JP2000334749A - Method for treating circulating high temperature air of oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for purifying circulating high temp. air in a high temp. state by positively oxidizing an evaporated substance generated in circulating hot air not only to prevent such a phenomenon that the evaporated substance is solidified or liquefied to adhere to the surfaces of the inner wall, floor, pillar or machinery of an oven but also to eliminate the contamination of a stretched film being a product with a peeled accumulated adherend or danger generating the point at issue from an aspect of the lowering of the mechanical capacity and maintenance of an apparatus caused by the accumulated adherend, dispensing with a post-treatment equipment required in the prior art and capable of achieving the facilitation of production and operation, the reduction of production cost, the conservation of energy and the prevention of air pollution and environmental pollution. SOLUTION: In a circulating hot air type heating oven used in the processing of a thermoplastic resin, high temp. air being a part of circulating hot air is guided to a heat accumulation type combustion device 19 and the evaporated matter in hot air is oxidized and decomposed to clean the circulating high temp. air of the circulating hot air type heating oven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tenter for producing a stretched resin film such as a biaxially stretched polypropylene film (BOPP), a biaxially stretched polystyrene film (BOPS), or synthetic paper, or a general thermoplastic resin. The present invention relates to a circulating hot air heating oven used for stretching.

[0002]

2. Description of the Related Art Various types of thermoplastic resin molded films are prepared by, for example, stretching an extruded film in the longitudinal direction using a difference in peripheral speed of a group of heating rolls, and then stretching the film in a horizontal direction using a tenter or the like in a heating oven. It is manufactured by drawing into heat, cooling and winding the product if necessary. An apparatus for producing synthetic paper by applying a similar process is also disclosed in Japanese Patent Publication No. 46-40794. Further, on the surface of the longitudinally stretched polypropylene film, a hot-melt film of a propylene / ethylene copolymer having a lower melting point than the polypropylene is laminated, and the laminated product is heated at a temperature lower than the melting point of the polypropylene using a tenter. Also known is a method for producing a low-temperature heat-sealing film which is stretched in a heating oven in a horizontal direction in a temperature range higher than the melting point of the copolymer and then heat-treated and used for packaging of cigarette boxes, confectionery boxes and the like. ing.

[0003] As a tenter oven used for these, a circulating hot air heating oven is generally used. As shown in FIG. 1, one unit constituting the circulating hot-air heating oven is composed of a return circulation duct 1, a circulation blower 2, a heat exchanger 3, a going circulation duct 4, a blowing nozzle 5, and the like. A part of the outside air intake 6
And a circulating hot air outlet 7 is provided in a part of the outgoing circulation duct 4. Upper and lower blowing nozzles 5
The film to be heated 10 is running between the two. The outside air intake 6 and the circulating hot air outside air outlet 7 are respectively provided with throttle mechanisms 6-1 and 7-1 of a butterfly type or the like capable of appropriately adjusting the air volume. In general, the outflow circulation duct 4 is also provided with a throttle mechanism 4-1 for controlling the amount of circulating air. Similarly, the return circulation duct 1 is also provided with a throttle mechanism 1-1 for controlling the air volume. In addition, a filter may be installed in the outside air intake 6.

[0004] The set temperature of the circulating hot air required for the manufacturing and processing operation is accurately maintained by controlling the heat exchanger 3 by a signal from a temperature sensor installed in the outgoing circulation duct 4 and a control device. The heat exchanger 3 uses a heat source of electricity, steam, or another heat medium. The circulating hot air is blown by the circulating blower 2 through the circulating duct 4 and blown out from the blowing nozzle 5 upward and downward of the running film 10 to be heated, thereby heating the film 10 to be heated. The heated circulating hot air is recovered, passed through the return circulation duct 1, and sequentially circulated while being again controlled to the set temperature in the heat exchanger 3 by the circulation blower 2.

[0005] With the above configuration and operation, units of appropriate length are installed in each of the preheating, stretching, heat setting, and cooling zones, for example, for each set temperature and air flow required for the manufacturing process. Constitutes a circulating hot air oven. Therefore, the units installed in each zone and for each zone have basically the same configuration. Each of the circulating hot air outlets 7 in each unit is provided for each unit to guide the circulating hot air to the outside and discharge it to the outside air, or a plurality of circulating hot air outside air outlets 7.
In some cases, the circulating hot air is discharged to the outside air by connecting the components as appropriate to form an exhaust chimney duct. The outside air intake 6 can be taken in from each unit or from one common duct.

In the above prior art, a film is formed from a thermoplastic resin having various additives contained therein, and if necessary, a coating agent such as an antistatic agent is applied to the surface of the film. When the film is introduced into a heating oven and stretched in the horizontal direction while heating, various additives and coating agents are constantly mixed and sublimated into the circulating hot air from the stretching surface of the film to be introduced, and the circulating hot air circulates. As they continue to drive for long periods of time,
The concentration rises and solidifies or liquefies and deposits on the surfaces of oven walls, floors, columns, equipment, etc., which tend to be at temperatures lower than the circulating hot air. In order to suppress the phenomenon as much as possible, a considerable amount of new air is always taken in from the outside air intake 6 and dirty circulating hot air is taken out from the circulating hot air outside air outlet 7 to the outside air for the purpose of diluting the vaporized substance concentration of the circulating hot air. Discharge, or collect this dirty hot air and pass it through a water scrubber, catch it with an electrostatic precipitator or filter,
It is common to prevent contamination to the outside air by directly burning or the like.

[0007] However, in the above prior art, it is not a desirable method from the viewpoint of manufacturing cost, energy saving, air pollution, pollution, and the like, to directly discharge the circulating hot air having a high temperature and containing a vapor to the outside air. In addition, technically, it is a method of constantly diluting the circulating hot air with clean outside air having a relatively low temperature to reduce the vaporized material concentration of the circulating hot air and reduce the accumulation of deposits. If the balance of the outside air intake based on different types of production items, production operation conditions, etc. is disrupted, there is a concern that this deposited matter will increase and it will peel off and stain the stretched film which is the product. In addition, there is always a problem of a decrease in mechanical performance of the apparatus and a problem in maintenance due to a small amount of deposits.

Accordingly, in some cases, the inner wall of the oven,
By observing the state of solidification or liquefaction deposition on the surfaces of floors, columns, equipment, etc., subtle and troublesome operations such as adjusting the amount of outside air to be taken in and the amount of circulating hot air to be discharged are performed. In addition, the production cost is increased and the heat energy loss is further increased, and direct release to the outside air may adversely affect air pollution. Even if not directly discharged to the outside air, the post-treatment equipment had problems with the treatment due to solidification or liquefaction deposits similar to those in the oven

[0009]

SUMMARY OF THE INVENTION According to the present invention, a part of the circulating hot air is guided to a regenerative combustion device, and vaporized substances in the hot air are oxidized and decomposed to purify the circulating high-temperature air in a circulating hot air heating oven. A method for treating circulating high-temperature air in an oven characterized by purifying circulating high-temperature air at a high temperature by positively oxidizing and decomposing vapors generated in circulating hot air, which could not be solved by the prior art. To prevent solidification or liquefaction from adhering to the surfaces of oven inner walls, floors, pillars, equipment, etc., and the deposited material is peeled off to contaminate the stretched film as a product, Eliminates the risk of performance degradation and maintenance problems, and eliminates the need for post-processing equipment required by conventional technology, facilitating production operation, reducing production costs, saving energy, preventing air pollution, and preventing pollution. Achievable processing method is to provide a.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a circulating heating oven used for processing a thermoplastic resin, in which a part of the circulating hot air is guided to a regenerative combustion device to oxidize and decompose a vapor in the hot air. This is a method for treating circulating high-temperature air in a tenter oven, in which the circulating high-temperature air in a circulating hot-air heating oven is sequentially purified, and a method for recirculating and using the cleaned high-temperature air again.

[0011]

In the prior art processing of a thermoplastic resin film, when the film is guided into a circulating heating oven and horizontally stretched while being heated, it is blended into the circulating hot air from the stretched surface of the film. As the additive is constantly mixed with sublimation vaporization and the continuous operation for a long time, the concentration of the sublimated vapor in the circulating hot air increases, and the circulating hot air is gradually contaminated. It solidifies or liquefies and deposits on the surfaces of the oven walls, floors, pillars, equipment, etc. at lower temperatures. To suppress this phenomenon, a considerable amount of clean outside air had to be always taken in for the purpose of diluting the concentration of vaporized substances in the circulating hot air.

In the present invention, a portion of the circulating hot air is guided to a regenerative combustion device, and vaporized substances in the hot air are constantly oxidized and decomposed, and then returned to the circulating hot air, thereby sequentially circulating the circulating hot air heating oven. It is intended to actively purify hot air, and it can release dirty circulating hot air to the outside air,
No more outside air than necessary. In addition, if the operating conditions of the circulation type heating oven side cause fluctuations in the pressure of the circulating high-temperature air going circulation duct to affect the wind speed of the blow-out nozzle, part of the circulating hot air to be taken out is mixed with outside air once under atmospheric pressure. After that, it is led to a regenerative combustion device and oxidized and decomposed, and then returned to circulating hot air or released to the outside air after treatment, thereby reducing the pressure fluctuations affecting the wind speed and wind speed distribution of the blowing nozzle on the circulating heating oven side. Can be eliminated. In addition, it is possible to recover the heat of oxidation of the contaminated circulating hot air and the condensed circulating hot air by the heat storage material of the regenerative combustion device. Losses are also drastically reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Thermoplastic resin] As the thermoplastic resin used for processing a thermoplastic resin film, polypropylene, polyamide, polyethylene terephthalate,
Examples include polyethylene, polyvinyl chloride, polystyrene, and polycarbonate. To these resins, inorganic fine powder, organic fine powder, stabilizer, light stabilizer, dispersant, lubricant and the like can be added. As the inorganic fine powder, the particle size is usually 0.01 to 15 μm, preferably 0.0
1-5 μm is used. Specifically, calcium carbonate, calcined clay, silica, diatomaceous earth, talc, titanium oxide, barium sulfate, alumina and the like can be used.

As the organic fine powder, it is preferable to select a fine powder of a resin different from the thermoplastic resin as the main component. For example, when the thermoplastic resin film is a polyolefin resin film, the organic fine powder may be polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, nylon-6, T, cyclic olefin. ,
It is a polymer such as polystyrene or polymethacrylate, and has a melting point (for example, 170 to 300 ° C.) higher than the melting point of the polyolefin resin or a glass transition temperature (for example, 1).
(70 to 280 ° C.).

When a stabilizer is added, usually 0.001
It is added within the range of １1% by weight. Specifically, sterically hindered phenol-based, phosphorus-based, amine-based stabilizers and the like can be used. When using a light stabilizer, usually 0.0
It is used in the range of 01 to 1% by weight. Specifically, light stabilizers such as sterically hindered amines, benzotriazoles, and benzophenones can be used. The dispersant and the lubricant are used, for example, for the purpose of dispersing the inorganic fine powder.
The amount used is usually in the range from 0.01 to 4% by weight. Specifically, silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid or salts thereof can be used.

The thermoplastic resin film to be processed has a single-layer structure or a two-layer structure including a base layer and a surface layer.
It may have a three-layer structure in which a surface layer exists on the front and back surfaces of the base layer, or may have a multilayer structure in which another resin film layer exists between the base layer and the surface layer. It may contain 100% by weight and 0 to 60% by weight of inorganic and / or organic fine powder. As the thermoplastic resin film to be processed, for example, inorganic and / or
Alternatively, a polypropylene-based synthetic paper containing an organic fine powder and a polyester-based synthetic paper may be used. These polypropylene-based synthetic papers and polyester-based synthetic papers may contain pores generated by inorganic and / or organic fine powder contained during stretching.

[Oven temperature] In the case of a tenter oven, the temperature required for the thermoplastic resin film to be heated and cooled is, for example, 120 to 160 ° C. in the heating and stretching zone and 30 to 50 ° C. in the cooling zone. . In the case of polycarbonate or polyamide (nylon 6), the stretching heating zone in a tenter oven is in the range of 100 to 130 ° C, and the cooling zone is in the range of 30 to 80 ° C.

[Definition of VOCs] VOCs (volatile organic compounds) are all organic compounds developed by humankind except for methane, unless otherwise specified in the definition of the ECE (United Nations Economic Commission for Europe). In addition, it refers to a chemical substance that can generate a photochemical oxidant by undergoing a photochemical reaction with nitrogen oxides under sunlight. Since VOCs vary widely depending on the generation source, various types of processing apparatuses have been developed so as to be compatible with the conditions.

[Regenerative combustion device] A regenerative combustion device heats a processing gas to a high temperature and oxidizes and decomposes it into harmless carbon dioxide and water to produce a clean gas. This is a well-known combustion apparatus which can process at low fuel consumption by increasing the heat exchange rate to 85 to 95% by using the same. Various types of devices have been developed and sold, but the basic principle is that it is equipped with three towers filled with heat storage material, and the circulating hot air guided from the circulating hot air heating oven is first discharged by a valve.
At the top of the tower, through the heat storage chamber of the tower, there is a combustion device at the top of the tower to keep the startup temperature and combustion temperature constant, and gas or high-quality heavy oil is used as the fuel. At the top of the tower, the hot air is heated and burned above about 800 ° C,
After the vaporized matter is completely oxidized and decomposed, the clean hot air is exchanged with the heat storage material and discharged while descending the second tower. Next, the circulating hot air guided from the circulating hot air heating oven is switched by a valve by a timer, ascends the second tower, obtains heat from the heat storage material, reaches the top of the tower, and similarly reaches about 800 ° C. or more. After being heated and completely oxidizing and decomposing the vaporized material, the gas is discharged by exchanging heat with the heat storage material in the third column. At this time, the original circulating hot air remaining in the first tower (a tower in which the circulating hot air has already been heated and burned) is expelled to the top of the tower by fresh air, all of which are completely heated and burned, and newly supplied. Prepare to process the circulating hot air. Next, after the circulating hot air is led to the third tower and heated and burnt at the top of the tower,
The clean hot air undergoes heat exchange in the first tower and is discharged to the outside.
This operation is switched and processed one after another.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Example 1) A polypropylene-based synthetic paper containing an additive-containing inorganic fine powder having a thickness of about 60 μm was prepared at 150 m / m
In the unit immediately after the stretching of the tenter oven manufactured in “in”, the circulating air volume is set to 20 m ³ / min, the circulating hot air temperature is set to 120 ° C., and the outside air of about 1 m ³ / min is supplied from the outside air inlet 6 of the return circulation duct 11. For the operating conditions in the prior art, in which the same amount of circulating hot air of about 1 m ³ / min is discharged into the atmosphere from the inlet 7 and the circulating hot air outside air outlet 7, a unit as schematically shown in FIG. 2 is used. ,
Throttling mechanism 7 that reduces the amount of circulating hot air released into the atmosphere
-1 was adjusted and sucked by the blower 18 and led to the regenerative combustion device 19, where the vaporized material in the hot air was 850 ° C. at the top of the tower.
After oxidizing and decomposing the circulating hot air to purify the circulating hot air, a continuous circulating operation was performed while returning to the outside air inlet 6 of the circulating hot air return circulation duct 11 of the circulating hot air heating oven instead of the outside air performed in the conventional technology.

Inlet 1 of the regenerative combustion device during its continuous operation
The hot air temperature and VOC measurement values at 9-1 and the outlet 19-2 were as follows. Inlet Outlet Hot air temperature (° C) 117 ° C 80 ° C Total VOC concentration (mg / Nm ³ ) 60 1.0 Total VOC removal rate 98.3% As a result, the conventional technology releases polluted circulating hot air to the atmosphere Although the VOC concentration of the circulating hot air was suppressed by taking in the outside air at the same time as the above, in this embodiment, the polluted circulating hot air was discharged to the atmosphere and VOC removal was continuously performed without taking in the outside air. Thus, newly vaporized VOCs from the additive-containing fine powder-containing polypropylene synthetic paper that has been produced are made into a circulating hot air that is sequentially cleaned, and high-quality synthetic paper can be produced. Prevents solidification or liquefaction from adhering to the surface of pillars, equipment, etc., and the deposited material is peeled off to contaminate the stretched film, which is a product, or to be used as a machine for the device by the deposited material Reducing ability, maintenance on the problem is gone.

(Embodiment 2) In this embodiment, a part of the circulating hot air in a circulating hot air heating oven and outside air are mixed under atmospheric pressure, and the mixture is guided to a regenerative combustion device 19 by a blower 18 and vaporized in the circulating hot air. This is an embodiment in which a portion of the clean air is returned to the outside air intake 16 of the return circulation duct 11 of the circulating hot air heating oven again after the oxidative decomposition of the air, and the remaining portion is discharged to the outside air.

That is, a unit as shown in FIG. 3 is used to circulate in a stretching unit of a tenter oven for producing polypropylene synthetic paper containing inorganic fine powder having a thickness of about 60 μm at a rate of 150 m / min. The air volume was set to 20 m ³ / min, the circulating hot air temperature was set to 120 ° C., and about 1.2 m ³ / min from the circulating hot air outlet 17.
Once circulated hot air is released into the atmosphere, and then mixed with the outside air under atmospheric pressure as shown in the figure, and blower 1 is mixed with approximately the same amount of outside air.
After being sucked by 8 and led to the regenerative combustion device 19, the vaporized matter in the hot air is oxidized and decomposed at 850 ° C. at the top of the tower to purify the circulating hot air, and then about 50% of the processing amount is released to the outside air. A continuous circulation operation was performed while returning the circulating hot air of the circulating hot air heating oven to the outside air intake 16 of the return circulation duct 11 by about 1.2 m ³ / min. The respective predetermined airflows were measured by the throttle mechanisms 16-1, 6-1, 17-1, and 7-1. Inlet 19-1 in regenerative combustion device during continuous operation
And the VOC measurement values at the outlet 19-2 were as follows. Inlet Outlet Hot air temperature (° C) 55 ° C 104 ° C Total VOC concentration (mg / Nm ³ ) 71 0.54 Total VOC removal rate 99.2%

That is, in the prior art, the VOC concentration of the circulating hot air was suppressed by taking in fresh outside air while discharging the contaminated circulating hot air to the outside air. While returning the circulating hot air to the circulation hot air return oven of the circulating hot air heating oven to the circulation duct 11 and releasing the remaining part to the atmosphere to purify the VOC of the circulating hot air of the circulating hot air heating oven. As in Example 1, the circulating hot air in the circulating hot air heating oven could be cleaned.

In addition to the above-described embodiments, the present invention leads to a regenerative combustion device which discharges polluted circulating hot air into the atmosphere as it is while taking in outside air, which is a conventional technology.
A method of purifying the circulating hot air by oxidizing and decomposing the vaporized material in the hot air at the top of the tower to release the circulating hot air to the outside air. It can also be applied to the method of suctioning with a blower while mixing under atmospheric pressure, leading to a regenerative combustion device, and oxidizing and decomposing vapors in the hot air at the top of the tower to clean the circulating hot air and release all of it to the outside air .

[0026]

According to the present invention, a part of the circulating high-temperature hot air is guided to a regenerative combustion device, and vaporized substances in the hot air are oxidized and decomposed to purify circulating high-temperature air in a circulating hot-air heating oven. It is a method of treating circulating high-temperature air in a tenter oven, which purifies circulating hot air at a high temperature by actively oxidizing and decomposing vaporized substances in circulating hot air, which could not be solved by the conventional technology. It is possible to process high-quality products in a clean atmosphere, prevent vaporized substances from solidifying or liquefying on the surfaces of oven inner walls, floors, pillars, equipment, etc. This eliminates the danger that the stretched film, which is the product, is contaminated or the mechanical performance of the device deteriorates due to deposits, and that there is no maintenance problem. Ko Down, energy conservation, air pollution, pollution prevention can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a unit used in the prior art.

FIG. 2 is a schematic view of a unit according to Embodiment 1 of the present invention.

FIG. 3 is a schematic view of a unit according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ・ 11 Return circulation duct 2 Circulation blower 3 Heat exchanger 4 Outgoing circulation duct 5 Blow-out nozzle 6 ・ 16 Outside air intake 7.17 Circulating hot air outside air blow-out port 10 Heated film 18 Blower 19 Thermal storage type combustion device

Claims (3)

[Claims] In a circulating hot air heating oven used for thermoplastic resin processing, a portion of high temperature air of the circulating hot air is guided to a regenerative combustion device, and a circulating hot air is oxidized and decomposed to vaporize the hot air. A method for treating circulating high-temperature air in an oven, comprising cleaning the circulating high-temperature air in a heating oven. 2. In the circulating hot air heating oven,
The circulation of the oven according to claim 1, wherein a part of the circulating hot air is guided to a regenerative combustion device, and vaporized substances in the hot air are oxidized and decomposed, and then recirculated back to the circulating hot air and reused. Hot air treatment method. 3. In the circulating hot air heating oven,
After a part of the circulating hot air is mixed with the outside air under the atmospheric pressure and led to the regenerative combustion device, and after oxidizing and decomposing the vapor in the mixed air,
2. The method for treating circulated high-temperature air in an oven according to claim 1, wherein a part of the circulated high-temperature air is recirculated to outside air and a part of the circulated hot air is recycled.