JPS5930180B2 - Rubber composition for vulcanization under atmospheric pressure and method for producing vulcanized molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a chlorosulfonated polyethylene composition that facilitates the removal of contained gas and is suitable for heat vulcanization under atmospheric pressure, and a vulcanized molded article made from the composition. Regarding the manufacturing method.

The gas contained in chlorosulfonated polyethylene (hereinafter referred to as Hypalon) is extremely difficult to remove, so even if Hypalon has been degassed and dried in a vacuum, when it is vulcanized at atmospheric pressure, Hypalon Hypalon foams due to the expansion of the gas remaining inside due to the heat during vulcanization.

By the way, according to research by the present inventors, when Hypalon is mixed with chlorinated polyethylene, the degassing properties are greatly improved, and Hypalon containing chlorinated polyethylene, which has been subjected to normal vacuum degassing treatment, can be heated and vulcanized under atmospheric pressure. It doesn't foam even if it does. In particular, when degassing and extruding using a shredding type twin-screw vent extruder described later as a vacuum degassing treatment method, the degree of degassing of the above composition is further improved, so that the degree of foaming during vulcanization is insulated. Reduce it to a level that can be applied to the production of electric wires. The present invention proposes a composition and a method for producing a vulcanized molded article, which are developed based on the above-mentioned new findings.

As the chlorosulfonated polyethylene (Hypalon) used in the present invention, various brands of Hypalon manufactured by DuPont, USA can be used.

As the chlorinated polyethylene, chlorinated polyethylene produced by reacting polyethylene with chlorine gas as a raw material can be used. In particular, randomly chlorinated rubbery chlorinated polyethylene having a chlorine content of 25% to 45% and a crystallinity of 10% or less is preferred. The amount of chlorinated polyethylene mixed is at least 5 parts per 100 parts by weight of Ipalon, and if the amount of chlorinated polyethylene is 5 parts or less, the above-mentioned drawbacks of Ipalon cannot be overcome.

The preferred mixing amount of chlorinated polyethylene is 5 parts to 100 parts, particularly 10 to 100 parts. As a vulcanizing agent,
Vulcanizing agents commonly used for Hypalon, such as metal oxide vulcanizing systems such as Resurge vulcanizing systems, magnesia vulcanizing systems, and peroxide vulcanizing systems, can be used. Examples of Surge vulcanization systems include Resurge/Sulfur Tetramethylthiuram Disulfide, Resurge/Sulfur Tetraethylthiuram Disulfide, Resurge/Dipentamethylenethiuram Tetrasulfide, and Resurge/Dibenzo. Thiacyl disulfide, Resurge/Stevilite resin (trade name of Hercules Powder Co., Ltd.), and vulcanization systems in which nickel dibutyl dithiocarbamate and m-phenrene bismaleimide are added to these systems; Examples include one or a combination of two of the following vulcanization systems. Examples of magnesia vulcanization systems include magnesia/dipentamethylenethiuram tetrasulfide, magnesia/pentaerythritol, and vulcanization systems in which nickel digityl dithiocarbamate and dibenzothiacyl disulfide are added to these systems, and furthermore, Examples of peroxide vulcanization systems that can be used as combinations of vulcanization systems include dicumyl peroxide,
Examples include vulcanization systems in which a vulcanization aid such as triaryl cyanurate or ethylene glycol acrylate is used in a peroxide such as 2.5-bis-t-butylperoxy-2.5-dimethylhexane. The amount of the vulcanizing agent used is about 1 to 30 parts per 100 parts of Hypalon, and the composition of the present invention can be mixed and manufactured using a common kneader such as a Niroll. During this mixing, reinforcing agents, fillers, process oils, softeners, colorants, anti-aging agents, vulcanization aids, and vulcanization accelerators commonly used in rubber compositions may be added as necessary. . Particularly preferred is the use of reinforcing agents and fillers (eg carbon black, clay, talc, calcium carbonate, silica, etc.). Although the composition of the present invention can be sufficiently degassed by a vacuum degassing treatment means such as a known vacuum vent extruder, it can be degassed by using a shredding twin-screw vent extruder as described below. If this method is adopted, deaeration can be performed to a higher degree as described above.

Hereinafter, a method for extrusion molding and vulcanization of the composition of the present invention using a shredding twin-screw vent extruder will be described in detail with reference to the drawings.

The figure is a cross-sectional view of an example of a shredding twin-screw vent extruder, in which a rubber composition is extruded into a vacuum degassing chamber 2 by a first extruder 1. Immediately after the extrusion port 3 of the first extruder, a rotary cutter 14 that rotates at high speed is installed to shred the extruded rubber composition. The reduced pressure degassing chamber is evacuated through the exhaust hole 5 and is constantly maintained in a vacuum or reduced pressure state.
The rubber composition whose surface area has been increased by the shredding is rapidly deaerated and dried in the chamber 2, and reaches the supply port 7 of the second extruder 6 by gravity, where it is extruded by the second extruder. It goes without saying that the higher the degree of reduced pressure or degree of vacuum in the reduced pressure deaeration chamber, the better, but usually a degree of several MuHg to several dozen MmHg is sufficiently effective. The temperature may be room temperature, but as long as the rubber does not scorch, the temperature should be as high as possible, for example 50 to 1
If the temperature is maintained at 00°C, the degree of degassing and drying will increase. A rotating cutter is several hundred to several thousand R. p. Although it is operated in the area of m,
1000~3000r. m. p. It is practical to drive at a certain level. A conventional rubber extruder can be used for both the first extruder and the second extruder. Since the rubber composition extruded in this way is sufficiently deaerated and dried, it does not substantially foam even when heated and vulcanized under atmospheric pressure (for example, by the LCM method), and therefore cannot be vulcanized by ordinary vulcanization. It can be put to practical use as a sulfur molded product. Examples and Comparative Examples
Various Ipalon compositions shown in the table were extruded into round rods with an outer diameter of 20 mu, and immediately introduced into a mixed salt bath kept at 200°C and heated and vulcanized.

The L/D of the first extruder is 12, the L/D of the second extruder is 8,
The volume of the vacuum degassing chamber is approximately 301 cm. Rotating cutter one is 4
It is a single blade. The operating conditions of each part during the extrusion experiment are as follows. 1st extruder: Set temperature approximately 60°C Screw rotation speed 10r. p. m. 2nd extruder: Set temperature approximately 50°C Screw rotation speed 14r. p. m. Number of revolutions of rotating cutter: 1200r. p. m. Decompression and deaeration chamber: degree of vacuum 5-10m77! Hg temperature: approximately 60°C Table 1 shows the cross-sectional state of the vulcanized product and the operating conditions of the extruder.

[Brief explanation of the drawing]

Figure 1 is a sectional view of one example of an extruder used in the present invention, in which 1 is a first extruder, 4 is a high-speed rotating cutter, 2 is a vacuum drying chamber, and 6 is a second extruder.

Claims (1)

[Scope of Claims] 1. A rubber for vulcanization under atmospheric pressure, comprising chlorosulfonated polyethylene, at least 5 parts by weight of chlorinated polyethylene and a vulcanizing agent per 100 parts by weight of the chlorosulfonated polyethylene. Composition. 2. A vulcanizable rubber composition comprising chlorosulfonated polyethylene, at least 5 parts by weight of chlorinated polyethylene and a vulcanizing agent per 100 parts by weight of the chlorosulfonated polyethylene is transferred from a first extruder into a vacuum degassing chamber. extruded into,
The extruded rubber composition is shredded by a high-speed rotating cutter immediately after the extrusion port of the first extruder, and the shredded rubber composition is supplied to the supply port of the second extruder that communicates with the vacuum degassing chamber. A method for producing a vulcanized rubber molded product, which is characterized by extrusion molding using two extruders and then heating and vulcanization under atmospheric pressure.