JPH0796281B2 - Method for manufacturing laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing a laminated film.

More specifically, the present invention provides a low density polyethylene having a melt flow rate of 0.5 to 50 g / 10 minutes and a density of 0.935 g / cm ³ or less between a base material thin film and a polyolefin thin film and 10% by weight or more of ethylene- Acrylic ester copolymer, or, after melt-extruding a resin composition comprising an ethylene-methacrylic acid ester copolymer at a temperature of 250 ~ 340 ℃, relates to a method for producing a laminated film, which is pressure-bonded Is.

<Prior Art> In recent years, the performance required for packaging materials has been remarkably diversified with the expansion of packaging functions, and various laminated films have already been put on the market.

Generally, as a packaging material, a plastic film of stretched polyamide, stretched polyethylene terephthalate, cellophane or the like is used on the side that becomes the outer surface after bag making, and a polyolefin resin is used on the inner surface, that is, the heat-sealing surface. Third resin in the middle layer,
Alternatively, one or more layers of metal foil such as aluminum may be stuck together.

In such a laminated film, how to bond the layers is a problem. As a method for adhering the inner surface and the outer surface of the laminated film, an ethylene copolymer such as an ionomer or an ethylene-acrylic acid copolymer, or a method of laminating a high-pressure low-density polyethylene by extrusion coating, a method of laminating with an adhesive, etc. are applied. To be done.

However, ethylene copolymers such as ionomers and ethylene-acrylic acid copolymers are expensive, and a sufficient combination of materials such as polyethylene terephthalate, polyamide, polypropylene and the like cannot be obtained.

Further, even with the high-pressure method low-density polyethylene, unless sufficient corona treatment or application of an anchor coating agent is applied to the base material, the adhesive strength sufficient for practical use cannot be obtained.

On the other hand, the method of sticking with an adhesive not only raises the equipment cost of an apparatus for drying the organic solvent because the organic solvent is used as the solvent, but also has safety and health problems.

<Problems to be Solved by the Invention> An object of the present invention is to provide a method for producing a laminated film, which is inexpensive and has excellent interlayer adhesiveness, in relation to the above problems.

<Means for Solving Problems> The present invention relates to a low-density polyethylene having a melt flow rate of 0.5 to 50 g / 10 min and a density of 0.935 g / cm ³ or less between a substrate thin film and a polyolefin thin film. A resin composition comprising an ethylene-acrylic acid ester copolymer or ethylene-methacrylic acid ester copolymer in an amount of at least 50% by weight is used.
The present invention relates to a method for producing a laminated film, which comprises melt-pressing at a temperature of ˜340 ° C. and then pressure bonding.

The substrate used in the present invention is a plastic film such as stretched polyamide, stretched polyethylene terephthalate, cellophane, and stretched polypropylene, paper, or a metal foil such as aluminum foil. Alternatively, if necessary, a surface treatment such as corona treatment or fire treatment, a preprinted product, a single substance or a laminate of two or more layers may be used.

The polyolefin layer used in the present invention is a film or sheet of low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and the like, and a mixed composition thereof.

The low-density polyethylene, which is one component of the resin composition as the adhesive layer used in the present invention, is a polymer containing ethylene as a main component, which is produced by a radical polymerization method or an ionic polymerization method.

In the radical polymerization method, low density polyethylene is obtained by polymerizing ethylene using an organic group generator such as organic peroxide or oxygen. The polymerization reaction is usually 130
It is carried out at a polymerization temperature of ˜300 ° C. and a polymerization pressure of 500˜3000 kg / cm ² .

In the ionic polymerization method, ethylene and 3 to 18 carbon atoms are used.
The low density polyethylene can be obtained by copolymerizing the α-olefin of (1) with a transition metal catalyst. The copolymerization reaction is usually carried out at a polymerization temperature of 30 to 300 ° C. and atmospheric pressure to 3000 kg / cm ^2.
Polymerization pressure, in the presence or absence of a solvent, gas-solid,
Examples are carried out in a single liquid or under a uniform liquid phase. As the α-olefin, propylene, butene-1, 4-methypentene-1, hexene-1, octene-1, decene-1 and the like are used, but those having 4 to 10 carbon atoms are preferable. These α-olefins may be used alone or in combination of two or more.

The density of the low density polyethylene used in the present invention (JIS K676
0) is at 0.935 g / cm ³ or less, preferably in to free 0.900 in the range of 0.930 g / cm ^3. When the density is higher than 0.935 g / cm ³ , the mixing and dispersibility with the ethylene-acrylic acid ester copolymer or the ethylene-methacrylic acid ester copolymer is deteriorated and the adhesive strength is lowered.

The melt flow rate of polyethylene (JIS K6760) is 0.
It is 5 to 50 g / 10 minutes, preferably 2 to 15 g / 10 minutes. If the melt flow rate is lower than 0.5 g / 10 minutes, the melt viscosity becomes too high, which makes extrusion difficult and also reduces the adhesive strength. On the other hand, when it is higher than 50 g / 10 minutes, the strength of the laminated film is lowered.

The ethylene-acrylic acid ester copolymer or ethylene-methacrylic acid ester copolymer, which is one component of the resin composition as the adhesive layer, comprises a monomer copolymerizable with ethylene (hereinafter referred to as a comonomer). It is obtained by copolymerization using a free radical generator such as organic peroxide or oxygen. The copolymerization reaction is usually carried out at a polymerization temperature of 130 to 300 ° C. and a polymerization pressure of 500 to 3000 kg / cm ² .

Examples of the ethylene-acrylic acid ester copolymer include copolymers of ethylene and methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like.

Specific examples of the ethylene-methacrylic acid ester copolymer include copolymers of ethylene with methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and the like. These copolymers can be used not only in one kind but also in a mixed composition of two or more kinds.

The content of the comonomer contained in these ethylene-acrylic acid ester or ethylene-methacrylic acid ester copolymer is 3 to 30% by weight, preferably 10 to 25% by weight. 3% by weight comonomer content
If it is lower, the desired adhesiveness cannot be obtained. On the other hand, if it is higher than 30% by weight, the adhesive strength between the layers which is the object of the present invention is sufficient, but the manufacturing cost becomes high and the heat during extrusion melting is high. Stability decreases. The ethylene copolymer used in the present invention has a melt flow rate (JIS K6730) of 0.5 to 50 g / 1.
It is 0 minutes, and preferably in the range of 2 to 15 g / 10 minutes. When the melt flow rate is lower than 0.5 g / 10 minutes, not only the melt extrusion becomes difficult, but also the adhesive strength decreases.
On the other hand, if it is higher than 50 g / 10 minutes, the mixing and dispersibility with low-density polyethylene deteriorates and the strength of the laminated film decreases. As the resin composition which is the adhesive layer of the present invention, the composition of low-density polyethylene and ethylene-acrylic acid ester copolymer or ethylene-methacrylic acid ester copolymer is used, and the latter is 10% by weight or more, and It is preferably in the range of 10% by weight to 50% by weight.

Ethylene-acrylic acid ester copolymer or ethylene-
When the content of the methacrylic acid ester copolymer is less than 10% by weight, the adhesiveness between the base material layer and the polyolefin layer is insufficient and the object of the present invention cannot be achieved. Even if 50% by weight or more is added, no further effect can be expected when a certain adhesive strength is reached.

The resin composition as the adhesive layer of the present invention can be obtained by uniformly mixing the components used in the present invention.

As the mixing method, various known methods for mixing the respective components within the above range, for example, a method of dry blending using a mixer such as a Henschel mixer or a tumbler blender, a melt-kneading process using a single-screw extruder or a multi-screw extruder after mixing A method of granulating or a method of melt-kneading and granulating with a Banbury mixer, a kneader, a roll mill or the like can be adopted.

As for the mixing of the respective components, they can be mixed at once, or a part thereof can be premixed and then further mixed with the remaining part.

The resin composition as the adhesive layer of the present invention, other known compounding agents such as weathering stabilizers, antioxidants, antistatic agents, antifog agents, slip agents, lubricants, antiblocking agents, dyes, pigments, inorganics. Alternatively, it may contain an organic filler or the like.

The method for producing a laminated film of the present invention can be obtained by melt-extruding the resin composition as an adhesive layer between the substrate thin film and the polyolefin thin film and then press-bonding.

As a specific example of an apparatus used for manufacturing a laminated film,
An extrusion lamination processing device capable of sandwich lamination molding can be mentioned.

The melt extrusion temperature of the resin composition as the adhesive layer is 250 to 340 ° C, preferably 280 to 320 ° C. 250
When the temperature is lower than ℃, the adhesive strength between the base material and the polyolefin thin film is insufficient, and when the temperature is higher than 340 ° C, the adhesive strength is lowered due to the thermal deterioration of the resin composition and the strength of the laminated film is also lowered.

The laminated film obtained by the present invention can be used as various packaging materials by subjecting it to secondary processing such as heat sealing.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.

In the examples and the comparative examples, the adhesive strength is 15 mm in width, cut out a tanzaque-shaped test piece, and using a tensile tester, the strength when peeled in the direction of 180 degrees at a speed of 500 mm / min. It is shown in units of g / 15 mm.

Physical properties and measurement methods of the base material thin film polyolefin thin film used in Examples and Comparative Examples, and low-density polyethylene as an adhesive layer, ethylene-acrylic acid ester copolymer, and ethylene-methacrylic acid ester copolymer are shown below. .

[(A) Substrate thin film]

 (I) Stretched polypropylene film (Toyobo Co., Ltd.)
Made, brand name Pyrene-OT P 2102, thickness 20μ, below OP
P) (ii) Stretched nylon film (manufactured by Toyobo Co., Ltd., high
Den The thickness is 15 μ, and is referred to as o-Ny hereinafter. ) (Iii) Aluminum evaporated polyester film (Toyo Metalla
Ising Co., Ltd., thickness 12μ, hereinafter referred to as VM-PET. ) [(B) Polyolefin thin film) (i) Unstretched polypropylene film (Toyobo Co., Ltd.)
Made, trade name Pyrene-CT P1120 Thickness 30μ, and below CPP
say. (Ii) Polyethylene film (manufactured by Aicero Chemical Co., Ltd.,
Product name Suzuron L L100, thickness 40μ, below, PE fill
It is called Mu. ) [(C) Low-density polyethylene] Sumikasen L705 (Sumitomo Chemical
Industrial Co., Ltd., melt flow rate 7.0 density 0.919, below
LDPE) was used.

[(D) Ethylene-ethyl acrylate copolymer]

As the ethylene-ethyl acrylate copolymer, a grade having an ethyl acrylate content of 20% by weight and a melt flow rate of 20 g / 10 min (hereinafter referred to as EEA) was used.

[(E) Ethylene-methyl methacrylate copolymer]

Ethylene-methacrylic acid copolymer, methyl methacrylate content 15 wt% melt flow rate 7g / 10
Minute Great (hereinafter referred to as EMMA) was used.

The melt flow rate (hereinafter referred to as MFR) and the density were measured as follows.

Complies with JIS-K6760 and JIS-K6730 (EVA) MFR: Under the specified temperature and pressure conditions, find the extrusion rate of the molten resin extruded through the specified orifice, and display it as the mass per 10 minutes.

Approximately 5g Temperature 190 ± 0.5 ℃ Preheating time 5 minutes Load 2.16kg Melt indexer (Takara Industry Co., Ltd.) MX-101 type Density: Sample preparation: The sheet was annealed at 100 ° C for 60 minutes and then slowly cooled,
Leave for 24 hours at 3 ℃ and 50% RH.

Test temperature: 23 ° C. ± 0.1 ° C. Test method: Density gradient tube Examples 1 to 3 LDPE and EEA were preliminarily used in a tumbler for 20 minutes at room temperature (dry blending was performed at about 25 ° C. (first.
The table below shows the blending amounts of LDPE and EEA. ) The obtained mixtures were granulated while kneading the mixture at a temperature of 200 ° C in an extruder. Each composition was extruded using a T-die extruder at a resin temperature of 310 ° C immediately below the die, and OPP, O-Ny, VM-PET were placed on the base material side using a sandwich laminator, and CPP and PE were placed on the polyolefin layer side. Each film was used for press bonding and extrusion lamination at each line speed of 80 m / kg. The thickness of the LDPE and EEA mixture is 20μ. The adhesive strength between the layers of the laminated film obtained as described above was measured. The results are shown in Table 1.

Comparative Example 1 A laminated film using only LDPE for the adhesive layer was produced under the same conditions as in the Example, and the adhesive strength between the layers was measured in the same manner.

Comparative Example 2 Table 1 shows the results of measuring the adhesive strength in the same manner as in Examples 1 to 3 except that a resin composition containing 95% by weight of LDPE and 5% by weight of EEA was used as the resin composition composition of the adhesive layer.

Examples 4 to 6 EMMA was used instead of EEA in Examples 1 to 3 and the adhesive strength was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 95% by weight of LDPE and 5% of EMMA of the resin compositions of Examples 4 to 6 were used.
Table 1 shows the results of measuring the adhesive strength in the same manner as in Examples 1 to 3 except that the weight percentage was changed.

<Effects of the Invention> As described above, the laminated film according to the present invention provides excellent interlayer adhesion, and can be applied to various packaging materials.

Claims (1)

[Claims] 1. A melt flow rate of 0.5 to 50 g / 10 minutes and a density of 0.935 g / cm ³ between a substrate thin film and a polyolefin thin film.
25% by weight of the following low-density polyethylene and ethylene-acrylic acid ester copolymer, or ethylene-methacrylic acid ester copolymer resin composition consisting of 25
A method for producing a laminated film, which comprises melt-extruding at a temperature of 0 to 340 ° C. and then pressure bonding