【発明の詳細な説明】[Detailed description of the invention]
本発明は曇り度が大きく光沢度が小さく書画性
にも優れたポリオレフインフイルムの成形に好適
な樹脂組成物に関する。
ポリオレフインフイルムは優れた機械的、化学
的性質、経済性等から広く使用され、特に包装用
に大きな分野を有し、また紙、アルミ箔のような
異種材料にラミネートされ複合材料としての用途
もあり、さらに合成紙の開発も進められている。
包装用として要求される性質として、内容物の
保護の他に外観が重要であり、ゴミ袋、シヨツピ
ングバツク等の場合は内容物が透視されないこと
が好ましくそのためにはフイルムの曇り度を大き
くする必要がある。
本発明者達はこの問題を解決すべく種々検討の
結果、メルトインデツクス0.002〜0.1g／10min、
密度0.920g／c.c.以上のエチレン単独重合体又はエ
チレンと他のα―オレフインとの共重合体20〜70
重量部とプロピレン単独重合体又はプロピレンと
他のα―オレフインとの共重合体30〜80重量部か
らなる樹脂組成物を空冷インフレーシヨン法によ
り成形すれば、曇り度が大きく光沢が小さく書画
性にも優れたフイルムが得られることを見出した
のである。
本発明で用いるポリエチレンはエチレン単独重
合体又はエチレンと１種又は２種以上のC3〜C8
のα―オレフインとの共重合体であり、メルトイ
ンデツクスは0.002〜0.1ｇ／10minであつて、
0.002g／10min未満ではポリプロピレンとの混合
が不均一となりフイルムにゲル、フイツシユアイ
が発生したり流動性が不足して成形が困難となる
場合があり、0.1g／10minを越えるとバブルが不
安定となる。又、密度は0.920g／c.c.好ましくは
0.930g／c.c.以上であつて、0.920g／c.c.未満では大
きい曇り度、小さな光沢度、書画性は得られな
い。
ポリプロピレンはプロピレン単独重合体又はプ
ロピレンと１種又は２種以上のC2〜C6のα―オ
レフイン10重量％以下との共重合体であり、メル
トフローインデツクス10g／10min以下がバブル
の安定上好ましい。
本発明の樹脂組成物においてはポリエチレン20
〜70重量部、ポリプロピレン30〜80重量部とする
ことが必要であり、この範囲を外れると大きい曇
り度、小さな光沢度、書画性は得られない。又ポ
リエチレンの比率が大きい程、メルトインデツク
スが低い程フイルムの耐衝撃性は向上するし、さ
らにポリエチレンの密度が大きい程、ポリエチレ
ンとポリプロピレンの屈折率の差が大きくなりフ
イルム内部の曇り度が大きくなるので適宜調整も
できる。
本発明の樹脂組成物は空冷インフレーシヨン法
によつて前記種々の特性を有するフイルムを成形
できるのであり、水冷インフレーシヨン法、水冷
Ｔダイ法等によつてはかかるフイルムは得られな
い。成形に当つては通常の装置、操作が適用でき
る。
得られるフイルムの表面には直径0.5〜20μの突
起が多数形成され、この微細な突起によつて曇り
度が大きくなり光沢度が小さくなるものと考えら
れるが、好ましい外観、感触をもたらすものであ
る。さらに鉛筆、ボールペン等で書画が可能であ
り大きな曇り度のため判読し易く、指による摩擦
で消えることもなくコピーもできて合成紙として
の用途も期待できる。しかもフイルムのかかる効
果はフイルムの厚みに殆ど無関係に発現するとい
う利点も有する。
以下に実施例，比較例を挙げて本発明をさらに
詳細に説明する。なお諸物性の測定方法は以下の
とおりである。
メルトインデツクス JIS K6758
メルトフローインデツクス JIS K6760（5.1）
密度 JIS K6460（5.2.4）
曇り度 ASTM Ｄ―1003
光沢度 ASTM Ｄ―523T（60゜）
実施例 １
メルトフローインデツクス0.7g／10minのプロ
ピレンホモポリマー60重量部とメルトインデツク
ス0.005g／10min、密度0.935g／c.c.のエチレンと
ブテン―１の中低圧法による共重合体40重量部を
50mmの単軸押出機で混合した。得られた組成物
のメルトフローインデツクス（230℃，2.16Kg）
は0.07g／10minであつた。この組成物を用いて
50mmの空冷インフレーシヨンフイルム成形機で
ダイス温度240℃，ブローアツプ比３として30μ
厚のフイルムを成形した。
得られたフイルムは、曇り度95.4％、光沢度
4.9％、衝撃強度152Kg・cm／mmであり、不透明で
光沢のない強度の優れた良質なものであつた。こ
のフイルムには鉛筆及びボールペンで字を明瞭に
書け指で摩擦しても消えなかつた。
又フイルムの表面を走査型電子顕微鏡（2000
倍）で観察したところ0.5μ〜数μの無数の突起が
認められた。さらに昇温速度１℃／minで加熱し
ながら光学顕微鏡（1000倍）で観察したところ突
起が先ず融解したので突起は融点の低いポリエチ
レンが主成分であることがわかつた。
実施例 ２
フイルムの厚みを10μとした他は実施例１と同
様に行なつたが、フイルムの曇り度93.2％、光沢
度5.1％、衝撃強度75Kg・cm／mmを示し、フイル
ムの厚みが実施例１の1/3にもかかわらず曇り度
の低下は僅かであり、書画性も実施例１と同様で
あつた。
実施例 ３〜７
実施例１のポリエチレンの代りに表１に示すポ
リエチレンを記載量用いて実施例１と同様に行な
つたところ、表１に示すように諸物性に優れ、書
画性も実施例１と同様であつた。
The present invention relates to a resin composition suitable for molding a polyolefin film having high haze, low gloss, and excellent calligraphy. Polyolefin film is widely used due to its excellent mechanical, chemical properties, and economic efficiency, and has a particularly large field of use in packaging. It is also used as a composite material when laminated with different materials such as paper and aluminum foil. Furthermore, the development of synthetic paper is also progressing. In addition to protecting the contents, appearance is important as a property required for packaging, and in the case of garbage bags, shopping bags, etc., it is preferable that the contents cannot be seen through. There is a need to. As a result of various studies to solve this problem, the inventors of the present invention found that the melt index was 0.002 to 0.1 g/10 min,
Ethylene homopolymer or copolymer of ethylene and other α-olefins with a density of 0.920 g/cc or more 20 to 70
If a resin composition consisting of 30 to 80 parts by weight of a propylene homopolymer or a copolymer of propylene and another α-olefin is molded by an air-cooled inflation method, the haze is high, the gloss is low, and the calligraphy property is high. They discovered that excellent films could also be obtained. The polyethylene used in the present invention is an ethylene homopolymer or ethylene and one or more types of C 3 to C 8
It is a copolymer with α-olefin of
If it is less than 0.002g/10min, the mixture with polypropylene will be uneven, which may cause gel or stickiness on the film, or the film may lack fluidity, making molding difficult.If it exceeds 0.1g/10min, bubbles may become unstable. Become. Also, the density is preferably 0.920g/cc
If it is 0.930 g/cc or more and less than 0.920 g/cc, high haze, low gloss, and calligraphic quality cannot be obtained. Polypropylene is a propylene homopolymer or a copolymer of propylene and one or more C2 to C6 α-olefins of 10% by weight or less, and a melt flow index of 10g/10min or less is important for bubble stability. preferable. In the resin composition of the present invention, polyethylene 20
70 parts by weight of polypropylene and 30 to 80 parts by weight of polypropylene. Outside this range, high haze, low gloss, and calligraphic quality cannot be obtained. Also, the higher the proportion of polyethylene and the lower the melt index, the better the impact resistance of the film will be, and the higher the density of polyethylene, the greater the difference in refractive index between polyethylene and polypropylene, and the greater the degree of haze inside the film. Therefore, adjustments can be made as appropriate. The resin composition of the present invention can be molded into a film having the above-mentioned various properties by an air-cooled inflation method, but such a film cannot be obtained by a water-cooled inflation method, a water-cooled T-die method, or the like. For molding, ordinary equipment and operations can be applied. Many protrusions with a diameter of 0.5 to 20μ are formed on the surface of the resulting film, and it is thought that these minute protrusions increase haze and reduce gloss, but they provide a desirable appearance and feel. . Furthermore, it can be used for drawing and calligraphy with pencils, ballpoint pens, etc., is easy to read due to its high degree of haze, and can be copied without being erased by finger friction, making it promising for use as synthetic paper. Moreover, the film also has the advantage that this effect appears almost independently of the thickness of the film. The present invention will be explained in more detail by giving examples and comparative examples below. The methods for measuring various physical properties are as follows. Melt index JIS K6758 Melt flow index JIS K6760 (5.1) Density JIS K6460 (5.2.4) Haze ASTM D-1003 Gloss ASTM D-523T (60°) Example 1 Melt flow index 0.7g/10min 60 parts by weight of a propylene homopolymer and 40 parts by weight of a copolymer of ethylene and butene-1 produced by a medium-low pressure method with a melt index of 0.005 g/10 min and a density of 0.935 g/cc.
Mixing was performed using a 50 mm single screw extruder. Melt flow index of the obtained composition (230℃, 2.16Kg)
was 0.07g/10min. With this composition
A 50mm air-cooled inflation film molding machine with a die temperature of 240℃ and a blow-up ratio of 30μ.
A thick film was formed. The resulting film has a haze level of 95.4% and a gloss level of 95.4%.
4.9% and impact strength of 152 kg cm/mm, it was opaque, non-glossy, and of good quality with excellent strength. Characters could be clearly written on this film with a pencil or ballpoint pen, and they would not be erased even when rubbed with a finger. The surface of the film was also examined using a scanning electron microscope (2000
When observed under magnification (magnification), numerous protrusions ranging from 0.5 μm to several μm in size were observed. Further, when it was observed under an optical microscope (1000x magnification) while being heated at a temperature increase rate of 1° C./min, the protrusions melted first, indicating that the protrusions were mainly composed of polyethylene, which has a low melting point. Example 2 The same procedure as in Example 1 was carried out except that the film thickness was changed to 10μ, but the film showed a haze level of 93.2%, a gloss level of 5.1%, and an impact strength of 75 kg cm/mm. Although it was 1/3 of that of Example 1, the decrease in haze was slight, and the calligraphy properties were also similar to those of Example 1. Examples 3 to 7 The same procedure as in Example 1 was carried out using the polyethylene shown in Table 1 in the amount shown in Table 1 instead of the polyethylene in Example 1. As shown in Table 1, the various physical properties were excellent, and the calligraphy properties were also as good as those of Example 1. It was the same as 1.
【表】
比較例 １
メルトインデツクス0.06g／10min、密度
0.948g／c.c.、ブテン―１をコモノマーとした中低
圧法ポリエチレンを用いて実施例１と同様にして
30μ厚のフイルムを成形した。このフイルムは衝
撃強度は320Kg・cm／mmと優れていたが、曇り度
68.3％、光沢度19.2％であり、不透明さに欠け稍
光沢を有していた。フイルム表面を走査型電子顕
微鏡（2000倍）で観察したところ突起は認められ
ず、鉛筆やボールペンにより字を書くことは困難
であり指で摩擦すると直ちに消えてしまつた。
比較例 ２
実施例１と同じポリプロピレン50重量部とメル
トインデツクス1.1g／10min、密度0.958g／c.c.の
中低圧法ポリエチレン（ホモ）50重量部を実施例
１と同様に混合してフイルムを成形したが、バブ
ルが安定せず厚みむらが発生して均質なフイルム
が得られなかつた。このフイルムの30μ厚の部分
については曇り度68.3％、光沢度14.6％と不満足
なものであり、書画性も認められなかつた。
実施例 ８
メルトフローインデツクス1.3g／10min、エチ
レン含量4.3重量％のプロピレン―エチレン共重
合体60重量部と実施例１で用いた中低圧法ポリエ
チレン40重量部を実施例１と同様に混合してフイ
ルムを成形した。得られたフイルムは曇り度96.2
％、光沢度4.8％、衝撃強度140Kg・cm／mmと諸物
性に優れ、書画性も実施例１と同様であつた。[Table] Comparative example 1 Melt index 0.06g/10min, density
0.948g/cc, in the same manner as in Example 1 using medium-low pressure polyethylene with butene-1 as a comonomer.
A film with a thickness of 30μ was molded. This film had an excellent impact strength of 320 kg・cm/mm, but its cloudiness
It had a gloss level of 68.3% and a gloss level of 19.2%, and lacked opacity and had a slight gloss. When the surface of the film was observed under a scanning electron microscope (2000x magnification), no protrusions were observed, making it difficult to write on them with a pencil or ballpoint pen, and they immediately disappeared when rubbed with a finger. Comparative Example 2 50 parts by weight of the same polypropylene as in Example 1 and 50 parts by weight of medium-low pressure polyethylene (homo) having a melt index of 1.1 g/10 min and a density of 0.958 g/cc were mixed in the same manner as in Example 1 to form a film. However, the bubbles were not stabilized and uneven thickness occurred, making it impossible to obtain a homogeneous film. The 30 μm thick portion of this film had unsatisfactory haze of 68.3% and gloss of 14.6%, and no calligraphic quality was observed. Example 8 60 parts by weight of a propylene-ethylene copolymer with a melt flow index of 1.3 g/10 min and an ethylene content of 4.3% by weight and 40 parts by weight of the medium-low pressure polyethylene used in Example 1 were mixed in the same manner as in Example 1. A film was formed. The resulting film has a haze of 96.2
%, glossiness of 4.8%, and impact strength of 140 Kg·cm/mm.