JP3692668B2 - Anti-vibration rubber composition - Google Patents

Description

上記構成により、耐熱安定性に優れるとともに、スコーチ安定性及び成形品生産性に優れ圧縮永久変形の小さい防振ゴムを提供する。
【００１３】
請求項２記載の防振ゴム組成物においては、請求項１記載の防振ゴム組成物において、前記ジエン系ゴムが、天然ゴム、又は、天然ゴムを５０重量％以上含むゴムブレンドであることを特徴とする。
【００１４】
【発明の実施の形態】
本発明の防振ゴム組成物に用いるゴム高分子成分はジエン系ゴムである。
【００１５】
ジエン系ゴムとしては、天然ゴム（ＮＲ）、イソプレンゴム（ＩＲ）、ブタジエンゴム（ＢＲ）といった一般的なもの、及び、これらのブレンドのいずれも使用可能である。好ましくは、天然ゴム単独、または、天然ゴムを主体とした他のジエン系ゴムとのゴムブレンドである。ゴムブレンドとしては、例えば天然ゴムとブタジエンゴムとを８０／２０の重量比で配合したものが好ましい。
【００１６】
本発明の防振ゴム組成物に用いる熱安定剤化合物は、下記一般式（Ｉ）で表される化合物（Ａ）（２−メルカプトベンゾイミダゾールの亜鉛塩、又はそのメチル化誘導体）と、下記化学式（II）で表される化合物（Ｂ）（４，４’−ビス（α，α’−ジメチルベンジル）ジフェニルアミン）と、下記化学式（III）で表される化合物（Ｃ）（Ｎ−ｔｅｒｔ−ブチル−ジ−（２−ベンソチアゾールスルフェンアミド））である。
【００１７】
【化３】

前記各化合物（Ａ）〜（Ｃ）は、ゴム高分子成分１００重量部すなわちジエン系ゴム１００重量部に対する、添加重量部ａ、ｂ及びｃが次式（ｉ）〜（ii）を満たす。
【００１８】
−１０≦ａ＋ｂ−２ｃ≦１０ （ｉ）
ａ、ｂ、ｃ≧０．３ （ii）
すなわち、ゴム高分子成分１００重量部に対する化合物（Ａ）と化合物（Ｂ）との合計添加重量部から化合物（Ｃ）の添加重量部の２倍を差し引いた値（ａ＋ｂ−２ｃ）が−１０〜１０であり、前記各化合物（Ａ）〜（Ｃ）の添加量（ａ、ｂ、ｃ）は少なくとも０．３重量部である。ａ＋ｂ−２ｃが−１０未満であると加硫に必要な時間が長く成りすぎて生産性が劣り、ａ＋ｂ−２ｃが１０を越えるとムーニースコーチ時間が短く成りすぎて加工性に難がある。ａ、ｂのいずれか一方でも０．３重量部未満である場合には熱安定効果が不十分であり、ｃが０．３重量部未満の場合には、ムーニースコーチ時間が短くなり加工性に劣る。
【００１９】
（試験方法）
＜混練＞
表面温度５０℃に調整されたミキシングロールに天然ゴムを巻き付け、このゴム材料１００重量部に対して、所定の熱安定剤２〜１７部、ＨＡＦ級カーボンブラック（ＣＢ）４０重量部、プロセスオイル（出光興産（株）ダイナプロセスオイルＡＨ−５８）５重量部、酸化亜鉛（ＺｎＯ）５重量部、ステアリン酸２重量部、所定の加硫促進剤２．５〜６重量部及び硫黄１重量部をこの順で逐次添加した。
【００２０】
＜ムーニー・スコーチタイム＞
ＪＩＳ Ｋ ６３００に準拠して、島津製作所（株）製ＳＭＶ−２００を用い１２５℃にて粘度が最低粘度から５ポイント（ムーニー単位）増加するまでの時間（分）を測定した。
【００２１】
＜９０％加硫時間ｔ９０の評価＞
ＡＳＴＭ Ｄ２０８４−７５に準拠して、レオメーター（東洋精機製作所（株）製ＯＤＲ−１００）を用い１５０℃にて９０％加硫時間（分）を測定した。これは、加硫温度（１５０℃）においてゲル化が開始する時間であり、加硫が終了するのに必要な時間（加硫時間）の指標となる。
【００２２】
＜引っ張り試験＞
混練終了後の未加硫ゴムをロールでシート状にし、熱プレスにて１５０℃３０分加熱して２ｍｍ厚の加硫ゴムのシートを得た。このシートを３号ダンベルで打ち抜いた試片について、東洋精機製作所（株）製ストログラフＲを用いて引っ張り試験を行った。これらはＪＩＳ Ｋ ６３０１に準拠して行った。
【００２３】
＜促進劣化試験＞
引っ張り試験用試験片を９０℃に調整した恒温乾燥機中１０００時間放置した。この後、上記引っ張り試験を行い、上記促進劣化前の値に対する保持率（％）を算出した。
【００２４】
また、混練終了後の未加硫ゴムを熱プレスにて１５０℃３０分圧縮成形して円柱形試片を作成し、上記と同様の促進劣化後に、ＪＩＳ Ｋ ６３０１に準拠して圧縮永久歪み（％）を測定した。
【００２５】
（実施例１〜９）
化合物（Ａ）として２−メルカプトベンゾイミダゾールの亜鉛塩（大内新興化学工業（株）ノクラックＭＢＺ）を用いた実施例について、添加剤配合量（天然ゴム１００重量部に対する添加重量部）と試験結果を表１にまとめて示す。
【００２６】
【表１】

表１の結果に示すように、ａ＋ｂ−２ｃが−１０〜１０、かつ、ａ、ｂ、ｃが０．５以上の条件で、促進劣化後の引っ張り強度及び伸び率の保持率が５０％前後又はそれ以上、圧縮永久歪みが５３％未満であり、ムーニースコーチタイムと９０％加硫時間がいずれも成形に適した範囲内であった。
【００２７】
（実施例１０〜１１）
化合物（Ａ）としてメチル−２−メルカプトベンゾイミダゾールの亜鉛塩を用いた実施例（実施例１０）、及び、４−，５−ジメチル−２−メルカプトベンゾイミダゾールの亜鉛塩を用いた実施例（実施例１１）について、添加剤配合量と試験結果を表２にまとめて示す。
【００２８】
【表２】

化合物（Ａ）の種類が異なる以外、添加剤配合が同一である実施例５の結果とほぼ同一の結果が得られた。特に、加硫ゴムについて得られた結果は測定誤差の範囲内で一致している。
【００２９】
（比較例１〜３）
熱安定剤としてＮ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン、２，２，４−トリメチル−１，２−ジヒドロキノリン重合体及び２−メルカプトベンゾイミダゾールをそれぞれ用いた従来技術による比較例を示す。
【００３０】
【表３】

表３の結果に示すように、芳香族第２級アミン単独（比較例１）、芳香族第２級アミンとアミン−ケトン系化合物との併用（比較例２）のいずれも促進劣化後における引っ張り強度及び伸び率の保持率が３０％前後またはそれ以下と低く熱安定性に問題があった。
【００３１】
一方、芳香族第２級アミンと２−メルカプトベンゾイミダゾールとの併用（比較例３）の場合、ムーニースコーチタイムが９分と極端に短いため、ゴム焼けが発生しやすく加工性に問題があった。また、圧縮永久歪みが７９％と極端に大きかった。
【００３２】
（比較例４〜７）
実施例１〜９と同様の添加剤配合であってａ＋ｂ−２ｃが−１０より小さい場合（比較例４）、及び、ａ＋ｂ−２ｃが１０より大きい場合（比較例５〜７）について表４にまとめて示す。
【００３３】
【表４】

ａ＋ｂ−２ｃの値が−１０より小さい場合（比較例４）には、９０％加硫時間が２１分であり、加硫時間が長く生産性が良くないことが知られた。また、促進劣化後における引っ張り強度及び伸び率の保持率が３３〜３５％と低く熱安定性に問題があった。これは本発明の評価方法で採用した１５０℃３０分の加熱時間では加硫が不十分であったことに起因すると考えられる。
【００３４】
ａ＋ｂ−２ｃの値が１０より大きい場合（比較例５〜７）には、ムーニースコーチタイムが１１分又は６分と極端に短いため、ゴム焼けが発生しやすく加工性に問題があった。
【００３５】
また、比較例５〜７の結果から知られるように、化合物（Ｃ）の量を減らして化合物（Ｃ）と同様にスルフェンアミド系である加硫促進剤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を加えた場合、化合物（Ｃ）の添加で見られたようなスコーチ防止効果が見られなかった。一方、一般的なスコーチ安定剤であるＮ−シクロヘキシルチオフタルイミドを加えても（比較例７）、加えなかった場合（比較例６）に比べてムーニースコーチタイムは全く改善されなかった。
【００３６】
表１及び４中に示した、実施例１〜８及び比較例４〜７におけるａ＋ｂ−２ｃの値とムーニースコーチタイム及び９０％加硫時間ｔ９０との関係について、図１にグラフで示す。９０％加硫時間が２０分未満であって加硫のための時間が適切であるためにはａ＋ｂ−２ｃの値が−１０より大きくなければならず、ムーニースコーチタイムが１５分以上であって加工性が適切であるためにはａ＋ｂ−２ｃの値が１０より小さくなければならない。
【００３７】
【発明の効果】
耐熱安定性に優れるとともに、スコーチ安定性及び成形品生産性に優れ圧縮永久変形の小さい防振ゴムを与える。
【図面の簡単な説明】
【図１】実施例及び比較例におけるａ＋ｂ−２ｃの値とムーニースコーチタイム及び９０％加硫時間ｔ９０との関係について示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composition for use in an anti-vibration rubber such as an automobile engine mount. In particular, the present invention relates to an anti-vibration rubber composition of natural rubber or other diene rubber.
[0002]
[Prior art]
Anti-vibration rubber is used for mounts such as engine mounts, dampers such as torsional dampers, and various bushes in order to absorb vibrations of automobiles and vehicles and prevent noise.
[0003]
As the rubber polymer component constituting the vibration-proof rubber, a diene rubber such as natural rubber having vibration-proof performance and resistance to repeated deformation is generally used. Usually, natural rubber alone or a rubber blend with other rubber mainly composed of natural rubber is blended and molded with an appropriate filler, oil agent, and the like.
[0004]
Since these diene rubbers are not inherently highly resistant to heat deterioration, a heat stabilizer is added for use in vibration-proof rubbers. In particular, anti-vibration rubber for automobiles such as engine mounts is used under severe conditions that continue to be heated, and long-term durability and reliability are required. Therefore, aromatic secondary amines such as N-phenyl-N′-isopropyl-paraphenylenediamine or 2-, 2-, 4-trimethyl-1,2-dihydro are particularly suitable as heat stabilizers. An amine-ketone compound such as quinoline is added.
[0005]
[Problems to be solved by the invention]
In recent years, as competition for performance between automakers intensified, anti-vibration rubber compositions blended with the above heat stabilizers have not always been able to adequately meet the demands for heat-resistant durability performance, which is becoming more severe every year. .
[0006]
In JP-A-3-146537, 2-mercaptobenzimidazole is proposed to be used in combination with a general amine heat stabilizer, and it is shown that the heat stability performance can be greatly improved.
[0007]
However, when 2-mercaptobenzimidazole is added to the diene rubber material, the scorch stability is extremely deteriorated, so that it is difficult to industrially use it. Further, compression permanent deformation after use under heating ( There was a problem that the size was extremely large.
[0008]
In view of the above-mentioned problems, the present invention provides a composition that provides a vibration-proof rubber having excellent heat stability and scorch stability and small compression set.
[0009]
In the present specification, the terms “thermal degradation” and “thermal stabilizer” include oxidative degradation promoted by heat and a stabilizer for the degradation.
[0010]
[Means for Solving the Problems]
The anti-vibration rubber composition according to claim 1 has the following features (1) to (3).
[0011]
(1) The rubber polymer component is a diene rubber,
(2) including a compound (A) represented by the following general formula (I), a compound (B) represented by the following chemical formula (II), and a compound (C) represented by the following chemical formula (III),
(3) The added weight parts a, b and c of the respective compounds (A) to (C) with respect to 100 parts by weight of the diene rubber satisfy the following formulas (i) to (ii).
[0012]
−10 ≦ a + b−2c ≦ 10 (i)
a, b, c ≧ 0.3 (ii)
[Chemical formula 2]

With the above configuration, a vibration-proof rubber having excellent heat resistance stability, excellent scorch stability and molded product productivity and small compression set is provided.
[0013]
The anti-vibration rubber composition according to claim 2, wherein in the anti-vibration rubber composition according to claim 1, the diene rubber is natural rubber or a rubber blend containing 50% by weight or more of natural rubber. Features.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The rubber polymer component used in the vibration-proof rubber composition of the present invention is a diene rubber.
[0015]
As the diene rubber, any of general rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and blends thereof can be used. Preferably, natural rubber alone or a rubber blend with other diene rubber mainly composed of natural rubber. As the rubber blend, for example, a blend of natural rubber and butadiene rubber at a weight ratio of 80/20 is preferable.
[0016]
The heat stabilizer compound used in the vibration-proof rubber composition of the present invention includes a compound (A) represented by the following general formula (I) (zinc salt of 2-mercaptobenzimidazole or a methylated derivative thereof) and the following chemical formula: Compound (B) (4,4′-bis (α, α′-dimethylbenzyl) diphenylamine) represented by (II) and compound (C) represented by the following chemical formula (III) (N-tert-butyl) -Di- (2-benzthiazolesulfenamide)).
[0017]
[Chemical 3]

In each of the compounds (A) to (C), the addition parts a, b and c satisfy the following formulas (i) to (ii) with respect to 100 parts by weight of the rubber polymer component, that is, 100 parts by weight of the diene rubber.
[0018]
−10 ≦ a + b−2c ≦ 10 (i)
a, b, c ≧ 0.3 (ii)
That is, a value (a + b-2c) obtained by subtracting twice the added weight part of the compound (C) from the total added weight part of the compound (A) and the compound (B) with respect to 100 parts by weight of the rubber polymer component is -10 to 10. 10 and the addition amount (a, b, c) of each of the compounds (A) to (C) is at least 0.3 parts by weight. If a + b-2c is less than −10, the time required for vulcanization becomes too long and the productivity is inferior. If a + b−2c exceeds 10, the Mooney scorch time becomes too short and the workability is difficult. When either a or b is less than 0.3 parts by weight, the thermal stability effect is insufficient, and when c is less than 0.3 parts by weight, the Mooney scorch time is shortened and workability is reduced. Inferior.
[0019]
(Test method)
<Kneading>
Natural rubber is wrapped around a mixing roll adjusted to a surface temperature of 50 ° C., and 2 to 17 parts of a predetermined heat stabilizer, 40 parts by weight of HAF grade carbon black (CB), process oil Idemitsu Kosan Co., Ltd. Dyna Process Oil AH-58) 5 parts by weight, zinc oxide (ZnO) 5 parts by weight, stearic acid 2 parts by weight, predetermined vulcanization accelerator 2.5-6 parts by weight and sulfur 1 part by weight Sequential additions were made in this order.
[0020]
<Mooney Scorch Time>
Based on JIS K 6300, SMV-200 manufactured by Shimadzu Corporation was used to measure the time (min) until the viscosity increased 5 points (Mooney unit) from the lowest viscosity at 125 ° C.
[0021]
<Evaluation of 90% vulcanization time t90>
Based on ASTM D2084-75, 90% vulcanization time (min) was measured at 150 ° C. using a rheometer (ODR-100 manufactured by Toyo Seiki Seisakusho Co., Ltd.). This is the time at which gelation starts at the vulcanization temperature (150 ° C.), and is an indicator of the time required to complete vulcanization (vulcanization time).
[0022]
<Tensile test>
The unvulcanized rubber after kneading was formed into a sheet with a roll and heated at 150 ° C. for 30 minutes with a hot press to obtain a vulcanized rubber sheet having a thickness of 2 mm. About the test piece which punched this sheet | seat with the No. 3 dumbbell, the tension test was done using Toyo Seiki Seisakusho Co., Ltd. strograph R. These were performed in accordance with JIS K 6301.
[0023]
<Accelerated deterioration test>
The tensile test specimen was left in a constant temperature dryer adjusted to 90 ° C. for 1000 hours. Then, the said tension test was done and the retention (%) with respect to the value before the said accelerated deterioration was computed.
[0024]
Further, the unvulcanized rubber after kneading is compression-molded at 150 ° C. for 30 minutes by a hot press to prepare a cylindrical specimen, and after accelerated deterioration similar to the above, compression set (in accordance with JIS K 6301) %).
[0025]
(Examples 1-9)
About the Example using the zinc salt of 2-mercaptobenzimidazole (Ouchi Shinsei Chemical Co., Ltd. NOCRACK MBZ) as a compound (A), additive compounding quantity (added weight part with respect to 100 weight part of natural rubber), and test result Are summarized in Table 1.
[0026]
[Table 1]

As shown in the results in Table 1, the tensile strength and elongation retention after accelerated deterioration are around 50% under the conditions that a + b-2c is −10 to 10 and a, b, and c are 0.5 or more. Or more than that, the compression set was less than 53%, and both Mooney scorch time and 90% vulcanization time were within the range suitable for molding.
[0027]
(Examples 10 to 11)
Example (Example 10) using a zinc salt of methyl-2-mercaptobenzimidazole as the compound (A) and Example (Example) using a zinc salt of 4-, 5-dimethyl-2-mercaptobenzimidazole Table 2 summarizes the additive blending amounts and test results for Example 11).
[0028]
[Table 2]

Except for the difference in the type of compound (A), almost the same result as that of Example 5 in which the additive composition was the same was obtained. In particular, the results obtained for the vulcanized rubber agree within the measurement error.
[0029]
(Comparative Examples 1-3)
N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 2-mercaptobenzimidazole are used as heat stabilizers, respectively. The comparative example by the prior art which has been shown.
[0030]
[Table 3]

As shown in the results of Table 3, both the aromatic secondary amine alone (Comparative Example 1) and the combined use of the aromatic secondary amine and the amine-ketone compound (Comparative Example 2) are tensile after accelerated deterioration. There was a problem in thermal stability because the strength and elongation retention were as low as about 30% or less.
[0031]
On the other hand, in the case of the combined use of an aromatic secondary amine and 2-mercaptobenzimidazole (Comparative Example 3), the Mooney scorch time was extremely short as 9 minutes, so that rubber burn was likely to occur and there was a problem in processability. . Further, the compression set was extremely large at 79%.
[0032]
(Comparative Examples 4-7)
Table 4 shows the same additive composition as in Examples 1 to 9 when a + b-2c is smaller than -10 (Comparative Example 4) and when a + b-2c is larger than 10 (Comparative Examples 5-7). Shown together.
[0033]
[Table 4]

When the value of a + b-2c was smaller than −10 (Comparative Example 4), it was known that the 90% vulcanization time was 21 minutes, and the vulcanization time was long and the productivity was not good. In addition, the tensile strength and elongation retention after accelerated deterioration were as low as 33 to 35%, and there was a problem in thermal stability. This is considered to be due to insufficient vulcanization at the heating time of 150 ° C. for 30 minutes employed in the evaluation method of the present invention.
[0034]
When the value of a + b-2c was larger than 10 (Comparative Examples 5 to 7), the Mooney scorch time was extremely short as 11 minutes or 6 minutes, so that rubber burn was likely to occur and there was a problem in workability.
[0035]
Further, as is known from the results of Comparative Examples 5 to 7, the amount of the compound (C) is reduced, and the vulcanization accelerator N-cyclohexyl-2-benzothiazoli which is a sulfenamide type as in the compound (C). When rusulfenamide was added, the scorch prevention effect as seen with the addition of compound (C) was not observed. On the other hand, even when N-cyclohexylthiophthalimide, which is a general scorch stabilizer, was added (Comparative Example 7), the Mooney scorch time was not improved at all as compared with the case where N-cyclohexylthiophthalimide was not added (Comparative Example 6).
[0036]
The relationship between the values of a + b-2c, Mooney scorch time, and 90% vulcanization time t90 in Examples 1-8 and Comparative Examples 4-7 shown in Tables 1 and 4 is shown graphically in FIG. In order for the 90% vulcanization time to be less than 20 minutes and the time for vulcanization to be adequate, the value of a + b-2c must be greater than −10 and the Mooney scorch time is 15 minutes or more. In order for workability to be appropriate, the value of a + b−2c must be less than 10.
[0037]
【The invention's effect】
An anti-vibration rubber having excellent heat resistance stability, scorch stability and molded product productivity, and small compression set.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the value of a + b−2c, Mooney scorch time, and 90% vulcanization time t90 in Examples and Comparative Examples.

Claims (2)

An anti-vibration rubber composition having the following features (1) to (3).
(1) The rubber polymer component is a diene rubber,
(2) including a compound (A) represented by the following general formula (I), a compound (B) represented by the following chemical formula (II), and a compound (C) represented by the following chemical formula (III),
(3) The added weight parts a, b and c of the respective compounds (A) to (C) with respect to 100 parts by weight of the diene rubber satisfy the following formulas (i) to (ii).
−10 ≦ a + b−2c ≦ 10 (i)
a, b, c ≧ 0.3 (ii)

In the vibration-proof rubber composition according to claim 1,
The anti-vibration rubber composition, wherein the diene rubber is natural rubber or a rubber blend containing 50% by weight or more of natural rubber.

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