JP2008239674A - Method for producing resin composition for polyolefin-based resin crosslinked foam - Google Patents
Method for producing resin composition for polyolefin-based resin crosslinked foam Download PDFInfo
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本発明は、発泡剤が均一に分散し、発泡体内部の粗気泡や発泡体表層部のピンホールが少ない、酢酸ビニル系樹脂架橋発泡体の製造に関するものである。 The present invention relates to the production of a vinyl acetate-based resin cross-linked foam in which a foaming agent is uniformly dispersed, and there are few coarse bubbles in the foam and pinholes in the foam surface layer.
酢酸ビニル系樹脂発泡体は、優れた柔軟性、クッション性、緩衝性、耐水性、耐化学薬品性等を有することから、クーラー等電化製品の断熱剤、高級製品の包装緩衝剤、容器のパッキン、粘着テープあるいは、パイプ形状に加工して調理機器の配管断熱剤等幅広く使用されてきている。
酢酸ビニル系発泡体の主用途であるパッキンや粘着テープについては、柔軟性や伸びを向上しつつ、成型時に耐えうる強度が要求され、なおかつスライス用途や延伸による極薄化の製品が求められている。極薄化に伴い、外観欠点や表面の微細なピンホール、内部のやや粗い気泡（粗気泡）に対しても客先の要求品質が高まってきている。
Since vinyl acetate resin foam has excellent flexibility, cushioning, cushioning, water resistance, chemical resistance, etc., it can be used for heat insulation of electrical appliances such as coolers, packaging cushioning for high-end products, and packing for containers. It has been used widely, such as adhesive tapes or pipe insulation for cooking equipment processed into a pipe shape.
For packing and adhesive tape, which are the main uses of vinyl acetate foam, there is a demand for strength that can withstand molding while improving flexibility and elongation, and for slicing and ultra-thin products by stretching. Yes. Along with the ultra-thinning, customer's required quality is increasing even for appearance defects, fine pinholes on the surface, and slightly rough bubbles (coarse bubbles) inside.
エチレン-酢酸ビニル樹脂とポリオレフィン樹脂を混合している酢酸ビニル系樹脂発泡体は、酢酸ビニル濃度が高くなると柔軟性及び伸びが向上する。逆に低密度ポリエチレン等のポリオレフィン樹脂の濃度が増えるほど、強度が増し柔軟性及び伸びが低下する。これらのことからエチレン−酢酸ビニル共重合体樹脂にポリエチレン樹脂を混合して、強度・伸び・柔軟性を調整している。 The vinyl acetate-based resin foam in which an ethylene-vinyl acetate resin and a polyolefin resin are mixed improves flexibility and elongation as the vinyl acetate concentration increases. Conversely, as the concentration of polyolefin resin such as low density polyethylene increases, the strength increases and the flexibility and elongation decrease. For these reasons, polyethylene resin is mixed with ethylene-vinyl acetate copolymer resin to adjust strength, elongation and flexibility.
エチレン−酢酸ビニル共重合体とポリオレフィン系樹脂の架橋発泡体は、通常粉体の発泡剤と原料樹脂をブレンドし、押出機でシート状に成形し、架橋を施し、加熱発泡をしている。しかしながらエチレン−酢酸ビニル共重合体樹脂とポリオレフィン系樹脂の融点が異なることから融点の低いエチレン−酢酸ビニル樹脂やオリゴマーに発泡剤が最初にとけ込み、融点の高いポリオレフィン樹脂の界面およびシリンダーや口金との接触面で発泡剤の分散不良により高濃度の発泡剤を含んだエチレン−酢酸ビニル共重合体樹脂やオリゴマー、またそれらの混合物、発泡剤凝集物がシート中に混入するため、発泡後発泡体表面上にピンホールが発生したり、発泡体内部に粗気泡が発生する。
また、微粉の発泡剤は、表面活性が高く２次凝集を起こしやすいことと、水分等の吸着により凝集しやすく、混練不十分により発泡体表面上のピンホールや発泡体内部に粗気泡が発生していた。
A cross-linked foam of an ethylene-vinyl acetate copolymer and a polyolefin-based resin is usually obtained by blending a powder foaming agent and a raw material resin, forming a sheet with an extruder, performing cross-linking, and performing heat foaming. However, since the melting point of the ethylene-vinyl acetate copolymer resin and the polyolefin resin are different, the blowing agent first melts into the ethylene-vinyl acetate resin or oligomer having a low melting point, and the interface between the high melting point polyolefin resin and the cylinder or die. Foam after foaming because ethylene-vinyl acetate copolymer resins and oligomers containing a high concentration of foaming agent due to poor dispersion of foaming agent on the contact surface of the resin, and their mixtures and foaming agent aggregates are mixed in the sheet. Pinholes are generated on the surface and coarse bubbles are generated inside the foam.
The fine foaming agent has high surface activity and tends to cause secondary agglomeration, and is easy to agglomerate due to adsorption of moisture, etc., and inadequate kneading generates coarse bubbles in the pinhole on the foam surface and inside the foam. Was.
この対策として発泡剤を比較的濃い状態となるように樹脂と発泡剤を混練したマスターバッチをあらかじめ製造しておき、所望の発泡倍率となるよう樹脂成分と混合することが行われているが、必ずしも発泡剤の分散が良好でなく、ピンホールや粗気泡の問題は、解決していない。 As a countermeasure, a master batch in which a resin and a foaming agent are kneaded so that the foaming agent is in a relatively dark state is manufactured in advance, and mixing with a resin component to achieve a desired expansion ratio is performed. The dispersion of the foaming agent is not always good, and the problems of pinholes and coarse bubbles are not solved.
エチレン−プロピレン−ジエン共重合体ゴムと、エチレン−酢酸ビニル共重合体とに発泡剤が大幅に濃い状態となるようにして混練したマスターバッチ組成物をあらかじめ製造しておき、それと結晶性ポリオレフィン（又は結晶性ポリオレフィンと、エチレン−プロピレン−ジエン共重合体ゴムと、エチレン−酢酸ビニル共重合体）とを所望の発泡倍率となるように混合して架橋発泡体用組成物とし、この組成物から得られる成形体を放射線架橋した後、加熱発泡する特許が提案されているが（特許文献１）、大幅に濃い状態では、ポリオレフィンとの分散性が悪い。
融点の高いポリオレフィンと発泡剤を最初に混練しマスターバッチを製造する際、ポリオレフィンの融点以上に温度を上げる必要があり、発泡剤が分解し易い。また、剪断発熱により能力が上げられないため、コストがかかる問題が発生する。
A master batch composition prepared by kneading an ethylene-propylene-diene copolymer rubber and an ethylene-vinyl acetate copolymer so that the foaming agent is in a deeply concentrated state is prepared in advance, and a crystalline polyolefin ( Alternatively, a crystalline polyolefin, an ethylene-propylene-diene copolymer rubber, and an ethylene-vinyl acetate copolymer) are mixed so as to obtain a desired foaming ratio to obtain a composition for a crosslinked foam. A patent has been proposed in which the resulting molded article is heated and foamed after radiation cross-linking (Patent Document 1). However, in a considerably deep state, dispersibility with polyolefin is poor.
When a masterbatch is produced by first kneading a polyolefin having a high melting point and a foaming agent, the temperature needs to be raised above the melting point of the polyolefin, and the foaming agent is easily decomposed. In addition, since the capacity cannot be increased by shearing heat generation, there is a problem that costs are increased.
分散不良対策として、押出機としては、単軸押出機から多軸押出機への移行やスクリュー径の径大化およびスクリュー形状の見直し、スクリューにピン植込、ダルメージ取付けによる混練性の強化が行われているが、工程を変更することはコストがかかること、少量他品種により全ての樹脂に万能なスクリューを選定することが困難なこと、発泡剤の分解温度以下で溶融混練を行う必要があるため、剪断をかけすぎると発泡剤が分解してしまう問題が発生し、分散不良による粗気泡やピンホールの問題は、解決していない。
従って本発明の目的は、発泡剤が均一に分散し、発泡剤の凝集による粗気泡が少ない酢酸ビニル系樹脂発泡体の製造方法を提供することにある。
Accordingly, an object of the present invention is to provide a method for producing a vinyl acetate resin foam in which a foaming agent is uniformly dispersed and there are few coarse bubbles due to aggregation of the foaming agent.
従って本発明の目的は、発泡剤が均一に分散し、発泡剤の凝集による粗気泡が少ない酢酸ビニル系樹脂発泡体の製造方法を提供することにある。 Accordingly, an object of the present invention is to provide a method for producing a vinyl acetate resin foam in which a foaming agent is uniformly dispersed and there are few coarse bubbles due to aggregation of the foaming agent.
上記課題を解決するために本発明は、
（１）エチレン−酢酸ビニル共重合体（Ａ）１００重量部に対して発泡剤を1５〜１００重量部配合し、前記エチレン−酢酸ビニル共重合体（Ａ）の融点から融点よりも５０℃低い温度で剪断力をかけながら溶融混練することにより得られる発泡剤含有マスターバッチ（Ｂ）であって、
ポリオレフィン系樹脂（Ｃ）１０〜９０重量％と前記発泡剤含有マスターバッチーバッチ（Ｂ）９０〜１０重量％からなる樹脂成分（Ｄ）に対して、前記ポリオレフィン系樹脂（Ｃ）の融点から融点よりも５０℃低い温度で剪断力をかけながら溶融混練することを特徴とする、ポリオレフィン系樹脂架橋発泡体用樹脂組成物の製造方法。
（２）樹脂成分（Ｄ）の混錬温度が、エチレン−酢酸ビニル共重合体（Ａ）の混錬温度よりも高いことを特徴とする、（１）に記載のポリオレフィン系樹脂架橋発泡体用樹脂組成物の製造方法。
（３）（１）又は（２）に記載の製造方法により得られることを特徴とする、ポリオレフィン系樹脂架橋発泡体用樹脂組成物。
を提供する。
In order to solve the above problems, the present invention
(1) 15 to 100 parts by weight of a foaming agent is blended with 100 parts by weight of the ethylene-vinyl acetate copolymer (A), and the melting point of the ethylene-vinyl acetate copolymer (A) is 50 ° C. lower than the melting point. A foaming agent-containing masterbatch (B) obtained by melt-kneading while applying a shearing force at a temperature,
From the melting point of the polyolefin resin (C) to the resin component (D) comprising 10 to 90% by weight of the polyolefin resin (C) and 90 to 10% by weight of the foaming agent-containing masterbatch batch (B). A method for producing a resin composition for a polyolefin-based resin cross-linked foam, which is melt-kneaded while applying a shearing force at a temperature lower by 50 ° C.
(2) The kneading temperature of the resin component (D) is higher than the kneading temperature of the ethylene-vinyl acetate copolymer (A), and for the polyolefin-based resin crosslinked foam according to (1) A method for producing a resin composition.
(3) A resin composition for a polyolefin-based resin crosslinked foam, which is obtained by the production method according to (1) or (2).
I will provide a.
本発明によれば、発泡剤が均一に分散し、発泡体内部の粗気泡や発泡体表層部のピンホールが少ない、酢酸ビニル系樹脂架橋発泡体を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, a foaming agent can disperse | distribute uniformly and there can be provided the vinyl acetate type resin cross-linked foam with few coarse bubbles inside a foam, and the pinhole of a foam surface layer part.
本発明で使用するエチレン−酢酸ビニル共重合体（Ａ）は、酢酸ビニルの含有率が４．５〜５０重量％、好ましくは１０〜３５重量％のエチレン系共重合体である。酢酸ビニル濃度が４．５重量％未満では、酢酸ビニル発泡体に必要な柔軟性や伸びを出すために、エチレン−酢酸ビニル共重合体（Ａ）を多量に添加する必要がありコストアップとなる。酢酸ビニル濃度が５０重量％以上では、融点が低下し、工程上「おこし」等の不具合が発生する。エチレン−酢酸ビニル共重合体（Ａ）の融点は、５０℃〜１１０℃、好ましくは６０℃〜１００℃である。酢ビ濃度と融点は、おおよそ相関があり、酢ビ濃度が４．５〜１０％では１１０℃〜１００℃で酢ビ濃度が１０〜３５重量％では、１００〜６０℃、酢ビ濃度が３５〜５０重量％では、６０〜５０℃である。融点が低い場合は、工程上「おこし」等の不具合が発生し、融点が高い場合は、溶融混練時、剪断発熱により発泡剤が分解する。このようなエチレン−酢酸ビニル共重合体（Ａ）のＪＩＳ−Ｋ−６７６０に基づくＭＦＲは、規定するものではないが、１〜２５ｇ/１０ 分が好ましい。ＭＦＲが１未満では溶融混練時、剪断発熱により発泡剤が分解する。ＭＦＲが２５以上では、粘度が低く十分な混練が出来ない。 The ethylene-vinyl acetate copolymer (A) used in the present invention is an ethylene copolymer having a vinyl acetate content of 4.5 to 50% by weight, preferably 10 to 35% by weight. When the vinyl acetate concentration is less than 4.5% by weight, it is necessary to add a large amount of the ethylene-vinyl acetate copolymer (A) to increase the flexibility and elongation required for the vinyl acetate foam, resulting in an increase in cost. . When the vinyl acetate concentration is 50% by weight or more, the melting point is lowered, and problems such as “striking” occur in the process. The melting point of the ethylene-vinyl acetate copolymer (A) is 50 ° C to 110 ° C, preferably 60 ° C to 100 ° C. The vinyl chloride concentration and the melting point are roughly correlated. When the vinyl chloride concentration is 4.5 to 10%, 110 ° C to 100 ° C, and when the vinyl chloride concentration is 10 to 35% by weight, the vinyl acetate concentration is 35 ° C. It is 60-50 degreeC in -50weight%. When the melting point is low, problems such as “koshi” occur in the process, and when the melting point is high, the foaming agent is decomposed by shearing heat generation during melt kneading. Although MFR based on JIS-K-6760 of such an ethylene-vinyl acetate copolymer (A) is not specified, 1 to 25 g / 10 min is preferable. When the MFR is less than 1, the foaming agent is decomposed by shearing heat generation during melt kneading. When the MFR is 25 or more, the viscosity is low and sufficient kneading cannot be performed.
本発明のポリオレフィン系樹脂（Ｃ）は、オレフィン系炭化水素の単独重合体または共重合体であって、例えば、ポリエチレン、ポリプロピレン、エチレン−プロピレン共重合体、エチレンとブテン、ペンテン等のα−オレフィンとの共重合体、エチレン−アクリル酸共重合体、エチレン−アクリル酸エステル共重合体、エチレン−スチレン共重合体、エチレン−プロピレン−スチレン−ブタジエン共重合体、エチレン−塩化ビニル共重合体、及びこれらの２種以上の混合物などが挙げられる。これらのオレフィン系樹脂には、グラフトのような化学的修飾が施されていてもよい。 The polyolefin resin (C) of the present invention is an olefinic hydrocarbon homopolymer or copolymer, for example, an α-olefin such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene and butene, pentene, etc. Copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-styrene copolymer, ethylene-propylene-styrene-butadiene copolymer, ethylene-vinyl chloride copolymer, and A mixture of two or more of these may be used. These olefin resins may be subjected to chemical modification such as grafting.
上述したポリオレフィン系樹脂（Ｃ）としては、ポリエチレン、ポリプロピレンが好ましく、ポリエチレン系樹脂およびポリプロピレン系樹脂の少なくとも１種類を含有することが好ましい。 As said polyolefin resin (C), polyethylene and a polypropylene are preferable and it is preferable to contain at least 1 sort (s) of a polyethylene resin and a polypropylene resin.
本発明のポリオレフィン系樹脂（Ｃ）としてポリエチレン系樹脂を使用する場合は、ポリエチレン単独重合体（低密度ポリエチレン、高密度ポリエチレン、線状低密度ポリエチレン、超高分子量ポリエチレン等）やエチレンを主成分とする共重合体、あるいはこれらの２種以上の混合物が用いられる。エチレン共重合体としては、エチレン単位を５０重量％以上含有するエチレン−α−オレフィン共重合体が好ましい。α−オレフィンとしては、例えば、１−ブテン、１−ペンテン、１−ヘキセン、４−メチル−１−ペンテン、１−オクテンなどが挙げられる。 When a polyethylene resin is used as the polyolefin resin (C) of the present invention, a polyethylene homopolymer (low density polyethylene, high density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, etc.) or ethylene is the main component. Or a mixture of two or more of these. As the ethylene copolymer, an ethylene-α-olefin copolymer containing 50% by weight or more of ethylene units is preferable. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like.
本発明のポリオレフィン系樹脂（Ｃ）としてポリエチレン系樹脂を使用する場合は、密度が８６０〜９７５ｋｇ／ｍ３ 、ＭＦＲが０．５〜５０ｇ／１０分の範囲内にあるものが好ましく用いられる。なお、かかるＭＦＲはＪＩＳ−Ｋ−６７６０に基づいて測定した。ポリエチレン系樹脂の中でも、密度が９２０〜９４０ｋｇ／ｍ３ 、ＭＦＲが１〜１５ｇ／１０分、融点が１００〜１３０℃の低密度ポリエチレンが最も好ましく用いられる。 When a polyethylene resin is used as the polyolefin resin (C) of the present invention, those having a density of 860 to 975 kg / m 3 and an MFR of 0.5 to 50 g / 10 min are preferably used. In addition, this MFR was measured based on JIS-K-6760. Among the polyethylene resins, low density polyethylene having a density of 920 to 940 kg / m 3 , an MFR of 1 to 15 g / 10 minutes, and a melting point of 100 to 130 ° C. is most preferably used.
本発明のポリオレフィン系樹脂（Ｃ）としてポリプロピレン系樹脂を使用する場合は、一般に立体規則性のよい結晶性ポリプロピレンの単独重合体、プロピレンの含有率が５０重量％以上、好ましくは７０重量％以上のポリプロピレン共重合体、あるいはこれらの２種以上の混合物が用いられる。ポリプロピレン共重合体としては、ポリプロピレンとα−オレフィンとの共重合体を挙げることができる。α−オレフィンとしては、例えば、１−ブテン、１−ペンテン、１−ヘキセン、４−メチル−１−ペンテン、１−オクテンなどが挙げられる。また、プロピレン−エチレン共重合体も使用することができる。ポリプロピレン系樹脂は、ＭＦＲが０．５〜２０ｇ／１０分、融点が１３０〜１７０℃の範囲内にあるものが好ましく用いられる。なお、かかるＭＦＲはＪＩＳ Ｋ７２１０に基づいて測定した。これらのポリプロピレン系樹脂の中でも、エチレン含有率が１〜５重量％、融点が１３５〜１５５℃、ＭＦＲが０．５〜５．０ｇ／１０分のランダムポリプロピレン、あるいはエチレン含有率が５〜１０重量％、融点が１５０〜１６５℃、ＭＦＲが３．０〜７．０ｇ／１０分のブロックポリプロピレンが特に好ましく用いられる。 When a polypropylene resin is used as the polyolefin resin (C) of the present invention, generally a homopolymer of crystalline polypropylene having good stereoregularity, the propylene content is 50% by weight or more, preferably 70% by weight or more. A polypropylene copolymer or a mixture of two or more of these is used. Examples of the polypropylene copolymer include a copolymer of polypropylene and α-olefin. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. A propylene-ethylene copolymer can also be used. A polypropylene resin having an MFR in the range of 0.5 to 20 g / 10 min and a melting point in the range of 130 to 170 ° C. is preferably used. Such MFR was measured based on JIS K7210. Among these polypropylene resins, ethylene content is 1 to 5% by weight, melting point is 135 to 155 ° C., MFR is 0.5 to 5.0 g / 10 minutes, or ethylene content is 5 to 10%. %, A melting point of 150 to 165 ° C., and an MFR of 3.0 to 7.0 g / 10 min.
本発明の発泡剤としては、有機系熱分解型発泡剤が好適に用いられる。有機系熱分解型発泡剤としては、加熱により分解して気体を発生する化合物が好ましく使用され、具体的には、アゾジカルボンアミド、オキシベンゼンスルホニルヒドラジド、ジニトロソペンタメチレンテトラミン、トルエンスルホニルヒドラジド、４，４−オキシビス（ベンゼンスルホニルヒドラジド）、アゾビスイソブチロニトリル、アゾジカルボン酸バリウム、ヒドラゾジカルボンアミド等が好ましく使用される。これらは単独で用いてもよいし、併用してもよい。 As the foaming agent of the present invention, an organic pyrolytic foaming agent is preferably used. As the organic pyrolytic foaming agent, a compound that decomposes by heating to generate a gas is preferably used. Specifically, azodicarbonamide, oxybenzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, 4 , 4-oxybis (benzenesulfonylhydrazide), azobisisobutyronitrile, barium azodicarboxylate, hydrazodicarbonamide and the like are preferably used. These may be used alone or in combination.
本発明の発泡剤含有マスターバッチ（Ｂ）は、上述のエチレン−酢酸ビニル共重合体（Ａ）に上述の発泡剤を単独または併用して添加し、エチレン−酢酸ビニル共重合体（Ａ）１００重量部に対して発泡剤を１５〜１００重量部添加することが好ましい。エチレン−酢酸ビニル共重合体（Ａ）１００重量部に対して発泡剤が５重量部未満の場合、発泡剤マスターバッチを多量に添加する必要があり、コストアップとなる。 The foaming agent-containing masterbatch (B) of the present invention is obtained by adding the above-mentioned foaming agent alone or in combination to the above-described ethylene-vinyl acetate copolymer (A), thereby producing an ethylene-vinyl acetate copolymer (A) 100. It is preferable to add 15 to 100 parts by weight of a foaming agent with respect to parts by weight. When the foaming agent is less than 5 parts by weight relative to 100 parts by weight of the ethylene-vinyl acetate copolymer (A), it is necessary to add a large amount of the foaming agent master batch, resulting in an increase in cost.
発泡剤含有マスターバッチ（Ｂ）には、オレフィン系ワックス等の分散剤やキッカー剤、熱安定剤を添加しても良い。 You may add dispersing agents, such as an olefin type wax, a kicker agent, and a heat stabilizer to a foaming agent containing masterbatch (B).
本発明においては、本発明の目的を損なわない範囲内で、フェノール系、リン系、アミン系、イオウ系等の酸化防止剤、多官能性モノマーであるジビニルベンゼン、トリメチロールプロパントリメタクリレート、１，６−ヘキサンジオールジメタクリレート、１，９−ノナンジオールジメタクリレート、１，１０−デカンジオールジメタクリレート、トリアリルイソシアヌレート、エチルビニルベンゼン、エチレンビニルジメタクリレート、１，２−ベンゼンジカルボン酸ジアリルエステル、１，３−ベンゼンジカルボン酸ジアリルエステル、１，４−ベンゼンジカルボン酸ジアリルエステル、１，２，４−ベンゼントリカルボン酸ジアリルエステル等の架橋助剤、脂肪酸系、脂肪酸ビスアミド系、脂肪酸モノアミド系、脂肪酸アミド系、脂肪酸アミド誘導体、ヒドロキシ脂肪酸アミド系、脂肪酸金属石鹸、脂肪族アルコール、シリコン、オレフィン系ワックス、アクリル系高分子、エステル系、脂肪酸エステル系、ベタイン系等の分散剤、顔料、金属害防止剤、粘土鉱物、シリカ、コロイダルシリカ、珪藻土、ゼオライト、マイカ、タルク等の充填剤、帯電防止剤、難燃剤等を添加してもよい。 In the present invention, within the range not impairing the object of the present invention, antioxidants such as phenols, phosphoruss, amines and sulfurs, polyfunctional monomers divinylbenzene, trimethylolpropane trimethacrylate, 1, 6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, triallyl isocyanurate, ethyl vinylbenzene, ethylene vinyl dimethacrylate, 1,2-benzenedicarboxylic acid diallyl ester, 1 Crosslinking aids such as 1,3-benzenedicarboxylic acid diallyl ester, 1,4-benzenedicarboxylic acid diallyl ester, 1,2,4-benzenetricarboxylic acid diallyl ester, fatty acid, fatty acid bisamide, fatty acid monoamide, fatty acid amide , Fat Acid amide derivatives, hydroxy fatty acid amides, fatty acid metal soaps, aliphatic alcohols, silicon, olefinic waxes, acrylic polymers, ester-based, fatty acid ester-based, betaine-based dispersants, pigments, metal damage inhibitors, clays Minerals, silica, colloidal silica, diatomaceous earth, zeolite, mica, talc and other fillers, antistatic agents, flame retardants and the like may be added.
融点の違う樹脂において、融点の低いエチレン−酢酸ビニル共重合体（Ａ）と発泡剤を融点温度から融点温度よりも５０℃低い温度で剪断力をかけながら溶融混練することにより発泡剤含有マスターバッチ（Ｂ）を製造し、エチレン−酢酸ビニル共重合体（Ａ）よりも融点の高いポリオレフィン系樹脂（Ｃ）を前記ポリオレフィン系樹脂（Ｃ）の融点から融点よりも５０℃低い温度で剪断力をかけながら溶融混練し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を製造し、押出機で溶融混練することにより発泡剤が均一に分散し、粗気泡やピンホールの数が少ない発泡体が出来ることを見出した。 In a resin having a different melting point, an ethylene-vinyl acetate copolymer (A) having a low melting point and a foaming agent are melt-kneaded while applying a shearing force from the melting point to a temperature lower by 50 ° C. than the melting point temperature. (B) is produced, and the polyolefin resin (C) having a higher melting point than the ethylene-vinyl acetate copolymer (A) is subjected to a shearing force at a temperature 50 ° C. lower than the melting point of the polyolefin resin (C). The resin composition for polyolefin resin cross-linked foam is produced by melting and kneading while being applied, and the foaming agent is uniformly dispersed by melting and kneading with an extruder, so that a foam with few coarse bubbles and pinholes can be produced. I found.
融点の違う２種類の原料に対し、融点の低いエチレン−酢酸ビニル共重合体（Ａ）１００重量部に対して発泡剤を1５〜１００重量部配合し、前記エチレン−酢酸ビニル共重合体（Ａ）の融点温度から融点温度よりも５０℃未満の温度で剪断力をかけながら溶融混練することにより発泡剤含有マスターバッチ（Ｂ）を製造し、ポリオレフィン系樹脂（Ｃ）１０〜９０重量％と前記発泡剤含有マスターバッチーバッチ（Ｂ）９０〜１０重量％とからなる樹脂成分１００重量部に対して、前記ポリオレフィン系樹脂（Ｃ）の融点から融点よりも５０℃低い温度で剪断力をかけながら溶融混練し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を製造し、単軸または多軸押出機で溶融混練し、シート状に成型後架橋を行い、発泡させることを特徴とする。 For two types of raw materials having different melting points, 15 to 100 parts by weight of a foaming agent is blended with 100 parts by weight of ethylene-vinyl acetate copolymer (A) having a low melting point, and the ethylene-vinyl acetate copolymer (A ) To produce a blowing agent-containing masterbatch (B) by applying a shearing force at a temperature lower than 50 ° C. from the melting point temperature to a melting point temperature of 10 to 90% by weight of the polyolefin resin (C). Melting while applying a shearing force at a temperature 50 ° C. lower than the melting point of the polyolefin resin (C) with respect to 100 parts by weight of the resin component comprising 90 to 10% by weight of the foaming agent-containing master batch (B) Kneaded to produce a resin composition for a polyolefin resin cross-linked foam, melt-kneaded with a single-screw or multi-screw extruder, molded into a sheet, cross-linked, and then foamed The
上記方法で製造した発泡体をフォーム厚みの中央でスライスし、１００ｍ２当たりのスライス面上の粗気泡の個数とピンホールの数をカウントした。粗気泡の定義は、スライス面の平均気泡径の５倍以上の気泡径とする。ピンホールの定義は、発泡体の表裏面上に平均気泡径の５倍以上のヘコミで内部に発泡剤分解残差があるものとし、粗気泡とピンホールの数が１０個／１００ｍ２以下であった。 The foam produced by the above method was sliced at the center of the foam thickness, and the number of coarse bubbles and the number of pinholes on the slice surface per 100 m 2 were counted. The definition of the coarse bubble is a bubble diameter of 5 times or more of the average bubble diameter of the slice surface. The definition of pinholes is that there are residuals of foaming agent inside with a dent larger than 5 times the average bubble diameter on the front and back surfaces of the foam, and the number of coarse bubbles and pinholes is 10/100 m 2 or less. there were.
（１）発泡倍率
ＪＩＳ Ｋ６７６７により、発泡体の密度をそれぞれのサンプルで３回測定し、発泡体の密度の平均値を求め、次式により発泡倍率を求める。
発泡倍率＝１／発泡体密度平均（ｎ＝３）
（２）平均気泡径
スライサーで発泡体を厚み方向に対し中央部でスライスし、スライス面をマイクロウオッチャーで１０倍に拡大し、ＴＤ方向の２５ｍｍ間の気泡個数を測定し、次の計算により平均気泡径を求める。
(1) Foaming magnification According to JIS K6767, the density of a foam is measured 3 times with each sample, the average value of the density of a foam is calculated | required, and a foaming magnification is calculated | required by following Formula.
Foaming ratio = 1 / foam density average (n = 3)
(2) Average bubble diameter Slice the foam in the center with respect to the thickness direction, expand the slice surface 10 times with a microwatcher, measure the number of bubbles between 25 mm in the TD direction, and perform the following calculation: Obtain the average bubble diameter.
平均気泡径＝２５０００／セルの実数（単位：μｍ／個）
サンプルを３個準備しそれぞれのサンプルを各１回計３回測定した際の平均値を平均気泡径とした。
（３）ピンホール数
発泡体の直径１ｍｍ以上の表裏面の穴をピンホールとし、上下面より光を当て目視観測し、発泡体１００m２当たりのピンホールの個数をカウントし、３回測定した際の平均値をピンホール数とした。
（４）粗気泡数
粗気泡数は、発泡体を厚み方向に対してスライスし、スライス面において平均気泡径の５倍以上の大きさのセル径と定義する。粗気泡数は１００m２あたりのスライス面の粗気泡の数で、測定方法は、平均気泡径＊５倍で計算した円を描いた透明フィルムのプレートを準備し、目視で気泡を照合し、大きいセルをカウントする。このようにして測定を行い、３回測定した際の平均値を求めた。
（実施例１）
エチレン−酢酸ビニル共重合体で融点が７８℃、ＭＦＲが２．８ｇ/1０分、その密度が０．９４８ｇ／ｃｍ３の樹脂（東ソー社製 ６４０）１００重量部に発泡剤のアゾジカルボンアミドを１００重量部を押出機（４０φ、L/D＝２０、単軸押出機）に供給し、押出温度が１２０℃で溶融混練し、Tダイでシート状に成型後チッパーで発泡剤濃度５０％のエチレン−酢酸ビニル共重合体発泡剤含有マスターバッチを製造した。
Average bubble diameter = 25000 / real number of cells (unit: μm / piece)
Three samples were prepared, and the average value when each sample was measured three times in total was taken as the average bubble diameter.
(3) a pin pinhole holes of the front and rear surfaces of the above diameter 1mm hole number foam was visually observed against the light from the upper and lower surfaces, and counting the number of pinholes per foam 100 m 2, it was measured 3 times The average value at that time was defined as the number of pinholes.
(4) Number of coarse bubbles The number of coarse bubbles is defined as a cell diameter having a size of 5 times or more of the average cell diameter on the slice surface by slicing the foam in the thickness direction. The number of coarse bubbles is the number of coarse bubbles on the slicing surface per 100 m 2 , and the measurement method is to prepare a transparent film plate on which a circle calculated with an average bubble diameter * 5 times is prepared. Count cells. Measurement was performed in this manner, and an average value was obtained when three measurements were taken.
Example 1
An ethylene-vinyl acetate copolymer having a melting point of 78 ° C., an MFR of 2.8 g / 10 min, and a density of 0.948 g / cm 3 of resin (640 manufactured by Tosoh Corporation) is mixed with a blowing agent azodicarbonamide. 100 parts by weight are supplied to an extruder (40φ, L / D = 20, single screw extruder), melt-kneaded at an extrusion temperature of 120 ° C., molded into a sheet with a T-die, and then a foaming agent concentration of 50% with a chipper. An ethylene-vinyl acetate copolymer foaming agent-containing masterbatch was produced.
低密度ポリエチレンで融点が１１１℃、ＭＦＲが３．０ｇ／１０分、密度が９２４ｋｇ／ｍ３ の樹脂（東ソー社製 １８８）６５重量部とエチレン−酢酸ビニル共重合体（東ソー社製 ６４０）３５重量部とエチレン−酢酸ビニル共重合体と低密度ポリエチレンの合計を１００重量部とし、それに対して、にエチレン−酢酸ビニル共重合体発泡剤マスターバッチ（発泡剤濃度５０％）を１０重量部と酸化防止剤（ＢＨＴ）を０．５部を押出機（１５０φ、L/D ＝６．６、２軸押出機）に供給し、押出温度１５０℃で押出し、Tダイでシート状に成型後チッパーでペレット化し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を製造し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を押出機（１５０φ、L/D ＝６．６、２軸押出機）に供給し、押出温度１５０℃で押出し、Tダイで厚さ1mmの長尺シートを作成した。 Low-density polyethylene with a melting point of 111 ° C., an MFR of 3.0 g / 10 min, and a density of 924 kg / m 3 of resin (188 manufactured by Tosoh Corporation) and 65 parts by weight of an ethylene-vinyl acetate copolymer (640 manufactured by Tosoh Corporation) 35 100 parts by weight of a total of parts by weight, ethylene-vinyl acetate copolymer and low-density polyethylene, and 10 parts by weight of an ethylene-vinyl acetate copolymer blowing agent master batch (foaming agent concentration 50%) 0.5 parts of antioxidant (BHT) is supplied to an extruder (150φ, L / D = 6.6, twin screw extruder), extruded at an extrusion temperature of 150 ° C., formed into a sheet with a T-die, and then chippered To produce a resin composition for polyolefin resin cross-linked foam, and supply the resin composition for polyolefin resin cross-linked foam to an extruder (150φ, L / D = 6.6, twin screw extruder). , Extrusion temperature The sheet was extruded at a temperature of 150 ° C., and a long sheet having a thickness of 1 mm was prepared with a T-die.
このシートに７００KV、５０ＫＧｙの電子線を照射し架橋を施した。熱風発泡装置で２７０℃で発泡剤を分解し、厚さ２．００ｍｍフォーム密度９０ｋｇ／ｍ３の長尺架橋発泡体を製造した。 This sheet was irradiated with 700 KV and 50 KGy electron beams for crosslinking. The foaming agent was decomposed at 270 ° C. with a hot air foaming apparatus to produce a long cross-linked foam having a thickness of 2.00 mm and a foam density of 90 kg / m 3 .
このようにして得られた架橋発泡体１００m２の表裏面のピンホールの個数をカウントし、透過光では、粗気泡がわかりにくいため、発泡体を１．００ｍｍにスライスし、１００m２あたりのスライス面の粗大気泡の数をカウントした。その結果を表１に示す。
（比較例１）
比較例１として、低密度ポリエチレンで融点が１１１℃、ＭＦＲが３．０ｇ／１０分、密度が９２４ｋｇ／ｍ３ の樹脂（東ソー社製 １８８）に１００重量部に発泡剤のアゾジカルボンアミドを１００重量部を押出機（４０φ、L/D＝２０、単軸押出機）に供給し、押出温度が１５０℃で溶融混練し、Tダイでシート状に成型後チッパーで発泡剤濃度５０％の低密度ポリエチレン樹脂発泡剤マスターバッチを製造した。エチレン−酢酸ビニル共重合体で融点が７８℃、ＭＦＲが２．８ｇ/1０分、その密度が0.948 g/cm3 の樹脂（東ソー社製 ６４０）７０重量部と低密度ポリエチレンで融点が１１１℃、ＭＦＲが３．０ｇ／１０分、密度が９２４ｋｇ／ｍ３ の樹脂（東ソー社製 １８８）３０重量部とエチレン−酢酸ビニル共重合体と低密度ポリエチレンの合計を１００重量部とし、それに対して、低密度ポリエチレン樹脂発泡剤マスターバッチ（発泡剤濃度５０％）を１０重量部と酸化防止剤（ＢＨＴ）を０．５部を押出機（１５０φ、L/D ＝６．６、２軸押出機）に供給し、押出温度１５０℃で押出し、Tダイでシート状に成型後チッパーでペレット化し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を製造し、ポリオレフィン系樹脂架橋発泡体用樹脂組成物を押出機（１５０φ，L/D ＝６．６，２軸押出機）に供給し、押出温度１５０℃で押出し、Tダイで厚さ1mmの長尺シートを作成した。
The number of pinholes on the front and back surfaces of the cross-linked foam 100 m 2 obtained in this way was counted, and since the rough bubbles were difficult to see in the transmitted light, the foam was sliced to 1.00 mm and sliced per 100 m 2 The number of coarse bubbles on the surface was counted. The results are shown in Table 1.
(Comparative Example 1)
As Comparative Example 1, 100 parts by weight of azodicarbonamide as a blowing agent was added to 100 parts by weight of a resin (188 manufactured by Tosoh Corporation) having a low-density polyethylene, a melting point of 111 ° C., an MFR of 3.0 g / 10 min, and a density of 924 kg / m 3 Part by weight is supplied to an extruder (40φ, L / D = 20, single screw extruder), melt kneaded at an extrusion temperature of 150 ° C., formed into a sheet with a T-die, and low in a blowing agent concentration of 50% with a chipper. A density polyethylene resin blowing agent masterbatch was produced. An ethylene-vinyl acetate copolymer has a melting point of 78 ° C., an MFR of 2.8 g / 10 minutes, and a density of 0.948 g / cm 3 of resin (640 manufactured by Tosoh Corporation) and low-density polyethylene having a melting point of 111 ° C. , 30 parts by weight of a resin having a MFR of 3.0 g / 10 min and a density of 924 kg / m 3 (188 manufactured by Tosoh Corporation), a total of 100 parts by weight of ethylene-vinyl acetate copolymer and low-density polyethylene, 10 parts by weight of a low density polyethylene resin foaming agent masterbatch (foaming agent concentration of 50%) and 0.5 part of an antioxidant (BHT) are extruders (150φ, L / D = 6.6, twin screw extruder ), Extruded at an extrusion temperature of 150 ° C., molded into a sheet with a T-die and pelletized with a chipper to produce a resin composition for a polyolefin-based resin crosslinked foam, and a resin composition for a polyolefin-based resin crosslinked foam Push Machine (150φ, L / D = 6.6,2-screw extruder) is supplied to and generated extrusion, a long sheet having a thickness of 1mm at a T-die at an extrusion temperature 0.99 ° C..
このシートに７００KV、５０ＫＧｙの電子線を照射し架橋を施した。熱風発泡装置で２７０℃で発泡剤を分解し、厚さ２．００ｍｍフォーム密度９０ｋｇ／ｍ３の長尺架橋発泡体を製造した。 This sheet was irradiated with 700 KV and 50 KGy electron beams for crosslinking. The foaming agent was decomposed at 270 ° C. with a hot air foaming apparatus to produce a long cross-linked foam having a thickness of 2.00 mm and a foam density of 90 kg / m 3 .
このようにして得られた架橋発泡体１００m２の表裏面のピンホールの個数をカウントし、透過光では、粗気泡がわかりにくいため、発泡体を１．００ｍｍにスライスし、１００m２あたりのスライス面の粗大気泡の数をカウントした。その結果、表２の通り平均気泡径は、０．４ｍｍで、ピンホールの個数が２〜４で粗気泡の個数は、５〜１０個／１００ｍ２で規格外のものが発生する。
（比較例２）
比較例２として、エチレン−酢酸ビニル共重合体の酢酸ビニル含有率が２６重量％でＭＦＲが２．８ｇ/1０分で、その密度が0.948 g/cm3の樹脂（東ソー社製 ６４０） を重量と低密度ポリエチレンでＭＦＲが３．０ｇ／１０分、密度が９２４ｋｇ／ｍ３ 、融点が１１１℃の樹脂（東ソー社製 １８８）の比率が７０：３５で合計１００重量部に対して、粉末発泡剤を５部添加し、さらに酸化防止剤（ＢＨＴ）を０．５部添加し、押出機に直接投入し、押出機（１５０φ、L/D ＝６．６、２軸押出機）で押出温度１５０℃で押出厚さ１．０mmの長尺シートを作成した。
The number of pinholes on the front and back surfaces of the cross-linked foam 100 m 2 obtained in this way was counted, and since the rough bubbles were difficult to see in the transmitted light, the foam was sliced to 1.00 mm and sliced per 100 m 2 The number of coarse bubbles on the surface was counted. As a result, as the average cell diameter in Table 2, in 0.4 mm, the number of coarse bubbles number of pinholes 2-4 are those out of the standard occurs in 5-10 / 100 m 2.
(Comparative Example 2)
As Comparative Example 2, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 26% by weight, an MFR of 2.8 g / 10 min, and a density of 0.948 g / cm 3 (640 manufactured by Tosoh Corp.) And low-density polyethylene with an MFR of 3.0 g / 10 min, a density of 924 kg / m 3 , and a melting point of 111 ° C. resin (188, made by Tosoh Corporation) in a ratio of 70:35 to a total of 100 parts by weight. 5 parts of the additive and 0.5 part of antioxidant (BHT) are added, and the mixture is directly charged into the extruder, and the extruder (150φ, L / D = 6.6, twin screw extruder) is used for the extrusion temperature. A long sheet having an extrusion thickness of 1.0 mm was prepared at 150 ° C.
このシートに７００KV、５０ＫＧｙの電子線を照射し架橋を施した。熱風発泡装置で発泡剤の分解温度以上に加熱し、厚さ２．００ｍｍフォーム密度９０ｋｇ／ｍ３の長尺架橋発泡体を製造した。 This sheet was irradiated with 700 KV and 50 KGy electron beams for crosslinking. It heated above the decomposition temperature of the foaming agent with a hot air foaming device to produce a long cross-linked foam having a thickness of 2.00 mm and a foam density of 90 kg / m 3 .
このようにして得られた架橋発泡体を１．００ｍｍにスライスし、１００cm2あたり１ｍｍ以上の粗大気泡の数をカウントした。その結果、表２の通り平均気泡径は、０．４ｍｍで、ピンホールの個数が７〜１２粗気泡の個数は、４８〜７６個／１００ｍ２で外観上問題がある。 The thus obtained crosslinked foam was sliced into 1.00 mm, and the number of coarse bubbles of 1 mm or more per 100 cm 2 was counted. As a result, as the average cell diameter in Table 2, in 0.4 mm, the number of the number of pinholes 7-12 coarse bubbles may appearance problems 48-76 pieces / 100 m 2.
本発明の酢酸ビニル架橋発泡体は、食品のパッキンや包装材、粘着テープ等に好適に用いることができる。 The vinyl acetate crosslinked foam of the present invention can be suitably used for food packing, packaging materials, adhesive tapes and the like.
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