JPH1052885A - Rubber molding of two-layer structure and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat resistance and chemical resistance by constituting an inner layer by fluororubber having hydrogen in a molecule, and forming an outer layer in a two-layer structure for enclosing the outer layer with perfluororubber without gap. SOLUTION: In an O-ring constituted at an inner layer by a fluororubber of vinylidene fluoride and at an outer layer by a perfluororubber, an unvulcanized vinylidene fluoride rubber compound uniformly mixed with carbon, a vulcanizer and other additive and an unvulcanized perfluororubber compound mixed in the same manner are prepared, and a string-like material in which a vinylidene fluororubber compound is disposed on an inner layer and an unvulcanized perfluororubber compound is disposed in a uniform thickness on its outer periphery is prepared. The string-like material is cut, and set to an O-ring compression mold. This mold is compression vulcanized by a hot plate press held in advance to a vulcanizing temperature, fusion-bonded at its ends, and simultaneously the vinylidene fluoride rubber and perfluororubber are vulcanized to obtain the O-ring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a special rubber molded article having excellent heat resistance and chemical resistance. For example, the present invention relates to a molded article of a rubber elastic body such as fluororubber and a molding method thereof. Various types of fluororubbers have been put into practical use, but can be roughly classified into two types. One type is a molecule whose molecule is mainly composed of carbon, fluorine and hydrogen, and is a copolymer of vinylidene fluoride and propylene hexafluoride or vinylidene fluoride and propylene hexafluoride and ethylene tetrafluoride. Terpolymers, copolymers of ethylene tetrafluoride and propylene, etc. are well known and industrially used. For the purposes of the present invention, this type of rubber is referred to as fluororubber having hydrogen in the molecule. The other is a rubber-like material composed of carbon, fluorine, oxygen and a small amount of iodine or bromine. The copolymer of ethylene tetrafluoride and perfluorovinyl ether is well known. is called. In the present invention, the term perfluoro rubber is used to refer to this type of rubber. In recent years, perfluoro rubber has been marketed as an elastic body having particularly excellent properties, and processed products thereof have begun to be used in various fields.

[0002] As one of such processed products, there are various O-rings. The fields used are the semiconductor industry,
It is widely used in the chemical industry, medical and pharmaceutical fields, etc. In the field of semiconductors, extremely corrosive acids and alkalis are used in the process of manufacturing semiconductor products, and harmful gases are used. Therefore, a sealing material having excellent corrosion resistance is demanded.

In the chemical industry and the medical and pharmaceutical fields, highly polar organic solvents such as ketones such as acetone and methyl ethyl ketone, amides such as dimethylformamide, amines such as ethylenediamine and triethylamine, and furans such as tetrahydrofuran and 2-methyltetrahydrofuran. And the like are commonly used. Accordingly, there is a demand for a sealing material, particularly an O-ring, having resistance to these organic solvents.

The present invention relates to the processing of perfluoro rubber and vinylidene fluoride-based fluoro rubber excellent in heat resistance and chemical resistance, and a two-layer rubber molding in which these rubbers are combined in a complex manner. Goods.

[0005]

2. Description of the Related Art Perfluoro rubber, which has the highest chemical resistance and heat resistance among the elastic materials currently available on the market, is relatively new, but several processing methods have already been proposed. , O-rings and the like are used for sealing. However, this rubber material is extremely expensive, and its use range must be limited. Therefore, a high-performance and less expensive sealing material is desired, and some attempts have been made. As one of them, a structure in which the outer periphery of a silicon rubber O-ring is wrapped with a fluororesin tube has already been put into practical use. However, since the outer periphery is a resin tube, the O-ring may break due to compression application during use. However, it has a disadvantage that creep deformation is apt to occur in long-term compression. In other words, this kind of O-
The ring has good chemical resistance but poor sealing performance. The heat resistance is comparable to that of silicon rubber, and the fluororesin does not contribute at all in this respect.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have been studying to develop a sealing material which is less expensive in terms of cost while maintaining the performance of a perfluoro rubber in terms of chemical resistance. Various studies were added. As a result, the inner layer portion is made of a fluorine-containing rubber having hydrogen in the molecule, which is relatively inexpensive but slightly inferior in chemical resistance, for example, a vinylidene fluoride-based fluororubber, and its periphery is completely wrapped with perfluororubber. It has been found that by forming a layer structure, an inexpensive sealing material having excellent chemical resistance can be obtained, and the present invention has been completed.

[0007]

The gist of the present invention will be described with reference to an O-ring having an inner layer made of vinylidene fluoride fluororubber and an outer periphery made of perfluororubber. An unvulcanized vinylidene fluoride-based fluororubber compound in which carbon, vulcanizing agent and other additives are uniformly mixed, and an unvulcanized plastic in which carbon, vulcanizing agent and other additives are uniformly mixed A fluororubber compound is prepared, and a vinylidene-based fluororubber compound is provided in an inner layer portion, and a string-shaped body having a predetermined thickness is provided in which an unvulcanized perfluororubber compound having a uniform thickness is disposed on the outer peripheral portion.

[0008] This string is cut and set in a compression mold for O-ring of a predetermined size. In this case, it is preferable to make an oblique cut at 45 degrees so that both ends of the cord-like body are overlapped with each other. By compressing and vulcanizing with a hot plate press that has been held at the vulcanization temperature in advance, the mold on which the string-like body has been set is fused together at the same time, and the vinylidene fluoride rubber in the inner layer is also The perfluoro rubber on the outer periphery is also vulcanized. The vulcanized O-ring removed from the mold can be subjected to secondary vulcanization in a normal pressure heating oven. When both ends are fused, there is a possibility that the vinylidene fluoride-based fluororubber in the inner layer portion may protrude to the surface and reverse to the perfluororubber layer. It is also a good method to use a short perfluoro rubber string as a splice to avoid this.

[0009]

A method of manufacturing a cord-like body whose inner layer is made of an unvulcanized vinylidene fluoride fluororubber compound and whose outer periphery is made of an unvulcanized perfluororubber compound will be described. FIG. 1B shows an extrusion die composed of a cylinder 1, a detachable die 2, and a piston 3 which can move up and down in the cylinder 1. FIG. 2 shows a blade for punching rubber. The blade (b) can be inserted into the blade (a) without a gap, but a constant gap (rr ′) is provided at the cutting edge.
It is designed to be opened. First, the unvulcanized perfluoro rubber compound is made into a sheet of a certain thickness,
The blade (a) and the blade (b) are fitted and set on a sheet,
Pressing down (b) cuts out the rubber sheet and then pressing down (a) gives a donut-shaped sheet. The required number of donut-shaped unvulcanized perfluoro rubber compounds is prepared. Next, the same number of disc-shaped unvulcanized vinylidene fluoride-based rubber compounds are punched out from a sheet having the same thickness as the above sheet, using only the punching blade (b). This disc-shaped compound is fitted into the hole of the donut-shaped perfluoro rubber compound. When this is inserted into the cylinder 2 of FIG. 1 in a stacked state, a rod is obtained in which the vinylidene fluoride-based rubber compound is wrapped in the inner layer portion and the periphery thereof is wrapped with the perfluoro rubber compound. This dice 1
3 is set on the pedestal B as shown in FIG. 3 and the piston is lowered by the compressor A to uniformly surround the vinylidene fluoride rubber compound on the inner layer and the perfluoro rubber compound on the outer periphery. A cord having a two-layer structure can be obtained.

Another method for producing a two-layer unvulcanized cord state is now disclosed. 4C and 4D are screw extruders, and E is a so-called two-color extrusion die. This mold
FIG. 5 shows a top view and a cross-sectional view of the die component 7,
8, 9, and 10 are assembled. From the screw extruder D, a vinylidene fluoride rubber compound is supplied to a two-color extrusion die, and a conical die k covering the die parts 8, 9, and 10 is filled with the compound. .

On the other hand, the perfluoro rubber compound is supplied from the screw extruder C, passes through the flow path n, passes through the die parts 9 and 8 to the extrusion die, and reaches the die part 7. The die part 7 is provided with a flow path i divided in two directions,
The perfluoro rubber compound reaches the nozzle m through this flow path. At the center of the nozzle m, a vinylidene fluoride-based rubber compound that has passed through the die k is extruded, and a perfluoro rubber is extruded around the perimeter from the nozzle in a form wrapping the outer periphery. Thus, a two-layer extrudate having a predetermined size is obtained.

In the above method, it is preferable to control the temperature of both the screw type extruder and the two-color extrusion die to 70 ° C. to 90 ° C. However, it is necessary to select the screw rotation speed of the extruder according to the thickness of the extrudate string, the structure of the extrusion die, the required cross-sectional area ratio of the inner and outer layers, the extrusion speed, and the like. This method takes time and effort to determine the conditions, but once the conditions are determined, it is preferably used for relatively large-scale production.

[0013]

Embodiment 1 Inner diameter 30 mm, outer diameter 80 mm, length 120
A metal cylinder having a length of 120 mm and a piston having a length of 120 mm capable of smoothly moving up and down closely in the cylinder were prepared. A die 1 as shown in FIG. 1 (c) was attached to the tip of the cylinder to form an extrusion die. In terms of main dimensions, the die entrance diameter is 30 mm, which is equal to the piston inner diameter, the exit diameter is 3.3 mm, and the land length is 5 mm. The die angle is about 20 degrees. All of these parts were chrome plated. The rubber materials used are Daiel Perfluoro GA-55 and Daiel G-902 (trade names, manufactured by Daikin Industries, Ltd.), both of which are uniformly compounded with a peroxide-based vulcanizing agent, carbon powder and other additives. One used. Each of the unvulcanized rubbers was formed into a sheet having a thickness of 3 mm, and 25 disks having a diameter of 30 mm were punched out of the sheet of Daiel G-902 using a punching blade shown in FIG. 2B. On the other hand, Daiel Perfluoro GA-
From the 55 sheets, the same number of donut-shaped sheets having an outer diameter of 30 mm and an inner diameter of 20 mm were punched out by combining the punching blades shown in FIGS. 2A and 2B. The disk-shaped dial G
-902 was inserted into a donut-shaped inner layer portion, and filled in a cylinder 2 of an extrusion die in a stacked state. In order to prevent the flow from being disturbed during the extrusion, the inside of the die 1 was previously filled only with the DAIEL G-902.

A band heater was attached to the outer periphery of the cylinder, and the temperature of the cylinder was maintained at 90 ° C. by adjusting the voltage with a slide rack. The cylinder was set in a hydraulic universal tester (a universal test machine manufactured by Shimadzu Corporation) as shown in FIG. By extruding while adjusting the temperature of the piston to fall to 50 mm / min, the diameter is about 4.3 to 4.5 m.
Thus, an unvulcanized cord having a smooth skin of m was obtained. About 15
Grams of unvulcanized rubber remained on the die. The string was cut and observed with a magnifying glass.
It was confirmed that it had a layer structure. Separately prepared O-pieces of 24 mm inner diameter and 4.2 mm wire diameter prepared separately
Both ends were cut into the groove of the ring mold at 45 degrees and set in a superposed state. The plates were pressed at 180 ° C for 20 minutes with a hot plate press, and then subjected to secondary vulcanization at 200 ° C for 4 hours in an electric furnace. went. Daiel G-902 and G thus obtained
The O-ring having a two-layer structure of A-55 was immersed in acetone at room temperature, but no change was observed even after 10 hours. For comparison, an O-ring made by the same method using only G-902 was immersed in acetone.
After the time, there was a 30% weight increase and a dimensional increase was noted.

[0015]

Example 2 For the purpose of clearly confirming the two-layer structure of the inner layer portion and the outer peripheral portion, almost the same experiment as in Example 1 was performed. The difference from Example 1 is that the formulation of Daiel G-902 was white. The white blend is a blend of silicon oxide and barium carbonate instead of carbon. O created
-The ring was cut and the cross section was observed under magnification. A copy of the photograph, magnified about 10 times, is shown in FIG. It is clear that the white inner layer is surrounded by black perfluoro rubber without any gap. Adhesion of the boundary phase was extremely high, and peeling between different kinds of rubber could not be recognized. No swelling was observed after 20 hours of immersion in acetone for the two-layer O-ring.

[0016]

According to the present invention, a rubber molded article having a two-layer structure in which the inner layer portion is made of inexpensive fluoro rubber and the outer layer portion is wrapped with an expensive but high-performance perfluoro rubber without gaps has a high performance. In particular, it can be provided at low cost, even though its chemical resistance is comparable to that of perfluororubber. The present invention uses a circular O
-Not limited to molded products such as rings,
It can also be effectively used as a sealing material having an irregular cross section, for example, a packing for an electric furnace door. To obtain a two-layer profile extrudate, the die disclosed in detail in FIG. 5 can be effectively used by making some modifications.

[Brief description of the drawings]

FIG. 1 is an extrusion die for molding a rubber molded product having a two-layer structure according to the present invention.

FIG. 2 is a plan view showing a punching blade.

FIG. 3 is a diagram in which an extrusion die is attached to a compressor.

FIG. 4 is a conceptual diagram of manufacturing a two-layer structure using two screw extruders.

FIG. 5 is a detailed view of a dice for obtaining a two-layer structure.

FIG. 6 is a diagram showing a cross-sectional shape of an O-ring obtained in Example 2.

[Explanation of symbols]

 Reference Signs List 1 die 2 cylinder 3 piston 4 band heater 5 rubber compound 6 extrusion cord 7 die component 8 die component 9 die component 10 die component A compressor B pedestal C screw extruder D screw extruder E two-color extrusion die r punching blade Diameter r 'Diameter of punching blade i Flow path k Dice m Nozzle n Flow path

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // B29K 105: 24 B29L 9:00 31:26

Claims (4)

[Claims] 1. A rubber molded product having a two-layer structure, wherein an inner layer portion is made of a fluororubber having hydrogen in a molecule, and an outer layer portion is wrapped with a perfluoro rubber without gaps. 2. An O-ring having a two-layer structure, wherein an inner layer portion is made of fluororubber having hydrogen in a molecule, and an outer layer portion is wrapped with perfluoro rubber without gaps. 3. A long rubber molded product having an irregular cross section, wherein an inner layer portion is made of fluorine rubber having hydrogen in a molecule, and an outer layer portion is wrapped with perfluoro rubber without gaps. Characteristic two-layer structure. 4. A string-like body whose inner layer is made of an unvulcanized compound of fluororubber having hydrogen in the molecule and whose outer layer is made of an unvulcanized compound of perfluororubber is extruded. 3. The method for producing an O-ring having a two-layer structure according to claim 2, wherein the inner and outer layers are simultaneously vulcanized by being set in a ring mold and hot-pressed.