment can be provided.

  In general, the crystallinity of a resin, which is a polymer compound, is affected by its molecular weight, molecular weight distribution, and the like, but also changes depending on the thermal history. Specifically, if the cooling is rapidly performed after melting at a temperature equal to or higher than the melting point, the three-dimensional structure is fixed before the crystallization proceeds and the crystallinity becomes low. On the other hand, when it is slowly cooled after melting, the degree of crystallinity increases. Further, since the heat of fusion is the amount of heat necessary to melt the crystal, the heat of fusion is small for a polymer having a low crystallinity. The same applies to fluororesin (PTFE).

Therefore, in order to solve the problem of obtaining a PTFE film in which voids are hardly generated by stretching, the present inventor selected and studied heat of fusion as an index of crystallinity of the PTFE film.
And when the heat of fusion as a parameter | index was made into a fixed value or less, it discovered that the PTFE film which a space | gap does not easily produce in an extending | stretching process was obtained.
Table 1 shows the relationship between the heat of fusion and the degree of formation of voids by changing the heat of fusion of the PTFE film to change the heat of fusion.

  Since PTFE does not exhibit fluidity even at temperatures above the melting point, it is not a method of forming a film from an extruder through a die like a general thermoplastic resin, but a skive method is generally used to form a film. . The skive method is a method in which a cylindrical compression-molded body is produced using PTFE powder as a raw material, fired at a temperature equal to or higher than the melting point, and then cut into a film having a desired thickness.

Industrially, the larger size of the compression-molded body is advantageous in terms of cost. However, when the temperature difference from the refrigerant (environment) is increased in the cooling after firing, the temperature is increased due to the low thermal conductivity of PTFE. A temperature gradient occurs and the crystallinity cannot be made uniform.
Therefore, in order to make the degree of crystallinity of the compression-molded body uniform, cooling is generally performed gradually industrially. Specifically, the cooling rate is usually made slower than 50 ° C./hour, and the heat of fusion of the film cut from the molded body thus cooled is about 28 mJ / mg.

The PTFE film used in Table 1 is also produced by the skive method.
The PTFE film used was cut to a thickness of 0.1 mm by Nippon Valqua Company.
The heating in Table 1 was performed by cutting the PTFE film into rectangles of a certain size, sandwiching both sides with flat iron plates, and placing them in a thermostat set at 350 ° C. for a certain period of time.

The cooling in Example 1 was performed by putting it in water at room temperature (around 25 ° C.) with the PTFE film sandwiched between iron plates. Cooling in Example 2 was performed by lowering the temperature in the thermostatic chamber at −10 ° C./min while the PTFE film was put after heating.
The reason why the PTFE film is sandwiched between the iron plates in the process of reducing the crystallinity is to prevent deformation of the PTFE film due to thermal shrinkage during rapid cooling.

  The heat of fusion in Table 1 is the result of measurement according to JIS K7122 “Method of measuring the transition heat of plastic”. The DSC apparatus used is DSC6220 manufactured by SII Nano Technology. For the measurement, approximately 8 mg of PTFE film was used as a test piece, and the heating rate was 10 ° C./min. The heat of fusion was calculated from the area of the endothermic site near 330 ° C., which is the melting point of PTFE.

A sample for measuring the number of voids was prepared as follows.
The PTFE films of Examples 1 and 2 and Comparative Example 1 were subjected to ion beam treatment, laminated on unvulcanized halogenated butyl rubber (rubber member) formed into a sheet having a thickness of 2 mm, and press vulcanized. . A mold for press vulcanization has nine cavities imitating a medical rubber stopper having an inner diameter of 12 mm and a height of 7 mm.

For the press vulcanization, 2-di-n-butylamino-4,6-dimercapto-s-triazine (manufactured by Sankyo Kasei Co., Ltd., Disnet (registered trademark)) was used as a crosslinking agent. The press vulcanization was performed for 5 minutes under the conditions of 180 ° C. and 20 MPa.
Table 2 shows raw materials and use ratios in press vulcanization excluding the PTFE film.

The surface area of the film was changed from 113 square mm to 376 square mm by press vulcanization, and stretched approximately 3 times.
Regarding the presence or absence of voids, the digital microscope VHX-600 manufactured by Keyence Co., Ltd. was used for each of 9 medical rubber plug-shaped molded products vulcanized and molded using the PTFE films of Examples 1 and 2 and Comparative Example 1. Used and confirmed by observing the surface at a magnification of 150 times.

The number of voids in Table 1 is the number of holes having a length of the longest portion of 100 μm or more among the holes penetrating the PTFE film in the molded product.
As can be seen from Table 1, the number of voids produced by vulcanization molding was 8.7 for each molded product (comparative example 1) using untreated PTFE, whereas the heat of fusion. In the molded product (Example 2) subjected to the treatment for reducing the slag to 23 mJ / mg, the voids were less than 0.5 per molded product, and the molded product subjected to the treatment for reducing the heat of fusion to 19 mJ / mg ( No voids were observed in Example 1).

  There is no particular designation for the heating and cooling methods in the process of reducing the crystallinity of the PTFE film, but it is necessary to devise measures to prevent deformation of the PTFE film due to thermal shrinkage during rapid cooling. In order to prevent deformation of PTFE film due to heat shrinkage, in small scale processing, for example, both sides of the PTFE film are sandwiched between flat iron plates. In large scale processing, the PTFE film from a long roll is intermittently fed. Batch processing that heats and cools between steel plates at the time of stopping, or continuous processing that heats and cools through a heat-resistant flat plate that performs continuous feeding and sandwiches both sides of the PTFE film and moves with the PTFE film Is adopted.

  The heating rate in the treatment for reducing the crystallinity is not particularly specified, but it is sufficient that the PTFE film surely reaches a temperature equal to or higher than the melting point. The cooling rate after heating is not particularly specified, but the cooling rate at the time of crossing the melting point is preferably 10 ° C./min or more, and more preferably 100 ° C./min or more. The purpose of the rapid cooling is to control the crystallinity, and the cooling rate after the temperature is sufficiently lowered from the melting point is not specified.

  Although there is no restriction | limiting in particular in the thickness of the PTFE film to be used, 0.3 mm or less is preferable and 0.2 mm or less is still more preferable in order to acquire the rapid cooling effect. In order to maintain the film form in the vulcanization molding treatment, it is preferable that the film has a certain degree of strength, and the PTFE film preferably has a thickness of 0.05 mm or more. That is, the thickness of the PTFE film is preferably 0.05 mm or more and 0.2 mm or less.

  In order to manufacture a rubber plug laminated with a PTFE film, adhesion between the PTFE film and rubber is necessary. In order to obtain a PTFE film having no voids after stretching, a process of heating the PTFE film at a high temperature is involved. Therefore, the adhesion treatment to the rubber member is preferably performed after controlling the crystallinity. What is necessary is just to perform the process which makes it possible to adhere | attach the PTFE film which is hard to adhere | attach on a rubber member by a known method. For example, a method of chemically treating the adhesive surface of the PTFE film using sodium metal and liquid ammonia (sodium-ammonia treatment), a method of physically changing the structure of the adhesive surface of the PTFE film by plasma treatment, etc. Is mentioned. Sodium-ammonia treatment is preferable because it can increase the adhesive strength and is a chemical treatment, and thus has little influence on crystallinity. The plasma treatment is preferable because an adhesion treatment without coloring is possible.

  As the material of the film to be used, modified PTFE such as perfluoroalkoxide modified PTFE can be used in addition to PTFE. With respect to the modified PTFE film, the generation of voids can be prevented in vulcanization molding by performing a treatment for reducing the heat of fusion to 23 mJ / mg or less, preferably to 19 mJ / mg.

The present invention may be a film of the film and PTFE or modified PTFE of the PTFE and modified PTFE laminated rubber molded article is used for a medical rubber stopper laminated.

Claims (4)

A heating step of heating the PTFE or modified PTFE film above its melting point;
A cooling step of cooling across the melting point heated the film a 10 ° C. / min or higher cooling rate than the melting point, Ri Tona,
The PTFE and modified PTFE film processing method, wherein the heating step and the cooling step are performed by sandwiching both surfaces of the film between iron plates . The thickness of the film before the heating step is 0.05 mm or more and 0.3 mm or less.
The processing method of the film of PTFE and modified PTFE of Claim 1. A heating step of heating the PTFE or modified PTFE film above its melting point;
A cooling step of cooling the film heated above the melting point across the melting point at a cooling rate of 10 ° C./min or more;
The cooled the film and a step of vulcanizing integrated with a rubber member, Ri Tona,
The method for producing a medical rubber plug, wherein the heating step and the cooling step are performed by sandwiching both surfaces of the film between iron plates . The thickness of the film before the heating step is 0.05 mm or more and 0.3 mm or less.
The manufacturing method of the medical rubber stopper of Claim 3.