JP6843265B2 - Sealing material - Google Patents

Description

The present invention relates to a sealing material . More specifically, the present invention relates to a sealing material that can be used for contacting R32 refrigerant and requires high cold resistance.

Hydrogenated NBR is widely used for hose members, automobile seal members, etc. because it has excellent heat resistance, chemical stability, mechanical properties, etc., as well as oil resistance.

Hydrogenated NBR has a feature that various properties can be changed by changing the acrylonitrile [AN] content. On the other hand, in consideration of use in cold regions, there is an increasing demand for a hydrogenated NBR composition having cold resistance in addition to oil resistance and heat resistance.

However, in general, hydrogenated NBR compositions have a relationship in which heat resistance deteriorates when cold resistance is improved, and it is difficult to impart high cold resistance while maintaining excellent heat resistance.

In addition, the adoption of R32 (HFC), which is a new refrigerant with a low global warming coefficient, is being promoted toward the recent greenhouse gas reduction target, and there is also a demand for a sealing material that can be used for applications that come into contact with the R32 refrigerant. It is increasing.

WO 2013/175877 A1 WO 2013/175878 A1

An object of the present invention is to provide a sealing material that can be used for R32 refrigerant contact applications, has both excellent cold resistance and heat resistance, and can sufficiently maintain sealing properties even in a low temperature environment of -40 ° C or lower. To do .

An object of the present invention is that the freezing point is -40 ° C or less and the molecular weight is 500 to 100 parts by weight of hydrogenated NBR having an acrylonitrile content of 15 to 22%, which is a hydride of acrylonitrile-butadiene binary copolymer rubber. A crosslinked molded product of a hydrogenated NBR composition containing 10 to 40 parts by weight of 1000 ester-based plasticizers and 1 to 10 parts by weight of organic peroxide, the TR-10 value in the low temperature elastic recovery test was -36. Achieved by sealing materials below ° C.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a sealing material that can be used for R32 refrigerant contact applications, has both excellent cold resistance and heat resistance, and can sufficiently maintain sealing properties even in a low temperature environment of -40 ° C or lower. .. This is due to the fact that hydrogenated NBR having a specific AN content was used and a specific amount of a specific ester-based plasticizer was blended.

As the hydrogenated NBR, one having an AN content in the range of 15 to 22%, preferably 18 to 21% is used. No commercial product has an AN content lower than this, while a product with an AN content higher than this results in poor cold resistance and R32 refrigerant resistance. The degree of hydrogenation is arbitrary.

Hydrogenated NBR is peroxide crosslinked. When an amine vulcanizable hydrogenated NBR containing a carboxyl group or the like is used, the R32 refrigerant resistance becomes inferior as shown in Comparative Example 1 below (see Patent Documents 1 and 2).

As the ester-based plasticizer, those having a freezing point of -40 ° C or lower, preferably -45 ° C or lower and a molecular weight of 500 to 1000 are used at a ratio of about 10 to 40 parts by weight per 100 parts by weight of hydrogenated NBR.

If the freezing point is higher than this, the cold resistance will be inferior, and if the molecular weight is smaller than this, the cold resistance will be improved, but the heat resistance will be worse, while if it is larger than this, the viscosity will be high and it will be difficult to handle. , The compatibility will also deteriorate. Further, if the blending ratio is less than this, the cold resistance becomes inferior, while if it is used more than this, the cold resistance is improved, but the heat resistance and the R32 refrigerant resistance are inferior, and the kneading processability is also deteriorated.

Examples of ester-based plasticizers having such a freezing point and / molecular weight include commercially available products such as ADEKA products ADEKA Sizer RS-700, RS-1000 (or more polyether ester-based), and C-9N (trimellitic acid isononyl ester). Etc. are used.

Organic peroxides used for peroxide cross-linking of hydride NBR include, for example, dithibyl peroxide, dicumyl peroxide, tertiary butylcumyl peroxide, 1,1-di (third butylperoxy)-. 3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (3rd butylperoxy) hexane, 2,5-dimethyl-2,5-di (3rd butylperoxy) hexin-3 , 1,3-Di (3rd Butyl Peroxyisopropyl) benzene, 2,5-Dimethyl-2,5-Di (Benzoyl Peroxy) hexane, 3rd Butyl Peroxybenzoate, 3rd Butyl Peroxyisopropyl Carbonate, n -Butyl-4,4'-di (3rd butylperoxy) valerate and the like are used at a ratio of about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight, per 100 parts by weight of hydride NBR. If the amount of organic peroxide is less than this, a vulcanized product with a sufficient cross-linking density cannot be obtained, while if it is used in a larger proportion, foaming cannot be performed by vulcanization, or it is possible. Even so, the rubber elasticity and elongation will decrease.

In addition to the above essential components, polyfunctional unsaturated compounds such as triallyl (iso) cyanurate, trimethylolpropane tri (meth) acrylate, and triallyl trimerite are added to the composition in an amount of about 100 parts by weight of hydrogenated NBR. It is preferably blended in an amount of 10 parts by weight or less, preferably about 2 to 8 parts by weight. The formulation of the polyfunctional unsaturated compound is effective in further improving the heat resistance and compression set resistance. However, when used in a larger proportion than this, the rubber elasticity and elongation are reduced. Here, (iso) cyanurate means cyanurate or isocyanurate, and (meth) acrylate means acrylate or methacrylate.

In the composition, reinforcing agents such as carbon black and white carbon, fillers such as talc, clay, graphite and calcium silicate, processing aids such as stearic acid, palmitic acid and paraffin wax, zinc oxide and magnesium oxide, Various compounding agents generally used in the rubber industry, such as acid receiving agents such as hydrotalcite, antiaging agents, and plasticizers other than the ester-based plasticizers, are appropriately added and used.

When carbon black is used alone, it is used at a ratio of about 20 to 150 parts by weight, preferably about 40 to 100 parts by weight, per 100 parts by weight of hydrogenated NBR, and the carbon black in this case is a single grade. Used as a mixture of products or multiple grades. When white carbon is used alone, it is used at a ratio of about 20 to 150 parts by weight, preferably about 30 to 60 parts by weight, per 100 parts by weight of hydrogenated NBR. Both of these can be used in combination, in which case they are used at a ratio of about 10 to 140 parts by weight per 100 parts by weight of hydrogenated NBR and a total of about 20 to 150 parts by weight.

When white carbon is used alone or in combination with carbon black, it is preferable to use a silane coupling in an amount of about 0.1 part by weight or more, preferably about 0.5 to 3 parts by weight, per 100 parts by weight of hydrogenated NBR. As the silane coupling agent, any one that can be generally used for rubber can be used without limitation. For example, vinyl trimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, etc. Examples thereof include γ-aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane. The formulation of the silane coupling agent contributes to the improvement of heat resistance and cold resistance.

The composition is prepared by kneading using a kneader such as an intermix, a kneader, a Banbury mixer, or an open roll, and the vulcanization is performed using an injection molding machine, a compression molding machine, a vulcanization press, or the like. Generally, it is carried out by heating at about 150 to 200 ° C. for about 2 to 30 minutes, and if necessary, secondary vulcanization by heating at about 120 to 200 ° C. for about 1 to 24 hours is also performed.

The sealing material formed from such a hydride NBR composition has less foaming even when it is brought into contact with the R32 refrigerant under the conditions of 40 ° C. and 24 hours, and the TR-10 value in the low temperature elastic recovery test is -36. Since the temperature is below ℃ and the compression set of the G25 O-ring after 70 hours at 120 ℃ is 34% or less, it can be used for applications that come into contact with R32 refrigerant, and is used in a low temperature environment of -40 ℃ or less. It is effectively used as a sealing material for refrigerants used in air conditioners and the like.

Next, the present invention will be described with respect to Examples.

Example 1
Hydrogenated NBR (Zeon Corporation Zetpol 4310, AN content 18.6%) 100 parts by weight Carbon black (Tokai carbon product Seest GS) 95 〃
Ester plasticizer (ADEKA product ADEKA Sizer RS-700 20 〃
Freezing point -53 ° C, molecular weight about 550)
Dikmyl Peroxide 6 〃
Processing aid (Miyoshi oil and fat product stearic acid TST) 1 〃
Anti-aging agent (Ouchi Shinko Kagaku Kogyo product Nocrack CD) 1 〃
Each of the above components (excluding the cross-linking agent) is kneaded with a kneader, and then the cross-linking agent is added with an open roll and kneaded. The kneaded product (composition) was press vulcanized at 180 ° C. for 6 minutes and then oven vulcanized (secondary vulcanization) at 150 ° C. for 1 hour.

The crosslinked products were measured and evaluated for each of the following items.
Low temperature elastic recovery test: JIS K 6261 compliant with ISO 2921
If the measured TR-10 value is -40 ° C or less, ◎, even if it is -39 to -36 ° C
○, evaluated as × if -35 ° C or higher Compression permanent strain test: JIS K 6262 compliant with ISO 815-1
G25 O-ring specified in JIS B 2401-1 corresponding to ISO 3601-1
Use, 120 ° C, 70 hours test, compression set of 20% or less ◎, 21
~ 34% was evaluated as ○, and 35% or more was evaluated as ×. Freon foam resistance evaluation test: 5 G25 O-rings specified in JIS B 2401-1
Was immersed in R32 refrigerant at 40 ° C for 24 hours.
After that, heat at 135 ° C for 1 hour and O-ring.
Cross section cut into 10 equal parts per piece (50 in total)
If the number of foams in is less than 15/50, ○,
If it is 15/50 or more, it is evaluated as ×

Example 2
In Example 1, the amount of ester plasticizer was changed to 10 parts by weight.

Example 3
In Example 1, the amount of ester plasticizer was changed to 40 parts by weight.

Comparative Example 1
In Example 1, the same amount (100 parts by weight) of Zeon Corporation Zetpol 3610 (AN content 20.5%) was used as the hydrogenated NBR, and 2.5 parts by weight of hexamethylenediamine dicarbamate was used instead of dicumyl peroxide. .. However, oven vulcanization was carried out at 175 ° C. for 6 hours.

Comparative Example 2
In Example 1, Zeon Corporation Zetpol 3310 (AN content 24.6%) was used as the hydrogenated NBR in the same amount (100 parts by weight).

Comparative Example 3
In Example 1, no ester plasticizer was used.

Comparative Example 4
In Example 1, 60 parts by weight of an ester plasticizer was used.

Comparative Example 5
In Example 1, the same amount (20 parts by weight) of ADEKA product ADEKA Sizer RS-735 (freezing point -8 ° C., molecular weight about 850) was used as the ester plasticizer.

Comparative Example 6
In Example 1, the same amount (20 parts by weight) of ADEKA product ADEKA Sizer RS-107 (freezing point -47 ° C., molecular weight 434) was used as the ester plasticizer.

The results obtained in each of the above Examples and Comparative Examples are shown in the following table. In Comparative Example 3, the kneading processability was poor.

From the above results, the following can be said.
(1) Each of the examples produces a crosslinked product having both high cold resistance and heat resistance in addition to chlorofluorocarbon resistance (Examples 1 to 3).
(2) When hydrogenated NBR of an amine vulcanization system (Comparative Example 1) is used, the compression set resistance is improved, but the chlorofluorocarbon foam resistance is inferior.
(3) In Comparative Example 2 in which hydrogenated NBR having an AN content of 24.6% was used, cold resistance and chlorofluorocarbon resistance were insufficient.
(4) In Comparative Example 3 in which the ester-based plasticizer was not used, the cold resistance was insufficient.
(5) In Comparative Example 4 in which an ester-based plasticizer of a specified amount or more was used, the cold resistance was improved, but not only the kneading processability was poor, but also the heat resistance and chlorofluorocarbon foaming resistance were inferior. ..
(6) In Comparative Example 5 using an ester-based plasticizer having a freezing point of -8 ° C, the cold resistance was insufficient.
(7) In Comparative Example 6 in which an ester-based plasticizer having a molecular weight of 434 was used, the cold resistance was improved, but the heat resistance was inferior.

Claims (6)

An ester-based plasticizer having a freezing point of -40 ° C or less and a molecular weight of 500 to 1000 with respect to 100 parts by weight of hydrogenated NBR having an acrylonitrile content of 15 to 22%, which is a hydride of acrylonitrile-butadiene binary copolymer rubber. A sealant having a TR-10 value of -36 ° C or less in a low temperature elastic recovery test, which is a crosslinked molded product of a hydrogenated NBR composition containing ~ 40 parts by weight and 1 to 10 parts by weight of an organic peroxide. The sealing material according to claim 1, wherein an ester-based plasticizer having a freezing point of −45 ° C. or lower is used. The sealing material according to claim 1, wherein the compression set after 70 hours at 120 ° C. of the G25 O-ring is 34% or less. The sealing material according to claim 1, which is used in a low temperature environment of -40 ° C or lower. The sealing material according to claim 1, which is used as a seal for a refrigerant. The sealing material according to claim 5, which is used for R32 refrigerant contact applications.