JPS5892528A - Air-ring and inflation film forming method using the same - Google Patents

Abstract

PURPOSE:To make it possible to perform stable extrusion molding at a high speed and improve the effect of cooling by such an arrangement wherein nozzles are provided so that cooling air is spouted out in both directions, the same and opposite to the running direction of molten and extruded resin film. CONSTITUTION:A tubular resin 2 is formed by circular molten resin extruded from a die 1 and a bubble 4 and a frost line F are formed by sealing compressed air inside the tubular resin 2, and an air-ring 5 is arranged at the midway between the die 1 and the frost line F so as to surround the tubular resin 2, and the tubular resin 2 is cooled by cooling wind blown out from the air-ring 5. At this time, the air-ring 5 is equipped with slits so that cooling wind can be blown out in both directions, the same and opposite to the running direction of the tubular resin 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air ring for cooling thermoplastic resin and a method of molding a blown film using this air ring.

In recent years, in extrusion molding of thermoplastic resins such as high-density polyethylene, low-density polyethylene, and f-lipropylene, high-speed molding has been desired from the viewpoint of improving productivity. However, when conventional air rings are used, high-speed molding results in insufficient cooling and non-uniform cooling, resulting in a significant rise in the 70-string, bubble breathing, and meandering, resulting in uneven film thickness, uneven width, and Otherwise, wrinkles may occur, and furthermore, there may be problems such as popping of the bubbles or a situation where the operation may be stopped due to bubble breakage. Also,
Increasing the air discharge volume of the air ring to compensate for the lack of cooling lowers the frost line, but increases the wind speed, which causes the bubble to become unstable, causing the bubble to vibrate violently, etc.
A film of uniform and good quality was very unlikely.

Therefore, in order to increase the cooling capacity without simply increasing the air discharge amount, double air discharge slits were provided facing the resin extrusion direction, and nine air rings (
% Kaikai No. 53-77258, No. 53-137261,
54-150473, etc.), and those that have a cylindrical body on the top of the air ring to rectify the air (% Publication No. 53-8339, etc.).
etc.) are known. However, in these VClps, the air ring is installed on a high-temperature extrusion die, so when air is discharged from the air ring in the direction of resin extrusion, the heated air at the top of the extrusion die causes the air to be discharged from the air ring. is heated, and the upper part of the extruded resin is particularly insufficiently cooled.

Further, since the flow velocity of the air discharged from the air ring decreases as it advances in the extrusion direction from the air ring, the cooling effect necessary for high-speed molding cannot be expected.

In addition, in addition to the air ring provided on the extrusion die, there are also known devices in which another air ring is provided at a predetermined height position (JP-A-52-101260, JP-A-52-128955, etc.). ), in such a product, the air flow is discharged from the lower air ring and raised in temperature on the outer circumferential surface of the resin, and flows upward along the outer circumferential surface of the resin, so the upper air ring The air discharged from the bubble cannot achieve a sufficient cooling effect, and when the upper air ring is brought close to the bubble expansion part, the bubble becomes unstable. In any case, in the conventional air ring and nine blown film molding methods using these, molding of high-density ethylene, etc.
In other words, it was insufficient for molding using a core under relatively high cross line conditions. Therefore, either you are unable to perform high-speed molding, or you change the blow ratio in various ways.
It was possible to produce films of various thicknesses, especially thick films.

The purpose of the present invention is to provide an air ring that has an excellent cooling effect and enables stable high-speed extrusion molding, and an inflation system using the air ring that has good productivity and that enables the molding of high-quality films with a thickness of 4. To provide a film forming method.

The air ring according to the present invention attempts to achieve the above object by providing air discharge slits for cooling the thermoplastic resin in both the resin extrusion direction and the counter-extrusion direction.

It, the blown film forming method according to the present invention 14 includes: - An air ring having thermoplastic resin cooling slits facing both the resin extrusion direction and the counter-extrusion direction is placed between the extrusion die and the frost line of the bubble. This air ring discharges air in both the resin extrusion direction and the counter-extrusion direction to block the heated air from the extrusion stopper by the air flow in the counter-extrusion direction.
Cooling air is effectively applied to the resin to cool it, and the air flow in the extrusion direction, which has a shortened section flowing along the bubbles, has less fluctuation and has excellent molding stability, while efficiently performing rapid cooling. This aims to achieve the above objective.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment in which the air ring according to the present invention is applied to a blown film forming apparatus. In this figure, from an extrusion die 1, molten resin is extruded in an annular shape to form a tubular resin 2. A cylindrical core 3 fixed to the extrusion die 1 is contained in the tubular resin 2.
is provided. The center core 3 is, for example, Special Publication No. 55-462.
These include those shown in No. 96. In addition, tubular resin 2
Compressed air is sealed inside, and the tubular resin 2 is expanded at a predetermined blow-up ratio on the extrusion direction side of the core 3, and bubbles 4 are formed. 2 in F is formed.

An air ring 5 located at an intermediate position between the extrusion die 1 and the frost line F is arranged to surround the tubular resin 2,
Moreover, the height position is variable.

As shown in an enlarged view in FIG. 2, the air ring 5 is provided with a ll-shaped hollow body 7 having a substantially rectangular cross section and having an annular air flow path 6, and this annular hollow body 7 has an air supply pipe. 8 are connected to each other, and air for cooling the thermoplastic resin is supplied to the annular air passage 6 through the air supply pipe 8.

The inner circumferential edge 9 of the award hollow body 7 has a threaded portion 10 carved all around it, and an air outlet 11 of a predetermined width is provided in the center of the inner circumferential edge 9 along the circumferential direction. It is perforated.

A screw carved on the outer periphery of an annular upper stem 12 is screwed into the threaded portion 10 on the side in the resin extrusion direction, that is, on the upper side in the figure, from the air outlet 11 of the inner periphery 9, and on the other hand, on the opposite side in the extrusion direction. A screw carved on the outer periphery of the annular lower part 13 is screwed into the threaded part 10 so that the air flowing out from the air outlet 11 is guided toward the inner center of the annular hollow body 7. It is configured.

An annular partition plate 14 is provided between the upper wing 12 and the lower jE13.
is provided. The inner edge of the partition plate 14 is connected to the upper wing 1
2 and the lower wing 13 are slightly protruded toward the inner center of the annular hollow body 7, and 14 protruding edges are formed on these edges to protrude by a predetermined length in the vertical direction.

The outer peripheral edge of the partition plate 14 is fixed to the annular hollow body 7 by a plurality of fixing parts 15 located at the center of the air outlet 11 and provided at predetermined intervals along the circumferential direction. 1
The air flowing out from K is separated by the partition plate 14.
It has become.

The air passing between the partition plate 14 and the upper wing 12 is directed upward as a thermoplastic resin cooling air discharge slit formed by the inner 8@ end edge of the upper wing 12 and the protruding edge 14A. The resin is discharged from the slit 16 in the resin extrusion direction,
On the other hand, the air passing between the partition plate 14 and the lower wing 13 is
The thermoplastic resin cooling air is discharged in the counter-extrusion direction from the downwardly facing sleeve 17 formed by the inner circumferential edge and the protruding edge of the lower wing 13 as a discharge slit.

In addition, an upward slit 16 and a downward slit 170
The width is the threaded portion 10K of the upper wing 12 and lower wing 13.
> By adjusting the screwing position of each screw, it can be changed continuously to wide or narrow, and the upward slit 1
6 and the downward slit 17 are configured to be adjusted continuously, that is, steplessly.

Next, the operation of this embodiment will be explained.

The tubular resin 2 extruded from the extrusion die 1 is cooled by being blown against thermoplastic resin cooling air discharged downward from the downward slit 17 of the air ring 5, that is, in a direction opposite to the extrusion direction of the resin.

At this time, the heated air in the upper part of the extrusion die 1 is passed through the air ring 5 and the air discharged downwardly into the tubular resin 2.
The heated air will not surround the outer periphery of the tubular resin 2 and be entrained in the flow of the tubular resin 2.

The tubular resin 2 immediately after being extruded from the extrusion die 1 has a low melt tension, but since it is efficiently cooled by the downward slit 17, the tension gradually increases sufficiently in the resin extrusion direction, making it suitable for high-speed molding. remains stable even when

The tubular resin 2 that has passed through the air ring 5 is further cooled by the thermoplastic resin cooling air discharged from the upward slit 16 and is expanded to form a tsuya del 4. 70 stripes/F are formed at predetermined locations.

On the upper side of the air ring, the air already heated by the tubular resin 2 on the lower side of the air ring 5 has no choice but to surround the outer periphery of the tubular resin 2 and the nozzle 4. The tubular resin 2 and bubbles 4 are efficiently cooled by the air discharged from the upward slit 16.

In this way, since the tubular resin 2 is efficiently cooled in the upper and lower directions of the air ring 5, the frost line F can be maintained at a predetermined level even during high-speed molding.
1 The arrangement position of the air ring 5 is variable at an intermediate position between the extrusion die 1 and the frost line F, and the extruded resin 01111. It may be placed at an appropriate position depending on the molding conditions, etc., but if it gets too close to the extrusion die IK, the cooling by the downward slit 17 will not be achieved sufficiently, and if it gets too close to the sifting line FK, the stability of the bubble in the expansion region will be lost. It is desirable that the groove be located within the range of 10H-10'', where H is the height at the groove.

Further, K, which adjusts the amount of air for cooling the thermoplastic resin discharged from the air ring 5 in the resin extrusion direction and the counter-extrusion direction, rotates the upper jlE 12 and the lower member 13 with respect to the annular hollow body 7, respectively. upward slit 1
The slit widths of the 6th and downward slits 17 may be adjusted respectively.

According to this example, the resin can be cooled extremely efficiently, and even during high-speed molding, there will be no insufficient cooling or uneven cooling, preventing breathing and meandering, and reducing the thickness. It has the effect of being able to stably and efficiently produce a film that does not have unevenness, width unevenness, wrinkles, etc.

Further, even during high-speed molding, the resin can be sufficiently cooled, so the frost line F can be maintained at a predetermined position.

Therefore, there is no possibility that niraglol will cause popping.

In addition, the resin used in this example is a thermoplastic resin in general, but in particular low-density FDL ethylene, diriglopylene, etc., and 70-string resin, which have low melt tension and which have conventionally been difficult to mold at high speeds or into thick materials. Since high-density I-polyethylene and the like that require a high position can be sufficiently cooled, these resins can also be molded at high speed stably and with good productivity.

Furthermore, the air volume and discharge angle of the thermoplastic resin cooling air discharged in the resin extrusion direction and the counter-extrusion direction can be controlled by adjusting the screwing positions of the threaded portions 10 of the upper tool 12 and the lower tool 13. Each can be easily and steplessly adjusted independently.

Therefore, optimum cooling conditions can be easily achieved depending on the type of resin, molding conditions, molding purpose, etc.

In the above-described embodiment, both the upper wing 12 and the lower member 13 of the air ring 50 can be attached to the annular hollow body 7 via the threaded portion 10, but only one of them is attached to the annular hollow body 7. They may be displaceable, or they may be fixed together so as not to be displaceable, as in the other embodiment shown in FIG.
If the tips of the adjusting screws 200 are mounted rotatably but not movable in the axial direction at a predetermined interval along the axis 41, and if the adjusting screws 20 are screwed into the upper fitting 12, the adjustment screws 20 can be rotated. Upward slit 16 and downward slit 17
Therefore, the amount of air discharged in the resin extrusion direction and the counter-extrusion direction and the discharge angle can be simultaneously adjusted.

Further, the amount of air for cooling the thermoplastic resin discharged in the resin extrusion direction and the counter-extrusion direction can be adjusted not only by means of adjusting the slit widths of the upward slits 16 and the downward slits 17, but also by providing a valve mechanism. It may also be adjusted by this.

Further, in the above embodiment, the core 3 is provided inside the annular resin 2, but the core 3 is not necessarily required. However, the provision of the core 3 has the effect of extremely high molding stability even in high-speed inflation molding of ultra-thin films and molding of thick films.

Further, in the above-described embodiments, the air ring 5 was applied to top-blown blown film forming, but it is of course also applicable to bottom-blown blown film forming. Furthermore, the air ring according to the present invention is applicable not only to blown film molding but also to a wide range of tubular resin extrusion molding fields such as thick pipes and sheets.

However, especially in blown film molding, the effect of improving stability in high speed molding and thick molding is remarkable.

As described above, the present invention provides an air ring that has an excellent cooling effect and enables stable high-speed extrusion molding, and has good productivity using the air ring, and can also form a high-quality 4o thick film. It is possible to provide a method for forming an blown film that makes it possible to form an blown film.

The present invention will be explained in more detail with reference to the following examples.

Examples 1 to 3 True book 1f/liethylene (density 0.9551/eIms,
) extruder 1155mm, press fils/chair 1180m,
A blown film of sea bream with a thickness of 25 μm was formed under the following conditions: 95 mm φ500 mm R center core body, temperature 200 tl. The amount of extrusion that can be stably molded was investigated by changing the temperature. The results are shown in Table 1.

Comparative Example 1 Under the same conditions as in Examples 1 to 3, the amount of tree extrusion was examined in the same manner as in Examples 1 to 3. However, the air ring is a conventional type that discharges air only in the extrusion direction (inside!! 13G
-) was provided on the extrusion die.

The results are shown in Table 1.

Examples 4 to 6 High density fS1fV7C density 0.955 Ji' 10x
” % 1 Luto index 0.05p/10-), extruder diameter 55m1 extrusion diameter 80wg, 95-φ
500mH center core, temperature 200℃, resin extrusion 40
Inflated films with different thicknesses of 400 mm during folding were molded under the conditions of #/h, and at this time, the height of the air ring (inner vk130 haze) according to the present invention was changed to evaluate the molding stability for each stacking thickness K. I looked into it. The results are shown in Table 2.

Comparative Example 2 Molding stability was investigated in the same manner as in Examples 4 to 6 under the same conditions as in Examples 4 to 6. However, the air ring is a conventional type that discharges air only in the extrusion direction (inner diameter 130mm
) was placed on the extrusion die.

The results are shown in Table 2.

As described above, the air ring according to the present invention has an excellent cooling effect and enables stable high-speed extrusion molding, and the blown film molding method according to the present invention has good productivity, high quality, and thin O-film. It can be seen that it is also possible to form

[Brief explanation of the drawing]

FIG. 1 shows an embodiment in which the air ring according to the present invention is used for inflatable film molding. 1-extrusion die, 2-tubular resin, 3...core, 4-bubble, 5"' air ring, 7・-Annular hollow body, 10-・Threaded portion, 12
- Upper part, 13...Lower part, 14-Partition plate, 16--Upward slit as a discharge slit for thermoplastic resin cooling air, 1st floor...Thermoplastic resin cooling air Downward slit as a discharge slit, 2G-...Adjustment screw, F--Frost line Figure 1 Figure 2 Figure 3 Procedural amendment (voluntary) September 31, 1939 Commissioner of the Japan Patent Office Kazuo Wakasugi Tono 1 , Indication of the case Relationship to Case No. 191011 Patent Applicant 4, Agent Address TS'1511c*si*em IK CorlH11t
4tff62F Telephone (0!I) $110-Ro310 Name ()908) Patent Attorney Minoru Kinoshita Go (1)
) After "extrusion" on page 2, line 14 of the specification, "inflation film" is completely added. (2) Change "decrease" to "decrease" in line 4 of page 3 of the specification. (3) Add "as an air ring body" before "the annular hollow body 7" on page 7, line 7 of the specification. (4) Add the following sentence between the first and second lines of page 14 of the specification. [Upward slit 16 and downward slit 17] are both provided in the same annular hollow body 7, in other words, when both the upward slit 16 and the downward slit 17 are provided in one air ring body. However, the present invention is not limited to, for example, different air ring bodies arranged adjacent to each other or close to each other may have an upward slot 16 on one side and a downward slot 17 on the other side. (5) To add "as an air ring body" before "annular hollow body" on page 20, line 14 of the specification. that's all

Claims (4)

[Claims] (1) The air discharge slit for cooling the thermoplastic resin is
An air ring characterized in that it is provided facing both the resin extrusion direction and the counter-extrusion direction. (2) In claim 1, at least one of the thermoplastic resin cooling air discharge slits provided in the resin extrusion direction and the counter-extrusion direction has an air discharge amount that is adjusted steplessly. An air ring characterized in that it is configured to (3) In the old inflation film forming method, in which molten resin was extruded into a tube shape from an extrusion die and expanded by internal pressure, it was continuously wound. The air ring installed opposite the extrusion die and the bubble 70
1. A method for forming a blown film, characterized in that the thermoplastic resin is cooled by discharging air through the air ring in both the resin extrusion direction and the counter-extrusion direction. (4) In Claim 3 JJ, the air ring has a height of H from the extrusion die to 70 strokes.
Then, place in the range -LH-j-H-* 0 1
0. A method for forming a blown film, characterized in that: