JPH01216839A - Multilayer film of polyethylene base - Google Patents

Abstract

PURPOSE:To obtain the film excellent in the handling and in high-speed filling and packaging properties by a method in which the film is composed of the composition layer containing the copolymer of two kinds of specified ethylene-alpha- olefin in a prescribed rate or the copolymer layer made of ethylene-alpha-olefin with a specified density and copolymer layer of specified ethylene-alpha-olefin. CONSTITUTION:The multilayer film of polyethylene base is composed of a composition layer or a copolymer layer A and a copolymer layer B. The composition layer is composed of 60-95wt.% of copolymer made of ethylene with 0.891-0.925g/cm<3> of density and alpha-olefin with 4-20 of carbons, and 40-5wt.% of low crystalline copolymer made of ethylene with 0.860-0.890 of density and alpha-olefin with 3-12 of carbon atoms. The copolymer layer A is made of the ethylene with 0.890-0.910g/cm<3> of density and alpha-olefin with 3-20 of carbon atoms. The layer B is composed of ethylene with 0.95-0.96g/cm<3> of density and alpha-olefin with 2-20 of carbon atoms. This multilayer film is excellent in low temperature sealing or the stability of sealing and has suitable rigidity, lubricating properties and blocking resistance, and it is excellent in high-speed filling and packaging properties.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel polyethylene multilayer film. More specifically, the present invention is suitable for use as a sealant base material for various packaging films and multilayer films, and has excellent low-temperature sealing properties and seal stability, as well as good rigidity, slipperiness, and anti-blocking properties. The present invention relates to a polyethylene multilayer film that has the following characteristics and is particularly suitable for high-speed filling and packaging.

[Prior Art] Conventionally, polyethylene films used for packaging articles include, for example, high-pressure low-density polyethylene films, high-density polyethylene films, and linear low-density polyethylene films made of ethylene-α-olefin copolymers. These films are widely used in various fields.

Among these polyethylene films, ethylene-α
-Linear low-density polyethylene film made of olefin copolymer has low energy cost during production compared to conventional high-pressure low-density polyethylene, and has excellent impurity sealing properties. Because it has excellent hot tack properties and mechanical properties such as tear strength and impact strength, it has recently been in the spotlight as a sealant base material for various packaging and multilayer films.

However, in these applications, not only good handling properties are required during operations such as laminating, printing, and bag making, but also high speed during automatic filling and packaging is required. Films made solely of olefin copolymers cannot always fully satisfy these handling characteristics and suitability for high-speed filling and packaging;
It has been desired to develop a film with rigidity, lubricity, anti-blocking properties, etc.

Therefore, in order to meet such demands, various compositions and films have been proposed, but at present none of them has been able to fully satisfy the above-mentioned physical properties. For example, a resin composition in which a low crystalline ethylene copolymer having a density of 0.9059/ci+3 or less is blended with an ethylene-α-olefin copolymer (Japanese Patent Laid-Open No.
No. 34145, No. 60-55045, No. 60
-55045 Publication, Special Publication No. 62-10532)
and a resin composition containing an ethylene-vinyl acetate copolymer (Japanese Unexamined Patent Publication No. 109543/1983). However, all of these resin compositions have the drawback that they cannot fully satisfy all of the above physical properties. In addition, dense ethylene
A resin composition containing an α-olefin copolymer and a low-density ethylene-α-olefin copolymer has been disclosed (JP-A-57-59943, JP-A-60-365).
However, although heat-sealing properties and the like are improved in films made from this composition, there is a problem in that the rigidity, anti-blocking properties, and lubricity are rather reduced.

Furthermore, a multilayer film (Japanese Patent Application Laid-Open No. 60-8594
6) or through a high-pressure low-density polyethylene layer,
An ethylene-α-olefin copolymer layer with a density of 0.91 to 0.93 and an ethylene-α-olefin copolymer layer with a density of 0.92 to 0.94.
A multilayer film formed by laminating an olefin copolymer layer (
JP-A-58-160147) and the like are disclosed. However, although the former multilayer film has improved transparency, impact resistance, and tear strength, the sealing performance has not been improved, and the latter multilayer film has the drawback of poor low-temperature sealability.

[Problems to be Solved by the Invention] Under these circumstances, the present invention has excellent low-temperature sealing properties and sealing stability, and has good rigidity, lubricity, anti-blocking properties, etc. This was done with the aim of providing a polyethylene multilayer film that has excellent handling properties and suitability for high-speed filling and packaging.

[Means for Solving the Problems] As a result of extensive research to develop a polyethylene multilayer film with such excellent properties, the present inventors have discovered that two specific ethylene-α-olefins coexist. A multilayer film consisting of a composition layer containing a polymer in a predetermined ratio or an ethylene-α-olefin copolymer layer having a specific density, and a specific ethylene-α-olefin copolymer layer, and these layers It has been discovered that a multilayer film in which a specific ethylene polymer layer is provided in between can meet the above objective, and based on this knowledge, the present invention has been completed.

That is, the present invention provides (A) (B) a density of 0.891 to
60 to 95% by weight of a copolymer of 0.9251 F/cm' of ethylene and an α-olefin having 4 to 20 carbon atoms; and (b)
Low crystallinity copolymer 4 of ethylene and α-olefin having 3 to 12 carbon atoms with a density of 0.860 to 0.890 #/am'
A composition layer consisting of 0 to 5% by weight, or a density of 0.890
~0.910 copolymer layer of ethylene and α-olefin having 4 to 20 carbon atoms, and (B) density 0.915 to 0°9
60 y/cm of ethylene and α- having 3 to 20 carbon atoms
A polyethylene multilayer film consisting of a copolymer layer with olefin, and the (A) layer and (B) layer, (C)
High-pressure polyethylene and/or ethylene with density 0.900=0.94 Of/cz' and α having 3 to 20 carbon atoms
- Provides a polyethylene multilayer film laminated with layers made of a copolymer with an olefin interposed therebetween.

The present invention will be explained in detail below.

In the multilayer film of the present invention, (A) layer (
b) Ethylene having a density in the range of 0.891 to 0.9259/cm', preferably 0.895 to 0.920 g/cm31 and carbon atoms having 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms.
a copolymer with a species or two or more α-olefins, (b) ethylene having a density in the range of 0.860 to 0.890 g/cm3, preferably 0.870 to 0.890ti/cm3, and carbon number A mixture of 3 to 12, preferably 4 to 10, one or more α-olefins and a low crystallinity copolymer is used. If the density of the copolymer of component (a) is less than 0.891 t/013, the rigidity of the film will be low and blocking will easily occur, and the heat sealing strength may decrease;
．． If it exceeds 925 g/cm', low-temperature sealing properties and impact strength tend to decrease. It is desirable that the melt index of the copolymer of component (a) is in the range of 1 to 50 g/10 minutes, preferably 2 to 30 g/10 minutes.If the melt index is less than 11/10 minutes, it will melt. The viscosity is high and the moldability is poor, and if it exceeds 50 g/10 minutes, the melt viscosity is too low, resulting in poor moldability, and the mechanical strength of the film tends to decrease, which is not preferable.

Examples of the α-olefin used as a raw material monomer for the ethylene-α-olefin copolymer of component (A) include butene-1, pentene-1, hexene-1,
Heptene-1, Octene-1, Nonene-1, Decene-1
, dodecene-1, tetradecene-1, octadecene-1
,4-methylpentene-1,4-methyl-hexene-1
, 4,4-dimethylpentene-1, or a mixture thereof, among which α-olefins having 4 to 12 carbon atoms are preferred.

On the other hand, the density of the low crystalline copolymer of component (b) is 0.
If it is less than 860 g/C1", the rigidity and heat sealing strength of the film will be low and blocking will easily occur, and if it exceeds 0.890 y/cm3, the effect of improving low temperature sealing performance may not be fully exhibited. (
The low crystallinity copolymer of component (b) preferably has a degree of crystallinity of 40% or less, from the viewpoint of improving the low-temperature sealing property.
Further, those having a melt index in the range of 0.5 to 50 g/10 min, preferably 1 to 20 y/cm3 are suitable. If the melt index is less than 0.5 y/10 minutes, the effect of improving low-temperature sealing properties will not be fully exhibited, and if it exceeds 509/10 minutes, the blocking properties of the film will deteriorate and the mechanical strength will decrease. It tends to be undesirable.

In the copolymer of component (b), examples of α-olefins used as raw material monomers include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene. α-olefins such as -1, dodecene-1,4-methylpentene-1,4-methylhexene-1,4,4-dimethylpentene-1, or mixtures thereof, among which -10 α-olefins are preferred.

In the present invention, the components (a) and (b) are
It is necessary to blend them in proportions of 60 to 95% by weight and 5% by weight of 4O-S-', preferably 64 to 92% by weight and 36 to 8% by weight, respectively. If the amount of the component (b) is less than 5% by weight, the effect of improving low-temperature sealing properties will not be sufficiently exhibited, and if it exceeds 40% by weight, the resulting film will tend to be prone to blocking and its mechanical strength will decrease. There is.

In the multilayer film of the present invention, the layer (A) contains ethylene having a density in the range of 0.890 to 0.910 g/cl, preferably 0.895 to 0.910 g/cm3, and carbon atoms having 4 to 20 carbon atoms. , preferably a copolymer with 4 to 12 α-olefins, may also be used. If the density is less than 0.890 g/cm', the rigidity of the film is low and blocking is likely to occur, and the heat sealing strength may decrease.
? /CI3, there is a tendency for low-temperature sealing properties and impact strength to decrease.

The melt index of this copolymer is 1-50g710
If the melt index is less than 11F/10 minutes, the melt viscosity is high and the moldability is poor;
If the heating time exceeds 10 minutes, the melt viscosity is too low, resulting in poor moldability, and the mechanical strength of the film tends to decrease, which is not preferable.

Examples of the α-olefin used as a raw material monomer for this copolymer include those listed in the explanation of the ethylene-α-olefin copolymer of component (A) above. 4 to 12 α-olefins are preferred.

In the multilayer film of the present invention, the (B) layer has a density of 0.915 to 0.960 g/cm3, preferably 0.960 g/cm3.
A copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms is used in the range of 92 C) to 0.955 g/cm'. This density is 0.915
If it is less than 11/cm', the rigidity of the film decreases and blocking tends to occur;
If it exceeds g/cm3, the impact resistance and transparency of the film tend to decrease.

The melt index of this copolymer is 0.5-301F
/10 minutes, preferably in the range of 1 to 20 g/10 minutes, and the melt index is 0.511/1
If it is less than 0 minutes, the melt viscosity will be high and the moldability will be poor;
If it exceeds y/10 minutes, the melt viscosity is too low, making it difficult to mold, and the mechanical strength also tends to decrease, which is not preferable.

In this copolymer, the α-olefin used as a raw material monomer includes, for example, propylene, butene-1, pentene-1, hexene-1, heptene-1,
Octene-1, Nonene-1, Decene-1, Dodecene-1
, tetradecene-1, octadecene-1,4-methylpentene-1,4-methylhexene-1,4,4-dimethylpentene-1, or mixtures thereof. α-olefins having numbers 3 to 12 are preferred.

The multilayer film of the present invention may be a two-layer film consisting of the above-mentioned (A) layer and (B) layer, or a (C) layer may be provided between the (A) layer and (B) layer. , the density is 0.900
~0.940fl/CM" preferably 0.910~0.
High-pressure polyethylene and/or ethylene in the range of 935y/cm3 and carbon number 3 to 20, preferably 4
It may have a layer made of a copolymer with ~10 α-olefins.

The density of the ethylene polymer used for this (C) layer is 0.
．． If it is less than 900y/cm3, the rigidity will be low and the film may become soft.
If it exceeds 0 p/cm3, the mechanical strength of the film, especially the impact strength, tends to decrease.

The melt index of this ethylene copolymer is 0.5
It is desirable that the melt index is in the range of ~50g/10min, preferably 1~20g/710min, and the melt index is 0.
If it is less than 5y/10 minutes, it is undesirable because it has a high melt viscosity and poor formability, and if it exceeds 50g/10 minutes, it has too low a melt viscosity and not only has poor formability but also reduces the mechanical strength of the film. So I don't like it.

For this layer (C), high-pressure polyethylene having the above physical properties may be used, a copolymer of ethylene and α-olefin may be used, or a mixture of both may be used. α- used as a raw material monomer for the copolymer
Examples of olefins include propylene, butene-1,
Pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, dodecene-1, tetradecene-1, octadecene-1,4-methylpentene-
Examples include α-olefins such as 1,4-methylhexene-1,4,4-dimethylpentene-1, and mixtures thereof, and among these, α-olefins having 4 to 10 carbon atoms are preferred.

The copolymer of ethylene and α-olefin used in layer (A) in the multilayer film of the present invention is produced by a so-called medium-low pressure method using a transition metal catalyst.
- It can be produced by polymerizing olefin at a ratio that gives the desired density. At this time, the type and amount of the chain transfer agent are appropriately selected in order to obtain a product having a desired melt index. As the polymerization method, various methods such as slurry polymerization, gas phase polymerization, and solution polymerization can be used. In addition, (B) layer and (C
) The copolymer of ethylene and α-olefin used in the layer may be produced by a low-pressure method using a transition metal catalyst as described above, or may be produced by a high-pressure method, and further, (C) The high-pressure polyethylene used in Jl can be produced by radical polymerizing ethylene under high pressure.

Regarding the thickness ratio of each layer in the multilayer film of the present invention, in a two-layer film, the thickness ratio between layer (A) and layer (B) is usually 2:98 to 50:50, preferably 3:97. or 40:60, and 3
In layered films, the thickness ratio of (A>layer, (C) layer, and (B) layer) is usually 2:96:2 to 40 when the (A) layer and (B) layer have the same layer thickness. :20:40, preferably 3:94:3 to 30:40:3
Selected within the range of 0. Furthermore, the thickness of the entire multilayer film is usually 10 to 300 μm, preferably 20 to 200 μm.
m, more preferably selected in the range of 30 to 150 μm.

There are no particular limitations on the method for producing the multilayer film of the present invention, and methods commonly used for producing multilayer films,
For example, a blown film molding method, a T-die film molding method, etc. can be used. At this time, the resin temperature is usually selected in the range of 200 to 300°C, and for cooling the formed film, a chill roll method is usually used in the T-die molding method, and an air cooling method is used in the inflation molding method. . In the chill roll method, it is desirable that the layer (B) is in contact with the roll surface, and the cooling temperature is usually 20 to 80°C, preferably 30 to 80°C.
Selected within the range of 70°C. If this cooling temperature is lower than 20°C, the rigidity of the film may decrease or the handling properties may deteriorate, and if it is higher than 80°C, film formability and the appearance of the film tend to deteriorate, which is not preferable. .

In the multilayer film of the present invention, antioxidants, light stabilizers, heat stabilizers, anti-blocking agents, lubricants, catalyst neutralizers (chlorine absorbers), and preventive agents may be added to any or all of the layers as desired. Various additives commonly used in polyethylene films, such as fogging agents and antistatic agents, can be added.

As the above-mentioned antioxidant, phenol-based and phosphorus-based antioxidants can be preferably mentioned, and it is particularly preferable to use these in combination.As the phenolic antioxidant, for example, 2,6-di-t-butyl-4-methyl Phenol, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate (manufactured by Ciba Geigy, Irgan
ox 3114), 2+2'-methylenebis(4-
ethyl-5-t-butylphenol), n-octadecyl-3-(3°,5°-di-t-butyl-4′-hydroxyphenyl)propionate (manufactured by Ciba Geigy, I
rganox1076), 4.4°-thiobis(3
-methyl-6-t-butylphenol), tetrakis[
Methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate comethane (manufactured by Ciba Geigy, Irganox 1010), 4.
4°-Butylidenebis(3-methyl-6-t-butylphenol), 2.2°-methylenebis(4-methyl-6-t-butylphenol), N,N'-hexamethylenebis(3,5-dimethylphenol) -t-butyl-4-hydroxyhydrocinnamide) (manufactured by Ciba Geigy, Irgan
ox1098), triethylene glycol-bis[3-
(3°-t-butyl-5°-methyl-4-hydroxyphenyl)probionate], a mixture of calcium bis(3,5-di-t-butyl-4-hydroxybenzylphosphonate) and PE wax ( weight ratio 1:1) (manufactured by Ciba Geigy, Irganox 1425WL). Examples of ricin-based antioxidants include distearylpentaerythritol diphosphite (manufactured by Adeka Argus, MARK PEP-8), tetrakis(2,4-di-t-butylphenyl)-4,4°
- Biphenylene diphosphite (manufactured by Sandoz, 5and
ostabP-EPQ) ,) lisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl)
Phosphite (manufactured by Adeka Argus, MARK 2
112) Di(2,4-di-t-butylphenyl)-pentaerythritol diphosphite (manufactured by Adeka Argus, MARK PEP-24G), bis-(2,6-di-t-butyl-4-methylphenyl) ) Pentaerythritol diphosphite (manufactured by Adeka Argus, MARK
PEP-36) and the like. As the light stabilizer, for example, salicylates, benzophenones, triazoles, oxalic acid anilides, hindered amines, etc. are used. Examples of the anti-blocking agent include natural silica, synthetic silica, zeolite, amorphous zeolite, diatomaceous earth, and among these, diatomaceous earth is particularly preferably used.

Furthermore, as a lubricant, for example, stearic acid amide,
Examples of the catalyst neutralizing agent include palmitic acid amide, oleic acid amide, erucic acid amide, etc., and calcium stearate, zinc stearate, magnesium stearate, hydrotalcite, and the like.

When the multilayer film of the present invention is used, for example, as a laminate sealant or when printing is performed on the surface of the film, it is advantageous to subject the surface of the layer (B) to a surface treatment such as a corona discharge treatment. The corona discharge treatment is
Usually 20 w/z2/min or more, preferably 2
By such surface treatment, which is preferably carried out under conditions of 5 w/I”/sin or more, the wettability index of the surface of the layer (B) is 30 dyne/cm or more, preferably 3
5 dyne/ex or more, more preferably 38 dyne/ex
It is desirable that it be at least cm.

Next, the polyethylene multilayer film of the present invention will be described with reference to the accompanying drawings. FIGS. 1 and 2 are cross-sectional views of different examples of the multilayer film of the present invention, respectively.
FIG. 1 shows a two-layer structure in which (A) layer 1 and (B) layer 2 are stacked, and FIG. 3 shows a two-layer structure in which (A) layer 1 and (B) layer 2 are laminated.
C) Shows a three-layer structure laminated with layer 3 in between. In addition, when using the film, (A) layer 1 is used as a sealing surface.

[Effects of the Invention] The polyethylene multilayer film of the present invention has excellent low-temperature sealing properties and sealing stability, as well as good rigidity, slipperiness, and anti-blocking properties, and is suitable for handling and high-speed filling and packaging. It is suitable for use as, for example, various packaging films and sealant base materials for multilayer films.

[Example''] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

In addition, each physical property of the film was determined as follows.

(1) Sealing temperature (Idemitsu method) Two multilayer films (A) layer surfaces facing each other, 21g/
The sealing was carried out under the conditions of ``cyt'' and 1 sec, and the sealing strength was 300 II/25 mm. (1) The temperature was measured using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd.

(2) Film impact Measured according to the Idemitsu method.

(3) Dirt Impact Compliant with ASTM D 1709A method, drop height 66
cm, measured at -20°C.

(4) Elmendorf tear strength, tensile modulus JIS
Determined in accordance with Law Z 1702.

(5) Film running properties (feeding properties, meandering properties, blocking properties) Evaluate using the following three-stage criteria.

◎: Excellent, O: Good, Δ: Fair In addition, as raw material resins, those shown in Table 1 were used.

(Leaving space below) (Examples 1 to 15, Comparative Examples 1 to 7゛) The resin layers shown in Table 2 were used as layers (A), (B), and (C), respectively, using extruders of 50xxφ, 60xxφ, and 50ivφ. Melt and knead to form a multi-manifold multi-layer T-die (
A film with a total thickness of 40 μm was obtained by extruding at a die temperature of 250 cm and then cooling the (B) layer in contact with a chill roll (40 °C).
Next, the (B) 11 surface of this film was heated with 28 w
A multilayer film was obtained by corona discharge treatment under the conditions of /I''/win.The evaluation results of this film are shown in Table 2.The thickness ratio of each layer of the multilayer film (A)/(C)
/(B) is 115/1.

(Margin below)

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of different examples of the polyethylene multilayer film of the present invention, in which reference numeral 1 is the A layer, 2 is the B layer, and 3 is the 0 layer. Figure 1 Figure 2

Claims (2)

[Claims] (1) (A) (A) Density 0.891 to 0.925 g/c
Copolymer of m^3 ethylene and α-olefin having 4 to 20 carbon atoms 60 to 95% by weight and (b) density 0.860 to
A composition layer consisting of 0.890 g/cm^3 of ethylene and 40 to 5% by weight of a low crystalline copolymer of α-olefin having 3 to 12 carbon atoms, or a density of 0.890 to 0.910 g
/cm^3 of ethylene and an α-olefin having 4 to 20 carbon atoms, and (B) a density of 0.915 to 0.96.
A polyethylene multilayer film comprising a copolymer layer of 0 g/cm^3 of ethylene and an α-olefin having 3 to 20 carbon atoms. (2) (A) (A) Density 0.891 to 0.925 g/c
Copolymer of m^3 ethylene and α-olefin having 4 to 20 carbon atoms 60 to 95% by weight and (b) density 0.860 to
A composition layer consisting of 0.890 g/cm^3 of ethylene and 40 to 5% by weight of a low crystalline copolymer of α-olefin having 3 to 12 carbon atoms, or a density of 0.890 to 0.910 g
/cm^3 of ethylene and an α-olefin having 4 to 20 carbon atoms, and (B) a density of 0.915 to 0.96.
A copolymer layer of 0 g/cm^3 of ethylene and an α-olefin having 3 to 20 carbon atoms, (C) having a density of 0.900 to 0
．． A polyethylene multilayer film formed by laminating layers of high-pressure polyethylene of 940 g/cm^3 and/or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms.