JPH09109253A - Manufacture of inflation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to accelerate, and to perform the high quality, resource conservation and energy conservation by pressurizing and sealing the air in a thermoplastic synthetic resin tubular body melted and extruded from an annular die, then folding the body, pressurizing it by pinch rolls, and solidifying it in a film state. SOLUTION: The air 9 is blown into a thermoplastic synthetic resin tubular body melted and extruded from an annular die 3, the body is expanded to a predetermined size, and then when the resin for forming the body (a bubble 4) is lowered to the temperature in a predetermined range, the expanded bubble 4 is folded, and pressurized by pinch rolls 6. The two films are thermally fusion- bonded (m) at the inner surfaces (a) to one another to one film. At the time point of press-bonding it by the rolls 6, the inner surface temperature of the resin for forming the bubble 4 is held at the temperature for thermally fusion bonding the inner surfaces to orie another. This apparatus can be set at its total height to a low value, and cooling of the bubble is sarely necessary, and hence its operation can be accelerated at its speeded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing various films mainly used for flexible packages, and more particularly to a film forming method having a stable quality and high productivity.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view showing a conventional inflation film forming method. The film-forming method by the air-cooling inflation method uses a die 3 having an annular slit at the tip of an extruder 1, extruding a molten resin to form a tubular body, and pinching the upper end with a pinch roll 6 to form a tubular body. A certain amount of air 9 is blown in to expand it to a predetermined size (the expanded tubular body is referred to as a bubble, hereinafter the same), while the bubble 4
A film is formed by blowing air 9'from the air ring 10 onto the outer periphery of the film while cooling. At this time, the diameter of the bubble 4 can be changed by adjusting the amount of air blown into the bubble, and the thickness of the obtained film can be changed by changing the pulling speed while keeping the extrusion amount constant.

The inflation film forming method has many characteristics as compared with other film forming methods. For example, in the film formation by the T die casting method, a linear die having a length equal to or larger than the required film finishing width is required, and the thickness is adjusted by adjusting the die lip clearance and adjusting the take-up speed. When changing the thickness in production, it takes time and effort to adjust the die lip. In the inflation method, as described above, the thickness adjustment is easy by changing the conditions of the blow ratio and the take-up speed, and in the production activity, the standard change is relatively easy, which is suitable for small lot production. In the inflation method,
Since the amount of air blown in can be adjusted, the range of width that can be produced by the same die is wide. On the other hand, in the film formation by the inflation method, the film formation speed is slow, the productivity is poor, and the bubble is unstable, so it takes time to adjust it, and the bubble is formed stably even during the film formation. There are also problems such as the need to pay attention to.

In the inflation film forming method, the bubbles 4 are sufficiently cooled by an air ring 10 or the like so that the inner surfaces of the bubbles do not block each other, the bubbles are folded by a stabilizer 5 and then folded by a pinch roll 6. As a folding tube, it was wound up as it was, or several mm at each end of the tube was removed, and the folded film was separated and wound up into two pieces 7 and 7 '. In order to wind the formed film into two single films, the removed films at both ends are fed back to the raw material hopper of the film forming machine again, or in another machine, the raw material (repro raw material) is re-used. Used as). In any case, it was necessary to reheat, which was not preferable from the viewpoint of energy consumption.

If the bubbles are not cooled sufficiently, the inner surfaces of the bubbles folded by the pinch roll will be in contact with each other to cause blocking, which inevitably keeps the bubble state for a long time and saves space as a device. It was supposed to be taken.

[0006]

(EN) Provided is a blown film manufacturing technique capable of speeding up a film forming process, that is, having excellent productivity, good quality, resource saving and energy saving.

[0007]

In the inflation method, air 9 is blown into a thermoplastic synthetic resin tubular body melt-extruded from an annular die 3 to expand the tubular body to a certain size and form a bubble, The bubble 4 is forcibly folded, and within the temperature range in which the thermoplastic synthetic resin forming the bubble can be heat-sealed by pressure, it is pressed by a pinch roll to be solidified into a single film, or Alternatively, the tubular body is a film forming method in which a film having a multilayer structure of resins extruded from at least two extruders is solidified into a single film by the above method, further comprising: A method for producing an inflation film, which comprises a pinch roll having a matte surface.

[0008]

1 is an explanatory view showing a method for producing an inflation film according to the present invention, and FIG.
Shows a state in which bubbles are folded according to the present invention and solidified into a single film in a stepwise manner in the cross section of each of a single-layer bubble and a multi-layer bubble, and (5) shows the X part of (4). FIG. The inflation film production method of the present invention is an inflation method, in which air 9 is blown into a thermoplastic synthetic resin tubular body melt-extruded from an annular die 3 to expand the tubular body to a certain size, and then the tubular body is expanded. When the thermoplastic synthetic resin forming the body (hereinafter referred to as the bubble 4) is cooled to a temperature within a certain range, the expanded bubble 4 is forcibly folded and solidified into a single film. The present invention is also a method for producing a blown film, and can be applied to a so-called coextrusion multilayer film in which the tubular body has a multilayer structure of resins extruded from at least two extruders.

In the present invention, when the temperature (inner surface temperature) of the bubble 4 falls within a certain range, the bubble 4 is folded and pressurized by the pinch roll 6,
Two sheets of film with a bubble folded inside
Then, the film is heat-sealed to form a single film. The stage where the temperature drop of the bubble falls to a certain temperature range,
In other words, at the time of pressing by the pinch roll 6, the temperature of the thermoplastic resin forming the bubble 4, in particular the inner surface temperature thereof, is maintained by the pressure of the pinch roll 6 so that the inner surfaces are heat-sealed. It is necessary to. In addition, air,
Cooling with water etc. is possible. The required temperature depends on the type of material placed on the inner surface of the bubble and its grade, and among various commercially available resins, the resin temperature range necessary for carrying out the present invention is as follows. LDPE: 120 to 60 ° C L-LDPE: 120 to 60 ° C EVA: 120 to 50 ° C S-PE: 120 to 50 ° C In the practice of the present invention, at least the bubble 4 held at this temperature or higher is pinch roll. It is necessary to crimp by 6. {The abbreviation is LDPE: low density polyethylene,
L-LDPE: linear low-density polyethylene, EVA: ethylene-vinyl acetate copolymer, S-PE: ethylene-α / olefin copolymer polymerized using a single-site catalyst}

In the present invention, the film may be formed by a single-layer bubble, but it may be formed by a multi-layer bubble. For example, when forming a film with a multi-layer structure of two layers of bubbles, b for the outer layer and c for the inner layer, stable film formation is possible by selecting a resin c with a low heat fusion temperature on the inner surface of the bubble. Becomes For example, LDPE / AD / EVOH (i) L-LDPE / EVA (ii). {Abbreviation is AD: adhesive resin layer} (ii),
L-LDPE is the outer layer b and EVA is the inner layer c. In order to stably maintain the temperature for heat fusion, it is effective to heat the pinch roll (by circulating a heat medium in the pinch roll) or to continuously provide the heated pinch roll. It is also possible to support by film forming conditions such as heating the air blown inside. Further, after heat fusion, it can be cooled with air or water.

By making two films into one,
Residual strain existing locally is reduced, and a stable film can be obtained. For example, forming a bubble of a multilayer film having a barrier resin (EVOH) such as the above (i) on the inner surface,
According to the method of the present invention, a stable composite film (LDPE / AD / EVOH / EVOH) without curl or wrinkle as a film generated by the conventional method is obtained by forming a single film by heat fusion on the EVOH surface. / AD / LDPE (the point is the pressure-bonded surface, the same applies below).
For materials, such as EVOH, whose physical properties change due to water absorption when left in the air, the ends can be covered with other materials, so for example, there is no deterioration during storage by winding and in terms of quality. Is also effective. In the case of the configuration (i), the end portion of EVOH is covered with the layer of LDPE / AD. Furthermore, the film formed according to the present invention has very few pinholes. With the method of the present invention in which even two very small pinholes existing in a bubble state are heat-sealed to each other, the number of pinholes penetrating the film is as close as possible to zero, and in fact, leak check No pinhole was found in the confirmation by a car or the like.

In contrast to the conventional film forming machine, in the case of the film forming method according to the present invention, the distance from the annular die to the pinch roll is shortened to avoid excessive temperature drop of bubbles. The device has the advantage that the total height above and below the device can be set low regardless of whether it is facing up or down. The productivity of the film formation according to the present invention is the same as that of the prior art if the amount of resin extruded from the extruder is constant. Can be speeded up (it will increase the extrusion amount), but using LDPE,
A film with a thickness of 40 μm and a finished width of 800 mm was formed,
The film forming speed is 5 times faster than the conventional speed (8m / min. → 40m /
It was possible to form a film at (min.). That is, the production amount was 5 times that of the conventional method.

In the conventional method, two sets of winding devices (two corona treatment devices t when the surface treatment is performed on the film) are required to roll the film as a flat film at the same time as the film formation. However, according to the present invention, only one set of the winding device is required, and when the corona-treated surface treatment is performed, only one treating device t is required.

In the film forming method of the present invention, the bubble blown up can be folded and used as a single film as it is. Therefore, if the bubble is folded by the guide plate in a stable state, the film pressed by the pinch roll is folded. The width of the film can be used as is as the finishing width. INDUSTRIAL APPLICABILITY The present invention is a resource-saving and energy-saving film manufacturing method that does not require removal of both ends of a film formed as in the conventional T-die casting method or inflation method.

In the flexible package, a physical property required for a film used as a sealant material (seal layer) is slipperiness of the film surface (which is an inner surface of a laminated film). Other film forming methods such as T die casting method and extrusion coating method (EC method)
In such a case, there is a cooling roll just below the die, and if the surface of the cooling roll is matte (rough surface), the molten resin will
The matte state of the surface of the cooling roll is transferred to the surface of the obtained film, and as a result, a film having good slipperiness can be obtained. However, in the case of film formation by the conventional inflation method, the molten resin extruded from the die does not come into contact with the mat surface like the T die cast method or the EC method between the die and the pinch roll. It was difficult to provide unevenness on the surface of the film. Although various methods have been proposed for the roughening technique of the film surface at the stage of inflation film formation,
It is no exaggeration to say that there is no popular technology. As a measure against slip, the technology used is slip agent,
Add an anti-blocking agent, etc. to the resin as an additive,
The surface properties are improved. However, the influence of odor etc. due to additives shifting to contents that emphasize taste,
Depending on seasonal factors and the storage period as a film,
There is also a problem such as bleed-out of the additive (a phenomenon in which the film surface is boiled out from inside the film layer).

In the conventional inflation film formation,
After cooling the bubble temperature to a certain temperature, fold it into a flat shape with a stabilizer, and with a pinch roll,
It is difficult to form unevenness on the surface of the film at the stage of pressure-bonding, melt-extruding the resin from the annular die to form bubbles, and blowing air into the bubbles to expand. . Further, even if the bubble is cooled and then pressurized by the pinch roll as described above, the resin forming the bubble is cooled and cannot be plastically deformed. According to the present invention, in the step of folding the bubble, since the resin forming the bubble maintains a temperature at which it can be plastically deformed, the surface of the pinch roll is matted, and the film is pressed, The matt shape of the pinch roll will be applied to the film surface, and as a result, the resulting film will have a surface with good slipperiness, preventing wrinkles during roll winding and various formers (forming parts) in packaging machines. It is a material that slides well on machines and is easy to use. The matt state of the pinch roll surface and the degree of matte of the obtained film surface were as follows. In each case,
The surface irregularities were measured by a three-dimensional surface roughness / contour shape measuring machine (manufactured by Nippon Denki Co., Ltd.). In this method, the surface of an object is three-dimensionally measured by a direct contact needle method. Pinch roll surface roughness Unevenness on the obtained film surface 10 μm 1 to 3 μm 50 μm 3 to 10 μm 100 μm 5 to 20 μm

In the present invention based on the multi-layer bubble system, the following film can be prepared by forming a film by combining a surface layer and a core layer. <Surface layer><Corelayer><Filmcharacteristics> Inorganic substance-containing NB / PE EO film Mat film NB / PE EVOH / a-PE Barrier film S-PE a-PE / MDPE Sealant for paper container Antibacterial agent / PE NB / PE Antibacterial film {symbol, NB / PE: non-blend polyethylene, EO: easy open, a-PE: adhesive polyethylene, MDPE: medium density polyethylene}

As described above, the structure of the multilayer film obtained by the present invention is as follows:
Various possibilities such as modification of the surface layer having a layer containing additives such as antistatic agents, decoration by providing a coloring material addition layer, roughening by forming a surface layer with a kneading resin of an inorganic compound, etc. It includes sex.

[Example 1] By the method of the present invention, L-LDPE
The resin was formed into a film, and the film forming conditions are as follows. Resin used: L-LDPE M0238N (manufactured by Idemitsu Petrochemical Co., Ltd.) Final target film thickness: 50 μm Final target film width: 1000 mm Extrusion temperature: 200 ° C Annular die: 300 φ Blow ratio: 2.1 Pulling speed: 80 m / min . Bubble inner surface temperature during pinch roll press bonding: 95 ° C. Pinch roll surface unevenness: 100 μm [Comparative Example 1] The film forming conditions for obtaining a film having the same thickness and width as the final product of Example 1 and the resin are as follows. On the street. Resin used: L-LDPE M0238N (manufactured by Idemitsu Petrochemical Co., Ltd.) Final target film thickness: 50 μm Final target film width: 1000 mm Extrusion temperature: 200 ° C Annular die: 300 φ Blow ratio: 2.1 Take-off speed: 20 m / min Pinch roll surface unevenness: 100 μm (Result) The take-up speed of the example was 80 m / min., And the comparative example was 20 m / min. The productivity is double. The same 100 μm uneven pinch roll as in the example was used.
The unevenness of the film obtained in each example is 10 to 20 μm in the examples, and the effect of sufficiently exhibiting the slipperiness required as a packaging material can be expected, whereas it is 0 to 2 μm in the comparative examples. However, there was no effect of imprinting unevenness.
In addition, in the examples, the film width heat-sealed in the pinch roll was the product width (1000 mm) as it was. But,
In the comparative example, the width when the bubble is folded and sandwiched by the pinch rolls is 1060 mm, and it is necessary to make it wider than the width of the present invention by 60 mm as the trimming width at both ends. , Returned to the raw material hopper. [Example 2] As an example of the multilayer bubble according to the present invention, a film was formed under the following conditions. Material composition: LDPE / AD / EVOH ・ EVOH / AD / LDPE (The final thickness is 75 μm, and the thickness of each layer is 20/10/15/10/2
It was 0 μm. ) Extruder and multilayer die: 3 types, 3 layers coextrusion method Product film thickness: 75 μm Extrusion temperature 220 ℃ Annular die 300 φ Blow ratio 1.7 Pulling speed 80 m / min. Pinch roll surface irregularities 50 μm Bubble inner surface when pinch roll is pressed Temperature 120 ° C Used resin name LDPE: NUC 8160 (Nippon Unicar Co., Ltd. product name) AD: Admer NF-500 (Mitsui Petrochemical Industry Co., Ltd.
Trade name) EVOH: EP-H (trade name, manufactured by Kuraray Co., Ltd.) [Comparative Example 2] The following film structure having the same function as the film obtained in Example 1 was prepared. LDPE / AD / EVOH / AD / LDPE (The thickness of each layer after winding is 20
/ 10/15/10 / 20μm) Extruder and multilayer die: 3 types, 5 layers coextrusion method Product film thickness: 75μm Extrusion temperature ooo ℃ Annular die 300 φ Blow ratio 1.7 Pulling speed 20m / min. Pinch roll surface irregularities 50μm Resin name used LDPE: NUC 8160 (trade name of Nippon Unicar Co., Ltd.) AD: Admer NF-500 (Mitsui Petrochemical Industry Co., Ltd.
Trade name) EVOH: EP-H (trade name, manufactured by Kuraray Co., Ltd.) (Result) In Comparative Example 2, it is necessary to use a complex die of 3 types and 5 layers. For comparison of productivity, take-off speed is
In the comparative example, it was 20 m / min. Regarding the film productivity, the productivity of Example 2 according to the present invention was twice that of the conventional method (Comparative Example 2). Further, as a result of film formation, the finished film had no curl and was finished as an easy-to-use film, but the curl phenomenon was observed in the comparative example. In both Example 2 and Comparative Example 2, a pinch roll having a matte surface having an unevenness of 50 μm was used. The surface of the obtained film could be imprinted with an unevenness of 5 to 10 μm in the Example. The film of Example 2 has no unevenness, and the slipperiness of both films is as a coefficient of static friction.
Example 2: 0.34, Comparative example 2: 0.46.

[0020]

As compared with the conventional inflation film-forming method, it is possible to obtain a film of stable quality, which has high-speed film-forming property, no curl, and no pinhole. In the film forming process according to the prior art, when winding the flat film, it was necessary to trim both ends, but according to the present invention, all the resin extruded from the annular die becomes a product, which is different from the conventional method. In addition, since it can be used as a film without trimming and removing both ends, it is a wasteless and environment-friendly film forming method. The cooling process is shortened, energy is saved, the film formation speed is increased, and the machine can be made compact. It is possible to provide fine irregularities on the film surface, and it is possible to manufacture a film having good slipperiness without using an additive such as a lubricant although it is an inflation film.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a film forming machine according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a film obtained by the present invention.

FIG. 3 is an explanatory view of a conventional inflation-type film forming machine.

[Explanation of symbols]

 1 Extruder 2 Raw Material Resin Hopper 3 Die (Die) 4 Bubble 5 Guide Plate 6 Pinch Roll (Heating Roll) 7 Annealing Roll (Cooling Roll) 8 Winding Part 9 9'Air, Cooling Air 10 Air Ring a Resin a b Resin b c resin cm heat-sealed part t corona discharge / surface treatment device

Claims (3)

[Claims] 1. In the inflation method, air is pressurized and sealed in a plastic synthetic resin tubular body melt-extruded from an annular die to expand the tubular body to a predetermined size,
By the pressurization of the thermoplastic synthetic resin forming the tubular body, within the temperature range in which the inner surfaces can be heat-sealed,
A method for producing an insulation film, characterized in that the expanded tubular body is forcibly folded and pressed by a pinch roll to be solidified into a single film. 2. The method for producing an inflation film according to claim 1, wherein the tubular body has a multi-layer structure of resins extruded from at least two extruders. 3. The method for producing an inflation film according to claim 1, wherein the pinch roll has a matte surface.