JP2530535B2 - Method for manufacturing fluororubber molded products - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluororubber molded article, and more particularly to a method for producing a fluororubber molded article having low surface tackiness (called tackiness).

[0002]

2. Description of the Related Art Conventionally, since fluororubber has excellent heat resistance and chemical resistance, it has been used for gaskets for ducts used for intake / exhaust systems of high-temperature gas, or high-temperature liquid or chemical transfer systems. Used as a material for packing and hoses for piping. However, since fluororubber itself has adhesiveness, packing or gasket formed by molding fluororubber (abbreviated as fluororubber packing, etc.)
Since it also has adhesiveness, there is a drawback in that workability is poor when the packing or the like is attached to a pipe joint or the like.

Further, when the fluororubber is molded into a packing or the like, the fluororubber is put into a mold, heated, and primary-crosslinked to be cured to obtain a molded product. In this case, since the fluororubber has adhesiveness, it is not only difficult to remove the burrs fixed to the mold, but also when the molded articles are secondarily crosslinked and further cured, the molded articles adhere to each other. In addition, when packing and shipping molded products (products), the product supply efficiency such as fluororubber packing will be inferior due to blocking such as products sticking to each other, increasing product manufacturing cost. There was a drawback that

Further, the fluororubber packing and the like have a drawback that the cost of mounting the packing is increased because it is difficult to automate or robotize the packing due to its adhesive property. Therefore, as a method for preventing the surface tackiness (surface tackiness) of a fluororubber molded product (simply referred to as a molded product), a method of coating the surface of the molded product with a fluororesin has been put into practical use.

However, since the above method may cause coating unevenness, it is not possible to impart a stable anti-adhesive effect to the molded product, and a coating step is required, so that the processing efficiency of the molded product is improved. As a result of the decrease, there is a drawback that the molding cost is increased.

Although a chemical treatment method has been attempted in which the surface of a molded article is treated with a chemical substance such as sulfuric acid, a halide or a secondary amine compound to prevent surface tackiness, stable surface tackiness has been tried. In addition to the fact that it is not possible to impart a property prevention effect to the molded product, and because it handles chemical substances, it is difficult to put it into practical use because it requires treatment of chemical substances storage equipment, waste liquid, etc. or safety and hygiene management. there were.

On the other hand, a method of preventing the tackiness of a molded article by treating the surface of the molded article with a polyhydroxy compound (Japanese Patent Laid-Open No. 63-291930) has also been proposed.
It delivers good results. In this method, a molded article is immersed in a solution of a polyhydroxy compound used as a cross-linking agent for fluororubber and an accelerator in an organic solvent, and then the molded article is heated to eliminate surface tackiness. is there. That is, the polyhydroxy compound accelerates the crosslinking of the fluororubber on the surface of the molded product, cures only the extremely surface layer of the molded product, and loses the surface tackiness.

However, in the above method, it is difficult to control the crosslinking of only the extreme surface layer of the molded product, and the inside of the molded product is cured to maintain the elasticity of the fluororubber molded product while maintaining the surface. It often happens that the purpose of preventing tackiness cannot be achieved. Therefore, there is a drawback that it is not always appropriate to use the above-mentioned treatment method for packing or the like which requires elasticity of the surface for sealing or the like. Further, as a method of preventing the surface tackiness of the molded product, there is a method of adding and kneading a silicone-based internal additive or a powder of tetrafluoroethylene, but there is a drawback that the intrinsic heat resistance and chemical resistance of fluororubber are impaired. It was

[0009]

Therefore, as a result of intensive studies to solve the above-mentioned drawbacks, the present inventor has found that a molded product formed using an aqueous solution of perfluoroalkylphosphoric acid ammonium salt as a releasing agent is an aqueous solution of Lewis acid. The present invention has been found out that the occurrence of surface tackiness can be prevented and a good fluororubber molded article with less tackiness can be easily produced by immersing in the above. Therefore, it is an object of the present invention to provide a novel method for producing a fluororubber molded article that has no surface tackiness and a small tackiness.

[0010]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
A method for producing a fluororubber molded article by applying a release agent to the inner surface of a mold, inserting fluororubber, and immersing the molded article obtained by heat molding into a Lewis acid aqueous solution, wherein the release agent Is a perfluoroalkylphosphoric acid ammoniu salt aqueous solution, which is achieved by a method for producing a fluororubber molded article.

The release agent used in the present invention has the following general formula:

Embedded image (However, Rf is a perfluoroalkyl group) is an aqueous solution of a perfluorophosphoric acid ammonium salt (abbreviated as a perfluorophosphate aqueous solution).

The concentration of the aqueous solution of perfluorophosphate used in the present invention is not particularly limited, but from the viewpoint of enhancing the effect of the next step of dipping the molded product in Lewis acid, it is 0.01 to 5% by weight is preferable,
In particular, it is preferably 0.1 to 3% by weight.

If the concentration of the perfluorophosphate aqueous solution is too high, the mold and the like will be contaminated quickly by the release agent, so that it is necessary to increase the number of times of cleaning the mold, resulting in a decrease in molding processing efficiency. Become. On the other hand, if the concentration is too low, the releasing effect becomes poor, and the work of taking out the molded product from the mold becomes complicated, which is not preferable.

In the present invention, the method of applying the aqueous solution of perfluorophosphate to the inner surface of the mold is not particularly limited, and known coating means used in ordinary rubber molding can be used. From the viewpoint of preventing uneven coating and obtaining a uniform coating film, the above-mentioned coating method preferably uses a spray air gun and coats at a constant speed from a constant distance.

The fluororubber used in the present invention is a highly fluorinated and elastic copolymer. Specific examples of the fluororubber include, for example, hexafluoropropane, pentafluoropropane, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether) and the like. Examples thereof include copolymers obtained by copolymerizing one or more selected from the above with vinylidene fluoride.

In the present invention, it is particularly preferable to use a binary copolymer of vinylidene fluoride and hexafluoropropane or a ternary copolymer of vinylidene fluoride and tetrafluoroethylene and hexafluoropropane.

In the present invention, the fluororubber is inserted into the mold and then heated, and the crosslinking reaction of the copolymer is promoted by the crosslinking agent to be solidified, whereby it is molded into a predetermined shape.
The cross-linking agent used in the present invention is not particularly limited, and a known cross-linking agent used for ordinary die molding can be used. The cross-linking agent, for example,
Examples thereof include amines, polyols and peroxides.

If necessary, a crosslinking aid, an accelerator, an acid acceptor, a filler, a plasticizer, a lubricant and the like can be appropriately added. Further, the crosslinking temperature and the crosslinking time are appropriately adjusted depending on the type or amount of the crosslinking agent used.

The Lewis acid aqueous solution used in the present invention is not particularly limited, and hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, aluminum chloride, ferric chloride, stannic chloride, boron trifluoride, carbonic acid. An aqueous solution of phosphoric acid or the like (referred to as a treatment liquid) or the like can be used. Among the above Lewis acids, it is preferable to use an organic acid such as acetic acid or formic acid, or a metal oxide of carbonic acid or ferric chloride from the viewpoint of safe handling.

In particular, it is not necessary to wash and remove unreacted acid remaining on the surface of the molded product after the dipping treatment and ammonium salt which is a by-product reacted with ammonium salt of perfluorophosphoric acid which is a release agent. From the viewpoint, it is more preferable to use an organic acid such as acetic acid or carbonic acid which is easily decomposed or volatilized by heating.

If the concentration of the treatment liquid is 1% by weight or less, the treatment effect is not sufficient, and if it is 50% by weight or more, a washing step for removing the Lewis acid may be required. % Is preferable. Since the surface of the molded product taken out from the mold has thin burrs etc. that have stickiness and there is a risk of blocking, it is preferable to perform immersion treatment immediately after removing the molded product from the mold. Depending on the shape or property of the above, the immersion treatment may be performed after the completion of the secondary crosslinking reaction after deburring.

The mold used in the present invention is not particularly limited, and a known mold used for usual rubber molding can be used. Further, conventionally, it has been difficult to bond the surface-treated fluororubber, but since the fluororubber molded article obtained by the present invention can be bonded by an epoxy adhesive, its application range is extremely wide. .

[0023]

As described above in detail, in the method for producing a fluororubber molded article of the present invention, the release agent layer (modified) formed by the ammonium perfluorophosphate salt reacting with the surface of the molded article and sticking thereto is formed. Layer) is treated with a Lewis acid to make it a non-adhesive layer, so that it is extremely easy to produce a good fluororubber molded product with little surface tackiness while maintaining the elasticity inherent to fluororubber. it can.

[0024]

The present invention will be described in more detail with reference to the following examples.
The present invention is not limited to this. In addition, "part" indicating the addition amount indicates "part by weight". Fluorine rubber compound used in Examples Fluorine rubber compound A (amine type) The components shown in Table 1 below were blended to obtain a fluorine rubber compound A.

[Table 1] ─────────────────────────────────── Fluorine rubber (Viton B-50: DuPont, USA) Product name) 100 parts MT carbon (Thermax MT: product name manufactured by Harbor Company) 10 parts DIAC No3 (product name manufactured by DuPont, USA) 3 parts MgO 15 parts ──────────── ────────────────────────

Fluororubber Compound B (Polyol-based) The components shown in Table 2 below were blended to obtain a fluororubber compound B.

[Table 2] ─────────────────────────────────── Fluorine rubber (Florel 3009: Sumitomo 3M Limited) Brand name) 100 parts MT carbon (Thermax MT: trade name manufactured by Harbor Company) 10 parts MgO 3 parts Ca (OH) ₂ 3 parts ────────────────── ─────────────────

Fluororubber Compound C (Peroxide) A fluororubber compound C was obtained by mixing the components shown in Table 3 below.

[Table 3] ─────────────────────────────────── Fluorine rubber (Daiel G801: manufactured by Daikin Industries, Ltd. Trade name) 100 parts MT carbon (Thermax MT: trade name manufactured by Harbor Company) 10 parts Taik (trade name manufactured by Nippon Kasei Co., Ltd.) 3 parts Perhexa 2-5B (trade name manufactured by NOF Corporation) 15 Department ───────────────────────────────────

Examples 1-3. Ammonium perfluorophosphate (X70-814:
Trade name of Shin-Etsu Chemical Co., Ltd.) 1% by weight aqueous solution,
The mold release agent was applied by spraying uniformly on the inner surface of the mold from a distance of 30 cm. Next, the fluororubber compounds A to C were inserted into the respective molds, heated at 170 ° C. for 10 minutes to be crosslinked, and molded into rubber sheets A to C each having a thickness of 2 mm. Each of the obtained rubber sheets had surface tackiness.

Next, each of the obtained rubber sheets A to C was
Two sheets of the same sheet were superposed on each other and then compressed so that the thickness after compression was reduced by 25% and left at 80 ° C. for 48 hours. Each of the obtained laminated sheets was cut into a width of 2 cm, and a peeling force test was performed by the 180-degree peeling test method to evaluate the surface tackiness of the rubber sheet. The results are as shown in Table 4.

Next, the rubber sheet before being overlaid 10
After soaking in a 1% by weight acetic acid aqueous solution for 1 hour,
Dry for 0 minutes (called acetic acid treatment), and in the same manner as above,
A laminated sheet was prepared and a peel test was conducted. The results are as shown in Table 4. Further, the above-mentioned acetic acid-treated rubber sheet was heated at 230 ° C. for 24 hours for secondary cross-linking (referred to as secondary cross-linking treatment), and a peeling test similar to the above was carried out to evaluate surface tackiness. The results are as shown in Table 4.

[0030]

[Table 4] The above results demonstrate that the molded article produced by the production method of the present invention has sufficiently low tackiness without secondary crosslinking.

Example 4 A rubber sheet was prepared in the same manner as in Example 2 except that the 10 wt% acetic acid aqueous solution was replaced with the aqueous solution shown in Table 5 below, and a peeling test was conducted.
The same result was obtained.

[Table 5]

Further, the obtained rubber sheet was adhered to a stainless steel plate using an epoxy adhesive (Hybon 3590: trade name of Hitachi Chemical Polymer Co., Ltd.), and an adhesive strength test was conducted to peel off the rubber sheet. When it was done, cohesive failure was observed that it did not peel off from the adhesive surface of the sheet rubber and peeled from the part where the adhesive aggregated, and it was confirmed that the adhesiveness between the rubber sheet and the epoxy adhesive was extremely good. .

Comparative Example 1. Example 2 except that a 10 wt% aqueous solution of an emulsion type fluorine release agent (Dynamer 5158: a trade name of Sumitomo 3M Co., Ltd.) was used as the release agent instead of the 1 wt% aqueous solution of perfluorophosphoric acid salt. A rubber sheet was obtained in exactly the same manner. The rubber sheet had tackiness.

The obtained rubber sheet was immersed in a treatment liquid containing 10% by weight of bisphenol AF and 2% by weight of benzyltriphenylphosphonium chloride in acetone as a solvent for 30 minutes, dried at room temperature for 24 hours, and then dried at 200 ° C.
Heated for 24 hours. The surface adhesion and physical properties of the obtained rubber sheet were tested, and it was found that the surface adhesiveness was small and good, but the physical properties were inferior, and it could not withstand use such as packing. The results are as shown in Table 6.
The epoxy adhesive used in Example 4 was used to adhere the rubber sheet to the stainless steel plate in exactly the same manner as in Example 4, but it could not be adhered at all.

[0035]

[Table 6]

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Claims (1)

(57) [Claims] 1. A method for producing a fluororubber molded article by applying a release agent to the inner surface of a mold, inserting fluororubber, and immersing the molded article obtained by heat molding into a Lewis acid aqueous solution. The method for producing a fluororubber molded article, wherein the release agent is an aqueous solution of perfluoroalkylphosphoric acid ammonium salt.