JP2004262983A - Crosslinked polyethylene resin foam and its production process - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、メタロセン触媒を用いて重合されたポリエチレン系樹脂を基材とする架橋ポリエチレン系樹脂発泡体及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来メタロセン触媒を用いて重合されたポリエチレン系樹脂による発泡成形技術が提案されている。（１）例えば特開平７−１８８４４２号公報には、メタロセン化合物を用いて得られたポリエチレン系樹脂の厚み１ｍｍのシートに電子線を照射、架橋した後、オーブン中で加熱発泡させるシートの発泡及び無架橋発泡が提案されている。（２）特開平７−２０７０５４号公報には、ポリプロピレンとメタロセン触媒を用いて重合されたポリエチレン系樹脂との混合物を前記と同様薄物シートの発泡法が提案されている。（３）特開平７−１７９６４０号公報には、メタロセン触媒を用いて重合されたポリエチレン系樹脂に（ａ）ハロゲン系難燃剤と三酸化アンチモン、又は（ｂ）赤リンと窒素化合物を添加混練し、薄物シートに発泡させる方法及び無架橋発泡法が提案されている。
【０００３】
（４）本出願人はメタロセン触媒を用いて重合されたポリエチレン系樹脂を基材とするＥＶＡ並の柔軟性と低密度ポリエチレン並の耐熱性を有する厚物架橋ポリエチレン系樹脂発泡体（特開平１０−２５９２６８号公報）及び（５）滑り止め効果、反発力、柔軟性に優れる架橋ポリエチレン系樹脂発泡体（特開２０００−２３９４２９）を提案した。
【０００４】
しかし、上記従来技術（１）〜（３）は、薄物シート発泡に関し、（４）及び（５）は、厚物発泡体に関するが、単一のメタロセン触媒を用いて重合されたポリエチレン系樹脂を基材とする加圧一段発泡法によるもので、発泡倍率２０倍までの発泡体を得ることしか出来ず、２０倍を越える高倍率の発泡体を得ることが出来なかった。
【０００５】
【発明が解決しようとする課題】
したがって本発明の目的は、上記従来技術の欠点を解消し、メタロセン触媒を用いて重合されたポリエチレン系樹脂を基材として、ノンスリップ性を有し、柔軟性に優れた高倍率で厚物の架橋ポリエチレン系樹脂発泡体及びその製造方法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明の架橋ポリエチレン系樹脂発泡体は、前記目的を達成するため、メタロセン触媒を用いて重合された数平均分子量（Ｍｎ）の異なる直鎖状低密度ポリエチレンを二種類以上ブレンドしてなるものである。メタロセン触媒を用いて重合されたポリエチレン系樹脂一種類のみを使用して発泡体を作る場合、樹脂の分子量分布の幅が狭く、２０倍以上の高倍率品を得ることができない。
【０００７】
本発明の架橋ポリエチレン系樹脂発泡体において、数平均分子量（Ｍｎ）の差が３，０００〜４０，０００である二種類のメタロセン触媒を用いて重合された直鎖状低密度ポリエチレンの混合比が１０：９０〜９０：１０であることが好ましい。数平均分子量（Ｍｎ）の差が３，０００未満の場合、分子量分布の差が少なく高倍率の発泡体になりにくい。一方、数平均分子量（Ｍｎ）の差が４０，０００以上になる組み合わせは、市販の樹脂ではない。混合比が、上記範囲外の場合、本発明の作用効果を得にくい。
【０００８】
本発明の架橋ポリエチレン連続気泡体において、メタロセン触媒を用いて重合された直鎖状低密度ポリエチレンが、示差走査熱量測定法によって得られる融解ピークを、３０〜９０℃の範囲に一つ以上有し、且つ１２０℃以上の範囲に有しないことが好ましい。この範囲から外れると、発泡体のノンスリップ性に劣ることになる。
【０００９】
本発明の架橋ポリエチレン連続気泡体の製造方法は、二種類以上のメタロセン触媒を用いて重合されたポリエチレン系樹脂をブレンドしたものに、発泡剤及び架橋剤を混和して発泡性樹脂組成物を得、該組成物を密閉金型中に充填して加圧下に加熱し、発泡剤及び架橋剤を部分的に分解させた後除圧して中間発泡体を得、次いで該中間発泡体を常圧下に加熱して残存する発泡剤及び架橋剤を分解させて発泡させる方法である。
【００１０】
本発明の製造方法において、数平均分子量（Ｍｎ）の差が３，０００〜４０，０００である二種類のメタロセン触媒を用いて重合された直鎖状低密度ポリエチレンの混合比が１０：９０〜９０：１０であることをが好ましい。数平均分子量（Ｍｎ）の差が３，０００未満の場合、分子量分布の差が少なく高倍率の発泡体になりにくい。一方、数平均分子量（Ｍｎ）の差が４０，０００以上になる組み合わせは、市販の樹脂ではない。混合比が、上記範囲外の場合、本発明の作用効果を得にくい。
【００１１】
本発明の製造方法において、メタロセン触媒を用いて重合されたポリエチレン系樹脂が、示差走査熱量測定法によって得られる融解ピークを、３０〜９０℃の範囲に一つ以上有し、且つ１２０℃以上の範囲に有しないことが好ましい。この範囲から外れると、発泡体のノンスリップ性に劣ることになる。
【００１２】
本発明において、示差走査熱量測定法によって得られる融解ピークとは、熱プレスによって成形した１００μｍのフィルムから約５ｍｇの試料を秤量し、それをセイコー電子工業株式会社製ＲＤＣ ２２０ ＤＳＣ装置にセットし、１７０℃に昇温してその温度で５分間保持した後、降温速度１０℃／分で−１０℃まで冷却する。次に、この試料を１分間保持した後、昇温速度１０℃／分で１７０℃まで昇温して測定を行う。−１０℃から１７０℃に昇温してＤＳＣ曲線を得た。その融解曲線より、緩やかなピーク及び鋭いピークを融解ピークとし、その時の温度を融解ピーク温度とした。
【００１３】
【発明の実施の形態】
以下、本発明に係る架橋ポリエチレン系樹脂発泡体の製造方法について具体的に説明する。
【００１４】
二種類以上のメタロセン触媒を用いて重合されたポリエチレン系樹脂をブレンドしたものに、発泡剤、発泡助剤、架橋剤及び必要に応じて充填剤を配合し、これを加熱したミキシングロール、加圧式ニーダー、押出機等によって混和する。その発泡性組成物を金型に充填し、これを加圧下に密閉し、１３０〜１６０℃、好ましくは１４０〜１５０℃で２０〜７０分間、好ましくは３５〜６０分間加熱し、発泡剤及び架橋剤を部分的に分解せしめて、除圧して金型より中間発泡体を取り出し、次に最終製品の形状、寸法に相当する密閉でない金型に上記中間発泡体を入れ、金型に設けたジャケットに熱媒を通して加熱し、１４０〜２００℃、好ましくは１５０〜１７０℃で、１０〜９０分間、好ましくは２０〜７０分間加熱せしめることにより、残存せる発泡剤を分解、発泡せしめ、さらに物性の均一な発泡体を得る。
【００１５】
本発明において使用されるメタロセン触媒を用いて重合されたポリエチレン系樹脂は、エチレンとＣ３ 〜Ｃ１８のαオレフィンとの共重合体から成り、α−オレフィンとしては、例えば、プロピレン、１−ブテン、１−ペンテン、１−ヘキセン、４−メチル−１−ペンテン、及び１−オクテン等が挙げられる。
【００１６】
一般に、メタロセン触媒とは、遷移金属をπ電子系の不飽和化合物で挟んだ構造の化合物であり、本発明では、チタン、ジルコニウム、ニッケル、パラジウム、ハフニウム、白金等の四価の遷移金属に、１または２以上のシクロペンタジエニル環またはその類縁体がリガンド（配位子）として存在する化合物が挙げられる。
【００１７】
リガンドとしては、シクロペンタジエニル環以外には、例えば、シコロペンタジエニルオリゴマー環、インデニル環、炭化水素基や置換炭化水素基或いは炭化水素―置換メタロイド基により置換されたシクロペンタジエニル環又はインデニル環等が挙げられる。このようなリガンド以外にも、例えば、塩素又は臭素の一価のアニオン又はニ価のアニオンキレート、炭化水素基、アルコキシド、アリールアルコキシド、アリールオキシド、アリールアミド、ホスフィド、アリールホスフィド等が遷移金属に配位結合されていてもよい。
【００１８】
本発明で使用しうる発泡剤は、ポリエチレン系樹脂の溶融温度以上の分解温度を有する化学発泡剤であり、例えばアゾ系化合物のアゾジカルボンアミド、バリウムアゾジカルボキシレート等；ニトロソ系化合物のジニトロソメチレンペンタテトラミン、トリニトロトリメチルトリアミン等；ヒドラジッド系化合物のｐ，ｐ‘−オキシビスベンゼンスルホニルヒゾラジッド等；スルホニルセミカルバジッド系化合物ｐ，ｐ‘−オキシビスベンゼンスルホニルセミカルバジッド、トルエンスルホニルセミカルバジッド等が挙げられる。
【００１９】
本発明で使用しうる架橋剤は、ポリエチレン系の流動開始温度以上の分解温度を有するものであって、加熱により分解され、遊離ラジカルを発生してその分子間もしくは分子内に架橋結合を生じせしめるラジカル発生剤であるところの有機過酸化物、例えばジクミルパーオキサイド、１，１−ジターシャリーブチルパーオキサイド、１，１−ジターシャリーブチルパーオキシー３，３，５−トリメチルシクロヘキサン、２，５−ジメチルー２，５−ジターシャリーブチルパーオキシヘキサン、２，５−ジメチルー２，５−ジターシャリーブチルパーオキシヘキシン、α、α―ジターシャリーブチルパーオキシイソプロピルベンゼン、ターシャリーブチルパーオキシケトン、ターシャリーブチルパーオキシベンゾエートなどがあるが、その時に使用される樹脂によって最適な有機過酸化物を選択しなければならない。
【００２０】
本発明において、発泡助剤を発泡剤の種類に応じて添加することができる。発泡助剤としては尿素を主成分とした化合物、酸化亜鉛、酸化鉛等の金属酸化物、サリチル酸、ステアリン酸等を主成分とする化合物、即ち高級脂肪酸あるいは高級脂肪酸の金属化合物などがある。
【００２１】
本発明において、樹脂組成物の物性の改良あるいは価格の低下を目的として、架橋結合に著しい悪影響を与えない配合剤（充填剤）、例えば酸化亜鉛、酸化チタン、酸化カルシウム、酸化マグネシウム、酸化ケイ素等の金属酸化物、炭酸マグネシウム、炭酸カルシウム等の炭酸塩、あるいはパルプ等の繊維物質、または各種染料、顔料並びに蛍光物質、その他常用のゴム配合剤等を必要に応じて添加することができる。
【００２２】
【実施例】
以下、実施例を示して本発明を更に具体的に説明するが、本発明は下記実施例により何等限定されるものではない。
【００２３】
実施例１
メタロセン触媒により重合された直鎖状低密度ポリエチレンＡ（商品名：アフィニティーＥＧ８１５０、数平均分子量（Ｍｎ）６３，０００、密度０．８６８ｇ／ｃｍ３、メルトフローレート０．５ｇ／１０分、ダウ・ケミカル日本製）５０重量部、メタロセン触媒により重合された直鎖状低密度ポリエチレンＢ（商品名：アフィニティーＥＧ８２００、数平均分子量（Ｍｎ）３２，０００、密度０．９２０ｇ／ｃｍ３、メルトフローレート５．０ｇ／１０分、ダウ・ケミカル日本製）５０重量部、アゾジカルボンアミド１７重量部、ステアリン酸亜鉛０．２重量部、ジクミルパーオキサイド０．９重量部を混練し、得られた発泡性樹脂組成物を１５０℃に加熱された油圧プレス上の密閉式金型（３６×１６０×１６０ｍｍ）に充填し、１００ｋｇ／ｃｍ２の圧力で密閉して５０分間加熱後除圧して、中間発泡体を得た。
【００２４】
該発泡体の線膨張率は１．６倍であった。
【００２５】
次いで、該成型物を加熱水蒸気の流路を周囲に設けた気密でない開閉式金属金型（１２０×５００×５００ｍｍ）の略中央に載置し、６．０ｋｇ／ｃｍ２の加熱水蒸気を該流路に流して５０分間加熱して残存する発泡剤及び架橋剤を分解して冷却後、発泡体を取り出した。
【００２６】
得られた発泡体の見掛け密度は３０ｋｇ／ｍ３で、二段発泡により発泡倍率３０倍を製造出来、滑り特性値０．７２ｋｇｆで、ノンスリップ性を有し、柔軟性に優れていた。
【００２７】
本発明において、滑り特性値とは、アクリル板の上に発泡体（サイズ：２０ｍｍ（厚み）ｘ５０ｍｍｘ５０ｍｍ）を置き、該発泡体の上に２２４ｇの錘を載置し、該発泡体をワイヤーで５０ｍｍ／分の速度で引張り、ワイヤーにかかるロードセルで測定するものである。
【００２８】
実施例２
樹脂の混合比を直鎖状低密度ポリエチレンＡ ２０重量部、直鎖状低密度ポリエチレンＢ ８０重量部に変えた以外は実施例１と同じ配合及び同じ条件で発泡させ、発泡体を得た。
【００２９】
得られた発泡体の見掛け密度は２９ｋｇ／ｍ３で、二段発泡により発泡倍率３０倍を製造出来、滑り特性値は、０．７６ｋｇｆで、ノンスリップ性を有し、柔軟性に優れていた。
【００３０】
実施例３
樹脂の混合比を直鎖状低密度ポリエチレンＡ ８０重量部、直鎖状低密度ポリエチレンＢ ２０重量部に変えた以外は実施例１と同じ配合及び同じ条件で発泡させ、発泡体を得た。
【００３１】
得られた発泡体の見掛け密度は３０ｋｇ／ｍ３で、二段発泡により発泡倍率３０倍を製造出来、滑り特性値は、０．７１ｋｇｆで、ノンスリップ性を有し、柔軟性に優れていた。
【００３２】
実施例４
直鎖状低密度ポリエチレンＢ ５０重量部、直鎖状低密度ポリエチレンＣ（商品名：カーネルＫＳ２４０、数平均分子量（Ｍｎ）３７，０００、密度０．８８０ｇ／ｃｍ３、メルトフローレート２．４ｇ／１０分、日本ポリケム製）５０重量を実施例１と同じ配合及び同じ条件で発泡させ、発泡体を得た。
【００３３】
得られた発泡体の見掛け密度は３０ｋｇ／ｍ３で、二段発泡により発泡倍率３０倍を製造出来、滑り特性値０．７５ｋｇｆで、ノンスリップ性を有し、柔軟性に優れていた。
【００３４】
比較例１
実施例１におけるメタロセン触媒により重合された直鎖状低密度ポリエチレンＡ（商品名：アフィニティーＥＧ８１５０、数平均分子量（Ｍｎ）６３，０００、密度０．８６８ｇ／ｃｍ３、メルトフローレート０．５ｇ／１０分、ダウ・ケミカル日本製）を１００重量にした以外は、すべて実施例１と同一条件で発泡させたが、満足のいく発泡倍率２０倍以上の発泡体は得られなかった。
【００３５】
比較例２
樹脂の混合比を直鎖状低密度ポリエチレンＡ ５重量部、直鎖状低密度ポリエチレンＢ ９５重量部に変えた以外は実施例１と同じ配合及び同じ条件で発泡させたが、満足のいく発泡倍率２０倍以上の発泡体は得られなかった。
【００３６】
比較例３
メタロセン触媒を用いて重合されたポリエチレン系樹脂の代わりに高圧法低密度ポリエチレン（ＭＦＲ １．１ｇ／１０分、密度０．９２ｇ／ｃｍ３）を１００重量部使用した以外は、実施例１と同じ配合及び同じ発泡条件で発泡体を得た。
【００３７】
得られた発泡体の見掛け密度３０ｋｇ／ｍ３、滑り特性値０．４０ｋｇｆで、ノンスリップ性が不足していた。
【００３８】
【表１】
【発明の効果】
本発明によれば、メタロセン触媒を用いて重合された平均分子量の異なる直鎖状低密度ポリエチレンを二種類以上ブレンドすることにより、柔軟性及びノンスリップ性に優れた、発泡倍率２０倍以上の厚物発泡体を製造することができる。
【００４０】
得られる発泡体は、断熱材、緩衝材、目地材、文具等に好適である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crosslinked polyethylene-based resin foam having a polyethylene-based resin polymerized using a metallocene catalyst as a base material, and a method for producing the same.
[0002]
[Prior art]
Conventionally, a foam molding technique using a polyethylene resin polymerized using a metallocene catalyst has been proposed. (1) For example, Japanese Patent Application Laid-Open No. 7-188442 discloses that a 1 mm thick sheet of a polyethylene resin obtained by using a metallocene compound is irradiated with an electron beam, crosslinked, and then heated and foamed in an oven. Non-crosslinked foaming has been proposed. (2) Japanese Patent Application Laid-Open No. 7-207054 proposes a method for foaming a thin sheet of a mixture of polypropylene and a polyethylene resin polymerized using a metallocene catalyst in the same manner as described above. (3) JP-A-7-179640 discloses that a (a) halogen-based flame retardant and antimony trioxide, or (b) red phosphorus and a nitrogen compound are added and kneaded to a polyethylene resin polymerized using a metallocene catalyst. In addition, a method of foaming into a thin sheet and a non-crosslinking foaming method have been proposed.
[0003]
(4) The present applicant has proposed a thick crosslinked polyethylene resin foam having flexibility similar to EVA and heat resistance comparable to low density polyethylene based on a polyethylene resin polymerized using a metallocene catalyst (Japanese Patent Application Laid-Open No. JP-A-259268) and (5) a crosslinked polyethylene resin foam (JP-A-2000-239429) having excellent anti-slip effect, resilience and flexibility.
[0004]
However, the above-mentioned prior arts (1) to (3) relate to thin sheet foaming, and (4) and (5) relate to thick foams, but use a polyethylene resin polymerized using a single metallocene catalyst. Due to the single-stage pressure foaming method used as a base material, a foam having an expansion ratio of up to 20 times could only be obtained, and a foam having a high magnification exceeding 20 times could not be obtained.
[0005]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to use a polyethylene-based resin polymerized by using a metallocene catalyst as a base material, have a non-slip property, and have excellent flexibility to cross-link a thick material at a high magnification. An object of the present invention is to provide a polyethylene resin foam and a method for producing the same.
[0006]
[Means for Solving the Problems]
The crosslinked polyethylene resin foam of the present invention is obtained by blending two or more kinds of linear low-density polyethylenes having different number average molecular weights (Mn) polymerized using a metallocene catalyst in order to achieve the above object. is there. When a foam is made using only one kind of polyethylene resin polymerized using a metallocene catalyst, the width of the molecular weight distribution of the resin is narrow, and a high magnification product of 20 times or more cannot be obtained.
[0007]
In the crosslinked polyethylene resin foam of the present invention, the mixing ratio of the linear low-density polyethylene polymerized using two types of metallocene catalysts having a difference in number average molecular weight (Mn) of 3,000 to 40,000 is The ratio is preferably from 10:90 to 90:10. When the difference in the number average molecular weight (Mn) is less than 3,000, the difference in the molecular weight distribution is small, and it is difficult to produce a high-magnification foam. On the other hand, a combination having a difference in number average molecular weight (Mn) of 40,000 or more is not a commercially available resin. If the mixing ratio is outside the above range, it is difficult to obtain the effects of the present invention.
[0008]
In the crosslinked polyethylene open-cell foam of the present invention, the linear low-density polyethylene polymerized using a metallocene catalyst has one or more melting peaks obtained by differential scanning calorimetry in the range of 30 to 90 ° C. , And preferably not in the range of 120 ° C. or higher. If it is out of this range, the non-slip property of the foam is inferior.
[0009]
The method for producing a crosslinked polyethylene open-cell foam of the present invention provides a foamable resin composition by blending a polyethylene-based resin polymerized using two or more metallocene catalysts with a foaming agent and a crosslinking agent. The composition is filled in a closed mold and heated under pressure to partially decompose the foaming agent and the cross-linking agent and then depressurized to obtain an intermediate foam. This is a method in which the remaining foaming agent and cross-linking agent are heated to decompose and foam.
[0010]
In the production method of the present invention, the mixing ratio of linear low-density polyethylene polymerized using two types of metallocene catalysts having a difference in number average molecular weight (Mn) of 3,000 to 40,000 is 10:90 to Preferably it is 90:10. When the difference in the number average molecular weight (Mn) is less than 3,000, the difference in the molecular weight distribution is small, and it is difficult to produce a high-magnification foam. On the other hand, a combination having a difference in number average molecular weight (Mn) of 40,000 or more is not a commercially available resin. If the mixing ratio is outside the above range, it is difficult to obtain the effects of the present invention.
[0011]
In the production method of the present invention, the polyethylene resin polymerized using the metallocene catalyst has one or more melting peaks obtained by differential scanning calorimetry in the range of 30 to 90 ° C, and 120 ° C or more. It is preferable not to have it in the range. If it is out of this range, the non-slip property of the foam is inferior.
[0012]
In the present invention, with the melting peak obtained by differential scanning calorimetry, a sample of about 5 mg is weighed from a 100 μm film formed by hot pressing, and set on an RDC 220 DSC device manufactured by Seiko Electronic Industry Co., Ltd. After the temperature is raised to 170 ° C. and maintained at that temperature for 5 minutes, it is cooled to −10 ° C. at a rate of 10 ° C./min. Next, after holding the sample for 1 minute, the temperature is increased to 170 ° C. at a rate of 10 ° C./min, and the measurement is performed. The temperature was raised from -10 ° C to 170 ° C to obtain a DSC curve. From the melting curve, a gentle peak and a sharp peak were defined as a melting peak, and the temperature at that time was defined as a melting peak temperature.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the method for producing the crosslinked polyethylene resin foam according to the present invention will be specifically described.
[0014]
A foaming agent, a foaming aid, a cross-linking agent and, if necessary, a filler are blended with a blend of a polyethylene resin polymerized using two or more metallocene catalysts, and the resulting mixture is heated with a mixing roll. Mix with a kneader, extruder or the like. The foamable composition is filled in a mold, sealed under pressure, and heated at 130 to 160 ° C., preferably 140 to 150 ° C. for 20 to 70 minutes, preferably 35 to 60 minutes to form a foaming agent and a crosslinking agent. The agent is partially decomposed, the pressure is removed, the intermediate foam is taken out of the mold, and then the intermediate foam is placed in an unsealed mold corresponding to the shape and dimensions of the final product, and the jacket provided in the mold The mixture is heated at 140 to 200 ° C., preferably 150 to 170 ° C., for 10 to 90 minutes, preferably 20 to 70 minutes to decompose and foam the remaining foaming agent, and to further uniformize the physical properties. A good foam.
[0015]
Polyethylene resin polymerized using a metallocene catalyst used in the present invention comprises a copolymer of α-olefins and C 3 -C 18, as α- olefins, for example, propylene, 1-butene , 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like.
[0016]
In general, a metallocene catalyst is a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds.In the present invention, titanium, zirconium, nickel, palladium, hafnium, tetravalent transition metals such as platinum, Examples include compounds in which one or more cyclopentadienyl rings or analogs thereof are present as ligands (ligands).
[0017]
As the ligand, other than a cyclopentadienyl ring, for example, a cyclopentadienyl oligomer ring, an indenyl ring, a cyclopentadienyl ring substituted with a hydrocarbon group or a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group, or And an indenyl ring. In addition to such ligands, for example, monovalent anions or divalent anion chelates of chlorine or bromine, hydrocarbon groups, alkoxides, arylalkoxides, aryloxides, arylamides, phosphides, arylphosphides, etc. It may be coordinated.
[0018]
The blowing agent that can be used in the present invention is a chemical blowing agent having a decomposition temperature equal to or higher than the melting temperature of the polyethylene resin, such as azo compounds such as azodicarbonamide and barium azodicarboxylate; and nitroso compounds such as dinitroso. Methylenepentatetramine, trinitrotrimethyltriamine and the like; hydrazide-based compounds such as p, p'-oxybisbenzenesulfonylhydrazide; and sulfonylsemicarbazide-based compounds p, p'-oxybisbenzenesulfonylsemicarbazide and toluenesulfonylsemi Carbazide and the like.
[0019]
The crosslinking agent that can be used in the present invention has a decomposition temperature equal to or higher than the flow initiation temperature of a polyethylene system, and is decomposed by heating to generate free radicals, thereby causing cross-linking between or within the molecules. Organic peroxides which are radical generators, for example, dicumyl peroxide, 1,1-ditert-butyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, 2,5- Dimethyl-2,5-di-tert-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexyne, α, α-di-tert-butylperoxyisopropylbenzene, tert-butylperoxyketone, tertiary Butyl peroxybenzoate, etc. The optimum organic peroxide must be selected depending on the resin used.
[0020]
In the present invention, a foaming aid can be added according to the type of the foaming agent. Examples of the foaming aid include compounds mainly containing urea, metal oxides such as zinc oxide and lead oxide, compounds mainly containing salicylic acid, stearic acid and the like, that is, higher fatty acids and metal compounds of higher fatty acids.
[0021]
In the present invention, for the purpose of improving the physical properties of the resin composition or reducing the price, a compounding agent (filler) that does not significantly affect cross-linking, for example, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, silicon oxide, etc. Metal oxides, carbonates such as magnesium carbonate and calcium carbonate, or fibrous substances such as pulp, or various dyes, pigments, fluorescent substances, and other commonly used rubber compounding agents, if necessary.
[0022]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.
[0023]
Example 1
Linear low density polyethylene A polymerized with a metallocene catalyst (trade name: Affinity EG8150, number average molecular weight (Mn) 63,000, density 0.868 g / cm 3 , melt flow rate 0.5 g / 10 min, Dow Chemical Japan, 50 parts by weight, linear low density polyethylene B polymerized with a metallocene catalyst (trade name: Affinity EG8200, number average molecular weight (Mn) 32,000, density 0.920 g / cm 3 , melt flow rate 5) 0.0 g / 10 min, 50 parts by weight of Dow Chemical Japan), 17 parts by weight of azodicarbonamide, 0.2 parts by weight of zinc stearate, and 0.9 parts by weight of dicumyl peroxide. The resin composition was filled into a closed mold (36 × 160 × 160 mm) on a hydraulic press heated to 150 ° C. 0 kg / in depressurized after heating for 50 minutes and sealed with a pressure of cm 2, and obtain an intermediate foam.
[0024]
The linear expansion coefficient of the foam was 1.6 times.
[0025]
Next, the molded product is placed substantially at the center of a non-hermetic open / close type metal mold (120 × 500 × 500 mm) provided with a heating steam flow path therearound, and 6.0 kg / cm 2 of heating steam is applied to the molding. The foam was heated by flowing through a channel for 50 minutes to decompose the remaining foaming agent and cross-linking agent, and then cooled.
[0026]
The foam obtained had an apparent density of 30 kg / m 3 , a foaming ratio of 30 times could be produced by two-stage foaming, a slip property of 0.72 kgf, a non-slip property, and excellent flexibility.
[0027]
In the present invention, the slip characteristic value means that a foam (size: 20 mm (thickness) x 50 mm x 50 mm) is placed on an acrylic plate, a 224 g weight is placed on the foam, and the foam is placed on a 50 mm wire. / Minute, and measured by a load cell applied to the wire.
[0028]
Example 2
Foaming was performed under the same composition and under the same conditions as in Example 1 except that the mixing ratio of the resin was changed to 20 parts by weight of linear low-density polyethylene A and 80 parts by weight of linear low-density polyethylene B.
[0029]
The foam obtained had an apparent density of 29 kg / m 3 , an expansion ratio of 30 times could be produced by two-stage foaming, a slip property value of 0.76 kgf, a non-slip property, and excellent flexibility.
[0030]
Example 3
A foam was obtained by foaming under the same composition and under the same conditions as in Example 1 except that the mixing ratio of the resin was changed to 80 parts by weight of the linear low-density polyethylene A and 20 parts by weight of the linear low-density polyethylene B.
[0031]
The foam obtained had an apparent density of 30 kg / m 3 , a foaming ratio of 30 times could be produced by two-stage foaming, a slip property value of 0.71 kgf, a non-slip property, and excellent flexibility.
[0032]
Example 4
50 parts by weight of linear low-density polyethylene B, linear low-density polyethylene C (trade name: Kernel KS240, number average molecular weight (Mn) 37,000, density 0.880 g / cm 3 , melt flow rate 2.4 g / 50 weight parts (manufactured by Nippon Polychem Co., Ltd. for 10 minutes) were foamed under the same composition and under the same conditions as in Example 1 to obtain a foam.
[0033]
The foam obtained had an apparent density of 30 kg / m 3 , a foaming ratio of 30 times could be produced by two-stage foaming, a slip property of 0.75 kgf, a non-slip property, and excellent flexibility.
[0034]
Comparative Example 1
Linear low-density polyethylene A polymerized with a metallocene catalyst in Example 1 (trade name: Affinity EG8150, number average molecular weight (Mn) 63,000, density 0.868 g / cm 3 , melt flow rate 0.5 g / 10) All the components were foamed under the same conditions as in Example 1 except that the weight of Dow Chemical Japan Ltd.) was changed to 100 weight, but a satisfactory foam having an expansion ratio of 20 times or more was not obtained.
[0035]
Comparative Example 2
Foaming was carried out under the same composition and under the same conditions as in Example 1 except that the mixing ratio of the resin was changed to 5 parts by weight of linear low density polyethylene A and 95 parts by weight of linear low density polyethylene B. A foam having a magnification of 20 times or more was not obtained.
[0036]
Comparative Example 3
Same as Example 1 except that 100 parts by weight of a high-pressure low-density polyethylene (MFR 1.1 g / 10 min, density 0.92 g / cm 3 ) was used instead of the polyethylene resin polymerized using the metallocene catalyst. A foam was obtained under the same blending and foaming conditions.
[0037]
The obtained foam had an apparent density of 30 kg / m 3 and a slip property value of 0.40 kgf, and lacked non-slip properties.
[0038]
[Table 1]
【The invention's effect】
According to the present invention, by blending two or more kinds of linear low-density polyethylenes having different average molecular weights polymerized using a metallocene catalyst, a thick material having an expansion ratio of 20 times or more, excellent in flexibility and non-slip properties. Foams can be manufactured.
[0040]
The obtained foam is suitable for a heat insulating material, a cushioning material, a joint material, a stationery, and the like.
Claims (6)
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| JP2003052367A JP3963455B2 (en) | 2003-02-28 | 2003-02-28 | Cross-linked polyethylene resin foam and production method thereof |
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| JP2003052367A JP3963455B2 (en) | 2003-02-28 | 2003-02-28 | Cross-linked polyethylene resin foam and production method thereof |
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| JP2004262983A true JP2004262983A (en) | 2004-09-24 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10301447B2 (en) | 2009-07-14 | 2019-05-28 | Toray Plastics (America), Inc. | Crosslinked polyolefin foam sheet with exceptional softness, haptics, moldability, thermal stability and shear strength |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10301447B2 (en) | 2009-07-14 | 2019-05-28 | Toray Plastics (America), Inc. | Crosslinked polyolefin foam sheet with exceptional softness, haptics, moldability, thermal stability and shear strength |
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