JPS592816A - Manufacture of adherent film - Google Patents

Abstract

PURPOSE:To obtain the titled film which is improved in the adhesion of its inner surface and is excellent in heat resistance as well as useful for the automatic packing of a liquid food, by a method wherein a flat tubular film formed from a high-density PE or the like by means of inflation technic is subjected to a corona discharge treatment from the outside. CONSTITUTION:A high-density PE or PP is melted and kneaded in an extruder and then extruded from a circular slit at preferably 180-230 deg.C to form a hollow film. A gas is blown into the inside of the hollow film to effect air-cooling, thereby to carry out inflation. The obtained flat tubular film is subjected to a corona discharge treatment from the outside thereof, preferably continuously, so that the wet tension of the outer surface of the tubular film immediately after the treatment is preferably 45 dyne/cm or more, thereby to obtain a desired film having an adhesion degree of, preferably, 10-50g/100cm<2>. USE:An automatic packing container and the like for juice, soybean curd and the like.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing an adhesive film.

More specifically, the present invention relates to a method for producing an adhesive film suitable for producing containers for automatically filling liquid foods such as jars and tofu.

In order to automatically fill liquid foods, etc., prepare a large number of synthetic resin sheets that are heat-sealed or otherwise formed into container shapes, and then feed them continuously into an automatic filling device where they are inserted into the filling nozzle from the mouth of the container. It is commonly used to insert liquid food into the container and fill it with liquid food.

Conventionally, low-density polyethylene has been used for this type of application, but low fI 1 degree polyethylene has a softening temperature of r
Z~? j Since it is low at 0, is it food etc.? / 00'
When filling after high-temperature sterilization at a temperature higher than Q, there was a drawback that filling could not be done at that temperature.

When high-density polyethylene or polypropylene is used, the softening temperature is high, so the heat resistance is good, but other drawbacks occur.

The drawback is that films made of high-density polyethylene or polypropylene have a large surface roughness, so the films do not stick together.

This drawback becomes a big problem when automatic filling is performed. In other words, when a container formed by heat-sealing the above-mentioned film is inserted through the mouth of an automatic filling device, the films do not adhere to each other, so the interface between the films peels off significantly, causing damage inside the container. This causes excessive air to enter.

Air entering the container not only causes spoilage of the filled liquid food 2, but also causes serious problems such as uneven filling amount, resulting in overfilling or underfilling.

In view of the above-mentioned circumstances, the inventors of the present invention have conducted extensive research and found that it is possible to produce a film with good adhesion by producing the film using a specific method using high-density polyethylene or polypropylene. They discovered this and completed the present invention.

That is, the gist of the present invention is to apply a corona discharge treatment to a flattened cylindrical film obtained by inflation molding high-density polyethylene or polypropylene from the outer surface thereof, thereby improving the inner surface of the cylindrical film. The present invention relates to a method for producing an adhesive film, which is characterized in that it is brought into close contact.

The resin used in the method of the present invention is high density polyethylene or polypropylene, and has a softening temperature of 7000 or higher.

High-density polyethylene has a melt index (M) of 0.
07-1077710 minutes, preferably O0Q~! 9/1
0 minutes, dense W0.9 da ~ 0, ? 7 g/all,
Preferably θ, 9 to θ, 94 9/-1 softening temperature/1
The polypropylene has a melt flow index (MFI) of /~/gl/10 min, preferably 7~109710. min, density o, r≦~0.9211
/di, preferably O0♂7~0.9/V (d1 softening degree/20~/j C1 preferably 13θ~/
j O'Q is preferred. These high-density polyethylenes or polypropylenes are preferably ethylene or propylene homopolymers, but may be non-polymers by adding appropriate copolymer components depending on the purpose.

Antioxidants are added to these raw resins depending on the purpose.

Sumata ultraviolet arc absorber, heat stabilizer, antistatic agent, flame retardant, RuO In the method of the present invention, the film is formed by inflation molding. Inflation molding involves melting and kneading the above raw material resin using an extruder, extruding the molten resin through a die with circular slits, and blowing gas into the hollow film to make it expand into a thin film. There are two methods for cooling the extruded film: an air cooling method using an air ring provided at the top of the die, and a water cooling method that brings the film into contact with cooling water.

In the method of the present invention, either an air-cooling method or a water-cooling method can be used, but the air-cooling method is preferable from the viewpoints of productivity, operability of the apparatus, ease of performing the subsequent corona discharge treatment, etc.
．． The most important molding conditions for inflation molding are: If the resin temperature is too high when the raw resin is melt-kneaded and extruded using an extruder, part of the resin will decompose, resulting in the formation of corona. In order to prevent damage from adhesion caused by discharge treatment, it is preferable not to perform molding at too high a temperature, but to extrude at a temperature of about 16θ to 23θC, and in the case of polypropylene, l≦O
A temperature of about -λ6θC, preferably l♂θ~23θC is desirable.

Normally, the blow ratio is preferably l-2, since the film may shrink during corona discharge treatment after blowing during inflation molding or when filling heated liquid foods, etc. is about 8~3, and the draft rate is t~100, preferably 10~! It is desirable to set it to about θ.

The cylindrical film obtained by inflation molding is flattened by pinch rolls provided at the top or bottom (in the case of a downward inflation molding umbrella). Next, a corona discharge treatment is performed, and it is desirable that the corona discharge treatment be performed immediately and continuously (in-line treatment) on the cylindrical film sent out from the inflation molding machine. If the inflation-molded film is once rolled up and then subjected to corona discharge treatment, especially if the raw resin is mixed with roughening etc.
This is because the additive may ooze out and the film may not adhere well even if corona discharge treatment is applied.

By subjecting the flattened cylindrical film to the corona radiation tJ6 treatment from the outer surface side, the cylindrical film will form a good dense layer on the inner surface side.

The reason for the close contact is not completely clear, but it is thought that the inner surface of the cylindrical film melts locally and instantaneously due to the heat generated by the corona discharge, causing a slight fusion state. .

The degree of treatment of corona discharge treatment depends on the treatment voltage, distance between electrode and film, film take-up speed, elapsed time from the time of film molding to application of corona discharge treatment, temperature and humidity conditions, type of raw resin, and additives in raw resin. It varies depending on the presence or absence of the film, its type, film thickness, etc. - cannot be determined generally, but usually,
When processing a film of high-density polyethylene or polypropylene that does not contain additives and has a thickness of about 20 to 10μ, preferably 30 to 30μ (thickness of one sheet), the outer surface of the film immediately after being subjected to corona discharge geography. Wetting tension (
J engineering 8-Kt7≦t-/based on 971) is 6t! dy
If it is n./sub or more, it can be obtained.

By applying corona discharge treatment while applying appropriate tension, the film adheres evenly.

In addition, by applying the corona discharge treatment, the film is in the same state as when it was heat-treated after molding, so it becomes a film with excellent dimensional stability. - The container is shaped into the desired shape using a cutter or the like.

The method of the present invention will be explained below with reference to Examples.
The present invention is not limited to the following nine embodiments as long as the gist of the present invention is not exceeded.

In addition, physical property measurements in Examples are as follows.

[Wetting tension]

, 67≦♂-7 for Tl8-71, apply the above reagent to the film surface with absorbent cotton using Wako Tsumugi Pharmaceutical @'s "Reagent for Wet Tension Test", and make sure that the reagent is on the film surface. The surface tension (dy
0 [degree of adhesion (degree of blocking)] expressed as n/cr11) from any position on the flattened cylindrical film /, 2
Cut out the am 2 by applying a pressure of 1097ad in an atmosphere of 0υ
4 for an hour, then remove the pressure.

- Leave in a constant temperature room at 〇〇 (relative humidity 40 degrees) for one hour. Both ends in the longitudinal direction of this test piece are peeled off at a width of 75 cm to obtain a test piece with an adhesion surface of /Ocm x /Ogq. The four films in the peeling section are each fixed to a chuck, and the chuck is moved in the direction of peeling the film at a moving speed of f Oam 1 minute, and the maximum strength at which the film is peeled off is UC1i/10.
0crl).

Example 1 'High equipment polyethylene (manufactured by Mitsubishi Chemical Industries, Ltd., Tsubachik IABJOO1M knee θ, Og, density = θ, ri ≦ O softening temperature [/ko lυ) f: Air-cooled inflation molding machine (manufactured by Modern Machinery Co., Ltd., KA - Resin temperature 2 at (40 type, 7! Cabinet φ spiral type guide, to die clearance - 1)
．． 20' (J, blow-up ratio 3.θ, frost line height OOW+, film take-up speed -〇rlL/min (
A film k having a draft rate/J) of 30 μm in thickness was molded.

The cylindrical film flattened with a vinyl roll was placed next to an inflation molding machine, and introduced into a corona discharge treatment apparatus for surface treatment.

Corona discharge treatment equipment (Kasuga Electric @IJjR%1 (IFε
-201 type, electrode length JOcm), the processing conditions are as follows:
The electrode-film distance was set to 0.7, and the processing voltage was set to 0 KV. The room temperature during treatment is 2. to, the relative humidity was 7j%.

Table 1 shows the physical properties of the adhesive film obtained.

Example 3 A close-tight film was produced in the same manner as in Example 1, except that the resin extrusion lid from the extruder was changed and the film take-up speed was 2/min and 30 m/min to form a film with a thickness of 30 μm. I got it. The physical properties of the resulting light-adhesive film are shown in Table 1.

Comparative Example 1 A film was obtained in the same manner as in Example 1 except that the corona discharge treatment was not performed.

Table 1 shows the physical properties of the obtained film.

Example Polypropylene (Mitsubishi Chemical Industries (Side Tsubachiku P3)
Evening 00'H', MF = 7, density = o, riθ, softening temperature lli! '0) T-Water-cooled inflation molding machine (manufactured by Kakuda Seisakusho, DTK-EIO type, screw diameter Owm)
φ, L/D ”' -24s die diameter 7rrmφ, die clearance/,,0.) Resin@fjf, 220
'0, Blow-up ratio 71 Cooling water temperature 2θC1 Frost line position, 200 wm (distance from die surface),
Film take-up speed/! A film with a thickness of 30 μm was molded at m/min.

The corona discharge treatment was carried out in the same manner as shown in Example 1.

Table 1 shows the physical properties of the adhesive film obtained.

Example! , while changing the amount of resin extruded from the extruder, the film take-up speed fft-2θ74/min 1.2! An adhesion film was obtained in the same manner as in Example G, except that a film having a thickness of 30 μm was formed at rn of 1 minute.The taking-up speed of the 0 film was changed, and the conditions for the cycorona discharge treatment were changed.

Table 1 shows the physical properties of the adhesive film obtained.

Comparative Example A film was obtained in the same manner as in the previous example except that the cocorona discharge treatment was not performed.

The physical properties of the obtained porous film are shown in Table #I1.

Table -/ Due to its good adhesion, if a container for automatic filling is manufactured and used, even if the nozzle of the automatic filling device is inserted into the customer device, excessive air will not enter the container. There is no problem, and filling is performed stably.

Furthermore, the film has been subjected to corona discharge treatment, so
Not only can printing etc. be performed well on the outer surface, but since heat is added to the film during corona discharge treatment, the film is stabilized against heat in the same way as heat-treated film, and it can be filled with high-temperature liquid. The film also has excellent dimensional stability, and the film does not shrink during heat sealing, providing advantages that are not found in various conventional films.

Applicant: Mitsubishi Chemical Industries, Ltd. Agent Patent Attorney Hase - (1 other person)

Claims (1)

[Scope of Claims] (1) A flattened cylindrical film obtained by inflation molding high-density polyethylene or polypropylene is subjected to corona discharge treatment from the outer surface side, so that the inner surface of the cylindrical film (2 2. The method for producing an adhesive film according to claim 1, wherein the corona discharge treatment is continuously performed on the cylindrical film fed out from the inflation molding machine. (3) The corona discharge treatment is performed so that the wetting tension on the outer surface of the cylindrical film immediately after the treatment is 41 j a7n·7cm or more. The method for producing the adhesive film described in Section 1.