JPH08269249A - Joint sheet and its production - Google Patents

Abstract

PURPOSE: To obtain a joint sheet improved in mechanical strengths by mixing a fibrous material, an acrylonitrile-butadiene rubber, a carbon black. and sulfur, forming the mixture into a sheet, and thermally treating the sheet. CONSTITUTION: A mixture is prepd. by mixing an acrylonitrile-butadiene rubber in an amt. of 15-30wt.% of the mixture, a carbon black in an amt. of 30-300wt.% of the rubber, a fibrous material in an amt. of 10-40wt.% of the mixture, and sulfur or an organosulfur compd. in an amt. of 1.0-5.0wt.% (in terms of sulfur) of the rubber. The mixture is put into between a pair of rolls, a hot roll at about 150 deg.C and a cold roll at about 20 deg.C, to vulcanize and simultaneously thermally calender the mixture. The resulting sheet is thermally treated in an autoclave at 100-210 deg.C for 60-240min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a joint sheet used as a gasket at a joint portion of pipes or the like in a refrigerating apparatus, etc. The present invention relates to a joint sheet that is useful for a refrigeration system that uses an alternative CFC or an ester-based lubricating oil used together with the alternative CFC.

[0002]

2. Description of the Related Art Conventionally, asbestos joint sheets made of asbestos fibers (abbreviated as A.J / S) have been widely used as joint sheets. Because asbestos fibers have a unique shape and have excellent heat resistance, we make use of these characteristics to produce asbestos joint sheet, and then process that sheet into punched gaskets to make water, oil, air, It has been used as a gasket for piping and equipment such as steam. However, the asbestos fiber used for the asbestos joint sheet is a natural product, and there is a concern that the resources will be exhausted, and the use of asbestos fibers tends to be restricted worldwide due to environmental hygiene problems. Therefore, recently, asbestos fiber is not used at all,
A joint sheet is used in which an inorganic fiber other than asbestos fiber and / or an organic fiber, or a filler and the like are compounded with a rubber as a binder. This joint sheet is an asbestos-free joint sheet or a non-asbestos joint sheet (hereinafter NA.J.
Abbreviated as / S. ), Is widely used.

Further, although NA.J / S is used for various pipes and equipment, especially for NA.J / S used for compressors of refrigerators and air conditioners, there are refrigerants of CFC and refrigerating machine oil. In order to seal the mixed system, higher sealing property is required as compared with NA / J / S used in pipes and equipment for water, oil, air, water vapor and the like. Furthermore, this NA / J / S for refrigerating equipment does not cause blowout even if the sheet is used while being subjected to vibration while the refrigerator is operating. Greater strength is also required. Therefore, especially for refrigeration equipment NAJ
/ S rubber has high polarity, high vulcanization degree, and good oil resistance acrylonitrile butadiene rubber (hereinafter,
Abbreviated as NBR. ) Is the mainstream. The inventors of the present invention have also been intensively researching NA / J / S for refrigerating machines by adjusting the ratio of NBR, fibrillated fiber, vulcanizing agent, and active fine particles such as carbon black. It has been found that NA · J / S with good characteristics can be obtained.

NA / J / S using this NBR is an NBR (or powder NB) obtained by swelling a fiber material, a filler (carbon black, etc.) and a rubber chemical such as a vulcanizing agent in a solvent.
R or NBR latex with solvent added) is sufficiently kneaded with a Henschel mixer or the like, and the kneaded material is put between a pair of rolls consisting of a hot roll (about 150 ° C.) and a cold roll (about 20 ° C.). Then, the NBR is vulcanized together with the evaporation of the solvent while laminating the kneaded material on the hot roll side, and finally the sheet material laminated on the hot roll side is peeled off.

[0005]

However, in the conventional method for manufacturing NA / J / S, the vulcanization treatment of NBR is carried out in the heat rolling step, but at that time, a thermal gradient occurs in the sheet thickness direction. In some cases, sufficient mechanical strength and oil resistance may not be obtained due to blooming that deteriorates the surface properties of the sheet, uneven vulcanization, and insufficient vulcanization. .

On the other hand, in recent years, due to the problem of ozone layer depletion, specific CFCs have been subject to use restrictions worldwide, and alternative CFCs have been developed and used in place of these CFCs. Along with that, ester-based lubricating oil is used instead of conventional mineral oil as refrigerating machine oil, but this ester-based lubricating oil has a stronger action of swelling rubber than mineral oil, and NBR, which has excellent oil resistance, can be used for a long period of time. It swells due to the contact over. Then, due to swelling, rubber chemicals etc. in NA / J / S are eluted, and this eluted component flows in the piping of the refrigeration system together with the ester lubricating oil, resulting in clogging of thin tubes and deterioration of the ester lubricating oil. Problems occur in the refrigeration system. Since this swelling depends on the vulcanization degree, it becomes more remarkable when the vulcanization degree is insufficient as described above.

The object of the present invention is also suitable for a pipe gasket of a refrigerating apparatus which does not have the above-mentioned drawbacks and has excellent mechanical strength even in a refrigerating apparatus using a CFC substitute and an ester type lubricating oil. It is to provide NA / J / S.

[0008]

The above-mentioned object of the present invention is to:
A composition comprising a fiber material, rubber, a rubber chemical, a filler, etc., wherein the acrylonitrile-butadiene rubber accounts for 15 to 30% by weight of the total joint sheet, and the carbon black accounts for 30 to 300% by weight based on the weight of the acrylonitrile-butadiene rubber. A sheet-shaped composition containing, as an essential component, 1.0 to 5.0% by weight of sulfur or an organic sulfur-containing compound in terms of the amount of sulfur based on the weight of acrylonitrile-butadiene rubber,
It is achieved by a joint sheet (NA · J / S) characterized by being heat-treated in an autoclave. A similar purpose is to add a kneaded material containing a fiber material, acrylonitrile-butadiene rubber, carbon black, sulfur or an organic sulfur-containing compound between a hot roll and a cooling roll, and heat-roll it into a sheet. It can also be achieved by a method for producing a joint sheet (NA · J / S), which comprises heat-treating the sheet-like material in an autoclave at a temperature of 100 to 210 ° C. for 60 to 420 minutes after molding.

The rubber component of NA / J / S according to the present invention is
Use NBR with good oil resistance. NBR has a good compatibility with sulfur as a vulcanizing agent and an organic sulfur compound, and is easily vulcanized, so that the degree of vulcanization can be increased. When the amount of NBR used is lower than 15% by weight of the total weight of the components constituting NA · J / S, voids are generated in the molded product, the sealing property is deteriorated, and mechanical properties such as tensile strength are deteriorated. On the other hand, NBR
If the amount used of is more than 30% by weight based on the total weight of the components, mechanical properties such as tensile strength are rather deteriorated. Further, when it is made into a kneaded product, it is too soft, resulting in poor processability. This N
A particularly preferable range of BR is 17 to 25% by weight.

For the vulcanization of the NBR, a vulcanizing agent composed of sulfur or an organic sulfur-containing compound is used as NBR1 in terms of the amount of sulfur.
1.0 to 5.0 parts by weight, preferably 1.0 to 3.0 parts by weight, is added to 00 parts by weight. If the compounding amount is less than 1.0 part by weight, vulcanization does not proceed, and if adding more than 5.0 parts by weight, it blooms on the surface of the sheet at the time of molding, and sulfur is mixed into the ester type lubricating oil at the time of use. And corrode the copper pipe. Examples of the organic sulfur-containing compound include tetramethylthiuram disulfide (Noxceller TT manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 4-4′-dithiodimorpholine (Barnock manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
R), 2- (4'-morpholinodithio) benzothiazole (Ouchi Shinko Chemical Industry Co., Ltd. Nox Cellar MD
B), dipentamethylene thiuram tetrasulfide (NOXCELLER TRA manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) and the like, but not limited thereto, and any organic sulfur-containing compound capable of vulcanizing NBR may be used.

In addition to the above sulfur and organic sulfur-containing compounds, vulcanization aids such as zinc oxide and magnesium oxide, aldehyde ammonia series, thiuram series, dithiocarbamate series, sulfenamide series, thiazole series, guanidine series, thiourea A vulcanization accelerator such as a system, a xanthate, or an aldehyde amine can be used in combination.

Further, as the rubber chemicals other than the above-mentioned vulcanization type, an appropriate amount of an antioxidant, a surfactant, an anti-scorch agent, a plasticizer, a colorant and the like can be used. However, it is desirable that the blending amount of these is minimized because it may be an extract from the sheet to accelerate the deterioration of the ester-based lubricating oil.

The NA / J / S according to the present invention contains carbon black as an essential component as a filler, and the amount of the component is 30 to 300 parts by weight, particularly 30 to 150 parts by weight, relative to 100 parts by weight of NBR. Is preferred. Carbon black forms a carbon gel during kneading with NBR and enhances the mechanical strength of the molded product. It also serves as a cross-linking point of NBR and brings about the same effect as that of increasing the vulcanization degree. Therefore, when carbon black is added in an amount of 300 parts by weight or more based on 100 parts by weight of NBR, the workability of the kneaded product is reduced and the brittleness of the molded product is reduced. Again 3
Addition of 0 parts or less results in the same result as the NBR vulcanization degree is lowered as described above, and results in bad results such as increased elution into the lubricating oil and reduced mechanical strength.

Fillers other than carbon black include
Clay, talc, barium sulfate, sodium bicarbonate, graphite, kaolinite, sericite, calcined clay,
An appropriate amount of wollastonite or the like can be added alone or in combination of two or more kinds.

In addition, the NA / J / S according to the present invention contains an appropriate amount of inorganic fibers and / or organic fibers other than asbestos. The blending of fibers increases the mechanical strength of NA · J / S. Suitable fibers include aromatic polyamide fibers,
Polyethylene fiber, acrylic fiber, nylon fiber, cellulose pulp such as bamboo pulp, softwood pulp, phenol fiber, aromatic polyamide fiber (chopped fiber)
And organic fibers such as rock wool, carbon fibers, glass fibers, and sepiolite. These organic fibers and inorganic fibers are used alone or in combination. Among the above-mentioned organic fibers, aromatic polyamide fibers, polyethylene fibers, acrylic fibers, and nylon fibers which are synthetic fibers are preferable because the tensile strength of NA · J / S is improved by fibrillation. The organic fiber and the inorganic fiber may be fibers used in conventional NA · J / S. The aromatic polyamide fiber, polyethylene fiber, acrylic fiber, nylon fiber and the like are added in a ratio of 10 to 40% by weight based on the total weight of NA · J / S. Four
It is not necessary to add 0% by weight or more, and it is not preferable to add 40% by weight or more because it is difficult to obtain a uniform composition.

The NA / J / S according to the present invention is based on the conventional production method, and first, the above-listed substances are sufficiently kneaded in a Henshal mixer or the like using an appropriate solvent, and the kneaded material is heated and roasted. NB is put between a pair of rolls (about 150 ° C) and a cold roll (about 20 ° C) to evaporate the solvent and NB
A sheet-like material is obtained while vulcanizing R. Next, the sheet-like material is heat-treated in an autoclave to obtain NA / J / S according to the present invention. The heat treatment in the autoclave is preferably carried out at a temperature between 100 and 210 ° C. for 60 minutes or longer, more preferably at 130 to 180 ° C. for 60 to 240 minutes.

The extraction amount of the mixture of the alternative CFC / NA / J / S flon obtained by the above method and the ester type lubricating oil was measured. As shown in FIG. It was confirmed that it decreased with. Further, it has been deduced that the extraction amount is preferably 0.5% or less for practical use, and that the processing time is required to be about 60 minutes to satisfy the value. At the same time, when the total acid number showing the deterioration state of the ester-based lubricating oil was examined, it was confirmed that it decreased with the time of the autoclave treatment, as shown in FIG. 2, which was a practically preferable value of 0.05 [mgKO
It was deduced that a processing time of about 60 minutes was required to satisfy [H / g]. The heating temperature and the treatment time in the autoclave treatment are in an inversely proportional relationship, and as the heating temperature is higher and the treatment time is longer, vulcanization proceeds, but when organic fibers are mixed,
When the heating temperature is low and the treatment time is short, the vulcanization may not proceed, because the organic fiber may deteriorate. Therefore, upon implementation, the optimum conditions are determined with these points in mind.

This autoclave heat treatment is a treatment for vulcanizing the unreacted portion of the vulcanization by the above-mentioned hot roll. At that time, by performing the treatment for a relatively long time, the vulcanization progresses uniformly and sufficiently in the thickness direction of the sheet. In addition, the secondary effect that the surface of the sheet is washed with water vapor in the autoclave container to remove unreacted sulfur and various compounds in the sheet and on the surface of the sheet can be obtained. Therefore, according to the production method of the present invention, the unvulcanized components to be the eluate are reduced, and the unvulcanized components and other compounds are purified even if they exude to the surface of the sheet. No matter is mixed into the ester-based lubricating oil to deteriorate the lubricating oil or corrode the copper pipe. Further, as a result of the increased vulcanization degree, the mechanical strength characteristics of NA · J / S also show good values.

[0019]

The present invention will be clarified by the following examples. However, the present invention is not limited to this.

(Example 1) A rubber masticating roller was used to measure
After weighing a predetermined amount of NBR thinned to 2 mm,
Swelled in 300 parts by weight of toluene, Henschel together with fiber materials, carbon black, fillers other than carbon black, vulcanizing agents (sulfur), vulcanization accelerators, and other rubber chemicals in the compounding ratio shown in A of Table 1. The mixture was kneaded in a mixer for 80 minutes. The obtained kneaded material was heated on a 150 ° C. heat roll, and 2
Pressure vulcanization molding was performed with a 0 ° C. cold roll calender roll to obtain a sheet-like material having a thickness of 1.5 mm. Then, this sheet material was post-treated at 150 ° C. for 60 minutes by an autoclave to obtain NA · J / S.

[0021]

[Table 1]

Example 2 A sheet-like material having the composition shown in A of Table 1 and produced by the same method as in Example 1 was treated at 150 ° C. for 90 minutes in an autoclave to obtain NA. I got J / S.

(Example 3) A sheet-like material having the composition shown in A of Table 1 and produced by the same method as in Example 1 was treated at 150 ° C for 120 minutes by an autoclave to obtain NA. I got J / S.

(Comparative Example 1) A sheet-like material having the composition shown in A of Table 1 and manufactured by the same method as in Example 1 was made NA.J / S without autoclaving. .

(Comparative Example 2) A sheet-like material having the composition shown in A of Table 1 and produced in the same manner as in Example 1 was post-treated at 150 ° C for 30 minutes in an autoclave to obtain NA.・ I got J / S.

(Comparative Example 3) A sheet-like material having the composition shown in B of Table 1 and produced in the same manner as in Example 1 was post-treated at 150 ° C for 90 minutes by an autoclave to obtain NA.・ I got J / S.

Table 2 shows the physical properties of each NA · J / S obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[0028]

[Table 2]

In Table 2, the tensile strength, compression rate, restoration rate and stress relaxation rate of NA · J / S are JIS R345.
It measured according to 3. In addition, the sealability is such that the ring-shaped punched NA / J / S is sandwiched by flanges and the N ₂ gas pressure is 15
The amount of leakage per hour when a load of kgf / cm ² was obtained was determined by the underwater substitution method. In addition, in order to check CFC resistance and refrigerating machine oil resistance, alternative CFCs, ester-based lubricating oil and NAJ / S were placed in a sealed container and treated with NA / J / S tension at 150 ° C for 22 hours. The rate of decrease in strength was measured. Further, the extraction amount of the eluate was measured from the weight change of NA · J / S before and after the treatment. Deterioration of lubricating oil can be measured using alternative CFCs, ester type lubricating oils and NA ・ J / S.
Was placed in a closed container, treated at 150 ° C. for 30 days, taken out of the ester-based lubricating oil, and the total acid value thereof was measured. The total acid value was measured according to JIS K2501. The smaller the total acid value, the better. Usually, it can be used if it is about 0.10 or less, preferably about 0.05 or less. The copper plate corrosion is a measure of the amount of unreacted sulfur remaining in NA · J / S, and was visually observed.

From Table 2, the NA of the present invention of Examples 1 to 3
・ J / S is the tensile strength, compression rate, restoration rate of the sheet itself,
The mechanical strength characteristics such as the stress relaxation rate and the sealability are equal to or higher than those of the NAJ / S of the comparative example, and can be handled in the same manner as the conventional one. However, the NA / J / S of the present invention is
Since the reduction rate of tensile strength, the amount of extraction, and the total acid value of the ester-based lubricating oil are lower than the NA / J / S of the comparative example, the resistance to the mixed system of CFC substitute and the ester-based lubricating oil is high. It turns out to be excellent. On the other hand, as in Comparative Example 1, in the case of NA / J / S which is not carried out by autoclave treatment after sheet-making and only by the crosslinking reaction by the hot roll at the time of sheet-making, the sulfur cannot be sufficiently reacted, so that the rubber , The total acid value of the lubricating oil became worse, and copper plate corrosion was also confirmed. In Comparative Example 2, since the autoclave treatment time after sheet making was shorter than the range of the present invention, both the rubber extraction and the total acid value of the lubricating oil showed poor values. Further, in Comparative Example 3, since the autoclave treatment is performed within the range specified in the present invention, the resistance to the mixed system of the CFC substitute and the ester-based lubricating oil is improved, but the sulfur content is within the range of the present invention. Since it was blended in a large amount as described above, the total acid value showed a bad value, and copper plate corrosion was also confirmed. Also, the sealing property was poor.

[0031]

As described above, according to the present invention, the autoclave treatment reduces the unvulcanized component in NA · J / S, which is the eluate, as well as the unvulcanized component and Since other compounds are purified even if they exude to the surface of the sheet, these eluates may be mixed in the ester-based lubricating oil to deteriorate the ester-based lubricating oil or corrode the copper pipe. Absent. Furthermore, as a result of increasing the degree of vulcanization, N
The mechanical strength characteristics of A · J / S also show good values.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the NA.J / S autoclave treatment time of the present invention and the amount of extraction with an ester-based lubricating oil.

FIG. 2 is a graph showing the relationship between the NA * J / S autoclave treatment time of the present invention and the total acid value of the ester-based lubricating oil in which the sheet is immersed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display part // (C08L 21/00 9:02) (72) Inventor Shoichi Shigedome Miyazaki, Kawasaki City, Kanagawa Prefecture 1-8-4- 313, Tsubashi, Ward (72) Toru Segawa 4-1000-4G, Matsumi-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (72) Takuya Hirokawa 4-1000-3L, Matsumi-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture

Claims (2)

[Claims] 1. A composition comprising a fibrous material, rubber, a rubber chemical, a filler and the like, which has a total joint sheet weight of 15
To 30% by weight of acrylonitrile butadiene rubber, 30 to 30 relative to the weight of the acrylonitrile butadiene rubber
A sheet-shaped composition containing 0% by weight of carbon black and 1.0 to 5.0% by weight of sulfur or an organic sulfur-containing compound in terms of sulfur with respect to the weight of the acrylonitrile-butadiene rubber as an essential component is heat-treated in an autoclave. A joint sheet characterized by being formed. 2. A kneaded material containing a fiber material, acrylonitrile butadiene rubber, carbon black, sulfur or an organic sulfur-containing compound is put between a hot roll and a cooling roll and heated and rolled to form a sheet. After the molding, the sheet-like material is heat treated in an autoclave at a temperature of 100 to 210 ° C. for 60 to 420 minutes.