JP2004339447A - Grease composition and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition suitably employable for a rolling device which hardly causes separation of a base oil and is endowed with excellent lubricating performances, and a rolling device obtained by sealing the same. <P>SOLUTION: The grease composition G comprises a styrene-based block copolymer comprising a block copolymer of styrene with an alkene or an alkadiene, a base oil and a thickening agent, and is constituted so that the total content of the thickening agent and the styrene-based block copolymer is 5-30 mass% of the whole grease composition and that the mass ratio of the thickening agent to the styrene-based block copolymer is 40/60 to 10/90. The grease composition G is sealed in a bearing space enclosed by an inner ring 1 and an outer ring 2 of a rolling bearing 10 and seals 5, 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２５】
なお、化学式（１）中のＲ_１ 〜Ｒ_６ は、それぞれ水素原子、メチル基、及びハロゲン原子から選択される一種であり、Ｒ_１ 〜Ｒ_６ はそれぞれ同一であってもよいし、異なっていてもよい。同様に、ａ，ｂ，ｃは、それぞれ１以上の整数を示す。
さらに、スチレン系ブロック共重合体の具体的な製品名としては、例えば、インフィニアム・ジャパン株式会社製のＳＶ１５０（商品名）などが挙げられる。また、スチレン系ブロック共重合体の製造方法は、特に限定されないが、例えば、米国特許第３７７２１９６号明細書に記載の方法に従って製造することができる。
【００２６】
〔増ちょう剤について〕
増ちょう剤の種類は、特に限定されないが、高温性能を考えると、ウレア化合物を用いることが好ましい。
ウレア化合物は、ジウレア、トリウレア、テトラウレアなどのポリウレア化合物が挙げられるが、特に、一般式が下記化学式（２）で表されるジウレアとすることが好ましい。
Ｒ_１ −ＮＨＣＯＮＨ−Ｒ_２ −ＮＨＣＯＮＨ−Ｒ_３ ・・・・・（２）
【００２７】
なお、化学式（２）中、Ｒ_１ 及びＲ_３ は脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、又は縮合炭化水素基をそれぞれ示し、Ｒ_１ とＲ_３ とは同一であってもよいし、異なっていてもよい。同様に、Ｒ_２ は２価の芳香族炭化水素基を示す。
また、ジウレアは、１モルのイソシアネート化合物と、２モルのアミノ化合物とを反応させることで得ることができる。ここで、上述の反応により得られたジウレアを基油中に添加するようにしてもよいが、グリース組成物の性能を安定させるために、上述の反応を基油中で行うことによって、グリース組成物中にジウレアを含有させるようにしても構わない。
【００２８】
〔基油について〕
基油の種類は、特に限定されないが、合成油、鉱油、又は動植物油から選択される一種又は二種以上を用いることが好ましく、特に、シリコーン油、エステル油、ポリアルキルグリコール油、合成炭化水素油、エーテル油、フッ素油、及び鉱油から選択される一種又は二種以上を用いることが好ましい。
【００２９】
〔グリース組成物の添加剤について〕
グリース組成物には、各種性能のさらなる向上を実現するために、必要に応じて各種添加剤を添加するようにしてもよい。具体的な添加物としては、アミン系、フェノール系、硫黄系、ジチオリン酸亜鉛などの酸化防止剤や、石油スルフォン酸塩、カルシウムスルフォネート、ソルビタンエステルなどの防錆剤や、モリブデン系又はリン系の極圧剤、脂肪酸、動植物油などの油性向上剤、及びベンゾトリアゾールなどの金属不活性化剤などが挙げられ、これらの添加剤は一種又は二種以上を組み合わせて用いることができる。
なお、添加剤の添加量は、本発明の目的を損なわない程度であれば、特に限定されない。
【００３０】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照しながら説明する。
図１は、本発明に係る転動装置の一例である転がり軸受を示す断面図である。なお、本実施形態は、本発明の一例を示すものであり、本発明は本実施形態に限定されるものではない。
本実施形態の転がり軸受は、円筒状のハウジング（図示せず）とこのハウジングに挿嵌された軸（図示せず）とを備え且つ少なくとも一部分がプラスチックで構成された転がり軸受装置に組み込まれており、ハウジングと軸とを相対回転自在に支持しているものである。
【００３１】
転がり軸受１０は、図１に示すように、内輪（内方部材）１と、外輪（外方部材）２と、内輪１の軌道面１ａ及び外輪２の軌道面２ａの間に転動自在に支持される玉（転動体）３と、内輪１及び外輪２の間に転動自在に玉３を保持する保持器４と、外輪２に取り付けられ、内輪１及び外輪２の間に介在されたシール５，５と、を備えている。そして、内輪１、外輪２、及びシール５，５の間に囲まれた軸受空間内には、グリース組成物Ｇが封入されている。
【００３２】
グリース組成物Ｇは、基油と、増ちょう剤と、スチレン系ブロック共重合体と、を含んで構成されている。基油は、合成炭化水素油や鉱油など極性基を有しない油である。また、増ちょう剤は、ウレア化合物である。さらに、スチレン系ブロック共重合体は、スチレンと、アルケン又はアルカジエンとのブロック共重合体である。
【００３３】
ここで、増ちょう剤とスチレン系ブロック共重合体との合計の含有量は、グリース組成物Ｇ全体の５〜３０質量％であるとともに、増ちょう剤とスチレン系ブロック共重合体との質量比は、４０：６０〜１０：９０である。
また、グリース組成物Ｇの混和ちょう度は、１８０〜２９０であり、離油度（ＪＩＳ Ｋ２２２０に規定された方法において試験温度８０℃、試験時間２４時間という条件で測定）は、０．１質量％未満である。
【００３４】
このように、本実施形態における転がり軸受１０によれば、本発明の油分離しにくいグリース組成物Ｇが封入されていることによって、グリース組成物Ｇの基油が転がり軸受１０外部に飛散したり滲み出したりせず、優れた耐摩耗性及び長寿命を実現することが可能となる。よって、油による汚染を嫌う機器に好適に用いることができる。
【００３５】
また、グリース組成物Ｇは、極性基を有しない油を基油として用いているが、この極性基を有しない油はプラスチックに対するケミカルアタックを生じにくいので、少なくとも一部分がプラスチックで構成された転がり軸受装置に転がり軸受１０を組み込んだとしても、プラスチックで構成された部分に基油が接触することによるケミカルアタックが生じることがほとんどない。
なお、本実施形態においては、本発明のグリース組成物を、転がり軸受１０に封入する場合について説明したが、これに限らず、例えば、ボールねじ、リニアガイド、リニアボールベアリングなどの転動装置に適用することも可能である。
【００３６】
【実施例】
次に、本発明の効果を、以下の実施例及び比較例に基づいて検証する。
表１に示すように、基油、増ちょう剤、添加剤を配合し、各種グリース組成物を形成した。なお、表１に示す全てのグリース組成物には、添加剤として酸化防止剤（イルガノックスＬ５７，チバガイギー社製）１質量％、防錆剤（ＮＡＳＵＬ ＢＳＮ ＫＩＮＧ社製）０．９質量％、及び腐食防止剤（イルガメット３９，チバガイギー社製）０．１質量％が、これらの合計の含有量が２質量％となるように添加されている。
【００３７】
【表１】

【００３８】
なお、表１中、ジウレア化合物Ａとは、４，４’−ジフェニルメタンジイソシアネートと、オクチルアミンとを、モル比で１：２の割合で反応させたウレア化合物である。また、ジウレア化合物Ｂとは、４，４’−ジフェニルメタンジイソシアネートとシクロヘキシルアミンとを、モル比で１：２の割合で反応させたウレア化合物である。さらに、ジウレア化合物Ｃとは、４，４’−ジフェニルメタンジイソシアネートとｐ−トルイジンとオクチルアミンとを、モル比で１：１：１の割合で反応させたウレア化合物である。
そして、これらのグリース組成物に対して、混和安定度試験による混和安定度と、ＪＩＳ Ｋ２２２０に示された方法を用いた離油度と、２０時間軸受回転試験によるグリース漏れ量と、軸受寿命試験による焼付き寿命と、について評価を行った。
【００３９】
以下、上記各種性能の評価方法について説明する。
〔混和安定度試験について〕
グリース混和安定度試験装置（ＪＩＳ Ｋ２２２０に記載のもの）を用いて、各グリース組成物の混和安定性（剪断安定性）を評価した。その結果を表１に示す。
なお、評価は、グリース組成物の混和前のちょう度に対する混和後のちょう度の増加量で行った。表１においては、増加量が５０未満である場合は○で示し、同様に、増加量が１００未満である場合は△、増加量が１００以上である場合は×で示す。
【００４０】
〔離油度試験について〕
ＪＩＳ Ｋ２２２０に記載の方法を用いて、試験温度８０℃、試験時間２４時間という条件で、グリース組成物から分離する油分量（質量％）を測定し、結果を表１に示す。
【００４１】
〔軸受回転試験について〕
まず、図２に示すように、上述した転がり軸受１０と同様の構成を有する転がり軸受３０の中に、表１に示すグリース組成物を封入した。そして、転がり軸受３０の軸受空間内部以外に付着した油分を取り除いた後、転がり軸受３０の重量を測定する。次いで、一対の転がり軸受３０を、スピンドルモータ２０を構成するモータ２３の軸２１に取り付け、ケーシング２３で固定した後、下記条件で回転を行った。さらに、回転後、スピンドルモータ２０から転がり軸受３０を取り出し、この転がり軸受３０の軸受空間内部以外に付着した油分を取り除いた後、再度転がり軸受３０の重量を測定した。その後、回転前の転がり軸受３０の重量と、回転後の転がり軸受３０の重量との差からグリース組成物の減少量を算出した。そして、封入したグリース組成物の初期量に対する前記減少量の割合（漏れ率）でグリース組成物の漏れ量を評価した。その結果を表１に示す。なお、表１においては、グリース組成物の漏れ率が０．１％未満である場合は○で示し、同様に漏れ率が０．１％以上１．０％未満である場合には△、漏れ率が１．０％以上である場合には×で示す。
【００４２】
（試験条件）
試験軸受：日本精工株式会社製深溝玉軸受呼び番号６９５ＶＶ（内径５ｍｍ，外径１３ｍｍ，幅４ｍｍ）
回転速度：１８００ｍｉｎ^−１
予圧荷重：１４．７Ｎ
試験時間：２０時間
雰囲気温度：８０℃
【００４３】
〔軸受寿命試験について〕
上述した転がり軸受３０を、図２と同様のスピンドルモータ２０に組み込み、下記試験条件で回転を行った。そして、焼付きが生じるまでの時間（焼付き寿命）を測定した。その結果を表１に示す。
（試験条件）
試験軸受：日本精工株式会社製深溝玉軸受呼び番号６３０３（内径１７ｍｍ，外径４７ｍｍ，幅１４ｍｍ）
回転速度：１３０００ｍｉｎ^−１
予圧荷重：１９６Ｎ
雰囲気温度：１７０℃
なお、評価は、比較例１の焼付き寿命を１とした場合の相対値で示す。
【００４４】
表１に示すように、本発明の範囲内である実施例１乃至５のグリース組成物においては、グリース組成物の漏れ量及び焼付き寿命が良好であった。
一方、増ちょう剤が含まれていない比較例１のグリース組成物においては、グリース漏れ量が多く、焼付き寿命が短くなっていることが分かる。また、スチレン−イソプレン共重合体が含まれていない比較例２及び比較例３のグリース組成物においては、グリース漏れ量が多く、焼付き寿命が非常に短くなっていることが分かる。
【００４５】
次に、実施例１に示すグリース組成物において、増ちょう剤とスチレン−イソプレン共重合体との割合のみを種々変更した場合の混和安定度及び離油度の評価を行った。なお、上述した各種性能は、いずれも上述した評価方法と同様の方法を用いて評価を行った。なお、図３及び図４における縦軸は、離油度に関しては油分量（質量％）で示し、その他の項目に関しては実施例１に示す初期のグリース組成物における値を１としてその相対値で示した。
【００４６】
図３は、スチレン系ブロック共重合体と増ちょう剤との合計の含有量を１００とした場合のスチレン系ブロック共重合体の割合と、混和安定度及び離油度との関係を示す図である。なお、図３のグラフにおける混和安定度及び離油度の数値は、いずれもスチレン系ブロック共重合体を含有せず、ウレア化合物からなる増ちょう剤のみを含有したグリース組成物の混和安定度及び離油度の値をそれぞれ１とした場合の相対値で示す。
【００４７】
図３に示すように、実施例１に示すグリース組成物において、増ちょう剤とスチレン系ブロック共重合体との質量比を、４０：６０〜１０：９０の範囲とすることで、離油度を良好にすることができるとともに、混和安定性を確保できていることが分かる。
続いて、実施例１及び実施例５に示すグリース組成物において、増ちょう剤とスチレン−イソプレン共重合体との割合のみを種々変更した場合のグリース漏れ量及び焼付き寿命の評価を行った。なお、上述した各種性能は、いずれも上述した評価方法と同様の方法を用いて評価を行った。
【００４８】
図４は、スチレン系ブロック共重合体と増ちょう剤との合計の含有量を１００とした場合のスチレン系ブロック共重合体の割合と、グリース漏れ量及び焼付き寿命との関係を示す図である。なお、図４のグラフにおけるグリース漏れ量及び焼付き寿命の数値は、いずれもスチレン系ブロック共重合体を含有せず、ウレア化合物からなる増ちょう剤のみを含有したグリース組成物のグリース組成物の漏れ量及び焼付き寿命の値をそれぞれ１とした場合の相対値で示す。
【００４９】
図４に示すように、実施例１及び実施例５に示すグリース組成物において、増ちょう剤とスチレン系ブロック共重合体との質量比を、４０：６０〜１０：９０の範囲とすることで、グリース漏れ量を少なくすることができるとともに、優れた焼付き寿命を確保できていることが分かる。
【００５０】
【発明の効果】
以上説明したように、本発明に係るグリース組成物によれば、増ちょう剤とスチレン系ブロック共重合体との合計の含有量、及び増ちょう剤とスチレン系ブロック共重合体との質量比を限定したことによって、基油が分離しにくくなるとともに、優れた潤滑性能を備えることができるため、転動装置への適用が可能となる。
【００５１】
また、本発明に係るグリース組成物によれば、混和ちょう度を、１８０〜２９０とすることによって、グリース組成物の転動装置外部への漏出を抑制することが可能となる。
さらに、本発明に係るグリース組成物によれば、ＪＩＳ Ｋ２２２０に規定された方法において試験温度８０℃、試験時間２４時間という条件で測定された離油度を０．１質量％未満とすることによって、グリース組成物の基油の分離をより確実に抑制することが可能となる。
【００５２】
さらに、本発明に係るグリース組成物によれば、増ちょう剤として、ウレア化合物を適用することによって、増ちょう剤による高温性能をさらに向上させることができるため、転動装置のさらなる長寿命化を実現することが可能となる。
本発明に係る転動装置によれば、油分離のしにくいグリース組成物を封入したことによって、グリース組成物の基油が転動装置外部に飛散したり漏れ出したりしにくく、且つ、優れた潤滑性能を備えることができるため、油による汚染を嫌う機器に好適に用いることが可能となる。
【００５３】
特に、転動装置が、少なくとも一部分がプラスチックからなる転がり軸受装置に組み込まれる転がり軸受である場合は、グリース組成物の基油を極性基を有しない油で構成することによって、グリース組成物の基油が転がり軸受外部に飛散したり漏れ出したりしにくく、且つ、優れた潤滑性能を備えるとともに、ケミカルアタックを抑制することが可能となる。
【図面の簡単な説明】
【図１】本発明に係る転動装置の一例である転がり軸受を示す断面図である。
【図２】スピンドルモータを示す断面図である。
【図３】スチレン系ブロック共重合体と増ちょう剤との合計の含有量を１００とした場合のスチレン系ブロック共重合体の割合と、混合安定度及び離油度との関係を示す図である。
【図４】スチレン系ブロック共重合体と増ちょう剤との合計の含有量を１００とした場合のスチレン系ブロック共重合体の割合と、グリース漏れ量及び焼付き寿命との関係を示す図である。
【符号の説明】
１…内輪（内方部材）
２…外輪（外方部材）
３…玉（転動体）
４…保持器
５…シール
１０…転がり軸受
２０…スピンドルモータ
２１…軸
２２…ケーシング
２３…モータ
Ｇ…グリース組成物[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grease composition that is difficult to separate oil, and a rolling device in which the grease composition is sealed. In particular, the present invention relates to a magnetic device such as a hard disk drive (HDD), a flexible disk drive (FDD), or a video tape recorder (VTR) used for a computer or the like. The present invention relates to a grease composition that can be suitably used for a device that does not want to be contaminated by oil, such as a storage device, a printing device such as a laser beam printer (LBP), and a storage device such as a compact disk drive (CDD).
[0002]
[Prior art]
In recent years, with the rapid progress of the above-mentioned devices, even for grease compositions used for rotating parts and sliding parts of these devices, excellent lubrication performance and quality improvement such as wear resistance and long life have been improved. It is becoming required.
In addition, since the base oil may be separated from the grease composition and scattered around, when an electric contact portion, a lens portion, a resin portion, or the like is present near a place where the grease composition is used, In addition, the base oil separated from the grease composition may adhere to these portions, causing problems such as occurrence of defective electrical contacts and contamination of the lens portion and the resin portion. In the worst case, there is a concern that the functions required of the device will be impaired.
[0003]
Therefore, in order to realize a grease composition having excellent lubrication performance and quality and hardly separating a base oil, various grease compositions using a fluorine oil as a base oil have been proposed.
For example, Patent Document 1 proposes a non-diffusion composition in which 0.01% by mass or more of a fluorine-based silane compound is contained in lubricating oil or grease. However, in the non-diffusion composition described in Patent Literature 1, oil components may be separated with time due to differences in compatibility and specific gravity between the oil components and other constituent components, so that long-term use or storage is difficult. There was a problem that it was not suitable.
[0004]
Patent Literature 2 proposes a non-diffusible grease composition that can suppress separation of a base oil by adjusting a combination of a base oil, a thickener, and an additive. According to Patent Literature 2, the difference in compatibility and specific gravity between the oil component and other components can be resolved, and the problem of the non-diffusion composition described in Patent Literature 1 can be solved. Because of the limitation, there is a problem that it is difficult to obtain a grease composition that satisfies the required performance according to the application site.
[0005]
Therefore, as means for suppressing the separation of the base oil without impairing the degree of freedom of the components constituting the grease composition, means for suppressing the separation of the base oil by using an additive has been proposed.
For example, Patent Document 3 proposes a low synergic grease composition to which behenic acid is added as an additive for suppressing base oil separation.
Patent Document 4 proposes a non-oil-separable lubricating composition to which a styrene-based block copolymer is added as an additive that similarly suppresses base oil separation.
[0006]
[Patent Document 1]
JP-A-5-78682
[Patent Document 2]
JP 2000-109874 A
[Patent Document 3]
JP-A-8-193198
[Patent Document 4]
JP-A-2002-327188
[0007]
[Problems to be solved by the invention]
Since the base oils of the grease compositions described in Patent Documents 1 to 3 are hardly separated, the base oil is less likely to be scattered outside in a rolling device in which these grease compositions are sealed. However, in the rolling devices in which the grease compositions described in Patent Documents 1 to 3 described above are sealed, the base oil oozes out to the outside, so that it was difficult to apply the rolling device to the rolling devices.
[0008]
Further, in the non-oil-separating lubricating composition described in Patent Literature 4, although the separation of the base oil can be almost completely prevented, the lubricating composition is applied to a rolling device in view of the mixing consistency and mixing stability of the grease composition. Was difficult.
Further, in recent years, plastic materials have been used for a part of a housing and a shaft constituting a rolling bearing device in order to realize weight reduction and cost reduction of equipment. For this reason, when the grease composition is composed of a base oil having a high aggressiveness (chemical attack) to plastics such as ester-based oil, when the grease composition leaks from the inside of the bearing, the member formed of the plastic material is deteriorated. Therefore, there is a possibility that the life of the bearing is reduced.
[0009]
Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grease composition that is difficult to separate a base oil and that can be suitably used for a rolling device. It is another object of the present invention to provide a rolling device that is less likely to cause the base oil of the grease composition to scatter or seep out, has excellent wear resistance, and has a long life. It is another object of the present invention to provide a rolling device that is less likely to cause chemical attack, has excellent wear resistance, and has a long life, even if the rolling device is at least partially made of plastic.
[0010]
[Means for Solving the Problems]
In order to solve such problems, the grease composition of the present invention has the following constitution.
That is, the grease composition of the present invention is a grease composition containing a base oil and a thickener, wherein the grease composition contains a styrene-based block copolymer which is a block copolymer of styrene and an alkene or alkadiene, and The total content of the thickener and the styrene-based block copolymer is 5 to 30% by mass of the whole composition, and the mass ratio of the thickener and the styrene-based block copolymer is 40: The ratio is 60 to 10:90.
[0011]
In such a grease composition, the base oil is separated by limiting the total content of the thickener and the styrene-based block copolymer and the mass ratio of the thickener and the styrene-based block copolymer. Since it is difficult to perform and has excellent lubrication performance, it can be suitably used for a rolling device.
In addition, the styrene-based block copolymer may be a block copolymer of styrene, alkene, and alkadiene.
[0012]
Further, in the grease composition of the present invention, in the alkene or the alkadiene, at least one of hydrogen atoms constituting a molecule may be substituted with a methyl group or a halogen atom.
Furthermore, in the grease composition of the present invention, it is preferable that the mixing penetration is from 180 to 290.
[0013]
If the penetration ratio specified in JIS K 2220 is less than 180, the hardness of the grease composition is too high, so that the torque performance of the rolling device deteriorates. On the other hand, if the penetration exceeds 290, the hardness of the grease composition is too low, and the grease composition may leak out of the rolling device. Therefore, it is preferable that the mixing consistency of the grease composition is 180 or more and 290 or less.
[0014]
Further, in the grease composition of the present invention, the degree of oil separation measured by a method specified in JIS K2220 at a test temperature of 80 ° C. and a test time of 24 hours is preferably less than 0.1% by mass.
Such a grease composition can more reliably suppress the separation of the base oil from the grease composition.
[0015]
Furthermore, in the grease composition of the present invention, the thickener is preferably a urea compound.
Such a grease composition can further improve the high-temperature performance of the thickener, and can further extend the life of the rolling device.
Further, in order to solve the above-mentioned problem, the rolling device of the present invention has the following configuration.
[0016]
That is, the rolling device of the present invention is an inner member having a raceway surface on the outer surface, and an outer member having a raceway surface with respect to the raceway surface of the inner member and disposed outside the inner member, A plurality of rolling elements disposed so as to be freely rotatable between the two raceway surfaces, wherein the rolling elements formed between the inner member and the outer member are disposed. The grease composition of the present invention is sealed in the void.
[0017]
Since such a rolling device is provided with a grease composition that does not easily separate oil, the base oil is unlikely to scatter or seep out of the rolling device, and has excellent wear resistance and life. Therefore, the present invention can be applied to equipment that does not like oil contamination.
In addition, the rolling device of the present invention includes a housing and a shaft inserted into the housing, and is incorporated in a rolling bearing device at least partially formed of plastic, so that the housing and the shaft can be relatively rotated. In the case of a supporting rolling bearing, the base oil contained in the grease composition is preferably an oil having no polar group.
[0018]
Since such a rolling device is provided with a grease composition that is difficult to separate oil, the base oil is unlikely to scatter or ooze out of the rolling bearing, and has excellent wear resistance and life, Chemical attack is less likely to occur on parts made of plastic.
The rolling device according to the present invention includes: an inner member having a raceway surface on an outer surface; and an outer member disposed outside the inner member having a raceway surface with respect to the raceway surface of the inner member. It is not particularly limited as long as it comprises a plurality of rolling elements disposed rotatably between the raceway surfaces, for example, rolling bearings, ball screws, linear guides, and linear ball bearings No.
[0019]
Here, when the rolling device is a rolling bearing, the inner member refers to the inner ring, the outer member refers to the outer ring, the rolling element refers to balls and rollers, and when the rolling device is a ball screw, the inner member refers to a screw. The shaft and outer member indicate a nut, and the rolling element indicates a ball. Further, when the rolling device is a linear guide, the inner member indicates a guide rail, the outer member indicates a slider, and the rolling element indicates a ball.
[0020]
Hereinafter, the critical significance of the numerical limitation and the material for forming the grease composition in the present invention will be described.
[About the total content of the thickener and the styrenic block copolymer]
When the total content of the thickener and the styrene-based block copolymer is less than 5% by mass of the entire grease composition, not only the grease formation becomes difficult, but also the improvement of the high temperature performance by the thickener is expected. I can no longer do it. Further, when the total content of the thickener and the styrene-based block copolymer exceeds 30% by mass of the entire grease composition, the amount of the base oil becomes relatively small. turn into. Therefore, the total content of the thickener and the styrene-based block copolymer is preferably 5 to 30% by mass of the entire grease composition.
[0021]
[About mass ratio of thickener and styrene block copolymer]
In the mass ratio of the thickener and the styrene block copolymer, if the ratio of the styrene block copolymer is less than 60%, the miscibility becomes poor, and the degree of oil separation increases. The amount of leakage will increase. On the other hand, when the ratio of the styrene-based block copolymer is more than 90%, the styrene-based block copolymer becomes relatively large and dispersibility deteriorates, so that the mixing stability deteriorates. Therefore, the mass ratio between the thickener and the styrene-based block copolymer is preferably 40:60 to 10:90.
[0022]
[About Alken]
The type of alkene that is a monomer of the styrene-based block copolymer is not particularly limited, but is preferably butene, propene, chloroethene, or dichloroethene.
[About Alkadiene]
The type of alkadiene which is a monomer of the styrene-based block copolymer is not particularly limited, but is preferably butadiene or isoprene, and particularly preferably isoprene.
[0023]
(Styrene block copolymerization)
The weight average molecular weight (hereinafter, referred to as average molecular weight) of the styrene-based block copolymer is not particularly limited, but may be 1.0 × 10 4⁴  ~ 3.0 × 10⁵  It is preferable to set the degree. The average molecular weight of the styrenic block copolymer is 1.0 × 10⁴  If it is less than 3, a good gel-like substance cannot be obtained even if the content of the styrene-based block copolymer with respect to the grease composition is increased. On the other hand, 3.0 × 10⁵  If the temperature exceeds the above, the melting point of the block copolymer increases, so that the heating temperature for dissolving the styrenic block copolymer in the base oil must be increased, and the base oil may be deteriorated. 3.0 × 10⁵  If it exceeds 3, the styrene-based block copolymer is difficult to disperse uniformly, and it becomes difficult to obtain a good gel-like material. Further, as a specific example of the styrene-based block copolymer, a styrene-butadiene copolymer using butadiene as an example of an alkadiene can be given as represented by the following chemical formula (1).
[0024]
Embedded image

[0025]
In addition, R in the chemical formula (1)₁~ R₆  Is a member selected from a hydrogen atom, a methyl group, and a halogen atom;₁  ~ R₆  May be the same or different. Similarly, a, b, and c each represent an integer of 1 or more.
Further, as a specific product name of the styrene-based block copolymer, for example, SV150 (trade name) manufactured by Infinium Japan Co., Ltd. may be mentioned. Further, the method for producing the styrene-based block copolymer is not particularly limited. For example, it can be produced according to the method described in US Pat. No. 3,772,196.
[0026]
[About thickener]
The type of the thickener is not particularly limited, but it is preferable to use a urea compound in consideration of high-temperature performance.
Examples of the urea compound include polyurea compounds such as diurea, triurea, and tetraurea. Particularly, it is preferable to use diurea represented by the following chemical formula (2).
R₁  -NHCONH-R₂  -NHCONH-R₃      ・ ・ ・ ・ ・ (2)
[0027]
Note that in the chemical formula (2), R₁  And R₃  Represents an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a condensed hydrocarbon group;₁  And R₃  May be the same or different. Similarly, R₂Represents a divalent aromatic hydrocarbon group.
Diurea can be obtained by reacting 1 mol of an isocyanate compound with 2 mol of an amino compound. Here, the diurea obtained by the above-described reaction may be added to the base oil.However, in order to stabilize the performance of the grease composition, the grease composition Diurea may be contained in the product.
[0028]
[About base oil]
The type of base oil is not particularly limited, but it is preferable to use one or more selected from synthetic oils, mineral oils, and animal and vegetable oils, particularly silicone oils, ester oils, polyalkyl glycol oils, and synthetic hydrocarbons. It is preferable to use one or more selected from oil, ether oil, fluorine oil, and mineral oil.
[0029]
(About additives of grease composition)
Various additives may be added to the grease composition as needed in order to further improve various performances. Specific additives include antioxidants such as amine-based, phenol-based, sulfur-based, and zinc dithiophosphates; rust preventives such as petroleum sulfonates, calcium sulfonates, and sorbitan esters; and molybdenum-based or phosphorus-based agents. An extreme pressure agent, a fatty acid, an oiliness improver such as an animal or vegetable oil, a metal deactivator such as benzotriazole, and the like can be used. These additives can be used alone or in combination of two or more.
The amount of the additive is not particularly limited as long as the object of the present invention is not impaired.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing a rolling bearing which is an example of the rolling device according to the present invention. Note that the present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment.
The rolling bearing according to the present embodiment includes a cylindrical housing (not shown) and a shaft (not shown) inserted into the housing, and is incorporated in a rolling bearing device at least partially formed of plastic. That is, the housing and the shaft are supported so as to be relatively rotatable.
[0031]
As shown in FIG. 1, the rolling bearing 10 is rotatable between an inner ring (inner member) 1, an outer ring (outer member) 2, and a raceway surface 1 a of the inner ring 1 and a raceway surface 2 a of the outer ring 2. A ball (rolling element) 3 to be supported, a retainer 4 that holds the ball 3 so as to roll freely between the inner ring 1 and the outer ring 2, and is attached to the outer ring 2 and is interposed between the inner ring 1 and the outer ring 2. And seals 5 and 5. A grease composition G is sealed in a bearing space surrounded by the inner ring 1, the outer ring 2, and the seals 5, 5.
[0032]
The grease composition G includes a base oil, a thickener, and a styrene-based block copolymer. The base oil is an oil having no polar group, such as a synthetic hydrocarbon oil or a mineral oil. The thickener is a urea compound. Further, the styrene-based block copolymer is a block copolymer of styrene and an alkene or alkadiene.
[0033]
Here, the total content of the thickener and the styrene-based block copolymer is 5 to 30% by mass of the entire grease composition G, and the mass ratio of the thickener and the styrene-based block copolymer. Is 40:60 to 10:90.
The penetration of the grease composition G is 180 to 290, and the degree of oil separation (measured at a test temperature of 80 ° C. and a test time of 24 hours according to the method specified in JIS K2220) is 0.1 mass. %.
[0034]
As described above, according to the rolling bearing 10 of the present embodiment, the grease composition G of the present invention, which is difficult to separate oil, is sealed, so that the base oil of the grease composition G may scatter outside the rolling bearing 10. It is possible to realize excellent abrasion resistance and long life without exuding. Therefore, it can be suitably used for equipment that does not like contamination by oil.
[0035]
Further, the grease composition G uses an oil having no polar group as a base oil. However, since the oil having no polar group does not easily cause a chemical attack on plastics, a rolling bearing at least partially constituted of plastics is used. Even if the rolling bearing 10 is incorporated in the device, a chemical attack due to the contact of the base oil with the portion made of plastic hardly occurs.
In the present embodiment, the case where the grease composition of the present invention is sealed in the rolling bearing 10 has been described. However, the present invention is not limited to this. For example, a ball screw, a linear guide, a rolling device such as a linear ball bearing may be used. It is also possible to apply.
[0036]
【Example】
Next, the effects of the present invention will be verified based on the following examples and comparative examples.
As shown in Table 1, various grease compositions were formed by blending a base oil, a thickener, and additives. In addition, in all the grease compositions shown in Table 1, 1% by mass of an antioxidant (Irganox L57, manufactured by Ciba Geigy), 0.9% by mass of a rust preventive (manufactured by NASUL BSN KING), and 0.1% by mass of a corrosion inhibitor (Irgammet 39, manufactured by Ciba-Geigy) is added so that the total content thereof is 2% by mass.
[0037]
[Table 1]

[0038]
In Table 1, the diurea compound A is a urea compound obtained by reacting 4,4'-diphenylmethane diisocyanate with octylamine at a molar ratio of 1: 2. The diurea compound B is a urea compound obtained by reacting 4,4'-diphenylmethane diisocyanate with cyclohexylamine at a molar ratio of 1: 2. Further, the diurea compound C is a urea compound obtained by reacting 4,4'-diphenylmethane diisocyanate, p-toluidine, and octylamine at a molar ratio of 1: 1: 1.
Then, for these grease compositions, the mixing stability by the mixing stability test, the degree of oil separation using the method shown in JIS K2220, the grease leakage amount by the 20-hour bearing rotation test, and the bearing life test Was evaluated with respect to the seizure life.
[0039]
Hereinafter, methods for evaluating the various performances will be described.
[About the stability test]
Using a grease mixing stability tester (described in JIS K2220), the mixing stability (shear stability) of each grease composition was evaluated. Table 1 shows the results.
The evaluation was made based on the increase in the consistency after mixing with the consistency before mixing the grease composition. In Table 1, when the amount of increase is less than 50, it is indicated by ○, similarly, when the amount of increase is less than 100, it is indicated by Δ, and when the amount of increase is 100 or more, it is indicated by ×.
[0040]
[About oil release test]
Using the method described in JIS K2220, the amount of oil (% by mass) separated from the grease composition was measured under the conditions of a test temperature of 80 ° C. and a test time of 24 hours, and the results are shown in Table 1.
[0041]
[About bearing rotation test]
First, as shown in FIG. 2, a grease composition shown in Table 1 was sealed in a rolling bearing 30 having the same configuration as the above-described rolling bearing 10. Then, after removing the oil attached to portions other than the inside of the bearing space of the rolling bearing 30, the weight of the rolling bearing 30 is measured. Next, the pair of rolling bearings 30 was attached to the shaft 21 of the motor 23 constituting the spindle motor 20, and was fixed by the casing 23, and then rotated under the following conditions. Further, after the rotation, the rolling bearing 30 was taken out of the spindle motor 20, and the oil attached to the rolling bearing 30 other than inside the bearing space was removed. Then, the weight of the rolling bearing 30 was measured again. Thereafter, the amount of reduction in the grease composition was calculated from the difference between the weight of the rolling bearing 30 before rotation and the weight of the rolling bearing 30 after rotation. Then, the leakage amount of the grease composition was evaluated based on the ratio (leakage rate) of the decrease amount to the initial amount of the sealed grease composition. Table 1 shows the results. In Table 1, when the leakage rate of the grease composition is less than 0.1%, it is indicated by ○, and similarly, when the leakage rate is 0.1% or more and less than 1.0%, Δ, the leakage When the rate is 1.0% or more, it is indicated by x.
[0042]
(Test condition)
Test bearing: Nippon Seiko Co., Ltd. deep groove ball bearing nominal number 695VV (inner diameter 5mm, outer diameter 13mm, width 4mm)
Rotation speed: 1800min^-1
Preload: 14.7N
Test time: 20 hours
Ambient temperature: 80 ° C
[0043]
[About bearing life test]
The above-described rolling bearing 30 was incorporated in the same spindle motor 20 as in FIG. 2 and rotated under the following test conditions. Then, the time until seizure occurred (seizure life) was measured. Table 1 shows the results.
(Test condition)
Test bearing: Nippon Seiko Co., Ltd. deep groove ball bearing number 6303 (inner diameter 17 mm, outer diameter 47 mm, width 14 mm)
Rotation speed: 13000min^-1
Preload: 196N
Ambient temperature: 170 ° C
The evaluation is shown as a relative value when the seizure life of Comparative Example 1 is 1.
[0044]
As shown in Table 1, in the grease compositions of Examples 1 to 5, which are within the scope of the present invention, the leakage amount of the grease composition and the seizure life were good.
On the other hand, in the grease composition of Comparative Example 1 containing no thickener, it can be seen that the amount of grease leakage was large and the seizure life was short. In addition, it can be seen that the grease compositions of Comparative Examples 2 and 3 containing no styrene-isoprene copolymer have a large amount of grease leakage and a very short seizure life.
[0045]
Next, in the grease composition shown in Example 1, the mixing stability and the oil separation were evaluated when only the ratio of the thickener and the styrene-isoprene copolymer was variously changed. The above-described various performances were evaluated using the same methods as the above-described evaluation methods. The vertical axis in FIGS. 3 and 4 indicates the degree of oil separation in terms of the amount of oil (% by mass), and the other items are expressed in relative values with the initial grease composition shown in Example 1 as 1. Indicated.
[0046]
FIG. 3 is a graph showing the relationship between the ratio of the styrene block copolymer and the mixing stability and the degree of oil separation when the total content of the styrene block copolymer and the thickener is 100. is there. In addition, the numerical values of the mixing stability and the oil separation degree in the graph of FIG. 3 do not contain any styrene-based block copolymer, and the mixing stability and grease composition of the grease composition containing only the thickener composed of the urea compound. It is shown as a relative value when the value of the degree of oil separation is set to 1.
[0047]
As shown in FIG. 3, in the grease composition shown in Example 1, by setting the mass ratio of the thickener and the styrene-based block copolymer in the range of 40:60 to 10:90, the degree of oil separation is improved. It can be seen that the mixing stability can be improved and the mixing stability can be ensured.
Subsequently, in the grease compositions shown in Example 1 and Example 5, the grease leakage amount and the seizure life were evaluated when only the ratio of the thickener and the styrene-isoprene copolymer was variously changed. The above-described various performances were evaluated using the same methods as the above-described evaluation methods.
[0048]
FIG. 4 is a graph showing the relationship between the ratio of the styrene block copolymer and the grease leakage amount and the seizure life when the total content of the styrene block copolymer and the thickener is 100. is there. In addition, the numerical values of the grease leakage amount and the seizure life in the graph of FIG. 4 are the same as those of the grease composition of the grease composition containing neither the styrene-based block copolymer but only the thickener composed of the urea compound. The values are shown as relative values when the value of the leakage amount and the value of the seizure life are each set to 1.
[0049]
As shown in FIG. 4, in the grease compositions shown in Examples 1 and 5, the mass ratio between the thickener and the styrene-based block copolymer is set in the range of 40:60 to 10:90. It can be seen that the grease leakage amount can be reduced and an excellent seizure life can be ensured.
[0050]
【The invention's effect】
As described above, according to the grease composition of the present invention, the total content of the thickener and the styrene-based block copolymer, and the mass ratio of the thickener and the styrene-based block copolymer The limitation makes it difficult for the base oil to be separated and provides excellent lubrication performance, so that application to a rolling device becomes possible.
[0051]
Further, according to the grease composition of the present invention, by setting the mixing consistency to 180 to 290, it is possible to suppress the leakage of the grease composition to the outside of the rolling device.
Further, according to the grease composition according to the present invention, the degree of oil separation measured under the conditions of a test temperature of 80 ° C. and a test time of 24 hours in the method specified in JIS K2220 is less than 0.1% by mass. Further, it is possible to more reliably suppress the separation of the base oil of the grease composition.
[0052]
Further, according to the grease composition according to the present invention, by applying a urea compound as a thickener, it is possible to further improve the high-temperature performance of the thickener, further extending the life of the rolling device. It can be realized.
According to the rolling device according to the present invention, by enclosing the grease composition that is difficult to oil-separate, the base oil of the grease composition is unlikely to scatter or leak outside the rolling device, and is excellent. Since lubrication performance can be provided, it can be suitably used for equipment that does not want to be contaminated by oil.
[0053]
In particular, when the rolling device is a rolling bearing incorporated in a rolling bearing device at least partially made of plastic, the base oil of the grease composition is constituted by an oil having no polar group, whereby the base of the grease composition is reduced. The oil is unlikely to be scattered or leaked out of the rolling bearing, has excellent lubrication performance, and can suppress chemical attack.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a rolling bearing as an example of a rolling device according to the present invention.
FIG. 2 is a sectional view showing a spindle motor.
FIG. 3 is a graph showing the relationship between the ratio of the styrene block copolymer and the mixing stability and the degree of oil separation when the total content of the styrene block copolymer and the thickener is 100. is there.
FIG. 4 is a graph showing the relationship between the ratio of the styrene block copolymer and the amount of grease leakage and seizure life when the total content of the styrene block copolymer and the thickener is 100. is there.
[Explanation of symbols]
1 ... Inner ring (inner member)
2 ... Outer ring (outer member)
3. Ball (rolling element)
4 ... Cage
5… Seal
10. Rolling bearing
20 ... Spindle motor
21 ... axis
22 ... casing
23 ... Motor
G: Grease composition

Claims (7)

In a grease composition containing a base oil and a thickener,
Along with styrene and a styrene-based block copolymer that is a block copolymer of an alkene or an alkadiene,
The total content of the thickener and the styrenic block copolymer is 5 to 30% by mass of the whole composition,
A grease composition characterized in that the mass ratio of the thickener to the styrene block copolymer is from 40:60 to 10:90. The grease composition according to claim 1, wherein at least one of hydrogen atoms constituting the alkene or the alkadiene is substituted with a methyl group or a halogen atom. The grease composition according to claim 1, wherein the compatibility is 180 to 290. The oil separation measured by a method defined in JIS K2220 at a test temperature of 80 ° C. and a test time of 24 hours is less than 0.1% by mass, according to any one of claims 1 to 3, characterized in that: The grease composition according to item. The grease composition according to any one of claims 1 to 4, wherein the thickener is a urea compound. An inner member having a raceway surface on an outer surface, an outer member having a raceway surface with respect to the raceway surface of the inner member, and an outer member disposed outside the inner member; And a plurality of rolling elements provided,
The grease composition according to any one of claims 1 to 5, wherein a gap formed between the inner member and the outer member and in which the rolling element is disposed is sealed. And rolling device. A rolling bearing that includes a housing and a shaft inserted into the housing, and is incorporated in a rolling bearing device at least partially formed of plastic, and that supports the housing and the shaft so as to be relatively rotatable,
The rolling device according to claim 6, wherein the base oil contained in the grease composition is an oil having no polar group.

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