JP3791439B2 - Biodegradable resin composition and machine part - Google Patents

Description

【００１５】
ここで、ｎ及びｍの数値は特に限定されるものではないが、ｎは２，３，又は４が好ましく、ｍは２〜２５０の整数、特に２〜１００の整数が好ましい。
なお、前記ポリエステル樹脂は、全体の５モル％以下であれば、その分子構造中にウレタン結合を有していてもよい。ウレタン結合を導入する方法としては、芳香族ポリエステル成分の構成モノマーである芳香族二塩基酸（ジカルボン酸）の一部を、ヘキサメチレンジイソシアネート等のジイソシアネート化合物に置き換えて、重縮合を行う方法等があげられる。
【００１６】
また、本発明に係る請求項３の生分解性樹脂組成物は、請求項１又は請求項２に記載の生分解性樹脂組成物において、補強材を含有することを特徴とする。
さらに、本発明に係る請求項４の生分解性樹脂組成物は、請求項３に記載の生分解性樹脂組成物において、前記ポリエステル樹脂の含有量を樹脂組成物全体の３０質量％以上９０質量％以下とし、前記補強材の含有量を樹脂組成物全体の１０質量％以上５０質量％未満としたことを特徴とする。
【００１７】
本発明の生分解性樹脂組成物には、その機械的性質を向上させるために補強材を含有させることができる。補強材の種類は特に限定されるものではないが、生分解性プラスチック研究会（ＢＰＳ）が運用しているグリーンプラ識別表示制度のポジティブリストに掲載されているものが好ましい。例えば、ガラス繊維，炭素繊維，チタン酸カリウムウィスカー，軽質炭酸カルシウム（結晶形はカルサイトやアルゴナイト），天然含水ケイ酸アルミニウム（カオリン、クレー），タルク，ベントナイト，繊維状水酸化マグネシウム，ウォラストナイト，セピオライト，カーボンブラック，マイカ，二酸化ケイ素，珪藻土等があげられる。これらの補強材の中では、その高い補強効果から、ガラス繊維が特に好ましい。
【００１８】
補強材の含有量は、樹脂組成物全体の１０質量％以上５０質量％未満とすることが好ましい。１０質量％未満であると機械的性質が低くなり、転がり軸受用保持器，シール等のような機械部品を構成する材料として必要な機械的性質が得られない。例えば、シールの場合であれば、シールとして最低限必要な強度と耐クリープ性が確保できない。
また、５０質量％以上であると、溶融成形時の樹脂組成物の流動性を十分に確保することが困難となる。樹脂組成物が十分な流動性を有していれば、樹脂組成物の成形を射出成形法により行うことが可能となるので、生産性，経済性の面からも好ましい。さらに、ＢＰＳのグリーンプラ識別表示制度において、生分解性樹脂組成物中の無機材料の含有量は５０質量％未満と規定されていることからも、補強材の含有量は樹脂組成物全体の５０質量％未満とすることが好ましい。
【００１９】
なお、補強材の含有量は、樹脂組成物全体の１０質量％以上４０質量％以下とすることがより好ましい。そうすれば、転がり軸受用保持器，シール等のような機械部品を本発明の生分解性樹脂組成物で構成した場合に、機械部品の性能，成形性，生産性，生分解性等のバランスがより良好となる。
また、前記ポリエステル樹脂の含有量は、樹脂組成物全体の３０質量％以上９０質量％以下とすることが好ましい。３０質量％未満であると、生分解性樹脂組成物の耐熱性が不十分となる。なお、前記ポリエステル樹脂の含有量を４０質量％以上とすれば、十分な耐熱性を長期にわたって維持することができるので、より好ましい。一方、前記ポリエステル樹脂の含有量を高くしても特に不都合はないので、樹脂組成物における補強材以外の成分をすべて前記ポリエステル樹脂としても差し支えない。よって、前記ポリエステル樹脂の含有量の上限値は９０質量％となる。
【００２４】
さらに、本発明の生分解性樹脂組成物には、生分解性を有するポリヒドロキシカルボン酸を含有させてもよい。ポリヒドロキシカルボン酸を含有させると、射出成形法によって成形する場合に金型からの離型性が向上する。例えば、転がり軸受用保持器やシールを射出成形法によって製造する場合、保持器やシールの形状によっては、樹脂の冷却に時間を要して生産性が低下する場合がある。しかしながら、生分解性樹脂組成物にポリヒドロキシカルボン酸を含有させると、ポリヒドロキシカルボン酸の特徴の一つである高い結晶性により、樹脂の冷却に要する時間を短縮することができるので、生産性が向上する。
【００２５】
ポリヒドロキシカルボン酸の含有量は、樹脂組成物全体の４０質量％以下であることが好ましい。４０質量％を超えると、生分解性樹脂組成物の耐熱性が不十分となる。ポリヒドロキシカルボン酸の含有量を３０質量％以下とすれば、十分な耐熱性を長期にわたって維持することができるので、より好ましい。ただし、十分な耐熱性及び機械的性質を長期にわたって維持するためには、引張破断伸びが５０％以上である生分解性ポリエステル樹脂と生分解性を有するポリヒドロキシカルボン酸との両方の合計の含有量は、本発明の生分解性樹脂組成物の主構成要素である前記ポリエステル樹脂と同量以下とすることが好ましい。なお、金型からの離型性に問題がない場合は、ポリヒドロキシカルボン酸を含有させなくても差し支えない。
【００２６】
ポリヒドロキシカルボン酸の種類は特に限定されるものではないが、例えばポリ乳酸（ＰＬＡ）は、一般的なポリヒドロキシカルボン酸の中でも高融点で結晶性が高く、また、コスト的にも優れているので好適である。
【００２７】
さらに、本発明の生分解性樹脂組成物には、その耐熱性，生分解性，機械的性質等に悪影響を及ぼさない範囲で、且つ前記生分解性樹脂組成物が分解されて自然環境に放出された際に自然環境に悪影響を与えない範囲であれば、所望により種々の添加剤を配合してもよい。
例えば、潤滑油，固体潤滑剤，熱安定剤，酸化防止剤，熱伝導性改良剤，結晶化促進剤，増核剤，顔料，染料等があげられるが、いずれの添加剤もグリーンプラ識別表示制度にしたがって添加されることが好ましい。
【００２８】
また、本発明に係る請求項５の機械部品は、請求項１〜４のいずれかに記載の生分解性樹脂組成物で構成したことを特徴とする。
さらに、本発明に係る請求項６の転がり軸受は、内輪と、外輪と、前記両輪の間に転動自在に配設された複数の転動体と、前記両輪の間に前記転動体を保持する保持器と、を備える転がり軸受において、前記内輪，前記外輪，前記転動体，及び前記保持器のうち少なくとも前記保持器を、請求項１〜４のいずれかに記載の生分解性樹脂組成物で構成したことを特徴とする。
【００２９】
さらに、本発明に係る請求項７の転がり軸受は、請求項６に記載の転がり軸受において、請求項１〜４のいずれかに記載の生分解性樹脂組成物で構成されたシールを備えることを特徴とする。
さらに、本発明に係る請求項８の直動案内軸受装置は、軸方向に延びる転動体転動溝を外面に有する案内レールと、該案内レールの転動体転動溝に対向する転動体転動溝を有するとともに前記軸方向に相対移動可能に前記案内レールに取り付けられたスライダと、前記両転動体転動溝の間に転動自在に介装された複数の転動体と、前記両転動体転動溝の間に前記転動体を保持する保持器と、を備える直動案内軸受装置において、前記スライダの少なくとも一部分と前記保持器とのうち一方又は両方を、請求項１〜４のいずれかに記載の生分解性樹脂組成物で構成したことを特徴とする。
【００３０】
さらに、本発明に係る請求項９の直動案内軸受装置用スライダの仮軸は、直動案内軸受装置の案内レールに滑動自在に嵌合されるスライダを仮に組み付ける仮軸において、請求項１〜４のいずれかに記載の生分解性樹脂組成物で構成したことを特徴とする。
本発明に係る生分解性樹脂組成物は、生分解しやすい脂肪族成分を有するポリエステル樹脂を含有しているので、土壌中等の自然環境に放出されると自然に分解される。よって、本発明に係る転がり軸受，直動案内軸受装置，直動案内軸受装置用スライダの仮軸等の機械部品は、自然環境に放出されると前記生分解性樹脂組成物で構成された部分が自然に分解されるので、自然環境に対して悪影響を及ぼしにくい。また、土壌中等の自然環境に廃棄処分することも可能であり、使用後の廃棄が容易となる。
【００３１】
なお、本発明における生分解性樹脂とは、ＩＳＯ １４８５１，１４８５２，１４８５５のうち少なくとも１つの条件に該当する樹脂を意味するものである。ＩＳＯ １４８５１の条件とは、「ＪＩＳ Ｋ６９５０に規定された好気的水系での生分解性試験における酸素消費量から求められた生分解度が６０％以上となるもの」である。また、ＩＳＯ １４８５２の条件とは、「ＪＩＳ Ｋ６９５１に規定された好気的水系での生分解性試験における二酸化炭素発生量から求められた生分解度が６０％以上となるもの」である。さらに、ＩＳＯ １４８５５の条件とは、「ＪＩＳ Ｋ６９５３に規定された好気的コンポスト過程での生分解性試験における二酸化炭素発生量から求められた生分解度が７０％以上となるもの」である。
【００３２】
【発明の実施の形態】
〔生分解性樹脂を含有する樹脂組成物の参考例〕
以下に示すような生分解性樹脂組成物（参考例１〜４及び比較例１〜３）を射出成形して、図２のような冠形保持器の形状に成形した。そして、この保持器を用いて、生分解性樹脂組成物の生分解性及び耐熱性を評価する試験を行った。
まず、使用した生分解性樹脂組成物について説明する。
【００３３】
参考例１の生分解性樹脂組成物は、ポリエチレンテレフタレートサクシネートである。これは、ポリエチレンテレフタレート（芳香族ポリエステル成分）とポリエチレンサクシネート（脂肪族ポリエステル成分）との共重合体であり、共重合比（モル比）はポリエチレンテレフタレート：ポリエチレンサクシネート＝６：４である。
参考例２及び参考例３もポリエチレンテレフタレートサクシネートであるが、共重合比（モル比）は、参考例２が７：３であり、参考例３が８：２である。
【００３４】
また、参考例４は、ポリエチレンテレフタレートとポリ（ポリオキシエチレン）サクシネート（脂肪族ポリエステル成分及び脂肪族ポリエーテル成分）との共重合体である。共重合比（モル比）は、ポリエチレンテレフタレート：ポリ（ポリオキシエチレン）サクシネート＝７：３である。
さらに、比較例１の生分解性樹脂組成物はポリ乳酸（島津製作所株式会社製のＬＡＣＴＹ９０３０）、比較例２はポリ−３−ヒドロキシ酪酸（三菱ガス化学株式会社製のビオグリーン）、比較例３はポリブチレンサクシネート（昭和高分子株式会社製のビオノーレ＃１０２０）である。
【００３５】
次に、生分解性試験の方法について説明する。
株式会社田窪工業所製のバイオ式生ごみ分解処理機である「地球の友だち」（商品名）中に、前記保持器を同社製の培養材及び「地球の友だち菌」（商品名）とともに投入し、５５〜６０℃で生分解させた。そして、初期の２０％以下の重量になった時間、あるいは初期形状を維持できずにバラバラになった時間を、生分解完了時間とし、その時間の長さによって生分解性を評価した。
【００３６】
試験結果を表１に示す。なお、表１における生分解完了時間の数値は、比較例１の生分解完了時間を１とした場合の相対値で示してある。
【００３７】
【表１】

【００３８】
表１の結果から、殆ど生分解性を有していない芳香族ポリエステル（ポリエチレンテレフタレート）の分子構造中に、優れた生分解性を有する脂肪族ポリエステル（ポリエチレンサクシネート）を導入することによって、参考例１〜４の樹脂組成物は優れた生分解性を有していることが分かる。また、参考例１〜３の比較から、脂肪族ポリエステルの割合が増加するにしたがって、生分解性が向上することが分かる。
【００３９】
さらに、参考例２と参考例４との比較から、脂肪族ポリエステル成分のみを芳香族ポリエステルに導入するよりも、脂肪族ポリエステル成分と脂肪族ポリエーテル成分の両方を芳香族ポリエステルに導入する方が、生分解性が優れていることが分かる。
次に、耐熱性試験の方法について説明する。
上記と同様の保持器を所定の温度（６０，７０，８０，９０，１００，１１０，１２０，１３０℃）の恒温槽中に１０００時間吊り下げた後に、引張破断強度（円環強度）を測定した。そして、初期の引張強度からの強度低下が２０％以下である温度のうち最高温度を、その生分解性樹脂組成物の耐熱温度とした。
【００４０】
試験結果を表１に併せて示す。表１から、参考例１〜４の生分解性樹脂組成物は、比較例１〜３と比べて耐熱温度が高いことが分かる。
〔補強材を含有する生分解性樹脂組成物の実施例〕
次に、補強材を含有する生分解性樹脂組成物について、各種性能を評価する試験を行った。
まず、表２〜５に示すような補強材を含有する生分解性樹脂組成物（参考例１１〜１９、実施例１〜６、及び比較例１１〜１７）を製造した。これらの生分解性樹脂組成物の原料として使用した樹脂及び補強材について説明する。
【００４１】
脂肪族成分と芳香族ポリエステル成分とを分子構造中に有するポリエステル樹脂としては、ポリエチレンテレフタレート部分改質品（デュポン株式会社製のＢｉｏｍａｘ ＷＵＨ、以降はＰＥＴ改質品と記す）を使用した。また、引張破断伸びが５０％以上である生分解性ポリエステル樹脂としては、ポリブチレンアジペート・テレフタレート（ＢＡＳＦ株式会社製のＥｃｏｆｌｅｘ、以降はＰＢＡＴと記す）を使用した。さらに、生分解性のポリヒドロキシカルボン酸としては、ポリ乳酸（株式会社島津製作所製のＬＡＣＴＹ ９０３０、以降はＰＬＡと記す）を使用した。
【００４２】
さらに、実施例との比較のため、生分解性脂肪族ポリエステル樹脂であるポリエチレンサクシネート（株式会社日本触媒製のルナーレ ＳＥ、以降はＰＥＳＵと記す）と、転がり軸受用保持器の材料として一般的に使用されている６６ナイロン（宇部興産株式会社製の宇部ナイロン グレード２０２０Ｕ、以降はＰＡ６６と記す）とを使用した。
さらに、補強材としては、ガラス繊維（富士ファイバーガラス株式会社製のグレードＦＥＳＳ−０１５−０４１３）を使用した。
【００４３】
これらの原料を表２〜５に示すような配合比率で配合し、ヘンシェルミキサーを用いて混合した。そして、この混合物を２軸押出機を用いてペレット化し、このペレットを射出成形機に投入して、ＪＩＳ１号形試験片と図２に示すような冠形保持器（呼び番号６３０５の転がり軸受用の保持器）と図３に示すようなシールとを射出成形した。なお、各樹脂を別々にペレット化し、各ペレットを所定の比率でペレットブレンドしたものを射出成形して、前記試験片と前記保持器と前記シールとを製造してもよい。
【００４４】
製造したＪＩＳ１号形試験片については、生分解性と耐熱性を評価した。また、保持器については、射出成形性と、転がり軸受を組み立てる作業における組み込み性とを評価し、さらに、組み立てた転がり軸受を使用して耐久性を評価した。また、シールについては、射出成形性と、転がり軸受を組み立てる作業における組み込み性とを評価し、さらに、組み立てた転がり軸受を使用してクリープ変形及びグリース漏れ性を評価した。
【００４５】
以下に、各試験の方法を説明する。
（１）生分解性試験
ＪＩＳ１号形試験片を温度６０℃，含水率３０質量％の腐葉土中に埋設して生分解させ、外観変化及び重量変化を調査した。なお、試験片を埋設した腐葉土を恒温恒湿槽内に設置することにより、腐葉土中の温度と含水率を適度なものに保持した。
【００４６】
そして、試験片の重量が初期の２０％以下となった時間、又は初期形状を維持できずに崩壊した時間を生分解完了時間とし、その時間の長さによって生分解性を評価した。
試験結果を表２〜５に示す。なお、表２〜５及び図５〜８のグラフにおける生分解完了時間の数値は、比較例１１の生分解完了時間を１とした場合の相対値で示してある。
（２）耐熱性試験
ＪＩＳ１号形試験片を所定の温度（６０，７０，８０，９０，１００，１１０，１２０，１３０℃）に設定した恒温槽内に１０００時間吊り下げた後に、引張破断強度を測定した。そして、初期の引張破断強度からの強度低下が１０％以内である温度のうち最高温度を、その樹脂組成物の耐熱温度とした。試験結果を表２〜５に併せて示す。
（３）射出成形性試験
保持器及びシールを射出成形した際の、金型からの離型のしやすさ、離型時の変形，割れ、及び成形後のそり，収縮をそれぞれ評価した。試験結果を表２〜５に併せて示す。なお、表２〜５においては、離型時の変形，割れと成形後のそり，収縮とが全く生じなかった場合を○印で示し、これらが少しでも生じた場合を×印で示した。
（４）組み込み性試験
転がり軸受（呼び番号６３０５、内径２５ｍｍ，外径６２ｍｍ，幅１７ｍｍ）用の内輪，外輪，転動体を用意し、保持器を組み込むことができるような状態に配置した。そして、エアシリンダを使用して保持器を組み込んで、組み込みによる保持器の変形や破損を評価した。
【００４７】
また、グリース（増ちょう剤がリチウム石けん、基油がエステル油、混和ちょう度が２５０の生分解性グリース）を封入した転がり軸受（呼び番号６２０３、内径１６ｍｍ，外径４０ｍｍ，幅１２ｍｍ）に、エアシリンダを使用してシールを組み込んで、組み込みによるシールの変形や破損を評価した。
試験結果を表２〜５に併せて示す。なお、表２〜５においては、組み込みによる変形，破損が全く生じなかった場合を○印で示している。
（５）耐久性試験
上記の保持器の組み込み性試験において組み立てた転がり軸受について、図４に示す軸受回転試験機を使用して耐久性を評価した。図４中、符号２１は評価対象の試験軸受を表し、支持軸受２２，２２に支持された軸２０の回転に伴って、試験軸受の内輪が回転する。試験条件は以下の通りである。なお、この試験条件は、本発明に係る転がり軸受が一般的な用途に幅広く対応可能であるかどうか判断することを目的として設定したものである。
【００４８】
回転速度 ：９０００ｍｉｎ^-1
ラジアル荷重 ：９８Ｎ
アキシアル荷重：２４５Ｎ
雰囲気温度 ：８０℃
潤滑剤 ：グリース
使用したグリースは、増ちょう剤がリチウム石けん、基油がエステル油、混和ちょう度が２５０の生分解性グリースである。また、グリースの封入量は、通常は軸受空間容積の３５％程度であるが、加速試験とするため１０％とした。
【００４９】
試験結果を表２〜５に示す。表に示した数値は、１種の試験軸受につき１０個ずつ試験を行って、そのうち１０％の試験軸受が寿命に達するまでのＬ₁₀寿命をワイブル分布曲線から求めたものである。なお、回転試験を５００時間行っても寿命に達しない試験軸受については、その時点で試験を打ち切った。
（６）クリープ変形試験及びグリース漏れ性試験
上記のシールの組み込み性試験において組み立てた転がり軸受を、所定の温度（８０，１００，１２０℃）に設定した恒温槽内のガラス板上に載置した。そして、１０００時間後のクリープ変形とグリースの漏れとを評価した。
【００５０】
シールの取付嵌合部は弾性変形した状態で外輪の嵌合溝に押し込まれているため（図３を参照）、雰囲気温度や軸受の回転に伴う発熱によりクリープ変形を起こして嵌合溝への固定力が低下することが多い。また、プラスチックは金属よりも線膨張係数が大きいため、温度が上がるとシールは径方向に膨張して常温状態よりも弾性変形量（締め付け力）が大きくなって、よりクリープ変形を起こしやすい。そして、この固定力が小さくなると、密封性能が低下するだけでなく、シールが小さな力で外輪から脱落してしまう場合がある。
【００５１】
試験結果を表２〜５に併せて示す。なお、表２〜５においては、クリープ変形及びグリースの漏れが転がり軸受の実用上問題のないレベルであった場合を○印で示し、問題が生じるレベルであった場合を×印で示している。
次に、上記各試験の結果について、表２〜５及びグラフを参照しながら説明する。
まず、生分解性樹脂の種類の影響について、表２の参考例１２及び比較例１１，１２（補強材の含有量はいずれも２０質量％）の結果を比較して考察する。
【００５２】
【表２】

【００５３】
ＰＥＴ改質品を使用した参考例１２は、優れた生分解性と高い耐熱性を示し、また、保持器とシールの射出成形性及び組み込み性も良好であった。さらに、耐久性試験においては、１０個すべての試験軸受が回転試験を５００時間行っても寿命に達しなかった。そして、回転試験終了後の保持器に摩耗，破損，変形等の異常は認められず、継続して稼働させることが可能であった。さらにまた、シールのクリープ変形及びグリースの漏れは実用上問題のないレベルであった。
【００５４】
これに対して、ＰＥＳＵを使用した比較例１１は、生分解性は優れているものの、耐熱性がかなり低かった。また、保持器とシールの射出成形性及び組み込み性は良好であったが、耐久性試験では試験開始直後に保持器が熱変形を起こし、試験を継続することができなかった。また、シールのクリープ変形試験においては、試験２４時間後にはシール全体が大きく変形し、グリースが多量に漏洩したため試験を中止した。
【００５５】
また、ＰＡ６６を使用した比較例１２は、耐熱性，射出成形性，組み込み性，耐久性，クリープ変形，及びグリース漏れ性は良好であったが、生分解性試験では４０００時間経過後も重量変化及び形状変化がほとんど認められず、生分解が進行しなかった。
次に、生分解性樹脂組成物中の補強材の含有量の影響について、表２（参考例１１〜１５及び比較例１３，１４）とそれをグラフ化した図５のグラフとを参照しながら考察する。なお、このグラフにおいては、生分解完了時間を○印、Ｌ₁₀寿命を●印で示してある。
【００５６】
表２から分かるように、参考例１１〜１５は、優れた生分解性と高い耐熱性を示し、また、保持器とシールの射出成形性及び組み込み性も良好であった。ガラス繊維の含有量が４９質量％である参考例１５だけは、他の参考例１１〜１４と比較して生分解完了までに若干時間を要したものの、実用上は問題のないレベルの生分解性である。
また、耐久性試験においては、１０個すべての試験軸受が回転試験を５００時間行っても寿命に達しなかった。そして、回転試験終了後の保持器に摩耗，破損，変形等の異常は認められず、継続して稼働させることが可能であった。
【００５７】
さらに、参考例１１〜１５は、シールのクリープ変形及びグリースの漏れは実用上問題のないレベルであった。参考例１１だけは参考例１２〜１５と比較してクリープ変形が若干大きく、初期と比較してシールの固定力が減少したが、実用上問題のないレベルであった。ただし、シールがこのクリープ変形試験よりも高温に曝される場合も考えられるので、ガラス繊維の含有量は２０質量％以上とすることがより好ましい。
【００５８】
これに対して、ガラス繊維を含有していない（樹脂のみ）比較例１３は、保持器の強度が不十分となり、耐久性試験では試験開始約２０時間後に保持器が変形を起こし、試験を継続することができなかった。また、シールを転がり軸受に組み込む際にシールが破損した。
また、ガラス繊維の含有量が６０質量％と多量である比較例１４は、生分解性と耐熱性は良好であったが、樹脂組成物の溶融流動性が不十分であるため、射出成形法により保持器及びシールを成形することが困難であった。
【００５９】
次に、生分解性樹脂組成物中のＰＬＡ（生分解性ポリヒドロキシカルボン酸）の含有量の影響について、表３（参考例１１，１６〜１９及び比較例１５）とそれをグラフ化した図６のグラフとを参照しながら考察する。なお、このグラフにおいては、生分解完了時間を○印、Ｌ₁₀寿命を●印、耐熱温度を△印で示してある。
【００６０】
【表３】

【００６１】
表３から分かるように、参考例１６〜１９は、いずれも優れた生分解性と高い耐熱性を示し、また、保持器とシールの射出成形性及び組み込み性も良好であった。さらに、耐久性試験においては、１０個すべての試験軸受が回転試験を５００時間行っても寿命に達しなかった。そして、回転試験終了後の保持器に摩耗，破損，変形等の異常は認められず、継続して稼働させることが可能であった。さらにまた、シールのクリープ変形及びグリースの漏れは、実用上問題のないレベルであった。
【００６２】
ＰＬＡの含有量が４０質量％である参考例１９だけは、他の参考例１１，１６〜１８と比較して耐熱温度が若干低かったが、耐久性試験においては特に問題はなかった。また、シールのクリープ変形もやや大きかった（初期と比較してシールの固定力が減少した）ものの、参考例１１とほぼ同レベルで実用上の問題はなかった。
ただし、この耐熱性試験の結果及びクリープ変形試験の結果から考えると、本耐久性試験よりも高い耐熱性が要求されるような場合には、ＰＬＡの含有量を３０質量％以下とする方が好ましいと考えられる。
【００６３】
一方、ＰＬＡの含有量をさらに高くすると、耐熱性が一層低下する傾向がある。ＰＬＡの含有量がさらに高い比較例１５は耐熱温度がさらに低く、また、Ｌ₁₀寿命も低かった。さらに、シールのクリープ変形が大きく、グリースの漏れも多量で、実用上の問題があった。
なお、表３には示していないが、ＰＬＡを含有する生分解性樹脂組成物の場合（参考例１６〜１９及び比較例１５）は、保持器を射出成形法により製造する際に、金型内に射出した樹脂の冷却時間を短縮することができた。
【００６４】
次に、生分解性樹脂組成物中のＰＢＡＴ（引張破断伸びが５０％以上である生分解性ポリエステル樹脂）の含有量の影響について、表４（参考例１２、実施例１，２、及び比較例１６）とそれをグラフ化した図７のグラフとを参照しながら考察する。なお、このグラフにおいても、生分解完了時間を○印、Ｌ₁₀寿命を●印、耐熱温度を△印で示してある。
【００６５】
【表４】

【００６６】
表４から分かるように、実施例１，２は、いずれも優れた生分解性と高い耐熱性を示し、また、保持器とシールの射出成形性及び組み込み性も良好であった。さらに、耐久性試験においては、１０個すべての試験軸受が回転試験を５００時間行っても寿命に達しなかった。そして、回転試験終了後の保持器に摩耗，破損，変形等の異常は認められず、継続して稼働させることが可能であった。さらにまた、シールのクリープ変形及びグリースの漏れは、実用上問題のないレベルであった。
【００６７】
ＰＢＡＴの含有量が２０質量％である実施例２だけは、他の参考例１２及び実施例１と比較して耐熱温度が若干低かったものの、耐久性試験においては特に問題はなかった。ただし、この耐熱性試験の結果から考えると、本耐久性試験よりも高い耐熱性が要求されるような場合には、ＰＢＡＴの含有量を１０質量％以下とする方が好ましいと考えられる。 一方、ＰＢＡＴの含有量をさらに高くすると、耐熱性及び機械的強度が一層低下する傾向がある。ＰＢＡＴの含有量がさらに高い比較例１６は、耐熱温度がさらに低く、また、Ｌ₁₀寿命も低かった。さらに、シールのクリープ変形が大きく、グリースの漏れも多量で、実用上の問題があった。
【００６８】
なお、表４には示していないが、ＰＢＡＴを含有する生分解性樹脂組成物の場合（実施例１，２及び比較例１６）は靱性が優れているため、アンダーカット部の大きい保持器であっても、金型から離型する際の保持器の損傷を防止することができた。また、金型から離型する際のシールの破損を防止すること及び転がり軸受に組み込む際のシールの破損を防止することにも効果があった。
特に、転がり軸受に組み込む際の破損防止効果は大きく、外輪の嵌合溝の最小径部（図３を参照）が小径である規格外の転がり軸受にも、シールを問題なく組み込むことができた。樹脂製のシールを転がり軸受に組み込む際には、シールの弾性を利用しシールの取付嵌合部が外輪の嵌合溝の最小径部を乗り越えるようにして、シールの取付嵌合部を軸受の嵌合溝にはめ込むので、最小径部が小径であるとシールの組み込みが難しくなる。
【００６９】
次に、ＰＬＡとＰＢＡＴの両方を使用した場合に生じる、生分解性樹脂組成物中のＰＬＡ及びＰＢＡＴの合計の含有量の影響について、表５（参考例１３、実施例３〜６、及び比較例１７）とそれをグラフ化した図８のグラフとを参照しながら考察する。なお、このグラフにおいても、生分解完了時間を○印、Ｌ₁₀寿命を●印、耐熱温度を△印で示してある。
【００７０】
【表５】

【００７１】
表５から分かるように、実施例３〜６は、いずれも優れた生分解性と高い耐熱性を示し、また、保持器とシールの射出成形性及び組み込み性も良好であった。さらに、耐久性試験においては、１０個すべての試験軸受が回転試験を５００時間行っても寿命に達しなかった。そして、回転試験終了後の保持器に摩耗，破損，変形等の異常は認められず、継続して稼働させることが可能であった。さらにまた、シールのクリープ変形及びグリースの漏れは、実用上問題のないレベルであった。
【００７２】
ＰＬＡ及びＰＢＡＴの合計の含有量がＰＥＴ改質品の含有量よりも多量である実施例６だけは、他の参考例１３及び実施例３〜５と比較して耐熱温度が若干低かったものの、耐久性試験においては特に問題はなかった。ただし、この耐熱性試験の結果から考えると、本耐久性試験よりも高い耐熱性が要求されるような場合には、ＰＬＡ及びＰＢＡＴの合計の含有量をＰＥＴ改質品の含有量より少なくする方が好ましいと考えられる。
【００７３】
一方、ＰＬＡ及びＰＢＡＴの合計の含有量をさらに高くして、ＰＥＴ改質品の含有量をさらに低くすると、耐熱性が一層低下する傾向がある。そのような比較例１７は、耐熱温度がさらに低く、また、Ｌ₁₀寿命も低かった。さらに、シールのクリープ変形試験においては、試験１００時間後にはシール全体が大きく変形し、グリースが多量に漏洩したため試験を中止した。
なお、表５には示していないが、ＰＬＡとＰＢＡＴの両方を含有する生分解性樹脂組成物の場合（実施例３〜６及び比較例１７）は、金型内に射出した樹脂の冷却時間を短縮する効果と、金型から離型する際の保持器の損傷を防止する効果との両方を有することが認められた。また、金型から離型する際のシールの破損を防止すること及び転がり軸受に組み込む際のシールの破損を防止することにも効果が認められた。
【００７４】
次に、本発明に係る機械部品の実施の形態を、図面を参照しながら詳細に説明する。
〔第一実施形態〕
図１は、本発明に係る機械部品の一実施形態である転がり軸受の構成を示す縦断面図である。
図１の深溝玉軸受は、内輪１１と、外輪１２と、該両輪１１，１２の間に転動自在に配設された複数の玉１３と、両輪１１，１２の間に複数の玉１３を深溝玉軸受の円周方向にわたって等配に保持する冠形保持器１４（図２を参照）と、両輪１１，１２の間に介在された接触形のシール１５と、を備えている。
【００７５】
このシール１５は環状で、外輪１２の内周面（内輪１１の外周面でもよい）に設けられたシール溝１２ａに嵌合するための取付嵌合部１５ａ（外周縁部）と、内輪１１の外周面に滑り接触するリップ部１５ｂと、取付嵌合部１５ａとリップ部１５ｂとを連結する連結部１５ｃと、で構成されている。このようなシール１５は外輪１２の両端部の内周面に取り付けられて、外輪１２の内周面と内輪１１の外周面との間の開口部分を覆っている。そして、外部からの異物の侵入や内部からのグリースの漏出を防止している。
【００７６】
なお、シール１５は非接触形でもよいし、金属製又は樹脂製の芯金を有しているタイプでもよい。また、シール１５の全体形状やリップ部１５ｂ等の細部の形状も図１のものに限定されるものではなく、図３に示すような形状のシールをはじめとして、種々の形状を採用可能であることは言うまでもない。さらに、外輪１２のシール溝１２ａの形態も、図１のものに限定されるものではない。
このような深溝玉軸受の保持器１４及びシール１５は、生分解性樹脂組成物で構成されている。すなわち、保持器１４は、前述の参考例２に使用した生分解性樹脂７０質量％と、充填材である炭酸カルシウムウィスカー（アルゴナイト）３０質量％とを混合した樹脂組成物で構成されている。なお、炭酸カルシウムウィスカーは、丸尾カルシウム株式会社製の商品名ウィスカルを使用した。
【００７７】
また、シール１５は、前述の参考例４に使用した生分解性樹脂８５質量％と、充填材である炭酸カルシウムウィスカー（アルゴナイト）１５質量％とを混合した樹脂組成物で構成されている。炭酸カルシウムウィスカーは、上記のものと同様である。
なお、内輪１１，外輪１２，及び玉１３は軸受鋼で構成されている。
これらの樹脂組成物は、優れた耐熱性を有するとともに、機械的性質の経時的な低下が生じにくいので、該樹脂組成物でその一部が構成された上記の深溝玉軸受は、転がり軸受として十分な性能を備えている。また、この深溝玉軸受が土壌中等の自然環境に放出されても、前記生分解性樹脂組成物で構成された部分は自然に分解されるから、自然環境に対して悪影響を及ぼしにくい。
【００７８】
なお、内輪１１，外輪１２，及び玉１３についても、生分解性樹脂組成物で構成することができる。例えば、前述の参考例１に使用した生分解性樹脂６０質量％と、充填材である前述の炭酸カルシウムウィスカー４０質量％と、からなる生分解性樹脂組成物で構成することができる（保持器１４及びシール１５については、前述と同様の生分解性樹脂組成物で構成されている）。
このような深溝玉軸受は、全体が生分解性樹脂組成物で構成されているので、土壌中等の自然環境に放出された場合は、全体が自然に分解される。したがって、自然環境に対する悪影響が極めて小さい。このような深溝玉軸受は土壌中等の自然環境に廃棄処分することも可能であるので、使用後の廃棄が容易である。
【００７９】
本実施形態においては、転がり軸受の例として深溝玉軸受をあげて説明したが、本発明は、他の種類の様々な転がり軸受に対して適用することができる。例えば、アンギュラ玉軸受，円筒ころ軸受，円すいころ軸受，針状ころ軸受，自動調心ころ軸受等のラジアル形の転がり軸受や、スラスト玉軸受，スラストころ軸受等のスラスト形の転がり軸受である。
〔第二実施形態〕
図９は、本発明に係る機械部品の一実施形態である直動案内軸受装置の構成を示す斜視図である。また、図１０は、図９の直動案内軸受装置を軸方向から見た正面図である。
【００８０】
角形の案内レール３１上に、横断面形状がほぼコ字形のスライダ３２が軸方向に相対移動可能に跨架されている。このスライダ３２は、スライダ本体３２Ａの軸方向の両端部にエンドキャップ３２Ｂ，３２Ｂが着脱可能に固着されて構成されている。
また、案内レール３１の上面３１ａと両側面３１ｂ，３１ｂが交差する稜線部には、断面ほぼ１／４円弧形状の凹溝である転動体転動溝３３Ａ，３３Ａが軸方向に形成されている。さらに、案内レール３１の両側面３１ｂ，３１ｂの中間位置には、断面ほぼ半円形の凹溝である転動体転動溝３３Ｂ，３３Ｂが軸方向に形成されている。なお、転動体転動溝３３Ｂの溝底には、転動体３５の脱落を防ぐ後述の保持器３６のための逃げ溝３３ａが、軸方向に形成されている。
【００８１】
一方、スライダ３２の本体３２Ａの両袖部３４，３４の内側のコーナ部には、案内レール３１の転動体転動溝３３Ａに対向する断面ほぼ半円形の負荷転動体転動溝４１が形成され、両袖部３４，３４の内側面の中央部には案内レール３１の転動体転動溝３３Ｂに対向する断面ほぼ半円形の負荷転動体転動溝４２が形成されている。
そして、上記の案内レール３１の転動体転動溝３３Ａとスライダ３２の負荷転動体転動溝４１とで負荷転動体転動路４３が構成され、案内レール３１の転動体転動溝３３Ｂとスライダ３２の負荷転動体転動溝４２とで負荷転動体転動路４４が構成されている。
【００８２】
また、スライダ本体３２Ａの袖部３４の上部肉厚に、負荷転動体転動路４３に平行な軸方向に延びる断面円形の貫通孔からなる転動体戻し路４５が形成され、袖部３４の下部肉厚内に、負荷転動体転動路４４に平行な同様の軸方向に延びる貫通孔からなる転動体戻し路４６が形成されている。
エンドキャップ３２Ｂは樹脂材料の射出成形品であり、断面ほぼコ字状に形成されている。そして、スライダ本体３２Ａとの接合面（裏面）には、図１１に示すように、斜めに傾斜した半円状の上凹部５１と下凹部５２とが、両袖分部３４，３４の上下に形成されるとともに、半円状の両凹部５１，５２の中心部を横断して半円柱状の凹溝５３が設けてある。
【００８３】
そして、その半円柱状の凹溝５３には、樹脂材料を射出成形して得た半円筒状のリターンガイド５５（図１２を参照）が嵌合される。なお、図１３は、リターンガイド５５が装着されたエンドキャップ３２Ｂの斜視図である。このリターンガイド５５の外径面の中央部には、転動体３５の案内面となる断面円弧状の凹溝５６が半円状に形成され、また、リターンガイド５５の内径側の凹部５７は潤滑剤通路であり、その凹部５７から外径側の凹溝５６に抜ける貫通孔５７Ａが給油孔として形成されている。
【００８４】
このようなリターンガイド５５を半円柱状の凹溝５３に組み込むことにより、エンドキャップ３２Ｂの裏面に断面円形の半ドーナツ状の湾曲路５８が上下二段に形成される（図１４を参照）。このエンドキャップ３２Ｂをスライダ本体３２Ａに取り付けると、湾曲路５８によって、スライダ本体３２Ａの負荷転動体転動路４４と転動体戻し路４６とが連通される。そして、上段の負荷転動体転動路４３と転動体戻し路４５も同様に連通される。
【００８５】
上記の負荷転動体転動路４３，４４，転動体戻し路４５，４６，湾曲路５８で構成される転動体無限循環経路に、多数の転動体３５が転動自在に装填されている。
案内レール３１上をスライダ３２が移動すると、転動体３５は負荷転動体転動路４３，４４内を転動しつつスライダ３２の移動方向にスライダ３２より遅い速度で移動し、一端側の湾曲路５８でＵターンして転動体戻し路４５，４６を逆方向に転動しつつ移動し、他端側の湾曲路５８で逆Ｕターンして負荷転動体転動路４３，４４内に戻る循環を繰り返す。
【００８６】
なお、エンドキャップ３２Ｂにおいて、転動体３５を案内する湾曲路５８の内側端部には半円状に突出させた転動体掬いあげ突部５９が形成され、その鋭角の先端が案内レール３１の転動体転動溝３３Ａ，３３Ｂの溝底に近接するようにされている。下段の転動体掬いあげ突部５９には、後述する保持器３６の取付溝５９ａと取付穴５９ｂとが設けてある。
また、エンドキャップ３２Ｂの表側の給油ニップル３７から注入された潤滑剤が、エンドキャップ３２Ｂの裏面の給油溝６０を通りリターンガイド５５の内径側の凹部５７から貫通孔５７Ａを経て、湾曲路５８内へ送り込まれるようになっている。さらに、エンドキャップ３２Ｂの裏面の給油溝６０の下方には、後述する保持器６１の取付け穴６１ａが形成してある。
【００８７】
スライダ３２の上段の負荷転動体転動路４３及び下段の負荷転動体転動路４４にそれぞれ装填された転動体３５は、スライダ３２を案内レール３１に組み付けない状態では脱落してしまう。よって、これを防止するために、射出成形された樹脂材料製の保持器が用いられている。
下段の負荷転動体転動路４４内の転動体脱落防止用の保持器３６は、断面角形状の保持器で、その長手方向の両端側は転動体３５を滑らかに案内するため弓なりに湾曲され、端末には取付け部が形成されている。装着は、エンドキャップ３２Ｂの転動体掬いあげ突部５９に形成された保持器取付け穴５９ｂに前記取付け部を差し込んで行われる。スライダ３２を案内レール３１に組みつけた状態では、保持器３６は案内レール３１の保持器用の逃げ溝３３ａ内に収容され、案内レール３１とは干渉しない。
【００８８】
これに対して、上段の負荷転動体転動路４３内の転動体脱落防止用の保持器６１は、図１５に示すようにほぼ長方形の枠形状である。この保持器６１は、その枠６２の長手方向の外側縁にほぼ１／４円弧状の転動体保持面６３が形成され、前後端には係止突部６４が突設されている。装着は、エンドキャップ３２Ｂの裏面の取付け穴６１ａに係止突部６４を差し込むことにより行われる。これにより保持器６１はエンドキャップ３２Ｂに支持されて、案内レール３１の上面３１ａとこれに向き合うスライダ本体３２Ａの内面との間の空間に収容され、転動体３５を転動体保持面６３と負荷転動体転動溝４１の溝面とで挟持して保持する。
【００８９】
このような直動案内軸受装置は、その一部が前述のように樹脂材料で構成されていて、この樹脂材料は、例えば、前述の参考例１に使用した生分解性樹脂６０質量％と、充填材である前述の炭酸カルシウムウィスカー４０質量％と、からなる生分解性樹脂組成物である。なお、従来の直動案内軸受装置においては、ポリアセタール樹脂が使用されていた。 これらの樹脂組成物は、優れた耐熱性を有するとともに、機械的性質の経時的な低下が生じにくいので、該樹脂組成物でその一部が構成された上記の直動案内軸受装置は、転動装置として十分な性能を備えている。また、この直動案内軸受装置が土壌中等の自然環境に放出されても、前記生分解性樹脂組成物で構成された部分は自然に分解されるから、自然環境に対して悪影響を及ぼしにくい。
【００９０】
〔第三実施形態〕
図１６は、本発明に係る機械部品の一実施形態である直動案内軸受装置用スライダの仮軸の構成を示す斜視図である。また、図１７は、スライダが組み付けられた状態の仮軸を示す斜視図である。
この仮軸１０１は、直動案内軸受装置用の案内レールとほぼ同一の形状に形成されている。すなわち、仮軸１０１の軸方向に垂直をなす面で破断した断面形状は、前記案内レールのそれとほぼ同一の形状をなしている。
【００９１】
そして、角状の仮軸１０１の上面１０１ａと両側面１０１ｂとが交差する稜線部には、転動体転動溝に相当する断面ほぼ１／４円弧形状の凹溝１０２Ａが軸方向に形成され、仮軸１０１の両側面１０１ｂの中間位置には、転動体転動溝に相当する断面ほぼ半円形の凹溝１０２Ｂが軸方向に形成されている。さらに、両側面１０１ｂの中間位置に形成された凹溝１０２Ｂの溝底には、前記案内レールと同様にボール保持器用の逃げ溝１０３が形成されている。
【００９２】
ただし、案内レールとは異なり、仮軸１０１はスライダ１０５を仮に組み付けておくためのものであるから、図１６及び図１７に示すように、その軸方向の長さはスライダ１０５の軸方向の長さよりも若干長ければ十分である。また、仮軸１０１の上面１０１ａは機能上平面状である必要はないので、仮軸１０１の寸法精度を向上させるために、凹状の肉ヌスミ１０４が設けてある。なお、肉ヌスミ１０４の内部には、肉ヌスミ１０４を補強するための補強板１０４ａが設けてある。
【００９３】
スライダ１０５が組み付けられた仮軸１０１を前記案内レールの端部に連続するように取り付け、スライダ１０５を仮軸１０１から案内レールに向けてスライドさせると、仮軸１０１に組み付けられていたスライダ１０５を案内レールに移動させることができる。
このような仮軸１０１は、例えば、前述の参考例１に使用した生分解性樹脂９０質量％と、充填材である前述の炭酸カルシウムウィスカー１０質量％と、からなる生分解性樹脂組成物を、射出成形することによって製造される。
【００９４】
したがって、スライダ１０５を案内レールに移動させた後の仮軸１０１を廃棄物として土壌中に埋設処理すると、自然に生分解されるから、自然環境に悪影響を及ぼしにくく、また、廃棄物問題の要因となりにくい。
なお、上記の第一〜第三実施形態は本発明の一例を示したものであり、本発明は上記の各実施形態に限定されるものではない。
例えば、生分解性樹脂組成物に使用する生分解性樹脂の種類，充填材の種類，添加剤の種類，及びこれらの配合比率等は、本実施形態に限定されるものではなく、使用温度，形状，使用目的等に応じて適宜選択することが可能である。例えば、表４，５に記載された実施例の構成としてもよい。
【００９５】
また、本実施形態においては、機械部品の例として玉軸受，直動案内軸受装置，及び直動案内軸受装置用スライダの仮軸をあげて説明したが、本発明は、他の種々の機械部品に対して適用することができる。例えば、ボールねじ等の転動装置である。
【００９６】
【発明の効果】
以上のように、本発明に係る生分解性樹脂組成物は、耐熱性に優れるとともに機械的性質の経時的な低下が生じにくい。
また、本発明に係る転がり軸受等の機械部品は、優れた耐熱性を有するとともに、機械的性質の経時的な低下が生じにくい。よって、種々の産業分野において使用することが可能である。さらに、本発明に係る転がり軸受等の機械部品は優れた生分解性を有しているので、土壌中等の自然環境に放出されると自然に分解され、自然環境に対して悪影響を及ぼしにくい。よって、土壌中等の自然環境に廃棄処分することも可能であり、使用後の廃棄が容易となる。
【図面の簡単な説明】
【図１】本発明に係る機械部品の一実施形態である深溝玉軸受の構造を示す縦断面図である。
【図２】図１の深溝玉軸受に使用されている冠形保持器を示す斜視図である。
【図３】本発明に係る転がり軸受用シールの構成を説明するシール及び転がり軸受の断面図である。
【図４】軸受回転試験機の構成を示す断面図である。
【図５】生分解性樹脂組成物中のガラス繊維の含有量と生分解完了時間及びＬ₁₀寿命との相関を示すグラフである。
【図６】生分解性樹脂組成物中のＰＬＡの含有量と生分解完了時間，Ｌ₁₀寿命，及び耐熱温度との相関を示すグラフである。
【図７】生分解性樹脂組成物中のＰＢＡＴの含有量と生分解完了時間，Ｌ₁₀寿命，及び耐熱温度との相関を示すグラフである。
【図８】生分解性樹脂組成物中のＰＬＡ及びＰＢＡＴの合計の含有量と生分解完了時間，Ｌ₁₀寿命，及び耐熱温度との相関を示すグラフである。
【図９】本発明に係る機械部品の別の実施形態である直動案内軸受装置の構成を示す斜視図である。
【図１０】図９の直動案内軸受装置の正面図である。
【図１１】リターンガイドを省略してエンドキャップの裏面を示した図である。
【図１２】リターンガイドの正面図である。
【図１３】リターンガイドを装着した状態のエンドキャップの斜視図である。
【図１４】図１０のエンドキャップ付近のＡ−Ａ線部分断面図である。
【図１５】保持器の斜視図である。
【図１６】本発明に係る機械部品の別の実施形態である直動案内軸受装置用スライダの仮軸を示す斜視図である。
【図１７】スライダを組み付けた状態の仮軸を示す斜視図である。
【符号の説明】
１１ 内輪
１２ 外輪
１３ 玉
１４ 保持器
１５ シール
３２Ｂ エンドキャップ
３６ 保持器
５５ リターンガイド
６１ 保持器
１０１ 仮軸[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biodegradable resin composition that is excellent in heat resistance and hardly deteriorates in mechanical properties over time. In addition, the present invention relates to a machine part that is excellent in biodegradability and hardly adversely affects the natural environment even if it is released into the natural environment such as soil.
[0002]
[Prior art]
When the biodegradable resin is left in the soil or the like, it is gradually decomposed into carbon dioxide and water by bacteria. Therefore, a resin product composed of a biodegradable resin is naturally decomposed until it does not retain its original shape even when released into the natural environment, and thus hardly adversely affects the natural environment. For these reasons, biodegradable resins are mainly used as materials for garbage bags, bottle containers, agricultural multi-films, etc., and the amount used has been increasing in recent years.
[0003]
On the other hand, currently commonly used biodegradable resins include, for example, polybutylene succinate, polyethylene succinate, polycaprolactone, polylactic acid, etc., most of which are aliphatic polyester resins.
[0004]
[Problems to be solved by the invention]
However, the conventional biodegradable resin (aliphatic polyester resin) as described above has the following problems.
(1) Low heat resistance. That is, many have a melting point of about 100 to 120 ° C., and even a high melting point is about 170 ° C. Moreover, even if it has a high melting point, there are many cases where the mechanical properties are greatly reduced at a temperature of about 100 ° C.
[0005]
{Circle around (2)} Since hydrolysis proceeds gradually due to moisture in the air, mechanical properties tend to deteriorate over time.
Therefore, it has been difficult to apply conventional biodegradable resins to materials constituting machine parts such as rolling bearings.
Accordingly, an object of the present invention is to provide a biodegradable resin composition that solves the problems of the conventional techniques as described above and has excellent heat resistance and is less likely to cause deterioration in mechanical properties over time. . It is another object of the present invention to provide a mechanical component that is excellent in biodegradability and hardly adversely affects the natural environment even when released into the natural environment.
[0006]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention has the following configuration. That is, the biodegradable resin composition according to claim 1 of the present invention is a resin composition containing a biodegradable resin, wherein the biodegradable resin is polycondensed between an aliphatic dibasic acid and an aliphatic diol. Polyester resin having in its molecular structure an aliphatic component composed of at least one of an aliphatic polyester component and an aliphatic polyether component, and an aromatic polyester component obtained byAnd at least a part of the polyester resin is a biodegradable polyester resin having a tensile elongation at break of 50% or more, and the content of the biodegradable polyester resin having a tensile elongation at break of 50% or more is 20% by mass or less of the entire compositionIt is characterized by that.
[0007]
  BookThe polyester resin in the invention is a resin (copolymer) having, in a molecular structure, an aromatic polyester component having high heat resistance and hardly biodegradable and an aliphatic component easily biodegradable in a predetermined ratio. Since it contains an aromatic polyester component having high heat resistance, the polyester resin has excellent heat resistance such as a high melting point and high high-temperature rigidity. In addition, due to the action of an aromatic polyester component that is not readily biodegradable, the polyester resin is less susceptible to hydrolysis due to moisture in the air and the like, and mechanical properties are less likely to deteriorate over time.
[0008]
  Therefore, the biodegradable resin composition of the present invention can be applied as a material constituting a mechanical part such as a rolling bearing that requires excellent heat resistance and mechanical properties. In particular, since a resin composition containing a polyester resin having a high melting point of 170 ° C. or higher can sufficiently exhibit the excellent heat resistance required for mechanical parts, it is suitable as a material constituting the mechanical parts. .
  Furthermore, when a biodegradable polyester resin having a tensile elongation at break of 50% or more is contained, the toughness of the biodegradable resin composition can be improved. For example, when manufacturing a rolling bearing cage with a spherical pocket and having an undercut portion by injection molding, it does not contain biodegradable polyester resin with a tensile elongation at break of 50% or more and biodegradation If the toughness of the conductive resin composition is insufficient, the rolling bearing cage may be damaged when released from the mold.
  In addition, when a seal for a rolling bearing is manufactured by an injection molding method, the seal is thin and contains a biodegradable polyester resin having a tensile rupture elongation of 50% or more because the lip is shaped to wrap the mold. However, if the toughness of the biodegradable resin composition is insufficient, the rolling bearing seal may be damaged when released from the mold.
  However, if the biodegradable resin composition contains a biodegradable polyester resin having a tensile elongation at break of 50% or more and the toughness of the biodegradable resin composition is sufficient, damage during release can be prevented, and further, a cage or seal can be removed. It is also possible to prevent damage when incorporated in a rolling bearing.
  The content of the biodegradable polyester resin having a tensile elongation at break of 50% or more is preferably 20% by mass or less based on the entire resin composition. If it exceeds 20% by mass, the heat resistance and mechanical properties of the resin composition will be insufficient. If the content of the biodegradable polyester resin having a tensile elongation at break of 50% or more is 10% by mass or less, it is more preferable because sufficient heat resistance and mechanical properties can be maintained over a long period of time.
  Furthermore, if a biodegradable polyester resin having a tensile elongation at break of 100% or more is used instead of a biodegradable polyester resin having an elongation at break of 50% or more, the inclusion of a biodegradable polyester resin having an excellent tensile elongation at break Even if the amount is reduced, sufficient toughness can be imparted to the biodegradable resin composition, and more sufficient heat resistance and mechanical properties can be maintained over a long period of time.
  Examples of biodegradable polyester resins having a tensile elongation at break of 50% or more include “Ecoflex” which is a copolyester resin (aliphatic and aromatic copolyester) manufactured by BASF Japan, and fat manufactured by Mitsubishi Gas Chemical Co., Ltd. “U-Pec” which is a group polyester carbonate resin, “Cell Green” which is a polycaprolactone manufactured by Daicel Chemical Industries, Ltd., and the like. Among these, “Ecoflex” which is excellent in heat resistance and has a tensile elongation at break of 100% or more is particularly preferable.
  Moreover, the biodegradable resin composition of Claim 2 which concerns on this invention is a biodegradable resin composition of Claim 1, The quantity ratio of the said aromatic polyester component of the said polyester resin, and the said aliphatic component The molar ratio of the repeating units of the respective components is 19: 1 to 5: 5.
  The higher the ratio of the aromatic polyester component in the polyester resin, the better the heat resistance, and the mechanical properties are less likely to deteriorate over time, but conversely the biodegradability decreases, The molar ratio (copolymerization ratio) of the repeating units of the aromatic polyester component and the aliphatic component may be appropriately selected according to the use.
[0009]
This copolymerization ratio is preferably set to aromatic polyester component: aliphatic component = 19: 1 to 5: 5 in view of the balance between heat resistance and resistance to a decrease in mechanical properties over time.
When the amount of the aromatic polyester component is less than 5: 5 (that is, when the aromatic polyester component is less than 50 mol%), the heat resistance becomes insufficient, and the mechanical properties are likely to deteriorate with time. On the other hand, when there are more aromatic polyester components than 19: 1 (that is, when the aliphatic components are less than 5 mol%), the biodegradability becomes insufficient and the natural environment when released into the natural environment. It tends to have an adverse effect on
[0010]
In order to make such inconvenience less likely to occur, the copolymerization ratio is more preferably aromatic polyester component: aliphatic component = 9: 1 to 6: 4.
The structure of the aromatic polyester component in the polyester resin is not particularly limited as long as it is difficult to biodegrade and has high heat resistance, and various aromatic polyesters can be used. In the present invention, the aromatic polyester component is a polyester obtained by polymerizing an aromatic monomer and an aliphatic monomer (for example, a polymer of an aromatic dicarboxylic acid and an aliphatic diol), a so-called semi-aromatic polyester. Means.
[0011]
Specific examples include polyethylene terephthalate (PET, melting point approximately 256 ° C.), polybutylene terephthalate (PBT, melting point approximately 227 ° C.), poly-1,4-cyclohexanedimethylene terephthalate (PCT, melting point approximately 290 ° C.), polyethylene naphthalate. (PEN, melting point: about 272 ° C.), polybutylene naphthalate (PBN, melting point: about 245 ° C.) and the like. These may be used alone or in combination of two or more.
[0012]
However, the higher the melting point (heat resistance) of the aromatic polyester component, the higher the melting point of the entire polyester resin even when more aliphatic components are introduced, so the highest melting point is PET, PCT, and PEN. Is preferred.
On the other hand, the structure of the aliphatic component in the polyester resin is not particularly limited as long as it is an aliphatic polyester or aliphatic polyether.
As a method for introducing an aliphatic polyester component into the molecular structure of the polyester resin, a part of an aromatic dibasic acid (dicarboxylic acid) that is a constituent monomer of the aromatic polyester component is converted into an aliphatic dibasic acid (dicarboxylic acid). And a method of performing polycondensation.
[0013]
Examples of the aliphatic dibasic acid include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and the like.
In addition, as a method for introducing an aliphatic polyether component into the molecular structure of the polyester resin, a part of a diol, which is a constituent monomer of an aromatic polyester component, has a structure represented by the following chemical formula (Chemical Formula 1), for example. A method of performing polycondensation by replacing with an aliphatic polyether diol is exemplified.
[0014]
[Chemical 1]

[0015]
Here, the numerical values of n and m are not particularly limited, but n is preferably 2, 3, or 4, and m is preferably an integer of 2 to 250, particularly preferably an integer of 2 to 100.
In addition, the said polyester resin may have a urethane bond in the molecular structure, if it is 5 mol% or less of the whole. As a method for introducing a urethane bond, a method in which a part of an aromatic dibasic acid (dicarboxylic acid) that is a constituent monomer of an aromatic polyester component is replaced with a diisocyanate compound such as hexamethylene diisocyanate, and polycondensation is performed. can give.
[0016]
Moreover, the biodegradable resin composition of Claim 3 which concerns on this invention is a biodegradable resin composition of Claim 1 or Claim 2, and contains a reinforcing material.
Furthermore, the biodegradable resin composition of claim 4 according to the present invention is the biodegradable resin composition of claim 3, wherein the content of the polyester resin is 30% by mass or more and 90% by mass of the entire resin composition. % Or less, and the content of the reinforcing material is 10% by mass or more and less than 50% by mass of the entire resin composition.
[0017]
The biodegradable resin composition of the present invention can contain a reinforcing material in order to improve its mechanical properties. The type of the reinforcing material is not particularly limited, but those that are listed in the positive list of the Green Plastic Identification and Labeling System operated by the Biodegradable Plastics Research Society (BPS) are preferable. For example, glass fiber, carbon fiber, potassium titanate whisker, light calcium carbonate (crystal form is calcite and argonite), natural hydrous aluminum silicate (kaolin, clay), talc, bentonite, fibrous magnesium hydroxide, wollast Examples include knight, sepiolite, carbon black, mica, silicon dioxide, diatomaceous earth, and the like. Among these reinforcing materials, glass fiber is particularly preferable because of its high reinforcing effect.
[0018]
The content of the reinforcing material is preferably 10% by mass or more and less than 50% by mass of the entire resin composition. If it is less than 10% by mass, the mechanical properties become low, and the mechanical properties required as a material constituting the mechanical parts such as a rolling bearing retainer and a seal cannot be obtained. For example, in the case of a seal, the minimum strength and creep resistance required for the seal cannot be ensured.
Moreover, when it is 50 mass% or more, it becomes difficult to ensure sufficient fluidity of the resin composition during melt molding. If the resin composition has sufficient fluidity, the resin composition can be molded by an injection molding method, which is preferable from the viewpoint of productivity and economy. Furthermore, since the content of inorganic material in the biodegradable resin composition is defined as less than 50% by mass in the BPS green plastic identification display system, the content of the reinforcing material is 50% of the total resin composition. It is preferable to be less than mass%.
[0019]
In addition, as for content of a reinforcing material, it is more preferable to set it as 10 to 40 mass% of the whole resin composition. Then, when machine parts such as rolling bearing cages and seals are composed of the biodegradable resin composition of the present invention, the balance of machine part performance, moldability, productivity, biodegradability, etc. Is better.
Moreover, it is preferable that content of the said polyester resin shall be 30 to 90 mass% of the whole resin composition. If it is less than 30% by mass, the biodegradable resin composition has insufficient heat resistance. In addition, if content of the said polyester resin shall be 40 mass% or more, since sufficient heat resistance can be maintained over a long term, it is more preferable. On the other hand, since there is no particular problem even if the content of the polyester resin is increased, all components other than the reinforcing material in the resin composition may be used as the polyester resin. Therefore, the upper limit of the content of the polyester resin is 90% by mass.
[0024]
Furthermore, the biodegradable resin composition of the present invention may contain a polyhydroxycarboxylic acid having biodegradability. When polyhydroxycarboxylic acid is contained, the releasability from the mold is improved when molding by injection molding. For example, when a rolling bearing retainer or a seal is manufactured by an injection molding method, depending on the shape of the retainer or the seal, it may take time to cool the resin and the productivity may decrease. However, when polyhydroxycarboxylic acid is contained in the biodegradable resin composition, the time required for cooling the resin can be reduced due to the high crystallinity that is one of the characteristics of polyhydroxycarboxylic acid. Will improve.
[0025]
  The content of the polyhydroxycarboxylic acid is preferably 40% by mass or less based on the entire resin composition. When it exceeds 40 mass%, the heat resistance of the biodegradable resin composition will be insufficient. If the content of the polyhydroxycarboxylic acid is 30% by mass or less, sufficient heat resistance can be maintained over a long period of time, which is more preferable.However, in order to maintain sufficient heat resistance and mechanical properties over a long period of time, the total content of both the biodegradable polyester resin having a tensile elongation at break of 50% or more and the polyhydroxycarboxylic acid having biodegradability is contained. The amount is preferably equal to or less than that of the polyester resin, which is the main component of the biodegradable resin composition of the present invention.If there is no problem in releasability from the mold, it does not matter if polyhydroxycarboxylic acid is not included.
[0026]
  The type of polyhydroxycarboxylic acid is not particularly limited. For example, polylactic acid (PLA) has a high melting point and high crystallinity among general polyhydroxycarboxylic acids, and is excellent in cost. So it is suitable.
[0027]
Furthermore, the biodegradable resin composition of the present invention has a range that does not adversely affect its heat resistance, biodegradability, mechanical properties, etc., and the biodegradable resin composition is decomposed and released into the natural environment. If desired, various additives may be blended as long as they do not adversely affect the natural environment.
Examples include lubricants, solid lubricants, thermal stabilizers, antioxidants, thermal conductivity improvers, crystallization accelerators, nucleating agents, pigments, dyes, etc. It is preferable to add according to the system.
[0028]
  Further, according to the present inventionClaim 5Machine partsClaims 1-4It comprised with the biodegradable resin composition in any one of these.
  Furthermore, according to the present inventionClaim 6The rolling bearing according to the present invention is a rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the two wheels, and a cage that holds the rolling element between the two wheels. , At least the cage among the inner ring, the outer ring, the rolling element, and the cage,Claims 1-4It comprised with the biodegradable resin composition in any one of these.
[0029]
  Furthermore, according to the present inventionClaim 7Rolling bearingsClaim 6In the rolling bearing described inClaims 1-4It comprises the seal | sticker comprised with the biodegradable resin composition in any one of these.
  Furthermore, according to the present inventionClaim 8The linear motion guide bearing device has a guide rail having a rolling element rolling groove extending in the axial direction on the outer surface, a rolling element rolling groove facing the rolling element rolling groove of the guide rail, and is relatively relative to the axial direction. A slider movably attached to the guide rail; a plurality of rolling elements interposed between the rolling element rolling grooves; and the rolling elements between the rolling element rolling grooves. A linear guide bearing device comprising: a holder for holding at least one of the slider and the holder;Claims 1-4It comprised with the biodegradable resin composition in any one of these.
[0030]
  Furthermore, according to the present inventionClaim 9The temporary shaft of the slider for the linear motion guide bearing device is a temporary shaft for temporarily assembling a slider that is slidably fitted to the guide rail of the linear motion guide bearing device.Claims 1-4It comprised with the biodegradable resin composition in any one of these.
  Since the biodegradable resin composition according to the present invention contains a polyester resin having an aliphatic component that is easily biodegradable, it is naturally decomposed when released into a natural environment such as soil. Therefore, the mechanical parts such as the rolling bearing, the linear motion guide bearing device, and the temporary shaft of the slider for the linear motion guide bearing device according to the present invention are parts made of the biodegradable resin composition when released into the natural environment. Since it is naturally decomposed, it is difficult to adversely affect the natural environment. Moreover, it can be disposed of in the natural environment such as in the soil, and disposal after use becomes easy.
[0031]
The biodegradable resin in the present invention means a resin that meets at least one of the ISO 14851, 14852, and 14855 conditions. The condition of ISO 14851 is “the degree of biodegradation obtained from oxygen consumption in a biodegradability test in an aerobic water system specified in JIS K6950 is 60% or more”. The condition of ISO 14852 is “the degree of biodegradation determined from the amount of carbon dioxide generated in the biodegradability test in the aerobic water system defined in JIS K6951 is 60% or more”. Furthermore, the condition of ISO 14855 is “the degree of biodegradation obtained from the amount of carbon dioxide generated in the biodegradability test in the aerobic composting process defined in JIS K6953 is 70% or more”.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
  [Resin composition containing biodegradable resinReference example]
  Biodegradable resin composition as shown below (Reference example1-4 and Comparative Examples 1-3) were injection-molded into a crown-shaped cage shape as shown in FIG. And the test which evaluates the biodegradability and heat resistance of a biodegradable resin composition was done using this cage.
  First, the biodegradable resin composition used will be described.
[0033]
  Reference exampleOne biodegradable resin composition is polyethylene terephthalate succinate. This is a copolymer of polyethylene terephthalate (aromatic polyester component) and polyethylene succinate (aliphatic polyester component), and the copolymerization ratio (molar ratio) is polyethylene terephthalate: polyethylene succinate = 6: 4.
  Reference example2 andReference example3 is also polyethylene terephthalate succinate, but the copolymerization ratio (molar ratio) isReference example2 is 7: 3,Reference example3 is 8: 2.
[0034]
  Also,Reference example4 is a copolymer of polyethylene terephthalate and poly (polyoxyethylene) succinate (aliphatic polyester component and aliphatic polyether component). The copolymerization ratio (molar ratio) is polyethylene terephthalate: poly (polyoxyethylene) succinate = 7: 3.
  Furthermore, the biodegradable resin composition of Comparative Example 1 is polylactic acid (LACTY9030 manufactured by Shimadzu Corporation), Comparative Example 2 is poly-3-hydroxybutyric acid (Biogreen manufactured by Mitsubishi Gas Chemical Co., Ltd.), and Comparative Example 3 Is polybutylene succinate (Bionore # 1020 manufactured by Showa Polymer Co., Ltd.).
[0035]
Next, a method for a biodegradability test will be described.
The cage is put together with its culture material and "Friends of the Earth" (trade name) into "Friends of the Earth" (trade name), a bio-type garbage decomposition processor manufactured by Takubo Industry Co., Ltd. And biodegraded at 55-60 ° C. Then, the time when the initial weight was 20% or less, or the time when the initial shape was not maintained and was broken apart was defined as the biodegradation completion time, and the biodegradability was evaluated based on the length of the time.
[0036]
The test results are shown in Table 1. The numerical values of the biodegradation completion time in Table 1 are shown as relative values when the biodegradation completion time of Comparative Example 1 is 1.
[0037]
[Table 1]

[0038]
  From the results of Table 1, by introducing an aliphatic polyester (polyethylene succinate) having excellent biodegradability into the molecular structure of an aromatic polyester (polyethylene terephthalate) that has little biodegradability,Reference exampleIt can be seen that the resin compositions 1 to 4 have excellent biodegradability. Also,Reference exampleFrom comparisons 1 to 3, it can be seen that biodegradability improves as the proportion of aliphatic polyester increases.
[0039]
  further,Reference example2 andReference exampleFrom the comparison with 4, it is better to introduce both the aliphatic polyester component and the aliphatic polyether component into the aromatic polyester than to introduce only the aliphatic polyester component into the aromatic polyester. I understand that.
  Next, a heat resistance test method will be described.
  Tensile fracture strength (ring strength) is measured after suspending a cage similar to the above in a thermostatic bath at a predetermined temperature (60, 70, 80, 90, 100, 110, 120, 130 ° C.) for 1000 hours. did. And the highest temperature among the temperatures at which the strength drop from the initial tensile strength is 20% or less was defined as the heat resistant temperature of the biodegradable resin composition.
[0040]
  The test results are also shown in Table 1. From Table 1,Reference exampleIt can be seen that the biodegradable resin compositions 1 to 4 have higher heat resistant temperatures than Comparative Examples 1 to 3.
  [Example of biodegradable resin composition containing reinforcing material]
  Next, tests for evaluating various performances were performed on the biodegradable resin composition containing the reinforcing material.
  First, a biodegradable resin composition containing a reinforcing material as shown in Tables 2 to 5 (Reference Examples 11-19, Examples 1-6,And Comparative Examples 11-17) were produced. The resin and reinforcing material used as raw materials for these biodegradable resin compositions will be described.
[0041]
As a polyester resin having an aliphatic component and an aromatic polyester component in the molecular structure, a polyethylene terephthalate partially modified product (Biomax WUH manufactured by DuPont, hereinafter referred to as a PET modified product) was used. Polybutylene adipate terephthalate (Ecoflex manufactured by BASF Corporation, hereinafter referred to as PBAT) was used as the biodegradable polyester resin having a tensile elongation at break of 50% or more. Furthermore, polylactic acid (LACTY 9030 manufactured by Shimadzu Corporation, hereinafter referred to as PLA) was used as the biodegradable polyhydroxycarboxylic acid.
[0042]
Furthermore, for comparison with the examples, polyethylene succinate (Lunale SE manufactured by Nippon Shokubai Co., Ltd., hereinafter referred to as PESU), which is a biodegradable aliphatic polyester resin, is commonly used as a material for cages for rolling bearings. 66 nylon (Ube nylon grade 2020U manufactured by Ube Industries, Ltd., hereinafter referred to as PA66) was used.
Further, glass fiber (grade FESS-015-0413 manufactured by Fuji Fiber Glass Co., Ltd.) was used as the reinforcing material.
[0043]
These raw materials were blended at a blending ratio as shown in Tables 2 to 5, and mixed using a Henschel mixer. And this mixture is pelletized using a twin screw extruder, and this pellet is put into an injection molding machine, and a JIS No. 1 type test piece and a crown-shaped cage as shown in FIG. And a seal as shown in FIG. 3 were injection molded. The test piece, the cage, and the seal may be manufactured by pelletizing each resin separately and injection molding a pellet blend of each pellet at a predetermined ratio.
[0044]
About the manufactured JIS1 type test piece, biodegradability and heat resistance were evaluated. In addition, the cage was evaluated for injection moldability and assemblability in the operation of assembling the rolling bearing, and further, durability was evaluated using the assembled rolling bearing. The seals were evaluated for injection moldability and ease of assembly in the work of assembling a rolling bearing, and further, creep deformation and grease leakage were evaluated using the assembled rolling bearing.
[0045]
Below, the method of each test is demonstrated.
(1) Biodegradability test
A JIS No. 1 type test piece was embedded in humus soil having a temperature of 60 ° C. and a water content of 30% by mass, and biodegraded, and changes in appearance and weight were investigated. In addition, the temperature and moisture content in humus were kept moderate by installing the humus in which the test piece was embedded in a constant temperature and humidity chamber.
[0046]
And the time when the weight of the test piece became 20% or less of the initial stage, or the time when the initial shape collapsed without being maintained was defined as the biodegradation completion time, and the biodegradability was evaluated by the length of the time.
Test results are shown in Tables 2-5. In addition, the numerical value of the biodegradation completion time in the graphs of Tables 2 to 5 and FIGS. 5 to 8 is shown as a relative value when the biodegradation completion time of Comparative Example 11 is 1.
(2) Heat resistance test
The tensile strength at break was measured after suspending a JIS No. 1 type test piece in a thermostat set at a predetermined temperature (60, 70, 80, 90, 100, 110, 120, 130 ° C.) for 1000 hours. Then, the highest temperature among the temperatures at which the strength decrease from the initial tensile strength at break was within 10% was defined as the heat resistant temperature of the resin composition. A test result is combined with Tables 2-5, and is shown.
(3) Injection moldability test
When the cage and the seal were injection molded, the ease of release from the mold, the deformation and cracking at the time of release, and the warp and shrinkage after molding were evaluated. A test result is combined with Tables 2-5, and is shown. In Tables 2 to 5, a case where no deformation, cracking, warping after molding, or shrinkage occurred at the time of mold release was indicated by ◯, and a case where any of these occurred was indicated by X.
(4) Incorporation test
An inner ring, an outer ring, and rolling elements for a rolling bearing (nominal number 6305, inner diameter 25 mm, outer diameter 62 mm, width 17 mm) were prepared and arranged so that a cage could be incorporated. Then, the cage was assembled using an air cylinder, and the deformation and breakage of the cage due to the incorporation were evaluated.
[0047]
In addition, a rolling bearing (nominal number 6203, inner diameter 16 mm, outer diameter 40 mm, width 12 mm) in which grease (a thickener is lithium soap, a base oil is ester oil, and a biodegradable grease having a blending degree of 250) is enclosed, The seal was assembled using an air cylinder, and the deformation and breakage of the seal due to the assembly were evaluated.
A test result is combined with Tables 2-5, and is shown. In Tables 2 to 5, a case where no deformation or breakage due to incorporation occurred is indicated by a circle.
(5) Durability test
The rolling bearings assembled in the above-described cage mountability test were evaluated for durability using a bearing rotation tester shown in FIG. In FIG. 4, reference numeral 21 denotes a test bearing to be evaluated, and the inner ring of the test bearing rotates with the rotation of the shaft 20 supported by the support bearings 22 and 22. The test conditions are as follows. This test condition is set for the purpose of judging whether or not the rolling bearing according to the present invention can be widely used for general applications.
[0048]
Rotation speed: 9000min^-1
Radial load: 98N
Axial load: 245N
Atmospheric temperature: 80 ° C
Lubricant: Grease
The used grease is a biodegradable grease having a thickening agent of lithium soap, a base oil of ester oil, and a blending degree of 250. The amount of grease filled is usually about 35% of the bearing space volume, but is 10% for the acceleration test.
[0049]
Test results are shown in Tables 2-5. The numerical values shown in the table are 10 times for each type of test bearing._TenThe lifetime is obtained from the Weibull distribution curve. In addition, about the test bearing which does not reach a lifetime even if it performs a rotation test for 500 hours, the test was stopped at that time.
(6) Creep deformation test and grease leakage test
The rolling bearing assembled in the above-described seal incorporation test was placed on a glass plate in a thermostat set at a predetermined temperature (80, 100, 120 ° C.). Then, creep deformation after 1000 hours and leakage of grease were evaluated.
[0050]
Since the fitting fitting portion of the seal is pushed into the fitting groove of the outer ring in an elastically deformed state (see FIG. 3), creep deformation is caused by the ambient temperature and heat generated by the rotation of the bearing, and the fitting groove is inserted into the fitting groove. Fixing force often decreases. In addition, since plastic has a larger linear expansion coefficient than metal, when the temperature rises, the seal expands in the radial direction, and the amount of elastic deformation (clamping force) becomes larger than that at room temperature, so that creep deformation is more likely to occur. When the fixing force is reduced, not only the sealing performance is deteriorated, but also the seal may fall off from the outer ring with a small force.
[0051]
  A test result is combined with Tables 2-5, and is shown. In Tables 2 to 5, the case where the creep deformation and the leakage of the grease are at a level causing no problem in practical use of the rolling bearing is indicated by ◯, and the case where the problem occurs is indicated by an X. .
  Next, the results of the above tests will be described with reference to Tables 2 to 5 and graphs.
  First, the influence of the type of biodegradable resinReference exampleThe results of No. 12 and Comparative Examples 11 and 12 (reinforcing material content is 20% by mass) are compared and discussed.
[0052]
[Table 2]

[0053]
  Using a PET modified productReference exampleNo. 12 exhibited excellent biodegradability and high heat resistance, and the injection moldability and incorporation of the cage and seal were also good. Further, in the durability test, all ten test bearings did not reach the end of their service life even after 500 hours of rotation test. The cage after the end of the rotation test showed no abnormalities such as wear, breakage, deformation, etc. and could be continuously operated. Furthermore, the creep deformation of the seal and the leakage of the grease were at a level with no practical problem.
[0054]
On the other hand, although the comparative example 11 using PESU was excellent in biodegradability, its heat resistance was quite low. In addition, although the cage and seal were excellent in injection moldability and incorporation, in the durability test, the cage was thermally deformed immediately after the start of the test, and the test could not be continued. Further, in the creep deformation test of the seal, the test was stopped because the entire seal was greatly deformed after 24 hours of the test and a large amount of grease leaked.
[0055]
  In Comparative Example 12 using PA66, the heat resistance, injection moldability, assemblability, durability, creep deformation, and grease leakage were good, but in the biodegradability test, the weight changes after 4000 hours. In addition, almost no change in shape was observed, and biodegradation did not proceed.
  Next, regarding the influence of the content of the reinforcing material in the biodegradable resin composition, Table 2 (Reference example11 to 15 and Comparative Examples 13 and 14) and the graph of FIG. In this graph, the biodegradation completion time is indicated by a circle, L_TenThe service life is indicated by ●.
[0056]
  As can be seen from Table 2,Reference exampleNos. 11 to 15 showed excellent biodegradability and high heat resistance, and the injection moldability and incorporation property of the cage and the seal were also good. The glass fiber content is 49% by massReference exampleOnly 15 is the otherReference exampleAlthough it took some time to complete biodegradation as compared with 11-14, the biodegradability is at a level that causes no problem in practical use.
  In the durability test, all ten test bearings did not reach the end of their service life even after 500 hours of rotation test. The cage after the end of the rotation test showed no abnormalities such as wear, breakage, deformation, etc. and could be continuously operated.
[0057]
  further,Reference exampleIn Nos. 11 to 15, the creep deformation of the seal and the leakage of grease were at a level with no practical problems.Reference exampleOnly 11Reference exampleThe creep deformation was slightly larger than 12-15, and the fixing force of the seal decreased compared to the initial level, but it was at a level causing no practical problems. However, since the seal may be exposed to a higher temperature than the creep deformation test, the glass fiber content is more preferably 20% by mass or more.
[0058]
On the other hand, in Comparative Example 13 containing no glass fiber (resin only), the strength of the cage was insufficient, and in the durability test, the cage was deformed after about 20 hours from the start of the test, and the test was continued. I couldn't. In addition, the seal was damaged when the seal was assembled into the rolling bearing.
Further, Comparative Example 14 in which the glass fiber content was as large as 60% by mass had good biodegradability and heat resistance, but the resin composition had insufficient melt fluidity, so that the injection molding method was used. Therefore, it was difficult to mold the cage and the seal.
[0059]
  Next, regarding the influence of the content of PLA (biodegradable polyhydroxycarboxylic acid) in the biodegradable resin composition, Table 3 (Reference example11 and 16 to 19 and Comparative Example 15) and the graph of FIG. In this graph, the biodegradation completion time is indicated by a circle, L_TenThe service life is indicated by ● and the heat-resistant temperature is indicated by △.
[0060]
[Table 3]

[0061]
  As can be seen from Table 3,Reference exampleNos. 16 to 19 all showed excellent biodegradability and high heat resistance, and the injection moldability and incorporation property of the cage and the seal were also good. Further, in the durability test, all ten test bearings did not reach the end of their service life even after 500 hours of rotation test. The cage after the end of the rotation test showed no abnormalities such as wear, breakage, deformation, etc. and could be continuously operated. Furthermore, the creep deformation of the seal and the leakage of grease were at a level causing no practical problem.
[0062]
  PLA content is 40% by massReference exampleOnly 19 is the otherReference exampleAlthough the heat resistant temperature was slightly lower than those of 11, 16 to 18, there was no particular problem in the durability test. In addition, the creep deformation of the seal was slightly large (the fixing force of the seal decreased compared to the initial),Reference exampleThere was no practical problem at the same level as 11.
  However, considering the results of this heat resistance test and the result of the creep deformation test, when higher heat resistance is required than this durability test, the content of PLA should be 30% by mass or less. It is considered preferable.
[0063]
  On the other hand, when the PLA content is further increased, the heat resistance tends to be further reduced. Comparative Example 15 having a higher PLA content has a lower heat-resistant temperature, and L_TenLifespan was also low. Furthermore, the creep deformation of the seal is large and the leakage of grease is large, which causes practical problems.
  Although not shown in Table 3, in the case of a biodegradable resin composition containing PLA (Reference example16-19 and Comparative Example 15) were able to shorten the cooling time of the resin injected into the mold when the cage was manufactured by the injection molding method.
[0064]
  Next, regarding the influence of the content of PBAT (biodegradable polyester resin having a tensile elongation at break of 50% or more) in the biodegradable resin composition, Table 4 (Reference Example 12, Examples 1, 2,The comparison will be made with reference to Comparative Example 16) and the graph of FIG. Also in this graph, the biodegradation completion time is indicated by a circle, L_TenThe service life is indicated by ● and the heat-resistant temperature is indicated by △.
[0065]
[Table 4]

[0066]
  As can be seen from Table 4,Examples 1 and 2All exhibited excellent biodegradability and high heat resistance, and the injection moldability and incorporation of the cage and seal were also good. Further, in the durability test, all ten test bearings did not reach the end of their service life even after 500 hours of rotation test. The cage after the end of the rotation test showed no abnormalities such as wear, breakage, deformation, etc. and could be continuously operated. Furthermore, the creep deformation of the seal and the leakage of grease were at a level causing no practical problem.
[0067]
  The content of PBAT is 20% by massExample 2Only the otherReference Example 12 and Example 1Although the heat-resistant temperature was slightly lower than that of No. 1, there was no particular problem in the durability test. However, considering the results of this heat resistance test, it is considered that the PBAT content is preferably 10% by mass or less when higher heat resistance is required than the durability test. On the other hand, when the content of PBAT is further increased, heat resistance and mechanical strength tend to be further reduced. Comparative Example 16 having a higher content of PBAT has a lower heat-resistant temperature,_TenLifespan was also low. Furthermore, the creep deformation of the seal is large and the leakage of grease is large, which causes practical problems.
[0068]
  Although not shown in Table 4, in the case of a biodegradable resin composition containing PBAT (Examples 1 and 2Since Comparative Example 16) has excellent toughness, it was possible to prevent damage to the cage when released from the mold, even with a cage having a large undercut portion. Moreover, it was effective in preventing the damage of the seal | sticker at the time of releasing from a metal mold | die, and preventing the damage of the seal | sticker at the time of incorporating in a rolling bearing.
  In particular, the effect of preventing breakage when incorporated in a rolling bearing is great, and a seal can be incorporated without difficulty in a non-standard rolling bearing in which the minimum diameter portion (see FIG. 3) of the fitting groove of the outer ring is small. . When incorporating a plastic seal into a rolling bearing, use the elasticity of the seal so that the fitting part of the seal gets over the smallest diameter part of the fitting groove of the outer ring, Since it fits into the fitting groove, it is difficult to incorporate the seal if the minimum diameter portion is small.
[0069]
  Next, regarding the influence of the total content of PLA and PBAT in the biodegradable resin composition that occurs when both PLA and PBAT are used, Table 5 (Reference Example 13, Examples 3-6,The following discussion will be made with reference to Comparative Example 17) and the graph of FIG. Also in this graph, the biodegradation completion time is indicated by a circle, L_TenThe service life is indicated by ● and the heat-resistant temperature is indicated by △.
[0070]
[Table 5]

[0071]
  As can be seen from Table 5,Examples 3-6All exhibited excellent biodegradability and high heat resistance, and the injection moldability and incorporation of the cage and seal were also good. Further, in the durability test, all ten test bearings did not reach the end of their service life even after 500 hours of rotation test. The cage after the end of the rotation test showed no abnormalities such as wear, breakage, deformation, etc. and could be continuously operated. Furthermore, the creep deformation of the seal and the leakage of grease were at a level causing no practical problem.
[0072]
  The total content of PLA and PBAT is larger than the content of PET modified productsExample 6Only the otherReference Example 13 and Examples 3-5Although the heat-resistant temperature was slightly lower than that of No. 1, there was no particular problem in the durability test. However, considering the results of this heat resistance test, when higher heat resistance is required than in this durability test, the total content of PLA and PBAT should be less than the content of the PET modified product. It is considered preferable.
[0073]
  On the other hand, when the total content of PLA and PBAT is further increased and the content of the PET modified product is further decreased, the heat resistance tends to be further decreased. Such Comparative Example 17 has a lower heat-resistant temperature, and L_TenLifespan was also low. Furthermore, in the creep deformation test of the seal, the test was stopped because the entire seal was greatly deformed after 100 hours of the test and a large amount of grease leaked.
  Although not shown in Table 5, in the case of a biodegradable resin composition containing both PLA and PBAT (Examples 3-6It was confirmed that Comparative Example 17) had both the effect of shortening the cooling time of the resin injected into the mold and the effect of preventing the cage from being damaged when released from the mold. Moreover, the effect was also recognized in preventing the damage of the seal at the time of releasing from a metal mold | die, and preventing the damage of the seal at the time of incorporating in a rolling bearing.
[0074]
Next, an embodiment of a machine part according to the present invention will be described in detail with reference to the drawings.
[First embodiment]
FIG. 1 is a longitudinal sectional view showing a configuration of a rolling bearing which is an embodiment of a mechanical component according to the present invention.
The deep groove ball bearing in FIG. 1 includes an inner ring 11, an outer ring 12, a plurality of balls 13 that are rotatably disposed between the both wheels 11, 12, and a plurality of balls 13 between the both wheels 11, 12. A crown-shaped cage 14 (see FIG. 2) that holds the deep groove ball bearings at equal intervals in the circumferential direction, and a contact-type seal 15 interposed between the two wheels 11 and 12 are provided.
[0075]
The seal 15 has an annular shape, an attachment fitting portion 15a (outer peripheral edge portion) for fitting in a seal groove 12a provided on the inner peripheral surface of the outer ring 12 (or the outer peripheral surface of the inner ring 11), and the inner ring 11 It comprises a lip portion 15b that is in sliding contact with the outer peripheral surface, and a connecting portion 15c that connects the attachment fitting portion 15a and the lip portion 15b. Such a seal 15 is attached to the inner peripheral surface of both ends of the outer ring 12 and covers an opening portion between the inner peripheral surface of the outer ring 12 and the outer peripheral surface of the inner ring 11. In addition, entry of foreign matter from the outside and leakage of grease from the inside are prevented.
[0076]
  The seal 15 may be a non-contact type or a type having a metal or resin cored bar. Further, the overall shape of the seal 15 and the detailed shape of the lip portion 15b and the like are not limited to those shown in FIG. 1, and various shapes such as the seal shown in FIG. 3 can be adopted. Needless to say. Furthermore, the form of the seal groove 12a of the outer ring 12 is not limited to that shown in FIG.
  The cage 14 and the seal 15 of such a deep groove ball bearing are made of a biodegradable resin composition. That is, the retainer 14 isReference example2 is composed of a resin composition in which 70% by mass of the biodegradable resin used in 2 and 30% by mass of calcium carbonate whisker (argonite) as a filler are mixed. As the calcium carbonate whisker, a brand name whiscal manufactured by Maruo Calcium Co., Ltd. was used.
[0077]
  In addition, the seal 15 isReference example4 is composed of a resin composition in which 85% by mass of the biodegradable resin used in 4 and 15% by mass of calcium carbonate whisker (argonite) as a filler are mixed. The calcium carbonate whisker is the same as described above.
  The inner ring 11, the outer ring 12, and the ball 13 are made of bearing steel.
  Since these resin compositions have excellent heat resistance and mechanical properties are less likely to deteriorate over time, the above deep groove ball bearings partially composed of the resin compositions are used as rolling bearings. It has sufficient performance. Moreover, even if this deep groove ball bearing is released into the natural environment such as the soil, the portion composed of the biodegradable resin composition is naturally decomposed, and therefore, it is difficult to adversely affect the natural environment.
[0078]
  In addition, the inner ring 11, the outer ring 12, and the ball 13 can also be formed of a biodegradable resin composition. For example,Reference example1 can be composed of a biodegradable resin composition comprising 60% by mass of the biodegradable resin used in No. 1 and 40% by mass of the aforementioned calcium carbonate whisker as a filler (for the cage 14 and the seal 15). The biodegradable resin composition is the same as described above).
  Since such a deep groove ball bearing is entirely composed of a biodegradable resin composition, the whole is naturally decomposed when released into a natural environment such as soil. Therefore, the adverse effect on the natural environment is extremely small. Since such a deep groove ball bearing can be disposed of in a natural environment such as in the soil, disposal after use is easy.
[0079]
In the present embodiment, a deep groove ball bearing has been described as an example of a rolling bearing, but the present invention can be applied to various types of rolling bearings. For example, radial ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, self-aligning roller bearings and other radial type rolling bearings, and thrust type ball bearings and thrust roller bearings such as thrust roller bearings.
[Second Embodiment]
FIG. 9 is a perspective view showing a configuration of a linear motion guide bearing device which is an embodiment of the mechanical component according to the present invention. FIG. 10 is a front view of the linear guide bearing device of FIG. 9 viewed from the axial direction.
[0080]
On a rectangular guide rail 31, a slider 32 having a substantially U-shaped cross section is straddled so as to be relatively movable in the axial direction. The slider 32 is configured by detachably fixing end caps 32B and 32B to both end portions of the slider body 32A in the axial direction.
Further, rolling element rolling grooves 33A and 33A, which are concave grooves having a substantially circular arc shape in cross section, are formed in the axial direction at the ridge line portion where the upper surface 31a of the guide rail 31 intersects with both side surfaces 31b and 31b. . Furthermore, rolling element rolling grooves 33B and 33B, which are concave grooves having a substantially semicircular cross section, are formed in the axial direction at intermediate positions between both side surfaces 31b and 31b of the guide rail 31. In addition, a clearance groove 33a for a retainer 36 to be described later that prevents the rolling element 35 from dropping off is formed in the axial direction at the groove bottom of the rolling element rolling groove 33B.
[0081]
On the other hand, a load rolling element rolling groove 41 having a substantially semicircular cross section facing the rolling element rolling groove 33A of the guide rail 31 is formed in the corner portion inside the sleeves 34, 34 of the main body 32A of the slider 32. In addition, a load rolling element rolling groove 42 having a substantially semicircular cross section facing the rolling element rolling groove 33 </ b> B of the guide rail 31 is formed at the center of the inner side surfaces of the sleeve portions 34, 34.
Then, the rolling element rolling groove 33A of the guide rail 31 and the load rolling element rolling groove 41 of the slider 32 constitute a load rolling element rolling path 43, and the rolling element rolling groove 33B of the guide rail 31 and the slider. A load rolling element rolling path 44 is constituted by the 32 load rolling element rolling grooves 42.
[0082]
Further, a rolling element return path 45 comprising a through hole having a circular cross section extending in the axial direction parallel to the load rolling element rolling path 43 is formed in the upper wall thickness of the sleeve section 34 of the slider main body 32A. In the wall thickness, a rolling element return path 46 formed of a similar axially extending through hole parallel to the load rolling element rolling path 44 is formed.
The end cap 32B is an injection-molded product made of a resin material and has a substantially U-shaped cross section. As shown in FIG. 11, a semicircular upper concave portion 51 and a lower concave portion 52 that are inclined obliquely are formed above and below the sleeve portions 34, 34 on the joint surface (back surface) with the slider body 32 </ b> A. In addition to being formed, a semi-cylindrical concave groove 53 is provided across the center of both semicircular concave portions 51 and 52.
[0083]
A semi-cylindrical return guide 55 (see FIG. 12) obtained by injection molding of a resin material is fitted into the semi-cylindrical concave groove 53. FIG. 13 is a perspective view of the end cap 32B to which the return guide 55 is attached. In the center of the outer diameter surface of the return guide 55, a concave groove 56 having a circular arc cross section serving as the guide surface of the rolling element 35 is formed in a semicircular shape, and the concave portion 57 on the inner diameter side of the return guide 55 is lubricated. A through hole 57 </ b> A that is an agent passage and extends from the concave portion 57 to the concave groove 56 on the outer diameter side is formed as an oil supply hole.
[0084]
By incorporating such a return guide 55 in the semi-cylindrical concave groove 53, a semi-doughnut-shaped curved path 58 having a circular cross section is formed on the back surface of the end cap 32B (see FIG. 14). When this end cap 32B is attached to the slider main body 32A, the load rolling element rolling path 44 and the rolling element return path 46 of the slider main body 32A communicate with each other through the curved path 58. And the upper load rolling element rolling path 43 and rolling element return path 45 are similarly communicated.
[0085]
A large number of rolling elements 35 are slidably loaded in the rolling element infinite circulation path constituted by the above-described load rolling element rolling paths 43 and 44, rolling element return paths 45 and 46, and a curved path 58.
When the slider 32 moves on the guide rail 31, the rolling element 35 moves in the moving direction of the slider 32 at a speed slower than the slider 32 while rolling in the load rolling element rolling paths 43 and 44, and the curved path on one end side. Circulation returns to the load rolling element rolling paths 43 and 44 by making a U-turn at 58 and moving while rolling the rolling element return paths 45 and 46 in the opposite direction, and making a reverse U turn at the curved path 58 on the other end side. repeat.
[0086]
In the end cap 32B, a rolling body scooping protrusion 59 that protrudes in a semicircular shape is formed at the inner end of the curved path 58 that guides the rolling element 35, and the acute end of the rolling end of the guide rail 31 rolls. The moving body rolling grooves 33A and 33B are arranged close to the groove bottoms. The lower rolling element scooping projection 59 is provided with a mounting groove 59a and a mounting hole 59b of the retainer 36, which will be described later.
Further, the lubricant injected from the oil supply nipple 37 on the front side of the end cap 32B passes through the oil supply groove 60 on the back surface of the end cap 32B, passes through the recess 57 on the inner diameter side of the return guide 55, passes through the through hole 57A, and enters the curved path 58. To be sent to. Further, a mounting hole 61a for a retainer 61, which will be described later, is formed below the oil supply groove 60 on the back surface of the end cap 32B.
[0087]
The rolling elements 35 respectively loaded in the upper load rolling element rolling path 43 and the lower load rolling element rolling path 44 of the slider 32 fall off in a state where the slider 32 is not assembled to the guide rail 31. Therefore, in order to prevent this, a cage made of an injection molded resin material is used.
The rolling element falling-off prevention cage 36 in the lower-stage loaded rolling element rolling path 44 is a cage having a square cross section, and both ends in the longitudinal direction thereof are curved like a bow to smoothly guide the rolling element 35. The terminal has a mounting portion. The mounting is performed by inserting the mounting portion into a cage mounting hole 59b formed in the rolling member scooping projection 59 of the end cap 32B. In a state where the slider 32 is assembled to the guide rail 31, the retainer 36 is accommodated in the retainer escape groove 33 a of the guide rail 31 and does not interfere with the guide rail 31.
[0088]
On the other hand, the rolling element falling prevention cage 61 in the upper load rolling element rolling path 43 has a substantially rectangular frame shape as shown in FIG. The retainer 61 has a substantially 1/4 arc-shaped rolling element retaining surface 63 formed on the outer edge in the longitudinal direction of the frame 62, and a locking projection 64 projects from the front and rear ends. The mounting is performed by inserting the locking projection 64 into the mounting hole 61a on the back surface of the end cap 32B. As a result, the retainer 61 is supported by the end cap 32B and accommodated in a space between the upper surface 31a of the guide rail 31 and the inner surface of the slider body 32A facing the guide rail 31, and the rolling element 35 and the rolling element holding surface 63 are loaded. It is sandwiched and held by the groove surface of the moving body rolling groove 41.
[0089]
  A part of such a linear motion guide bearing device is made of a resin material as described above.Reference example1 is a biodegradable resin composition comprising 60% by mass of the biodegradable resin used in No. 1 and 40% by mass of the aforementioned calcium carbonate whisker as a filler. In the conventional linear motion guide bearing device, polyacetal resin has been used. Since these resin compositions have excellent heat resistance and mechanical properties are less likely to deteriorate over time, the linear motion guide bearing device partially composed of the resin composition is not suitable for rolling. It has sufficient performance as a moving device. Moreover, even if this linear motion guide bearing device is released into the natural environment such as in the soil, since the portion composed of the biodegradable resin composition is naturally decomposed, it is difficult to adversely affect the natural environment.
[0090]
[Third embodiment]
FIG. 16 is a perspective view showing a configuration of a temporary shaft of a slider for a linear guide bearing device that is an embodiment of a mechanical component according to the present invention. FIG. 17 is a perspective view showing the temporary shaft in a state where the slider is assembled.
The temporary shaft 101 is formed in substantially the same shape as a guide rail for a linear motion guide bearing device. That is, the cross-sectional shape broken by a plane perpendicular to the axial direction of the temporary shaft 101 is substantially the same as that of the guide rail.
[0091]
Then, a concave groove 102A having a substantially arc-shaped cross section corresponding to a rolling element rolling groove is formed in the axial direction at a ridge line portion where the upper surface 101a and both side surfaces 101b of the angular temporary shaft 101 intersect, A concave groove 102B having a substantially semicircular cross section corresponding to the rolling element rolling groove is formed in the axial direction at an intermediate position between both side surfaces 101b of the temporary shaft 101. Further, a clearance groove 103 for the ball cage is formed in the groove bottom of the concave groove 102B formed at the intermediate position of the both side surfaces 101b, like the guide rail.
[0092]
However, unlike the guide rail, the temporary shaft 101 is for temporarily assembling the slider 105. Therefore, as shown in FIGS. 16 and 17, the axial length of the temporary shaft 101 is the length of the slider 105 in the axial direction. Slightly longer than that is sufficient. In addition, since the upper surface 101a of the temporary shaft 101 does not need to be planar in terms of function, a concave meat blank 104 is provided in order to improve the dimensional accuracy of the temporary shaft 101. It should be noted that a reinforcing plate 104 a for reinforcing the meat paste 104 is provided inside the meat paste 104.
[0093]
  When the temporary shaft 101 with the slider 105 assembled is attached to the end of the guide rail so as to be continuous, and the slider 105 is slid from the temporary shaft 101 toward the guide rail, the slider 105 assembled with the temporary shaft 101 is removed. It can be moved to the guide rail.
  Such a temporary shaft 101 is, for example,Reference example1 is produced by injection molding a biodegradable resin composition comprising 90% by mass of the biodegradable resin used in No. 1 and 10% by mass of the aforementioned calcium carbonate whisker as a filler.
[0094]
  Therefore, if the temporary shaft 101 after the slider 105 is moved to the guide rail is buried in the soil as waste, it is naturally biodegraded, so that it does not adversely affect the natural environment, and causes of waste problems It is hard to become.
  In addition, said 1st-3rd embodiment shows an example of this invention, and this invention is not limited to said each embodiment.
  For example, the type of biodegradable resin used in the biodegradable resin composition, the type of filler, the type of additive, and the blending ratio thereof are not limited to the present embodiment. It is possible to select appropriately according to the shape, purpose of use and the like. For example,Tables 4 and 5It is good also as a structure of the Example described in this.
[0095]
In the present embodiment, ball bearings, linear motion guide bearing devices, and temporary shafts of linear motion guide bearing device sliders have been described as examples of mechanical components. However, the present invention is not limited to various other mechanical components. Can be applied. For example, a rolling device such as a ball screw.
[0096]
【The invention's effect】
As described above, the biodegradable resin composition according to the present invention is excellent in heat resistance and hardly deteriorates over time in mechanical properties.
In addition, mechanical parts such as rolling bearings according to the present invention have excellent heat resistance, and mechanical properties are unlikely to deteriorate over time. Therefore, it can be used in various industrial fields. Furthermore, since mechanical parts such as rolling bearings according to the present invention have excellent biodegradability, they are naturally decomposed when released into the natural environment such as the soil, and do not adversely affect the natural environment. Therefore, it can be disposed of in the natural environment such as in the soil, and disposal after use becomes easy.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing the structure of a deep groove ball bearing which is an embodiment of a mechanical component according to the present invention.
2 is a perspective view showing a crown-shaped cage used in the deep groove ball bearing of FIG. 1. FIG.
FIG. 3 is a cross-sectional view of a seal and a rolling bearing for explaining the configuration of the rolling bearing seal according to the present invention.
FIG. 4 is a cross-sectional view showing a configuration of a bearing rotation tester.
FIG. 5 shows glass fiber content, biodegradation completion time, and L in the biodegradable resin composition._TenIt is a graph which shows the correlation with a lifetime.
FIG. 6: PLA content in biodegradable resin composition, biodegradation completion time, L_TenIt is a graph which shows the correlation with a lifetime and heat-resistant temperature.
FIG. 7: Content of PBAT in biodegradable resin composition and biodegradation completion time, L_TenIt is a graph which shows the correlation with a lifetime and heat-resistant temperature.
FIG. 8 shows the total content of PLA and PBAT in the biodegradable resin composition, biodegradation completion time, L_TenIt is a graph which shows the correlation with a lifetime and heat-resistant temperature.
FIG. 9 is a perspective view showing a configuration of a linear guide bearing device which is another embodiment of the mechanical component according to the present invention.
10 is a front view of the linear motion guide bearing device of FIG. 9. FIG.
FIG. 11 is a view showing the back surface of the end cap with the return guide omitted.
FIG. 12 is a front view of a return guide.
FIG. 13 is a perspective view of the end cap with the return guide attached.
14 is a partial cross-sectional view taken along line AA in the vicinity of the end cap of FIG.
FIG. 15 is a perspective view of a cage.
FIG. 16 is a perspective view showing a temporary shaft of a slider for a linear motion guide bearing device which is another embodiment of the mechanical component according to the present invention.
FIG. 17 is a perspective view showing a temporary shaft in a state where a slider is assembled.
[Explanation of symbols]
11 Inner ring
12 Outer ring
13 balls
14 Cage
15 seal
32B end cap
36 Cage
55 Return Guide
61 Cage
101 Temporary axis

Claims (9)

In the resin composition containing a biodegradable resin, the biodegradable resin comprises at least one of an aliphatic polyester component and an aliphatic polyether component obtained by polycondensation of an aliphatic dibasic acid and an aliphatic diol. A polyester resin having an aliphatic component and an aromatic polyester component in the molecular structure ,
At least a part of the polyester resin is a biodegradable polyester resin having a tensile elongation at break of 50% or more, and the content of the biodegradable polyester resin having a tensile elongation at break of 50% or more is determined based on the total resin composition. A biodegradable resin composition characterized by being 20% by mass or less .   2. The amount ratio of the aromatic polyester component and the aliphatic component of the polyester resin is 19: 1 to 5: 5 in terms of a molar ratio of repeating units of the respective components. Biodegradable resin composition.   The biodegradable resin composition according to claim 1 or 2, further comprising a reinforcing material.   The content of the polyester resin is 30% by mass or more and 90% by mass or less of the entire resin composition, and the content of the reinforcing material is 10% by mass or more and less than 50% by mass of the entire resin composition. Item 4. The biodegradable resin composition according to Item 3. A machine part comprising the biodegradable resin composition according to any one of claims 1 to 4. In a rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements arranged to roll between the two wheels, and a cage for holding the rolling element between the two wheels,
A rolling bearing characterized in that at least the cage of the inner ring, the outer ring, the rolling element, and the cage is made of the biodegradable resin composition according to any one of claims 1 to 4. The rolling bearing according to claim 6, comprising a seal composed of the biodegradable resin composition according to claim 1. A guide rail having a rolling element rolling groove extending in the axial direction on the outer surface, a rolling element rolling groove facing the rolling element rolling groove of the guide rail, and attached to the guide rail so as to be relatively movable in the axial direction A plurality of rolling elements interposed between the rolling element rolling grooves and the rolling element rolling grooves, and a cage for holding the rolling elements between the rolling element rolling grooves. In the linear motion guide bearing device provided,
A linear motion guide bearing device, wherein one or both of at least a part of the slider and the cage are made of the biodegradable resin composition according to any one of claims 1 to 4. A temporary shaft for temporarily assembling a slider that is slidably fitted to a guide rail of a linear motion guide bearing device, comprising a biodegradable resin composition according to any one of claims 1 to 4. Temporary shaft of slider for dynamic guide bearing device.

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