WO2019078068A1 - Hydrogenated nbr composition - Google Patents

Abstract

A hydrogenated NBR composition which is obtained by blending 5-50 parts by weight of an ester-based plasticizer that has a freezing point of -40°C or less and a molecular weight of 500-1,000 and 1-10 parts by weight of an organic peroxide per 100 parts by weight of a hydrogenated NBR that has an acrylonitrile content of 15-22%. This hydrogenated NBR composition provides a sealing material which is suitable for applications in contact with R32 coolant, while achieving a good balance between excellent cold resistance and heat resistance, and which is capable of maintaining sufficient sealing properties even in a low-temperature environment at -40°C or less. A sealing material which is formed from this hydrogenated NBR composition has a TR-10 value of -36°C or less in a low-temperature elasticity recovery test, and a G25 O-ring thereof has a compression set of 34% or less after 70 hours at 120°C.

Description

Hydrogenated NBR composition

The present invention relates to hydrogenated NBR compositions. More particularly, it relates to hydrogenated NBR compositions that can be used in R32 refrigerant contact applications and can provide seals that require high cold resistance.

Since hydrogenated NBR is excellent in oil resistance, heat resistance, chemical stability, mechanical properties and the like, it is widely used as a member for hoses, automobile seal members and the like.

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

However, in general, the hydrogenated NBR composition is in a relation that heat resistance deteriorates when cold resistance is improved, and it is difficult to impart high cold resistance while maintaining excellent heat resistance.

In addition, R32 (HFC), a new refrigerant with a low global warming potential, is being adopted toward the recent greenhouse gas reduction target, and there is also a demand for sealing materials that can be used for applications that contact R32 refrigerant. It is rising.

WO 2013/175877 A1 WO 2013/175878 A1

An object of the present invention is to provide a sealing material which can be used in R32 refrigerant contact applications, and which has both excellent cold resistance and heat resistance, and which can sufficiently maintain sealability even in a low temperature environment of -40 ° C or less To provide a hydrogenated NBR composition.

The object of the present invention is to use 5 to 50 parts by weight of an ester plasticizer having a freezing point of -40.degree. C. or less and a molecular weight of 500 to 1000 and 100 parts by weight of hydrogenated NBR having an acrylonitrile content of 15 to 22%. This is achieved by a hydrogenated NBR composition comprising 1 to 10 parts by weight of oxide.

The present invention provides a sealing material that can be used in R32 refrigerant contact applications, and has both excellent cold resistance and heat resistance, and can maintain sealing performance sufficiently even in a low temperature environment of -40 ° C or less An improved NBR composition is provided. This is because hydrogenated NBR having a specific AN content is used, and a specific amount of a specific ester plasticizer is compounded.

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

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

As ester-based plasticizers, those having a freezing point of -40 ° C. or less, preferably -45 ° C. or less and a molecular weight of 500 to 1000 are used in an amount of about 5 to 50 parts by weight, preferably 10 to 30 parts by weight per 100 parts by weight of hydrogenated NBR. Used in proportions by weight.

If the freezing point is higher than this, cold resistance will be poor, and if the molecular weight is smaller than this, cold resistance will be improved, but heat resistance will deteriorate, while if it is larger, viscosity will be high and handling will be difficult , Compatibility will also be worse. If the proportion is lower than this range, cold resistance will be poor. If more than this range, cold resistance will be improved, but heat resistance and R32 refrigerant resistance will be inferior, and kneading processability will also deteriorate.

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

Examples of the organic peroxide used for peroxide crosslinking of hydrogenated NBR include di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, 1,1-di (tert-butylperoxy)- 3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3 1,3-Di (tert-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n -Butyl-4,4'-di (tert-butylperoxy) valerate or the like is used in a proportion of about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight, per 100 parts by weight of the hydrogenated NBR. If the amount of the organic peroxide is less than this, a vulcanized product having a sufficient crosslink density can not be obtained, while if it is used at a ratio higher than this, it can not be formed by foaming or vulcanization. Even in such cases, the rubber elasticity and the elongation will be reduced.

In the composition, in addition to the above essential components, polyfunctional unsaturated compounds such as triallyl (iso) cyanurate, trimethylolpropane tri (meth) acrylate, and triallyl trimellitate are added in an amount of about 100 parts by weight of hydrogenated NBR. It is preferable to blend 10 parts by weight or less, preferably about 2 to 8 parts by weight. The compounding of the polyfunctional unsaturated compound is effective to further improve the heat resistance and the compression set resistance. However, when it is used at a ratio higher than this, the rubber elasticity and elongation decrease. 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, magnesium oxide, Various additives commonly used in the rubber industry, such as acid acceptors such as hydrotalcite, anti-aging agents, and plasticizers other than the above-mentioned ester plasticizers, are appropriately added and used.

When carbon black is used alone, it is used in a proportion of about 20 to 150 parts by weight, preferably about 40 to 100 parts by weight, per 100 parts by weight of hydrogenated NBR, in which case the carbon black may be a single grade. Or as a mixture of multiple grades. When white carbon is used alone, it is used in a proportion 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 about 10 to about 140 parts by weight each per 100 parts by weight of hydrogenated NBR, and the total of these is about 20 to about 150 parts by weight.

When white carbon is used alone or in combination with carbon black, it is preferable to use 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 which can be generally used for rubber can be used without limitation, and examples thereof include vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane Examples thereof include γ-aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane. The blending of the silane coupling agent contributes to the improvement of the heat resistance and the cold resistance.

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

The sealing material molded from such a hydrogenated NBR composition has less foaming even when 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. Because it is less than ° C, and the compression set after 70 hours at 120 ° C of G25 O-ring is 34% or less, it can be used for applications that contact R32 refrigerant, and used in a low temperature environment of -40 ° C or less Sealing material, for example, a seal for a refrigerant used in an air conditioner or the like.

The invention will now be described by way of example.

Example 1
Hydrogenated NBR (Nippon Zeon product Zetpol 4310, AN content 18.6%) 100 parts by weight Carbon black (Tokai carbon product Seat GS) 95 〃
Ester-based plasticizer (ADEKA products Adekasizer RS-700 20 〃
Freezing point-53 ° C, molecular weight about 550)
Dicumyl peroxide 6 〃
Processing aid (Miyoshi oil product Stearic acid TST) 1 〃
Anti-aging agent (Ouchi emerging chemical industry product Nocl CD) 1 1
The above components (except for the crosslinking agent) are kneaded with a kneader, and then the crosslinking agent is added and kneaded using an open roll. The kneaded product (composition) was press-cured at 180 ° C. for 6 minutes and then oven-cured (secondary cure) at 150 ° C. for 1 hour.

The following items were measured and evaluated for the crosslinked product.
Low-temperature elastic recovery test: conforms to JIS K6261 corresponding to ISO 2921 TR if measured TR-10 value is -40 ° C or less, ○ if -39 to -36 ° C, × if -35 ° C or more Compression set test evaluated: Using a G25 O-ring specified in JIS B 2401-1 according to JIS K6262 corresponding to ISO 815-1, according to ISO 3601-1, the compression set after the test at 120 ° C. for 70 hours is 20% or less 21, 21
34% was evaluated as ○, 35% or more was evaluated as × CFC foam resistance evaluation test: After immersing 5 pieces of G25 O-ring specified in JIS B2401-1 in R32 refrigerant at 40 ° C. for 24 hours, Heated at 135 ° C for 1 hour, and divided into 10 equal sections per O-ring (total 50)
○, if the number of foams in is less than 15/50
If it is 15/50 or more, it was evaluated as x

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 Nippon Zeon product Zetpol 3610 (20.5% of AN content) was used as a hydrogenated NBR, and 2.5 parts by weight of hexamethylene diamine dicarbamate was used instead of dicumyl peroxide. . However, oven vulcanization was performed at 175 ° C. for 6 hours.

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

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 Adekasizer RS-735 (solidifying point -8 ° C., molecular weight about 850) was used as an ester-based plasticizer.

Comparative example 6
In Example 1, the same amount (20 parts by weight) of ADEKA product Adekasizer RS-107 (solidifying point-47 ° C, molecular weight 434) was used as an ester-based 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) In each of the examples, in addition to fluorocarbon foam resistance, a crosslinked product in which high cold resistance and heat resistance are compatible (Examples 1 to 3) is produced.
(2) Although the compression set resistance characteristics are improved when the hydrogenated NBR of the amine vulcanization system (Comparative Example 1) is used, the fluorocarbon foam resistance is inferior.
(3) In Comparative Example 2 in which the hydrogenated NBR having an AN content of 24.6% was used, the cold resistance and the fluorocarbon foam resistance were insufficient.
(4) In Comparative Example 3 in which no ester plasticizer was used, the cold resistance was insufficient.
(5) In Comparative Example 4 in which the ester plasticizer of the specified amount or more was used, the cold resistance is improved, but not only the kneading processability is not good, but also the heat resistance and the freon resistance are inferior. .
(6) In Comparative Example 5 using an ester plasticizer having a freezing point of −8 ° C., cold resistance was insufficient.
(7) In Comparative Example 6 in which an ester plasticizer having a molecular weight of 434 was used, although the cold resistance was improved, the heat resistance was inferior.

Claims (10)

5 to 50 parts by weight of an ester plasticizer having a freezing point of -40 ° C. or less and a molecular weight of 500 to 1000 and 1 to 10 parts by weight of organic peroxide relative to 100 parts by weight of hydrogenated NBR having an acrylonitrile content of 15 to 22% A hydrogenated NBR composition comprising The hydrogenated NBR composition according to claim 1, wherein an ester plasticizer having a freezing point of -45 ° C or less is used. The hydrogenated NBR composition according to claim 1, wherein 10 to 40 parts by weight of an ester plasticizer is blended. The hydrogenated NBR composition of claim 1 for use in R32 refrigerant contact applications. A sealing material which is a crosslinked molded product of the hydrogenated NBR composition according to claim 1. The sealing material according to claim 5, wherein TR-10 value in the low temperature elastic recovery test is -36 ° C or less. The sealing material according to claim 5, 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 5, which is used in a low temperature environment of -40 ° C or less. The sealing material according to claim 5, which is used as a refrigerant seal. The sealing material according to claim 9, which is used for R32 refrigerant contact application.