JPH046541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a flat tube of synthetic resin by an inflation method.

[Conventional technology]

Conventionally, this type of inflation method has been used to manufacture flat tubes by using an air cooling device (air ring) equipped with an annular outlet to cool the outside of the bubble discharged from the annular opening of the die in one or two stages. The ones established were 15225-15225 and 15225-
150473, and one in which a cylindrical body with an open bottom end is placed very close to the outside of the bubble is known as Japanese Patent Publication No. 53-8339.

However, these well-known devices with multi-stage cold air outlets have been widely used in recent years due to their good ability to cool bubbles, but the bubbles near the frost line and above are cooled too much, causing Thermal distortion of the film becomes internal distortion, or the vibration of bubbles often causes small wrinkles in the film when it is folded flat, or distortion occurs during storage after being folded flat.

This tendency is especially noticeable when the bubble blowing ratio is increased, so the blowing ratio is at most 4.
The limit is about twice as much, and there are usually products on the market that are up to about twice that.

As a result of extensive research, the inventor found that rapid cooling is required to improve productivity and to prevent the bubbles from relaxing while expanding the bubbles to the desired diameter. found that better results were obtained by slightly retarding the cooling rate.

[Problem to be solved by the invention]

This method invention is to insulate bubbles in a predetermined zone from the outside air from slightly upstream of the frost line of bubbles that have expanded to a predetermined size, thereby delaying the rapid cooling of the bubbles, preventing uneven cooling of the bubbles, and preventing uneven thickness. This method is used to produce films with less thickness, wrinkles, and other distortions, and is mainly used to form polystyrene into films using an inflation method.

In addition, in device inventions, simple devices can be used to
This method is intended to enable the above-mentioned method invention to be carried out, to stably support bubbles, and to allow one device to be used for changing molding dimensions. It is formed into a film using this equipment.

[Means to solve the problem]

This invention is characterized in that a bubble expanded to a predetermined diameter is passed through a heat-retaining zone slightly upstream of the frost line, which has a width of 0.5 to 1.5 times the bubble diameter and is cut off from the outside air. This is an inflation film forming method.

In another invention, a heat-retaining band has a length sufficient to be wrapped at least once around the entire outer circumference of a bubble expanded to a predetermined diameter, and has a width in the flow direction of the bubble approximately equivalent to the diameter of the bubble, An inflation film forming apparatus characterized in that the apparatus is connected to a machine frame of the film forming apparatus or a part of a stationary part fixed thereto by a locking means that prevents bubbles from being transferred in the flow direction. .

The present invention will now be described based on a typical embodiment of the device invention.

In the figure, 10 is a die, 11 is its annular resin discharge port, and 12 is a bubble discharged from the die. After being expanded and molded to a predetermined diameter, it is folded flat by a pair of folding guide plates 13, and then It is wound up into a roll by a winding device (not shown).

Reference numeral 14 denotes a heat-retaining band, which is usually made of a thick woven fabric made of vegetable fibers, and its length is long enough to be wrapped around the bubble 12 after expansion one or more times, and its width, that is, the direction of bubble flow. dimension l
is about 0.5 to 1.5 times the diameter of the bubble 12, preferably 0.5
~1.0 times. The heat-retaining belt 14 only needs to have heat-retaining properties and heat resistance, and is not limited to natural vegetable fibers such as cotton cloth and linen cloth, but may also be mineral fibers or blends or mixed products thereof, and is not necessarily made of woven fabrics but non-woven fabrics or knitted fabrics. This also falls under the category of the heat insulation zone 14 of the present invention.

The lower edge of the heat insulation zone 14 has several tension members (usually strings made of vegetable fibers) 1 at several places.
5, it is moored to the air cooling device 18 provided around the discharge port 11 or to one of the cylindrical bubble guide tubes 19a, 19b, and 19c provided integrally therewith. The heat insulation zone 14 is a bubble 12
After wrapping it around the outer edge 1 to prevent it from unraveling.
It is advisable to attach a velvet-type fastener 17 to the inside of 6 (see Fig. 3). In the illustrated example, the outside of the heat retaining zone 14 is supported by a holding member consisting of several holding plates 23 curved in the circumferential direction of the bubble.

In addition, the bubble guide tubes shown in the figure are triple-layered in a concentric circle, and the outermost one is taller, and the outermost one 19c is the bubble guide tube 19c.
It is taller than the frost line L and has an inner diameter approximately 1.5 to 2 times the maximum diameter of the bubble 12, and the lower part of this outermost guide tube 19c has a large diameter 24 bulge on the outside. Each of the bubble guide tubes 19a, 19b, and 19c, and between the innermost bubble guide tube 19a and the outer lip 21 of the air outlet 20 of the air cooling device 18, are shielded from the outside air except for the upper end. Individual pressure adjustment chambers 22a, 22b and 22c are formed.
Further, the tension member 15 is anchored to the upper end of the middle bubble guide tube 19b among the triple bubble guide tubes.

In the above example, the device for locking the heat-retaining zone 14 includes a tension member 15, and
Although both the holding members 23 are shown holding the holding member 23, either one of them may be used, or even if the heat insulation band 14 is simply engaged with the pair of folding guide plates 13, in this invention, the heat insulation band shall be considered as a locking device concept.

Embodiments of the method invention will be described along with the effects of the apparatus invention.

First, tube-shaped bubbles are extruded from the annular discharge port of the die 10, and the bubbles are blown out from the air outlet 20 of the air cooling device 18 and the bubble guide tubes 19a, 19b, and 19.
The bubbles are gradually expanded to larger diameters at part c, and the bubbles expanded to a predetermined size are placed between a pair of folding guide plates 13.
Fold it flat and roll it up.

In this case, in the method of this invention, bubble 1
The length of each tension member 15 is determined so that the lower edge of the heat insulation band 14 is located slightly upstream of the frost line L of No. 2, and the heat insulation band 14 is wrapped around the bubble 12 in the circumferential direction. Heat insulation zone 14
In the illustrated example, the heat retaining band 14 is secured by a fastener 17 so that the inner diameter thereof matches the diameter of the bubble to be formed.

As shown in FIGS. 1 and 2, the holding plate 23 of the locking device is brought into contact with the outside of the heat-insulating zone 14 to prevent the bubble and the heat-insulating zone 14 from vibrating back and forth and from side to side. .

When the inflation film is formed in this way, the bubble 12 expands to a predetermined size and the air blown out from the air outlet 20 flows along the surface of the bubble 12 until it reaches the frost line L, forming a laminar flow. However, after that, the bubbles 12 pass through the heat insulation zone formed by the heat insulation zone 14 and cut off from the outside air, so the cooling rate is moderated during this section, and the frost line is substantially reduced. is higher than those without heat retention zone,
The bubbles 12 that have passed through the post-warming zone are cooled by the outside air and folded by the folding guide plate 13.

〔effect〕

In the method of this invention, as described above, the bubble 1 is started from a position slightly upstream of the frost line L.
Since a heat-retaining zone is provided between the dimensions approximately equivalent to the diameter of 2, and the bubble is allowed to pass through this, the temperature in the circumferential direction of the bubble becomes uniform while passing through this zone, and internal residual strain due to temperature distortion is reduced. It becomes a homogeneous film around the entire circumference, and since this insulation zone is isolated from the outside air, the bubble becomes stable.
No wrinkles are generated due to vibration of the bubble 12 when folded by the folding plate 13.

Particularly when molding polystyrene films or molding bubbles at a high blow ratio of 2 to 8 times, uneven cooling may occur due to even a slight air current in the workplace, or the blowing air from the air cooling device 18 may cause uneven cooling. Even if the bubble guide cylinder 19
a, 19b, and 19c and the air cooling device 18 are provided concentrically, and the pressure adjustment chamber 2 is closed except for the upper end.
When used in conjunction with the method of forming bubbles 12 with a small amount of air as 0a, 20b and 20c,
Since the amount of air from the air cooling device 18 is small, the stability of the bubbles 12 above the bubble guide tube is poor and vibrations are likely to occur. However, with the method invention described above, such drawbacks can be overcome and inflation can be prevented. Films can be formed.

In particular, in the case of a method in which a heat-retaining band having heat resistance and heat-retaining properties is directly wrapped around the bubble, the heat-retaining effect and stabilizing effect of the bubble are particularly remarkable.

If the entire heat retention zone is located downstream of the frost line, distortion due to thermal imbalance cannot be removed, and if the length l of the heat retention zone is smaller than the above limit, distortion removal and bubble retention will be incomplete. If l is too large, bubbles that cannot be cooled down sufficiently after passing through this heat-retaining zone will be folded, causing blocking.

In the device invention, in addition to being able to carry out the method invention described above, the heat insulating band 14 has heat resistance and heat retention, so it can sufficiently withstand the heat from the bubble 12 and has a sufficient heat insulating effect, and the band can be wrapped around it. Since the heat insulating band 14 is designed to be able to freely match the dimensions of the bubble, and since the heat insulating band 14 is locked to an immovable part by a locking device, the bubble 1 can be adjusted freely.
It does not move even with the flow of 2.

[Effects of Examples]

In particular, if the insulation band 14 is made of cotton cloth or other material with a fine mesh and soft surface, the surface of the bubble 12 will not be damaged, and if the locking device is just a tension member 15, the structure will be simple. It is inexpensive, can be easily added to existing equipment, and exhibits excellent moldability. Such moldability can be fully exhibited even when molding polystyrene film.

In the case where the velvet type fastener 17 is attached to the inside of the outer end 16 of the heat insulating band 14, the inner diameter of the heat insulating band 14 does not change during molding, there is no risk of it unraveling, the inner diameter can be changed steplessly, and various types of bubbles can be formed. Able to handle dimensional shaping.

In addition, the stability of the bubble becomes even more excellent in a device equipped with a curved holding plate 23.

In addition, the dimensions of the inner and outer lips of the air outlet of the illustrated air cooling device 18 and the bubble guide tubes 19a, 19b,
For example, the dimensions of 19c are when the diameter of the annular discharge port 11 is 100 mm, and the inner lip diameter is
120 to 160 mm, diameter of outer lip 21 is 150 to 160 mm
240mm, bubble guide tube 19a has a diameter of 220 to 360mm,
The height is 0.7 to 1 times this diameter, and the diameter of the middle bubble guide cylinder 19b is 420 to 560 mm, and the height is 0.7 to 1 times this diameter.
The diameter of the outermost bubble guide cylinder 19c is approximately 700 mm, and its upper end reaches the heat retention zone, and the lower part is even larger, with a diameter of 950 mm, for example, and the diameter of the outermost bubble guide cylinder 19c is approximately 700 mm. The cage pressure decreases in order, and bubbles are sucked in the vicinity of the inner and outer lips and the upper edges of each bubble guide cylinder 19a, 19b, and 19c by the ventilly effect, and the pressure in other parts is closed to the outside air except for the upper end. The bubble 12 is supported by the pressure in the adjustment chamber, enabling expansion molding with a high blow ratio. It is desirable to use such a device in combination with the method and device of the present invention.

[Brief explanation of drawings]

The drawings are related to this invention and show typical embodiments of the device invention, in which Fig. 1 is a partial longitudinal sectional view, Fig. 2 is a cross-sectional plan view taken along the line 2-2 in Fig. 1, and Fig. 3 The figure is a perspective view of the heat insulation zone. Main symbols in the figure: 10...Die, 11...Annular discharge port, 12...Bubble, 13...Pair of folding guide plates, 14...Heat insulation band, 15...Tension member, 23...Holding Plate, L...Frost line, L...Height dimension of the heat insulation zone.

Claims (1)

[Claims] 1. A bubble expanded to a predetermined diameter is passed through a heat-retaining zone that has a width of 0.5 to 1.5 times the bubble diameter from slightly upstream to downstream of the frost line and is isolated from outside air. An inflation film forming method characterized by forming. 2. The inflation film forming method according to claim 1, wherein the heat-retaining band is formed by wrapping a heat-resistant and flexible heat-retaining band directly around the bubble. 3. It has a length sufficient to be wrapped at least once around the entire outer circumference of a bubble expanded to a predetermined diameter,
A heat insulating zone having a width approximately equivalent to the diameter of the bubble in the flow direction of the bubble is attached to the machine frame of the film forming apparatus or the immovable part fixed thereto by a locking means that prevents the bubble from moving in the flow direction. An inflation film forming device characterized in that some parts are connected. 4. The heat-retaining zone is made of a thick fabric formed from one of vegetable fibers and mineral fibers, and has a width (length in the bubble transport direction) of 10 to 50 cm, preferably 15 to 25 cm. An inflation film forming apparatus according to claim 3. 5 The heat insulation zone locking device includes holding members provided on several machine frames with curved surfaces along the outer circumferential surface of the bubble;
The inflation device according to claim 3, characterized in that the inflation device is made of one of several tension members provided on one of a plurality of concentric cylinders for guiding bubbles. Film forming equipment.