JP2545576B2 - Thermoplastic resin film and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermoplastic resin film having excellent transparency and gas barrier properties, and a method for producing the same.

[Conventional technology and its problems]

It has been widely known that a thermoplastic resin such as polyethylene resin, polypropylene resin or polystyrene resin is extruded from an extruder through a T-die or the like to form a film. This film is formed into a packaging material, a container or the like by a vacuum forming machine or the like. However, since the thermoplastic resin as described above generally has a poor gas barrier property, it has a drawback that the aroma retaining property of the container is inferior, and oxygen gas invades, the contents easily rot, and the storage period cannot be extended. Had.

In order to improve such a defect, a five-layer film has been developed in which both surface layers are made of a thermoplastic resin, an intermediate layer is made of a gas barrier resin, and an adhesive resin layer is provided between both surface layers and the intermediate layer. However, in the case of such a five-layer laminated film, its manufacturing apparatus becomes complicated, and it is difficult to form a uniform multilayer,
Moreover, there is a problem that it is difficult to select an appropriate adhesive material.

In general, a polyolefin resin and a gas barrier resin have no adhesiveness to each other, and therefore, in order to obtain a laminated film of the both, it is necessary to interpose an adhesive layer between them. In addition, an adhesive resin is required. Therefore, in order to extrude such three kinds of molten resins, three extruders are required. Further, in order to form three kinds of molten resins into a gas barrier laminated film consisting of five layers as described above, a laminating apparatus for distributing and laminating into five layers is required, but this five-layer laminating apparatus is very complicated. Not only is this expensive and expensive, but even with this expensive laminating device, 3
It is difficult to stably obtain a film having a uniform five-layer structure due to a difference in melt viscosity between different types of resins, a difference in resin pressure, and the like, and a high level of operation technology is required. That is, when the three types of thermoplastic resins merge, if the respective viscosities, pressures, and flow velocities are not substantially uniform, there are problems such as generation of flow marks, uneven wall thickness, and uneven distribution of the gas barrier resin layer. appear.

Further, depending on the combination of the polyolefin resin and the gas barrier resin, there is a material in which a suitable adhesive has not been found yet. Actually, in the case of polyethylene and a polyamide resin containing a metaxylene group (hereinafter abbreviated as MX nylon), a suitable adhesive has not been found yet. On the other hand, when a small amount of a gas barrier resin is simply blended with a polyolefin resin by a screw of an extruder, the gas barrier resin is dispersed in the polyolefin resin in the form of fine particles. The gas barrier property only changes linearly with the mixing ratio of. Furthermore, in the case of this blend film, the dispersed fine particles have a wide distribution from large particles to small particles, and there are many particles with a particle diameter close to the wavelength of visible light, so the visible light is scattered by the particles. However, it becomes a cloudy film.

In a multilayer film, its gas permeability coefficient is determined by the following equation.

_{1 / P = n 1 / P} 1 + n 2 / P 2 (1) P: gas permeability coefficient of the multilayer film P _1: polyolefin resin of the gas permeability coefficient P _2: the gas barrier material gas permeability coefficient n _1: the polyolefin resin Ratio n ₂ to the total thickness n ₂ : Ratio to the total thickness of the gas barrier material n ₁ + n ₂ = 1 Therefore, in the case of a multilayer film, only a very thin gas barrier layer exists in the entire thickness, and the rapid gas barrier effect A film is obtained. The larger the ratio of the gas permeation coefficient between the polyolefin resin and the gas barrier resin, the more remarkable the effect. When the gas permeability of the multilayer film is measured while changing the thickness of the gas barrier material, the curve 1 in FIG. 1 is obtained. On the other hand, in the case of a simple mixed resin film, the curve is as shown by curve 2 in FIG. From these figures, it can be seen that when the same amount of gas barrier resin is used, the multilayer film has a gas barrier effect more than the simple mixed resin film.

Since the gas barrier material is more expensive than the polyolefin-based resin, it is better to use the gas barrier material in a smaller amount, and if a multilayer structure is used, sufficient gas barrier properties can be obtained with a small amount.

〔Purpose〕

A first object of the present invention is to provide a multi-layer structure,
It is an object of the present invention to provide a film having a gas barrier effect equivalent to that of a multi-layered structure with a single-layered structure without requiring an expensive laminating device and an adhesive resin.

Another object of the present invention is to provide a film having excellent transparency and gas barrier properties by bringing a thermoplastic resin and a small amount of gas barrier resin into a special mixed state.

[Means for solving problems]

According to the present invention, it is composed of a base thermoplastic resin A and an auxiliary thermoplastic resin B, and the auxiliary resin B is the base resin A.
There is provided a thermoplastic resin film having a plurality of dispersed films or tapes therein. Further, according to the present invention, the base thermoplastic resin A and the auxiliary thermoplastic resin B are separately melted, and then the two resins are joined together, and then passed through a static mixer to be mixed to form a film. A method for manufacturing a thermoplastic resin film is provided.

Although the film obtained by the present invention is a mixed resin film composed of two resins, the base resin A
Since the auxiliary resin B blended as the auxiliary component exists in the form of a plurality of dispersed films or tapes in the film, it exhibits substantially the same function and effect as the multilayer film constituted by both resins.

In general, when the two kinds of thermoplastic resins A and B are heated and melt-mixed with a screw of an extruder, the phase distribution is observed with a microscope. As shown in FIG. The resin B is mixed and dispersed in the form of particles. Further, the distribution state of the particle diameter d of the resin B has a wide distribution width as shown in FIG. Therefore, in the case of mixing with a screw, a large number of resin B particles having a diameter of 1/10 micron to about 10 micron, which causes haze, are always present. That is, the film formed from the resin in such a mixed state becomes cloudy due to the added resin B.

On the other hand, in the case of the film obtained by the present invention, as shown in FIG. 4, the auxiliary resin B is present in the base resin A in the form of a plurality of dispersed films or tapes. The auxiliary resin B exists along the film surface in a substantially parallel state. The width h of the layered product made of the resin B as seen from above the film has a distribution state as shown in FIG. 5, and the distribution width of h becomes very narrow.

The film of the present invention having a multi-layered structure in the film as described above is prepared by extruding the base resin A and the auxiliary resin (B) as an auxiliary component (or the addition resin B) in a melted state and joining them together, and then using a static mixer. Mix both,
It can be obtained by forming a film through an annular die or a T-die. There are various types of static mixers, but the static mixer used in the present invention is a static mixer without a driving unit, in which a square plate is twisted 180 ° to the right in a pipe. It has a structure in which a large number of bent right elements and a large number of left elements twisted 180 ° to the left are alternately arranged. An explanatory view of this static mixer is shown in FIG. In FIG. 6, 1 indicates a pipe, 2 indicates a right element, and 3 indicates a left element. The fluids are mixed while flowing in the direction of the arrow. When using this static mixer,
The fluids are mixed by the following three actions.

(1) Division of fluid The fluid is divided into two each time it passes through one element. If the number of divisions is S and the number of elements is n, the relationship of S = 2 ⁿ is established.

(2) Reversal of flow Since the right element and the left element are arranged alternately, the flow is reversed every time each element is passed.

(3) Flow conversion Along the twisted surface of the element, from the center to the wall,
The flow moves from the wall to the center.

In the present invention, when the resin A and the resin B are brought together in a molten state and passed through a static mixer,
As shown in FIG. 4, the auxiliary resin B is present in the form of a plurality of films or tapes dispersed in the base resin A, and the long axis direction of the film or tape-shaped shaped body is the resin flow direction. Matches The width h of the film-shaped or tape-shaped shaped body is controlled by the number of elements and the inner diameter of the pipe, and by controlling this width h, a film having no haze and excellent transparency can be obtained. In the case of the present invention, the number n of elements of the static mixer is 5 to 15, preferably 8 to 12, and the inner diameter D of the pipe is 10 to 50 mm, preferably 20 to 40 mm. Also,
The width h of the layered material is usually 10 to 10000 μm, preferably 100 to
It is 1000 μm.

 Next, the gas barrier property of the film will be described.

In general, a gas barrier resin such as nylon or ethylene / vinyl alcohol copolymer has a gas barrier property several tens to several thousands times that of a polyolefin resin. The ratio of oxygen permeability coefficient between polyethylene and MX nylon is about
It is 600 times. In the case of mixing of polyethylene and MX nylon with a screw, as shown in Fig. 2, MX nylon is dispersed in the form of particles, so gas can diffuse smoothly in polyethylene. It only changes linearly according to the mixing ratio of However, in the case of special mixing with a static mixer, as shown in FIG. 4, MX nylon is dispersed in a layered form, so gas cannot pass smoothly and a gas barrier performance equivalent to that of a multilayer film can be obtained. In other words, in the case of special mixing of polyethylene and MX nylon with a static mixer, the relationship of 1 / P = 0.9 / Po + 0.1 / Po / 600 is obtained from the above formula (1) simply by mixing MX nylon with 10 vol%. The formula holds, P = Po / 60.9, and a gas barrier property of about 61 times is obtained.

In the case of the film composed of the special mixed resin layer according to the present invention, the resin B added on both sides of the film is present, but in this case, when the resin B is exposed on the surface, the surface condition of the film is not good. Is hygroscopic, there is a possibility that inconveniences such as water absorption and crystallization of the resin B may occur. Therefore, in order to avoid such inconvenience, the film is used as an intermediate layer and the resin A
It is preferable to laminate and adhere a film made of the same or the same kind of resin A as the outer layer. In this case, the films can be easily and firmly adhered to each other because the films are made of the same or the same kind of resin. Generally, if the proportion of the matrix resin A in the film made of the special mixed resin layer is 60 vol% or more, sufficient adhesion can be achieved.

Examples of the base thermoplastic resin A used in the present invention include polyolefin resins such as polyethylene and polypropylene copolymers thereof, polystyrene, polyacrylonitrile, polyester, polycarbonate, polyvinyl chloride and modified resins thereof. Can be given.

As the auxiliary resin B used in the present invention, for example, a gas barrier resin is preferably used. Examples of such materials include MX nylon, saponified ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinylidene chloride resin, polyacrylonitrile copolymer, nylon 6, nylon 6, nylon 6, 6 mag.

As the MX nylon, for example, metaxylylenediamine alone or metaxylylenediamine and 30% of the total amount
A polymer containing at least 70 mol% or more of a constituent unit obtained from the following mixed xylylenediamine containing para-xylylenediamine and an α · ω-aliphatic dicarboxylic acid having 6 to 10 carbon atoms can be mentioned.

Examples of these polymers include homopolymers such as polymeta-xylylene adipamide, polymeta-xylylene sepacamide, poly-meta-xylylene speramide, meta-xylylene / para-xylylene adipamide copolymer, meta-xylylene / Copolymers such as paraxylylenepimelamide copolymers, metaxylylene / paraxylenenaphtheramide copolymers and the components of these homopolymers or copolymers, and aliphatic diamines such as hexamethylenediamine and piperazine. Alicyclic diamines, aromatic diamines such as para-bis- (2-aminoethyl) benzene, aromatic dicarboxylic acids such as terephthalic acid, lactams such as ε-caprolactam, and ω-aminoheptanoic acid. with aromatic aminocarboxylic acids such as ω-aminocarboxylic acid and para-aminobenzoic acid It can be exemplified polymer.

Further, it is advantageous to use a heat resistant resin as the auxiliary resin B used in the present invention, and in this case, a film having excellent heat resistance can be obtained. In this case, examples of the heat resistant resin include polyamide resin, saturated polyester resin, polypropylene resin, polycarbonate resin and the like. Further, as the auxiliary resin B, an appropriate resin can be used according to the desired improvement in physical properties.

The blending amount of the auxiliary resin B is generally 1 to 40 vol% with respect to the mixture of the resin A and the resin B, and in the case of the gas barrier resin, the addition of 1 to 25 vol% provides sufficient gas barrier property. It is possible to obtain a film having

Next, FIG. 7 schematically shows an apparatus for producing a film comprising the special mixed resin layer of the present invention. In FIG. 7, 10 is an extruder for base resin A, 11 is an extruder for auxiliary resin B, 12 is a static mixer, 13 is a T die, 14 and 15 are cooling rolls, and 17 is a film.

In this apparatus, a resin A and a resin B are extruded in a molten state from an extruder 10 and an extruder 11, respectively, and these resins are joined in a passage P, mixed in a static mixer 12, and then film-formed from a T die 13. Is extruded into. This film is cooled by chill rolls 14 and 15, then roll 1
It is guided by 6 and is designated as product film 17.

Further, FIG. 8 shows a schematic view of a laminated film manufacturing apparatus having a structure in which another film is laminated and adhered on both sides of the film of the present invention. In FIG. 8, molten resins A and B are extruded from extruders 10 and 11, respectively, and these resins are joined in a passage P, mixed in a static mixer 12, and sent to a laminating apparatus 20. On the other hand, a part of the resin A from the extruder 10 is sent to the laminating apparatus 20 through the passage 19. In the laminating apparatus 20, the resin A is laminated in layers on both sides of the special mixed resin layer composed of the resin A and the resin B, and the laminated product is formed into a film by the T die 13, and then the cooling rolls 14 and 15 are formed.
After passing through the guide roll 16, the product film 17 having a thickness of usually 10 to 1000 μm is formed by the guide roll 16.

The laminated film of the present invention can be produced as described above, and can also be produced by laminating the laminating film on both sides of the film comprising the special mixed resin layer of the present invention and thermocompression bonding.

[Operation and effect of the invention]

Since the film comprising the special mixed resin layer of the present invention has the internal multilayer structure as described above, it has the same function as a conventional multilayer film. Moreover, the production of the film is extremely easy because it does not require an adhesive resin, an extruder or a laminating device.

When the film using a gas barrier resin as the auxiliary resin B of the film of the present invention is packaged, oxygen is less likely to enter the package, the contents can be stored for a long time, and the transparency is good. The state of the contents can be observed from the outside.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

The methods for measuring the physical properties shown below are as follows.

(1) Haze: [(diffuse transmitted light amount) / (total transmitted light amount)] x 100 (%) * JIS-K-6714 or ASTM D883-62T, Nippon Denshoku Industries Co., Ltd. Digital Haze Meter NDH-2D Use (2) Oxygen permeability: Use OXTRAN100 made by Modern Control, measurement temperature 20
° C, inner relative humidity 100%, outer relative humidity 65% Examples 1 to 6 and Comparative Examples 1 to 2 Using a device as shown in Fig. 7, a film having a thickness of 50 µm was produced. In this case, the thermoplastic resin A is polyethylene (melt index 2.0 g / 10 min) or polystyrene, and the auxiliary resin B is polymethaxylylene adipamide (hereinafter abbreviated as N-MXD6) or nylon 6 (hereinafter N-).
(Abbreviated as 6) was used. Inner diameter of static mixer is φ30
The number of elements is 7 in mm. The manufacturing conditions are as follows.

(Thermoplastic resin A extruder) Cylinder inner diameter: 50 mm Cylinder temperature: 260 ° C Cylinder discharge rate: 10 kg / hr (Auxiliary resin B extruder) Cylinder inner diameter: 30 mm Cylinder temperature: 260 ° C Comparative example 3 N-6 in polyethylene The raw materials were blended so as to be 25 vol% and extruded from a polyethylene extruder.
The static mixer was removed and the auxiliary resin B extruder was stopped.

Table 1 shows the physical properties of the films obtained as described above.

Examples 7 to 8 Multilayer films were produced using the apparatus shown in FIG. In this case, polyethylene (melt index 2.0 g / 10 min) was used as the resin A, and polymethaxylylene adipamide (N-MXD6) was used as the resin B. The operating conditions of each extruder are the same as in the case of the first embodiment. The film obtained from this device has a three-layer structure in which the intermediate layer is a special mixed resin layer (thickness: 150 μm) consisting of polyethylene and N-MXD6, and polyethylene layers (thickness: 100 μm) are laminated on both sides. (The total thickness: 350μ
m).

Comparative Example 4 A film having a three-layer structure was produced in the same manner as in FIG. 8 except that the static mixer 12 was removed.

Table 2 shows the physical properties of each film obtained as described above.

In addition, in Examples 7 to 8 and Comparative Example 4, a film having the same composition and the same layer ratio and a total thickness of 50 μm was separately manufactured, and the haze and oxygen permeability were measured with this film.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a difference in gas barrier property between a simple mixed single layer film and a multilayer film by a screw in a film composed of a thermoplastic resin and a gas barrier resin. FIG. 2 is an explanatory view showing a state of the added resin B distributed in the base resin A when the resin composed of two kinds of the base resin A and the added resin B is heated and melt mixed in the extruder. FIG. 3 is a diagram showing a distribution state of particle diameters of the gas barrier resin B dispersed in the simple mixed resin film. FIG. 4 is an explanatory view showing a special mixed state of the resin A and the resin B in the present invention. FIG. 5 is a view showing a distribution state of the width h of the gas barrier resin B existing in the form of a plurality of dispersed films or tapes in the film of the present invention. FIG. 6 is an explanatory diagram of the static mixer. FIG. 7 is a schematic view of an apparatus for producing the special mixed resin film of the present invention. FIG. 8 shows a schematic diagram of an apparatus for producing the multilayer film of the present invention. 1 ... pipe, 2 ... right element, 3 ... left element, 10 ... thermoplastic resin A extruder, 11 ... auxiliary resin B extruder, 12 ... static mixer, 13 ... T die, 1
4,15: Cooling roll, 17: Product film, A: Base resin, B: Auxiliary resin.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29L 9:00

Claims (6)

(57) [Claims] 1. A base thermoplastic resin A and an auxiliary thermoplastic resin B
A thermoplastic resin film, wherein the auxiliary resin B is present in the form of a plurality of dispersed films or tapes in the base resin A. 2. A base thermoplastic resin A and an auxiliary thermoplastic resin B.
And a thermoplastic resin A which is the same as or similar to the base resin A laminated and adhered on both sides of the intermediate layer.
A thermoplastic resin film, wherein the auxiliary resin B is present in the form of a plurality of dispersed layers in the intermediate layer. 3. The film according to claim 1, wherein the auxiliary resin B is a gas barrier resin. 4. A base thermoplastic resin A and an auxiliary thermoplastic resin B.
A method for producing a thermoplastic resin film, characterized in that the two resins are separately melted, and then the two resins are brought together and then passed through a static mixer to be mixed to form a film. 5. A base thermoplastic resin A and an auxiliary thermoplastic resin B
Are separately extruded in a molten state, passed through a static mixer, the obtained resin flow is used as an intermediate layer, and a thermoplastic resin A in the same or the same molten state as the base resin is in a layered contact with both surfaces of the intermediate layer. A method for producing a thermoplastic resin film, which comprises integrally forming a film. 6. A base thermoplastic resin A and an auxiliary thermoplastic resin B
Are separately extruded in a molten state, passed through a static mixer to form a film, and the film is used as an intermediate layer, and a film made of the same or the same kind of the thermoplastic resin A as the base resin is thermocompression bonded to both surfaces of the film. A method for producing a thermoplastic resin film, comprising: