JPH02196608A - Continuously vulcanizing method for extruded rubber material - Google Patents

Abstract

PURPOSE:To advance the surface vulcanization of a sponge rubber part in a short time in such a degree that foaming gas is made impermeable therethrough by utilizing fluorine-based inactive liquid having specified b.p. selected from perfluorotrialkylamine, perfluoroalkyltetrahydrofuran and perfluoropolyoxyalkylene or vapor thereof as a heating medium. CONSTITUTION:A surface prevulcanization tank 11 is arranged in the prestage of a microwave vulcanization tank 3 and the surface of at least sponge rubber part is brought into contact with a heating medium and surface prevulcanization is performed. As this heating medium, fluorine-based inactive liquid or vapor thereof is utilized which consists of one kinds or two or more kinds selected from perfluorotrialkylamine, perfluoroalkyltetrahydrofuran and perfluoropolyoxyalkylene and has >=170 deg.C b.p. This heating medium is high in heat transfer coefficient and low in surface tension in both liquid and vapor state. Therefore this heating medium is favorably infiltrated into the surface of the sponge rubber part and excellently transfers heat. Therefore vulcanization of the skin layer of the surface is advanced in a short time in such a degree that foaming gas is made impermeable therethrough.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to the continuous vulcanization of rubber extrudates having sponge rubber parts, and microwave vulcanization is performed as the main vulcanization step during the vulcanization process. The present invention relates to a continuous vulcanization method for rubber extrudates.

In particular, this method is suitable for continuous vulcanization of rubber extrudates such as automobile weather strips, which require fine surface roughness from the standpoint of sealability and design, that is, a clean surface texture.

<Prior art> Recently, continuous vulcanization of rubber extrudates such as weather strips has been
From the standpoint of heating efficiency and productivity, methods that include microwave (UHF) vulcanization as the main vulcanization step during the vulcanization process are mainstream instead of the conventional fluidized bed vulcanization (using glass beads). It is.

For example, as shown in FIG. 2, the extrusion head 1 of the extruder 1
The extrudate M from a is introduced into a UHF vulcanization tank 3 for UHF vulcanization, and further introduced into a hot air tank 5 for hot air vulcanization. It's a tank.

However, when the rubber extrudate M includes a sponge rubber part S, such as the rubber extrudate 21 and 23 shown in Figures 3 and 4, UHF vulcanization is an internal heating method, so fluidized bed vulcanization, Compared to the external heating method, it is difficult to obtain a sponge rubber part with a beautiful surface texture. That is, in the sponge rubber portion S, gas accompanying foaming is generated before surface vulcanization progresses to the extent that foaming gas hardly permeates to the outside, that is, before a thin skin layer is formed. This is because gas permeates through the surface layer of the sponge rubber portion.

<Problems to be Solved by the Invention> At this time, in order to make the surface of the sponge rubber part clear, it is possible to pre-vulcanize the surface of the sponge rubber part by bringing the surface into contact with a heating medium prior to UHF vulcanization. Conceivable.

However, it has been difficult to vulcanize rubber extrudates with good productivity using general-purpose heating means conventionally used for vulcanizing rubber extrudates.

In other words, heat 1a (hot jet) and infrared heating essentially involve air layer heat transfer, which rapidly raises the rubber surface to the vulcanization temperature and quickly vulcanizes the surface to the point where foaming gas cannot pass through. Furthermore, although it is possible to rapidly raise the rubber surface to the vulcanization temperature using a liquid heat medium such as molten salt, it is necessary to remove the heat medium attached to the extrudate. shall be.

In view of the above, an object of the present invention is to enable surface vulcanization of a sponge rubber portion to proceed in a short time to the extent that foaming gas does not pass through, prior to UHF vulcanization, and to perform vulcanization such as removal of heat medium. It is an object of the present invention to provide a continuous vulcanization method for rubber extrudates, which does not require post-curing treatment and can produce rubber extrudates having a sponge rubber portion with a clean surface texture with good productivity.

<Means for Solving the Problems> The present invention solves the above problems by a continuous vulcanization method for rubber extrudates having the following configuration.

A method applied to the continuous vulcanization of a rubber extrudate having a sponge rubber portion, the method comprising microwave vulcanization as a main vulcanization step during the vulcanization step, and prior to the microwave vulcanization, at least In a continuous vulcanization method including a step of surface pre-vulcanization by bringing the surface of the rubber part into contact with a heating medium, the heating medium includes perfluorotrialkylamine,
It is characterized by using a fluorine-based inert liquid or its vapor having a boiling point of 170° C. or higher and consisting of one or a mixture of two or more selected from perfluoroalkyltetrahydrofuran and perfluoropolyoxyalkylene.

<Detailed Description of Means> Hereinafter, the continuous vulcanization method for rubber extrudates of the present invention will be explained based on the details. The same parts as those in the conventional example are given the same reference numerals, and all or part of the explanation thereof will be omitted.

FIG. 1 is a process schematic diagram showing the method of the present invention. The difference from the conventional method is that a surface pre-vulcanization tank 11 is disposed in the pre-process of the UHF vulcanization tank 3, and the process is performed prior to microwave vulcanization. At least the surface of the sponge rubber portion is brought into contact with a heat medium to perform surface pre-vulcanization.

In the present invention, the heating medium is a fluorinated non-fluoride having a boiling point of 170° C. or more and is composed of one or a mixture of two or more selected from (1) perfluorotrialkylamine, (2) perfluoroalkyltetrahydrofuran, and (2) perfluoropolyoxyalkylene (polyether). Use active liquids or their vapors.

Here, the reason why the boiling point of the fluorine-based inert liquid is set to 1°C or higher is to correspond to the temperature at which rubber extrudates can be vulcanized with good productivity.

Specific examples of the above ■■■- in fluorine-based inert liquids include (■) perfluorotributylamine, perfluorotripentylamine, perfluorotrihexylamine, etc.; (■) perfluorooctyltetrahydrofuran, perfluorohexyltetrahydrofuran, perfluor Nonyltetrahydrofuran, closed,
One type of homopolymer or a copolymer of two or more types in which the alkylene group is selected from methylene, ethylene, propylene, trimethylene, etc. can be mentioned, respectively.

More specifically, ■、■ and Sumitomo 3M■
RVC-43-to- with a boiling point of 170°C or higher, manufactured and sold under the trade name "Florinat" from
tl" (■) of C or above, and "5311" (■) can be used. The boiling points of each are 174, 215, 2.
53 (t) J, "215 (℃)".
It is possible to use model numbers such as ”. The boiling points of each are "230±5.260±5 (°C)" in order.

Furthermore, each of the above fluorine-based inert liquids has the following common characteristics.

(1) Excellent electrical insulation and thermal conductivity.For example,
Heat transfer coefficient of 215℃ steam of Floriner) FC-70J (
kcal-s-"-h-'-t) is approximately 600, which is approximately twice the heat transfer coefficient of 300 for silicone oil liquid at 215°C.

(2) Completely inert and does not attack metals, plastics, rubber, etc.

(3) Very low surface tension and excellent permeability (compatibility)0 For example, "Florinat FC-70-71
In the case of J, it is I B dyn/cm.

(4) Non-flammable, non-toxic and odorless.

In addition, perfluorocarbons such as perfluorohexane and perfluorodecalin are commercially available as fluorine-based inert liquids other than the above ■■■, but these have a boiling point of 17
At present, it cannot be used in place of the above-mentioned heat medium of the present invention at temperatures below 0°C, but in the future, if one with a high boiling point is developed, it may be possible to use it.

The form of the above-mentioned surface pre-vulcanized cypress 11 is not particularly limited, but the forms shown in Figs. 5 to 7 can be considered. In this case, since the surface pre-vulcanization may be performed only on the sponge rubber portion, the heating medium may contact only the surface of the sponge rubber portion.

(1) Fig. 5 shows a configuration in which a bathtub 13 equipped with a heating means 12 such as a heater and storing a liquid heat medium is used as a vulcanization tank, and the extrudate M is forcibly immersed in the liquid heat medium. , surface pre-vulcanization is performed. As a heat medium, it has a high boiling point.
It is desirable to use Fluorinert FC-71'', Galden H3J, etc.

(2) In Fig. 6, a heating means 15 and a circulation means (pipes equipped with a pump 16) are placed in a separate position from the funnel-shaped heat medium recovery tank 14, and the discharge side of the pump 16 is placed above the surface vulcanization tank. A shower nozzle is arranged in the vulcanization tank, and a liquid heat medium is used in circulation. As a heat medium,
Those exemplified in (1) above can be used. Although this method requires a more complicated device than the above method (1), the heating efficiency is better than the above method (1) because the heating medium is ejected toward the surface of the sponge rubber portion of the extrudate using a shower.

(3) In Fig. 7, a cooling coil 18 is arranged at the inlet/outlet of the extrudate M to prevent the vapor heat medium V from escaping, and a heating means 12 such as a heater is arranged at the bottom to heat the steam 'a19. It is configured as a sulfur tank, and the extrudate is passed through saturated steam formed by heating and evaporating a liquid heat medium stored at the bottom. In terms of equipment, this method is as follows (1) (2)
), but has the best heating efficiency. As the heat medium is used after being vaporized, the above (1) is used.
- Fluorinert FC, which has a lower boiling point than in case (2)
-70.43" is preferably used.

<Actions and Effects of the Invention> As described above, the continuous vulcanization method for rubber extrudates of the present invention includes the following steps:
A method commonly used for continuous vulcanization of rubber extrudates having a sponge rubber part, which includes microwave vulcanization as a main vulcanization step during the vulcanization process, and prior to the microwave vulcanization, at least In a continuous vulcanization method that includes a step of surface pre-vulcanization by bringing the surface of the rubber part into contact with a heating medium,
A fluorinated inert liquid having a boiling point of 170° C. or higher, consisting of one or a mixture of two or more selected from perfluorotrialkylamine, perfluoroalkyltetrahydrofuran, and perfluoropolyoxyalkylene, or its vapor is used as the heat medium. With this configuration, the following actions and effects are achieved.

The heat medium used for surface pre-vulcanization prior to UHF vulcanization has a high heat transfer coefficient and low surface tension in both liquid and vapor states, so it blends well with the surface of the sponge rubber part and transfers heat well. Therefore, the temperature of the surface of the sponge rubber portion increases rapidly, and vulcanization of the surface skin layer progresses in a short time to the extent that the foaming gas does not permeate. Therefore, even if the extrudate is introduced into the UHF vulcanization tank and foaming gas is generated in the sponge rubber part due to internal heating, the gas will not pass through the surface of the sponge rubber part, and the sponge rubber with a clean surface texture will be produced. A rubber extrudate is obtained having a volume of 50%. In addition, the heat medium used in the present invention is completely inert as described above, and is not vulcanized with the heat medium attached to the surface of the extrudate. No post-processing is required, and productivity is improved.

Therefore, the method for continuously vulcanizing a rubber extrudate of the present invention can produce a rubber extrudate having a sponge rubber portion with a beautiful surface texture with good productivity.

<Examples> Examples carried out to confirm the effects of the present invention will be described below together with conventional examples.

The extrusion conditions and common vulcanization conditions for each example and conventional example are as follows.

(1) Extrusion conditions: Cross section of extrudate... Weatherstrip rubber material composition shown in Figure 3... Table 1, Extruder... Cylinder diameter: 90s φ, L/D: 1
6.

Discharge temperature: -80℃, discharge speed: 5 m, 7 minutes.

(2) Common vulcanization conditions: UHF vulcanization: output 2 kW (maximum output 5 kW) x time 1 minute, hot air vulcanization: 200°C x 4 minutes.

Then, continuous vulcanization was performed using the surface pre-vulcanization method and conditions shown in Table 2. Specific gravity of each extrudate after completion of vulcanization
The surface roughness was measured and the surface texture was visually determined. The test results are shown in Table 2, and it can be seen that the surface roughness of each example is much finer than that of the conventional example.

Furthermore, the density of the sponge rubber portion in each example is smaller than that in the conventional example, which indicates that the foaming gas escapes to the outside less.

Table 1 (Unit - parts by weight)

[Brief explanation of the drawing]

Fig. 1 is a schematic process diagram of the continuous vulcanization method of the present invention, and Fig. 2 is a schematic process diagram of the conventional continuous vulcanization method. Table J2 Figure 3 is a sectional view of a weather strip showing an example of an extruded product to which the present invention can be applied, Figure 4 is a sectional view of a weather strip showing another example, and Figure 5 is a cross-sectional view of a weather strip showing another example of an extruded product to which the present invention can be applied. FIG. 6 is a schematic sectional view showing an example of a sulfur tank, FIG. 6 is a schematic sectional view showing another example, and FIG. 7 is a schematic sectional view showing still another example. 1... Extruder, 3... U) IF vulcanized cypress, 5... Hot air vulcanization tank, 11... Surface pre-vulcanization tank, M... Extrudate, *Liquid temperature is 250°C , ○...Good, O...Very good 3...Sponge rubber part, L...Liquid heat medium, ■...Steam heat medium. Patent agent agent

Claims (1)

[Scope of Claim] A method applied to continuous vulcanization of a rubber extrudate having a sponge rubber part, which includes microwave vulcanization as a main vulcanization step during the vulcanization process, and includes microwave vulcanization as a main vulcanization step during the vulcanization step. A continuous vulcanization method including a step of surface pre-vulcanization by bringing at least the surface of the sponge rubber portion into contact with a heating medium prior to curing, wherein the heating medium includes perfluorotrialkylamine,
Continuous vulcanization of rubber extrudates, characterized by using a fluorinated inert liquid with a boiling point of 170° C. or higher, consisting of one or a mixture of two or more selected from perfluoroalkyltetrahydrofuran and perfluoropolyoxyalkylene, or its vapor. Method.