KR910008769B1 - Poly ehtyler multi-film - Google Patents

Abstract

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Description

Polyethylene Multilayer Film

1 and 2 are cross-sectional views of different examples of the polyethylene-based multilayer film of the present invention, respectively.

* Explanation of symbols for main parts of the drawings

1: A layer 2: B layer

3: C layer

The present invention relates to a novel polyethylene-based multilayer film.

More specifically, the present invention is excellent in low temperature sealability and seal stability, has good stiffness, activity, antiblocking property, and the like, and is particularly excellent in high speed packing and packaging properties, and is suitable for various packaging films and multilayers. It relates to a polyethylene-based multilayer film suitably used as a sealant for film.

Conventionally, as a polyethylene film used for the packaging of articles | goods, a high pressure low density polyethylene film, a high density polyethylene film, the linear low density polyethylene film which consists of ethylene-alpha-olefin copolymers, etc. are mentioned, for example, It is widely used in each field.

Among these polyethylene films, the linear low density polyethylene film composed of the ethylene-α-olefin copolymer has a low energy cost at the time of manufacturing the linear low density polyethylene of the substrate as compared with the conventional high pressure method low density polyethylene, As it is excellent in sealing property and hot-tack property and also excellent in mechanical properties such as tear strength and impact steel, it has recently been in the spotlight as various packaging materials and multilayer film sealant materials.

However, in these applications, for example, good handleability in operations such as lamination, printing, and bag making, as well as high speed in automatic filling and packaging, are required. However, the linear low density ethylene-α-olefin is required. In the film composed of the copolymer alone, the handling properties and the high-speed filling packaging properties cannot be sufficiently satisfied, and development of a film having more excellent low temperature sealability, seal stability, rigidity, activity, and anti-blocking property is desired. It became.

Therefore, in order to meet such a request, although various compositions and films have been proposed so far, it is a reality that none of them sufficiently satisfies the above properties.

For example, the resin composition which mix | blended the low crystalline ethylene copolymer of density 0.905g / cm <3> with the ethylene-alpha-olefin copolymer (JP-A-57-34145, 60-55045, copper Japanese Patent Application Laid-Open No. 62-10532), a resin composition containing an ethylene-vinyl acetate copolymer (Japanese Patent Application Laid-Open No. 59-109543), and the like are disclosed.

Moreover, the resin composition which mix | blended the high density ethylene-alpha-olefin copolymer and the low density ethylene-alpha-olefin copolymer is disclosed. (No. 57-59943, 60-36549).

However, in the film which consists of this composition, although the heat sealability etc. are improved, there exists a problem that rigidity, anti blocking property, and activity fall rather.

Moreover, ethylene-α- having a density of 0.91 to 0.93 g / cm 3 via a multilayer film formed by laminating the same kind of low density ethylene-α-olefin copolymer (see Japanese Patent Application Laid-Open No. 60-85946) or a high pressure method low density polyethylene layer. Disclosed are a multi-layer film (JP-A No. 58-160147) and the like obtained by laminating an olefin copolymer layer and an ethylene-α-olefin copolymer layer having a density of 0.92 to 0.94 g / cm 3.

However, in the above-mentioned multilayer film, transparency, impact resistance, and tear strength are improved, but the sealing property is not improved, and in the multilayer film mentioned later, there exists a fault that it is inferior to low temperature sealing property.

Under the circumstances, an object of the present invention is to provide a polyethylene-based multilayer film that is excellent in low temperature sealability and seal stability, has good rigidity, activity, antiblocking property, and the like, and is excellent in handleability and high-speed filling packaging ability. It is made up of.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to develop the polyethylene-type multilayer film which has such outstanding characteristic, the present inventors etc., the specific composition layer which contains two specific ethylene-alpha-olefin copolymer in predetermined ratio, or A specific copolymer layer having an ethylene unit and an α-olefin unit and having a specific density, a multilayer film composed of a specific ethylene-α-olefin copolymer layer, and a multilayer film in which a specific ethylene polymer layer is formed between these layers The present invention has been completed based on this finding.

That is, this invention is (a) 60-95 weight% of copolymers of ethylene and alpha-olefin of 4-20 carbon atoms of 0.891-0.925 g / cm <3>, and (b) 0.860-0.080g of density A composition having 40 to 5% by weight of a low crystalline copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms / cm 3, or an ethylene having 4 to 20 carbon atoms having a density of 0.890 to 0.910 g / cm 3. having a first layer (A) of the copolymer with an α-olefin and a second layer (B) of a copolymer of ethylene having an density of 0.915 to 0.960 g / cm 3 and an α-olefin having 4 to 20 carbon atoms It is to provide a polyethylene-based multilayer film, characterized in that.

In the multilayer film of the present invention, the first layer (A) is composed of a specific composition layer or a specific copolymer layer having a specific density.

As the specific composition, (a) ethylene having a density of 0.891 to 0.925 g / cm 3, preferably 0.895 to 0.920 g / cm 3, and one or two species of 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms. (B) ethylene having a density of 0.860 to 0.890 g / cm 3, preferably in the range of 0.870 to 0.890 g / cm 3, and having 3 to 12 carbon atoms, preferably 4 to 10 carbon atoms. Mixtures of low crystalline copolymers with species or two or more α-olefins are used.

When the density of the copolymer of the component (a) is less than 0.891 g / cm 3, the film has low rigidity and is easy to cause blocking, and there is a fear that the heat seal strength is lowered, while 0.925 g / When it exceeds 3 cm <3>, there exists a tendency for low temperature sealing resistance and impact strength to fall.

The melt index of the copolymer of the above (a) component is preferably in the range of 1 to 50 g / 10 minutes, preferably 2 to 30 g / 10 minutes.

If the melt index is less than 1 g / 10 min, the melt viscosity of the copolymer is high, so that the moldability of the first layer (A) is lowered, and if the melt index is more than 50 g / 10 min, the melt viscosity is too low and the first layer is In addition to reducing the moldability of (A), the mechanical strength of the film tends to decrease, which is not preferable.

As an alpha olefin used as a raw material monomer of the ethylene- alpha-olefin copolymer of the said (a) component, For example, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1 ? -Olefins such as decene-1, dodecene-1, tetradecene-1, octadecene-1, 1,4-methylpentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene-1 Or a mixture thereof is mentioned, Of these, C4-C12 alpha-olefin is preferable and octene-1 is especially preferable.

On the other hand, when the density of the low crystalline copolymer of the component (b) is less than 0.860 g / cm 3, the film has low rigidity and hit seal strength and is prone to blocking, and when it exceeds 0.890 g / cm 3, There is a concern that the improvement effect of the workability may not be sufficiently exhibited.

The low crystalline copolymer of the component (b) preferably has a crystallinity of 40% or less from the viewpoint of improving the low temperature sealing property, and has a melt index of 0.5 to 50 g / 10 minutes, preferably 1 to It is preferable to exist in the range of 20g / cm <3>.

When the melt index is less than 0.5 g / 10 min, the effect of improving low temperature sealing is not sufficiently exhibited. When the melt index exceeds 50 g / 10 min, the blocking property of the film is deteriorated, and the mechanical strength tends to be lowered. Not desirable

In the copolymer of component (b), examples of the α-olefins used as raw material monomers include propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, Α-olefins such as decene-1, dodecene-1,4-methylpentene-1,4-methylhexene-1, 4,4-dimethylpentene-1, or mixtures thereof, and the like. 10 alpha-olefin is preferable and octene-1 is especially preferable.

In the present invention, the above-mentioned (a) component and (b) component are respectively mix | blended in the ratio of 60-95 weight% and 40-5 weight%, Preferably it is 64-92 weight% and 36-8 weight%. desirable.

When the compounding quantity of the said (b) component is less than 5 weight%, the effect of improving low temperature sealing property is not fully exhibited, and when it exceeds 40 weight%, the film obtained will be easy to block and there exists a tendency for mechanical strength to fall.

The specific copolymer used as the first layer (A) has an ethylene having a density of 0.890 to 0.910 g / cm 3, preferably 0.895 to 0.910 g / cm 3, and 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms. Copolymer with? -Olefin.

The copolymer having a density of less than 0.890 g / cm 3 has a low rigidity of the film and is easy to cause blocking, and there is a fear that the heat seal strength is lowered. When the copolymer exceeds 0.910 g / cm 3, low-temperature sealability or impact resistance is achieved. The strength tends to be lowered.

The melt index of this copolymer is preferably in the range of 1 to 50 g / 10 minutes, preferably 2 to 30 g / 10 minutes.

If the melt index is less than 1 g / 10 min, the melt viscosity is high, and moldability is low. If the melt index is more than 50 g / 10 min, the melt index is too low, the moldability is worsened, and the mechanical strength of the film tends to be lowered. Not desirable

As alpha-olefin used as a monomer which is a raw material of this copolymer, what was mentioned by description of the ethylene-alpha-olefin copolymer of the said (a) component can be illustrated, but, among these, a C4-12 alpha-olefin is preferable. Especially, butene-1 is preferable.

In the multilayer film of the present invention, as the second layer (B), the density is 0.915 to 0.960 g / cm 3, preferably ethylene in the range of 0.920 to 0.955 g / cm 3, and 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms. Copolymers with olefins are used.

When this density is less than 0.915 g / cm <3>, rigidity of a film falls and blocking tends to occur, and when it exceeds 0.960 g / cm <3>, there exists a tendency for the impact resistance and transparency of a film to fall.

The melt index of this copolymer is preferably in the range of 0.5 to 30 g / 10 minutes, preferably 1 to 20 g / 10 minutes.

If the melt index is less than 0.5 g / 10 minutes, the melt viscosity is high and the moldability is inferior. If the melt index is more than 30 g / 10 minutes, the melt index is too low to be difficult to mold and the mechanical strength tends to be lowered, which is not preferable. .

In this copolymer, as an alpha olefin used as a raw material monomer, for example, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, Α-olefins such as dodecene-1, tetradecene-1, octadecene-1,4-methylpentene-1,4-methylhexene-1, 4,4-dimethylpentene-1, or mixtures thereof Among these, α-olefins having 3 to 12 carbon atoms are preferable, and propylene, butene-1, and octene-1 are particularly preferable.

The multilayer film of this invention may be a 2-layer film which consists of said 1st layer (A) and 2nd layer (B), and is an intermediate | middle layer between said 1st layer (A) and 2nd layer (B). As (C), a high pressure polyethylene and / or ethylene having a density in the range of 0.900 to 0.940 g / cm 2 and preferably 0.910 to 0.935 g / cm 2 and 3 to 20 carbon atoms, preferably 4 to 10 alpha- You may have a layer which consists of a copolymer with an olefin.

If the density of the ethylene polymer used for this intermediate | middle layer (C) is less than 0.900 g / cm <2>, the rigidity of an intermediate | middle layer (C) may be small, and the middle of a film may become soft, and when it exceeds 0.940 g / cm <2>, Mechanical strength, particularly impact strength, tends to be lowered.

The melt index of the ethylene copolymer is desired to be in the range of 0.5 to 50 g / 10 minutes, preferably 1 to 20 g / 10 minutes.

The melt index is less than 0.5g / 10 minutes is not preferable because the melt viscosity is high because the moldability is lower, more than 50g / 10 minutes melt viscosity is too low, the moldability is lowered, the mechanical strength of the film It is not preferable because it is lowered.

As this intermediate | middle layer (C), the high pressure polyethylene which has the said physical property may be used, the copolymer of ethylene and an alpha olefin may be used, and the mixture of both may be used.

As an alpha olefin used as a raw material monomer of the said copolymer, for example, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, dodecene- Α-olefins such as 1, tetradecene-1, octadecene-1,4-methylpentene-1,4-methylhexene-1, 4,4-dimethylpentene-1, or mixtures thereof; C4-C10 alpha olefins are preferable, but butene-1 and octene-1 are especially preferable.

The copolymer of ethylene and an α-olefin used in the first layer (A) in the multilayer film of the present invention is formed of ethylene and an α-olefin by a so-called medium-low pressure method using a transition metal catalyst. It can manufacture by superposing | polymerizing in the ratio which becomes desired density.

At this time, in order to obtain a thing having a desired melt index, the kind and amount of the chain transfer agent are appropriately selected.

As the polymerization method, various methods such as slurry polymerization method, gas phase polymerization method and solution polymerization method can be used.

Moreover, the copolymer of ethylene and alpha-olefin used for a 2nd layer (B) and an intermediate | middle layer (C) may be manufactured by the low pressure method, using a transition metal catalyst similarly to the above, You may manufacture by Moreover, the high pressure polyethylene used for an intermediate | middle layer (C) can be manufactured by carrying out radical polymerization of ethylene under high pressure.

About the thickness ratio of each layer in the multilayer film of this invention, in a two-layer film, the thickness ratio of a 1st layer (A) and a 2nd layer (B) is usually 2: 98-50: 50, Preferably 3: It is selected from the range of 97-40: 60, and in a 3-layer film, the thickness ratio of a 1st layer (A), an intermediate | middle layer (C), and a 2nd layer (B) is a 1st layer (A), When the second layer (B) has the same layer thickness, it is usually 2: 96: 2 to 40:20:40, preferably 3; It is selected in the range of 94: 3 to 30:40:30.

Moreover, the thickness of the whole multilayer film is 10-300 micrometers normally, Preferably it is 20-200 micrometers, More preferably, it is selected in the range of 30-150 micrometers.

There is no restriction | limiting in particular about the manufacturing method of the multilayer film of this invention, The method conventionally used for manufacture of a multilayer film, for example, the inflation film forming method, the T-die film forming method, etc. can be used.

At this time, the resin temperature is usually selected in the range of 200 to 300 ° C, and the chilling method is generally used in the T die molding method and the air cooling method is used in the inflation molding method for cooling the film formed.

In the chilling method, it is desired that the second layer B be in contact with the roll surface.

Cooling temperature is 20-80 degreeC normally, Preferably it selects in the range of 30-70 degreeC.

When this cooling temperature is lower than 20 degreeC, the rigidity of a film may fall, handling property may worsen, and when it is higher than 80 degreeC, film formability and the external appearance of a film will worsen, and it is unpreferable.

In the multilayer film of the present invention, antioxidants, light stabilizers, thermal stabilizers, antiblocking agents, lubricants, catalyst neutralizing agents (chlorine absorbers), antifogging agents, antistatic agents, etc. may be used as desired in any or all layers of each layer. Various additives usually used for polyethylene-based films can be added.

As said antioxidant, although a phenol type or phosphorus type is mentioned preferably, these combinations are especially preferable.

As a phenolic antioxidant, 2, 6- di-t- butyl- 4-methyl phenol, a tris (3, 5- di- t- butyl- 4-hydroxy benzyl) isocyanurate (Ciba-Geigi company, for example) Product Irganox 3114), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), n-octadecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxy Phenyl) propionate (Irganox 1076 from Chiba Co., Ltd.), 4,4 "-thiobis (3-methyl-6-t-butylphenol), tetrakis [methylene-3- (3 ', 5'-[1 -t-butyl-4'-hydroxyphenyl) propionate] methane (Irganox 1010 from Chiba Co., Ltd.), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 2, 2'-methylenebis (4-ethyl-6-t-butylphenol), N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxyhydrocinnamid) Irganox 1098), triethyleneglycol-bis- [3- (3'-t-butyl-5'-methyl-4-hydroxyphenyl) propionate], bis (3,5-di-t-butyl-4 -Mixture of ethyl hydroxyphosphonate) calcium and PE wax (parts by weight 1: 1) Inc. and the like product Irganox 1425WL).

As a phosphorus antioxidant, for example, distearyl pentaerythritol diphosphate (MARKPEP-8 made by Adega Agas Co.), tetrakis (2,4-di-t-butylphenyl), 4,4'-biphenyl Rendiphosphate (Sandostabp-EPQ), trisnonylphenyl phosphate, tris (2,4-di-t-butylphenyl) phosphate (MARK 2112 from Adega Agas company) di (2,4-di- t-butylphenyl) -pentaerythritol diphosphate (MARKPEP-24G by Adega Agas Co., Ltd.), bis- (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphate (Adega, Agas product MARKPEP-36) etc. are mentioned.

Moreover, as a light stabilizer, a salicylate type, a benzophenone type, a triazole type, an oxalate anhydride type, a hindadoamine type, etc. are used, for example.

Examples of the antiblocking agent include natural silica, synthetic silica, zeolite, amorphous zeolite, diatomaceous earth, and the like, and among them, diatomaceous earth is preferably used.

As the lubricant, for example, stearic acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, etc., as the catalyst neutralizing agent, for example, calcium stearate, zinc stearate, magnesium stearate, hydrotalcite, etc. Can be mentioned.

The multilayer film of the present invention is advantageous when the surface of the second layer (B) is subjected to surface treatment by corona discharge treatment or the like, for example, when used for lamination or when printing on the film surface.

The corona discharge treatment is usually performed at a condition of 20 w / m 2 / min or more, preferably 25 w / m 2 / min or more.

By such a surface treatment, it is desired that the wettability index of the surface of the second layer (B) is 30 dyne / cm or more, preferably 35 dyne / cm or more, more preferably 38 dyne / cm or more.

Next, when this invention demonstrates a polyethylene type multilayer film according to an accompanying drawing, FIG. 1 and FIG. 2 are sectional drawing of the different example of the multilayer film of this invention, respectively, and FIG. 1 is a 1st layer (A) 1 and a 1st drawing. A two-layer structure in which two layers (B) 2 are stacked is shown, and in FIG. 2, a first layer (A) 1 and a second layer (B) 2 are stacked in a three-layer structure via an intermediate layer (C) 3. Is displayed.

In addition, in the use of the said film, it uses so that 1st layer (A) 1 may become a seal surface.

The polyethylene-based multilayer film of the present invention has excellent low temperature sealability and seal stability, has good rigidity, activity, antiblocking property, and the like, and is excellent in handling and fast filling packaging properties. It is suitably used as a sealant base material for multilayer films.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited at all by these Examples.

In addition, each physical property of the film was calculated | required as follows.

(1) Seal temperature (light emission method)

The surface of the first layer (A) of the two multilayer films is opposed to each other, the seal is performed under the conditions of 2 kg / cm 2 and 1 sec, and the temperature when the seal strength is 300 g / 25 mm is measured. It measured using the inclination tester.

(2) Film impact (light emission method)

The full range was made into 30 kg * cm, and the beater head was made into 1 inch using the film impact tester by Dongyang Electric Co., Ltd., and measured.

(3) The impact

In accordance with ASTM D 1709A method, it measured on condition of drop height 66cm and -20 degreeC.

(4) elemental dolphin tear strength, tensile modulus

It calculated | required based on the JIS Z 1702 method.

(5) film traveling

(Exudativeness, meandering blocking property)

The evaluation was based on the following three steps.

◎: Right, ○: Quantity, △: A, ×: Not available

As the raw material resin, those shown in the first table were used.

TABLE 1

[Examples 1-6, 11, Comparative Examples 1-3, 5, 6, 9]

Each layer resin shown in a 2nd table is made into the 1st layer (A) and the 2nd layer (B), melt-kneading with the extruder of 50 mm and 60 mm, respectively, and a multi-manifold multilayer T-die (die After supplying to width 800mm) and extruding at 250 degreeC of die temperature, the film | membrane of 40 micrometers in total was obtained by contacting and cooling a 2nd layer (B) in a chiller (40 degreeC).

Subsequently, the surface of the 2nd layer (B) of this film was corona-discharge-treated on the conditions of 28w / m <2> / min, and the multilayer film was obtained.

The evaluation results of this film are shown in Table 2.

In addition, each layer thickness ratio (A) / (B) of a multilayer film is 1/6.

[Examples 7-10, 12-15, Comparative Examples 4, 7, 10]

Each layer resin shown in the 2nd table was made into the 1st layer (A), the 2nd layer (B), and the intermediate | middle layer (C), melt-kneading with the extruder of 50 mm, 60 mm, and 50 mm, respectively, and the multi-manifold multilayer T After supplying to a die (die width 800mm) and extruding at a die temperature of 250 degreeC, the film of 40 micrometers in total thickness was obtained by contacting and cooling a 2nd layer (B) in a chiller (40 degreeC).

Subsequently, corona discharge treatment was performed on the surface of the second layer (B) of this film under the condition of 28 w / m 2 / min, to obtain a multilayer film.

The evaluation result of this film is shown in a 2nd table | surface. In addition, each layer thickness ratio (A) / (C) / (B) of a multilayer film is 1/5/1.

TABLE 2

Claims (9)

(a) 60 to 95% by weight copolymer of ethylene with an density of 0.891 to 0.925 g / cm 3 and α-olefin having 4 to 20 carbon atoms (b) Ethylene and carbon number with a density of 0.860 to 0.890 g / cm 3 Of a composition having 40 to 5% by weight of a low crystalline copolymer with an α-olefin having 3 to 12 or a copolymer of ethylene having an density of 0.890 to 0.910 g / cm 3 and an α-olefin having 4 to 20 carbon atoms Polyethylene-based multilayer film comprising a first layer (A) and a second layer (B) of a copolymer of ethylene and an α-olefin having 4 to 20 carbon atoms having a density of 0.915 to 0.960 g / cm 3. . A high pressure polyethylene and / or ethylene having 3 to 20 carbon atoms according to claim 1, wherein the density is between 0.900 and 0.960 g / cm 3 between the first layer (A) and the second layer (B). Polyethylene-based multilayer film having an intermediate layer (C) consisting of a copolymer with an olefin. The composition for forming the first layer (A) has a (a) copolymer having a melt index of 1 to 50 g / 10 minutes, and a melt index of 0.5 to 10 g / 10 minutes. b) Polyethylene-based multilayer film composed of a low crystalline copolymer. The composition of claim 1, wherein the composition forming the first layer (A) comprises (a) a copolymer having an ethylene unit and an octene-1 unit, and (b) a low crystallinity having an ethylene unit and a butene-1 unit. Polyethylene-based multilayer film made of a copolymer. The polyethylene-based multilayer film according to claim 1 or 2, wherein the copolymer forming the first layer (A) has a melt index of 1 to 50 g / 10 minutes and an ethylene unit and an octene-1 unit. The polyethylene according to claim 1 or 2, wherein the second layer (B) is a copolymer having a melt index of 0.5 to 39 g / 10 minutes and having an ethylene unit and a propylene unit, butene-1 unit or octene-1 unit. Type multilayer film. The polyethylene-based multilayer film according to claim 1 or 2, wherein the intermediate layer (C) is a copolymer having a melt index of 0.5 to 50 g / 10 minutes and an ethylene unit and butene-1 unit or octene-1 unit. The polyethylene-based multilayer film according to claim 1, wherein the polyethylene-based multilayer film is a two-layer film, and the thickness ratio of the first layer (A) and the second layer (B) is 2:98 to 50:50. The method of claim 2, wherein the polyethylene-based multilayer film is a three-layer film, the first layer (A) and the second layer (B) is the same thickness, and the first layer (A), the intermediate layer (C) and the second Polyethylene-based multilayer film having a thickness of the layer (B) of 2: 96: 2 to 40:20:40.

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