JP2004180780A

JP2004180780A - Washing piece for car washing brush

Info

Publication number: JP2004180780A
Application number: JP2002348824A
Authority: JP
Inventors: Naoki Hashimoto; 直樹橋本
Original assignee: Inoue MTP KK; Inoac Corp; Inoac Elastomer Co Ltd
Current assignee: Inoac Corp; Inoac Elastomer Co Ltd
Priority date: 2002-11-29
Filing date: 2002-11-29
Publication date: 2004-07-02
Anticipated expiration: 2022-11-29
Also published as: JP4069292B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing piece wherein a substance containing a linear low density polyethylene resin for which an α-olefin is copolymerized using a metallocene catalyst is used as the material for the washing piece constituting a car washing brush, thus, the physical property values for various kinds of mechanical strengths such as hardness, tensile strength and tearing strength of an obtained foamed body are controlled, and which can be suitably used for the car washing brush, and also does not damage a car body, and in addition, can perform a sure washing while having a good durability. <P>SOLUTION: Numerous flexible washing pieces 12 constituting the car washing brush are constituted of the foamed body of the resin containing the linear low density polyethylene resin for which the α-olefin is copolymerized using the metallocene catalyst. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、洗車ブラシに好適に使用されて、自動車の塗装や外装品を損傷することなく洗浄可能であり、しかも低温での柔軟性および耐薬品性に優れると共に、業務用用途等の過酷な繰り返し使用に対応した洗浄片に関するものである。
【０００２】
【従来の技術】
一般にガソリンスタンド等に設置されている自動洗車機は、図１に示す如く、制御下に回転可能な回転軸１４の周りに多数の柔軟な洗浄片１２を植設した洗車ブラシ１０を備え、該洗車ブラシ１０を回転させることで洗浄片１２と被洗浄物である車体とを接触させ（図１（ｂ）参照）、これに洗剤を噴射させて車体の表面の洗浄を行なうものである。
【０００３】
これまで前記洗浄片１２として、各種の布やナイロン等を材質とするものが一般に使用されていたが、これらの材質は以下の問題を内在していた。
▲１▼材質が布の場合
前記洗浄片の材質として各種の布が使用した場合、これは柔軟性が高く硬度が低いため、車体表面等に該洗浄による擦り傷等を生ずることは殆どない。しかし布は吸収した水分を保持し易いので、冬季や寒冷地では布中に保持した水分が凍結して柔軟性を低下させる難点がある。またこのように凍結した状態で洗浄を強行すると、自動車に擦り傷を与えるだけでなく、例えば車体を凹ませたり、ガラスを破損する等の重大なダメージに至る。
▲２▼材質がナイロンの場合
前記洗浄片の材質としてナイロンを使用すると、ナイロンは吸水性が殆どないため前述のような寒冷地での凍結等による欠点は回避し得る。しかしナイロンは一般的に硬度が高いので、洗浄中に自動車に擦りを付けてしまう欠点が挙げられる。
【０００４】
そこで前述の各問題点に鑑み、硬度が低く、しかも吸水性を殆ど発現しないエチレン−酢酸ビニル（以下ＥＶＡと云う）樹脂の発泡体を材質とする洗浄片の使用が提案されている。前記ＥＶＡ樹脂は、材質的に非常に柔軟であり、また発泡体とした際に内部の気泡がそれぞれ独立していて連泡率を小さくし得る特徴を有する。従って前述の如く、低い硬度および低い吸水率を発現させ得る。しかし、前記ＥＶＡ樹脂発泡体を洗浄片１２とした洗車ブラシ１０は、その摩擦係数が高いために、実際の使用に当たっては、該洗浄片１２が洗浄回転中に自動車の突起部、例えば外部アンテナ、ミラーその他の外装品に絡み付いてしまう難点がある。このような状況下で洗車ブラシ１０での洗浄を続けると、前記洗浄片１２が絡み付いたアンテナ等の部分が損壊してしまう等の問題が指摘される。
【０００５】
前述したＥＶＡ樹脂発泡体の絡み付きを原因とする自動車外装品の損壊を防止する手段として、該外装品が損壊する程度の応力がかかった際に該ＥＶＡ樹脂発泡体自身の構造を破壊することで、該外装品の損壊を回避する方法が考えられる。この方法は前記ＥＶＡ樹脂発泡体の強度を制御することで可能であり、この強度の制御手段として、該発泡体の架橋度の調整、すなわち分子間結合の度合いの調整が考えられ、該強度を減少させるには該架橋度を小さくすればよい。しかし前記架橋度は、同時に発泡体の発泡に際して最も重要な要素の一つであり、該架橋度が小さくなるのに伴って、発泡体の粘度が低下してしまい安定な発泡体が得られなくなってしまう欠点が指摘される。
【０００６】
【発明が解決しようとする課題】
この問題を解決するため、前記洗浄片１２の材質の主原料として、例えばエチレン−エチルアクリレート（以下、ＥＥＡと云う）樹脂等のポリオレフィン系樹脂を採用することが考えられる。前記ポリオレフィン系樹脂を採用することで、柔軟性、吸水性および引張強度等の各物性値を所定の範囲内とした洗浄片１２を製造し得る。しかし、前記ＥＥＡ樹脂はエチルアクリレート基（前記ＥＶＡ樹脂では酢酸ビニル基）といった短鎖分岐を数多く持っており柔軟性には優れている一方、引張強度および引裂強度といった機械的強度が低く、例えば業務用として実際使用される際の数千台に及ぶ洗車作業に対する耐久性が充分でなく、前記洗浄片１２が断裂や摩耗を起こしてしまう問題を内在している。
【０００７】
この問題は、前記ＥＥＡ樹脂に代表されるポリオレフィン樹脂がチーグラ・ナッター触媒を利用して作られているため、ラメラ（ポリエチレンの折り畳み結晶）が厚く、該ラメラ間を繋ぐタイ分子の数が少ない構造をとっていることに起因している。具体的には前記タイ分子の数が、前記ＥＥＡ樹脂の引張強度等の機械的物性に大きな影響を与え、該タイ分子の数が少ないと、そこから断裂が容易に発生し、その結果、該機械的物性が悪化してしまうためである。このような樹脂の機械的強度を向上させる手段の一つとして低倍率による発泡化が挙げられるが、この方法の場合、得られるＥＶＡ樹脂発泡体の硬度が高くなり、また柔軟性を失うという他の問題が顕在化してしまう。
【０００８】
【発明の目的】
この発明は、従来の技術に係る洗浄片に内在していた問題に鑑み、これを好適に解決するべく提案されたものであって、洗車ブラシを構成する洗浄片の原料として、メタロセン触媒を用いて、α−オレフィンを共重合した直鎖状低密度ポリエチレン（以下、Ｍｅ−ＬＬＤＰＥと云う）樹脂を含有した物質を使用することで、得られる発泡体の硬度並びに引張強度および引裂強度等の各種機械的強度の物性値を制御し、洗車ブラシに好適に使用可能であり、かつ車体を損傷させることなく、さらに良好な耐久性をもって確実な洗浄を行ない得る洗浄片を提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記課題を克服し、所期の目的を達成するため本発明の洗浄片は、洗車ブラシを構成する多数の柔軟な洗浄片であって、
前記洗浄片は、メタロセン触媒を用いてα−オレフィンを共重合させた直鎖状低密度ポリエチレン樹脂を含む樹脂の発泡体から構成することを特徴とする。
【００１０】
【発明の実施の形態】
次に本発明に係る洗浄片につき、好適な実施例を挙げて、以下説明する。本願の発明者は、メタロセン触媒を用いて、α−オレフィンを共重合した直鎖状低密度ポリエチレン（以下、Ｍｅ−ＬＬＤＰＥと云う）樹脂を含む樹脂を採用し、得られる発泡体の硬度並びに引張強度および引裂強度等の各種機械的強度の物性値を所定の範囲内とすることで、長期間に亘り洗浄に必要な機械的強度等を保持すると共に、車体を損傷させる畏れがなく、洗車ブラシに好適に使用し得る洗浄片が得られることを見出したものである。また好適な実施例に係る洗車ブラシは、その構造が前出した従来技術に係る洗車ブラシ１０と殆ど同一であるので、構成等の詳細な記載は省略し、参照番号も同一のものを使用する。
【００１１】
好適な実施例に係る洗浄片を採用した洗車ブラシ１０は、図１に示す如く、制御下に回転する回転軸１４と、この回転軸１４に植設され、該軸１４の回転時に被洗浄物である車体と接触して洗浄を行ない得る多数の洗浄片１２とからなる。前記洗浄片１４は、前記Ｍｅ−ＬＬＤＰＥ樹脂と、ＥＥＡ樹脂等のボリオレフィン樹脂とを樹脂成分として、これに発泡剤および架橋剤等の所定の副原料を混合・発泡させて得られるＭｅ−ＬＬＤＰＥ樹脂含有発泡体（以下、発泡体と云う）から製造される。
【００１２】
前記Ｍｅ−ＬＬＤＰＥ樹脂は、メタロセン触媒を用いて、α−オレフィンを共重合した直鎖状低密度ポリエチレン（以下、ＬＬＤＰＥと云う）樹脂のことである。前記ＬＬＤＰＥ樹脂は、エチレンと、１−ブテン、１−ヘキセンまたは１−オクテン等のα−オレフィンとの共重合体であり、該共重合によりエチル分岐、ｎ−ブチル分岐またはｎ−ヘキシル分岐等がその構造内に導入された低密度ポリエチレンのことである。前記メタロセン触媒は、別名カミンスキー触媒と呼ばれ、例えば二塩化ジルコノセンとメチルアルミノキサンを組み合わせた構造を有し、エチレンに対して高い重合活性を示し、その活性点が均一（シングルサイト触媒ＳｉｎｇｌｅＳｉｔｅＣａｔａｌｙｓｔｓ（ＳＳＣ））である特徴を有する。そして前記メタロセン触媒は、均一系触媒であるため、ポリマ−の分子構造を精密に設計でき、該ポリマ−の微細分子構造や共重合反応性を自由に制御し得る特徴も有する。
【００１３】
また前記メタロセン触媒の如きＳＳＣは、前記チーグラ・ナッター触媒等に代表される従来の触媒、所謂マルチサイト触媒（ＭｕｌｔｉＳｉｔｅＣａｔａｌｙｓｔｓ（ＭＳＣ））と呼ばれる触媒に較べて分子量分布が狭く、かつ各分子のコモノマー含量がほぼ等しいため、得られるＬＬＤＰＥ樹脂の分子量や、短鎖分岐の濃度の分布が小さく、その結果、構造均一性が高いという点でも優れている。
【００１４】
前述したメタロセン触媒を用いて、α−オレフィンを共重合した直鎖状低密度ポリエチレン樹脂の各種機械的強度が、従来のポリオレフィン径樹脂のそれより高くなるのは以下の理由による。すなわち、前記ラメラの厚みをより薄くできるため、その分ラメラとラメラの間を繋ぐタイ分子の数が相対的に多くできる。従って、前記タイ分子の数が少ない時に比較して、強い引張りまたは引裂きの力を分散させて、その結果、引張強度および引裂強度に優れた物性を発現することになる。
【００１５】
前記Ｍｅ−ＬＬＤＰＥ樹脂の全樹脂成分中における含有量、すなわち後述（［００１６］）する各種ポリオレフィン系樹脂との混合割合は、少なくとも３０重量部以上、好ましくは５０重量部以上に設定される。このような混合割合とすることで、混合されて得られる前記樹脂成分と、発泡剤等のその他副原料との混合・混練容易性が高くなる。そして更に、前記Ｍｅ−ＬＬＤＰＥ樹脂の優れる物理的強度と、ＥＶＡ樹脂やＥＥＡ樹脂等の各種ポリオレフィン系樹脂が有する柔軟性とを併有した好適な発泡体の製造もより容易となる効果を奏する。
【００１６】
前記ポリオレフィン系樹脂としては、エチレンと、メチル、エチル、プロピル、ブチルまたは各アクリル酸アルキルエステル（この際のエステル含有量；４５モル％以内）との共重合体や、これらの２種類以上の混合物が使用される。その他、前述の共重合体または混合物と、アイソタクチックポリプロピレンまたはアタクチックポリプロピレンとの混合物の使用も可能である。なお塩素含有量６０重量％までの塩素化物についても使用可能である。殊に前記ポリオレフィン系樹脂としては、発泡体になった際に従来技術で説明したＥＶＡ樹脂や、該ＥＶＡ樹脂から得られる発泡体とほぼ同等の物性値を備え、低い引張強度を発現するＥＥＡ樹脂が好適である。
【００１７】
前記発泡剤としては、無機または有機発泡剤を制限することはなく使用することができる。具体的には、重炭酸ナトリウム、重炭酸アンモニウム、アゾジカルボンアミド、ジニトロソペンタメチレンテトラミン、ジニトロソテレフタルアミド、アゾビスイソブチロニトリルおよびスルホニルヒドラジド類等が挙げられる。これらの中ではアゾジカルボンアミド、アゾビスイソブチロニトリルおよびスルホニルヒドラジド類が好ましい。発泡剤の配合量は、一般的に前記Ｍｅ−ＬＬＤＰＥ樹脂を含む樹脂１００重量部に対して、３〜３０重量部であり、所望の発泡倍率に応じて設定される。
【００１８】
また発泡状態を制御するために、尿素を主成分とする化合物、酸化亜鉛、酸化鉛等の金属酸化物、各種脂肪酸または各種脂肪酸の金属塩等の発泡助剤を添加してもよい。さらに物性改善のため、必要に応じて充填剤としてのカーボンブラック、炭酸カルシウム、アスベストまたは各種金属酸化物等を混合するようにしてもよい。殊にカーボンブラックまたは炭酸カルシウムがコスト低減に好適である。
【００１９】
前記架橋剤としては、少なくとも前記樹脂成分を構成する前記Ｍｅ−ＬＬＤＰＥ樹脂およびポリオレフィン系樹脂の流動開始温度以上の分解温度を有し、加熱により分解され、遊離ラジカルを発生してポリオレフィン系樹脂の分子間に架橋結合を発生させる有機過酸化物が挙げられる。前記有機過酸化物としては、例えばジクミルパーオキサイド、２，５−ジメチル−２，５−ビス−ターシャリーブチルパーオキシヘキセン、１，３−ビス−ターシャリーパーオキシイソプロピルベンゼン等が使用可能である。
【００２０】
前記洗浄片１２を構成する発泡体が発現すべき物性としては、洗車時に自動車への傷の付き易さの指標となる柔軟性を示す硬度と、使用における充分な洗車機能を発現すると共に、経時変化に対する耐久性を示す引張強度等の機械的強度が挙げられる。殊に前記硬度としては、使用時の回転状態を考慮して２５％圧縮硬さが採用されている。
【００２１】
前記硬度については、該硬度を表す２５％圧縮硬さが、０．２ＭＰａ以下、好ましくは０．１２ＭＰａ以下であることが望まれる。前記２５％圧縮硬さが０．２ＭＰａを越えると、通常の使用に当たって車体に擦り傷等を付けてしまうことが経験的に知られているので注意が必要である。この硬度は、基本的に前記Ｍｅ−ＬＬＤＰＥ樹脂の密度と、前記洗浄片１２を構成する樹脂発泡体の発泡倍率とによって決定される物性値である。
【００２２】
前記Ｍｅ−ＬＬＤＰＥ樹脂においては、その密度が０．８８〜０．９３ｇ／ｃｍ^３、好ましくは０．８７〜０．９１ｇ／ｃｍ^３に設定された物質を使用する。これは前記ＥＶＡ樹脂が酢酸ビニル基の、ＥＥＡ樹脂がエチルアタリレート基の含有量の増加に伴い柔軟性が増すのと同様に、ＬＬＤＰＥは共重合させる短鎖分岐（α−オレフィン）の数の増加により、密度低下が図られて短鎖分岐の数が多くなり、これにより得られるＬＬＤＰＥの結晶形成が阻害され、非晶性、すなわち柔軟性が増すことを利用して硬度を所望の範囲にするためである。そして前記密度が０．８８ｇ／ｃｍ^３未満の場合、硬度を表す２５％圧縮硬さが０．２ＭＰａを越えてしまうことが考えられ、また０．９３ｇ／ｃｍ^３を越える場合、得られるＭｅ−ＬＬＤＰＥ樹脂の融点が高くなってしまい、その結果、該樹脂と発泡剤や架橋剤との混練時における必要温度の増大による各種の弊害、具体的には該発泡剤や架橋剤の混練時における熱分解、各種混練機器の耐熱性向上に係る維持コストおよび使用エネルギー量等のランニングコストの増大等の問題をもたらす。このように制御することで、前述の硬度を達成し得る発泡体の基となる中間材料たる樹脂混練物を得ることができる。
【００２３】
また前記発泡倍率については、８〜１５倍、好ましくは８〜１２倍程度の範囲であれば、前記Ｍｅ−ＬＬＤＰＥ樹脂を含む樹脂混練物を使用した発泡体、すなわち洗浄片１２が前述の値を達成し得る。なお、主原料たる樹脂の種類・混合割合によっては、発泡倍率の設定によって本発明に係る各物性値の範囲をから外れることがあるため注意が必要である。基本的に発泡倍率が高くなるに従って、前記洗浄片１２を構成する発泡体の構造が疎となるため、引張強度等は悪化し、２５％圧縮硬さは良化する。この他、前記発泡体原料中の混合される充填材の量に反して硬度が低下することも知られている。前記発泡倍率は、８倍未満となると硬度が高くなってしまい、１５倍を越えると後述（［００２５］）する引張強度が低下してしまう。この発泡倍率は、前記主原料樹脂に加えられる前述［００１７］した発泡剤等の量によって、容易に設定可能である。
【００２４】
前記引張強度としては、１．３〜２．０ＭＰａ（ＪＩＳＫ６７６７に準拠）の範囲が好適であり、基本的に発泡体構造中の分子間力等、すなわちＭｅ−ＬＬＤＰＥの短鎖分岐数や、前述［００１９］した架橋剤等の使用量によって決定されるものである。引張強度が１．３ＭＰａ未満であっても、通常状態の洗浄には充分使用し得るが、長期間に亘る経時的な使用においては発泡体が断裂してしまい必要な洗浄力が得られなくなってしまう。また２．０ＭＰａを越えると、回転中の洗浄片が自動車のミラー等の外装品に巻き付いた際に、該外装品を損壊させてしまう畏れが高くになり、本発明の洗浄片として採用し得ない。
【００２５】
前記引裂強度としては、４３〜６０Ｎ／ｃｍ（ＪＩＳＫ６７６７に準拠）の範囲が好適である。この数値は、前記引張強度に比例的なものであり、基本的に発泡体構造中の分子間力によって決定されるものである。この引裂強度が４３Ｎ／ｃｍ未満であっても、通常状態の洗浄には充分使用し得るが、長期間に亘る経時的な使用においては発泡体が断裂してしまって必要な洗浄力が得られなくなってしまう。また６３Ｎ／ｃｍを越えると、回転中の洗浄片が自動車のミラー等の外装品に巻き付いた際に、該外装品を損壊させてしまう畏れが高くなり、本発明の洗浄片として採用し得ない。
【００２６】
【製造方法の一例】
以下に本発明に係る洗車ブラシの洗浄片を好適に製造する方法の一例を以下に記載する。前記Ｍｅ−ＬＬＤＰＥ樹脂およびポリオレフィン系樹脂等からなる樹脂成分と、架橋剤、発泡剤、発泡助剤、充填剤および所望の各種副原料等とを、バンバリーミキサー等の従来公知の混練器を用いて充分に混練して樹脂混練物とする。そして前記樹脂混練物を所定の金型等を用いて加圧・加熱下に充填、前記架橋剤および発泡剤を完全に分解した後に減圧状態とすることで一度に膨張させる、所謂一段発泡法や、該金型による一次発泡で得られる一次（中間）発泡体を常圧下にさらに加熱して二次発泡させる、所謂二段発泡法により所望の密度としたＭｅ−ＬＬＤＰＥ樹脂含有発泡体を得る。
【００２７】
前記一段発泡法は、使用する装置および操作等が簡便で、かつ得られる発泡体の強度が二段発泡法に較べて高く発現するものであるので好適に採用されるが、前述の何れの方法であっても本発明に係る好適な洗浄片１２の製造は可能であり、実際には得るべき該洗浄片１２の発泡倍率等の諸物性値により適宜選択される。通常、前記発泡倍率が１０〜１５倍程度の場合は、前記一段発泡法の採用が好適である。
【００２８】
なお、ここでは化学的発泡法および押出成形を採用して前述の所要形状に成形したが、所定の物性を満足すると共に、所要形状への成形が可能であれば、如何なる公知の発泡法や成形法であっても採用は可能である。殊に樹脂成分内に、前述（［００１５］）した如く、Ｍｅ−ＬＬＤＰＥ樹脂を３０重量部以上、好適には５０重量部以上混合させることで、全原料の混合・混練は容易に実施可能となる。
【００２９】
【実験例】
以下に本発明に係る洗車ブラシに好適に採用し得る洗浄片の実験例を示す。なお、本実験例では樹脂成分を構成するＭｅ−ＬＬＤＰＥ樹脂以外の樹脂として、ＥＥＡ樹脂を使用した例を示すが、殊にこの実験例に記載された内容に限定されるものではない。
【００３０】
（実験１）Ｍｅ−ＬＬＤＰＥ樹脂の含有量について
前記洗浄片の原料として以下の表１に記載する各原料および副原料を使用し、かつ該表１に記載される一次加熱条件とすると共に、同じく記載される発泡倍率８〜１５倍（参照として見掛け密度０．０６〜０．１５ｇ／ｃｍ^３）となるように設定した一段発泡法により、実施例１〜５および比較例１〜３に係る試験片発泡体を夫々製造し、ＪＩＳＫ６７６７に準拠した方法等を用いて引張強度（ＭＰａ）、引裂強度（Ｎ／ｃｍ）および２５％圧縮硬さ（ＭＰａ）の測定を夫々行ない、その測定物性値から本発明に係る洗浄片としての評価を○または×により行なった。なお全原料の混合・混練には、ニーダ（１リットルニーダ；トーシン製）およびロール（１０ｉｎｃｈロール；コビキ製）を夫々２５ｍｉｎおよび７ｍｉｎ使用して実施し、一次加圧加熱時に掛けられる温度は１５８℃×４０ｍｉｎ、圧力は８．０ＭＰａに設定した。また使用した各原料は、以下に述べる。
【００３１】
使用した各原料は以下の通りである。
・Ｍｅ−ＬＬＤＰＥ（Ａ）：商品名１Ｐ５３Ａ；東ソー製（密度０．８９ｇ／ｃｍ^３）
・Ｍｅ−ＬＬＤＰＥ（Ｂ）：商品名７Ｐ０４Ｂ；東ソー製（密度０．９０ｇ／ｃｍ^３）
・ＥＥＡ樹脂Ａ：商品名ＮＵＣ６２２０；日本ユニカー製
・ＥＥＡ樹脂Ｂ：商品名ＮＵＣ６２２１；日本ユニカー製
・ＥＶＡ樹脂：商品名＃５４０；東ソー製
・発泡剤：アゾジカルボンアミド
・発泡助剤Ａ：酸化亜鉛
・発泡助剤Ｂ：ステアリン酸亜鉛
・造核剤：重炭酸カルシウム
・架橋剤：ジクミルパーオキサイド
【００３２】
【表１】

【００３３】
（実験１の結果）
得られた各物性値および評価を上記表１に併せて示す。ここから実施例に掛かる試験片は、比較例に係る試験片に較べて、引張強度、引裂強度および２５％圧縮硬さについて、何れも良好であることが確認された。
【００３４】
（実験２）Ｍｅ−ＬＬＤＰＥ樹脂の発泡倍率について
実験１の実施例３および４並びに比較例３に係る発泡体の組成を基本として、下記の表２に示すように原料中の発泡剤の添加量を変化させることで、発泡倍率を変動させた実施例６および実施例７並びに比較例４に係る発泡体から該実験１と同様な試験片を作製し、各測定および評価を行なった。なお全原料の混合・混練条件等については実験１と同様とし、一次加圧加熱時に掛けられる温度は１５４℃×４０ｍｉｎ、圧力は８．０ＭＰａに設定した。また参考として、表２中に実験１の実施例３および４並びに比較例３を併記する。
【００３５】
【表２】

【００３６】
（実験２の結果）
得られた各物性値および評価を上記表２に併せて示す。ここから各実施例については、発泡倍率が大きくなることによって、２５％圧縮硬さがより好適なものとなる一方、引張強度および引裂強度は充分な数値を維持することが確認された。また比較例４については、発泡倍率が増加と共に２５％圧縮硬さはより良化したが、他の強度データは悪化し、長時間に亘る使用に耐えないことが確認された。
【００３７】
【発明の効果】
以上に説明した如く、本発明に係る洗浄片によれば、洗浄片の樹脂としてメタロセン触媒を用いてα−オレフィンを共重合させた直鎖状低密度ポリエチレン（Ｍｅ−ＬＬＤＰＥ）樹脂を、少なくとも３０重量部使用するようにすることで、得られる発泡体の物性値を、引張強度を１．３〜２．０ＭＰａ、引裂強度を４３〜６０Ｎ／ｃｍ、２５％圧縮硬さを２．０ＭＰａ以下に夫々設定し、これにより車体を損傷することなく確実な洗浄を行ない得ると共に、これまでより格段に長時間の稼働に耐え得る洗浄片を得ることができる。また前記Ｍｅ−ＬＬＤＰＥ樹脂の密度を、０．８８〜０．９３ｇ／ｃｍ^３、好ましくは０．８７〜０．９１ｇ／ｃｍ^３に設定することで、好適な柔軟性を容易に発現し得る効果を奏する。
【図面の簡単な説明】
【図１】洗浄片を使用した洗車ブラシの構造と、稼働した際の動きを示す概略図である。[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is suitably used for a car wash brush, and can be washed without damaging the paint and exterior parts of an automobile. This relates to a cleaning piece that can be used repeatedly.
[0002]
[Prior art]
As shown in FIG. 1, an automatic car washer generally installed in a gas station or the like includes a car wash brush 10 in which a number of flexible washing pieces 12 are planted around a rotating shaft 14 that can be controlled and rotated. By rotating the car wash brush 10, the cleaning pieces 12 are brought into contact with the vehicle body to be cleaned (see FIG. 1 (b)), and the surface of the vehicle body is cleaned by spraying a detergent onto the body.
[0003]
So far, the cleaning pieces 12 have generally been made of various materials such as cloth and nylon, but these materials have the following problems.
{Circle around (1)} When the material is a cloth When various kinds of cloths are used as the material for the cleaning pieces, they have high flexibility and low hardness, so that there is almost no abrasion or the like due to the cleaning on the body surface or the like. However, since the cloth easily retains the absorbed moisture, there is a problem that the moisture retained in the cloth freezes in winter or in a cold region to lower the flexibility. Further, if cleaning is performed in such a frozen state, not only will the car be scratched, but also serious damage will occur, such as, for example, denting the vehicle body or damaging the glass.
{Circle around (2)} When the material is nylon If nylon is used as the material of the cleaning piece, the above-mentioned disadvantages caused by freezing in a cold region can be avoided because nylon has almost no water absorption. However, nylon generally has a high hardness, and thus has a drawback that it rubs an automobile during washing.
[0004]
In view of the above problems, use of a cleaning piece made of a foam of ethylene-vinyl acetate (hereinafter referred to as EVA) resin having low hardness and hardly exhibiting water absorption has been proposed. The EVA resin is very flexible in terms of material, and has a feature that when formed into a foam, the internal bubbles are independent of each other and the open cell ratio can be reduced. Therefore, as described above, low hardness and low water absorption can be exhibited. However, the car wash brush 10 using the EVA resin foam as the cleaning piece 12 has a high friction coefficient. Therefore, in actual use, when the cleaning piece 12 is rotated during cleaning, a protrusion of an automobile, for example, an external antenna, There is a drawback that it gets entangled with mirrors and other exterior parts. If the washing with the car wash brush 10 is continued in such a situation, a problem such as damage of the portion of the antenna or the like with which the washing piece 12 is entangled is pointed out.
[0005]
As means for preventing damage to the car exterior parts due to the above-described entanglement of the EVA resin foam, the structure of the EVA resin foam itself is destroyed when stress is applied to the extent that the exterior parts are damaged. A method of avoiding the damage of the exterior component is conceivable. This method is possible by controlling the strength of the EVA resin foam. As a means for controlling the strength, adjustment of the degree of crosslinking of the foam, that is, adjustment of the degree of intermolecular bonding, is considered. The degree of crosslinking may be reduced by reducing the degree of crosslinking. However, the degree of crosslinking is simultaneously one of the most important factors in foaming the foam, and as the degree of crosslinking decreases, the viscosity of the foam decreases and a stable foam cannot be obtained. Disadvantages are pointed out.
[0006]
[Problems to be solved by the invention]
In order to solve this problem, it is conceivable to employ, for example, a polyolefin-based resin such as ethylene-ethyl acrylate (hereinafter, referred to as EEA) resin as a main raw material of the cleaning piece 12. By using the polyolefin-based resin, it is possible to manufacture the cleaning piece 12 in which each property value such as flexibility, water absorption and tensile strength is within a predetermined range. However, the EEA resin has many short-chain branches such as an ethyl acrylate group (a vinyl acetate group in the EVA resin) and is excellent in flexibility, but has low mechanical strength such as tensile strength and tear strength. The durability of the washing pieces 12 is not sufficient for thousands of car washing operations when actually used, and there is a problem that the washing pieces 12 are torn or worn.
[0007]
The problem is that the polyolefin resin represented by the EEA resin is made using a Ziegler-Natta catalyst, so that the lamella (a folded crystal of polyethylene) is thick and the number of tie molecules connecting the lamella is small. Due to the use of Specifically, the number of the tie molecules greatly affects the mechanical properties such as the tensile strength of the EEA resin, and when the number of the tie molecules is small, the tie molecules are easily broken from there, and as a result, This is because the mechanical properties deteriorate. One of the means for improving the mechanical strength of such a resin is foaming at a low magnification. In this method, however, the hardness of the obtained EVA resin foam is increased and the flexibility is lost. The problem becomes apparent.
[0008]
[Object of the invention]
The present invention has been proposed in view of the problem inherent in the cleaning piece according to the prior art, and has been proposed to appropriately solve the problem, and uses a metallocene catalyst as a raw material of a cleaning piece constituting a car wash brush. By using a substance containing a linear low-density polyethylene (hereinafter, referred to as Me-LLDPE) resin obtained by copolymerizing an α-olefin, various properties such as hardness, tensile strength and tear strength of the obtained foam can be obtained. An object of the present invention is to provide a cleaning piece that controls physical property values of mechanical strength, can be suitably used for a car wash brush, and can perform reliable cleaning with better durability without damaging a vehicle body. .
[0009]
[Means for Solving the Problems]
To overcome the above problems and achieve the intended purpose, the cleaning piece of the present invention is a number of flexible cleaning pieces constituting a car wash brush,
The cleaning piece is formed of a resin foam containing a linear low-density polyethylene resin obtained by copolymerizing an α-olefin using a metallocene catalyst.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a cleaning piece according to the present invention will be described below with reference to a preferred embodiment. The inventor of the present application employs a resin containing a linear low-density polyethylene (hereinafter, referred to as Me-LLDPE) resin obtained by copolymerizing an α-olefin with a metallocene catalyst, and obtains the hardness and tensile strength of the obtained foam. By keeping the physical properties of various mechanical strengths such as strength and tear strength within a predetermined range, the mechanical strength required for cleaning for a long period of time is maintained, and there is no fear of damaging the vehicle body, and the car washing brush is not used. It has been found that a cleaning strip which can be suitably used for the above is obtained. Further, the structure of the car wash brush according to the preferred embodiment is almost the same as that of the car wash brush 10 according to the related art described above, so that detailed description of the configuration and the like is omitted, and the same reference numerals are used. .
[0011]
As shown in FIG. 1, a car wash brush 10 employing a cleaning piece according to a preferred embodiment is provided with a rotating shaft 14 that rotates under control, and is implanted on the rotating shaft 14 so that when the shaft 14 rotates, an object to be cleaned is rotated. And a large number of cleaning pieces 12 that can be cleaned by contacting the vehicle body. The cleaning piece 14 is a Me-LLDPE resin obtained by mixing and foaming the Me-LLDPE resin and a polyolefin resin such as an EEA resin as a resin component with a predetermined auxiliary material such as a foaming agent and a crosslinking agent. It is manufactured from a resin-containing foam (hereinafter referred to as a foam).
[0012]
The Me-LLDPE resin is a linear low-density polyethylene (hereinafter referred to as LLDPE) resin obtained by copolymerizing an α-olefin using a metallocene catalyst. The LLDPE resin is a copolymer of ethylene and an α-olefin such as 1-butene, 1-hexene or 1-octene, and the copolymer has an ethyl branch, an n-butyl branch or an n-hexyl branch. Low density polyethylene introduced into the structure. The metallocene catalyst is also called a Kaminsky catalyst and has, for example, a structure in which zirconocene dichloride and methylaluminoxane are combined, exhibits high polymerization activity with respect to ethylene, and has a uniform active site (single-site catalyst Single Site Catalysts). (SSC)). Since the metallocene catalyst is a homogeneous catalyst, the molecular structure of the polymer can be precisely designed, and the fine molecular structure and copolymerization reactivity of the polymer can be freely controlled.
[0013]
The SSC such as the metallocene catalyst has a narrower molecular weight distribution than a conventional catalyst typified by the Ziegler-Natta catalyst or the like, a so-called multi-site catalyst (MSC), and has a smaller molecular weight distribution. Since the comonomer contents are almost equal, the distribution of the molecular weight of the obtained LLDPE resin and the concentration of the short-chain branching are small, and as a result, it is also excellent in that the structural uniformity is high.
[0014]
Various mechanical strengths of the linear low-density polyethylene resin obtained by copolymerizing an α-olefin using the above-mentioned metallocene catalyst are higher than those of the conventional polyolefin resin, for the following reasons. That is, since the thickness of the lamella can be reduced, the number of tie molecules connecting the lamella can be relatively increased. Therefore, compared to when the number of the tie molecules is small, a strong tensile or tearing force is dispersed, and as a result, physical properties excellent in tensile strength and tear strength are exhibited.
[0015]
The content of the Me-LLDPE resin in all the resin components, that is, the mixing ratio with various polyolefin-based resins described later ([0016]) is set to at least 30 parts by weight or more, preferably 50 parts by weight or more. With such a mixing ratio, the ease of mixing and kneading the resin component obtained by mixing with other auxiliary materials such as a foaming agent is increased. Further, it is possible to easily produce a suitable foam having both the excellent physical strength of the Me-LLDPE resin and the flexibility of various polyolefin resins such as an EVA resin and an EEA resin.
[0016]
Examples of the polyolefin-based resin include a copolymer of ethylene and methyl, ethyl, propyl, butyl or each alkyl acrylate (ester content: within 45 mol%), or a mixture of two or more of these. Is used. In addition, it is also possible to use a mixture of the above-mentioned copolymer or mixture with isotactic polypropylene or atactic polypropylene. Chlorinated products having a chlorine content of up to 60% by weight can be used. In particular, as the polyolefin-based resin, an EVA resin described in the related art when formed into a foam, or an EEA resin having substantially the same physical properties as a foam obtained from the EVA resin and exhibiting a low tensile strength Is preferred.
[0017]
As the foaming agent, an inorganic or organic foaming agent can be used without limitation. Specific examples include sodium bicarbonate, ammonium bicarbonate, azodicarbonamide, dinitrosopentamethylenetetramine, dinitrosoterephthalamide, azobisisobutyronitrile, and sulfonylhydrazides. Of these, azodicarbonamide, azobisisobutyronitrile and sulfonyl hydrazides are preferred. The amount of the foaming agent is generally 3 to 30 parts by weight based on 100 parts by weight of the resin containing the Me-LLDPE resin, and is set according to a desired expansion ratio.
[0018]
In order to control the foaming state, a foaming aid such as a compound containing urea as a main component, metal oxides such as zinc oxide and lead oxide, various fatty acids, and metal salts of various fatty acids may be added. Further, in order to improve the physical properties, carbon black, calcium carbonate, asbestos, various metal oxides, or the like as a filler may be mixed as necessary. In particular, carbon black or calcium carbonate is suitable for cost reduction.
[0019]
The cross-linking agent has a decomposition temperature at least equal to the flow start temperature of the Me-LLDPE resin and the polyolefin-based resin constituting the resin component, and is decomposed by heating to generate free radicals to generate molecules of the polyolefin-based resin. Organic peroxides that generate cross-links between them. As the organic peroxide, for example, dicumyl peroxide, 2,5-dimethyl-2,5-bis-tert-butylperoxyhexene, 1,3-bis-tert-peroxyisopropylbenzene, or the like can be used. .
[0020]
The physical properties that the foam constituting the cleaning piece 12 should exhibit include hardness indicating flexibility, which is an index of the tendency of the vehicle to be damaged during car washing, and sufficient car washing function in use, and And mechanical strength such as tensile strength indicating durability against change. In particular, as the hardness, 25% compression hardness is adopted in consideration of the rotation state during use.
[0021]
Regarding the hardness, it is desired that a 25% compression hardness representing the hardness is 0.2 MPa or less, preferably 0.12 MPa or less. It should be noted that if the 25% compression hardness exceeds 0.2 MPa, it is empirically known that the vehicle body may be scratched in normal use. This hardness is a physical property value basically determined by the density of the Me-LLDPE resin and the expansion ratio of the resin foam constituting the cleaning piece 12.
[0022]
In the Me-LLDPE resin, a substance whose density is set to 0.88 to 0.93 g / cm ³ , preferably 0.87 to 0.91 g / cm ³ is used. This is because, like the EVA resin having a vinyl acetate group and the EEA resin having an increased flexibility with an increase in the content of an ethyl acrylate group, LLDPE has a low number of short-chain branches (α-olefins) to be copolymerized. Due to the increase, the density is reduced and the number of short-chain branches is increased, thereby inhibiting the crystal formation of LLDPE to be obtained. To do that. When the density is less than 0.88 g / cm ^3, it is considered that the 25% compression hardness representing the hardness exceeds 0.2 MPa, and when it exceeds 0.93 g / cm ³ , the obtained Me- The melting point of the LLDPE resin increases, and as a result, various adverse effects due to an increase in the required temperature during kneading of the resin with a foaming agent or a crosslinking agent, specifically, heat during kneading of the foaming agent or the crosslinking agent. This leads to problems such as an increase in the running cost such as the maintenance cost and the amount of energy used for improving the heat resistance of the disassembling and various kneading devices. By controlling in this manner, a resin kneaded product as an intermediate material serving as a base of the foam capable of achieving the above-described hardness can be obtained.
[0023]
As for the expansion ratio, if it is in the range of 8 to 15 times, preferably about 8 to 12 times, the foam using the resin kneaded material containing the Me-LLDPE resin, that is, the cleaning piece 12 has the above-described value. Can be achieved. It should be noted that depending on the type and the mixing ratio of the resin as the main raw material, the setting of the expansion ratio may deviate from the range of each physical property value according to the present invention, so care must be taken. Basically, as the expansion ratio increases, the structure of the foam constituting the cleaning piece 12 becomes sparse, so that the tensile strength and the like deteriorate, and the 25% compression hardness improves. In addition, it is also known that the hardness is reduced contrary to the amount of the filler mixed in the foam raw material. If the foaming ratio is less than 8 times, the hardness increases, and if it exceeds 15 times, the tensile strength described later ([0025]) decreases. This expansion ratio can be easily set by the amount of the above-mentioned foaming agent and the like added to the main raw material resin.
[0024]
The tensile strength is preferably in the range of 1.3 to 2.0 MPa (according to JIS K 6767), and basically the intermolecular force in the foam structure, that is, the number of short-chain branches of Me-LLDPE and the like. It is determined by the amount of the cross-linking agent or the like used in [0019] above. Even if the tensile strength is less than 1.3 MPa, it can be sufficiently used for cleaning in a normal state, but in a long-term use over time, the foam is torn and the necessary cleaning power cannot be obtained. I will. On the other hand, when the pressure exceeds 2.0 MPa, when the rotating cleaning piece is wrapped around an exterior product such as a mirror of an automobile, there is a high fear that the exterior product may be damaged, and the cleaning product may be employed as the cleaning product of the present invention. Absent.
[0025]
The tear strength is preferably in the range of 43 to 60 N / cm (based on JIS K 6767). This value is proportional to the tensile strength and is basically determined by the intermolecular force in the foam structure. Even if the tear strength is less than 43 N / cm, it can be sufficiently used for cleaning in a normal state, but in a long-term use over time, the foam breaks and the necessary cleaning power is obtained. Will be gone. On the other hand, if it exceeds 63 N / cm, there is a high possibility that when the rotating cleaning piece is wrapped around an exterior component such as a mirror of an automobile, the exterior component may be damaged, and cannot be used as the cleaning component of the present invention. .
[0026]
[Example of manufacturing method]
Hereinafter, an example of a method for suitably manufacturing a cleaning piece of a car wash brush according to the present invention will be described. Using a resin component consisting of the Me-LLDPE resin and the polyolefin resin, and a crosslinking agent, a foaming agent, a foaming aid, a filler and various desired auxiliary materials, using a conventionally known kneader such as a Banbury mixer. The mixture is sufficiently kneaded to obtain a kneaded resin. Then, the resin kneaded material is filled under pressure and heat using a predetermined mold or the like, and the cross-linking agent and the foaming agent are completely decomposed and then expanded at a time by reducing the pressure. A primary (intermediate) foam obtained by primary foaming by the mold is further heated under normal pressure to perform secondary foaming, thereby obtaining a Me-LLDPE resin-containing foam having a desired density by a so-called two-stage foaming method.
[0027]
The one-stage foaming method is preferably employed because the equipment and operation to be used are simple, and the strength of the obtained foam is higher than that of the two-stage foaming method. Even so, it is possible to manufacture a suitable cleaning piece 12 according to the present invention, and it is appropriately selected according to various physical properties such as the expansion ratio of the cleaning piece 12 to be actually obtained. Usually, when the expansion ratio is about 10 to 15 times, it is preferable to use the one-stage expansion method.
[0028]
Although the above-described required shape is formed by employing the chemical foaming method and the extrusion molding, any known foaming method or molding may be used as long as it satisfies predetermined physical properties and can be formed into the required shape. Even the law can be adopted. Particularly, as described above ([0015]), by mixing the Me-LLDPE resin in an amount of 30 parts by weight or more, preferably 50 parts by weight or more, the mixing and kneading of all the raw materials can be easily performed. Become.
[0029]
[Experimental example]
Hereinafter, an experimental example of a cleaning piece that can be suitably used for the car wash brush according to the present invention will be described. In this experimental example, an example is shown in which an EEA resin is used as a resin other than the Me-LLDPE resin constituting the resin component, but the present invention is not particularly limited to the contents described in this experimental example.
[0030]
(Experiment 1) Regarding the content of the Me-LLDPE resin, the respective raw materials and auxiliary raw materials described in Table 1 below were used as raw materials for the cleaning pieces, and the primary heating conditions described in Table 1 were used. Tests according to Examples 1 to 5 and Comparative Examples 1 to 3 by a one-stage foaming method set so as to have an expansion ratio of 8 to 15 times (apparent density of 0.06 to 0.15 g / cm ³ as a reference). Each of the piece foams was manufactured, and the tensile strength (MPa), the tear strength (N / cm), and the 25% compression hardness (MPa) were measured using a method according to JIS K 6767, and the measured physical properties were measured. From the values, the evaluation as a cleaning strip according to the present invention was performed by ○ or ×. The mixing and kneading of all the raw materials were carried out using a kneader (1 liter kneader; manufactured by Toshin) and a roll (10 inch roll; manufactured by Kobiki) for 25 min and 7 min, respectively. × 40 min, pressure was set to 8.0 MPa. The used raw materials are described below.
[0031]
The raw materials used are as follows.
-Me-LLDPE (A): trade name 1P53A; manufactured by Tosoh (density 0.89 g / cm ³ )
・ Me-LLDPE (B): trade name 7P04B; manufactured by Tosoh (density 0.90 g / cm ³ )
EEA resin A: trade name NUC6220; manufactured by Nippon Unicar EEA resin B: trade name NUC6221; manufactured by Nippon Unicar EVA resin: trade name # 540; manufactured by Tosoh Blowing agent: azodicarbonamide Foaming aid A: zinc oxide -Foaming aid B: zinc stearate-Nucleating agent: calcium bicarbonate-Crosslinking agent: dicumyl peroxide
[Table 1]

[0033]
(Result of Experiment 1)
The obtained physical properties and evaluation are shown in Table 1 above. From this, it was confirmed that the test pieces according to the examples had better tensile strength, tear strength and 25% compression hardness than the test pieces according to the comparative examples.
[0034]
(Experiment 2) Regarding the expansion ratio of the Me-LLDPE resin Based on the compositions of the foams according to Examples 3 and 4 and Comparative Example 3 of Experiment 1, the amount of the foaming agent added to the raw materials as shown in Table 2 below The test pieces similar to those in Experiment 1 were prepared from the foams according to Examples 6 and 7 and Comparative Example 4 in which the expansion ratio was varied by changing the ratio, and each measurement and evaluation were performed. The conditions for mixing and kneading all the raw materials were the same as those in Experiment 1. The temperature applied during the primary pressurization and heating was set at 154 ° C. × 40 min, and the pressure was set at 8.0 MPa. Tables 2 and 3 also show Examples 3 and 4 of Experiment 1 and Comparative Example 3 for reference.
[0035]
[Table 2]

[0036]
(Result of Experiment 2)
The obtained physical properties and evaluation are shown in Table 2 above. From this, it was confirmed that, for each of the examples, as the expansion ratio increased, the 25% compression hardness became more preferable, while the tensile strength and the tear strength maintained sufficient numerical values. In Comparative Example 4, it was confirmed that the 25% compression hardness was further improved as the expansion ratio was increased, but the other strength data was deteriorated, and it was not possible to withstand use for a long time.
[0037]
【The invention's effect】
As described above, according to the cleaning piece of the present invention, a linear low-density polyethylene (Me-LLDPE) resin obtained by copolymerizing an α-olefin with a metallocene catalyst is used as the resin of the cleaning piece at least 30 times. By using parts by weight, the physical properties of the obtained foam can be reduced to a tensile strength of 1.3 to 2.0 MPa, a tear strength of 43 to 60 N / cm, and a 25% compression hardness of 2.0 MPa or less. By setting each of them, it is possible to perform reliable cleaning without damaging the vehicle body, and to obtain a cleaning piece that can withstand much longer operation than before. In addition, by setting the density of the Me-LLDPE resin to 0.88 to 0.93 g / cm ³ , preferably 0.87 to 0.91 g / cm ³ , an effect that suitable flexibility can be easily exhibited. To play.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a structure of a car wash brush using a cleaning piece and a movement at the time of operation.

Claims

A number of flexible cleaning pieces that make up the car wash brush,
The cleaning piece, wherein the cleaning piece is formed of a resin foam containing a linear low-density polyethylene resin obtained by copolymerizing an α-olefin using a metallocene catalyst.

The cleaning piece according to claim 1, wherein the linear low-density polyethylene resin is used in an amount of 30 parts by weight or more, preferably 50 parts by weight or more based on 100 parts by weight of all resin components.

The cleaning piece according to claim 1, wherein the density of the linear low-density polyethylene resin is set to 0.88 to 0.93 g / cm ³ , preferably 0.87 to 0.91 g / cm ³ .

The cleaning strip according to any one of claims 1 to 3, wherein the expansion ratio of the linear low-density polyethylene resin-containing foam is set in a range of 8 to 15 times, preferably 8 to 12 times.

The linear low-density polyethylene-containing foam has a tensile strength set in a range of 1.3 to 2.0 MPa, a tear strength set in a range of 43 to 60 N / cm, and a 25% compression hardening. The cleaning piece according to any one of claims 1 to 4, wherein the cleaning piece is set to 0.2 MPa or less, preferably 0.12 MPa or less.

The cleaning piece according to any one of claims 1 to 5, wherein an ethylene-vinyl acetate resin and / or an ethylene-ethyl acrylate resin are used as a resin component other than the linear low-density polyethylene resin.