JPS5837893B2 - Kanjiyou film no seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a tubular film by an air-cooled inflation method. More specifically, the present invention relates to a method for manufacturing a tubular film using an air-cooled inflation method. The present invention relates to a method for manufacturing a tubular film that reduces the difference in mechanical properties between the film and the perpendicular direction.

In the conventional air-cooling inflation method for manufacturing tubular films, the mechanical properties in the longitudinal and transverse directions, such as tensile strength, tensile elongation, tensile impact strength, and tear strength, are different.
Since the strength in the transverse direction is weak, the film has the disadvantage of being easily torn in the longitudinal direction.

Known methods for improving these drawbacks include increasing the resin extrusion temperature, increasing the solidification position, increasing the expansion ratio, or a combination of these methods to produce a film. Ta.

However, when forming a tubular film using this manufacturing method, the forming stability is significantly impaired, and it is extremely difficult to obtain a film with uniform thickness during folding.

Furthermore, as a method to solve the above-mentioned drawbacks,
As seen in No. 252, by specifying the resin extrusion temperature and the ratio of the resin extrusion speed to the withdrawal speed, the valve is made to have a constriction, and an internal mandrel with a diameter smaller than the diameter of the die is installed above the die. However, although stability in the shape of a wedge is sought by bringing the constriction section into contact with the surface of the internal mandrel, such a method cannot prevent the following drawbacks.

■) There are restrictions on the resin in order to create a constricted part.

That is, the MI of the resin used must be low.

2) In order to uniformly contact the six constricted sections in the inner circumferential direction of the bubble with the internal mandrel, a very sophisticated technique is required and it is extremely difficult to operate.

Furthermore, it is better not to use an internal mandle for air-cooled inflation models for the following reasons.

(a) Since the inner mandrel and the bubble come into contact, bubble breakage is likely to occur depending on the type of raw material resin used, resulting in poor shapeability and operability.

(D) Cause of (A) (Flaws are likely to occur on the inside of the product film formed from this material, which may reduce the product value.

Q.) High-speed cutting performance is worse than cause 6 of (a).

The present invention solves the above-mentioned drawbacks, and the M of the resin used is
The I range is also wide <0.01~5. (Bi'/10 min), does not require the use of an internal mandrel, and provides a method for producing a film with well-balanced mechanical properties in the vertical and horizontal directions.

That is, in the present invention, when polyethylene is formed into a film by the air-cooled inflation method, a die cap of 150 to 230
Polyethylene is melt-extruded into a tubular shape within a temperature range of 150°C, the tubular bubble is placed in a constricted state with a diameter smaller than the diameter of the die just before expansion, and then the solidified position is 150 degrees or more and the expansion is 2.0 degrees or more. Surprisingly, the method of the present invention solves all of the above-mentioned drawbacks.

In other words, using an annular die of 1.5 mm or more for air-cooled inflation will reduce the resin kneading effect, make it difficult to control the thickness of the product film, or, fatally, cause the lateral direction of the film to deteriorate. Conventionally, it was not worth considering because it could not produce a stretching effect, but as a result of intensive research, it was found that the stretching effect was 1.5 to 5. Q
Polyethylene is extruded at a melting temperature of 150 to 230'C using an annular die with a die gap of mm, and the polyethylene is extruded at a melting temperature of 150 to 230'C, and immediately before expansion into a bubble shape (solidification position is 150'IIL7IL or more in a prone state with a constriction, the expansion ratio is 2 .0 or higher (this makes it possible to use polyethylene with a wide MI range as a raw material, and to produce a strong film with well-balanced mechanical strength in the longitudinal and transverse directions without compromising molding stability). Moreover, the film thickness can be adjusted freely by adjusting the resin extrusion amount and film take-up speed (5
〜lOOμ)//We have created a method for manufacturing a tube-shaped film that can be shaped.

Furthermore, the effects of the present invention are most evident when producing thin films with a thickness of 30 μm or less.

To explain the present invention in detail with reference to the drawings, FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a conventional 0.5
A circular die with ~1.0 mounds was used.

The present invention is based on 1.5 to 5. Polyethylene is extruded at a melting temperature of 150 to 2300C using an annular die of Omru, and a constriction part M is formed just before expansion of the bubble shape, and this constriction part M is made to meet the above conditions. It is forced to occur.

Furthermore, by using a 6-bubble stabilizer after the bubble solidification position to suppress the forced 6-bubble, it is possible to more easily create a constriction.The bubble stabilizer is designed to suppress bubbles from all sides of the bubble. It may be a flat plate, or it may be something that suppresses the entire circumference of the bubble, not just the 46,000 points of the bubble.

Furthermore, as an effect of using the valve stabilizer, the solidification position can also be adjusted in addition to the above.

On the other hand, the die gap was conventionally used, 0.5~LO
If air-cooled inflation molding is performed using a mm die, no matter what MI resin is used, the shape will be as shown in FIG. 2, and the constriction will be 6 mm.

Even if the constriction is forcibly generated by setting conditions such as film take-up speed, resin extrusion speed, frost line, etc., the bubble itself will not be stabilized and the film will suffer from uneven thickness, wrinkles, walnuts, and fold diameter. Since problems such as fluctuations are large and it cannot be put to practical use, it is necessary to install an internal six-piece mandrel or the like to stabilize the bubble.

In the present invention, the raw material polyethylene has an MI range of 0.01 to 5.
Even at 0 g/to minute ζ, no internal mandrel is used during molding, and the bubble becomes unstable C1.

The reason for this is that the die gap is 1.5 to 5. 0 7n
Since a die of 1 L is used, the thickness of the bubble in the section N where the resin is extruded from the die and reaches the constriction M is larger than that using a conventional die, so stability is ensured.

Therefore, there is no need to install a mandrel inside.

However, in the present invention, even if an internal ζ-shaped mandrel is used in combination, there is no problem in achieving the effects of the present invention.

Furthermore, if we consider the linear velocity between the constriction M and the section N leading to the constriction in the present invention, it is clear that the constriction is much larger by 6 points than the conventional method shown in FIG. differs from the fact that the linear velocity is almost the same no matter where you look just before expansion.

That is, the linear velocity ( A, V
B, Va, and Vb), but the premise is that vA - vB.

It is clear from Figures 1 and 2. ■A《■8 Va ta■b It is.

Furthermore, when the film take-up speed is vF, the stretching ratio that effectively affects the longitudinal direction of the film is expressed as follows.

Fig. 1 ■F/■B Fig. 2 ■F/■b Comparing the two, it becomes ゛■F/■B〈■F/■b. By causing this, the effective stretching ratio in the machine direction can be reduced.

On the other hand, in the present invention shown in FIG. 1, since there is a constriction M, the lateral stretching ratio is increased due to rapid expansion, and compared to the conventional molding method shown in FIG. In the present invention, even if the film is formed during the same folding process, the strength in the lateral direction is increased by increasing the stretching ratio in the lateral direction by the amount of bubble reduction due to the constriction.

The above is summarized in Table 1.

That is, in the present invention, by lowering the stretching ratio in the longitudinal direction and increasing the stretching ratio in the transverse direction, a film with balanced longitudinal and lateral mechanical strength can be formed.

Gui gap, resin extrusion temperature, which are the structural conditions of the present invention,
The solidification position and expansion ratio will be explained in detail.

If an annular die with a die cap smaller than 1.5 mm is used, it is unavoidable to cause constriction in a short period from after the die is discharged to just before the expansion part.

Therefore, in order to generate constrictions, the solidification position must be set high, but if the solidification position is set high, the forming stability will be significantly impaired as described above, and it will be difficult to obtain a film with uniform folding and thickness. It is difficult.

Also, the die gap is 5. If it is 0 mm or more, it is not preferable because when the molten bubble is suddenly stretched in the vertical direction in a short period from the discharge of the die to the expansion part, the bubble cannot withstand the weight of the resin itself and breaks easily. .

The reason why the resin extrusion temperature is regulated to 150 to 230°C is that below 150°C, bubble breakage is likely to occur, and above 230°C (j The melting temperature of the resin sharply decreases, the gathering force decreases, and constriction occurs. This is because bubbles are less likely to occur and the stability of the bubble is impaired.

Note that the resin extrusion temperature is preferably within the range of 150 to 230° C., and is preferably within the following setting range depending on the MI/I of the resin used.

MI (.9/10 min) Temperature ('C) 0. O l~
0.1 180~2300.1~1.0
160~2001.0~5.0 150~
If the solidification position is less than 150 mm, constrictions will occur, and a film with good vertical and horizontal balance cannot be formed, which is not in accordance with the intent of the present invention.

Further, there is no particular limitation on the upper limit of the solidification position, but it is sufficient that the bubble is stable during shaping, and although it varies depending on the molding apparatus, the upper limit is usually considered to be about 1000 ii.

If the expansion ratio is less than 2.0, there will be no stretching effect in the transverse direction, and the film will tend to tear in the longitudinal direction, which is also contrary to the intent of the present invention.

Also, the upper limit of the expansion ratio is as long as the valve is stable during molding.
Although there is no particular limitation, 7 to 8 is generally considered to be the limit.

The annular die itself used in the present invention is not particularly limited, and any of center-feed type spider dies, spiral dies, side-feed type dies, etc. can be used.

The diameter of the annular die is not particularly limited, and may be any commonly used diameter of 20 to 300 mm.

The present invention will be explained below with reference to Examples and Comparative Examples.

The tensile strength and dart impact strength of Examples and Comparative Examples C were measured using the following six test methods.

Tensile test ASTM D882-64T Dart impact Dart strength test according to ASTM D1709-62 The height of the dart was 5 inches.

Example l High-density polyethylene "Stafrene E503J (M.I:
0.3, density: 0.950') under the following cutting conditions to obtain a film having the mechanical properties shown in Table 2.

Inflation: 50 units manufactured by Modern Machinery Co., Ltd.
Blown film manufacturing equipment Die: 50 mm ψ - Spiral die Die gap: 2.5 mm Extrusion resin temperature: 70°C Solidification position = 300 mm Expansion ratio: 1:4.0 Take-up speed: 60 m/in Film thickness :lOμ Comparative example 1 Die gap 0. The film was shaped using an 8 mm encircling die under the same molding conditions as in Example 1 to obtain a film having the mechanical properties shown in Table 2.

Example 2 In the same way as Example 1, “Stafrene E503J (M-I
:0.3, density: 0.950) under the following conditions to obtain a film having the mechanical properties shown in Table 2.

Inflation: 50 mm manufactured by Modern Machinery
ψ blown film manufacturing equipment Die: 50 mm ψ-Spiral die Die gap: 1,5 mm Extrusion resin temperature: 180℃ Solidification position: 400 mm Expansion ratio: 1:5.0 Take-up speed: 45 m/min Film thickness: lOμ Comparison Example 2 Die gap o. A film was molded using an annular die of s mπ under the same conditions as in Example 2 to obtain a film having the mechanical properties shown in Table 2.

Example 3 The high-density polyethylene used was “Stafrene E505J”.
A film having the mechanical properties shown in Table 2 was obtained in the same manner as in Example 1 except that the film was changed to (MI 0.9 density 0.95).

Example 4 Low density polyethylene “Lexron F3 1J (MI2.
The film was shaped using C, density 0.92), the same inflation device and die as in Example 1, and other conditions as follows.

Extrusion resin temperature: l50℃ Expansion: l:2.0 Pick-up speed: 60m/min Solidification position: 300 piles Film thickness = lOμ The mechanical properties of the obtained film are shown in Table 2.

Example 5 Diamond gap is 4. A film having the mechanical properties shown in Table 2 was obtained in the same manner as in Example 1 except that a Qm11L die was used.

As explained above, the film obtained by the present invention has superior tensile strength at break in the transverse direction compared to the film obtained by the comparative example of the conventional method, and the tensile elongation is increased and balanced in both the longitudinal and transverse directions. It can also be seen that a well-balanced film with increased dart impact strength can be obtained.

Furthermore, the expansion ratio was set to 1:5. Stable film molding is possible even if the diameter is made as large as o.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the implementation of the air-cooled inflation method according to the present invention, and FIG. 2 is a schematic diagram of the implementation of the conventional air-cooled inflation method using a die with a die gap of 0.5 to 1.0 mm. Yes. Explanation of symbols, 1... circular die, 2...
・Tubular bubble, 3... Solidification position, 4...
・Bubble stabilizer, M... Constriction, N: Section % from the die exit to the constriction A s a ...
・Dice exit part, B, b... part just before expansion.

Claims (1)

[Claims] 1 When forming polyethylene into a film by the air-cooled inflation method, the die gap is 1.5 to 5.0.
Polyethylene is melt-extruded into a tubular shape from a ring-shaped die within a temperature range of 150 to 230°C, the tubular bubble is made into a constricted state with a diameter smaller than the diameter of the die at a position immediately before expansion, and then at a solidification position of 150 mm or more, the expansion ratio is 1. A method for producing a tubular film, the method comprising forming a tubular film at a temperature of 2.0 or higher.