JPH0447611B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a cooling device for a tubular parison (sheath body) that is inflation-molded, and a method for producing plastic film using the cooling device. BACKGROUND OF THE INVENTION Inflation molding devices for obtaining transparent films are known. This inflation molding device consists of three elements arranged one above the other along the direction of movement of the tubular parison: a lower closed chamber (the so-called annealing chamber) and a strong gas flow perpendicular to the tubular parison. It consists of an intermediate blow ring which promotes the solidification of the plastic material and an upper chamber which brings the tubular parison into contact with air flowing along the direction of tension of the tubular parison. A device of this type is described in European Patent Application No. 0041803. This device is capable of extruding polyethylene films with a taux de gonflage=2. However, it is insufficient to extrude polyethylene films with expansion coefficients greater than 2 (see Comparative Examples below in this regard). Furthermore, known devices can only improve the optical properties of certain resins, such as low-density radically polymerized polyethylene, ethylene/vinyl acetate copolymers, and linear low-density polyethylene, which have fairly good optical properties. % or more of turbidity (measured according to ASTM standard D103-77) with sufficient optical properties is difficult to produce. Further, with conventional cooling devices, it is not possible to improve the optical properties of blown film while maintaining high productivity. Problems to be Solved by the Invention It is an object of the present invention to produce a blown film that is excellent in optical properties, particularly in terms of transparency and turbidity, and that can be applied to most resins. An object of the present invention is to provide an efficient film cooling device. Means for Solving the Problems The present invention has a blowing ring in the middle portion that blows a strong gas flow toward the tubular parison, and an upper chamber that contacts the tubular parison with the air flow flowing in the direction in which the tubular parison is pulled out. A device for cooling a plastic film obtained by blow-molding a tubular parison, which is characterized in that the lower part has an open lower chamber with at least one opening. Function: The degree of opening of the opening can be adjusted using a disk having holes or the like. Preferably, the height of the lower chamber and the height of the upper chamber are also adjusted by a series of spacer elements. Furthermore, it is preferable to provide means for adjusting the flow rate of air sent in the direction of withdrawal of the tubular parison within the upper chamber. The blowing ring has a thickness such that the angle A formed between the axis perpendicular to the tubular parison and the direction of the air flow blown from the blowing ring is within the range of 0 to 85 degrees, and the opening degree F is 0.1 to 15 mm. Preferably, it is adjustable. The degree of opening F means the degree of opening of the lip of the blowing ring through which the airflow blown toward the tubular parison passes. In one embodiment of the present invention, the opening degree F of the inlet of the inlet ring is 0.1.
The strength of the airflow can be adjusted by changing it within the range of mm to 15 mm. One embodiment of the invention includes an internal cooling device above the extrusion nozzle, which has at least one air supply passage and at least one air exhaust passage passing axially through the extrusion nozzle. This internal cooling device also has at least one
Height can be adjusted with two spacer elements. These spacer elements can consist of at least one gas-tight element and/or at least one element with an opening. By using elements with openings it is possible to cool the interior of the tubular parison near the exit of the extrusion nozzle. Hereinafter, specific examples of the apparatus of the present invention will be described, but the present invention is not limited to the following examples. DESCRIPTION OF THE PREFERRED EMBODIMENTS The attached FIGS. 1 and 2 are cross-sectional views, and the elements designated by reference numerals 1 to 15 are common to these two figures. In a first embodiment of the invention, shown in FIG. It is slowly cooled in the lower chamber consisting of and 4. In the lower part of this lower chamber, an aperture adjustment member 5, specifically a disc 5 having holes, is provided. By adjusting the opening using this opening adjustment member 5, suction air is generated due to the decompression effect caused by the air flow 7 blown into the upper chamber constituted by spacer elements 14 and 15, which will be explained later. Adjust the amount of step 6. The tubular parison 1 has spacer members 3, 4
The area is moderately cooled by the air flow 8 and is not subject to excessive dimensional changes. The tubular parison 1 is then rapidly cooled by an air jet 9 from the blow ring 10.
In this figure, the air jet 9 is blown at right angles to the tubular parison 1. The tubular parison 1 leaving the blow ring 10 is
At least two spacer elements 14 are then provided along the direction in which the tubular parison 1 is stretched;
Enter the upper chamber consisting of 15. Inside this upper chamber, the air flows in a flux 7. The flow rate of this air flux 7 is regulated by a regulating device 12 . In the upper chamber, a pressurized air introduction pipe 16
The tubular parison 1 is inflated to its final size under the action of pressurized air supplied into the interior of the tubular parison 1 introduced from the inside of the tubular parison 1. The blown and finally completely solidified blown film is pulled out by a feeding device 17. In a second embodiment of the invention, shown in FIG. 2, the direction and intensity of the air jet 9 emitted from the blow ring 10 can be adjusted simultaneously. (1) Adjustment of the blowing direction: The blowing angle of the air is varied using different blowing rings 10 with blowing angles A ranging from 0 to 85°. (2) Adjustment of blowing strength: Opening degree F of the blowing lip of the blowing ring 10
Adjust. This adjustment makes it possible to vary the amount of airflow 9 blown into the upper chamber relative to the airflow 11 blown towards the tubular parison. The turbulence of the air flow 7 can be reduced by providing, for example, a grid 18 above the air volume regulating means 12. Inside the tubular parison 1 there is a cooling device 19 arranged inside the tubular parison 1 of the upper chamber.
Pressurized air is introduced via. This cooling device 1
9 height is spacer elements 20, 21 and 22
It can be adjusted using Bottom spacer element 2
2 has an opening near the nozzle outlet for letting air flow escape. The cooling device 19 has an air supply path 19A and an air discharge path 19B. The completely solidified blown film is drawn out by a delivery means 17 (not shown). This feeding means is the same as in the previous embodiment. A second object of the invention is a method for producing a plastic film by inflation molding, which comprises the steps of extruding a molten plastic material from an extrusion nozzle, blow molding it, and cooling it, the blown film being subjected to a cooling device as described above. It is characterized by the fact that it is sent through. In this method, it is advantageous for the ratio of the flow rate of air sent to the lower chamber to the flow rate of air introduced into the blow ring to be in the range 0.1 to 0.5. The method of the present invention can be applied to resins such as radically polymerized polyethylene, high density polyethylene, polypropylene, polybutene-1, linear low density polyethylene, and mixtures thereof, and which has a fluidity coefficient.
It has the advantage that films with excellent properties (transparency, turbidity) can be obtained from resins in the range of 0.1 to 10 dg/min (measured according to ASTM standard D1238/73). In particular, in the method of the present invention, a film with excellent optical properties can be obtained from radically polymerized polyethylene having a fluidity coefficient of 30 dg/min or more. The resin used in the method of the present invention may be one that has been stored until the desired product is manufactured using a molding technique. The method according to the invention also makes it possible to obtain films with much higher production and/or expansion rates than the method described in the aforementioned European Patent Application No. 0041803. In order that the advantages of the method of the invention compared to conventional methods may be more fully understood, examples of the invention are described below. Examples 1 to 4 Molten plastic material is extruded through the nozzle of an extruder with a diameter of 30 mm, then blow molded in the apparatus described above, in particular the apparatus shown in FIG.
Manufacture 40μm film. The characteristics of the extruder nozzle and cooling device are as follows: Nozzle diameter = 50 mm, gap = 0.5 mm Height of the lower chamber of the cooling device = 250 mm Height of the upper chamber = 250 mm Introduced into the blow ring The ratio R of the amount of air supplied to the lower chamber relative to the amount of air is shown in Table 1 below. The expansion coefficient TG (ratio of the blown film diameter to the nozzle diameter) and the material feed rate Q (expressed in kg/hour) are also shown in Table 1. The material used is LOTRENE (trademark)
FA0401 (manufactured by CdF Chimie) is a low density radically polymerized polyethylene having a flow coefficient of 4 dg/min (measured according to ASTM standard D1238-73) and a specific gravity of 0.918. Table 1 also shows the following properties: (1) Extrudability (E): Blown films that do not exhibit optical defects such as streaks are marked with a (+), whereas inflated films that have this optical defect are Flasion films are indicated by (-). (2) Transparency (C): Measured according to ASTM standard D1746-78, and measurement results are expressed in %.

[Table] Comparative Examples 1A to 4A The same materials used in Examples 1 to 4 were extruded in the same extruder as used in Examples 1 to 4, and then the equipment described in European Patent Application No. 0041803 was extruded. A film with a thickness of 40 μm is produced by blow molding and cooling. Table 2 below shows Q, TG, R
The operating conditions and properties of the resulting blown film are shown.

[Table] Examples 5 to 8 Examples 1 to 4 were repeated, but the material was LOTRENE (trademark) FB5026 (manufactured by CdF Chimie).
The commercially available fluidity coefficient is 0.6dg/min (ASTM standard
D1238-73) and a low density radically polymerized polyethylene with a specific gravity of 0.921 was substituted. Table 3 below shows the operating conditions such as Q, TG, R, etc. and the measurement results obtained on the resulting blown film with a thickness of 40 μm. The same equipment as in Examples 1 to 4 was used for the measurements.

[Table] Comparative Examples 5A to 8A The same plastic materials as Examples 5 to 8 were extruded using the same equipment and blow molded using the same equipment used in Comparative Examples 1A to 4A - cooled and blown to a thickness of 40 μm. I got the film. The operating conditions and the measurement results obtained are shown in Table 4 below. Extrudability (0) indicates that it is impossible to obtain a blown film.

[Table] Example 9 and Comparative Example 9A LOTREX (trademark) FW1290 (CdF
Table 5 below shows the results obtained for a commercially available linear low density polyethylene (manufactured by Chimie) with a flow coefficient of 1 dg/min and a specific gravity of 0.919. The feed rate of material is 3 Kg/hour and the expansion coefficient is 2. Example 9 uses the cooling device shown in FIG. 1, and Comparative Example 9A uses the cooling device shown in
This is the case when the one described in No. 0041803 is used. T is the turbidity (expressed in %) measured according to ASTM standard D103/77. The extruder used was the same as that used in Examples 1-8.

[Table] Examples 10 to 12 Plastic material was extruded from the nozzle of a WINDMOLLWE AND HOLSCHER extruder (screw diameter 60 mm), and then blow molded and cooled using the equipment shown in Figure 2. and produce film. The characteristics of the nozzle and cooling device are as follows: Nozzle diameter = 160 mm, gap thickness = 0.8 mm Cooling device: Lower chamber height = 640 mm Upper chamber height = 320 mm Air flow blowing from the blow ring The included angle A is
At 75°, the opening degree F of the inlet through which the airflow flowing towards the tubular parison was 7 mm. The material used was LOTRENE® FB3010 (manufactured by CdF Chimie), a commercially available low-density radical polymerized polymer with a fluidity coefficient of 0.25 dg/min (measured according to ASTM standard D1238-73) and a specific gravity of 0.922. It is polyethylene. Table 6 below shows operating conditions such as TG, R, etc.
The results obtained for a blown film of thickness e in μm are shown. Material flow rate is 108
Kg/hour.

[Table] Comparative Examples 10A to 12A The same materials and the same extruder were used as in Examples 10 to 12, but the cooling of the tubular parison was used as in Examples 10 to 12, and the lower opening of the lower chamber was The film was produced by using it in a closed and airtight state. The feed rate of material was the same, 108 Kg/h, and the operating conditions and measurement results obtained are shown in Table 7 below. An extrudability (E) of (0) means that a blow molded sheath cannot be obtained.

[Table] Examples 13-15 The same equipment as Examples 10-12 is used. The plastic material used is trademark LOTRENE FB5005
(manufactured by CdF Chimie), with a fluidity coefficient of
0.6dg/min (measured according to ASTM standard D1236-73)
and low density radically polymerized polyethylene with a specific gravity of 0.921. Table 8 below shows the operating conditions such as TG, R and the results obtained for the blow molded sheaths.
The feed rate of material was 102Kg/hour.

Table Comparative Examples 13A-15A Blow molded sheaths are made using the same materials used in Examples 13-15, but this time using the equipment already used in Comparative Examples 10A-12A. Table 9 below shows the operating conditions as well as the measurement results obtained for the blow molded sheaths. The amount of material supplied is the same as in Examples 13-15, i.e. 102
Kg/hour.

[Table] Example 16 and Comparative Example 16A 75% trademark LOTREX FW 1290 (CdF Chimie
Extrusion was carried out using a resin mixture consisting of linear polyethylene, commercially available as CdF Chimie, and 25% radically polymerized polyethylene, commercially available under the trademark LOTRENE FB 3010 (CdF Chimie).
The film is made by blow molding. In Example 16, cooling was performed using the equipment already used in Examples 10 to 15, and in Comparative Example 16A, cooling was performed using the equipment already used in Examples 10 to 15.
It was cooled with the equipment used in 10A to 15A. These examples show that the blow molded sheath thickness e=
The test was conducted at an expansion rate of TG=2 for a diameter of 25 μm and a material feed rate of 65 kg/hour, and the results are shown in Table 10.

【table】 [Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the cooling device of the present invention, and FIG. 2 is a cross-sectional view showing another embodiment of the cooling device of the present invention. Main reference numbers: 1... tubular parison, 2... extrusion nozzle, 3, 4... spacer element, 5...
Opening, 7, 8, 11... Air flow, 9... Air jet, 10... Blow ring, 12... Flow rate adjustment device, 14, 15, 20, 21, 22... Spacer element, 16... Addition Pressurized air supply pipe, 17... feeding device, 18... grid, 19... internal cooling device.

Claims (1)

[Scope of Claims] 1. Upper chamber 14, 1 which has a blowing ring 10 in the middle part that blows a strong gas flow toward the tubular parison 1, and brings the tubular parison into contact with the air flow 7 flowing in the direction in which the tubular parison is pulled out.
5 in the upper part of a plastic film obtained by blow molding a tubular parison, characterized in that the lower part has an open lower chamber 3, 4 with at least one opening. Device. 2. The cooling device according to claim 1, wherein the opening degree of the opening is adjustable. 3. The cooling device according to claim 2, wherein the opening degree is adjusted by a disk 5 having holes. 4. The cooling device according to any one of claims 1 to 3, wherein the height of the lower chamber is adjustable. 5. The cooling device according to any one of claims 1 to 4, wherein the height of the upper chamber is adjustable. 6. Cooling device according to any one of claims 1 to 5, comprising means 12 for adjusting the flow rate of air sent in the direction of withdrawal of the tubular parison in the upper chamber. 7. Claim No. 7 having a blowing ring 10 such that the angle A between the axis perpendicular to the tubular parison and the direction of the air flow blown from the blowing ring is in the range of 0 to 85°. The cooling device according to any one of items 1 to 6. 8. The cooling device according to any one of claims 1 to 7, wherein the opening degree F of the blow ring 10 that blows out the air flow toward the tubular parison can be adjusted to a thickness of 0.1 to 15 mm. 9. Any one of claims 1 to 8 having an internal cooling device above the extrusion nozzle having at least one air supply passage 19A and at least one air discharge passage 19B passing through the extrusion nozzle 2 in the axial direction. The cooling device according to item 1. 10. The cooling device according to claim 9, wherein the height of the internal cooling device is adjustable. 11. Cooling device according to claim 10, wherein the height of the internal cooling device is adjusted by at least one spacer element 20, 21, 22. 12. Cooling device according to claim 11, wherein the spacer element consists of at least one gas-tight element 20, 21 and/or at least one element 22 with an opening. 13 In a method of manufacturing a plastic film by inflation molding and cooling a tubular parison 1 of molten plastic material extruded from an extrusion nozzle 2, an air flow 7 flowing in the direction of drawing out the tubular parison.
and the tubular parison.
4, 15 in the upper part, a blow ring 10 in the middle part for blowing a strong gas flow towards the tubular parison, and an open lower chamber 3, 4 with at least one opening in the lower part. A method characterized in that the plastic film is cooled using a cooling device. 14. The method of claim 13, wherein the ratio of the air flow rate drawn into the lower chamber to the air flow rate blown out of the blow ring is in the range 0.1 to 0.5. 15. A method according to any one of claims 13 to 14, wherein the plastic material is selected from the group consisting of polyethylene, polypropylene, polybutene-1 and mixtures thereof. 16 The fluidity coefficient of plastic material is 0.1~
Claim 15 within the range of 10 dg/min
The method described in section.