FI85671C

Multi-layer film

Abstract

@ The present invention relates to a multi-layer film comprising at least three layers of two outer layers and an intermediate layer sandwiched therebetween wherein the intermediate layer is formed of a resin composition of a high density polyethylene and an ethylene a-olefin copolymer, and the outer layers are formed of an ethylene a-olefin copolymer and at least one of the outer layers is formed of a resin composition of an ethylene a-olefin copolymer and a low density polyethylene. The object of the present invention is to provide a multi-layer film having a high mechanical strength and superior in properties such as heat sealability, antiblocking, and automatic packaging property.

FI85671C, drawing sheet 1 — Sheet 1 of 66

Term

Term ended

Expired 7 November 2004, 21.9 years ago.

5 claims: 1 independent, 4 dependent

1
Claims 030 / I Patenttivaatimukset 030 / I patentkrav 1. A multilayer film comprising at least three layers, the three layers comprising two outer layers and an intermediate layer interposed between the two outer layers of 90 to 1. Flerskiktsfilm, som omfattar ätminstone tre skikt, vilka skikt bestär av tvä yttre skikt och ett mellanskikt som placerats mellan de tvä yttre skikten är av hartskonsistens, som innehäller 90 - 10 vikt-% polyetylen med hög densitet och 10 1. Monikerroskalvo käsittäen ainakin kolme kerrosta, näiden kolmen kerroksen sisältäessä kaksi ulkokerrosta ja kahden ulkokerroksen väliin sijoitetun välikerroksen, joka on 90 - - 90 vikt-% etylen-fK-olef inkopolymer, vardera av de tvä yttre skikten innehäller etylen-'K-olef inkopolymer, k ä n n e tecknad av att ätminstone det ena av de tvä yttre skikten är av hartskonsistens, som innehäller 98 - 50 vikt-% etylen-°(-olefinkopolymer och 2-50 vikt-% polyetylen med läg densitet, tillverkad enligt högtryckspolymeriseringsmetoden. 10 a resin composition comprising 10% to 90% by weight of high density polyethylene and 10 to 90% by weight of an ethylene-N-olefin copolymer, each of the two outer layers containing an ethylene-α-olefin copolymer, characterized in that at least one of the two outer layers is a resin composition containing 98 to 50% by weight ethylene-olefin copolymer and 25% by weight of low density polyethylene produced by a high pressure polymerization process. 10 paino-% suuritiheyksistä polyetyleeniä ja 10 - 90 paino-% etyleeni-«<-olefiinikopolymeeriä sisältävä hartsikoostumus, kummankin kahdesta ulkokerroksesta sisältäessä etyleeni-ec-olefiinikopolymeeriä, tunnettu siitä, että ainakin toinen kahdesta ulkokerroksesta on hartsikoostumus, joka sisältää 98 - 50 paino-% etyleeni-«<-olef iinikopolymeeriä ja 2 50 paino-% pienitiheyksistä polyetyleeniä, joka on valmistettu suurpainepolymerointimenetelmällä.

369 paragraphs in 10 sections, as filed

MULTI-LAYER FILM

The present invention relates to a multilayer film, and in particular to a multilayer film having a high mechanical strength and a thickness which can be reduced and further having a very good heat sealability and non-adhesion.

High or low density polyethylene films have previously been used as hard wear resistant packaging film materials for packaging fertilizers, rice, wheat, etc. However, the high-density polyethylene film produced by the high-pressure polymerization method has poor mechanical strength and therefore it is inevitably necessary to increase their thickness. Similarly, low density polyethylene films have the disadvantage that the tear strength is not good enough, the sealability and puncture resistance are not satisfactory, and also the appearance is not good.

In order to overcome the above-mentioned problems of polyethylene films and also to meet the requirement that the film thickness should be reduced in order to save raw materials, various single- or multilayer films have been developed in recent years. Typical examples are (1) films produced from moldable compositions comprising high density polyethylene and rubbers, (2) films comprising a layer of low density polyethylene and a layer of high density polyethylene as a laminated bilayer structure, (3) films comprising: consisting of a resin composition of high density polyethylene and ethylene ob-olefin copolymer and a layer formed of low density polyethylene laminated as a two-layer structure, and (4) three-layer laminate films comprising a layer of polyethylene and two outer layers of low density polyethylene.

However, these films still have various disadvantages and are not sufficiently satisfactory in practice. For example, the above-mentioned films (1) do not have satisfactory mechanical strength or appearance, although the sealability has improved. The films (2) do not have any particular problems in terms of mechanical strength and appearance, but they are not always satisfactory in terms of properties such as sealability, puncture resistance and practical drop strength. The films (5) are not sufficiently rigid and are also not suitable for automatic packaging. Furthermore, sacks with a low-density polyethylene layer as the inner layer are easily prone to adhesion and thus have poorer opening properties. The films (4) have very good optical properties, but their disadvantage is that the puncture resistance and sealability when packing heavy metals are not sufficiently satisfactory and adhesion occurs easily.

The object of the present invention is to overcome the known problems described above, and the present invention relates to a multilayer film having good mechanical strength and further very good properties such as heat sealability, non-stickiness and suitability for automatic packaging.

The present invention relates to a multilayer film comprising at least three layers consisting of two outer layers and an intermediate layer formed therein consisting of a resin composition of a high density polyethylene and an ethylene-olefin copolymer and two outer layers of at least two ethylene and the outer layer being formed of a resin composition, consisting of an ethylene-e-olefin copolymer and a low density polyethylene produced by a high pressure polymerization process.

The intermediate layer of the multilayer film of the present invention is formed of a resin composition formed of a high density polyethylene and an ethylene-e <-olefin copolymer. As used herein, the density of high density polyethylene is in the range of 0.945. · .0.970 g / cm 3, preferably 0.948 ... 0.965 g / cm 3 and a melt index (MI) in the range 0.01 ... 20 g / 10 min, preferably 0.02 ... 5 g / 10 min, most preferably 0.02 ... 2 g / 10 min. The ethylene-o (-olefin copolymer) is a linear low density polyethylene produced by a low or moderate pressure polymerization process with a density in the range of 0.900 to 0.940 g / cm3, preferably in the range of Ο.9 ...5 to Ο.93Ο g / cm3 and a melt index ( MI) in the range 0.1 to 20 g / 10 min, preferably 0.2 to 10 g / 10 min. The amount of copolymer • 4-olefin is usually 1 to 20% by weight. * (- The olefins which can be used are those containing 3 ·· «20 carbon atoms. Representative examples are propylene, 1-butene, 1-pentene-1-hexene, 4-methyl-1-pentene, 1-octene, 1-nonene and 1-decene.

The resin composition for the interlayer contains 90 to 10% by weight of high density polyethylene and 10 to 90% by weight of an ethylene-olefin copolymer, and preferably

80 .. .20% by weight of high density polyethylene and

20 .. .80% by weight of ethylene-p <-olefin copolymer. The mixing ratio of high density polyethylene is ethylene-o *. -olefin copolymer may be suitably administered within the range defined above, taking into account, for example, the intended use of the multilayer film. If the amount of the ethylene-β-olefin copolymer is less than 10% by weight, then the puncture resistance and the tear strength are not high enough. On the other hand, if its amount exceeds 90% by weight, the rigidity and suitability for automatic packaging are undesirably reduced. If the ethylene-α-olefin copolymer is added in an amount of at least 50% by weight, a multilayer film having a higher impact strength at a low temperature can be obtained.

The resin composition for the interlayer is based on the low-pressure polyethylene and ethylene-oC-olefin copolymer described above. If necessary, the composition may further contain a low degree of crystallinity o <-olefin copolymer. The addition of such low crystallinity »ς-olefin copolymers makes it possible to greatly increase the impact strength, especially at low temperature. The low crystallinity oC olefin as used herein has a density between 0.85 ... 0.9 g / cm 3, preferably 0.86 ... 0.89 g / cm 3, a melt index (MI) between 0.01 ... 50 g / 10 min, preferably 0.05 ·· -20 g / 10 min and a degree of crystallinity between 0 and 30%, preferably Ο ... 25%. If the density, melt index and degree of crystallinity do not fall within the ranges defined above, then the workability, formability, physical properties, etc. are undesirably inferior.

The low-crystallinity o <-olefin copolymer included herein is a copolymer composed mainly of ethylene or propylene as a monomeric component copolymerized with other olefins. The ε-olefins copolymerizable with ethylene or propylene are not particularly limited, including ethylene propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene and the like. In addition to ethylene or propylene and the above-mentioned o <-olefins, the copolymer may comprise other types of monomeric components derived by copolymerization with copolymerizable monomers, e.g. non-conjugated diene monomers, e.g., 1,4-hexadiene, dicyclopentadiene, 5-methyl-2-norbornane and the like, and conjugated diene monomers, e.g., butadiene, isoprene and the like. Particularly preferred in the present invention are copolymers composed of ethylene or propylene and other Λ-olefins and copolymers thereof with copolymerizable diene monomers having a * <- olefin content of at least 80 moles of ethylene and propylene other than # and o <-olefins. ethylene and propylene, the amount is in the range of 4 to 5Ο molar # or, preferably 5 ·· <40 molar #.

Examples of suitable low crystallinity α-olefin copolymers include ethylene-propylene copolymer, propylene-ethylene copolymer, ethylene-1-butene copolymer, ethylene-propylene-1,4-hexadiene copolymer, ethylene-ethylene-2-ethylene-5-propylene-5-hexylene copolymer. Of course, these low crystallinity cK-olefin copolymers can be used either alone or in combination with two or more of them having different density, melt index and crystallinity values than those prepared with different o <-olefins.

The amount of the low crystallinity χ-olefin copolymer added is 1 to 30 parts by weight, preferably 2 to 20 parts by weight per 100 parts by weight of the above-described resin composition consisting of high density polyethylene and ethylene-olefin copolymer. If a resin composition mixed with a low crystallinity X-olefin copolymer has been used to make the intermediate layer, a multilayer film can be obtained which has further increased mechanical strength and further has very good puncture resistance at low temperature.

In the resin composition, the low-density polyethylene, ethylene-vinyl acetate copolymer and the like produced by the mouth-pressure polymerization process for the interlayer of the multilayer film of the present invention can be mixed with or in combination with the low-crystallinity ® <-olefin copolymer described above. The low density polyethylene produced by this high pressure polymerization process suitably has a density in the range of 0.910 to 0.940 g / cm 3, preferably 0.915 ·· .0.930 g / cm 3 and a melt index (MI) in the range of 0.05 ·· .20 g / 10 min, preferably 0.1 to 10 g / 10 min.

In the multilayer film of the present invention comprising two outer layers and an intermediate layer therebetween, the two outer layers are formed of an ethylene-X-olefin copolymer and at least one of the outer layers is made of a resin composition consisting of an ethylene-oC-olefin copolymer and a high pressure copolymer . The ethylene-X-olefin copolymers used in the two outer layers may be the same or different. These copolymers have a density and a melt index in the same range as defined for the ethylene-olefin copolymer forming the interlayer, and are prepared using an olefin having 3 to 20 carbon atoms. The ethylene-cK olefin in the outer layer may be the same as or different from the copolymer in the intermediate layer.

The low density polyethylene produced by high pressure polymerization using at least one of the two outer layers suitably has a density in the range 0.910 to 0.940 g / cm3, preferably 0.915 ·· »0.930 g / cm3 and a melt index (MI) in the range 0.05 ··» 20.0 g / 10 min, preferably 0.1 ... 10 g / cm3. The resin composition for the second layer of the at least two outer layers comprises 99 ·· »30% by weight of ethylene-C-olefin copolymer and 1 ... 70% by weight of low density polyethylene produced by a high pressure polymerization process, preferably 98 ··» 50% by weight of the above and

2 .. .50 weight percent of the latter, and even more preferably

96 .. .60% by weight of the former and 4 ··· 4Ο% by weight of the latter. In the case where the multilayer film of the present invention is forged by the expansion balance method, it is preferable that the inner or inner layer of the multilayer is made of a resin composition containing low-density polyethylene produced by a high-pressure polymerization process, or both outer layers are made of a resin composition. so the blended amount of low density polyethylene produced by the high pressure polymerization process should be higher in the inner layer than in the outer layer.

The multilayer film of the present invention comprises at least three layers, two outer layers and an intermediate layer. If necessary, the multilayer film may further comprise one or more layers. For example, a layer made of low density polyethylene, high density polyethylene, ethylene-based copolymer (e.g., ethylene-unsaturated ester - such as ethylene vinyl acetate copolymer and ethylene-ethyl acrylate copolymer) or the like between the outer layer and other such as and may be placed at a suitable location.

In the case that the multilayer film according to the present invention is composed of the above three layers, i. of the intermediate layer and the two outer layers, the thicknesses of the layers are usually selected so that the thickness of the two outer layers is 2 to 60%, preferably 5 to 50% and even more preferably 10 to 50% of the total thickness of the three layers and the intermediate layer is 96%. .10%, preferably 90-15% and even more preferably 80-20% of the total thickness. When the multilayer film is used as a packaging bag for heavy goods, it is suitable that the thickness of the intermediate layer is 60 to 25% of the total thickness. As the thickness of the outer layer increases, the thickness of the intermediate layer decreases correspondingly, and the mechanical strength of the resulting multilayer film decreases. On the other hand, if the thickness of the outer layer is too small, the seam strength is undesirably reduced. The thickness of the multilayer film is not critical, it is usually about 10 to 300 microns, preferably about 20 to 25 microns, and preferably about 20 to 200 microns.

The multilayer film of the present invention can be produced by various methods such as expansion and T-extrusion. It is desirable to produce the multilayer film by the procedure described below, especially considering its application as a packaging bag.

The resin materials for the layers of the target multilayer film are each mixed by melt blending, for example, and are coextruded using an die of the in-die adhesion type and molded by an expansion method to produce a multilayer film. When producing a multilayer film having a thickness of 100 μ or more, the expansion molding is performed at a blow ratio of

1.1 ... 5-5, preferably 1.1 ... · 3 · 0 · If the blow ratio is more than 3 · 5, only a multilayer film can be obtained in which corrugation has developed for the heat-sealing areas; i. the appearance has deteriorated. Further, sacks made of such a multilayer film are not suitable for transporting empty because they are thicker on the heat-sealed side; i.e., due to the waviness, they become bulky.

The multilayer film of the present invention has various advantages over conventional films. For example, a multilayer film has a very high mechanical strength (such as tensile strength and impact strength, especially tear strength) and therefore its thickness can be reduced compared to conventional films. This leads to a reduction in the production cost of the multilayer film and further contributes to the saving of raw materials. The multilayer film has good heat sealability; the seam strength is high and the seam shrinkage is small. The multilayer film has good contamination sealing properties and thus is useful as a bag for packaging, for example, powder-containing material. The multilayer film has good non-stick properties and thus has excellent opening properties when used as a sack. Furthermore, the multilayer film is very stackable because of its suitable adhesion properties on its outer surface. Because the multilayer film has better rigidity than linear low density polyethylene films, it has good properties for automatic packaging.

Thus, the multilayer film of the present invention is very useful as a packaging film, especially for packaging heavy material.

The present invention is described in more detail in the following examples.

Examples 1-10 and Comparative Examples 1-4

The resin materials for the intermediate layer and the two outer layers (inner and outer layers) as shown in Table 1 were melted and mixed in three respective extruders (diameter 40 mm), extruded in an inner die adhesion type rotary die (die diameter: 200 mm; flange gap: 2 mm; flange clearance: 2 mm; ° C), and then blow molded at a given blow ratio to produce a multilayer well.

Examples 11-20

The multilayer films shown in Table 2 were prepared in the same manner as in Example 1 except that the blow ratio was set to 1.7 and the film thickness was adjusted to 140 gin.

The multilayer films obtained in Examples 1-20 and Comparative Examples 1-4 were tested for several of their physical properties as described below. The results are shown in Tables 1 and 2.

Tensile strength: measured according to JIS Z1702.

Tear strength: measured according to JIS Z1702.

Puncture resistance: measured according to JIS P8134

Low temperature: drop test

440 millimeters times a 660 millimeter (440 mm * 660 mm) sack containing 20 kg of chemical fertilizer was heat sealed at 200 ° C and then allowed to stand at -10 ° C for 10 hours. The sack was then dropped on a concrete floor from a height of 1.2 meters and examined for breakage. The evaluation was defined as follows:

5 ..... No breakage

2 ..... Breakage less than 50 percent

1 ..... Breakage more than 50 percent

Comparative Example 5

A simple film consisting of low density polyethylene made by high pressure polymer and 200 .mu.m thick was tested for its various physical properties as described above. The results are shown in Table 2.

Tables 1 and 2 (see next pages)

Outer Thickness Ratio Total no. Inner- Intermediate (inner layer / intermediate layer / thickness

CM

Fa a

Non-stick properties inside-outElmendorf Elasticity- Tensile-Elongation. arrow side ring strength modulus strength (nrosent- Puncture- inner- outer-

-r-> C

KA -4 KA <rc \ j KA <J ·

-4 KA KA rl xa <r ka

Π3 r! • H »H Φ

rH f — I CM mm T3

CM

Table 1 * 1 LDPE: High density polymerization low density polyethylene (density: 0.929 g / cm3; licking index (Ml): 0.5 g / 10 min), manufactured by Toyo Soda Co., Ltd. and sold under the trade name Petrothene 172.

* 2 LLDPE (A): Ethylene-4-methyl-1-pentene copolymer (density: 0.920 g / cm 3; lumbar index (M1): 2.2 g / 10 min), manufactured by Mitsui Sekyu Kagaku Kogyo Co., Ltd. and sold under the trade name Ultzex 2021 L.

* 5 LLDPE (B): Ethylene-1-octene copolymer (density: 0.924 g / cm 3; melt index (MI): 1.5 g / 10 min), manufactured by DSM Corp., and sold under the tradename Stamylex 1016.

* 4LLDPE (C): Ethylene-1-octene copolymer (density: 0.922 g / cm 3; melt index (MI): 1.9 g / 10 min), manufactured by DSM Corp., and sold under the tradename Stamylex 1026.

* 5 LLDPE (D): Ethylene-1-butene copolymer (density: 0.921 g / cm 3 M melt index (MI): 5 · 7 g / 10 min), manufactured by DSM Corp., and sold under the tradename Stamylex 1048.

♦ 6 HDPE: high density polyethylene (density: 0.959 g / cm3; melt index (MI): 0.05 g (10 min), manufactured by Idemitsu Sekyu Kagaku Co., Ltd. and sold under the tradename Idemitsu Polyethylene 640 UF.

* 7: Non-stick varies depending on, for example: 4 · .... commendable, 5 · ... Good, 2 .... satisfactory, 1 .... poor film thickness.

Table 2 * 1 LLDPE (B): Same as LLDPE in Table 1 (* 5) · * 2 LDPE: Same as LDPE in Table 1 (* 1) * 5 HDPE: Same as HDPE in Table 1 (* 6) * 4 LLDPE (D ): Same as LLDPE (D) in Table 1 (* 5) * 5 EPR: Ethylene-propylene diene copolymer (Mooney viscosity MLj<sub>+</sub>4 (100 ° C): 88), manufactured by Nippon Gosei Gomu Co., Ltd. and sold under the trade name EP57P · * 6 Lateral drop: The sack was dropped so that it was held in a lateral position.

Longitudinal drop: The sack was dropped so that it was held in a longitudinal position.

no Internal External Paksuussuh.de

m en <r tn un

m en

en en * 3 en en <r

CQ

swim

CU Q rJ r4

tn and CO rt oo

CM

IS

o jö (Λ> Φ

ΚΛ ΚΑΚΑΚΑΚΑΚΑΚΑΗΑΚΑΚΑ rl

KA Κ \ KA KA ιο, <AJ ΚΑ ΚΑ ΚΑ ΚΑ

I (Λ

CM

O CM

Table 3 shows Comparative Examples A and B prepared by us in which EVA has been used in place of LLDPE used in the inner layer in Examples 1 and 2 of this invention, and Comparative Examples C and D in which EVA has been used in place of LLDPE. used in the outer layer in Examples 5 and 6 of this invention.

Other points than above, i.e. the structure, thickness ratio, total thickness, blow ratio of the other layers are the same as in Tables 1 and 2.

I

U) • H <0

tn □ • -I—

Mi 3 <-1

Contents10

17 members in 8 offices

This recordMember, by publication datePriority claim

Priority claims3

Priority claims
Document	Office	Kind	Date
21355083	Japan	A	1983-11-14
58213550	–	–	–
JP19830213550	–	–	–

Members17

Family members, oldest first
Document	Office	Kind
DK538684D0	Denmark	D0	1984-11-13
DK538684A	Denmark	A	1985-05-15
FI844379L	Finland	L	1985-05-15
JPS60105541A	Japan	A	1985-06-11
EP0145945A2	European Patent Office (EPO)	A2	1985-06-26
US4574104A	United States of America	A	1986-03-04
IE842795L	Ireland	L	1986-05-14
EP0145945A3	European Patent Office (EPO)	A3	1986-07-23
EP0145945B1	European Patent Office (EPO)	B1	1989-07-19
AT44689T	Austria	T	1989-08-15
DE3479010D1	Germany	D1	1989-08-24
IE55914B1	Ireland	B1	1991-02-14
JPH0321343B2	Japan	B2	1991-03-22
FI85671B	Finland	B	1992-02-14
DK163972B	Denmark	B	1992-04-27
FI85671CThis record	Finland	C	1992-05-25
DK163972C	Denmark	C	1992-09-21

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