JP3559077B2 - Gear oil composition - Google Patents

Description

【００１４】
一般式（１）中、Ｒ１、Ｒ２、Ｒ３およびＲ４は、それぞれ同一または相異なる炭素数１０以上のアルキル基が好ましい。
炭素数１０未満のアルキル基のものは、耐摩耗性、耐酸化性が小さく、炭素数が多すぎるアルキル基のものでも、同様に、耐摩耗性、耐酸化性が小さくなるため、アルキル基の炭素数の上限は２０程度とすることが適している。
アルキル基の好ましい炭素数は１０〜１８、より好ましくは１１〜１４であり、例えば、デシル基、ドデシル基、テトラシル基、ヘキサデシル基などが挙げられる。
【００１５】
上記のジアルキルジチオリン酸亜鉛は、単独でまたは２種以上を混合して使用でき、その配合割合は、０．５〜３．０重量％、好ましくは１．０〜２．０重量％である。
ジアルキルジチオリン酸亜鉛が少なすぎると、耐ピッチング性、シンクロ特性および極圧性が低下し、多すぎてもこの効果は飽和し、経済的に不利である。
【００１６】
（Ｂ）成分の塩基価が２００ｍｇＫＯＨ／ｇ以上のアルカリ土類金属型清浄分散剤は、従来よりエンジン油に使用されている公知のものを使用することができる。
塩基価が２００ｍｇＫＯＨ／ｇ未満のものであると、耐ピッチング性を優れたものとすることができず、また硫黄−リン系極圧剤を配合する場合においては、金属腐食，スラッジの生成を抑制し、耐ピッチング性を向上させることができない。
【００１７】
なお、塩基価の上限は、特に限定しないが、あまり高すぎると分散性に悪影響を及ぼすため、６００ｍｇＫＯＨ／ｇ程度を上限とするのが好ましい。
好ましい塩基価は、２５０〜４５０ｍｇＫＯＨ／ｇ、より好ましくは３００〜４５０ｍｇＫＯＨ／ｇである。
【００１８】
このようなアルカリ土類金属型清浄分散剤の具体例としては、スルフォネート、フェネート、サリチレート、ホスフォネートなどと、Ｃａ、Ｍｇ、Ｂａなどとの金属塩形になっているものが挙げられる。
また、Ｃａ、Ｍｇ、Ｂａなどの水酸化物や炭酸塩を過剰に含有させた超塩基性清浄分散剤も使用できる。
好ましくはスルフォネートとＣａ、Ｍｇ、Ｂａなどとの金属塩であり、より好ましくはＭｇスルフォネートであり、特に好ましくはＣａスルフォネートとＭｇスルフォネートを重量比で１：０．８〜１：１０、好ましくは１：１〜１：８、より好ましくは１：２〜１：６の割合で併用したものである。
【００１９】
上記のアルカリ土類金属型清浄分散剤は、単独でまたは２種以上を混合して使用でき、その配合割合は、１．２〜４．０重量％、好ましくは１．５〜２．５重量％である。
アルカリ土類金属型清浄分散剤が少なすぎると、耐ピッチング性および清浄性が低下し、多すぎてもこの効果は飽和し、経済的に不利である。
【００２０】
（Ｃ）成分のアルケニルこはく酸イミドまたはその誘導体は、平均分子量が２０００〜５０００、好ましくは２０００〜３０００、さらに好ましくは２３００〜２５００のポリブテニル基を有するビスタイプのものであり、化２の一般式（２）で表される。なお、（Ｃ）成分の平均分子量は、２０００未満であると充分な耐ピッチング性が得られず、５０００を超えると油への溶解性が悪くなる。
【００２１】
【化２】

【００２２】
化２の一般式（２）中、Ｒ５はアルケニル基であるポリブテニル基で、上記した平均分子量のものを表し、Ｒ６は炭素数２〜５の２価の飽和脂肪族炭化水素を表し、ｘは０〜１０の整数を表す。
【００２３】
一般式（２）で表されるビスタイプのアルケニルこはく酸イミドまたはその誘導体は、一般には、ポリブテンと無水マレイン酸との反応で得られるポリブテニルコハク酸無水物と、ポリアミンとの反応によって合成される。
このポリアミンの例としては、単一ジアミン、例えば、エチレンジアミン、プロピレンジアミン、ブチレンジアミン、ペンチレンジアミンなど；ポリアルキレンポリアミン、例えば、ジエチレントリアミン、トリエチレンテトラアミン、テトラエチレンペンタミン、ペンタエチレンヘキサミン、ジ（メチルエチレン）トリアミン、ジブチレントリアミン、トリブチレンテトラミン、ペンタペンチレンヘキサミンなど、が挙げられる。
【００２４】
また、ビスタイプのアルケニルこはく酸イミドのホウ素化合物誘導体、有機ホスフォネート誘導体等、あるいはビスタイプのアルケニルこはく酸イミドをアルデヒド、ケトン、カルボン酸、スルホン酸、アルキレンオキシド、硫黄等と反応させたビスタイプのアルケニルこはく酸イミドの誘導体も使用できる。
【００２５】
上記のビスタイプのアルケニルこはく酸イミド、その誘導体は、それぞれ単独で、あるいは２種類以上を混合して使用することができ、その配合割合は、４〜１５重量％、好ましくは５〜１０重量％である。
ビスタイプのアルケニルこはく酸イミド、その誘導体が少なすぎると、耐ピッチング性が低下し、多すぎても、この効果は飽和し、経済的に不利となる。
【００２６】
以上の（Ａ）〜（Ｃ）成分とともに、配合される任意成分である（Ｄ）成分の硫黄−リン系極圧剤は、１つの化合物中に硫黄とリンとを含むものであってもよいし、いずれか一方を含むいわゆる硫黄系極圧剤とリン系極圧剤とを混合したものであってもよい。
【００２７】
上記の硫黄系極圧剤としては、化３の一般式（３）で表される炭化水素硫化物、硫化テルペン、油脂と硫黄との反応生成物である硫化油脂などが使用される。
【００２８】
【化３】
一般式（３）
Ｒ７−Ｓ_ｙ−（Ｒ９−Ｓ_ｙ）_ｎ−Ｒ８
【００２９】
化３の一般式（３）中、Ｒ７、Ｒ８は一価の炭化水素基で、それぞれ同一でも異なっていてもよく、Ｒ９は二価の炭化水素基、ｙは１以上の整数で、好ましくは１〜８で、繰り返し単位中においてそれぞれのｙが同一または異なる数であることもあり、ｎは０または１以上の整数である。
【００３０】
上記Ｒ７、Ｒ８の一価の炭化水素基としては、炭素数２〜２０の直鎖または分枝の飽和または不飽和脂肪族炭化水素基（例えば、アルキル基、アルケニル基）、炭素数６〜２６の芳香族炭化水素基が挙げられ、具体的には、エチル基、プロピル基、ブチル基、ノニル基、ドデシル基、プロペニル基、ブテニル基、ベンジル基、フェニル基、トリル基、ヘキシルフェニル基などが挙げられる。
【００３１】
上記Ｒ９の二価の炭化水素基としても、炭素数２〜２０の直鎖または分枝の飽和または不飽和脂肪族炭化水素基、炭素数６〜２６の芳香族炭化水素基が挙げられ、具体的には、エチレン基、プロピレン基、ブチレン基、フェニレン基などが挙げられる。
【００３２】
化（３）の一般式（３）で表される炭化水素硫化物の代表的なものは、硫黄オレフィンおよび一般式Ｒ７−Ｓ_ｙ−Ｒ８（ｙは２以上の整数）で示されるポリサルファイド化合物である。
具体的には、ジイソブチルジサルファイド、ジオクチルポリサルファイド、ジターシャリーノニルポリサルファイド、ジターシャリーブチルポリサルファイド、ジターシャリーベンジルポリサルファイド、あるいはポリイソブチレンやテルペン類などのオレフィン類を硫黄などの硫化剤で硫化した硫化オレフィン類などが挙げられる。
【００３３】
油脂と硫黄との反応生成物である硫化油脂は、油脂としてラード、牛脂、鯨油、パーム油、ヤシ油、なたね油などの動植物油脂を使用したものであり、この反応生成物は、化学構造が単一ではなく、種々の混合物であり、化学構造そのものは明確ではない。
【００３４】
また、リン系極圧剤または、硫黄−リン系極圧剤（１つの化合物中に硫黄とリンとを含むもの）としては、化４の硫黄−リン系極圧剤（４）で表されるリン酸エステル、亜リン酸エステル、チオリン酸エステル、ジチオリン酸エステルなどが挙げられる。
【００３５】
【化４】
一般式（４）
（Ｒ１０）_ａＨ_３−ａＸ_３ＰＸ_ｂ
【００３６】
化４の一般式（４）中、Ｒ１０は一価の炭化水素基、Ｘは酸素原子または硫黄原子、ａは１，２または３、ｂは０または１である。
【００３７】
上記Ｒ１０としては、炭素数５〜２０の直鎖または分枝の飽和または不飽和脂肪族炭化水素基（例えば、アルキル基、アルケニル基）、炭素数６〜２６の芳香族炭化水素基、シクロアルキル基が挙げられる。
【００３８】
化（４）の一般式（４）で表されるエステル硫化物の具体例としては、リン酸モノオクチル、リン酸ジオクチル、リン酸トリオクチル、亜リン酸ジオクチル、亜リン酸トリオクチル、チオリン酸ジオクチル、チオリン酸トリオクチル、リン酸ジデシル、亜リン酸ジデシル、リン酸ジドデシル、リン酸トリドデシル、亜リン酸ジドデシル、亜リン酸トリドデシル、チオリン酸トリドデシル、リン酸トリヘキサデシル、亜リン酸トリヘキサデシル、チオリン酸トリヘキサデシル、リン酸トリオクタデセニル、亜リン酸トリオクタデセニル、チオリン酸トリオクタデセニル、リン酸トリ（オクチルフェニル）、リン酸トリ（オクチルシクロヘキシル）、ジチオリン酸トリデシルなどが挙げられる。
【００３９】
また、リン系極圧剤は、化４の一般式（４）で表される酸性リン酸エステル、酸性亜リン酸エステル、酸性チオリン酸エステル、酸性ジチオリン酸エステル、のアルキルアミン塩なども使用することができる。
【００４０】
これらのアルキルアミン塩の具体例としては、酸性エステルとして、ブチルアシッドホスフェート、２−エチルヘキシルアシッドホスフェート、オクチルアシッドホスフェート、ラウリルアシッドホスフェート、オレイルアシッドホスフェート、トリールアシッドホスフェートなどが挙げられる。
これらを中和するためのアルキルアミンとしては、一般式ＮＲ１１Ｒ１２Ｒ１３（式中、Ｒ１１、Ｒ１２およびＲ１３は一価の炭化水素基または水素原子であり、そのうち少なくとも１つは炭化水素基である）で表され、具体的には、ジブチルアミン、オクチルアミン、ジオクチルアミン、ラウリルアミン、ジラウリルアミン、ココナッツアミン、牛脂アミンなどが挙げられる。
【００４１】
以上（Ｄ）成分である硫黄−リン系極圧剤の配合割合は、２〜１０重量％、好ましくは３〜７重量％である。
硫黄−リン系極圧剤が少なすぎると、ハイポイドギヤを装着したトランスアクスルに使用する場合、極圧性が低く、ギヤの損傷、焼き付きなどを引き起こし、多すぎると、シンクロ特性および酸化安定性に悪影響を及ぼす。
【００４２】
上記した（Ａ）〜（Ｃ）成分、または（Ａ）〜（Ｄ）成分の他に、本発明のギヤ油組成物においては、目的に応じて、通常使用されている（Ａ）〜（Ｄ）成分以外の公知の添加剤、例えば、無灰型分散剤、摩擦調整剤、酸化防止剤、腐食防止剤、粘度指数向上剤、流動点降下剤、消泡剤などを配合することもできる。
【００４３】
このうち無灰型分散剤としては、アルケニルこはく酸エステル、長鎖脂肪酸とポリアミンとのアミド（アミノアミド型）などが、摩擦調整剤としては、脂肪酸、有機モリブデン化合物などが、酸化防止剤としては、アミン系、フェノール系のものなどが、腐食防止剤としては、ベンゾトリアゾール、アルケニルこはく酸エステルなどが、粘度指数向上剤としては、ポリメタクリレート、オレフィンコポリマーなどが、流動点降下剤としては、ポリメタクリレートなどが、消泡剤としては、シリコン化合物、エステル系のものなど、がそれぞれ使用できる。
【００４４】
以上詳述した本発明のギヤ油組成物は、（Ａ）〜（Ｃ）成分の相互作用により耐ピッチング性、シンクロ特性、極圧性、酸化安定性に優れたものとなり、またこれら（Ａ）〜（Ｃ）成分と（Ｄ）成分とを配合すると、（Ｄ）成分による金属腐食に起因するトランスミッションのトラブル、スラッジの生成を抑制し、優れた極圧性を得ることができる。
【００４５】
【実施例】
実施例１〜６、比較例１〜１２
パラフィン系基油（８０ニュートラル）に、表１〜６に示す各成分を同表に示す割合で配合して、本発明のギヤ油組成物を調製し、これらのギヤ油組成物につき、次の性能試験を行った。この結果を、表１〜６に合わせて示す。
【００４６】
〔耐ピッチング性試験〕
耐ピッチング性の評価として、四円筒試験を行った。四円筒試験の試験条件および疲労寿命の判定法は、次の通りとした。
【００４７】
（試験条件）
回転数：１０００ｒｐｍ
滑り率：３０％
接触圧力：６５ｋｇ／ｍｍ^２
油温：８０℃
【００４８】
（疲労寿命の判定法）
運転開始から１０万サイクル毎に試験機を停止し、肉眼で観察できる損傷（ピッチング）が発生するまでのサイクル数を疲労寿命とした。すなわち、サイクル数が多いほど疲労寿命が長く、かつ耐ピッチング性も優れることになる。
本試験では、疲労寿命７０万サイクル以上を合格とした。
【００４９】
〔シンクロ特性試験〕
先ず、シンクロナイザーリングとギヤコーンを台上に設置し、ギヤコーンの回転数をモーターにより１２００ｒｐｍに維持する。
次いで、シンクロナイザーリングを４０ｋｇｆの荷重にて押し付ける。
その後、シンクロナイザーリングの荷重を取り除き、ギヤコーンからシンクロナイザーリングを切り離す。
このシンクロナイザーリングの押し付けと切り離しとからなるパターンを、１００００サイクル繰り返す。
【００５０】
上記の繰り返しにおいて、シンクロナイザーリングを押し付けた時に発生するトルクを測定し、摩擦係数を求めた。
この摩擦係数を、１００サイクルと１００００サイクルとで比較し、摩擦係数の高低で評価した。すなわち、摩擦係数が高く、かつ１００００サイクル後でもこの高い摩擦係数を維持できるものをシンクロ特性が優れるものとした。
本試験では、１００００サイクル後の摩擦係数が０．１００以上を有するものを合格とした。
【００５１】
〔極圧性試験〕
次の試験条件にてギヤ試験を行った。なお、ＩＡＥギヤ試験は、ＩＰ（イギリス石油協会規格）法のＩＰ１６６／６８に従って行い、焼き付き限界荷重を測定した。
【００５２】
（試験条件）
小歯車回転数：６０００ｒｐｍ
給油温度：１１０℃
給油方法：強制給油
給油量：０．５６リットル／分
運転方法：５分毎のステップ荷重増加法（すなわち、１０ポンドの荷重で運転を開始し、５分毎に５ポンドづつ荷重を増加させた。）
【００５３】
〔酸化安定性試験〕
内燃機関用潤滑油安定度試験法（ＪＩＳ Ｋ ２５４１）に準拠し、１５０℃、９６ｈｒの条件で行った。
評価は、粘度増加、全酸価増加およびスラッジの有無で行った。
【００５４】
なお、表１〜６中の＊１〜＊１１は、次の意味を有する。
＊１：第２級アルキル基を有するアルキルジチオリン酸亜鉛
＊２：塩基価３９８ｍｇＫＯＨ／ｇのＭｇスルフォネート
＊３：塩基価３００ｍｇＫＯＨ／ｇのＣａスルフォネート
＊４：塩基価２９ｍｇＫＯＨ／ｇのＣａスルフォネート
＊５：ポリブテニル基の平均分子量が２４００のビスタイプアルケニルこはく酸イミド
＊６：ポリブテニル基の平均分子量が１９００のビスタイプアルケニルこはく酸イミド
＊７：ポリブテニル基の平均分子量が７００のモノタイプアルケニルこはく酸イミド
＊８：硫化油脂、硫化オレフィン、リン酸エステルアミン塩からなる極圧剤（Ｓ＝２２．９重量％、Ｐ＝１．４重量％）
＊９：その他の添加剤
＊１０：硫黄系極圧剤を含まない市販のトランスミッションギヤ油（ＧＬ−３ ７５Ｗ８５）
＊１１：硫黄−リン系極圧剤を含む市販のトランスミッションギヤ油（ＧＬ−３ ９０）
【００５５】
【表１】

【００５６】
【表２】

【００５７】
【表３】

【００５８】
【表４】

【００５９】
【表５】

【００６０】
【表６】

【００６１】
なお、以上の結果から、硫黄−リン系極圧剤を配合した実施例６（表２）において、シンクロ特性を損なうことなく、しかもスラッジの生成を抑えて、優れた極圧性を示すことが分かる。
【００６２】
【発明の効果】
以上詳述したように、本発明のギヤ油組成物は、優れた極圧性、酸化安定性、シンクロ特性を有するとともに、耐ピッチング性にも優れ、長い疲労寿命を有するものである。
したがって、本発明のギヤ油組成物は、最近の高トルク化に伴い大きな負荷がかかり、優れた耐ピッチング性、シンクロ特性、極圧性、酸化安定性の要求される自動車用マニュアルトランスミッションギヤ用として好適であり、また硫黄−リン系極圧剤を配合した組成のものについては、これらの特性の他にさらに高い極圧性が要求されるハイポイドギヤを装着したトランスアクスル用のギヤ油として好適である。[0001]
[Industrial applications]
The present invention relates to a gear oil composition, and more particularly to a gear oil composition having excellent abrasion resistance, oxidation stability, and synchro properties, and further significantly improving pitting resistance, and containing a sulfur-phosphorus extreme pressure agent. The present invention relates to a manual transmission for an automobile and a gear oil composition for a transaxle having excellent extreme pressure characteristics while maintaining these excellent characteristics.
[0002]
2. Description of the Related Art
Gear oils that have been used in the past have an object of forming an oil film between metals in various devices and suppressing tooth surface damage such as wear, seizure, pitching, and scoring.
This gear oil is usually a mixture of mineral oil or synthetic oil as a base oil and various additives depending on the purpose.
[0003]
In recent years, in automotive gears, the load on the gears has been increased with the increase in engine torque, which may cause various troubles.
Among them, there are more gear troubles due to fatigue in metal, that is, pitching, as compared with wear and scoring.
For this reason, gear oils for automobiles that have higher anti-fatigue properties (pitting resistance) have been demanded.
[0004]
In order to meet this demand, usually, additives such as extreme pressure agents and antiwear agents are blended, while a paraffinic mineral oil having a high viscosity index and more excellent oxidation stability is used as a base oil. .
However, the gear oil using the base oil and the additive has a problem that the pitting resistance is insufficient under conditions involving high contact stress and high sliding speed.
[0005]
Further, gear oil used for a transaxle equipped with a hypoid gear requires a high extreme pressure property. Therefore, a sulfur-phosphorus extreme pressure agent is particularly blended.
However, this sulfur-phosphorus extreme pressure agent causes problems such as metal corrosion and sludge formation, and causes a decrease in the coefficient of friction or abnormal wear at the synchronizer ring and gear cone in the transmission synchromesh mechanism, and synchronization occurs. Failures may occur, causing problems such as an increase in shift force and, consequently, a shift being impossible.
[0006]
Recently, (1) a base oil having a specific kinematic viscosity is added to (a) zinc dithiophosphate, (b) an alkaline earth metal-based detergent and dispersant having a base number of less than 200 mgKOH / g, and (c) succinimide. A gear oil composition (see JP-A-2-155988), (2) a base oil having a specific kinematic viscosity, (a) a sulfur-containing compound such as zinc dithiophosphate, and (b) a base. Earth oil based detergent and dispersant having a value of 200 mgKOH / g or more, and a specific amount of (c) a partial ester of a polyhydric alcohol are blended in a specific amount to provide a lubricating oil composition for power control (see JP-A-2-155987). Have been.
However, these previously proposed gear oils have not been sufficient to prevent pitching, which has hitherto been a problem in the market.
[0007]
In consideration of the above-mentioned circumstances, the present invention maintains the excellent extreme pressure property, oxidation stability, and synchro properties of conventional gear oils as it is, and also provides excellent pitting resistance and fatigue life. A gear oil composition which can effectively prevent metal corrosion and sludge formation when it contains a sulfur-phosphorus extreme pressure agent, and which has a composition different from that of the above-mentioned prior proposal. The purpose is to provide things.
[0008]
[Means for Solving the Problems]
The present inventors have repeatedly studied to achieve the above object, and have obtained the following findings.
(I) An alkaline earth metal-based detergent / dispersant having a base number of 200 mgKOH / g or more, which is a component (b) in the power control lubricating oil composition of the above-mentioned proposal (2), has excellent pitting resistance. And
(Ii) However, when the base number of the alkaline earth metal-based detergent / dispersant is 200 mgKOH / g or more, it becomes difficult to select the component (c), that is, the pitting resistance of the mono-type succinimide is reduced. (Incidentally, in the gear oil composition of the above-mentioned proposal (1) using succinimide as the component (c), the alkaline earth metal type detergent / dispersant of the component (b) is used. In the above-mentioned power control lubricating oil composition of the above-mentioned proposal (2), a base oil having a base number of less than 200 mgKOH / g is used, and an alkaline earth metal-based detergent / dispersant having a base number of 200 mgKOH / g or more is used. , (C) a polyhydric alcohol partial ester is used as a component).
(Iii) Therefore, as a result of further study, the use of bis-type alkenyl succinimide having a polybutenyl group having a specific molecular weight as a component (c) or a derivative thereof achieves all of the above objects of the present invention. To get.
(Iv) When a sulfur-phosphorus extreme pressure agent is further contained, excellent pitting resistance is maintained without causing metal corrosion and sludge formation by synergistic action with the components (a) to (c). And obtain high extreme pressure.
[0009]
The gear oil composition of the present invention is based on the above findings,
[1] At least one selected from mineral oil and synthetic oil having a viscosity of 2 to 50 cSt at 100 ° C. is used as a base oil,
(A) 0.5 to 3.0% by weight of zinc alkyldithiophosphate;
(B) 1.2 to 4.0% by weight of an alkaline earth metal type detergent / dispersant having a base number of 200 mgKOH / g or more;
(C) a bis-type alkenyl succinimide having a polybutenyl group having an average molecular weight of 2,000 to 5,000, a derivative thereof of 4 to 15% by weight,
Or [2] the base oil contains (D) 2 to 10% by weight of a sulfur-phosphorus extreme pressure agent together with the components (A) to (C),
It is characterized by.
[0010]
The gear oil composition of the present invention comprising the above components has properties to be provided as a manual transmission oil, that is,
1) It has an appropriate coefficient of friction between the synchronizer ring and the gear cone.
2) maintain this coefficient of friction for a long time,
3) Excellent in extreme pressure and wear resistance
4) excellent oxidation stability;
5) Excellent pitting resistance,
have.
[0011]
The base oil used in the gear oil of the present invention is selected from mineral lubricating oils having a viscosity at 100 ° C of 2 to 50 cSt or purified products thereof, and synthetic lubricating oils having a viscosity at 100 ° C of 2 to 50 cSt. More than a species.
[0012]
The zinc dialkyldithiophosphate of the component (A) blended in the above base oil is represented by the general formula (1).
[0013]
Embedded image

[0014]
In the general formula (1), R1, R2, R3 and R4 are preferably the same or different alkyl groups having 10 or more carbon atoms.
Alkyl groups having less than 10 carbon atoms have low abrasion resistance and oxidation resistance. Even alkyl groups having too many carbon atoms have low abrasion resistance and oxidation resistance. The upper limit of the number of carbon atoms is preferably about 20.
The preferred carbon number of the alkyl group is 10 to 18, more preferably 11 to 14, and examples thereof include a decyl group, a dodecyl group, a tetrasil group, and a hexadecyl group.
[0015]
The above zinc dialkyldithiophosphates can be used alone or as a mixture of two or more kinds, and the compounding ratio is 0.5 to 3.0% by weight, preferably 1.0 to 2.0% by weight.
If the amount of zinc dialkyldithiophosphate is too small, the pitting resistance, the synchronizing property and the extreme pressure property decrease, and if the amount is too large, this effect is saturated, which is economically disadvantageous.
[0016]
As the alkaline earth metal type detergent / dispersant having a component (B) having a base number of 200 mg KOH / g or more, a known one conventionally used in engine oils can be used.
If the base number is less than 200 mgKOH / g, the pitting resistance cannot be improved, and when a sulfur-phosphorus extreme pressure agent is blended, metal corrosion and generation of sludge are suppressed. However, the pitting resistance cannot be improved.
[0017]
The upper limit of the base number is not particularly limited, but if it is too high, the dispersibility is adversely affected. Therefore, the upper limit is preferably about 600 mg KOH / g.
Preferred base numbers are from 250 to 450 mg KOH / g, more preferably from 300 to 450 mg KOH / g.
[0018]
Specific examples of such alkaline earth metal type detergent / dispersants include those in the form of metal salts of sulfonates, phenates, salicylates, phosphonates and the like, and Ca, Mg, Ba and the like.
Further, an ultra-basic detergent / dispersant containing an excess of hydroxides or carbonates such as Ca, Mg and Ba can also be used.
It is preferably a metal salt of sulfonate and Ca, Mg, Ba or the like, more preferably Mg sulfonate, particularly preferably a Ca sulfonate and Mg sulfonate in a weight ratio of 1: 0.8 to 1:10, preferably 1 to 1. : 1 to 1: 8, more preferably 1: 2 to 1: 6.
[0019]
The above alkaline earth metal type detergents / dispersants can be used alone or in combination of two or more, and the compounding ratio is 1.2 to 4.0% by weight, preferably 1.5 to 2.5% by weight. %.
If the amount of the alkaline earth metal type detergent / dispersant is too small, the pitting resistance and the detergency will be reduced.
[0020]
The alkenyl succinimide or a derivative thereof as the component (C) is a bis-type having a polybutenyl group having an average molecular weight of 2,000 to 5,000, preferably 2,000 to 3,000, and more preferably 2,500 to 2,500. It is represented by (2). If the average molecular weight of the component (C) is less than 2,000, sufficient pitting resistance cannot be obtained, and if it exceeds 5,000, the solubility in oil deteriorates.
[0021]
Embedded image

[0022]
In the general formula (2) of Chemical Formula 2, R5 represents a polybutenyl group which is an alkenyl group and has the above-mentioned average molecular weight, R6 represents a divalent saturated aliphatic hydrocarbon having 2 to 5 carbon atoms, and x represents Represents an integer of 0 to 10.
[0023]
A bis-type alkenyl succinimide represented by the general formula (2) or a derivative thereof is generally synthesized by a reaction of polybutenyl succinic anhydride obtained by the reaction of polybutene and maleic anhydride with a polyamine. Is done.
Examples of such polyamines include single diamines such as ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, and the like; polyalkylenepolyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, di ( (Methylethylene) triamine, dibutylenetriamine, tribubutylenetetramine, pentapentylenehexamine and the like.
[0024]
In addition, bis-type alkenyl succinimide boron compound derivatives, organic phosphonate derivatives and the like, or bis-type alkenyl succinimides are reacted with aldehydes, ketones, carboxylic acids, sulfonic acids, alkylene oxides, bis-types, etc. Alkenyl succinimide derivatives can also be used.
[0025]
The above-mentioned bis-type alkenyl succinimides and derivatives thereof can be used alone or in admixture of two or more. The compounding ratio is 4 to 15% by weight, preferably 5 to 10% by weight. It is.
If the amount of the bis-type alkenyl succinimide or its derivative is too small, the pitting resistance is reduced. If the amount is too large, this effect is saturated and becomes economically disadvantageous.
[0026]
The sulfur-phosphorus extreme pressure agent of component (D), which is an optional component to be blended together with the above components (A) to (C), may contain sulfur and phosphorus in one compound. A so-called sulfur-based extreme pressure agent containing either one and a phosphorus-based extreme pressure agent may be mixed.
[0027]
Examples of the sulfur-based extreme pressure agent include hydrocarbon sulfide, terpene sulfide, and sulfurized oil and fat which are reaction products of oil and fat represented by the general formula (3).
[0028]
Embedded image
General formula (3)
_{R7-S y - (R9-} S y) n -R8
[0029]
In the general formula (3), R7 and R8 are monovalent hydrocarbon groups, which may be the same or different, R9 is a divalent hydrocarbon group, and y is an integer of 1 or more, preferably 1 to 8, each y may be the same or different in the repeating unit, and n is 0 or an integer of 1 or more.
[0030]
Examples of the monovalent hydrocarbon group of R7 and R8 include a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms (for example, an alkyl group and an alkenyl group), and a carbon number of 6 to 26 carbon atoms. Examples of the aromatic hydrocarbon group, specifically, ethyl group, propyl group, butyl group, nonyl group, dodecyl group, propenyl group, butenyl group, benzyl group, phenyl group, tolyl group, hexylphenyl group and the like No.
[0031]
Examples of the divalent hydrocarbon group of R9 also include a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, and an aromatic hydrocarbon group having 6 to 26 carbon atoms. Specific examples include an ethylene group, a propylene group, a butylene group, and a phenylene group.
[0032]
Of (3) the general formula (3) a hydrocarbon sulfide typical expressed in sulfur olefin and formula R7-S y _-R8 (y is an integer of 2 or more) in the polysulfide compounds represented by is there.
Specifically, diisobutyl disulfide, dioctyl polysulfide, ditertiary nonyl polysulfide, ditertiary butyl polysulfide, ditertiary benzyl polysulfide, or sulfurized olefins obtained by sulfurizing olefins such as polyisobutylene and terpenes with a sulfurizing agent such as sulfur. Is mentioned.
[0033]
Sulfurized fats, which are reaction products of fats and oils, use animal and vegetable fats such as lard, beef tallow, whale oil, palm oil, coconut oil, and rapeseed oil as fats and oils. It is not one but various mixtures, and the chemical structure itself is not clear.
[0034]
The phosphorus-based extreme pressure agent or sulfur-phosphorus-based extreme pressure agent (one compound containing sulfur and phosphorus) is represented by a sulfur-phosphorus-based extreme pressure agent (4) in Chemical Formula 4. Phosphoric acid esters, phosphites, thiophosphates, dithiophosphates and the like can be mentioned.
[0035]
Embedded image
General formula (4)
_{(R10) a H 3 -aX 3} PX b
[0036]
In the general formula (4), R10 is a monovalent hydrocarbon group, X is an oxygen atom or a sulfur atom, a is 1, 2 or 3, and b is 0 or 1.
[0037]
As the above R10, a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 5 to 20 carbon atoms (eg, an alkyl group or an alkenyl group), an aromatic hydrocarbon group having 6 to 26 carbon atoms, cycloalkyl Groups.
[0038]
Specific examples of the ester sulfide represented by the general formula (4) of the chemical formula (4) include monooctyl phosphate, dioctyl phosphate, trioctyl phosphate, dioctyl phosphite, trioctyl phosphite, dioctyl thiophosphate, Trioctyl thiophosphate, didecyl phosphate, didecyl phosphite, didodecyl phosphate, tridodecyl phosphate, didodecyl phosphite, tridodecyl phosphite, tridodecyl thiophosphate, trihexadecyl phosphate, trihexadecyl phosphite, thiophosphoric acid Trihexadecyl, trioctadecenyl phosphate, trioctadecenyl phosphite, trioctadecenyl thiophosphate, tri (octylphenyl) phosphate, tri (octylcyclohexyl) phosphate, tridecyl dithiophosphate, etc. No.
[0039]
As the phosphorus-based extreme pressure agent, an alkylamine salt of an acidic phosphate, an acid phosphite, an acid thiophosphate, an acid dithiophosphate represented by the general formula (4), and the like are also used. be able to.
[0040]
Specific examples of these alkylamine salts include, as acidic esters, butyl acid phosphate, 2-ethylhexyl acid phosphate, octyl acid phosphate, lauryl acid phosphate, oleyl acid phosphate, tolyl acid phosphate, and the like.
The alkylamine for neutralizing these is represented by the general formula NR11R12R13 (where R11, R12 and R13 are monovalent hydrocarbon groups or hydrogen atoms, at least one of which is a hydrocarbon group). Specific examples thereof include dibutylamine, octylamine, dioctylamine, laurylamine, dilaurylamine, coconutamine, tallowamine, and the like.
[0041]
The compounding ratio of the sulfur-phosphorus extreme pressure agent as the component (D) is 2 to 10% by weight, preferably 3 to 7% by weight.
If the sulfur-phosphorus extreme pressure agent is too small, when used in a transaxle equipped with a hypoid gear, the extreme pressure property is low, causing gear damage and seizure.If too large, the synchronizing characteristics and oxidation stability are adversely affected. Exert.
[0042]
In addition to the components (A) to (C) or the components (A) to (D), the gear oil composition of the present invention is usually used according to the purpose, according to the purpose. )) Known additives other than the components, for example, ashless dispersants, friction modifiers, antioxidants, corrosion inhibitors, viscosity index improvers, pour point depressants, defoamers and the like can also be blended.
[0043]
Among them, ashless dispersants include alkenyl succinates, amides of long-chain fatty acids and polyamines (aminoamide type), etc., friction modifiers include fatty acids, organic molybdenum compounds, and antioxidants. Amine type, phenol type, etc., as corrosion inhibitors, benzotriazole, alkenyl succinate, etc., as viscosity index improver, polymethacrylate, olefin copolymer, etc., as pour point depressant, polymethacrylate As the antifoaming agent, a silicon compound, an ester type, or the like can be used.
[0044]
The gear oil composition of the present invention described in detail above has excellent pitting resistance, synchro properties, extreme pressure properties and oxidation stability due to the interaction of the components (A) to (C). When the component (C) and the component (D) are blended, transmission trouble and sludge generation due to metal corrosion caused by the component (D) can be suppressed, and excellent extreme pressure properties can be obtained.
[0045]
【Example】
Examples 1 to 6, Comparative Examples 1 to 12
Each component shown in Tables 1 to 6 was blended with a paraffinic base oil (80 neutral) at a ratio shown in the table to prepare a gear oil composition of the present invention. A performance test was performed. The results are shown in Tables 1 to 6.
[0046]
[Pitching resistance test]
As an evaluation of the pitting resistance, a four-cylinder test was performed. The test conditions for the four-cylinder test and the method for determining the fatigue life were as follows.
[0047]
(Test condition)
Rotation speed: 1000 rpm
Sliding rate: 30%
Contact pressure: 65 kg / mm ²
Oil temperature: 80 ° C
[0048]
(Method of judging fatigue life)
The test machine was stopped every 100,000 cycles from the start of operation, and the number of cycles until damage (pitting) observable with the naked eye occurred was defined as the fatigue life. In other words, the greater the number of cycles, the longer the fatigue life and the better the pitting resistance.
In this test, a fatigue life of 700,000 cycles or more was judged to be acceptable.
[0049]
[Synchro property test]
First, a synchronizer ring and a gear cone are set on a table, and the rotation speed of the gear cone is maintained at 1200 rpm by a motor.
Next, the synchronizer ring is pressed with a load of 40 kgf.
Thereafter, the load on the synchronizer ring is removed, and the synchronizer ring is separated from the gear cone.
This pattern consisting of pressing and separating the synchronizer ring is repeated for 10,000 cycles.
[0050]
In the above repetition, the torque generated when the synchronizer ring was pressed was measured, and the friction coefficient was determined.
This friction coefficient was compared between 100 cycles and 10,000 cycles, and evaluated based on the level of the friction coefficient. That is, those having a high friction coefficient and capable of maintaining this high friction coefficient even after 10,000 cycles were regarded as having excellent synchro characteristics.
In this test, those having a coefficient of friction of 0.100 or more after 10,000 cycles were regarded as acceptable.
[0051]
(Extreme pressure test)
A gear test was performed under the following test conditions. The IAE gear test was performed according to IP166 / 68 of the IP (British Petroleum Institute Standard) method, and the seizing limit load was measured.
[0052]
(Test condition)
Small gear rotation speed: 6000 rpm
Lubrication temperature: 110 ° C
Refueling method: Forced refueling Refueling amount: 0.56 liter / min Operating method: Step load increase method every 5 minutes (that is, operation was started at a load of 10 pounds, and the load was increased by 5 pounds every 5 minutes) .)
[0053]
(Oxidation stability test)
The test was carried out under the conditions of 150 ° C. and 96 hours in accordance with the lubricating oil stability test method for internal combustion engines (JIS K2541).
The evaluation was made based on the increase in viscosity, the increase in total acid value, and the presence or absence of sludge.
[0054]
Note that * 1 to * 11 in Tables 1 to 6 have the following meanings.
* 1: Zinc alkyldithiophosphate having a secondary alkyl group * 2: Mg sulfonate with a base number of 398 mg KOH / g * 3: Ca sulfonate with a base number of 300 mg KOH / g * 4: Ca sulfonate with a base number of 29 mg KOH / g * 5: Bis-type alkenyl succinimide having an average molecular weight of polybutenyl group of 2,400 : Extreme pressure agent consisting of sulfurized oil, sulfurized olefin, phosphate amine salt (S = 22.9% by weight, P = 1.4% by weight)
* 9: Other additives * 10: Commercial transmission gear oil containing no sulfur-based extreme pressure agent (GL-3 75W85)
* 11: Commercial transmission gear oil containing sulfur-phosphorus extreme pressure agent (GL-390)
[0055]
[Table 1]

[0056]
[Table 2]

[0057]
[Table 3]

[0058]
[Table 4]

[0059]
[Table 5]

[0060]
[Table 6]

[0061]
From the above results, it can be seen that in Example 6 (Table 2) in which the sulfur-phosphorus extreme pressure agent was blended, excellent extreme pressure properties were exhibited without impairing the synchronizing properties and suppressing the generation of sludge. .
[0062]
【The invention's effect】
As described in detail above, the gear oil composition of the present invention has excellent extreme pressure properties, oxidation stability, and synchro properties, has excellent pitting resistance, and has a long fatigue life.
Therefore, the gear oil composition of the present invention is subjected to a large load with the recent increase in torque, and is suitable for a manual transmission gear for automobiles requiring excellent pitting resistance, synchro properties, extreme pressure properties, and oxidation stability. Further, a composition containing a sulfur-phosphorus extreme pressure agent is suitable as a gear oil for a transaxle equipped with a hypoid gear that requires even higher extreme pressure properties in addition to these characteristics.

Claims (2)

One or more selected from mineral oils and synthetic oils having a viscosity of 2 to 50 cSt at 100 ° C. as a base oil,
(A) 0.5 to 3.0% by weight of zinc alkyldithiophosphate;
(B) 1.2 to 4.0% by weight of an alkaline earth metal type detergent / dispersant having a base number of 200 mgKOH / g or more;
(C) a bis-type alkenyl succinimide having a polybutenyl group having an average molecular weight of 2,000 to 5,000, a derivative thereof of 4 to 15% by weight,
A gear oil composition comprising: One or more selected from mineral oils and synthetic oils having a viscosity of 2 to 50 cSt at 100 ° C. as a base oil,
(A) 0.5 to 3.0% by weight of zinc alkyldithiophosphate;
(B) 1.2 to 4.0% by weight of an alkaline earth metal type detergent / dispersant having a base number of 200 mgKOH / g or more;
(C) a bis-type alkenyl succinimide having a polybutenyl group having an average molecular weight of 2,000 to 5,000, a derivative thereof of 4 to 15% by weight,
(D) 2 to 10% by weight of a sulfur-phosphorus extreme pressure agent,
A gear oil composition comprising: