JPH11188793A - Manufacture of embossed film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an embossed film for obtaining the film of a good molded state having a uniform thickness even at the time of rapid molding. SOLUTION: In the method for manufacturing an embossed film comprising the steps of extruding a thermoplastic resin in a film state from a lip 11 of a mold, and then sandwiching the extruded film-like extruded material 5 between an embossed roll 2 and a rubber roll 3 under pressure to transfer an embossed pattern of the roll 2 to a surface of the material 5; the material 5 is first brought into close contact with any one of the rolls 2 and 3 near the lip 11 of the roll 3, and then sandwiched between the embossed roll and the rubber roll under pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an embossed film.

[0002]

2. Description of the Related Art Thin embossed films of 200 μm or less are used for disposable diapers and sanitary napkins. This embossed film was manufactured by
As disclosed in No. 9628, after extruding a thermoplastic resin into a film from a lip of a mold,
In the nip portion formed by the embossing roll and the rubber roll, the extruded molten film extrudate is sandwiched between the embossing roll and the rubber roll, and the embossing pattern of the embossing roll is transferred to the surface of the film-like extrudate. Manufactured by the method.

However, the conventional manufacturing method described above has a problem that stability at the time of high-speed molding is poor. That is, about 1
When high-speed molding is performed at a line speed of 00 m / min or more, the thickness of the film-like extrudate in the air gap portion from the lip of the mold to the nip portion periodically fluctuates in both the vertical and horizontal directions ( Pulsation), a phenomenon called so-called draw resonance.

[0004] The mechanism by which the draw resonance occurs is not sufficiently clarified theoretically. However, when the draw resonance occurs, the thickness of the obtained embossed film becomes so large that it does not become a product. In addition, due to uneven thickness of the extruded film at the air gap, the extruded film is torn from the thin part, or the thick part is insufficiently cooled and wrapped around the embossing roll or rubber roll. Or

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides a method of manufacturing an embossed film capable of obtaining an embossed film having a uniform thickness and a good molded state even during high-speed molding. It is an object.

[0006]

In order to achieve such an object, a method for producing an embossed film according to the present invention comprises extruding a thermoplastic resin from a mold lip into a film and extruding the resin. In a method for producing an embossed film in which a film-like extruded product is pressed between an embossing roll and a rubber roll to transfer an embossed pattern of the embossing roll to the surface, the film-like extruded product is near the lip of a mold, the embossed roll and First, it was brought into close contact with either one of the rubber rolls, and then pressed between the embossing roll and the rubber roll.

[0007] As the method for extruding a film-like extrudate in the present invention, a usual T-die method is used. Examples of the thermoplastic resin used in the present invention include, but are not particularly limited to, polyethylene, polypropylene, polyvinyl chloride, polyamide (nylon), polyester and the like. Single or a mixture of high-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, etc.).

[0008] The embossing roll is not particularly limited, but usually a metal-made embossing roll is used. The method for first bringing the film-like extrudate into close contact with the surface of the embossing roll or rubber roll is not particularly limited, for example,
A method in which air is blown onto the surface of a film-like extrudate and the film-like extrudate is pressed in the direction of an embossing roll or a rubber roll by air pressure, and a method in which the surface of the film-like extrudate is attracted to the embossing roll or a rubber roll by suction. And the like.

As a method of pushing with air pressure, a method using an air knife and an air chamber can be mentioned. The air knife blows air with a predetermined width from a narrow slit provided at the tip.

The air chamber is provided with a pressure equalizing chamber inside, and a large number of air blowing holes communicating with the pressure equalizing chamber are provided on the surface, and air is blown out from each of the blowing holes at a uniform pressure. Say things. When an air chamber is used, the air pressure in the pressure equalizing chamber
It is preferable to increase the height by about 0 to 300 mmaq (water column).

[0011] That is, if it is less than 30 mmaq, the adhesion of the film to the roll is insufficient, and if it exceeds 300 mmaq, it becomes difficult to maintain the pressure equalized state of the pressure equalizing chamber of the air chamber, and irregularities are generated from the air chamber. The leaking air causes the extruded film to vibrate or the adhesion of the extruded film to the roll becomes unstable.

On the other hand, as a method of attracting a film-like extrudate, for example, a method using a vacuum chamber, an electrostatic pinning method or the like can be mentioned. In the vacuum chamber, the inside of the chamber is depressurized, and the film-like extrudate is sucked from the suction hole of the chamber, contrary to the air chamber. In the method using a vacuum chamber, it is preferable that the pressure in the chamber be lower than the atmospheric pressure by about 30 to 300 mmaq.

That is, if the difference from the atmospheric pressure is smaller than 30 mmaq, the film is not sufficiently adhered to the roll,
If it exceeds mmaq, it will be difficult to maintain the pressure equalized state in the pressure equalizing chamber, and the adhesion of the film-shaped extrudate to the roll will be unstable.

The method using the electrostatic pinning method means that a high DC voltage is applied between a metal embossing roll and a pinning electrode such as a needle electrode or a wire electrode arranged so as to face the metal embossing roll. This is a method in which a film-like extrudate is forcibly charged by applying a voltage, and the film-like extrudate is brought into close contact with a grounded metal embossing roll by static electricity.

When the electrostatic pinning method is used, the voltage applied to the pinning electrode is not particularly limited, but is 5 kV to 5 kV.
20 kV is preferred. That is, when the voltage is lower than 5 kV, the film is insufficiently adhered to the metal embossing roll, and when the voltage exceeds 20 kV, a spark discharge easily occurs from the pinning electrode toward the ground of the metal embossing roll or the electrode support. In addition, the applied voltage may not be stable, and the adhesion of the film-shaped extrudate to the metal embossing roll may not be stable. The polarity of the pinning electrode may be positive or negative.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
The details will be described with reference to the drawings. FIG. 1 shows an embodiment of a method for producing an embossed film according to the present invention.

As shown in FIG. 1, in this manufacturing method, a nip portion 4 composed of a metal embossing roll 2 and a rubber roll 3 is provided below the mold 1, and a lip 1 of the mold 1 is provided.
The extrudate 5 extruded from the nip 1 is pinched between the metal embossing roll 2 and the rubber roll 3 at the nip portion 4, and a pinning electrode is provided between the mold 1 and the nip portion 4. 6, a DC voltage is applied to the pinning electrode 6 to positively charge the extrudate 5 in a film form.

That is, the film-like extrudate 5 extruded from the lip 11 repels the pinning electrode 6 to which positive electricity is applied, and is sucked by the grounded embossing roll 2 and firstly adsorbed on the embossing roll 2. In this state, the emboss pattern advances to the nip portion 4 and is nipped between the rubber roll 3 and the emboss pattern of the emboss roll 2 is transferred.

In this manufacturing method, as described above, first, the extruded film 5 extruded from the lip 11 adheres to the surface of the embossing roll 2 near the lip by using the electrostatic pinning method. The length of the portion (hereinafter referred to as “air gap length”) is shorter than the air gap length of the conventional manufacturing method. further,
Since the film width is regulated at the same time when the film is in contact with the embossing roll, the deformation in the air gap portion is stabilized. That is, the film-shaped extruded product 5 in the air gap portion can be suppressed from periodically fluctuating (pulsating) in both the vertical and horizontal directions.

Further, as the air gap length becomes shorter, the variation in the amount of deformation at the time of drawdown also becomes smaller. It is considered that this is because the deformation ends in a short section, and the fluctuation of the deformation amount or the tension is hard to propagate.
Therefore, it is possible to produce the embossed film 7 which has good high-speed moldability, does not cause draw resonance, has a uniform thickness, and is in a good molded state.

FIG. 2 shows another embodiment of the method for producing an embossed film according to the present invention. As shown in FIG. 2, in this manufacturing method, instead of using the electrostatic pinning method, a vacuum chamber 8 is provided on the rubber roll 3 side, and the extruded film-like extruded material is first brought into close contact with the rubber roll 3 side by suction. It is the same as the manufacturing method of FIG. 1 except that the nip portion 4 is pressed between the embossing roll 2 and the rubber roll 3.

FIG. 3 shows another embodiment of the method for producing an embossed film according to the present invention. As shown in FIG. 3, in this manufacturing method, an air knife 9a is provided instead of the vacuum chamber 8, and the air knife 9a is provided.
First, the film-like extrudate 5 extruded by the air blown out from a is brought into close contact with the embossing roll 2 side.
In the nip portion 4, pressure was applied between the embossing roll 2 and the rubber roll 3. In addition, the manufacturing method of FIG.
The vertical relationship between the embossing roll 2 and the rubber roll 3 is reversed.

FIG. 4 shows another embodiment of the method for producing an embossed film according to the present invention. As shown in FIG. 4, in this manufacturing method, an air chamber 9b is provided instead of the vacuum chamber 8, and the extruded film 5 extruded by the air blown from the air chamber 9b is first brought into close contact with the embossing roll 2 side. After that, the nip portion 4 was pressed between the embossing roll 2 and the rubber roll 3. The vertical relationship between the embossing roll 2 and the rubber roll 3 is opposite to that of the manufacturing method of FIG.

[0024]

Embodiments of the present invention will be described below in more detail.

(Example 1) As shown in FIG. 5, an apparatus using an electrostatic pinning method similar to the apparatus shown in FIG. 1 using a wire electrode 6a as a pinning electrode was prepared.
(Melt flow rate) A blend of 2.0 parts by weight of low-density polyethylene having a density of 0.92 and 4 parts by weight of calcium carbonate having an average particle size of 10 μm was extruded using a 115 mmφ extruder and a T-die having a lip width of 1000 mm. Extruded into a film, + 12k between wire electrode 6a and embossing roll
v, a film-like extrudate was first brought into close contact with the metal embossing roll 2 and then pressed between the embossing roll 2 and the rubber roll 3 at a line speed of 250 m / min.
To obtain an embossed film having a product effective width of 850 mm and an average thickness of 25 μm. The air gap length at this time is 6
It was 0 mm. The thickness of the obtained embossed film was measured at 1 cm intervals in the width direction and at 1 m intervals in the length direction over 10 m. As a result, the variation (range) in the width direction was 2.
1 μm, variation (range) in the length direction is 1.8 μm on average
m. The resulting film had a matte surface and a soft feel, and was suitable as a sanitary film such as a disposable diaper or a sanitary napkin.

Example 2 As shown in FIG. 6, an apparatus using an electrostatic pinning method similar to the apparatus shown in FIG. 1 using a needle-like electrode 6b as a pinning electrode was prepared, and the MFR (melt flow rate) was obtained. 4.0, 100 parts by weight of linear low-density polyethylene having a density of 0.94 and 4 parts by weight of calcium carbonate having an average particle size of 10 μm are formed into a film by using an extruder having a diameter of 115 mm and a T-die having a lip width of 1000 mm. Extruded, +12 kv between needle electrode 6 b and embossing roll 2
, The film-shaped extrudate is first brought into close contact with the metal embossing roll 2, then sandwiched between the embossing roll 2 and the rubber roll 3, taken up at a line speed of 250 m / min, the product effective width 800 mm, average An embossed film having a thickness of 25 μm was obtained. The air gap length at this time is 60
mm. The thickness of the obtained embossed film was measured at 1 cm intervals in the width direction and 10 m at 1 m intervals in the length direction. As a result, the variation (range) in the width direction was 2.4 on average.
μm, variation (range) in the length direction is 2.0 μm on average
Met. The resulting film had a matte surface and a soft feel, and was suitable as a sanitary film such as a disposable diaper or a sanitary napkin. (Example 3) A mixture of 100 parts by weight of a linear low-density polyethylene having an MRF of 2.0 and a density of 0.935 and 4 parts by weight of calcium carbonate having an average particle diameter of 10 µm was extruded into a 115 mmφ extruder.
After extruding into a film using a T-die having a lip width of 1000 mm, the extruded film is brought into close contact with the rubber roll 3 using a vacuum chamber (internal pressure is reduced to 150 mmaq with respect to the atmospheric pressure) 8 as shown in FIG. , Between the embossing roll 2 and the rubber roll 3,
The film was taken at a speed of 00 m / min to obtain an embossed film having an effective width of 820 mm and an average thickness of 25 μm. The air gap length at this time was 70 mm. The thickness of the obtained film was measured at intervals of 1 cm in the width direction and at intervals of 1 m in the length direction over 10 m.
m, the variation in the length direction was 2.2 μm on average.
The resulting film had a good matte surface and a soft feel, and was suitable as a sanitary film.

(Comparative Example 1) A film-like extrudate extruded from a mold was pressed directly at a nip portion where an embossing roll and a rubber roll were arranged so that an air gap length was 200 mm, in the same manner as in Example 1. When the embossed film was manufactured by using the method, the extrudate was easily wound around the rubber roll, and the extrudate was frequently cut, so that a product could not be obtained stably.

(Comparative Example 2) A film-like extrudate extruded from a mold was directly pressed at a nip portion where an embossing roll and a rubber roll were arranged so as to have an air gap length of 200 mm, and was pulled at a line speed of 100 m / min. Except that the effective width of the product was 800 in the same manner as in Example 1.
mm, an embossed film having an average thickness of 25 μm was obtained. The thickness of the obtained embossed film was measured at intervals of 1 cm in the width direction and 10 m at intervals of 1 m in the length direction. As a result, the maximum value of the thickness was 45 μm, the minimum value was 16 μm, and the variation in the width direction was 23 μm on average, and the thickness in the length direction was 23 μm. Variation is 15μ on average
m.

Further, the obtained embossed film has a large thickness variation, so that the thick portion is hard, the thin portion is soft and easily torn, and the appearance is matte only in the thick portion and glossy and translucent in the thin portion. there were. That is,
It could not be used as a sanitary film.

[0030]

Since the method for producing an embossed film according to the present invention is constituted as described above, it is possible to obtain an embossed film having a uniform thickness and a good molded state even during high-speed molding.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing one example of a production apparatus used for a method for producing an embossed film according to the present invention.

FIG. 2 is a schematic view schematically showing another example of the manufacturing apparatus used in the method for manufacturing an embossed film according to the present invention.

FIG. 3 is a schematic diagram schematically showing another example of the manufacturing apparatus used in the method for manufacturing an embossed film according to the present invention.

FIG. 4 is a schematic view schematically showing another example of the production apparatus used in the method for producing an embossed film according to the present invention.

FIG. 5 is a perspective view schematically showing an apparatus using the electrostatic pinning method used in Example 1.

FIG. 6 is a perspective view schematically showing an apparatus using an electrostatic pinning method used in Example 2.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold 11 lip 2 emboss roll 3 rubber roll 4 nip 5 film extrudate 7 emboss film

Claims (1)

[Claims] 1. After extruding a thermoplastic resin into a film from a lip of a mold, the extruded film-like extrudate is sandwiched between an embossing roll and a rubber roll to transfer the embossing pattern of the embossing roll to the surface. In the method for producing an embossed film, the film-shaped extruded material is first brought into close contact with one of the embossed roll and the rubber roll in the vicinity of the lip of the mold, and then pressed between the embossed roll and the rubber roll. Method for producing an embossed film.