JP7219001B2 - cushioning material - Google Patents
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- JP7219001B2 JP7219001B2 JP2017120054A JP2017120054A JP7219001B2 JP 7219001 B2 JP7219001 B2 JP 7219001B2 JP 2017120054 A JP2017120054 A JP 2017120054A JP 2017120054 A JP2017120054 A JP 2017120054A JP 7219001 B2 JP7219001 B2 JP 7219001B2
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Description
本発明は、ポリオレフィン系樹脂押出発泡体からなる、各種物品搬送に使用される緩衝材に関する。 TECHNICAL FIELD The present invention relates to a cushioning material made of an extruded polyolefin resin foam and used for transporting various articles.
従来、電気部品や電子部品のような外部からの衝撃に対し弱い製品の運搬や自動車部品のような比較的重量のある物品を運搬する際には、運搬時の衝撃を緩和させ当該製品を破損から守るために、さまざまな緩衝材が用いられている。中でも発泡プラスチックは衝撃を吸収し製品にかかる衝撃を緩和する特性に優れており、最も多く用いられている緩衝材のひとつである。発泡プラスチックの緩衝性のレベルは、該発泡体を構成するプラスチックの種類により異なる。最も多く用いられているポリスチレンからなる発泡体は、ポリスチレンが柔軟性に欠ける為に、繰り返して衝撃が加わると発泡体の破壊がおこり緩衝性が急速に低下するという欠点がある。一方、発泡ポリエチレン系樹脂からなる緩衝材は、ポリエチレン系樹脂が柔軟性に富む為に上記のような繰り返しの衝撃に対する緩衝性の低下はなく、繰り返し使用される用途においては好適に使用される。 Conventionally, when transporting products that are vulnerable to external shocks, such as electrical and electronic parts, or relatively heavy items, such as automobile parts, it is necessary to reduce the impact during transportation and damage the product. Various cushioning materials are used to protect against Among them, foamed plastic is one of the most widely used cushioning materials because it has excellent properties of absorbing impact and mitigating the impact applied to the product. The level of cushioning properties of foamed plastic varies depending on the type of plastic that makes up the foam. The foam made of polystyrene, which is the most widely used material, has the disadvantage that repeated impacts cause the foam to break and the cushioning performance to rapidly decrease due to the lack of flexibility of polystyrene. On the other hand, a cushioning material made of foamed polyethylene resin does not deteriorate in cushioning properties against repeated impacts as described above because polyethylene resin is highly flexible, and is preferably used in applications where it is used repeatedly.
例えば、特許文献１には、ＩＣ等の静電気破壊防止用の簡易パッケージ材料として好適なものとして、ポリエチレン系樹脂とエチレン－酢酸ビニル共重合体とを含有する架橋性組成物を加熱、発泡して得られる架橋ポリエチレン系発泡体が開示されている。一般に、エチレン－酢酸ビニル共重合体は発泡性が劣るものの、架橋せしめると、高い独立気泡率を有する発泡体が得られ、厚物の成形体も成形しうる。しかしながら、当該発泡体は高度に架橋されているためリサイクルが難しく、当該発泡体を用いた緩衝材は使用後に埋め立てや燃焼により廃棄せざるをえず、環境に負荷をかける点で問題がある。 For example, in Patent Document 1, a crosslinkable composition containing a polyethylene resin and an ethylene-vinyl acetate copolymer is heated and foamed as a material suitable as a simple packaging material for preventing electrostatic breakdown of ICs and the like. The resulting crosslinked polyethylene-based foam is disclosed. In general, ethylene-vinyl acetate copolymers are inferior in foamability, but when crosslinked, foams having a high closed cell ratio can be obtained, and thick molded articles can be molded. However, since the foam is highly crosslinked, it is difficult to recycle, and the cushioning material using the foam must be disposed of by landfilling or burning after use, which poses a problem in that it places a burden on the environment.
特許文献２には、特定の酢酸ビニル成分含有量を有する、エチレン－酢酸ビニル共重合体、または、エチレン－酢酸ビニル共重合体とポリエチレン系樹脂の混合物を発泡させて得られる、滑り防止性を有する無架橋ポリエチレン系樹脂発泡シートが開示されている。このような無架橋押出発泡シートは、リサイクルが容易で環境に優しい発泡体として緩衝材分野にも利用実績が多い。しかしながら、酢酸ビニル含有率が高い共重合体は発泡性が劣る傾向にあり、高独立気泡率の発泡体を安定して得ることが困難である。特に、セル微細化や高独立気泡率維持が難しい厚物の発泡体で所望通りの物性を達成することは難しく、滑り防止性の良好な厚物の緩衝材を得ることは困難である。 Patent Document 2 discloses anti-slip properties obtained by foaming an ethylene-vinyl acetate copolymer or a mixture of an ethylene-vinyl acetate copolymer and a polyethylene-based resin having a specific vinyl acetate component content. A non-crosslinked polyethylene resin foam sheet having Such non-crosslinking extruded foam sheets are widely used in the field of cushioning materials as easily recyclable and environmentally friendly foams. However, copolymers with a high vinyl acetate content tend to have poor foamability, and it is difficult to stably obtain a foam with a high closed cell content. In particular, it is difficult to achieve desired physical properties in a thick foam that is difficult to refine cells and maintain a high closed cell content, and it is difficult to obtain a thick cushioning material with good anti-slip properties.
また、リサイクル可能な無架橋発泡体からなる緩衝材としては、発泡性が良好な低密度ポリエチレンを用いた無架橋発泡体が一般的に使用されている。一般的に分岐構造を有する低密度ポリエチレンは溶融聴力が高く発泡性に優れるという点から、高い独立気泡率を達成するものの、セル径が粗い物が主流となっており、製品の滑り防止性に優れた、すなわちグリップ力の高い特性が要求される緩衝材には適用され難い。 Moreover, as a cushioning material made of a recyclable non-crosslinked foam, a non-crosslinked foam using low-density polyethylene with good foamability is generally used. In general, low-density polyethylene with a branched structure has high melt hearing ability and excellent foaming properties, so although it achieves a high closed cell ratio, it is mainly used with coarse cell diameters, and it is effective in preventing product slippage. It is difficult to apply to cushioning materials that require excellent properties, that is, high gripping power.
本発明の目的は、低コストかつリサイクル可能で製品のグリップ性に優れ、自動車部品などの大型部品や重量品の運搬に好適に用いられる緩衝材を得ることにある。 SUMMARY OF THE INVENTION An object of the present invention is to obtain a cushioning material which is low-cost, recyclable, excellent in product gripping properties, and suitable for transporting large parts such as automobile parts and heavy goods.
本発明者は、上記課題に鑑みて鋭意研究した結果、発泡倍率、平均気泡径および独立気泡率が特定範囲に制御された厚物の無架橋ポリエチレン系樹脂発泡体によれば、製品を載せた際の密着性に優れ、かつ、重量のある製品の輸送における瞬間的な過荷重にも耐えうる強度を両立した、緩衝材が得られることを見出し、本発明の完成に至った。 As a result of intensive research in view of the above problems, the present inventors have found that a thick non-crosslinked polyethylene resin foam in which the expansion ratio, average cell diameter and closed cell rate are controlled within a specific range can be used when a product is placed. The present inventors have found that a cushioning material can be obtained that has both excellent adhesiveness during transportation and strength that can withstand momentary overloads during the transportation of heavy products, and has completed the present invention.
すなわち、本発明は、下記ａ）からｄ）を満たす無架橋ポリオレフィン系樹脂押出発泡体を使用した緩衝材に関する。 That is, the present invention relates to a cushioning material using a non-crosslinked polyolefin resin extruded foam that satisfies the following a) to d).
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上
また、本発明は、下記ｅ）からｈ）を満たす無架橋ポリオレフィン系樹脂押出発泡体を使用した緩衝材に関する。
a) The expansion ratio is 5 times or more and 30 times or less b) The average cell diameter is 100 μm or more and 600 μm or less c) The closed cell ratio is 70% or more d) The thickness is 20 mm or more In addition, the present invention satisfies the following e) to h) The present invention relates to a cushioning material using a non-crosslinked polyolefin resin extruded foam.
ｅ）発泡倍率が５倍以上３０倍以下
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦３５０ －式（１）
ｇ）独立気泡率が７０％以上
ｈ）厚みが２０ｍｍ以上
本発明において、前記無架橋ポリオレフィン系樹脂押出発泡体の動摩擦係数が０．３１０以上であることが好ましい。
e) Foaming ratio of 5 times or more and 30 times or less
f) Average cell diameter that satisfies the relationship of the following formula (1) - (33.3 x foaming ratio) ≤ 350 - formula (1)
g) Closed cell ratio of 70% or more h) Thickness of 20 mm or more In the present invention, the non-crosslinked polyolefin resin extruded foam preferably has a dynamic friction coefficient of 0.310 or more.
本発明において、前記無架橋ポリオレフィン系樹脂押出発泡体が下記式（２）の関係を満たすことが好ましい。 In the present invention, the non-crosslinked polyolefin resin extruded foam preferably satisfies the relationship of the following formula (2).
圧縮応力比≧０．４×Ｌｎ（発泡倍率）－０．４ －式（２）
圧縮応力比＝Ｓ２５５０／Ｓ０４
Ｓ０４：歪０％と４％での圧縮応力の差（ＭＰａ）
Ｓ２５５０：歪２５％と５０％での圧縮応力の差（ＭＰａ）
本発明において、前記ポリオレフィン系樹脂がポリエチレン系樹脂を含むことが好ましい。
Compressive stress ratio ≥ 0.4 × Ln (expansion ratio) -0.4 - formula (2)
Compressive stress ratio = S2550/S04
S04: difference in compressive stress at strain 0% and 4% (MPa)
S2550: difference in compressive stress at 25% and 50% strain (MPa)
In the present invention, the polyolefin-based resin preferably contains a polyethylene-based resin.
本発明においては、前記ポリオレフィン系樹脂１００重量％において低密度ポリエチレンが６０重量％以上含まれることが好ましい。 In the present invention, it is preferable that 60% by weight or more of low-density polyethylene is contained in 100% by weight of the polyolefin resin.
本発明において、前記低密度ポリエチレンの密度が９００～９３０ｋｇ／ｍ３であることが好ましい。 In the present invention, the density of the low density polyethylene is preferably 900-930 kg/m 3 .
本発明の緩衝材は、重量品の輸送用に好適である。 The cushioning material of the present invention is suitable for transporting heavy goods.
本発明は、ポリオレフィン系樹脂、および、脂肪族炭化水素類を含む発泡剤を溶融混練する工程、および、前記溶融混練で得られる発泡剤を含んだ溶融状態の樹脂組成物を冷却した後に減圧下に押出発泡し発泡体を成形する工程を含む、次のａ）～ｄ）の要件を満たす無架橋ポリオレフィン系樹脂押出発泡体の製造方法に関する。
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上
本発明は、ポリオレフィン系樹脂、および、脂肪族炭化水素類を含む発泡剤を溶融混練する工程、および、前記溶融混練工程で得られる発泡剤を含んだ溶融状態の樹脂組成物を冷却した後に減圧下に押出発泡しの発泡体を成形する工程を含む、次のｅ）～ｈ）の要件を満たす無架橋ポリオレフィン系樹脂押出発泡体の製造方法に関する。
The present invention comprises a step of melt-kneading a polyolefin resin and a foaming agent containing an aliphatic hydrocarbon, and cooling the molten resin composition containing the foaming agent obtained by the melt-kneading, followed by It relates to a method for producing a non-crosslinked polyolefin resin extruded foam that satisfies the following requirements a) to d), including the step of extruding and molding the foam.
a) Expansion ratio of 5 to 30 times b) Average cell diameter of 100 μm to 600 μm c) Closed cell ratio of 70% or more d) Thickness of 20 mm or more The present invention provides a polyolefin resin and an aliphatic hydrocarbon. and a step of cooling the molten resin composition containing the foaming agent obtained in the melt-kneading step and extruding under reduced pressure to form a foamed product. , to a method for producing a non-crosslinked polyolefin resin extruded foam that satisfies the following requirements e) to h).
ｅ）発泡倍率が５倍以上３０倍以下
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦３５０ －式（１）
ｇ）独立気泡率が７０％以上
ｈ）厚みが２０ｍｍ以上
本発明において、前記樹脂組成物が気泡核形成剤として化学発泡剤を含むことが好ましい。
e) Foaming ratio of 5 times or more and 30 times or less
f) satisfying the relationship of the following formula (1)
Average bubble diameter - (33.3 x foaming ratio) ≤ 350 - formula (1)
g) closed cell ratio of 70% or more h) thickness of 20 mm or more In the present invention, the resin composition preferably contains a chemical foaming agent as a cell nucleating agent.
本発明において、前記化学発泡剤が炭酸水素ナトリウムとクエン酸塩との混合物であることが好ましい。 In the present invention, the chemical blowing agent is preferably a mixture of sodium bicarbonate and citrate.
本発明において、前記樹脂組成物が収縮防止剤を含むことが好ましい。 In the present invention, the resin composition preferably contains an anti-shrinkage agent.
本発明によれば、運搬される製品のグリップ力に優れ、自動車部品や各種工業製品、中でもバランスの崩れ易い大物製品、重量物に好適な緩衝材が得られる。 According to the present invention, it is possible to obtain a cushioning material which is excellent in gripping force for transported products and which is suitable for automobile parts and various industrial products, particularly large and heavy products that tend to be out of balance.
本発明の第一の緩衝材は、発泡倍率が５倍以上３０倍以下であり、平均気泡径が１００μｍ以上６００μｍ以下であり、独立気泡率が７０％以上であり、および、厚みが２０ｍｍ以上である無架橋ポリオレフィン系樹脂押出発泡体からなることを特徴とする。発泡倍率、独立気泡率、および、厚みは従来から緩衝材に用いられる板状発泡体に要求される特性ではあるが、これらが上記範囲を満たし、かつ平均気泡径が上記範囲を満たすことが重要であり、上記要件を満たす無架橋ポリオレフィン系樹脂押出発泡体を用いることにより、製品のグリップ力に優れ、かつ、重量物の搬送に耐えうる強度を両立した緩衝材を得られる。さらに、本発明の緩衝材は無架橋ポリオレフィン系樹脂押出発泡体からなるため、リサイクル性をも有する。 The first cushioning material of the present invention has an expansion ratio of 5 times or more and 30 times or less, an average cell diameter of 100 μm or more and 600 μm or less, a closed cell ratio of 70% or more, and a thickness of 20 mm or more. It is characterized by comprising a non-crosslinked polyolefin resin extruded foam. Expansion ratio, closed cell ratio, and thickness are properties required for plate-shaped foams conventionally used as cushioning materials. By using a non-crosslinked polyolefin resin extruded foam that satisfies the above requirements, it is possible to obtain a cushioning material that has both excellent product grip and strength enough to withstand the transportation of heavy objects. Furthermore, since the cushioning material of the present invention is made of non-crosslinked polyolefin resin extruded foam, it also has recyclability.
無架橋ポリオレフィン系樹脂押出発泡体の平均気泡径は、所望の独立気泡率および発泡倍率に調整し易い点から、１２０μｍ以上であること好ましく、１４０μｍ以上がより好ましく、１５０μｍ以上が更に好ましい。また、製品のグリップ性能に影響する摩擦係数が大きくなる点から５００μｍ以下であることが好ましく、４００μｍ以下がより好ましく、３００μｍ以下が更に好ましい。ここで、平均気泡径とは、後述する実施例に記載の測定方法により測定したものである。 The average cell diameter of the non-crosslinked polyolefin resin extruded foam is preferably 120 μm or more, more preferably 140 μm or more, and even more preferably 150 μm or more, from the viewpoint of facilitating adjustment to a desired closed cell ratio and expansion ratio. In addition, it is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less, because the coefficient of friction that affects the grip performance of the product increases. Here, the average bubble diameter is measured by the measuring method described in Examples described later.
無架橋ポリオレフィン系樹脂押出発泡体の発泡倍率は、５～３０倍の範囲にあることで、緩衝材としての加工性が良好で、軽量部品から自動車のエンジン等の重量部品の緩衝材としての使用が可能となる。発泡倍率は製品の重量によって適宜選択されるが、グリップ性と緩衝性のバランスが得られやすいとの観点から、下限値は、好ましくは６倍であり、より好ましくは７倍である。一方、上限値は、好ましくは２５倍であり、より好ましくは２０倍である。 The expansion ratio of the non-crosslinked polyolefin resin extruded foam is in the range of 5 to 30 times, so it has good workability as a cushioning material, and can be used as a cushioning material for lightweight parts to heavy parts such as automobile engines. becomes possible. The expansion ratio is appropriately selected depending on the weight of the product, but the lower limit is preferably 6 times, more preferably 7 times, from the viewpoint of easily obtaining a balance between grip and cushioning properties. On the other hand, the upper limit is preferably 25 times, more preferably 20 times.
無架橋ポリオレフィン系樹脂押出発泡体の独立気泡率は７０％以上であることで、緩衝材としての緩衝性能や繰り返し使用性能、さらには打ち抜き加工時の寸法回復性が良好となる。好ましくは７５％以上であり、より好ましくは８０％以上であることが好ましい。 When the non-crosslinked polyolefin resin extruded foam has a closed cell ratio of 70% or more, the cushioning performance as a cushioning material, the repeated use performance, and the dimensional recovery property during punching are improved. It is preferably 75% or more, more preferably 80% or more.
無架橋ポリオレフィン系樹脂押出発泡体の厚みは、加工によりさまざまな緩衝材形状への加工が可能となるという観点、およびシートの積層体ではなく一枚物として使用した際に緩衝材として均質なものが得られ易いとの観点から好ましくは３０ｍｍ以上、４０ｍｍ以上であることがより好ましい。厚みの上限については特に制約は無いが、押出発泡による厚み確保の難しさから、通常は１５０ｍｍ以下、さらには１００ｍｍ以下、特に７０ｍｍ以下であることが好ましい。 The thickness of the non-crosslinked polyolefin resin extruded foam should be uniform from the standpoint that it can be processed into a variety of cushioning material shapes, and when used as a single piece instead of a laminated sheet, it will be uniform as a cushioning material. is preferably 30 mm or more, and more preferably 40 mm or more, from the viewpoint that is easy to obtain. The upper limit of the thickness is not particularly limited, but it is usually 150 mm or less, more preferably 100 mm or less, and particularly preferably 70 mm or less, due to the difficulty of ensuring the thickness by extrusion foaming.
本発明の、第二の緩衝材は、発泡倍率が５倍以上３０倍以下、独立気泡率が７０％以上であり、下記式（１）を満たし、かつ厚みが２０ｍｍ以上である無架橋ポリオレフィン系樹脂押出発泡体を用いることを特徴とする。 The second cushioning material of the present invention has an expansion ratio of 5 times or more and 30 times or less, a closed cell ratio of 70% or more, satisfies the following formula (1), and has a thickness of 20 mm or more. It is characterized by using an extruded resin foam.
平均気泡径－（３３．３×発泡倍率）≦３５０ －式（１）
本発明の検討過程において、発泡体の摩擦係数は発泡倍率と平均気泡径の影響を受けることが分かっている。すなわち、高い発泡倍率では摩擦係数が高くなるため平均気泡径はある程度大きなものでも許容されるが、低い発泡倍率では、より小さな平均気泡径が必要とされるというものである。具体的には式（１）を満たすことで、摩擦係数が高い発泡体が得られる傾向にあり、このような発泡体を使用することで梱包される製品のグリップ性に優れた緩衝材が得らる。ここでいう摩擦係数とは動摩擦係数のことを言う。
式（１）の右辺の値は好ましくは２００、より好ましくは１００、特に－５０であることが好ましい。
Average bubble diameter - (33.3 x foaming ratio) ≤ 350 - formula (1)
In the process of examining the present invention, it has been found that the coefficient of friction of the foam is affected by the expansion ratio and the average cell diameter. That is, at a high expansion ratio, the coefficient of friction becomes high, so a somewhat large average cell diameter is acceptable, but at a low expansion ratio, a smaller average cell diameter is required. Specifically, by satisfying formula (1), a foam with a high coefficient of friction tends to be obtained. Ral. The coefficient of friction here means the coefficient of dynamic friction.
The value of the right-hand side of formula (1) is preferably 200, more preferably 100, especially -50.
第二の緩衝材における、無架橋ポリオレフィン系樹脂押出発泡体の発泡倍率および厚みは、上述の第一の緩衝材における無架橋ポリオレフィン系樹脂押出発泡体の発泡倍率および厚みが同様に好適である。また、平均気泡径に関しても、第一の緩衝材における無架橋ポリオレフィン系樹脂押出発泡体の平均気泡径が同様に好適である。 The expansion ratio and thickness of the non-crosslinked polyolefin resin extruded foam in the second cushioning material are similarly suitable for the expansion ratio and thickness of the non-crosslinked polyolefin resin extruded foam in the first cushioning material. As for the average cell diameter, the average cell diameter of the non-crosslinked polyolefin resin extruded foam in the first cushioning material is also suitable.
本発明の緩衝材に使用される無架橋ポリオレフィン系樹脂押出発泡体は、製品のグリップ性の観点から、動摩擦係数が、０．３１０以上であることが好ましく、０．３４０以上であることがより好ましく、０．３６０以上であることがさらに好ましい。 The non-crosslinked polyolefin resin extruded foam used in the cushioning material of the present invention preferably has a dynamic friction coefficient of 0.310 or more, more preferably 0.340 or more, from the viewpoint of product grip. It is preferably 0.360 or more, and more preferably 0.360 or more.
さらに、無架橋ポリオレフィン系樹脂押出発泡体は下記式（２）を満たすことが好ましい。 Furthermore, the non-crosslinked polyolefin resin extruded foam preferably satisfies the following formula (2).
圧縮応力比≧０．４×Ｌｎ（発泡倍率）－０．４ －式（２）
圧縮応力比＝Ｓ２５５０／Ｓ０４
・Ｓ０４：歪０％と４％とでの圧縮応力の差（ＭＰａ）
・Ｓ２５５０：歪２５％と５０％とでの圧縮応力の差（ＭＰａ）
上記Ｓ０４は発泡体の圧縮初期の応力であり、緩衝材として使用した場合には製品を載せた際の、ソフト間や密着性に影響する因子である。この値が大きいと製品と緩衝材の密着性が十分に得られず局所荷重になり易く、輸送時の状況によっては意匠性の高い製品表面を傷つけたりすることがある。一方、Ｓ２５５０は大きな圧縮歪が生じた際の歪に対する圧縮応力の向上率を表している。Ｓ２５５０が大きな値を示す発泡体は大きな圧縮歪が生じた際に応力が上昇し易い特性を有しており、製品輸送時に発生する、瞬間的な過荷重に耐え製品の底付き（緩衝材が押し潰され、外部の衝撃をダイレクトに受けてしまうこと）を防止する目安となる。圧縮応力比が高い発泡体からはソフト感と底付き性を両立する緩衝材を得られる傾向にあるが、発泡倍率によってその値は異なる。具体的には式（２）を満たすことで、発泡倍率に応じたソフト感と底付き性とが両立された緩衝材が得られ易く、式（２）の右辺は好ましくは「０．４×Ｌｎ（発泡倍率）－０．３」、さらには「０．４×Ｌｎ（発泡倍率）－０．２」であることが好ましい。また、圧縮応力比は式（２）を満たせば良いが、ソフト感と底付き性の両立が容易との観点から、０．５５以上であることが好ましく、より好ましくは０．６０以上であり、特には０．６５以上であることが好ましい。
Compressive stress ratio ≥ 0.4 × Ln (expansion ratio) -0.4 - formula (2)
Compressive stress ratio = S2550/S04
・ S04: difference in compressive stress between 0% and 4% strain (MPa)
・ S2550: difference in compressive stress between 25% and 50% strain (MPa)
The above S04 is the stress at the initial stage of compression of the foam, and is a factor that affects softness and adhesion when a product is placed on the foam when used as a cushioning material. If this value is large, sufficient adhesion between the product and the cushioning material cannot be obtained, and localized loads are likely to occur, and depending on the conditions during transportation, the surface of the highly designed product may be damaged. On the other hand, S2550 represents the rate of improvement of compressive stress with respect to strain when a large compressive strain occurs. A foam with a large value of S2550 has the property that stress tends to increase when a large compressive strain occurs, and it can withstand momentary overloads that occur during product transportation. It is a measure to prevent crushing and receiving external impact directly). A foam with a high compressive stress ratio tends to provide a cushioning material that has both a soft feel and a good bottoming property, but the values differ depending on the expansion ratio. Specifically, by satisfying formula (2), it is easy to obtain a cushioning material that has both a soft feeling and bottoming property according to the expansion ratio, and the right side of formula (2) is preferably "0.4 × Ln (expansion ratio) −0.3”, more preferably “0.4×Ln (expansion ratio)−0.2”. In addition, the compressive stress ratio may satisfy formula (2), but from the viewpoint of facilitating both softness and bottoming, it is preferably 0.55 or more, more preferably 0.60 or more. , particularly preferably 0.65 or more.
本発明の緩衝材に使用する無架橋ポリオレフィン系樹脂押出発泡体は、ポリオレフィン系樹脂を含む原料樹脂成分と、発泡剤と、必要により後述の各種添加剤とを押出機を用いて溶融混練し、発泡剤を含有する発泡性樹脂溶融物を押出機に付帯したダイスから低圧域に押出し発泡させると同時に、発泡体の進行速度を調整可能な引取機を使用し所望のサイズ（厚み、幅）に成形することにより製造することができる。また、ダイスに付帯した成形金型を使用することも可能である。 The non-crosslinked polyolefin resin extruded foam used for the cushioning material of the present invention is obtained by melt-kneading a raw material resin component containing a polyolefin resin, a foaming agent, and, if necessary, various additives described later using an extruder. A foamable resin melt containing a foaming agent is extruded from a die attached to the extruder to a low pressure region and foamed. It can be manufactured by molding. It is also possible to use a molding die attached to a die.
ポリオレフィン系樹脂としては、発泡性と発泡した際の緩衝性能に優れている樹脂であれば特に制約なく使用することが可能である。ポリオレフィン系樹脂としては、オレフィン成分単位が５０モル％以上の樹脂であればよく、ポリエチレン系樹脂、ポリプロピレン系樹脂等が挙げられる。 As the polyolefin-based resin, any resin can be used without any particular restrictions as long as it is foamable and has excellent cushioning performance when foamed. The polyolefin-based resin may be any resin having an olefin component unit of 50 mol % or more, and examples thereof include polyethylene-based resins and polypropylene-based resins.
ポリエチレン系樹脂としては、例えば、エチレン成分単位が５０モル％以上の樹脂が挙げられ、高密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－プロピレン共重合体、エチレン－プロピレン－ブテン－１共重合体、エチレン－ブテン－１共重合体、エチレン－ヘキセン－１共重合体、エチレン－４－メチルペンテン－１共重合体、エチレン－オクテン－１共重合体等が例示される。 Examples of polyethylene-based resins include resins having ethylene component units of 50 mol% or more, such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-propylene copolymer. coalescence, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer A coalescence etc. are illustrated.
ポリプロピレン系樹脂としては、プロピレン単独重合体、またはプロピレンと共重合可能な他のオレフィン等の成分との共重合体が挙げられる。プロピレンと共重合可能な他のオレフィンとしては、例えば、エチレンや、１－ブテン、イソブチレン、１－ペンテン、３－メチル－１－ブテン、１－ヘキセン、３，４－ジメチル－１－ブテン、１－ヘプテン、３－メチル－１－ヘキセンなどの炭素数４～１０のα－オレフィンが例示される。また上記共重合体は、ランダム共重合体であってもブロック共重合体等であってもよく、さらに二元共重合体のみならず三元共重合体であってもよい。 これらポリオレフィン系樹脂の中でも、柔軟性に優れ非緩衝物の保護性に優れるとの観点からポリエチレン系樹脂が好ましく、中でも、密度が９３５ｋｇ／ｍ３以下のポリエチレン系樹脂を主成分とするものが好ましい。具体的には、低密度ポリエチレン、直鎖状低密度ポリエチレン等を用いることが好ましく、さらには発泡性が良好な低密度ポリエチレンを用いることがより好ましい。なお、密度が９３５ｋｇ／ｍ３以下のポリエチレン系樹脂を「主成分」とするとは、ポリオレフィン系樹脂１００重量％に対して該ポリエチレン系樹脂の含有量が６０重量％以上であることをいう。また、ポリエチレン系樹脂の密度の下限は概ね８９０ｋｇ／ｍ３である。ポリエチレン系樹脂の密度の好ましい範囲は９００ｋｇ／ｍ３から９３０ｋｇ／ｍ３であり、さらには９１０ｋｇ／ｍ３から９２５ｋｇ／ｍ３であることが好ましく、特に９１３ｋｇ／ｍ３から９２３ｋｇ／ｍ３であることが好ましい。 Examples of polypropylene-based resins include propylene homopolymers and copolymers of propylene with other copolymerizable components such as olefins. Other olefins copolymerizable with propylene include, for example, ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1 C4-C10 α-olefins such as -heptene and 3-methyl-1-hexene are exemplified. The above copolymer may be a random copolymer, a block copolymer, or the like, and may be a terpolymer as well as a binary copolymer. Among these polyolefin-based resins, polyethylene-based resins are preferable from the viewpoint of excellent flexibility and protection of non-cushioning objects. Among them, polyethylene-based resins having a density of 935 kg/m 3 or less as a main component are preferable. . Specifically, it is preferable to use low-density polyethylene, linear low-density polyethylene, or the like, and it is more preferable to use low-density polyethylene with good foamability. The term "main component" consisting of a polyethylene-based resin having a density of 935 kg/m 3 or less means that the content of the polyethylene-based resin is 60% by weight or more based on 100% by weight of the polyolefin-based resin. Moreover, the lower limit of the density of polyethylene resin is approximately 890 kg/m 3 . The preferred range of density of the polyethylene resin is from 900 kg/m3 to 930 kg/ m3 , more preferably from 910 kg/ m3 to 925 kg/m3 , particularly from 913 kg/ m3 to 923 kg/ m3 . is preferred.
これらポリオレフィン系樹脂は、単独でも２種以上の混合物として使用することも可能であり、また同じ樹脂種で密度の異なるものを２種以上混合して使用することも可能である。ポリオレフィン系樹脂の２種以上の混合物の例としては、低密度ポリエチレンに直鎖状低密度ポリエチレンを混合したもの等が挙げられる。 These polyolefin-based resins may be used alone or as a mixture of two or more, and two or more of the same resin species but different densities may be used in combination. Examples of mixtures of two or more polyolefin resins include mixtures of low density polyethylene and linear low density polyethylene.
ポリオレフィン系樹脂のＭＦＲは、溶融張力を有しかつ押出機内での過度なせん断発熱を防止でき押出発泡に適した条件設定が容易となる傾向があるとの観点から、好ましくは０．０５から１５ｇ／１０分、より好ましくは０．５から１０ｇ／１０分、さらに好ましくは０．８から５．０ｇ／１０分、特に好ましくは１．０から３．０ｇ／１０分である。 The MFR of the polyolefin resin is preferably 0.05 to 15 g from the viewpoint that it has a melt tension and can prevent excessive shear heat generation in the extruder and tends to facilitate the setting of conditions suitable for extrusion foaming. /10 min, more preferably 0.5 to 10 g/10 min, still more preferably 0.8 to 5.0 g/10 min, particularly preferably 1.0 to 3.0 g/10 min.
本発明に用いられる無架橋ポリオレフィン系樹脂押出発泡体の平均気泡径の調整方法としては、気泡核形成剤の添加量、押出発泡時の温度条件、押出発泡時のせん断速度、ダイス開口部の形状等、従来公知の調整が有効である。 As a method for adjusting the average cell diameter of the non-crosslinked polyolefin resin extruded foam used in the present invention, the amount of cell nucleating agent added, the temperature conditions during extrusion foaming, the shear rate during extrusion foaming, and the shape of the die opening. For example, conventionally known adjustments are effective.
気泡核形成剤としては発泡体の製造に通常使用される無機物や化学発泡剤等を使用することが可能である。無機物としては、タルク、シリカ、炭酸カルシウム、ゼオライト、炭酸リチウム、亜鉛華などがあげられる。また、化学発泡剤は、有機系化学発泡剤と無機系化学発泡剤に分類され、有機系化学発泡剤としては、ＡＤＣＡ（アゾジカルボンアミド）、ＤＰＴ（Ｎ，Ｎ’－ジニトロペンタメチレンテトラミン）、ＯＢＳＨ（４，４’－オキシビスベンゼンスルホニルヒドラジド）等が良く用いられる。無機系化学発泡剤としては炭酸水素塩、炭酸塩、炭酸水素塩と有機酸塩との混合物などが挙げられる。これら気泡核形成剤は、単独或いは２種以上を併用することが出来る。気泡核形成剤は粉体状のものを直接添加しても良く、主材（原料樹脂成分）との混合性を考慮したマスターバッチを使用しても良い。特に下記する収縮防止剤を使用する場合には、気泡が粗大化し易い傾向があり、所望の気泡径を少ない添加量で達成しうる核形成効果の高いものが好ましい。少量で核形成効果が得られやすいとの観点から上記の中でも無機系化学発泡剤が好ましく、中でも、炭酸水素塩と有機酸塩との混合物が好ましく、特に炭酸水素ナトリウムとクエン酸塩との混合物が好ましい。気泡核形成効果を高めるために、炭酸水素ナトリウムとクエン酸塩との混合物と上記無機物とを併用することが好ましく、無機物としてはタルク、炭酸リチウムが好ましい。化学発泡剤はその濃度が１５重量％から５０重量％程度のマスターバッチとして使用されることが好ましい。このような気泡核形成効果の高い化学発泡剤マスターバッチとして「ＥＥ２７５Ｆ」（永和化成株式会社製）などが挙げられる。これら気泡核形成剤は使用量を多くすれば得られる発泡体の気泡径は小さくなる傾向にあるが、適性量を超えると独立気泡率の低下につながる。よって使用量としては原料樹脂成分１００重量部に対して０．１～１０重量部が好ましく、０．１～７重量部がより好ましく、０．１～５重量部であることがさらに好ましい。 As the cell nucleating agent, it is possible to use inorganic substances, chemical foaming agents, and the like that are commonly used in the production of foams. Examples of inorganic substances include talc, silica, calcium carbonate, zeolite, lithium carbonate, and zinc oxide. Chemical foaming agents are classified into organic chemical foaming agents and inorganic chemical foaming agents. Organic chemical foaming agents include ADCA (azodicarbonamide), DPT (N,N'-dinitropentamethylenetetramine), OBSH (4,4'-oxybisbenzenesulfonyl hydrazide) and the like are often used. Examples of inorganic chemical foaming agents include hydrogen carbonates, carbonates, mixtures of hydrogen carbonates and organic acid salts, and the like. These bubble nucleating agents can be used alone or in combination of two or more. The cell nucleating agent may be directly added in the form of powder, or may be used as a masterbatch in consideration of mixability with the main material (raw material resin component). In particular, when the shrinkage preventing agent described below is used, the air bubbles tend to be coarsened, and an agent having a high nucleation effect capable of achieving a desired air bubble diameter with a small addition amount is preferred. Inorganic chemical foaming agents are preferable among the above from the viewpoint that a nucleation effect can be easily obtained with a small amount, and among them, a mixture of a hydrogen carbonate and an organic acid salt is preferable, and a mixture of sodium hydrogen carbonate and a citrate is particularly preferable. is preferred. In order to enhance the bubble nucleation effect, it is preferable to use a mixture of sodium hydrogencarbonate and citrate in combination with the above inorganic substance, and talc and lithium carbonate are preferable as the inorganic substance. The chemical foaming agent is preferably used as a masterbatch with a concentration of about 15% to 50% by weight. "EE275F" (manufactured by Eiwa Kasei Co., Ltd.) and the like can be mentioned as a chemical blowing agent masterbatch having such a high bubble nucleation effect. If the amount of these cell nucleating agents used is increased, the resulting foam tends to have a smaller cell diameter, but exceeding the appropriate amount leads to a decrease in closed cell ratio. Therefore, the amount used is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, even more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the starting resin component.
その他、独立気泡率や発泡倍率の調整は、従来公知の方法にて調整することが可能である。具体的には、独立気泡率は、押出発泡時の溶融樹脂の押出温度の調整等が挙げられ、発泡倍率に関しては、発泡剤量および押出発泡時の溶融樹脂の押出温度の調整等が挙げられる。 In addition, the closed cell ratio and expansion ratio can be adjusted by conventionally known methods. Specifically, the closed cell ratio includes adjustment of the extrusion temperature of the molten resin during extrusion foaming, and the expansion ratio includes adjustment of the amount of foaming agent and the extrusion temperature of the molten resin during extrusion foaming. .
発泡剤としては、例えば、プロパン、ノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン、ヘキサン等の脂肪族炭化水素類；シクロペンタン、シクロブタン等の脂肪式環化水素類；ジメチルエーテル、ジエチルエーテル、メチルエチルエーテル等のエーテル類；メタノール、エタノール等のアルコール類；空気、窒素、炭酸ガス等の無機ガス；さらには水等が挙げられる。これらの発泡剤は単独で用いてもよく、また、２種類以上併用してもよい。これらのうちでも、所望の発泡倍率、独立気泡率、平均気泡径が得られやすいとの観点から脂肪族炭化水素類が好ましく、特にノルマルブタン、イソブタンが好ましい。発泡剤の添加量は、発泡剤の種類および目標とする発泡体の発泡倍率により異なる為適宜調整すればよいが、原料樹脂成分１００重量部に対して、０．５重量部以上２０重量部以下が好ましく、１重量部以上１５重量部以下であることがより好ましい。 Examples of foaming agents include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane; aliphatic cyclic hydrogens such as cyclopentane and cyclobutane; dimethyl ether, diethyl ether, methyl ethyl ether, and the like. alcohols such as methanol and ethanol; inorganic gases such as air, nitrogen and carbon dioxide; and water. These foaming agents may be used alone or in combination of two or more. Among these, aliphatic hydrocarbons are preferable, and normal butane and isobutane are particularly preferable, from the viewpoint that desired expansion ratio, closed cell ratio and average cell diameter can be easily obtained. The amount of the foaming agent to be added may vary depending on the type of the foaming agent and the expansion ratio of the target foam, so it may be adjusted as appropriate. is preferred, and it is more preferably 1 part by weight or more and 15 parts by weight or less.
本発明に用いられる発泡体には必要に応じて、発泡後の収縮を防止する目的で所謂収縮防止剤が使用されることが好ましい。特に従来発泡剤として使用されていたフロン系の発泡剤に代え、上記発泡剤を使用する場合には収縮防止剤を加えることが好ましい。 It is preferable to use a so-called shrinkage inhibitor for the purpose of preventing shrinkage after foaming, if necessary, in the foam used in the present invention. In particular, it is preferable to add an anti-shrinkage agent when using the above-mentioned foaming agent in place of the flon-based foaming agent conventionally used as the foaming agent.
前記収縮防止剤として、脂肪酸エステル、脂肪族アミン、脂肪酸アミドなどの従来周知のものが使用できる。 Conventionally well-known agents such as fatty acid esters, fatty amines and fatty acid amides can be used as the shrinkage inhibitor.
前記脂肪酸エステルとしては、炭素数８～３０の脂肪酸と水酸基を３～７個有する多価アルコールとのエステルが好ましい。炭素数８以上の脂肪酸としては、ラウリン酸、オレイン酸、ステアリン酸、ベヘン酸、リグノセリン酸、セロチン酸、ヘプタコ酸、モンタン酸、メリシン酸、ラクセル酸などが挙げられる。水酸基を３～７個有する多価アルコールとしては、グリセリン、ジグリセリン、トリグリセリン、エリトリットアラビット、キシリマアット、マンニット、ソルビット、ソルビタンなどが挙げられる。 これらのエステル化合物の中でも、これらの完全エステル化物よりは部分エステル化物、特にモノエステル化物がより顕著な収縮防止効果が得られるため好ましく、ステアリン酸モノグリセライド、ベヘン酸モノグリセライド、又はステアリン酸モノグリセライドとベヘン酸モノグリセライドの混合物が更に好ましい。 As the fatty acid ester, an ester of a fatty acid having 8 to 30 carbon atoms and a polyhydric alcohol having 3 to 7 hydroxyl groups is preferable. Examples of fatty acids having 8 or more carbon atoms include lauric acid, oleic acid, stearic acid, behenic acid, lignoceric acid, cerotic acid, heptakoic acid, montanic acid, melissic acid and laxeric acid. Examples of polyhydric alcohols having 3 to 7 hydroxyl groups include glycerin, diglycerin, triglycerin, erythritol arabit, xylimaat, mannitol, sorbitol and sorbitan. Among these ester compounds, partial esters, particularly monoesters, are preferable to full esters because they provide a more pronounced anti-shrinkage effect. Mixtures of monoglycerides are more preferred.
また、前記脂肪族アミンとしては、ドデシルアミン、テトラデシルアミン、ヘキサデシルアミン、オクタデシルアミン、エイコシルアミン、ドコシルアミン、Ｎ－メチルオクタデシルアミン、Ｎ－エチルオクタデシルアミン、ヘキサデシルプロピレンジアミン、オクタデシルプロピレンジアミンなどが挙げられる。 Examples of the aliphatic amine include dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, docosylamine, N-methyloctadecylamine, N-ethyloctadecylamine, hexadecylpropylenediamine, octadecylpropylenediamine, and the like. is mentioned.
また、前記脂肪酸アミドとしては、ステアリン酸アミド、オレイン酸アミド、エルカ酸アミド、メチレンビスステアリン酸アミド、エチレンビスステアリン酸アミド、ラウリン酸ビスアミド、などが挙げられる。 Examples of the fatty acid amide include stearic acid amide, oleic acid amide, erucic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, and lauric acid bisamide.
前記収縮防止剤の配合量は、原料樹脂成分１００重量部に対して０．３重量部以上が好ましく、より好ましくは０．５重量部以上、さらに好ましくは０．７重量部以上である。該配合量が少なすぎると収縮防止効果が不充分となる場合がある。一方、配合量が多すぎると収縮防止効果が頭打ちとなりコスト的にメリットがないばかりか得られる発泡体の圧縮応力等の強度物性を低下する場合がある。その為、該配合量の上限は、概ね３重量部が好ましく、より好ましくは２重量部である。 The amount of the shrinkage inhibitor to be blended is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, and still more preferably 0.7 parts by weight or more based on 100 parts by weight of the raw material resin component. If the amount is too small, the anti-shrinkage effect may be insufficient. On the other hand, if the blending amount is too large, the shrinkage prevention effect reaches a peak, and not only is there no merit in terms of cost, but also strength physical properties such as compressive stress of the obtained foam may be lowered. Therefore, the upper limit of the content is preferably approximately 3 parts by weight, more preferably 2 parts by weight.
また、本発明の効果を損なわない範囲で、ポリオレフィン系樹脂以外の他の合成樹脂を添加しても良い。ポリオレフィン系系樹脂以外の他の合成樹脂としては、ポリスチレン、スチレン－無水マレイン酸共重合体、スチレン－エチレン共重合体、スチレン－イソブチレン－スチレン共重合体、スチレン－イソブチレン共重合体、スチレン－ブタジエン－スチレン共重合体、スチレン－イソプレン－スチレン共重合体、及びそれらの水素添加物、等のスチレン系樹脂、ポリアミド系樹脂、熱可塑性ポリウレタン等が例示される。 In addition, other synthetic resins than polyolefin resins may be added as long as the effects of the present invention are not impaired. Synthetic resins other than polyolefin resins include polystyrene, styrene-maleic anhydride copolymer, styrene-ethylene copolymer, styrene-isobutylene-styrene copolymer, styrene-isobutylene copolymer, styrene-butadiene. Styrene-based resins such as -styrene copolymers, styrene-isoprene-styrene copolymers, and hydrogenated products thereof, polyamide-based resins, thermoplastic polyurethanes, and the like are exemplified.
本発明においては、必要に応じて、酸化防止剤、金属不活性剤、燐系加工安定剤、紫外線吸収剤、紫外線安定剤、蛍光増白剤、金属石鹸、制酸吸着剤などの安定剤、または架橋剤、連鎖移動剤、造核剤、滑剤、可塑剤、充填材、強化材、顔料、染料、難燃剤、帯電防止剤などの添加剤を添加してもよい。 In the present invention, stabilizers such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, ultraviolet absorbers, ultraviolet stabilizers, fluorescent whitening agents, metallic soaps, antacid adsorbents, etc. Alternatively, additives such as cross-linking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants and antistatic agents may be added.
本発明においては、着色剤の添加に制限はなく、着色剤を添加せずにナチュラル色とすることもできるし、青、赤、黒など着色剤を添加して所望の色とすることもできる。着色剤としては、例えば、ペリレン系有機顔料、アゾ系有機顔料、キナクリドン系有機顔料、フタロシアニン系有機顔料、スレン系有機顔料、ジオキサジン系有機顔料、イソインドリン系有機顔料、カーボンブラックなどが挙げられる。 In the present invention, the addition of a coloring agent is not limited, and a natural color can be obtained without adding a coloring agent, or a desired color can be obtained by adding a coloring agent such as blue, red, or black. . Examples of coloring agents include perylene organic pigments, azo organic pigments, quinacridone organic pigments, phthalocyanine organic pigments, threne organic pigments, dioxazine organic pigments, isoindoline organic pigments, and carbon black.
得られた無架橋ポリオレフィン系樹脂押出発泡体は、切削加工、打ち抜き加工等により、所望の形状に加工することで緩衝材として使用される。 The resulting non-crosslinked polyolefin resin extruded foam is processed into a desired shape by cutting, punching, or the like, and used as a cushioning material.
本発明の緩衝材は、上記無架橋ポリオレフィン系樹脂押出発泡体を使用するため、重量品やバランスの崩れ易い大物製品に対するグリップ力に優れるとともに、輸送時におけるこれら製品の底付きを防止する圧縮応力にも優れる。そのため、自動車部品、金属製工業用部品、大型プラスチック製品などの重量工業製品の輸送用緩衝材として最適である。また、本発明の緩衝材はリサイクル性を有するため、環境にも優しい。 Since the cushioning material of the present invention uses the non-crosslinked polyolefin resin extruded foam, it has excellent gripping power for heavy items and large items that tend to lose balance, and compressive stress that prevents these items from bottoming out during transportation. Also excellent. Therefore, it is most suitable as a cushioning material for transportation of heavy industrial products such as automobile parts, metal industrial parts, and large plastic products. Moreover, since the cushioning material of the present invention is recyclable, it is environmentally friendly.
以下に実施例によって本発明をより詳しく説明するが、本発明はこれらによって何ら制限されるものではない。 EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited by these examples.
実施例および比較例において、各種の評価方法に用いられた試験法および判定基準は次の通りである。 Test methods and criteria used for various evaluation methods in Examples and Comparative Examples are as follows.
＜メルトフローレート（ＭＦＲ）＞
ＭＦＲは、ＪＩＳ Ｋ ７２１０（１９９９）記載のＡ法の規定に準拠し、メルトインデクサーＳ－０１（東洋精機製作所製）を用い、１９０℃、一定荷重（２．１６ｋｇ）下でダイから一定時間に押し出される樹脂量から、１０分間に押し出される量に換算した値とした。
<Melt flow rate (MFR)>
MFR conforms to the provisions of A method described in JIS K 7210 (1999), using a melt indexer S-01 (manufactured by Toyo Seiki Seisakusho), 190 ° C., from the die under a constant load (2.16 kg) for a certain time. The value was obtained by converting the amount of resin extruded in 10 minutes into the amount extruded in 10 minutes.
なお、前記一定時間とは、メルトフローレートが０．５ｇ／１０分を超え１．０ｇ／１０分以下の場合は１２０秒間、１．０ｇ／１０分を超え３．５ｇ／１０分以下の場合は、６０秒間、３．５ｇ／１０分を超え１０ｇ／１０分以下の場合は３０秒間、１０ｇ／１０分を超え２５ｇ／１０分以下の場合は１０秒間、２５ｇ／１０分を超え１００ｇ／１０分以下の場合は５秒間、１００ｇ／１０分を超える場合は３秒間とした。 The fixed time is 120 seconds when the melt flow rate is more than 0.5 g/10 minutes and 1.0 g/10 minutes or less, and when it is more than 1.0 g/10 minutes and 3.5 g/10 minutes or less. is 60 seconds, 30 seconds if over 3.5 g/10 minutes and 10 g/10 minutes or less, 10 seconds if over 10 g/10 minutes and 25 g/10 minutes or less, and 100 g/10 over 25 g/10 minutes 5 seconds when less than 10 minutes, and 3 seconds when more than 100 g/10 minutes.
前記一定時間で切り取った切り取り片を３個採取しその平均値を算出することとし、一回の測定で３個採取できない場合は３個採取できるまで測定を継続するものとした。ある秒数で測定した際のメルトフローレートが対応する範囲に無かった場合は、そのメルトフローレートに応じた秒数で再度測定するものとした。 Three cut pieces cut out in the above-mentioned fixed period of time were collected, and the average value was calculated. If three pieces could not be collected in one measurement, the measurement was continued until three pieces could be collected. If the melt flow rate measured for a certain number of seconds was not within the corresponding range, the measurement was repeated for the number of seconds corresponding to the melt flow rate.
＜独立気泡率＞
実施例および比較例で得られた各発泡体から幅２０ｍｍ、厚み２０ｍｍ、長さ３０ｍｍの試験片を準備し、ＡＳＴＭ Ｄ２８５６に記載の方法に準拠し、エアピクノメータ（東京サイエンス株式会社製空気比較式比重計モデル１０００）を用いて、試験片の体積Ｖｃ（ｃｍ３）測定した。次に測定後の同じ試験片をエタノールの入ったメスシリンダー内に沈め、メスシリンダーの液面上昇分（水没法）から見かけ上の体積Ｖａ（ｃｍ３）を求め、下記式に従って独立気泡率（％）を求めた。
独立気泡率（％）＝（Ｖｃ／Ｖａ）×１００
なお、測定は３つの試験片について実施し、その平均値を発泡体の独立気泡率とした。
<Closed cell rate>
A test piece having a width of 20 mm, a thickness of 20 mm, and a length of 30 mm was prepared from each foam obtained in Examples and Comparative Examples, and measured in accordance with the method described in ASTM D2856 with an air pycnometer (air comparison manufactured by Tokyo Science Co., Ltd.). Using a hydrometer model 1000), the volume Vc (cm 3 ) of the test piece was measured. Next, the same test piece after measurement is submerged in a graduated cylinder containing ethanol, and the apparent volume Va (cm 3 ) is obtained from the amount of liquid level rise in the graduated cylinder (submersion method), and the closed cell ratio ( %) was obtained.
Closed cell rate (%) = (Vc/Va) x 100
In addition, the measurement was implemented about three test pieces, and the average value was made into the closed-cell rate of the foam.
＜発泡体密度＞
上記独立気泡率の測定で用いた試験片の重量Ｗ（ｇ）と上記水没法により求めた体積Ｖａ（ｃｍ３）とから下記式により求めた。
発泡体密度（ｇ／ｃｍ３）＝Ｗ／Ｖａ
<Foam density>
It was obtained by the following formula from the weight W (g) of the test piece used in the measurement of the closed cell ratio and the volume Va (cm 3 ) obtained by the above water immersion method.
Foam density (g/cm 3 ) = W/Va
＜発泡倍率＞
上記発泡体密度（ｇ／ｃｍ３）と樹脂密度（ｇ／ｃｍ３）から下記式により求めた。
発泡倍率（倍）＝樹脂密度／発泡体密度
<Expansion ratio>
It was obtained from the foam density (g/cm 3 ) and the resin density (g/cm 3 ) according to the following formula.
Foaming ratio (times) = resin density / foam density
＜平均気泡径＞
実施例および比較例で得られた発泡体を、押出方向と直行する任意の断面３箇所につき、押出方向長さ２０ｍｍに切断し、サンプルＡを作製した。さらにサンプルＡから下記測定箇所につきに各辺が５～１０ｍｍの立方体サンプルＢを切り出した。サンプルＢにつき各々の観察面（厚み方向、幅方向、押出方向）を両刃カミソリ［フェザー製、ハイステンレス両刃］を用いて、気泡膜（セル膜）が破壊されないように充分注意して切断し、その切断面をマイクロスコープ［キーエンス社製、ＶＨＸ－９００］にて観察した。得られた画像において、長さ４０００μｍの線分を引き、該線分が通る気泡数ｎを測定し、下記式により気泡径を算出した。
<Average bubble diameter>
The foams obtained in Examples and Comparative Examples were cut into 20 mm lengths in the direction of extrusion at three arbitrary cross-sections perpendicular to the direction of extrusion to prepare samples A. Furthermore, a cubic sample B with each side of 5 to 10 mm was cut out from the sample A at the following measurement points. Each observation surface (thickness direction, width direction, extrusion direction) of sample B was cut with a double-edged razor [feather made, high stainless steel double-edged blade], being careful not to destroy the bubble membrane (cell membrane), The cut surface was observed with a microscope [VHX-900 manufactured by Keyence Corporation]. In the obtained image, a line segment with a length of 4000 μm was drawn, the number of bubbles n passed by the line segment was measured, and the bubble diameter was calculated by the following formula.
気泡径（μｍ）＝４０００／ｎ
この測定を各測定点につき厚み方向、幅方向、押出方向について実施し、これらの相加平均値を平均気泡径（μｍ）とした。
※）測定箇所：発泡体の押出方向と直行する任意断面３箇所の各々において下記５点の平均気泡径を測定した。
Bubble diameter (μm) = 4000/n
This measurement was carried out for each measurement point in the thickness direction, width direction, and extrusion direction, and the arithmetic mean value of these was taken as the average cell diameter (μm).
*) Measurement points: The average cell diameter at the following five points was measured at each of three arbitrary cross-section points perpendicular to the extrusion direction of the foam.
・中央部（測定点１）
・中央部と幅方向両端部の中間部（測定点２，３）
・中央部と厚み方向上下端部の中間部（測定点４，５）
・Central part (measurement point 1)
・Middle part between the central part and both ends in the width direction (measurement points 2 and 3)
・Intermediate part between the central part and the upper and lower ends in the thickness direction (measurement points 4 and 5)
＜ボイド評価＞
発泡体の押出方向と直行する断面を平均気泡径の測定と同様にして観察し、気泡が連通して発生した空洞で平均気泡径の３．２４６倍以上のものをボイドとしその有無を評価した。
<Void evaluation>
The cross section perpendicular to the extrusion direction of the foam was observed in the same manner as the measurement of the average cell diameter, and the presence or absence of voids was evaluated as voids generated by communicating cells that were 3.246 times or more the average cell diameter. .
＜緩衝材としての物性評価＞
発泡体から幅５０ｍｍ、厚み２５ｍｍ、長さ２００ｍｍの緩衝材サンプルを切り出し、下記評価を実施した。
<Evaluation of physical properties as a cushioning material>
A cushioning material sample having a width of 50 mm, a thickness of 25 mm, and a length of 200 mm was cut out from the foam and subjected to the following evaluations.
１）外観
緩衝材サンプルの切り出し面を下記基準により目視評価した。
Ａ・・・気泡が均一微細で、表面が滑らかな印象を与える。
Ｂ・・・ＡとＣの間。
Ｃ・・・気泡が粗く一つ一つが明瞭で、気泡による表面凹凸が目視で容易に確認される。
1) Appearance
The cut surface of the cushioning material sample was visually evaluated according to the following criteria.
A: Air bubbles are uniform and fine, giving an impression that the surface is smooth.
B: between A and C;
C: Bubbles are coarse and each one is distinct, and surface unevenness due to bubbles can be easily visually confirmed.
２）動摩擦係数
表面性試験機（新東科学社製 ＨＥＩＤＯＮ ＴＲＩＢＯＧＥＡＲ Ｔｙｐｅ１４）を使用し、ＡＳＴＭ Ｄ１８９４に準拠し測定した。上記緩衝材サンプルから、幅５０ｍｍ、厚み９ｍｍ、長さ２００ｍｍの試験片を切り出した。摩擦は表面性試験機付属のＡＳＴＭ平面圧子が試験片上を水平移動することによって生じさせた。測定は、荷重１１５０ｇ（平面圧子：１５０ｇ、錘：１０００ｇ）、試験速度１５０ｍｍ／ｍｉｎ、距離７０ｍｍにて実施した。測定開始後１．５秒から５秒までの動摩擦力の平均値と試験荷重から動摩擦係数を算出した。同様の測定を３回実施しこれらの平均値を発泡体の動摩擦係数とし、下記基準で評価した。
Ａ・・・０．３６０以上
Ｂ・・・０．３４０以上０．３６０未満
Ｃ・・・０．３１０以上０．３４０未満
Ｄ・・・０．３１０未満
2) Dynamic Friction Coefficient Measured according to ASTM D1894 using a surface property tester (HEIDON TRIBOGEAR Type 14, manufactured by Shinto Kagaku Co., Ltd.). A test piece having a width of 50 mm, a thickness of 9 mm, and a length of 200 mm was cut from the cushioning material sample. Friction was produced by horizontal movement of an ASTM flat indenter attached to the surface tester over the specimen. The measurement was performed at a load of 1150 g (flat indenter: 150 g, weight: 1000 g), a test speed of 150 mm/min, and a distance of 70 mm. The dynamic friction coefficient was calculated from the average value of the dynamic friction force from 1.5 seconds to 5 seconds after the start of measurement and the test load. The same measurement was carried out three times, and the average value of these was taken as the dynamic friction coefficient of the foam, and evaluated according to the following criteria.
A: 0.360 or more B: 0.340 or more and less than 0.360 C: 0.310 or more and less than 0.340 D: less than 0.310
３）圧縮応力比
上記緩衝材サンプルから幅５０ｍｍ×長さ５０ｍｍ×厚み２５ｍｍの試験片を切り出し、オートグラフ（島津製作所製 オートグラフＡＧ－Ｘ／Ｒ、負荷容量２０ｋＮ）を使用し、ＪＩＳ Ｋ６７６７に準拠し圧縮応力を測定した（試験速度１０ｍｍ／ｍｉｎ、伸び原点（測定開始点）を試験力フルスケール（２０ｋＮ）の０．３％（６０Ｎ）に設定）。得られた圧縮応力データから、歪０％と４％の圧縮応力の差Ｓ０４（ＭＰａ）と、歪２５％と５０％との圧縮応力の差Ｓ２５５０（ＭＰａ）の比を下記式にて求めた。
圧縮応力比＝Ｓ２５５０／Ｓ０４
3) Compressive stress ratio A test piece of width 50 mm x length 50 mm x thickness 25 mm is cut out from the above buffer material sample, and an autograph (manufactured by Shimadzu Autograph AG-X/R, load capacity 20 kN) is used, and according to JIS K6767. The compressive stress was measured according to the test speed (test speed 10 mm/min, elongation origin (measurement start point) set at 0.3% (60 N) of test force full scale (20 kN)). From the obtained compressive stress data, the ratio of the difference S04 (MPa) in compressive stress between 0% and 4% strain and the difference S2550 (MPa) in compressive stress between 25% and 50% strain was obtained by the following formula. .
Compressive stress ratio = S2550/S04
（実施例１）
低密度ポリエチレン（宇部丸善ポリエチレン製「Ｃ４７０」、ＭＦＲ２．０ｇ／１０分、密度９１８ｋｇ／ｍ３）１００重量部に、気泡核形成剤として化学発泡剤（永和化成製 ＥＥ２７５Ｆ、重曹－クエン酸系熱分解型発泡剤マスターバッチ）３．０重量部、収縮防止剤としてステアリン酸モノグリセライド１．０重量部加えたものを、Φ４０二軸－φ９０ｍｍ単軸タンデム押出機に供給した。２３０℃に設定した第１押出機（φ４０二軸）中に溶融させた後、発泡剤としてのイソブタンを３．５重量部圧入混合し、９７℃に設定した第２押出機（φ９０ｍｍ）中で冷却した後、押出機先端に接続された矩形ダイ（開口部５０ｍｍ×４ｍｍ）より、大気圧下に吐出量５０ｋｇ／時間で押出した。ダイから押出された発泡体を引取機で引き取りながら成形ダイにより板状発泡体を得た。得られた発泡体は、ボイドが無くかつ独立気泡率も高かった。得られた発泡体について各種物性を測定・評価した結果を表１に示す。
(Example 1)
To 100 parts by weight of low-density polyethylene ("C470" manufactured by Ube Maruzen Polyethylene, MFR 2.0 g/10 min, density 918 kg/m 3 ), a chemical foaming agent (EE275F manufactured by Eiwa Kasei, sodium bicarbonate-citric acid heat 3.0 parts by weight of decomposable foaming agent masterbatch) and 1.0 parts by weight of stearic acid monoglyceride as an anti-shrinkage agent were added to a Φ40 twin-Φ90 mm single-screw tandem extruder. After melting in the first extruder (φ40 twin screw) set at 230°C, 3.5 parts by weight of isobutane as a foaming agent is injected and mixed, and then in the second extruder (φ90 mm) set at 97°C. After cooling, it was extruded at a discharge rate of 50 kg/hour under atmospheric pressure from a rectangular die (opening 50 mm×4 mm) connected to the tip of the extruder. A plate-like foam was obtained by a forming die while the foam extruded from the die was taken by a take-up machine. The resulting foam was free of voids and had a high closed cell content. Table 1 shows the results of measuring and evaluating various physical properties of the resulting foam.
（実施例２～３）
表１の通り配合を調整した以外は実施例１と同様にして発泡体を得た。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Examples 2-3)
A foam was obtained in the same manner as in Example 1 except that the formulation was adjusted as shown in Table 1. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（実施例４）
イソブタンの添加量を２．０部に変更した以外は実施例１と同様にして発泡体を得た。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Example 4)
A foam was obtained in the same manner as in Example 1, except that the amount of isobutane added was changed to 2.0 parts. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（実施例５～６）
表１の通り配合を調整した以外は実施例１と同様にして発泡体を得た。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Examples 5-6)
A foam was obtained in the same manner as in Example 1 except that the formulation was adjusted as shown in Table 1. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（比較例１）
気泡核形成剤の添加量を０．３３部に変更した以外は実施例１と同様にして平均気泡径の大きな発泡体を得た。この平均気泡径の大きな発泡体から作製した緩衝材サンプルは気泡に基づく表面凹凸が目立ち外観が悪く、かつ動摩擦係数も低く、圧縮応力比も低いものであった。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Comparative example 1)
A foam having a large average cell diameter was obtained in the same manner as in Example 1, except that the amount of cell nucleating agent added was changed to 0.33 parts. The cushioning material sample produced from the foam having a large average cell diameter had a poor appearance due to conspicuous surface irregularities due to the cells, a low dynamic friction coefficient, and a low compressive stress ratio. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（比較例２）
押出条件、成形条件を調整した以外は実施例１と同様にして独立気泡率の低い発泡体を得た。得られた発泡体についてボイド有無を評価したところ、ボイドは無い発泡体であった。このボイドは無いが独立気泡率の低い発泡体から作製した緩衝材サンプルは圧縮応力比が低いものであった。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Comparative example 2)
A foam with a low closed cell content was obtained in the same manner as in Example 1, except that the extrusion conditions and molding conditions were adjusted. When the presence or absence of voids was evaluated for the resulting foam, the foam was free of voids. This void-free cushioning material sample made from a foam with a low closed cell content had a low compressive stress ratio. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（比較例３）
気泡核形成剤の添加量を１．０部に変更した以外は実施例４と同様にして平均気泡径の大きな発泡体を得た。この平均気泡径の大きな発泡体から作製した緩衝材サンプルは気泡に基づく表面凹凸が目立ち外観が悪く、かつ動摩擦係数も低く、圧縮応力比も低いものであった。得られた発泡体について同様に各種物性を測定・評価した結果を表１に示す。
(Comparative Example 3)
A foam having a large average cell diameter was obtained in the same manner as in Example 4, except that the amount of cell nucleating agent added was changed to 1.0 part. The cushioning material sample produced from the foam having a large average cell diameter had a poor appearance due to conspicuous surface irregularities due to the cells, a low dynamic friction coefficient, and a low compressive stress ratio. Table 1 shows the results of similarly measuring and evaluating various physical properties of the resulting foam.
（参考例１）
市販の無架橋ポリエチレン発泡体（旭化成製、サンテックフォーム「Ｑ１５」）について各種物性を同様に測定・評価した結果を表１に示す。比較例１同様に平均気泡径が荒いため、外観に乏しく動摩擦係数も低いものであった。
(Reference example 1)
Table 1 shows the results of similarly measuring and evaluating various physical properties of commercially available non-crosslinked polyethylene foam (Suntech Foam "Q15" manufactured by Asahi Kasei Corporation). Similar to Comparative Example 1, since the average cell diameter was large, the appearance was poor and the coefficient of dynamic friction was low.
Claims (16)
前記無架橋ポリオレフィン系樹脂押出発泡体は、高密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－プロピレン共重合体、エチレン－プロピレン－ブテン－１共重合体、エチレン－ブテン－１共重合体、エチレン－ヘキセン－１共重合体、エチレン－４－メチルペンテン－１共重合体およびエチレン－オクテン－１共重合体からなる群から選択される１種以上のポリエチレン系樹脂を含み、
前記無架橋ポリオレフィン系樹脂押出発泡体におけるポリオレフィン系樹脂１００重量％は、前記ポリエチレン系樹脂のうち密度が９３５ｋｇ／ｍ ３ 以下のポリエチレン系樹脂を６０重量％以上含む、緩衝材。
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上 A cushioning material using a non-crosslinked polyolefin resin extruded foam that satisfies the following a) to d),
The non-crosslinked polyolefin resin extruded foam includes high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-propylene-butene-1 copolymer. one selected from the group consisting of coalescence, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer and ethylene-octene-1 copolymer Including the above polyethylene resin ,
100% by weight of the polyolefin resin in the extruded non-crosslinked polyolefin resin foam contains 60% by weight or more of the polyethylene resin having a density of 935 kg/m 3 or less among the polyethylene resins.
a) Foaming ratio of 5 times or more and 30 times or less b) Average cell diameter of 100 μm or more and 600 μm or less c) Closed cell ratio of 70% or more d) Thickness of 20 mm or more
前記無架橋ポリオレフィン系樹脂押出発泡体は、高密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－プロピレン共重合体、エチレン－プロピレン－ブテン－１共重合体、エチレン－ブテン－１共重合体、エチレン－ヘキセン－１共重合体、エチレン－４－メチルペンテン－１共重合体およびエチレン－オクテン－１共重合体からなる群から選択される１種以上のポリエチレン系樹脂を含み、
前記無架橋ポリオレフィン系樹脂押出発泡体におけるポリオレフィン系樹脂１００重量％は、前記ポリエチレン系樹脂のうち密度が９３５ｋｇ／ｍ ３ 以下のポリエチレン系樹脂を６０重量％以上含む、緩衝材。
ｅ）発泡倍率が５倍以上３０倍以下
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦２０７ －式（１）
ｇ）独立気泡率が７０％以上
ｈ）厚みが２０ｍｍ以上 A cushioning material using a non-crosslinked polyolefin resin extruded foam satisfying the following e) to h),
The non-crosslinked polyolefin resin extruded foam includes high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-propylene-butene-1 copolymer. one selected from the group consisting of coalescence, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer and ethylene-octene-1 copolymer Including the above polyethylene resin ,
100% by weight of the polyolefin resin in the extruded non-crosslinked polyolefin resin foam contains 60% by weight or more of the polyethylene resin having a density of 935 kg/m 3 or less among the polyethylene resins.
e) The expansion ratio is 5 times or more and 30 times or less f) The average cell diameter that satisfies the relationship of the following formula (1) - (33.3 x expansion ratio) ≤ 207 - formula (1)
g) Closed cell ratio of 70% or more h) Thickness of 20 mm or more
前記無架橋ポリオレフィン系樹脂押出発泡体はポリオレフィン系樹脂を含み、
前記ポリオレフィン系樹脂１００重量％において低密度ポリエチレンおよび／または直鎖状低密度ポリエチレンが６０重量％以上含まれる、緩衝材。
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上 A cushioning material using a non-crosslinked polyolefin resin extruded foam that satisfies the following a) to d),
The non-crosslinked polyolefin resin extruded foam contains a polyolefin resin,
A cushioning material containing 60% by weight or more of low-density polyethylene and/or linear low-density polyethylene in 100% by weight of the polyolefin resin.
a) Foaming ratio of 5 times or more and 30 times or less b) Average cell diameter of 100 μm or more and 600 μm or less c) Closed cell ratio of 70% or more d) Thickness of 20 mm or more
前記無架橋ポリオレフィン系樹脂押出発泡体はポリオレフィン系樹脂を含み、
前記ポリオレフィン系樹脂１００重量％において低密度ポリエチレンおよび／または直鎖状低密度ポリエチレンが６０重量％以上含まれる、緩衝材。
ｅ）発泡倍率が５倍以上３０倍以下
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦２０７ －式（１）
ｇ）独立気泡率が７０％以上
ｈ）厚みが２０ｍｍ以上 A cushioning material using a non-crosslinked polyolefin resin extruded foam satisfying the following e) to h),
The non-crosslinked polyolefin resin extruded foam contains a polyolefin resin,
A cushioning material containing 60% by weight or more of low-density polyethylene and/or linear low-density polyethylene in 100% by weight of the polyolefin resin.
e) The expansion ratio is 5 times or more and 30 times or less f) The average cell diameter that satisfies the relationship of the following formula (1) - (33.3 x expansion ratio) ≤ 207 - formula (1)
g) Closed cell ratio of 70% or more h) Thickness of 20 mm or more
圧縮応力比≧０．４×Ｌｎ（発泡倍率）－０．４ －式（２）
圧縮応力比＝Ｓ２５５０／Ｓ０４
Ｓ０４：歪０％と４％での圧縮応力の差（ＭＰａ）
Ｓ２５５０：歪２５％と５０％での圧縮応力の差（ＭＰａ） The cushioning material according to any one of claims 1 to 7 , wherein the non-crosslinked polyolefin resin extruded foam satisfies the relationship of the following formula (2).
Compressive stress ratio ≥ 0.4 × Ln (expansion ratio) -0.4 - formula (2)
Compressive stress ratio = S2550/S04
S04: difference in compressive stress at strain 0% and 4% (MPa)
S2550: difference in compressive stress at 25% and 50% strain (MPa)
前記重量品は、自動車部品、金属製工業用部品、大型プラスチック製品からなる群から選択される１種以上である、請求項１～１１のいずれか一項に記載の緩衝材。 The cushioning material is for transporting heavy goods,
The cushioning material according to any one of claims 1 to 11 , wherein the heavy goods are one or more selected from the group consisting of automobile parts, metal industrial parts, and large plastic products.
次のａ）～ｄ）の要件を満たし、
前記樹脂組成物が気泡核形成剤として化学発泡剤を含み、
前記化学発泡剤が炭酸水素ナトリウムとクエン酸塩との混合物であり、
前記ポリオレフィン系樹脂は、高密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－プロピレン共重合体、エチレン－プロピレン－ブテン－１共重合体、エチレン－ブテン－１共重合体、エチレン－ヘキセン－１共重合体、エチレン－４－メチルペンテン－１共重合体およびエチレン－オクテン－１共重合体からなる群から選択される１種以上のポリエチレン系樹脂を含み、
前記ポリオレフィン系樹脂１００重量％は、前記ポリエチレン系樹脂のうち密度が９３５ｋｇ／ｍ ３ 以下のポリエチレン系樹脂を６０重量％以上含む、無架橋ポリオレフィン系樹脂押出発泡体の製造方法。
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上 A step of melt-kneading a polyolefin resin and a foaming agent containing an aliphatic hydrocarbon, and extruding under reduced pressure after cooling the molten resin composition containing the foaming agent obtained in the melt-kneading step. including the step of foaming and molding the foam,
Satisfy the following requirements a) to d),
The resin composition contains a chemical foaming agent as a cell nucleating agent,
the chemical blowing agent is a mixture of sodium bicarbonate and citrate;
The polyolefin resins include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-butene. -1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer and ethylene-octene-1 copolymer, at least one polyethylene resin selected from the group consisting of including
100% by weight of the polyolefin-based resin includes 60% by weight or more of the polyethylene-based resin having a density of 935 kg/m 3 or less among the polyethylene-based resins.
a) Foaming ratio of 5 times or more and 30 times or less b) Average cell diameter of 100 μm or more and 600 μm or less c) Independent cell ratio of 70% or more d) Thickness of 20 mm or more
次のｅ）～ｈ）の要件を満たし、
前記樹脂組成物が気泡核形成剤として化学発泡剤を含み、
前記化学発泡剤が炭酸水素ナトリウムとクエン酸塩との混合物であり、
前記ポリオレフィン系樹脂は、高密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－プロピレン共重合体、エチレン－プロピレン－ブテン－１共重合体、エチレン－ブテン－１共重合体、エチレン－ヘキセン－１共重合体、エチレン－４－メチルペンテン－１共重合体およびエチレン－オクテン－１共重合体からなる群から選択される１種以上のポリエチレン系樹脂を含み、
前記ポリオレフィン系樹脂１００重量％は、前記ポリエチレン系樹脂のうち密度が９３５ｋｇ／ｍ ３ 以下のポリエチレン系樹脂を６０重量％以上含む、無架橋ポリオレフィン系樹脂押出発泡体の製造方法。
ｅ）発泡倍率が５倍以上３０倍以下
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦２０７ －式（１）
ｇ）独立気泡率が７０％以上
ｈ）厚みが２０ｍｍ以上 A step of melt-kneading a polyolefin resin and a foaming agent containing an aliphatic hydrocarbon, and extruding under reduced pressure after cooling the molten resin composition containing the foaming agent obtained in the melt-kneading step. including the step of foaming and molding the foam,
Satisfy the following requirements e) to h),
The resin composition contains a chemical foaming agent as a cell nucleating agent,
the chemical blowing agent is a mixture of sodium bicarbonate and citrate;
The polyolefin resins include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-butene. -1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer and ethylene-octene-1 copolymer, at least one polyethylene resin selected from the group consisting of including
100% by weight of the polyolefin-based resin includes 60% by weight or more of the polyethylene-based resin having a density of 935 kg/m 3 or less among the polyethylene-based resins.
e) Foaming ratio of 5 times or more and 30 times or less
f) satisfying the relationship of the following formula (1)
Average bubble diameter - (33.3 x foaming ratio) ≤ 207 - formula (1)
g) Closed cell ratio of 70% or more h) Thickness of 20 mm or more
次のａ）～ｄ）およびｆ）の要件を満たし、
前記樹脂組成物が気泡核形成剤として化学発泡剤を含み、
前記化学発泡剤が炭酸水素ナトリウムとクエン酸塩との混合物であり、
前記ポリオレフィン系樹脂１００重量％は、低密度ポリエチレンおよび／または直鎖状低密度ポリエチレンを６０重量％以上含む、無架橋ポリオレフィン系樹脂押出発泡体の製造方法。
ａ）発泡倍率が５倍以上３０倍以下
ｂ）平均気泡径が１００μｍ以上６００μｍ以下
ｃ）独立気泡率が７０％以上
ｄ）厚みが２０ｍｍ以上
ｆ）下記式（１）の関係を満たす
平均気泡径－（３３．３×発泡倍率）≦２０７ －式（１） A step of melt-kneading a polyolefin resin and a foaming agent containing an aliphatic hydrocarbon, and extruding under reduced pressure after cooling the molten resin composition containing the foaming agent obtained in the melt-kneading step. including the step of foaming and molding the foam,
meet the following requirements a) to d) and f) ,
The resin composition contains a chemical foaming agent as a cell nucleating agent,
the chemical blowing agent is a mixture of sodium bicarbonate and citrate ;
A method for producing a non-crosslinked polyolefin resin extruded foam, wherein 100% by weight of the polyolefin resin contains 60% by weight or more of low density polyethylene and/or linear low density polyethylene .
a) Foaming ratio of 5 times or more and 30 times or less b) Average cell diameter of 100 μm or more and 600 μm or less c) Closed cell ratio of 70% or more d) Thickness of 20 mm or more
f) satisfying the relationship of the following formula (1)
Average bubble diameter - (33.3 x foaming ratio) ≤ 207 - formula (1)
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