JPS6371331A - Manufacture of tubular film - Google Patents

Abstract

PURPOSE:To manufacture tubular films speedily and of good productivity without inferior quality and production loss by providing a floating stabilization body in the expanded area upper than an expansion starting point and a fixed stabilization body between a ring die and the expansion starting point. CONSTITUTION:A first mandrel 4, that is a fixed stabilization body, is mounted on a hollow supporting strut 3 coaxial to a ring die 1 connected with an extruder. Next, a second mandrel 9, a fixed stabilization body, is mounted on the upper part of the first mandrel 4 between an expansion starting point of a resin tubular body 8 and the first mandrel 4. Then, one or more of floating stabilization body 10, movable during manufacturing a membrane are mounted upper than an expansion starting point 13. Accordingly, the diameter at expansion starting point of the resin tubular body is not expanded forcibly by the floating stabilization body, and as the floating stabilization body moves up and down continuously and speedily in accordance with the up and down movement of the expansion starting point, films of good strength and good appearance can be manufactured during the operation for a period of long time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improved process for making tubular films. More specifically, the present invention aims to improve the hole-making method to efficiently produce a high-quality film that exhibits well-balanced strength in both the direction and the transverse direction when forming a tubular film of polyolefin resin by the inflation method. This is related to method V.

Conventional technology In recent years, films of polyolefin resins, especially high-molecular-weight, high-density polyethylene, have been developed using inflation methods such as air-cooled inflation methods to improve the molecular orientation in the lateral direction and achieve a complete balance of strength in the longitudinal and lateral directions. It is widely used as a balance film for packaging, agricultural and industrial materials. In this case, in order to increase the molecular orientation in the lateral direction, the molten resin tubular body extruded from the annular die is raised while maintaining a diameter close to the diameter of the die, and when it reaches a predetermined height, it is expanded. The further away the expansion starting point is from the die surface, and the higher the expansion ratio (the ratio of the bubble diameter after expansion to the die diameter), the higher the lateral molecular orientation becomes. The strength becomes balanced with the strength in the vertical direction.

Therefore, in order to achieve a good balance of strength and increase the impact strength of the entire film, it is necessary to either increase the expansion ratio or raise the starting point of the expansion, but in this way, the bubbles after expansion must be increased. Significant horizontal and vertical shaking9 causes the resulting film to wrinkle, sag, and fluctuate during folding, resulting in a decrease in quality. In order to suppress the shaking of the bubble after expansion and prevent the occurrence of the above-mentioned trouble, a method has been developed in which the constriction of the baffle is brought into contact with a mandrel having a diameter smaller than the diameter of the die. No. 2180), a method in which a mandrel with a diameter larger than the die diameter is placed at a position where the bubble of a post set up in the center of the die begins to cool and solidify (Japanese Patent Publication No. 55-123
No. 67), the diameters of the lower and upper ends of the mandrel and the diameter of the circular base that attaches it to the die are fully regulated, and the bubble is raised along the circumferential side of the mandrel and rapidly expanded before reaching the upper end. Method (Special Publication No. 59-5408)
, melting is carried out on the surface of the cylindrical part of the mandrel, which has a diameter of 1.01 to 1.2 times the lip diameter of the die, a sufficient length, and a hollow cylindrical part made of metal with a roughened surface. A method (Japanese Patent Publication No. 13964/1983) has been proposed in which the resin tubular body is brought into contact with the resin tubular body before constriction occurs and expansion is started on the surface of the cylindrical part.

Problems to be Solved by the Invention However, in these methods, since the position of the stabilizer is fixed, various factors such as hunting of the extrusion amount, extrusion Due to changes in the temperature of the resin being used, or changes in the temperature of the air sent in from the blower, the expansion starting point inevitably moves upward or downward on the stabilizer, and eventually comes off the stabilizer or the diameter of the stabilizer changes. This may lead to undesirable situations such as being smaller than the diameter at the starting point of expansion, or conversely being too large. Under these conditions, the resin/tubular body shakes horizontally or even vertically, causing significant changes in the dimensions of the film, large wrinkles in the film, and even weakening of the film's strength. Various inconveniences occur, such as a significant decrease in the film's strength and scratches on the inner surface of the film.

Therefore, in the above method, in order to avoid such various inconveniences, it is necessary to manually adjust the air volume of the extruder and the prower, and as a result, it is necessary to manually adjust the air flow rate of the extruder and the prower, and as a result, it is necessary to manually adjust the air flow rate of the extruder and the proir. There is a problem in that quality defects and product losses are inevitable before and after the adjustment work.

On the other hand, in order to cope with the vertical movement of the expansion starting point, a method has been proposed in which a stable body is erected and moved up and down by an air cylinder for all the supports, and the position of the stable body is varied (especially In this method,
It is difficult to change the inflation start point steplessly and automatically in response to the rise or fall of the inflation start point, and it must be operated manually while monitoring the up and down movement of the inflation start point, making adjustment work difficult. However, there are disadvantages such as poor quality and a tendency to cause product loss.

Furthermore, all of these known methods have the disadvantage that the physical properties of the resulting film are impaired due to contact of the expansion starting point of the resin tubular body with a fixed stabilizer.

The purpose of the present invention is to overcome the drawbacks of the conventional inflation method and to produce polyolefin resin tubular films with balanced strength in the longitudinal and lateral directions at high speed and without causing quality defects or product loss. The object of the present invention is to provide a manufacturing method with high productivity, such as a reduction in the number of parts.

Means for Solving the Problems As a result of various studies on the operating conditions when producing a polyolefin resin tubular film by the inflation method, the inventors found that the polyolefin resin tubular body extruded from an annular die has a die diameter of When forming a tubular film by expanding it after raising it with a diameter approximately equal to that of
By placing a stable body (hereinafter referred to as a floating stable body) in the expansion region above the expansion start point, which is guided by a support and floats and automatically moves up and down in accordance with the rise or fall of the expansion start point. The stabilizer always remains in contact with a portion of the resin tubular body having almost the same shape in the expansion region above the expansion start point to achieve the above purpose. It has been discovered that the above object can be achieved more effectively by providing a fixed and stable body between the expansion start point and the expansion start point, and based on this knowledge, the present invention has been completed.

That is, the first aspect of the present invention is to form a tubular film by expanding a polyolefin resin tubular body melt-extruded from an annular die by an inflation method while bringing it into contact with a stabilizer provided coaxially with the annular die. hit, placed at a suitable location in the expansion region above the expansion start point,
At least one floating stable body that is movable up and down along a support provided coaxially with the annular die and whose weight is less than the supporting force of the stable body of the resin tubular body at the contact position is always provided. The present invention provides a method for producing a tubular film, which is characterized by expanding a resin tubular body while contacting and following the position of a resin tubular body having a diameter equal to the diameter of the resin tubular body.

In addition, the second invention is to form a tubular film by expanding a polyolefin resin tubular body melt-extruded from an annular die by an inflation method while bringing it into contact with a stabilizer 1 (provided coaxially with the annular die). at least one fixed stabilizer provided at a suitable location between the die and the expansion start point and in full contact with the resin tubular body, and further disposed at a suitable location in the expansion region above the expansion start point. It can be freely moved up and down along a support provided coaxially with the die.
and at least one floating stabilizer having a weight 1 less than the stabilizer supporting force of the resin tubular body at the contact position,
The present invention provides a method for producing a tubular film, characterized in that a resin tubular body is expanded while always contacting and following the position of a resin tubular body having a diameter equal to that of the resin tubular body.

The supporting force that the resin stabilizer has here means that when the resin tubular body supports the floating stabilizer, it supports the floating stabilizer without substantially changing the shape of the resin tubular body at that position. It is the power to be able to. In addition, the expansion start point here refers to the point at which the molten resin tubular body extruded from the annular die is taken up and expanded with a diameter approximately equal to the diameter of the die, or while expanding or contracting slightly. This refers to the point at which the diameter begins to expand rapidly.

Furthermore, the expansion region is the region where the tubular body expands from the expansion start point, its diameter expands, and finally reaches a constant diameter, that is, the region where the tubular body continues to expand. That's true.

The floating stabilizer arranged in the present invention appears as if it is floating while being in contact with the resin tubular body in this expansion region. The diameter of the expansion starting point of the resin tubular body is not forcibly expanded by the floating stabilizer, and the stability of the tubular body as a whole is not impaired. Since the floating stabilizer moves up and down continuously and quickly in response to the up and down movement of the expansion starting point, a film of good quality both in terms of strength and appearance can be produced during long-term operation. can do.

Furthermore, a fixed stable body is a stable body that is moved to an arbitrary position on a support and then fixed with a lock screw or the like.

Next, one embodiment of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a main part showing an example of an embodiment of the present invention, in which air blowing and circulation are provided near the upper and lower ends coaxially of an annular die l connected in an extrusion manner. A hollow column 37ft having an opening 5.11 and communicating with the air blowing pipe 2: erected by screw fitting, and a first mandrel 4, which is a fixed stable member, is attached to the column. The first mandrel 4 to be attached here has an outer diameter large enough to come into contact with the resin tubular body 8 extruded from the annular die 1, and its shape is cylindrical, disc-shaped, pincushion-shaped, or truncated conical. Selected from etc. Note that it is preferable that the mandrel 4 has a ventilation hole 6. The main action of this g-mandrel is that the resin tubular body is dented inward by the pressure of the air from the air ring 7.

The goal is to prevent that stability from being compromised. The size and shape of the first mandrel 40 must be such that the friction between the resin tubular body 8 and the mandrel becomes too large, thereby impeding the film start-up work and the movement of the tubular body rising during operation. Generally, the outer diameter is preferably in the range of 1.0 to 1.5 times the diameter of the tubular body.

Next, above the first mandrel 4, that is, the resin tubular body 8
A second mandrel 9, which is a fixed stable body, is provided between the expansion start point and the first mandrel 4.

Both the first mandrel and the second mandrel can move up and down on the hollow support 3, but during operation they are fixed to the support using a method such as screwing. The number of second mandrels 9 is not limited to one, and two or more mandrels can be used if necessary, and the shape of the second mandrel 9 can be selected from various shapes as appropriate, similar to the first mandrel. It is also preferable to have ventilation holes 6 like the first mandrel. The main action of this second mandrel is
The purpose is to support the resin tubular body 8 in the middle, and like the first mandrel 4, its size and shape are such that the friction between the resin tubular body 8 and the second mandrel 9 becomes too large, causing the film to rise. The outer diameter must be such that it does not impede the upward movement of the tubular body during work or operation, and usually the outer diameter is preferably in the range of 1.0 to 1.5 times the diameter of the tubular body.

Next, the floating stable body 10, which is a main part of the present invention and is movable during film formation, will be explained. One or more floating stabilizers 10 are installed above the inflation starting point 13. During film production, the floating stabilizer is
It is not fixed to the column, as it needs to be able to move up and down along the column. If a plurality of floating stabilizers are used, the first floating stabilizer (the one closest to the die) should
so that it is above the position.

Once the floating stable body 10 is erected, the floating stable body 10 is 1! as shown in FIG. i@ is located in the expansion region of the tubular body 8, is in contact with the resin tubular body, and is supported by its supporting force. The diameter of the second floating stable body 10 is larger than the diameter of the first floating stable body IO. Its position is therefore above the floating stabilizer 10. Furthermore, the diameters can be sequentially increased and placed upward. In addition, the outer diameter of the lowermost floating stabilizer (the one closest to the die) of the part that contacts the film is the expansion starting point 13' (third point) of the resin tubular body when the floating stabilizer is not used.
(see figure) 1.02 to 168 times the diameter, preferably 1.0
It is selected in the range of 5 to 1.5 times. On the other hand, the weight of the floating stabilizer is less than or equal to the supporting force of the resin tubular body when the floating stabilizer contacts the resin tubular body. Therefore, the floating stabilizer is supported by contacting the resin tubular body without substantially changing the shape of the resin tubular body. However, the weight of the floating stabilizer is huge! 9. It is preferable that it is not too light. This weight is appropriately selected depending on various conditions such as film thickness, fold diameter, and take-up speed during inflation molding. Also, for weight adjustment,
It is convenient to place a weight 12, such as a weight, on top of the stabilizer. This weight may be mounted on each floating stabilizer or on a particular floating stabilizer.

On the other hand, it is preferable that the floating stabilizer has air circulation holes 6e-W similarly to the first and second mandrels.

The floating stabilizer 10 can be moved along the support 3 by sliding the support 3 through a cavity or hole drilled in the center of the floating stabilizer 10, or by using a ball bearing. Usually considered methods are used, such as a method of moving using a rotating body such as. In either case, the sliding or rolling portions between the stabilizer and the weight and the support column 3 must be structured so that the vertical movement of the stabilizer and the weight is not hindered and smooth movement is possible. therefore,
There shall be no significant gaps between the column and the sliding or rolling parts of the stabilizer and weight. Further, in order to smooth the vertical movement of the stabilizer and the weight during operation, it is preferable to apply a lubricant such as oil or grease to the 9 parts that slide or roll with the hollow support 3. Furthermore, if necessary, a fastener 15 for determining the reciprocating range in the vertical direction of the floating stable body 10 is placed at an appropriate position below the lowest level of the floating stable body 10 and above the highest level including the weight. It may be attached by screwing or the like.

Examples of the polyolefin resin used in the present invention include low density, medium density or high density polyethylene, homopolymers such as polypropylene, copolymers of ethylene or propylene and other monomers, etc. Polyethylene, which has a high melt viscosity and a high melt tension, gives favorable results.

The method of the present invention can be applied over a wide range of applications from approximately 3μ thin films to 150μ thick films. Particularly effective M is a high molecular weight, high density polyethylene film formed with an expansion ratio of 2 to 6.

Effects of the Invention According to the present invention, by using a floating stabilizer that can move up and down, films of a wide range of thicknesses and widths can be coated over a long period of time without being affected by outside temperature or other external disturbances, and the strength of the film can be reduced. It can be manufactured with high quality and high productivity without causing wrinkles or meandering.

EXAMPLES Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 As a raw material, melt index (9 loads at 190°C 2.16) 0.05 r/10 min, density 0.954 t
A high-density polyethylene film grate having a diameter of /d was used, and an inflation film-forming material having an extruder with a screw diameter of 59 IIm and a die with a die diameter of 751111 was used as the film-forming material.

In addition, the temperature setting of the extruder and die was 200℃, the film thickness was 25μm, and the width of each film was 45OW (blow ratio: 3.8
).

The stabilizer was constructed as shown in Figure 1 and was constructed as follows.

Stable body External diameter Height from the die 1st mandrel (fixed) 80mm 85 rim 2nd mandrel (fixed) 80mm 300m1i + flute - and the second mandrel are made of aluminum cracks, about 20111 mm thick, and the outer surface is threaded. A disk with stripes was used.

The first and second floating stabilizers were aluminum discs with a thickness of about 3 mm, each of which was adjusted to have a size that did not change the shape of the expansion region by mounting weights on them. Atmosphere temperature is 20-35℃
The film was continuously molded for 24 hours at a discharge rate of 30 to 9/Hr in a room with varying temperatures. The height of the die υ at the expansion start point at the start of molding is 540n, and under these conditions, the diameter at the expansion start point when the entire stabilizer is not used is 73n.
It was in order. During 24 hours of molding, the starting point of expansion is at least 44
It varied from 01!1 to a maximum of 610 tm. During molding,
Following the vertical movement of this inflation starting point, the floating stable body moved up and down and was located at the same position in the inflation area of the tubular body. When the dart impact strength of the film sampled during this period was measured, it was found to be stable at a minimum of 250 and a maximum of 2902.

Comparative Example 1 In Example 1, as shown in FIG. 2 as a stabilizer,
Stable body made by covering the surface of an aluminum cylinder with felt (
The one closest to the die has an outer diameter of 7511 φ, and the one closest to the take-off side has an outer diameter of 9 Q mm φ, a length of 300111 mm, and is tapered). A film was formed in the same manner.

The height at which the tubular body contacted the stabilizer was 600+i+ at the highest and 450n at the lowest, but if the height of the contact point was less than 4900, the film became unstable and wrinkles occurred.

The appearance of the film was poor. Also, is the dart impact strength of the film at least 160? , the highest value was 2402, which was low and had a large variation.

This is because the diameter of the expansion starting point of the tubular body is forcibly expanded by the fixed stable body, and when the position of the expansion starting point becomes high, the diameter is expanded at the part of the stable body with a large outer diameter. This is because the strength becomes lower.

Example 2 Using the same equipment and conditions as in Example 1, a film was formed with a total thickness of 13 μm and a width of 650 mm (blow ratio 5.5). 27 K9/H at outside temperature 18-30℃
When molding was performed for 24 hours at a discharge rate of r, the height of the expansion starting point at the start of molding from the die was 54 (lf
l, but the maximum weight was 580R1g and the minimum weight was 4
It was 10 minutes. During molding, as the expansion start point rises and falls,
The floating stabilizer automatically follows up and down to maintain film stability,
Both appearance was good.

The dart impact strength was measured by sampling the film as the expansion starting point moved up and down, and it was stable at 120-1502.

Note that the diameter of the expansion starting point when the stabilizer was not used at the start under these film forming conditions was 64 O. Comparative Example 2 In Example 2, the stabilizer was shaped like a cylinder as shown in Stabilizer (the surface is felt, the one closest to the die has an outer diameter of 701
1φ, the one closest to the receiving side has an outer diameter of 80φ and a length of 3001mm.
m). Other conditions are the same as in Example 2.

During molding, the height at which the tubular body contacted the stabilizer was 570 at the highest and 410,111 at the lowest.

During this period, the dart impact strength of the film was low with a minimum of 70 knots and a maximum of 1302 knots, and there was wide variation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main part of the tubular film forming method of the present invention. In the figure, 1 is an annular die, 2 is an air blowing pipe, 3 is a hollow strut, 4 is a first mandrel, 5.11 is an air blowing and circulation dose part, 6 is a ventilation hole, 7 is an air cooling ring, 8
is a tubular body, 9 is a second mandrel, 10.10' is a floating stabilizer, 12 is a weight, 13 is an expansion starting point, 14 is an expansion area, and 15 is a fastener for determining the reciprocating range of the floating stabilizer. be. In Fig. 2, a known cylindrical stabilizer is used and the cylindrical stabilizer is used. Figure 3 shows a film forming method when no devices such as a mandrel or a floating stabilizer are installed inside the tubular body 8. In the figure, 13' indicates the starting point of expansion at that time.

Claims (1)

[Claims] 1. In forming a tubular film by expanding a polyolefin resin tubular body melt-extruded from an annular die by an inflation method while contacting a stable body provided coaxially with the annular die, It is movable up and down along a column coaxial with the annular die, which is placed at an appropriate position in the expansion region above the expansion start point, and the stable support force of the resin tubular body at the contact position is less than or equal to A method for producing a tubular film, characterized in that at least one floating stabilizer having a weight of . 2. When forming a tubular film by expanding a polyolefin resin tubular body melt-extruded from an annular die by the inflation method while contacting a stable body provided coaxially with the annular die, the die and the expansion start point are formed. The resin tubular body is brought into contact with at least one fixed stable body provided at a suitable position between the resin tubular body, and further provided coaxially with the annular die disposed at a suitable position in the expansion region above the expansion starting point. At least one floating stabilizer is movable up and down along the column and has a weight less than the stabilizer supporting force of the resin tubular body at its contact position, and is always attached to a resin tubular body with a diameter equal to the diameter of the floating stabilizer. A method for manufacturing a tubular film, which comprises expanding the resin tubular body while contacting and following the position of the resin tubular body.