JP4110032B2 - Foaming agent composition, polyolefin-based foam using the same, and method for producing the same - Google Patents
Foaming agent composition, polyolefin-based foam using the same, and method for producing the same Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は発泡剤組成物、およびこれを用いるポリオレフィン系発泡体とその製造方法に関する。
【０００２】
【従来の技術】
ポリオレフィン系樹脂に発泡剤を加え、熱加工処理等によって前記発泡剤が発泡することによってなる発泡体（以下、発泡体とする）がある。このような発泡体は、ドアトリム等の自動車の内装される樹脂部品において用いられている。この発泡体の製造方法は、化学発泡剤をポリオレフィン系樹脂に添加し、射出成形装置によって発泡成形させる方法がある。このとき、射出成形する前の初期板厚が極めて薄く、初期板厚と成形後の発泡体を比較したときの発泡倍率（以下、発泡倍率とする）が大きくなると（例えば、初期板厚が３．０ｍｍ以下であって、発泡倍率１．２倍以上）発泡体中の気泡が粗大となり、外観品質もよくなかったため、気泡が微細であり、外観品質が通常成形品と同程度良好となる発泡体を作る課題を実現することが難しかった。このような不具合の解決手段として、発泡剤中に気泡核剤としてタルクやシリカ等を添加して射出成形する方法が知られている。
【０００３】
しかし、これらのタルクやシリカ等を発泡剤中に添加する方法では、発泡体中の気泡の微細化は図れるとされているが、表面平滑性を含めた外観はタルクやシリカ等を発泡剤中に添加しない通常成形品と比べて劣る場合がある。そこで、特開２０００−２６４９９３号公報では、熱可塑性樹脂に熱分解型発泡剤にクエン酸塩とリチウム化合物（ただし、リチウム塩は除く）または亜鉛華を含んだ発泡剤組成物を添加することで、微細な気泡で発泡成形される発泡剤組成物および熱可塑性樹脂発泡体の製造方法が記載されている。
【０００４】
なお、従来技術としては、特開２００１−１８４９３号公報では、ポリプロピレン樹脂の発泡体からなる容器の射出成形による製造方法が、特許第３１１８１２５号公報では熱可塑性エラストマーの発泡体の射出成形による製造方法が開示されている。
【０００５】
【特許文献１】
特開２０００−２６４９９３号公報
【特許文献２】
特開２００１−１８９４３号公報
【特許文献３】
特許第３１１８１２５号公報
【０００６】
【発明が解決しようとする課題】
しかし、上記発泡体は、射出成形による発泡体形成時のその外観等が、その用途やニーズによっては、まだ十分でない場合があることもある。例えば、射出成形時に樹脂の混合が円滑に行われないために起こるウエルドライン、表面の微少な凹凸であるアバタ、射出成型時にキャビティ部へ樹脂が十分に浸透しないなどの理由によって発生するフラッシュが多少発生する場合や射出時の樹脂のフローや成形性が十分でない場合もありうる。
【０００７】
本発明は上記課題を鑑みてなされたものであり、発泡体中の気泡をより微細で均一な分布なものとし、平面平滑性等の外観等に優れたポリオレフィン系発泡体およびそれを製造する方法と、その製造に用いる発泡剤組成物を提供することを目的とする。
【０００８】
【課題を解決するための手段】
【０００９】
上記目的を達成するために、本発明の発泡剤組成物は、樹脂と混合され、熱加工処理により樹脂内部で発泡し、前記樹脂の発泡体を成形する発泡剤組成物において、熱分解型発泡剤と、炭素数１２〜２０の飽和脂肪酸塩と、
を含むことを特徴とする。
【００１０】
ここで、熱分解型発泡剤と炭素数１２〜２０の高級飽和脂肪酸塩を加えた発泡剤組成物を用いることで、発泡体を発泡成形したときに、発泡体中の気泡を従来技術に比べてより微細な状態とすることができるようになる。その結果、成形時の気泡の影響を防止でき、ひいては、発泡体の外観の向上を図ることができる。
【００１１】
また、気泡がより微細となることによって、外観の向上だけでなく、様々な利点を得ることができる。例えば、発泡体の強度等の物理的な物性を向上させることが可能となる。気泡が微細となることによって、綿密な気泡構造を有する発泡体となり、ソリッドな物性により近づくことができるなどの作用が得られるからである。
【００１２】
この発泡体中の気泡が微細となる理由は、以下のようにも考えられる。通常、樹脂内部で熱分解型発泡剤が発泡したときに、発泡体中の気泡が大きくなるという現象が生じやすい。これは、発泡の際、多量に生じる気泡同士が結合して、泡の大きさが大きくなってしまうことなどが考えれられている。これを解消するために、炭素数１２〜２０の高級飽和脂肪酸塩を加えることで界面活性的作用等によって発泡体中の気泡が結合したり、破裂したりすることを、防止することができるようになり、結果として、発泡体中の気泡を微細である状態とすることができるのではないかと勘案されるところである。
【００１３】
また、上記本発明の発泡剤組成物は、さらにクエン酸塩と、気泡核剤として、亜鉛華、タルク、シリカのうち少なくともいずれか１つと、を含んでいてもよい。
【００１４】
従来技術から、クエン酸塩は、発泡体中の気泡を微細にすることが知られている。そのため、発泡体中の気泡の微細化を図るには炭素数１２〜２０の高級脂肪酸との相乗効果を望むことができる。
【００１５】
また、気泡核剤を用いることで、発泡体中の気泡を微細にすることも同様に知られている。気泡核剤を用いるとその部分で熱分解型発泡剤が発泡するため、樹脂中で発泡する箇所の整合をとりやすくすることができる。その理由は、周辺部の樹脂と比べて、気泡核剤となるタルクやシリカ、亜鉛華は熱容量が大きい。そのため、気泡核剤がホットスポットとなり、その部分で熱分解型発泡剤が発泡しやすくなるということなどが勘案される。
【００１６】
また、上記本発明の発泡剤組成物は、前記発泡剤組成物の全重量に対し、前記熱分解型発泡剤は炭酸水素ナトリウムを５７．０〜５７．５重量部、前記クエン酸塩はクエン酸モノナトリウムを２８．５〜２９．０重量部、前記炭素数１２〜２０の飽和脂肪酸塩はステアリン酸リチウムを５．５〜６．０重量部、前記気泡核剤を８．５〜９．０重量部、含んでいてもよい。
【００１７】
熱分解型発泡剤としての炭酸水素ナトリウムは、発泡剤組成物に対して、上記重量部下限値以下では、発泡体を成形するのに十分の発泡量を得られない場合等がある。また、上記重量部上限値以上では、発泡体を成形する際に、発泡が激しくなり、微細な気泡を有する発泡体の提供が難しい場合等がある。
【００１８】
クエン酸塩としてのクエン酸モノナトリウムは、発泡剤組成物に対して、上記重量部下限値以下では、発泡体を成形するのに発泡体中の気泡を微細にする効果を得られないない場合等がある。また、上記重量部上限値以上では、他の組成物の含有量を低下させるなど発泡剤組成物として適さなくなってしまう場合がある。
【００１９】
炭素数１２〜２０の飽和脂肪酸塩としてのステアリン酸リチウムは、発泡剤組成物に対して、上記重量部下限値以下では、発泡体を成形するのに発泡体中の気泡を微細にする効果を得られないない場合等がある。また、上記重量部上限値以上では、他の組成物の含有量を低下させるなど発泡剤組成物として適さなくなってしまう場合がある。
【００２０】
気泡核剤は、発泡剤組成物に対して、上記重量部下限値以下では、発泡体を成形するのに発泡体中の気泡を微細にする効果を得られないない場合等がある。また、上記重量部上限値以上では、他の組成物の含有量を低下させるなど発泡剤組成物として適さなくなってしまう場合がある。
【００２１】
次に、本発明の発泡剤組成物を用いたポリオレフィン系発泡体の製造方法は、ポリオレフィン系の樹脂に混合し、前記混合物に、射出成形装置中で熱加工処理を加えることで、前記発泡剤組成物中の前記熱分解型発泡剤を発泡させ、射出発泡成形されるポリオレフィン系発泡体の製造方法において、前記ポリオレフィン系の樹脂は、融点１４０℃以上かつＭＦＲ１０以上であって、温度２００℃での剪断速度０．１〜５．０×１０2sec-1における溶融粘度が２．０×１０4ポイズ以下であることを特徴とする。
【００２２】
上記発泡剤組成物を用いて、発泡体を成形するには、この条件の樹脂を用いると外観および基材性能に加えて、成形加工も容易であるなど好ましい場合が多い。例えば、粘度が低いため成形加工が容易となることなどがある。
【００２３】
また、上記本発明のポリオレフィン系発泡体の製造方法は、前記射出発泡成形が、前記混合物を１７０〜２３０℃に加熱し、前記加熱した混合物を、射出成形装置の射出部からキャビティ部へ１０〜２００ＭＰａの圧力で、射出開始から終了まで射出時間３秒以内に射出し、前記射出終了後３秒以内に、前記キャビティ部に隣接する前記射出装置の金型コア部を０．１〜１００ｍｍ／seｃの速度で前記キャビティ部の厚さを大きくする方向へ後退させ、前記後退以後に前記キャビティ内の前記混合物を４０〜８０℃で１ｓ以上冷却するコアバック式の射出発泡成形であるものであってもよい。
【００２４】
射出時において、上記上限値を超えた射出時間となると、樹脂の結晶化が起こり、発泡倍率を高めることが難しくなったり、樹脂中の発泡ガスが表面へと逃げることを許すこととなり、成形された発泡体表面にシルバーマーク等が発生しやすくなるおそれがある。
【００２５】
射出後、上記範囲の射出終了後からコアバック開始までの時間、コアバックの時間、冷却時間、冷却温度でないと、発泡体の成形では、混合物のコア層は、冷却されにくく、スキン層は早く冷却されることから、発泡倍率の調整が難しい場合がある。
【００２６】
上記のように、この条件とした本発明の発泡剤組成物をポリオレフィン系の樹脂に用いて、コアバック式の射出成形装置で成形したポリオレフィン系発泡体では、さらに、外観および基材性能は勿論、成形加工もさらに容易であるなど好ましい。よって、優れた外観と基材性能を有するポリオレフィン系発泡体を提供することができる。
【００２７】
特に、従来の発泡剤ではポリオレフィン系樹脂は、ポリスチレン系樹脂などに比べ、その溶融粘度が大幅に低いため、発泡成形の際に、脱泡若しくは破泡現象を起こしてしまい、気泡の破壊等が発生し、発泡体の外観に影響を与えてしまうことがあった。それに対し、本発明では、ステアリン酸などの高級飽和脂肪酸を用いると、その高級飽和脂肪酸により、気泡の破裂等を押さえることが可能となり、ひいては、気泡の微細化が実現でき、優れた外観と基材性能を有するポリオレフィン系発泡体を提供することができる。
【００２８】
【発明の実施の形態】
以下、本発明の発泡剤組成物を用いて、ポリオレフィン系発泡体をコアバック式の射出成形装置によって成形し、自動車用ドアトリムを製造する実施形態について説明する。本発明の実施形態は、本発明の実施に関しての好ましい一例であって、本発明は、本実施形態に限定されるものではない。
【００２９】
発泡剤組成物は、その全重量に対し、熱分解型発泡剤として炭酸水素ナトリウムを５７．０重量部と、クエン酸塩としてクエン酸モノナトリウムを２８．５重量部と、炭素数１２〜２０の飽和脂肪酸塩としてステアリン酸リチウムを５．５重量部と、気泡核剤となるタルクを９．０重量部含んでいる発泡剤組成物を用いる。
【００３０】
発泡剤の基材となるポリプロピレン樹脂を用意する。このポリオレフィン系樹脂は、融点が１４０℃以上、ＭＦＲ（メルトフローレイト）が１０以上、好ましくはＭＦＲ５０程度であって、温度２００℃で剪断速度が０．１×１０2sec-1〜０．５×１０2sec-1において、溶融粘度が２．０×１０4ポイズ以下である物性を示すポリオレフィン系樹脂であればよい。
【００３１】
次に、望むドアトリムに発泡成形するための希望する型のキャブティ部を有する射出成形装置を用意する。ここの射出部にて上記ポリオレフィン系樹脂と発泡剤組成物を溶融等によって混合させた混合物（以下、単に混合物とする）を作成する。この混合方法は、ポリプロピレン樹脂に予め上記発泡剤組成物を配合するか、射出成形装置のシリンダーの途中から発泡剤を注入するなどとする。ここでポリプロピレン径樹脂の初期板厚は２．０ｍｍとした。
【００３２】
この混合物を射出成形装置の射出部（シリンダー）で１７０〜２３０℃となるように加熱する。該温度でこの混合物を、この射出成形装置の射出部からキャビティ部へ１０〜２００ＭＰａの圧力で射出する。この射出は射出開始から終了時まで３秒以内に射出を行えるものであればよい。
【００３３】
前記射出終了後３秒以内に、前記射出成形装置のキャビティ部に隣接する前記射出装置の金型コア部を０．１〜１００ｍｍ／seｃの速度で前記キャビティ部の厚さを大きくする方向へ後退させる。
【００３４】
前記後退以後に前記キャビティ部内の前記混合物を５０℃で１ｓ以上冷却する。冷却後、型を外し、発泡体の厚さ３．０ｍｍ、発泡倍率１．５倍のドアトリムの発泡成形が可能となる。
【００３５】
本製造方法によって、ウェルドラインやアバタ、フラッシュ等をさらに防止でこのため、外観補修等が必要でなくなった。それに加え、フローや成形性も従来と比べ向上したため、成形工程が迅速かつ、簡単に行えるようになった。
【００３６】
さらに、気泡の微細化はさらに顕著なものとなった。従来技術では、発泡倍率は１〜１．５倍以上で、気泡径も２００〜１５００μｍ、もしくはそれ以上となりうる場合があったが、本発明ではより微細な径で均一な気泡の分布によって外観、表面平滑性が良好である発泡体として、発泡倍率１．１〜２．０倍で気泡径２００μｍ以下の発泡体を提供することができるようになった。
【００３７】
ポリオレフィン系樹脂であれば、ポリエチレン、ポリブチレン等、であってもよい。さらには、単独のオレフィンのモノマーによる重合体に限られず、コモノマーとの共重合体であってもよい。そのような共重合体である場合は、コモノマーとしてはエチレン、１−ブテン、１−ヘキセン、４−メチル−１−ペンテン、１−オクテン、１−デセン等を用いることが好ましい。
ここで発泡剤組成物中の熱分解型発泡剤としては、他の無機発泡剤は勿論、アゾジカルボンアミド、ベンゼンスルホニルヒドラジド、Ｎ，Ｎ’−ジニトロソペンタメチレンテトラミン、５−フェニル−１，２，３，４−テトラゾールおよび有機酸金属塩等の有機化学系発泡剤を用いることもできる。
【００３８】
また、発泡剤組成物中のクエン酸塩としてはクエン酸トリナトリウムなどの他のナトリウム塩は勿論、カリウム塩、リチウム塩（ただし、炭素数：Ｃ１２〜２０の飽和脂肪酸リチウム塩は除く）であってもよい。
【００３９】
また、発泡剤組成物中の炭素数：Ｃ１２〜２０の飽和脂肪酸塩としてはステアリン酸塩に限られず、Ｃ１２のラウリン酸、Ｃ１４のミリスチン酸、Ｃ１６のパルミチン酸、Ｃ２０のアラキジン酸など、炭素数が１２〜２０の範囲である飽和脂肪酸であればよい。また、それらのリチウム塩に限られず、ナトリウム塩、カリウム塩などであってもよい。
【００４０】
また、気泡核剤としては亜鉛華、シリカ等、従来の気泡核剤、いずれでもよい。
【００４１】
【実施例】
本発明の発泡剤組成物を用いて自動車のドアトリムを成形した実施例と、従来品の発泡剤組成物を用いて自動車のドアトリムを成形した比較例と、の外観評価等を行った。実施例の発泡剤組成物は、炭酸水素ナトリウムを５７．０重量部、クエン酸モノナトリウムを２８．５重量部、ステアリン酸リチウムを５．５重量部、タルクを９．０重量部含んでいる。また、比較例は、炭酸水素ナトリウム７８．０重量部、クエン酸モノナトリウム１３．５重量部、ステアリン酸リチウム４．５重量部、タルク９．０重量部含んでいる。発泡剤組成物以外は、実施例と比較例ともに同じ材料・製造方法であり、ポリプロピレン樹脂に各発泡剤組成物を混入し、上記実施形態のコアバック式の射出成形装置にて、上記実施形態と同じ製造方法によりドアトリムを成形した。
【００４２】
外観評価は、発泡倍率、成形性、ウエルドライン、フロー、フラッシュ、アバタについて行った。なお、評価としては△を普通として○、◎と右の記号ほど外観が好ましいとして外観評価した。その結果を、以下の表１に示す。
【００４３】
【表１】
【００４４】
【発明の効果】
本発明の発泡剤組成物を用いることにより、発泡体中の気泡をより微細で均一な分布なものとし、平面平滑性等の外観や基材性能などに優れたポリオレフィン系発泡体とそれを製造する方法、およびその製造に用いる発泡剤組成物を提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foaming agent composition, a polyolefin foam using the same, and a method for producing the same.
[0002]
[Prior art]
There is a foam (hereinafter referred to as a foam) formed by adding a foaming agent to a polyolefin-based resin and foaming the foaming agent by heat processing or the like. Such foams are used in resin parts such as door trims that are installed in automobiles. As a method for producing this foam, there is a method in which a chemical foaming agent is added to a polyolefin-based resin and foamed by an injection molding apparatus. At this time, when the initial plate thickness before injection molding is very thin and the initial plate thickness is compared with the foam after molding (hereinafter referred to as the foaming rate) becomes large (for example, the initial plate thickness is 3). 0 mm or less and a foaming ratio of 1.2 times or more) Since the bubbles in the foam are coarse and the appearance quality is not good, the bubbles are fine and the appearance quality is as good as that of a normal molded product. It was difficult to realize the task of making a body. As a means for solving such a problem, a method of injection molding by adding talc or silica as a cell nucleating agent to a foaming agent is known.
[0003]
However, in the method of adding these talc and silica to the foaming agent, it is said that the bubbles in the foam can be made finer, but the appearance including the surface smoothness includes talc and silica in the foaming agent. It may be inferior to a normal molded product that is not added to the. Therefore, in Japanese Patent Laid-Open No. 2000-264993, by adding a foaming agent composition containing a citrate and a lithium compound (excluding a lithium salt) or zinc white to a thermally decomposable foaming agent to a thermoplastic resin. A foaming agent composition that is foam-molded with fine bubbles and a method for producing a thermoplastic resin foam are described.
[0004]
As a conventional technique, Japanese Patent Laid-Open No. 2001-18493 discloses a manufacturing method by injection molding of a container made of a polypropylene resin foam, and Japanese Patent No. 3118125 discloses a manufacturing method by injection molding of a foam of a thermoplastic elastomer. Is disclosed.
[0005]
[Patent Document 1]
JP 2000-264993 A [Patent Document 2]
JP 2001-18943 A [Patent Document 3]
Japanese Patent No. 3118125 [0006]
[Problems to be solved by the invention]
However, in some cases, the above-mentioned foam may not be sufficient in appearance or the like at the time of foam formation by injection molding depending on its use and needs. For example, weld lines that occur because the resin is not smoothly mixed during injection molding, avatars that are fine irregularities on the surface, and flash that occurs due to the fact that the resin does not sufficiently penetrate into the cavity during injection molding. It may occur or the resin flow and moldability at the time of injection may not be sufficient.
[0007]
The present invention has been made in view of the above problems, and has a finer and more uniform distribution of bubbles in the foam, and is excellent in appearance such as flatness and the like, and a method for producing the same. And it aims at providing the foaming agent composition used for the manufacture.
[0008]
[Means for Solving the Problems]
[0009]
In order to achieve the above object, the foaming agent composition of the present invention is mixed with a resin and foamed inside the resin by heat processing to form a foam of the resin. An agent, a saturated fatty acid salt having 12 to 20 carbon atoms,
It is characterized by including.
[0010]
Here, by using a foaming agent composition to which a pyrolytic foaming agent and a higher saturated fatty acid salt having 12 to 20 carbon atoms are added, when the foam is foam-molded, the bubbles in the foam are compared with the prior art. Thus, a finer state can be achieved. As a result, the influence of bubbles at the time of molding can be prevented, and as a result, the appearance of the foam can be improved.
[0011]
Further, since the bubbles become finer, not only the appearance is improved, but various advantages can be obtained. For example, physical properties such as strength of the foam can be improved. This is because, when the bubbles become fine, a foam having a fine cell structure is obtained, and an effect such as being closer to solid physical properties can be obtained.
[0012]
The reason why the bubbles in the foam are fine is considered as follows. Usually, when the pyrolyzable foaming agent is foamed inside the resin, a phenomenon that bubbles in the foam become large tends to occur. As for this, it is considered that bubbles generated in a large amount are combined at the time of foaming to increase the size of the bubbles. In order to solve this problem, it is possible to prevent the bubbles in the foam from being bound or ruptured by a surface active action or the like by adding a higher saturated fatty acid salt having 12 to 20 carbon atoms. As a result, it is considered that the bubbles in the foam may be in a fine state.
[0013]
The blowing agent composition of the present invention may further contain citrate and at least one of zinc white, talc, and silica as a cell nucleating agent.
[0014]
From the prior art, citrate is known to make the bubbles in the foam fine. Therefore, a synergistic effect with a higher fatty acid having 12 to 20 carbon atoms can be desired to reduce the size of bubbles in the foam.
[0015]
It is also known to make the bubbles in the foam fine by using a cell nucleating agent. When the cell nucleating agent is used, the pyrolyzable foaming agent foams at that portion, so that it is possible to easily align the foamed portions in the resin. The reason is that talc, silica, and zinc white, which are cell nucleating agents, have a larger heat capacity than the resin in the periphery. Therefore, it is considered that the bubble nucleating agent becomes a hot spot, and the pyrolytic foaming agent easily foams at that portion.
[0016]
The foaming agent composition of the present invention is based on the total weight of the foaming agent composition, the pyrolyzable foaming agent is 57.0-57.5 parts by weight of sodium hydrogen carbonate, and the citrate salt is citrate. 28.5 to 29.0 parts by weight of monosodium acid, the saturated fatty acid salt having 12 to 20 carbon atoms is 5.5 to 6.0 parts by weight of lithium stearate, and 8.5 to 9. 0 part by weight may be included.
[0017]
With respect to the foaming agent composition, sodium hydrogen carbonate as a pyrolytic foaming agent may not have a sufficient foaming amount to form a foam when the weight part is lower than the lower limit value. In addition, when the above-mentioned upper limit by weight is exceeded, foaming becomes severe when molding the foam, and it may be difficult to provide a foam having fine bubbles.
[0018]
When monosodium citrate as a citrate is less than the lower limit of the above-mentioned parts by weight relative to the foaming agent composition, it is not possible to obtain the effect of reducing the bubbles in the foam to form the foam. Etc. Moreover, if it is more than the upper limit of the above-mentioned parts by weight, it may become unsuitable as a foaming agent composition such as reducing the content of other compositions.
[0019]
Lithium stearate as a saturated fatty acid salt having 12 to 20 carbon atoms has the effect of making the bubbles in the foam finer when molding the foam below the lower limit of the above weight parts relative to the foaming agent composition. There are cases where it cannot be obtained. Moreover, if it is more than the upper limit of the above-mentioned parts by weight, it may become unsuitable as a foaming agent composition such as reducing the content of other compositions.
[0020]
If the cell nucleating agent is less than the lower limit value by weight of the foaming agent composition, there may be a case where the effect of making the bubbles in the foam fine is not obtained when the foam is molded. Moreover, if it is more than the upper limit of the above-mentioned parts by weight, it may become unsuitable as a foaming agent composition such as reducing the content of other compositions.
[0021]
Next, in the method for producing a polyolefin foam using the foaming agent composition of the present invention, the foaming agent is mixed with a polyolefin resin, and the mixture is subjected to a heat processing treatment in an injection molding apparatus. In the method for producing a polyolefin-based foam that is foamed by injection-molding by foaming the pyrolyzable foaming agent in the composition, the polyolefin-based resin has a melting point of 140 ° C. or higher and an MFR of 10 or higher at a temperature of 200 ° C. The melt viscosity at a shear rate of 0.1 to 5.0 × 10 2 sec −1 is 2.0 × 10 4 poises or less.
[0022]
In order to mold a foam using the above-mentioned foaming agent composition, it is often preferable to use a resin under these conditions because, in addition to the appearance and the performance of the base material, the molding process is easy. For example, since the viscosity is low, the molding process may be easy.
[0023]
Moreover, in the method for producing a polyolefin-based foam of the present invention, the injection foam molding is performed by heating the mixture to 170 to 230 ° C., and transferring the heated mixture from an injection part of an injection molding apparatus to a cavity part. Injection was performed within 3 seconds from the start to the end of injection at a pressure of 200 MPa, and within 3 seconds after the end of injection, the mold core portion of the injection device adjacent to the cavity portion was 0.1 to 100 mm / sec. The core portion is reciprocated in the direction of increasing the thickness of the cavity at a speed of, and after the retreat, the mixture in the cavity is cooled at 40 to 80 ° C. for 1 s or more, and is a core back type injection foam molding. Also good.
[0024]
At the time of injection, when the injection time exceeds the above upper limit, crystallization of the resin occurs, it becomes difficult to increase the foaming ratio, or the foaming gas in the resin is allowed to escape to the surface and molded. There is a risk that a silver mark or the like is likely to be generated on the surface of the foam.
[0025]
After injection, the time from the end of injection in the above range to the start of the core back, the time of the core back, the cooling time, and the cooling temperature, the foam core is difficult to cool the core layer of the mixture, and the skin layer is fast. Since it is cooled, it may be difficult to adjust the expansion ratio.
[0026]
As described above, in the polyolefin-based foam molded by the core-back type injection molding apparatus using the foaming agent composition of the present invention under these conditions as a polyolefin-based resin, the appearance and the base material performance are of course further improved. It is preferable because the molding process is further easy. Therefore, the polyolefin-type foam which has the outstanding external appearance and base-material performance can be provided.
[0027]
In particular, in conventional foaming agents, polyolefin resins have a significantly lower melt viscosity than polystyrene resins, which causes defoaming or bubble breakage during foam molding, resulting in bubble destruction and the like. May occur and affect the appearance of the foam. On the other hand, in the present invention, when a higher saturated fatty acid such as stearic acid is used, the higher saturated fatty acid makes it possible to suppress the bursting of bubbles and the like. A polyolefin-based foam having material performance can be provided.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which a polyolefin foam is molded by a core back type injection molding apparatus using the foaming agent composition of the present invention to produce a door trim for an automobile will be described. Embodiment of this invention is a preferable example regarding implementation of this invention, and this invention is not limited to this embodiment.
[0029]
The total amount of the foaming agent composition is 57.0 parts by weight of sodium bicarbonate as a pyrolytic foaming agent, 28.5 parts by weight of monosodium citrate as a citrate, and 12 to 20 carbon atoms. As the saturated fatty acid salt, a foaming agent composition containing 5.5 parts by weight of lithium stearate and 9.0 parts by weight of talc as a cell nucleating agent is used.
[0030]
A polypropylene resin is prepared as a base material for the foaming agent. This polyolefin resin has a melting point of 140 ° C. or higher, an MFR (melt flow rate) of 10 or higher, preferably about MFR 50, a shear rate of 0.1 × 10 2 sec −1 to 0.5 at a temperature of 200 ° C. Any polyolefin resin may be used as long as it has a physical property of melt viscosity of 2.0 × 10 4 poises or less at × 10 2 sec −1 .
[0031]
Next, an injection molding apparatus having a desired mold cavity portion for foam molding to a desired door trim is prepared. A mixture (hereinafter simply referred to as a mixture) in which the polyolefin resin and the foaming agent composition are mixed by melting or the like is created at the injection portion. In this mixing method, the foaming agent composition is blended in advance with polypropylene resin, or the foaming agent is injected from the middle of a cylinder of an injection molding apparatus. Here, the initial plate thickness of the polypropylene diameter resin was 2.0 mm.
[0032]
This mixture is heated so that it may become 170-230 degreeC with the injection part (cylinder) of an injection molding apparatus. At this temperature, the mixture is injected from the injection part of the injection molding apparatus into the cavity part at a pressure of 10 to 200 MPa. The injection may be any injection that can be performed within 3 seconds from the start to the end of the injection.
[0033]
Within 3 seconds after completion of the injection, the mold core portion of the injection device adjacent to the cavity portion of the injection molding device is retracted in the direction of increasing the thickness of the cavity portion at a speed of 0.1 to 100 mm / sec. Let
[0034]
After the retreat, the mixture in the cavity is cooled at 50 ° C. for 1 s or more. After cooling, the mold is removed, and foaming of a door trim with a foam thickness of 3.0 mm and a foaming ratio of 1.5 is possible.
[0035]
This manufacturing method further prevents weld lines, avatars, flashes, and the like, thus eliminating the need for external repairs. In addition, the flow and moldability are improved compared to the conventional method, so that the molding process can be performed quickly and easily.
[0036]
Furthermore, the refinement of the bubbles became even more remarkable. In the prior art, the foaming ratio may be 1 to 1.5 times or more and the bubble diameter may be 200 to 1500 μm, or more, but in the present invention, the appearance is reduced by the uniform bubble distribution with a finer diameter, As a foam having good surface smoothness, a foam having a foaming ratio of 1.1 to 2.0 times and a cell diameter of 200 μm or less can be provided.
[0037]
As long as it is a polyolefin resin, it may be polyethylene, polybutylene, or the like. Furthermore, the polymer is not limited to a single olefin monomer, and may be a copolymer with a comonomer. In the case of such a copolymer, it is preferable to use ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene or the like as a comonomer.
Here, as the thermally decomposable foaming agent in the foaming agent composition, azodicarbonamide, benzenesulfonylhydrazide, N, N′-dinitrosopentamethylenetetramine, 5-phenyl-1,2, as well as other inorganic foaming agents are used. Organic chemical foaming agents such as 1,3,4-tetrazole and organic acid metal salts can also be used.
[0038]
The citrate in the foaming agent composition is not only other sodium salts such as trisodium citrate, but also potassium salts and lithium salts (however, except for C12-20 saturated fatty acid lithium salts). May be.
[0039]
The number of carbon atoms in the blowing agent composition: C12-20 saturated fatty acid salts are not limited to stearates, but include C12 lauric acid, C14 myristic acid, C16 palmitic acid, C20 arachidic acid, etc. May be a saturated fatty acid in the range of 12-20. Moreover, it is not restricted to those lithium salts, A sodium salt, potassium salt, etc. may be sufficient.
[0040]
The cell nucleating agent may be any conventional cell nucleating agent such as zinc white or silica.
[0041]
【Example】
Appearance evaluation and the like of an example in which an automobile door trim was molded using the foaming agent composition of the present invention and a comparative example in which an automotive door trim was molded using a conventional foaming agent composition were performed. The foaming agent composition of the example contains 57.0 parts by weight of sodium bicarbonate, 28.5 parts by weight of monosodium citrate, 5.5 parts by weight of lithium stearate, and 9.0 parts by weight of talc. . Moreover, the comparative example contains 78.0 parts by weight of sodium hydrogen carbonate, 13.5 parts by weight of monosodium citrate, 4.5 parts by weight of lithium stearate, and 9.0 parts by weight of talc. Except for the foaming agent composition, the examples and comparative examples are the same materials and manufacturing methods. Each foaming agent composition is mixed in polypropylene resin, and the core back type injection molding apparatus according to the above embodiment is used. The door trim was formed by the same manufacturing method as in Example 1.
[0042]
Appearance evaluation was performed for foaming ratio, moldability, weld line, flow, flash, and avatar. In addition, as for evaluation, the appearance was evaluated assuming that the appearance is more preferable as the symbols of ○, ◎, and right, with Δ being normal. The results are shown in Table 1 below.
[0043]
[Table 1]
[0044]
【The invention's effect】
By using the foaming agent composition of the present invention, the foams in the foam are made to have a finer and more uniform distribution, and the polyolefin foam having excellent appearance such as flatness and substrate performance, and the like are produced. And a foaming agent composition used for the production thereof.
Claims (4)
熱分解型発泡剤と、炭素数１２〜２０の飽和脂肪酸塩と、クエン酸塩と、気泡核剤とを有し、
前記発泡剤組成物の全重量に対し、
前記熱分解型発泡剤は炭酸水素ナトリウムを５７．０〜５７．５重量部、
前記炭素数１２〜２０の飽和脂肪酸塩はステアリン酸リチウムを５．５〜６．０重量部、
クエン酸塩はクエン酸モノナトリウムを２８．５〜２９．０重量部、
気泡核剤は亜鉛華、タルク、シリカのうち少なくともいずれか１つを８．５〜９．０重量部、
含むことを特徴とする発泡剤組成物。In a foaming agent composition that is mixed with a resin, foamed inside the resin by heat processing, and forms a foam of the resin,
A pyrolytic foaming agent, a saturated fatty acid salt having 12 to 20 carbon atoms, a citrate salt, and a cell nucleating agent;
For the total weight of the blowing agent composition,
The pyrolytic foaming agent is 57.0 to 57.5 parts by weight of sodium hydrogen carbonate ,
The saturated fatty acid salt having 12 to 20 carbon atoms contains 5.5 to 6.0 parts by weight of lithium stearate ,
The citrate is 28.5 to 29.0 parts by weight of monosodium citrate ,
The cell nucleating agent is 8.5 to 9.0 parts by weight of at least one of zinc white, talc, and silica ,
A foaming agent composition comprising:
前記ポリオレフィン系の樹脂は、融点１４０℃以上かつＭＦＲ１０以上であって、温度２００℃での剪断速度０．１〜５．０×１０2sec-1における溶融粘度が２．０×１０4ポイズ以下であること、
を特徴とするポリオレフィン系発泡体の製造方法。The thermally decomposable foaming agent in the foaming agent composition is prepared by mixing the foaming agent composition according to claim 1 with a polyolefin-based resin and subjecting the mixture to a thermal processing treatment in an injection molding apparatus. In the method for producing a polyolefin-based foam to be foamed and injection-molded,
The polyolefin-based resin has a melting point of 140 ° C. or higher and MFR 10 or higher, and a melt viscosity at a shear rate of 0.1 to 5.0 × 10 2 sec −1 at a temperature of 200 ° C. is 2.0 × 10 4 poise or less. Being
A process for producing a polyolefin-based foam.
前記射出発泡成形は、前記混合物を１７０〜２３０℃に加熱し、
前記加熱した混合物を、射出成形装置の射出部からキャビティ部へ１０〜２００ＭＰａの圧力で、射出開始から終了まで３秒以内に射出し、
前記射出終了後３秒以内に、前記キャビティ部に隣接する前記射出装置の金型コア部を０．１〜１００ｍｍ／seｃの速度で前記キャビティ部の厚さを大きくする方向へ後退させ、
前記後退以後に前記キャビティ内の前記混合物を４０〜８０℃で１ｓ以上冷却するコアバック式の射出発泡成形であること、
を特徴とするポリオレフィン系発泡体の製造方法。In the manufacturing method of the polyolefin-type foam described in Claim 2 ,
The injection foam molding heats the mixture to 170-230 ° C,
The heated mixture is injected within 3 seconds from the injection start to the end at a pressure of 10 to 200 MPa from the injection part of the injection molding apparatus to the cavity part,
Within 3 seconds after the end of the injection, the mold core portion of the injection device adjacent to the cavity portion is retracted in the direction of increasing the thickness of the cavity portion at a speed of 0.1 to 100 mm / sec,
A core-back type injection foam molding in which the mixture in the cavity is cooled at 40 to 80 ° C. for 1 second or longer after the retreating;
A process for producing a polyolefin-based foam.
前記ポリオレフィン系の樹脂は、融点１４０℃以上かつＭＦＲ１０以上であって、温度２００℃での剪断速度０．１〜５．０×１０2sec-1における溶融粘度が２．０×１０4ポイズ以下であること、
を特徴とするポリオレフィン系発泡体。A polyolefin system obtained by mixing the foaming agent composition according to claim 1 and a polyolefin-based resin, and foaming the thermally decomposable foaming agent in the foaming agent composition by thermal processing in an injection molding apparatus. In foam,
The polyolefin-based resin has a melting point of 140 ° C. or higher and MFR 10 or higher, and a melt viscosity at a shear rate of 0.1 to 5.0 × 10 2 sec −1 at a temperature of 200 ° C. is 2.0 × 10 4 poise or less. Being
Polyolefin foam characterized by the following.
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| JP6909394B2 (en) * | 2014-12-22 | 2021-07-28 | キョーラク株式会社 | Foam auxiliary material and foam molding method |
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