JPH0363498B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for eliminating slack in stretched films such as synthetic paper and cigarette packaging films. [Prior Art] A base film of polypropylene is longitudinally stretched at a temperature lower than the melting point of the polypropylene by utilizing the peripheral speed difference between the roll groups, and then a film having a melting point lower than that of the polypropylene is applied to the surface of the stretched base film. A low melt propylene-ethylene copolymer or polyethylene film is extruded and laminated, and then stretched laterally using a tenter at a temperature lower than the melting point of the polypropylene base material but higher than the melting point of the laminating resin to form the base material. Low-temperature heat-sealing films in which the layers are oriented and the laminate layers are not oriented are used as packaging films for cigarette boxes and candy boxes. In addition, a base film of polypropylene or polyethylene terephthalate containing inorganic fine powder is longitudinally stretched, then polypropylene or polyethylene terephthalate containing inorganic fine powder is extruded and melt-laminated on the surface of this longitudinally stretched film, and then the base resin is It is also known to produce synthetic paper in which both the base layer and the laminate layer are oriented by transversely stretching the paper using a tenter at a temperature lower than the melting point of the laminate resin (Japanese Patent Publication No. 40794/1983,
48-8581). Furthermore, oriented films made by biaxially stretching resin films such as polyethylene terephthalate, polyvinyl chloride, and mixtures of polypropylene and polyethylene containing fine inorganic powders are also known (Japanese Patent Publication No.
−31032). Stretched films with these orientations are usually heat-treated (annealed) by passing through an oven set at a temperature close to the melting point of the resin after completing transverse stretching using a tenter, and then guided into a cooling furnace and cooled. It is usually cooled with air, then rolled up after slitting the ears. In the production of these stretched films, it is extremely difficult to maintain a uniform temperature inside the tenter oven, so the heaters at both left and right ends of the oven are set higher than the central heater, and air is sucked into the center of the film. Stretching is performed by attaching the film to the oven so that the temperature distribution inside the oven is uniform, but it is not possible to make the temperature the same on the left, right, and center sides of the oven. As can be understood from the heat shrinkage of the stretched film shown in the figure, the degree of orientation is different, so the wound roll of the stretched stretched film has different sagging parts, portions, and winding diameters in the width direction as shown in Figure 2. Become something,
It is inconvenient to store. Furthermore, when cutting a stretched film such as a low-temperature sheet seal film or synthetic paper into a sheet, problems may arise in dimensional accuracy. The cause of the slack in the winding diameter of the stretched film is as follows:
This is due to the non-uniformity of the temperature distribution within the tenter oven as well as the non-uniformity of the temperature within the cooling furnace. In particular, in the cooling furnace, the cooling efficiency at both ends of the film decreases due to the gripping tool for the film which is heated after passing through the stretching zone and the annealing zone, resulting in a high film temperature. Therefore, the film has an uneven temperature distribution in the width direction. That is, if the stretched film is cooled under uniform cooling conditions in the width direction, there will naturally remain non-uniformity in temperature distribution of the stretched film in the tenter oven and during cooling. Therefore, if the shrinkage stress of the film due to the pulling stress is greater in the portion of the stretched film that is at a higher temperature than in the portion of the stretched film that is at a lower temperature, this causes shrinkage and sagging. On the other hand, if the take-off stress is greater than the film shrinkage stress, the film will elongate, but normally, increasing the take-off stress increases the residual stress in the wound film, which increases the sagging over time, so this is preferable. do not have. [Specific means for solving the problem] In the present invention, the material is laterally stretched by a tenter,
In cooling the annealed stretched film with cooling air, a duct is used in which the chamber of the duct for discharging the cooling air is divided into a plurality of independent chambers, and the divided chambers correspond to the high temperature parts of the stretched film. By increasing the amount of cooling air discharged from the room, the parts of the stretched film are cooled more quickly, and the amount of cooling air discharged from the compartments corresponding to the lower temperature parts of the stretched film is reduced. This is to prevent sagging by making the temperature distribution of the cooled stretched film as uniform as possible by cooling such portions of the stretched film slowly. The temperature distribution of this stretched film may vary depending on the temperature setting conditions and operating conditions of the tenter oven and annealing furnace, so the positions of high temperature and low temperature areas may shift. Use. That is, the present invention provides a cooling method in which cooling air discharged from a plurality of ducts arranged above and below the resin film is blown onto the front and back surfaces of the thermoplastic resin film to lower the temperature of the resin film.
(A) The plurality of ducts are arranged in parallel in a direction perpendicular to the direction in which the resin film is sent out, and each duct room is divided into a plurality of independent chambers, Each of these divided rooms is connected to the divided rooms of the adjacent duct by a conduit, and (B) the amount of cooling air sent to the duct is controlled by a valve (damper) in the direction in which the resin film is sent out. The present invention provides a method for cooling a thermoplastic resin film, which is characterized in that a desired discharge amount is adjusted and discharged for each partitioned room arranged in a row. Examples of the thermoplastic resin for the film material include polypropylene, polyamide, polyethylene terephthalate, polyethylene, polyvinyl chloride, and polystyrene. These resins include talc,
It may also contain inorganic fine powders such as calcined clay, calcium carbonate, titanium oxide, etc., heat stabilizers, lubricants, antistatic agents, ultraviolet absorbers, and the like. Stretching is carried out in the longitudinal direction using the difference in circumferential speed of the roll groups.
7 times, and 4 to 12 times in the lateral direction using a tenter. The stretching temperature is 150-162°C for polypropylene having a melting point of 164°C, and 108-125°C for polyethylene terephthalate having a melting point of 264°C. Next, a cooling furnace used in the present invention will be explained using the drawings. Fig. 1 is a top view of the ducts 2, 2,... provided at the bottom of the resin film 1 in the cooling furnace, Fig. 4 is a front view of the cooling furnace, and Fig. 5 is a perspective view of the ducts. . In the figure, 3 is an outdoor air inlet, 4 is an indoor air inlet, 5 is a damper (moderation valve), 6 is a blower, 7 is a motor, and 8 is a damper connected to the upper ducts 2a, 2a... ,
9 is the main damper connected to the lower ducts 2b, 2b..., 10a is the duct 2 with divided rooms
b ₁ , 2b ₂ , 2b ₃ , 2b ₄ sub-dampers, 11a, 1
1b, 11c, 11d, 11e, 11f, 11
g, 11i are dampers that adjust the amount of cooling air discharged from each of the nine compartments A, B, C, D, E, F, G, H, and I of the branch damper 2b; 12 is a damper for each duct 2b ₁ , 2b ₂ , 2b ₃ , 2b ₄ , which are divided into nine rooms A, B, C, ...I, adjacent to each other (2b ₁ -
A, 2b ₂ -A, 2b ₃ -A, 2b ₄ -A) (2b ₁ -B,
2b ₂ -B, 2b ₃ -B, 2b ₄ -B), ... (2b ₁ -
I, 2b ₂ - I, 2b ₃ - I, 2b ₄ - I) A conduit connecting the two, 13 is a manometer that reads the pressure of the cooling air discharged from the room, 10b is a duct 2b ₅ in which the room is not divided, 2b ₆ , 2b ₇ , 2b ₈ are sub-dampers that adjust the discharge amount of cooling air; 14 is an infrared thermometer movable in the width direction of the film; 1
5 and 16 are film gripping tools, 16 is an infrared thermometer that reads the temperature, and dampers 11a, 11b, . . .
...Converter that instructs the opening and closing of the damper of 11i, 1
7 is a VVVF inverter that receives information from the converter 16 and can convert the rotation speed of the motor 7, and 18 is a casing of the cooling furnace. In addition, in FIG. 1, 19 is a stretched resin film annealing processing furnace;
Reference numeral 20 denotes a nozzle that blows cooling air onto the edges of the film, and the resin film is transferred from the annealing furnace side into the cooling furnace by rotating the chain to hold the gripping tool 1.
Sent by 5. In FIG. 1, a portion of the resin film is shown by a phantom line at the outlet of the cooling furnace to help understand the width of the resin film. An operating method for producing a resin film with little sagging using such a cooling furnace will be described below. Resin film 1 horizontally stretched in a tenter oven
is heat-treated in an annealing furnace 19 (in some cases, it may be designed integrally with a tenter oven furnace) at a temperature 5 to 10 degrees Celsius higher than the drawing temperature, and then sent to a cooling furnace where it is heated at 20 to 10 degrees Celsius. It is cooled by cooling air to a temperature of about 60℃. Inside the casing 18 of the cooling furnace is a resin film 1.
Eight pairs of ducts 2 are placed vertically in parallel to the flow direction of the resin film (direction of the arrow in Figure 1), 20 to 40 cm apart from the film surface, and parallel to each other, with an interval of 30 to 100 cm between each duct. Of these ducts 2, 4 which are closer to the annealing processing furnace 19
The paired upper and lower ducts 2b ₁ , 2b ₂ , 2b ₃ , 2b ₄ are divided into nine rooms A, B, C, ... I, and each room of each duct (approximately 40 cm long) is divided into nine rooms A, B, C, ... I. )
are connected to adjacent chambers by conduits ₁₂ , and _the same compartment symbols A, A, _A , A, _B , B, B,
The amount of cooling air discharged from the chambers having B, . . . I, I, I, I is designed to be approximately the same. Four pairs of ducts 2b ₅ , 2b ₆ , 2 on the outlet side of the cooling furnace
b ₇ and 2b ₈ are cooled so that the temperature distribution in the width direction of the resin film 1 is uniform in the four pairs of ducts 2b ₁ , 2b ₂ , 2b ₃ , and 2b ₄ , so the temperature distribution in the latter four pairs of ducts is The rooms are not divided. Note that if the temperature distribution in the film width direction is not uniform among the former four pairs of ducts, the number of ducts having partitioned chambers is increased. Therefore, it may be possible to completely replace the duct with a divided chamber. The cooling air can be either outdoor air, indoor air, or both. In summer, the temperature inside the factory building is high, so it is better to draw air from outside through the suction port 3, and in winter, when the temperature of the outside air is too low, it is better to suck indoor air through the suction port 4. Of course,
If the factory building is equipped with air conditioning equipment and the temperature inside the building can be kept constant, it is better to use indoor air. The sucked air is sent through the main damper 8 by the blower 6, to the upper duct 2 by a pipe, and then to the lower duct 2 through the main damper 9. A part of the air is guided from the annealing furnace 19 to the nozzle 20 that cools the edge of the resin film 1 moving to the cooling furnace. The cooling air that has passed through the main dampers 8 and 9 further passes through sub-dampers 10a and 10b, and one passes through branch dampers 11a, 11b...11i and is divided into ducts 2b ₁ , 2b ₂ , 2b ₃ , 2b ₄ Cooling air is sent to the chambers A, B, . . . The other air is supplied through ducts 2b ₅ , 2b ₆ , 2b ₇ , 2 in which the rooms are not divided.
b ₈ and is sprayed onto the resin film 1 from the discharge port. For example, the temperature of the resin film may be 160°C in the annealing furnace, but it may be 30°C at the exit of the cooling furnace.
Cooled to ~50°C. The amount of cooling air discharged from the ducts 2b ₁ , 2b ₂ , 2b ₃ , and 2b ₄ is determined by moving the infrared thermometer 14 in the width direction of the film on a rail (not shown), and measuring the temperature of the film in the cooling furnace. On the other hand, before winding the film, marks (a, b,...
...i) from the surface of the film with a drafting needle
Drill a hole large enough for ~4 sheets to pass through, read the distances la, lb,, lc...li between these marks in the film flow direction, and if the distance l between the marks is shorter than the average value, the hole in the duct corresponding to the film position is read. In order to increase the amount of air discharged from the divided chambers, the opening degree of the corresponding branch damper (valve) is increased so that the cooling of that part of the film is equal to the cooling of other parts of the film. do. On the other hand, if the interval l is longer than the average value, the opening degree of the corresponding branch damper valve is reduced in order to reduce the amount of air discharged from the divided chamber of the duct corresponding to the film position. , so that the cooling of that part of the film is comparable to the cooling of other parts of the film. The amount of air discharged from each room can be understood from the air pressure recorded on the manometer 13.
Regarding the interval 1 between the marks, the long portions and short portions do not always appear at the same location in the width direction. That is, the position may shift due to changes in the amount of air discharged from each of the rooms,
Furthermore, the temperature distribution of the heated air within the tenter oven may change depending on the operating conditions. Therefore, it is preferable to track this interval l at as short time intervals as possible, but always monitor the film temperature distribution in the cooling furnace using infrared rays so that the fluctuation of l is within the smallest numerical range possible. It is preferable to read the discharge pressure of the cooling air from each chamber with a thermometer and a manometer at any time, and operate so that the difference in temperature distribution of the film and the difference in discharge pressure are as small as possible. The resin film, whose temperature distribution has become almost uniform due to the air blown out from the ducts 2b ₁ , 2b ₂ , 2b ₃ , and 2b ₄ , is further heated to room temperature by the air blown out from the ducts 2b ₅ , 2b ₆ , 2b ₇ , and 2b ₈ . It is cooled to a temperature of about 55°C that can be rolled up, then the edges are slit and rolled up. (Effects) The resin film obtained by implementing the present invention is
There is little sagging, and the distribution of the winding diameter in the width direction of the wound film is uniform, which is advantageous for storage. Also, printing is performed with high precision. Reference example Polypropylene “Noblen MA” manufactured by Mitsubishi Yuka Co., Ltd.
-6” (product name) 90 parts, high-density polyethylene “Yukalon Hard EY-40” manufactured by Mitsubishi Yuka Co., Ltd. (product name)
100 parts, 15 parts of clay, 0.3 parts of antioxidant, and oleic acid "Lunatsuku" manufactured by Kao Soap Co., Ltd. as a dispersant.
(Product Name) A composition consisting of 0.1 part was melted and kneaded using an extruder, extruded from a die at a temperature of 200°C into a sheet, and the sheet was cooled to about 50°C. Next, after heating this sheet to about 150℃,
The film was stretched 4 times in the longitudinal direction by utilizing the difference in peripheral speed between the roll groups. Separately, polypropylene (Mitsubishi Noblen MA-
6) A composition containing 100 parts of clay, 80 parts of clay with an average particle size of 1.5μ, 10 parts of titanium oxide with an average particle size of 1μ, 0.2 parts of an antioxidant, and 0.1 part of oleic acid was prepared using two other extruders. The laminated film is melt-kneaded using a die and laminated on both sides of the longitudinally stretched sheet at a temperature of 250°C into a sheet, and once cooled to a temperature 20°C higher than room temperature, the laminated film is placed in a tenter oven ( Temperature distribution is 175℃ at the edges and 170℃ at the center.
The film was then reheated to about 155°C, stretched 8 times in the transverse direction using a tenter, and then passed through a heat treatment oven at 160°C for heat setting. After cooling the edges of the heat-set stretched film with cooling air, the stretched film was introduced into a cooling furnace having eight pairs of ducts as shown in Fig. 1, and the discharge pressure of the cooling air from each duct was set to 40 mmAq. At the same time, the resin film was cooled to 45°C with cooling air, and then the edges were slit, and the stretched film was
I wound up 500m. This stretched film has a biaxially stretched intermediate layer (base material layer) with a thickness of 70 μm, a front and back layer of uniaxially stretched films with a thickness of 10 μm each, a three-layer structure with a width of 300 cm, and excellent writability. It was a white stretched film. The apparent density of this three-layer film is 0.78
g/cc, and many fine voids were formed in both the base layer and the front and back layers. In addition, many fine cracks were observed on the surfaces of the front and back layers. When the winding diameter of this white stretched film was measured every 20 cm, the distribution was as shown in Table 1, indicating that there was some slack. The temperature distribution of the stretched film passing under each compartment of the duct and the length (l) of the marks attached to the stretched film at a given time in the flow direction are as shown in Table 2. It was hot. Example In Reference Example, a stretched film having the winding diameter distribution shown in Table 1 was obtained in the same manner as in Reference Example except that the discharge pressure of the cooling furnace was changed as shown in Table 2. The temperature distribution of the stretched film during production and the length (l) of the marks attached to the stretched film were as shown in Table 2.

[Table] * Upper left end
Measured from the bottom
Bottom right end

【table】 [Brief explanation of drawings]

FIG. 1 is a top view of a cooling furnace in which the present invention is implemented. FIG. 2 is a perspective view showing a state in which a conventional stretched film is wound. FIG. 3 is a diagram showing the thermal shrinkage rate of the stretched film in the film feeding direction, which was measured by leaving the stretched film obtained in the reference example at 120° C. for 2 hours. FIG. 4 is a front view of the inside of the cooling furnace, and FIG. 5 is a perspective view of the upper part of the inside of the cooling furnace. FIG. 6 is a partial perspective view of the marked stretched film. In the figure, 1 is a film, 2 is a duct, A, B,
C, D, E, F, G, H and I are divided chambers of the duct, 11 is a damper, and 12 is a conduit connecting the divided chambers.

Claims (1)

[Claims] 1. A cooling method in which the temperature of a thermoplastic resin film is lowered by blowing cooling air discharged from a plurality of ducts arranged above and below the resin film onto the front and back surfaces of the resin film, A) The plurality of ducts are arranged in parallel in a direction perpendicular to the direction in which the resin film is sent out, and the chambers of each duct are divided into a plurality of independent chambers, and Each of these divided rooms is connected to the divided rooms of the adjacent duct by a conduit, and (B) the discharge amount of cooling air sent to the duct is controlled by a valve in a line arranged in the direction in which the resin film is sent out. 1. A method for cooling a thermoplastic resin film, which comprises adjusting and discharging a desired discharge amount for each divided room. 2. The cooling method according to claim 1, wherein each duct is divided into nine rooms. 3. The cooling method according to claim 1, wherein four pairs of ducts are provided above and below the resin film. 4. The cooling method according to claim 1, wherein the amount of cooling air discharged from the divided chambers of the duct is controlled by opening and closing a valve based on reading the pressure of a manometer. 5 The amount of cooling air discharged from each partitioned chamber of the duct increases from the central chamber toward the chambers at both left and right ends. Cooling method. 6. The cooling method according to claim 1, wherein each duct is installed in a cooling furnace together with a resin film. 7. The cooling method according to claim 1 or 6, wherein the thermoplastic resin film is a stretched film. 8. The cooling method according to claim 7, wherein the cooling furnace is provided after the furnace for heat-treating the resin film that has been laterally stretched using a tenter. 9. Claims characterized in that the temperature of the film passing through the final part of the divided duct in the cooling furnace is uniform in the center and both ends, or that both ends are 1 to 10 degrees Celsius lower than the center. Section 5 or 6
Cooling method described in section.