JP5998490B2 - Rubber composition for air spring - Google Patents

Description

  The present invention relates to a rubber composition for forming a gas chamber of an air spring used in railway vehicles, various industrial equipment, automobiles, and the like. More specifically, the air spring is excellent in heat resistance and adhesion to a reinforcing cord. The present invention relates to a rubber composition.

  The rubber wall that forms the air chamber of an air spring used in railway vehicles, various industrial equipment, automobiles, etc., is formed of a rubber composition in which a reinforcing cord made of polyamide yarn or the like is embedded in vulcanized rubber. In some cases, an outer rubber layer and an inner rubber layer are laminated on both the front and back surfaces of the rubber composition in which the reinforcing cord is embedded.

  The air spring rubber composition is required to have characteristics such as weather resistance, heat resistance, and flexibility, and it is also an important characteristic to adhere well to the reinforcing cord. Chloroprene rubber is an example of a rubber material that satisfies the properties such as weather resistance, heat resistance, and flexibility. In the presence of a thiourea vulcanization accelerator that is added to improve heat resistance, In particular, it is difficult to secure sufficient adhesion to a reinforcing cord subjected to RFL (resorcin formalin latex) treatment.

  In this case, the amount of sulfur used is increased in order to improve the adhesion, but if the amount of sulfur used is increased, the adhesion with the reinforcing cord can be improved, but the heat resistance is reduced. Will be invited. That is, when preparing a rubber composition for an air spring using chloroprene rubber, the adhesiveness and heat resistance of the reinforcing cords are contradictory issues. The following documents can be listed as prior art documents related to the present application.

JP 2008-132641 A JP 2009-127712 A JP 2004-36894 A JP 2001-131342 A

  The present invention has been made in view of the above circumstances, and solves the above-mentioned contradictory problems of a rubber composition containing chloroprene rubber, has good heat resistance, and has excellent adhesion to a reinforcing cord. An object is to provide a rubber composition for a spring.

As a result of intensive studies to achieve the above object, the present inventor has as a main component a chloroprene rubber or a blend of chloroprene rubber and a diene rubber, and the mass ratio of the chloroprene rubber and the diene rubber is determined at that time. Rubber / diene rubber = 60/40 to 100/0, and 100 parts by mass of this rubber component is blended with bismaleimide as a vulcanizing agent in the range of 1 to 10 parts by mass, and thiuram vulcanization is accelerated. The vulcanized molded product of this rubber composition has the weather resistance, heat resistance and flexibility possessed by the chloroprene rubber by blending the agent and setting the sulfur content as the vulcanizing agent to 0.5 parts by mass or less. It is possible to improve the adhesion to the reinforcing cord without degrading the properties such as, and in particular, to achieve both the heat resistance and the adhesiveness, which were considered to be anti-traditional in the past. Further an acid anhydride such as phthalic anhydride to improve environmental stability by blending 0.1 to 10 parts by weight, is possible to effectively prevent the adhesion reduction of the reinforcing hardness at particularly high temperature and high humidity It was found that a vulcanized rubber composition having excellent performance for an air spring can be obtained, and the present invention has been completed.

Therefore, this invention provides the rubber composition for air springs of the following Claim 1.
[Claim 1]
In the rubber composition for air springs, which is a vulcanized rubber composition comprising chloroprene rubber or a blend of chloroprene rubber and diene rubber as a main component and bonded and integrated with a reinforcing cord,
The mass ratio of the chloroprene rubber to the diene rubber is chloroprene rubber / diene rubber = 60/40 to 100/0, and 1 to 10 parts by mass of bismaleimide as a vulcanizing agent with respect to 100 parts by mass of the rubber component. 0.1-10 mass of 1 or 2 types or more of acid anhydrides which contain a thiuram type vulcanization accelerator and are chosen from phthalic anhydride, maleic anhydride, succinic anhydride, and glutaric anhydride A rubber composition for an air spring, which is obtained by vulcanizing and molding a rubber composition containing a part and having a sulfur content as a vulcanizing agent of 0.5 parts by mass or less.

Further, as a result of further studies on a more preferable composition in preparing the rubber composition according to claim 1, the present inventor has found a rubber composition for an air spring according to claims 2 to 9 as a preferred embodiment. Is to provide.

[Claim 2]
The rubber composition for an air spring according to claim 1, wherein the bismaleimide has a gelation time at 250 ° C of 100 seconds or less.
[Claim 3]
The rubber composition for an air spring according to claim 1 or 2, wherein the bismaleimide is one or more selected from 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, and bisphenol A.diphenyl ether bismaleimide. object.
[Claim 4]
The rubber composition for an air spring according to any one of claims 1 to 3, comprising 3 parts by mass or more of a thiuram vulcanization accelerator with respect to 100 parts by mass of the rubber component.
[Claim 5]
The air according to any one of claims 1 to 4, wherein the thiuram vulcanization accelerator contains one or both of tetramethylthiuram disulfide, tetrabutylthiuram disulfide, and tetrakis (2-ethylhexyl) thiuram disulfide. Rubber composition for spring.
[Claim 6]
The rubber composition for an air spring according to any one of claims 1 to 5, wherein the content of the bismaleimide is 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component.
[Claim 7 ]
The rubber composition for an air spring according to any one of claims 1 to 6 , wherein the reinforcing cord is one or more selected from polyamide yarn, polyester yarn, rayon yarn, and polyvinyl alcohol yarn.
[Claim 8 ]
The composition for an air spring according to any one of claims 1 to 7 , wherein the reinforcing cord is subjected to RFL (resorcinol formalin latex) treatment.
[Claim 9 ]
The rubber composition for an air spring according to any one of claims 1 to 8 , wherein the reinforcing cord is a woven fabric composed of warp and weft.

  The rubber composition for an air spring of the present invention has excellent weather resistance, heat resistance, flexibility, and adhesiveness with an excellent reinforcing cord, and can constitute an air spring having high performance and excellent durability. Is.

It is the schematic sectional drawing which showed typically the section of the rubber composition for air springs concerning an example of the present invention.

Hereinafter, the present invention will be described in more detail.
The rubber composition for an air spring of the present invention is, for example, bonded and integrated with a reinforcing cord 2 as shown by reference numeral 1 in FIG. 1, and is chloroprene rubber (CR) or chloroprene rubber (CR) and a diene system. The main component is a blend with rubber.

  The blending ratio of the chloroprene rubber and the diene rubber is chloroprene rubber / diene rubber = 60/40 to 100/0, preferably 70/30 to 100/0, more preferably 80/20 to 100. / 0.

  Here, the chloroprene rubber is excellent in weather resistance, heat resistance and flexibility as described in detail, and can further improve the rubber adhesion after standing by adding a diene rubber. When the blending amount of chloroprene rubber is reduced due to the blending of rubber, heat resistance tends to decrease.If diene rubber is blended exceeding the above range, the heat resistance may decrease and the object of the present invention may not be achieved. is there.

  The diene rubber blended with the chloroprene rubber is not particularly limited, and examples thereof include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), isoprene rubber (IR) and the like. 1 type or 2 types or more can be used. Of these, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), and isoprene rubber (IR) are particularly preferably used.

  In the rubber composition of the present invention, bismaleimide is blended as a vulcanizing agent, and as this bismaleimide, a bismaleimide having a gelation time at 250 ° C. of 100 seconds or less, particularly 50 seconds or less is preferably used. Specifically, 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A / diphenyl ether bismaleimide, and the like are preferably used as the bismaleimide, and one or more of these can be blended.

  The amount of the bismaleimide is 1 to 10 parts by mass, preferably 2 to 8 parts per 100 parts by mass of the rubber component consisting of the chloroprene rubber (CR) or a blend of chloroprene rubber (CR) and a diene rubber. It is 3 to 6 parts by mass, more preferably 3 to 6 parts by mass. If the blending amount is less than 1 part by mass, the adhesiveness with the reinforcing cord may not be sufficiently improved. On the other hand, if it exceeds 10 parts by mass, there is a risk of inconvenience such as a decrease in the flexibility of the rubber. is there.

  The rubber composition of the present invention achieves both heat resistance and reinforcing cord adhesion by using the bismaleimide as a vulcanizing agent, but in some cases, sulfur may be used in combination with bismaleimide. it can. In this case, the amount of sulfur is 0.5 parts by mass or less, preferably 0.3 parts by mass or less, with respect to 100 parts by mass of the rubber component. If the amount of sulfur exceeds 0.5 parts by mass, the heat resistance may decrease and the object of the present invention may not be achieved.

  In the rubber composition of the present invention, a thiuram vulcanization accelerator is blended together with the vulcanizing agent bismaleimide. Specific examples of the thiuram-based vulcanization accelerator include tetramethylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and the like, among which tetramethylthiuram disulfide, tetrabutyl Thiuram disulfide and tetrakis (2-ethylhexyl) thiuram disulfide are preferably used.

  The blending amount of the thiuram vulcanization accelerator is not particularly limited, but is 3 parts by mass or more, preferably 4 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 3 parts by mass, the effect of the accelerator may not be sufficiently obtained. On the other hand, the upper limit of the blending amount is not particularly limited, but is 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less. May occur.

  Vulcanization accelerators can be used for vulcanization as needed. Specifically, metal oxides such as magnesium oxide, calcium oxide, zinc oxide, lead oxide, antimony dioxide, antimony trioxide, An appropriate amount of fatty acid such as stearic acid can be blended. Among these, magnesium oxide, fatty acid and the like are preferably used.

  In the rubber composition of the present invention, an acid anhydride can be blended, and the environmental stability can be improved by blending the acid anhydride, which is particularly effective in reducing adhesiveness with a reinforcing cord under high temperature and high humidity. Can be suppressed.

  Acid anhydrides include acetic anhydride, benzoic anhydride, succinic anhydride, phthalic anhydride, maleic anhydride, nicotinic anhydride, propionic anhydride, -n-caproic anhydride, glutaric anhydride, formic anhydride, tetrahydrophthalic anhydride Acid, trifluoroacetic anhydride, endeck acid anhydride, n-caproic acid anhydride, phenylselenic acid anhydride, krendic acid anhydride, selenous anhydride, chromic anhydride, cinnamic acid anhydride, monochloroacetic acid anhydride, anhydrous Examples include tungstic acid, thiophosphoric anhydride, 1,8-naphthalic anhydride, vanadic anhydride, propanoic anhydride, boric anhydride, molybdic anhydride, iodic anhydride, itaconic anhydride, phosphoric anhydride, etc. 1 type (s) or 2 or more types can be used. Of these, phthalic anhydride and maleic anhydride are particularly preferably used.

  The compounding amount of the acid anhydride is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, still more preferably with respect to 100 parts by mass of the rubber component. Is 0.3 parts by mass or more. The upper limit of the amount is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 6 parts by mass or less with respect to 100 parts by mass of the rubber component. If the blending amount is less than 0.1 parts by mass, the effect of the acid anhydride blending may not be sufficiently obtained, and if it exceeds 10 parts by mass, the heat resistance may be deteriorated.

  In addition to the above components, the rubber composition includes known fillers, lubricants, tackifiers, anti-aging agents, ultraviolet absorbers, softeners, plasticizers, vulcanization accelerators, waxes, zinc whites, and the like. An appropriate amount of additives can be blended.

  Examples of the filler include carbon black such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, and MT, white carbon, fine magnesium silicate, heavy calcium carbonate, magnesium carbonate, clay, and talc. Organic fillers such as inorganic filler, high styrene resin, coumarone indene resin, phenol resin, lignin, modified melamine resin, petroleum resin and the like can be mentioned.

  Examples of the anti-aging agent include p, p′-dioctyldiphenylamine, p, p′-dicumyldiphenylamine, N, N′-diphenyl-p-phenylenediamine, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2 Amine-based anti-aging agents such as dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid stearate, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), tetrakis (methylene-3- (3,5-di-tert-butyl-4-hydride) Phenol-based anti-aging agents such as xy-phenyl) furopionate) methane, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone; 2-mercaptobenzimidazole, Examples include imidazole anti-aging agents such as tributylthiourea, 2-mercaptobenzimidazole zinc salt, and 2-mercaptomethylbenzimidazole zinc salt.

  Examples of the plasticizer include dioctyl phthalate (DOP), dibutyl phthalate (DBP), tricresyl phosphate (TCP) dioctyl sebacate (DOS), dioctyl adipate (DOA), and rapeseed oil.

  In addition, lubricants, tackifiers, ultraviolet absorbers, softeners, and the like may be appropriately selected from known ones as necessary.

  In the rubber composition of the present invention, the above components are kneaded and vulcanized into a sheet shape or a plate shape, for example, as indicated by reference numeral 1 in FIG. It is set as the wall body which forms the air chamber. In this case, the kneading of each component is not particularly limited, but is preferably performed in two stages or in three or more stages, for example, for vulcanization reactions such as vulcanizing agents and vulcanization accelerators. First, components other than those that act directly are kneaded to uniformly knead each component, and then a component that acts directly on the vulcanization reaction such as a vulcanizing agent and a vulcanization accelerator is added to the second stage. It is preferable to perform kneading and vulcanization molding.

  As the reinforcing cord 2 bonded and integrated with the rubber composition 1, a known one can be used, for example, those made of polyamide, polyester, rayon, polyvinyl alcohol, etc., among these, Polyamide is preferably used.

  In addition, these reinforcing cords 2 may be those subjected to RFL treatment impregnated with RFL (Resorcin Formalin Latex) liquid, thereby further improving the adhesion between the rubber composition 1 and the reinforcing cord 2. Can do.

  The form of the reinforcing cord 2 may be one using a thread-like or linear cord as it is, or may be a woven fabric composed of warp and warp, for example, and may be of other forms.

  The bonding mode between the reinforcing cord 2 and the rubber composition is not limited to the form in which the reinforcing cord 2 is embedded in the rubber composition 1 shown in FIG. A form in which the reinforcing cord is bonded and integrated on one or both sides of a rubber composition vulcanized and molded, or a form in which the reinforcing cord is bonded and integrated with a plurality of layers made of the rubber composition being sandwiched. You can also.

  The rubber composition of the present invention is bonded and integrated with the reinforcing cord and used as a wall body constituting the air chamber of the air spring. In that case, one side of the rubber composition of the present invention bonded and integrated with the reinforcing cord is used. Alternatively, another rubber layer can be laminated on both sides as necessary to form a wall of the air chamber.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example.

[ Reference Examples 1 to 14 ]
First, each component shown in the column of kneading stage A in Table 1 is kneaded using a Banbury mixer, and then each component shown in the column of kneading stage B in Table 1 is blended and kneaded to obtain a rubber composition. A product was prepared. About each obtained rubber composition, code | cord adhesiveness and heat resistance were evaluated with the following method. The results are shown in Table 1. In addition, all the mixing | blendings in the following Table 1 and Table 2 are a mass part.

[Cord adhesiveness]
The rubber composition is vulcanized and molded at 160 ° C. for 15 minutes, and at this time, a reinforcing cord made of polyamide yarn subjected to RFL treatment is vulcanized in a state of being buried in the rubber and bonded and integrated. A plate-shaped test piece (thickness 2 mm, width 20 mm, length 150 mm) was prepared.
The reinforcing cord was forcibly peeled off from the obtained test piece, and the ratio of the rubber adhesion area to the surface area of the reinforcing cord was defined as the rubber breaking rate, and the adhesiveness was evaluated. In addition, it is evaluated that adhesiveness is so high that a rubber fracture rate is high.

[Heat-resistant]
The rubber composition is vulcanized and molded at 160 ° C. for 15 minutes to prepare a test piece, and a tensile test is performed in accordance with JIS K6251-2004. Elongation at break Eb (dumbbell type 3 test piece) is obtained. It was measured. Further, the test piece was heated at 120 ° C. for 100 hours, the elongation Eb at the same time was measured in the same manner, and the Eb retention was calculated by the following formula. The higher the Eb retention, the better the heat resistance.
Eb retention (%) = (Eb after heating at 120 ° C. for 100 hours) / (Eb before heat treatment)

ＣＲ：クロロプレンゴム
ＮＲ：天然ゴム
ＦＥＦ：ＦＥＦカーボン
脂肪酸：ステアリン酸
ＤＯＰ：フタル酸ジオクチル
老防６Ｃ：Ｎ−フェニル−Ｎ’−１，３−ジメチルブチル−ｐ−フェニレンジアミン
ＴＴ：テトラメチルチウラムジスルフィド
ＴＯＴ：テトラキス（２−エチルヘキシル）チウラムジスルフィド
ＣＺ：Ｎ−シクロヘキシル−２−ベンゾチアゾリルスルフェンアミド
ＤＭ：ジベンゾチアジルジスルフィド
＊１：２５０℃でのゲル化時間３０秒未満
＊２：２５０℃でのゲル化時間３０秒
＊３：２５０℃でのゲル化時間７５秒

CR: chloroprene rubber NR: natural rubber FEF: FEF carbon fatty acid: stearic acid DOP: dioctyl phthalate aging 6C: N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine TT: tetramethylthiuram disulfide TOT : Tetrakis (2-ethylhexyl) thiuram disulfide CZ: N-cyclohexyl-2-benzothiazolylsulfenamide DM: Dibenzothiazyl disulfide * 1: Gelation time at 250 ° C less than 30 seconds * 2: Gel at 250 ° C Gelation time 30 seconds * 3: Gelation time at 250 ° C. 75 seconds

As shown in Table 1, the rubber compositions of Reference Examples 1, 2, and 4 have good adhesiveness to the reinforcing cords and good Eb retention of 50% or more even under severe temperature conditions. It was confirmed to have heat resistance.

[Examples 1-5 and Comparative Examples 1-7 ]
In order to confirm the effect of improving the environmental stability due to the addition of an acid anhydride, the rubber compositions having the compositions of Examples 1 to 5 shown in Table 2 below using phthalic anhydride as the acid anhydride are the same as the above Reference Example. It was prepared by the following procedure. Each rubber composition obtained was evaluated for cord adhesion and heat resistance in the same manner as in the above Reference Example, and after leaving the test piece at 40 ° C. and 98% RH for 7 days, the cord adhesion was similarly tested. The stability of the cord adhesion under high temperature and high humidity environment was evaluated. The results are shown in Table 2. For comparison, Comparative Examples 1 to 7 are shown in the same table. Comparative Example 1 is the above Reference Example 1, Comparative Example 2 is the above Reference Example 2, Comparative Example 5 is the above Reference Example 8 , and Comparative Example 6 is the above. The rubber composition having the same composition as that of Reference Example 4 was again subjected to an evaluation test of cord adhesion and heat resistance, and the cord adhesion after being left under the above high temperature and high humidity was evaluated.

As shown in Table 2, it was confirmed that addition of acid anhydride (phthalic anhydride) can suppress a decrease in adhesiveness when left in a high temperature and high humidity environment. In this case, Comparative Example 3 is not effective because the amount of acid anhydride (phthalic anhydride) is too small, and Comparative Example 4 is because the amount of acid anhydride (phthalic anhydride) is too large. The Eb retention rate is lowered and the heat resistance is poor.

1 Rubber composition 2 Reinforcement cord

Claims (9)

In the rubber composition for air springs, which is a vulcanized rubber composition comprising chloroprene rubber or a blend of chloroprene rubber and diene rubber as a main component and bonded and integrated with a reinforcing cord,
The mass ratio of the chloroprene rubber to the diene rubber is chloroprene rubber / diene rubber = 60/40 to 100/0, and 1 to 10 parts by mass of bismaleimide as a vulcanizing agent with respect to 100 parts by mass of the rubber component. 0.1-10 mass of 1 or 2 types or more of acid anhydrides which contain a thiuram type vulcanization accelerator and are chosen from phthalic anhydride, maleic anhydride, succinic anhydride, and glutaric anhydride A rubber composition for an air spring, which is obtained by vulcanizing and molding a rubber composition containing a part and having a sulfur content as a vulcanizing agent of 0.5 parts by mass or less.   The rubber composition for an air spring according to claim 1, wherein the bismaleimide has a gelation time at 250 ° C of 100 seconds or less.   The rubber composition for an air spring according to claim 1 or 2, wherein the bismaleimide is one or more selected from 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, and bisphenol A.diphenyl ether bismaleimide. object.   The rubber composition for an air spring according to any one of claims 1 to 3, comprising 3 parts by mass or more of a thiuram vulcanization accelerator with respect to 100 parts by mass of the rubber component.   The air according to any one of claims 1 to 4, wherein the thiuram vulcanization accelerator contains one or both of tetramethylthiuram disulfide, tetrabutylthiuram disulfide, and tetrakis (2-ethylhexyl) thiuram disulfide. Rubber composition for spring.   The rubber composition for an air spring according to any one of claims 1 to 5, wherein the content of the bismaleimide is 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for an air spring according to any one of claims 1 to 6 , wherein the reinforcing cord is one or more selected from polyamide yarn, polyester yarn, rayon yarn, and polyvinyl alcohol yarn. The composition for an air spring according to any one of claims 1 to 7 , wherein the reinforcing cord is subjected to RFL (resorcinol formalin latex) treatment. The rubber composition for an air spring according to any one of claims 1 to 8 , wherein the reinforcing cord is a woven fabric composed of warp and weft.

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