JPS63170022A - Manufacture of thermoplastic resin foam and manufacture equipment - Google Patents

Abstract

PURPOSE:To make a removing rate of a sublimate favorable and lower the cost of equipment and a thermal energy loss, by a method wherein a hot atmosphere containing the sublimate to be generated at the time of dissolution of a foaming agent is led within a cooler, stuck to a cooling surface through precipitation and the hot atmosphere from which the sublimate has been removed is sent back within a heater. CONSTITUTION:A closed circuit constituted of a suction port 16 of hot atmosphere containing sublimate, a cooler 19 removing the sublimate through cooling and a sending-back port 22 of purifying hot atmosphere is provided within a heater. A suction port 15 is mounted so that the same is situated on both surfaces of a foamable molded material in a period of time from directly before starting of foaming to a time after completion of foaming, and widths of a foamable molded material, the molded material in a foaming process and a foam are of the width of at least half of them respectively. A wall of the cooler 19 is of a jacket structure and cooling water and air are cooled by passing them through the cooler 19. A coil-like cooling pipe 29 is provided within the cooler 19. The sublimate cooled with the wall of the cooler 19 and a cooling surface of the cooling pipe 29 is removed by accumulating on the surface of the same through precipitation. The purifying hot atmosphere after removal of the sublimate is returned within the heater through the sending-back port 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in a method and apparatus for producing a thermoplastic resin foam.

[Prior art]

In order to produce a thermoplastic resin foam, a thermoplastic resin foam molded product containing a pyrolyzable blowing agent is introduced into a heating device, where it is heated and foamed, and then the foam is taken out from the heating device. It is widely practiced. In the production of such foams, an important issue is how to deal with the sublimate generated during foaming, that is, when the foaming agent is thermally decomposed.

In a heating device with relatively good airtightness, the concentration of sublimate within the device increases over time, and crystallized sublimate precipitates and accumulates at lower temperature locations within the device. The nature of the deposited sublimate may be solid or liquid depending on the influence of temperature and moisture. In any case, there is a problem in that these deposited sublimate substances adhere to the surface of the foamable molded article before foaming or during the foaming process, or to the surface of the foamed product after foaming, thereby contaminating the product.

On the other hand, in order to avoid the problems caused by the sublimate mentioned above, a method is known in which an exhaust duct is provided in the heating device to exhaust the sublimate out of the device. If an attempt is made to discharge the heat to the outside, a large amount of the hot atmosphere inside the device will also be discharged at the same time, which will greatly reduce the thermal efficiency of the heating device and lead to an increase in the cost of the product. or,
Since the temperature of the exhaust duct is lower than that of the inside of the heating device, if the inside of the duct becomes dirty over time, crystals of the sublimate will precipitate inside the duct in a relatively short period of time, and the duct will become clogged. This clogging can be resolved by cleaning it, but since it occurs frequently,
It was extremely inefficient. Furthermore, it is undesirable to discharge the sublimate-containing thermal atmosphere directly into the atmosphere from the viewpoint of air pollution.

As a technique for solving the above-mentioned problems, the techniques disclosed in Japanese Patent Publication No. 46-35154 and Japanese Patent Application Laid-Open No. 59-199222 are known. Special Public Service (1977)
Japanese Patent No. 35154 discloses a method in which a wire mesh filter that moves at low speed is provided above the heating device, and the sublimate generated on the filter is attached to the filter and discharged to the outside. However, since this method does not essentially force the sublimate to adhere to the wire mesh filter, it has the drawback that the removal rate (collection rate) of the sublimate is relatively low. As a method to further increase the removal rate, a cooling plate is installed between the going and returning filters, and the sublimate adhering to this cooling plate is dropped onto the filter (first method), and a duct is placed from the top of the filter. The second method is to suck in the hot atmosphere and discharge the sublimate that has passed through the filter to the outside of the device (the second method), and the third method is a combination of these methods in which a cooling pipe is used instead of a cooling plate. Method)
It is shown. Among these methods, the first method requires increasing heating to prevent the temperature inside the device from decreasing.
And filter = 4- The droplet-shaped sublimate that fell on the filter passes through the filter,
There is a disadvantage that it drips onto the infrared lamp below and even onto the surface of the foamed molded article. The second method has the disadvantage that the thermal efficiency of the apparatus is reduced because the thermal atmosphere inside the apparatus is exhausted together with the sublimate to the outside of the apparatus. Since the third method is simply a combination of these methods, it inevitably has the drawbacks of both methods.

Furthermore, in the method disclosed in Japanese Patent Publication No. 46-35154, the filter with sublimate adhering to it is continuously immersed in the water in the tank for cleaning, so the water in the tank is frequently replaced or the water is continuously supplied and drained. If this is not done, the cleaning of the filter will be insufficient and the collection rate of sublimate will be reduced. A large amount of water is required for thorough cleaning. The lower the temperature of the wire mesh filter, the better the sublimate collection rate.On the other hand, it is desirable that the wire mesh filter, which is returned to the equipment after washing, be kept as dry as possible. The sublimate easily dissolves in the water and becomes droplets of sewage that easily fall. Therefore, after cleaning the filter in this method, it is desirable that the device for removing the water droplets adhering to the filter be one that does not simply wipe or blow away the water droplets, but rather performs heating drying. However, heating and drying increases the temperature of the filter, which has the opposite effect of reducing the sublimate collection rate.

Next, in JP-A-59-199222, gas containing sublimate is discharged from a discharge port provided near the upper part of a preheating chamber of a thermoplastic resin foam sheet, and the gas is passed through a pipe to a combustion device. After the sublimate is thermally decomposed by combustion in this combustion device to obtain a gaseous product, this gaseous product is either left as it is or mixed with a gas containing the sublimate, and is then heated to the lower part of the foaming chamber. A method is shown in which the foam is supplied into a foaming chamber from a nearby supply port and used for heating and foaming a foamable sheet, and an apparatus equipped with such equipment is shown.

In this method and apparatus, the sublimate content in the gas is greatly reduced before and after passing through the combustion apparatus, and the removal rate of sublimate in the combustion apparatus is good. However, the gas containing the sublimate is not discharged from the foaming chamber where the sublimate is generated to the combustion equipment, but from the preheating chamber above or in front of the foaming chamber, so the gas containing the sublimate is not discharged from the preheating chamber above or in front of the foaming chamber. Since the substances diffuse and the sublimate concentration in the sublimate-containing gas decreases, in order to discharge a large amount of sublimate, a very large amount of sublimate-containing gas must be discharged. That is, in the combustion apparatus, a large amount of low-concentration sublimate-containing gas must be processed, resulting in a disadvantage of low energy efficiency. Also,
In this method, it is actually extremely difficult to completely exhaust the sublimate-containing gas that has been diffused and reduced in concentration from the exhaust port.
Sublimate that cannot be completely discharged accumulates in the preheating chamber, eventually contaminating the foam sheet that is being preheated.

Furthermore, in order to combust the sublimate-containing gas in the combustion equipment, the temperature must be increased by approximately 150°C, and although the associated thermal energy is large, all of the heated purified gas is consumed by the foam sheet. It is not used for heating, and some of it is discharged outside the system, resulting in a large energy loss. Moreover, in this method, the purified gas after combustion reaches a high temperature of 400 to 450° C., so it is not possible to directly heat the foamable sheet with this gas. Therefore, it is necessary to mix it with outside air or exhaust gas and lower the temperature to a temperature suitable for foaming heating, for example, 150 to 350°C. When mixing with outside air, it is necessary to exhaust the thermal atmosphere corresponding to the amount of outside air taken into the system to the outside of the system, and this causes a large loss of thermal energy. Moreover, when mixed with exhaust gas, this mixed gas ceases to be a purified gas and becomes a sublimate-containing gas. When a foamable sheet is heated with this sublimate-containing gas, it becomes a foam sheet with sublimate adhering to it, and when the foam is cooled, crystals of the sublimate are deposited on the surface of the foam, resulting in a product with reduced commercial value.

That is, in the method and apparatus of JP-A-59-199222, the removal rate of sublimate in the combustion apparatus is very high, but in the entire thermoplastic resin foam production apparatus,
This has the disadvantage that if the removal rate is low or if the removal rate is made high, the thermal energy loss will be extremely large.

=8- Also, in this thermoplastic resin foam manufacturing equipment, the combustion device, which is a sublimation removal device, is composed of a combustion chamber, a catalyst element, a gas preheating device, an automatic control device, etc. A burner, electric heater, etc. must be installed, and the gas preheating equipment must also be equipped with a combustion air supply blower, propane gas and air piping, ascending and pressure gauges, etc., and an automatic control device. must be equipped with combustion control equipment, temperature indicator controllers, and pressure switches. Further, when the exhaust gas after combustion is used for preheating the exhaust gas, a heat exchanger is required in addition to the combustion device.

As is clear from article 2, this thermoplastic resin foam production equipment, especially the combustion equipment, has a very complicated structure, is expensive, and has the drawbacks of not being easy to maintain. It had a

〔the purpose〕

The present invention aims to prevent product contamination by continuously removing sublimate generated during decomposition of a pyrolytic foaming agent in the production of thermoplastic foam sheets. The purpose is to improve the manufacturing method and manufacturing equipment of the body, and its purpose is to achieve a good sublimate removal rate with low equipment cost and low thermal energy loss.
It is an object of the present invention to provide a method and apparatus for manufacturing a thermoplastic resin foam, which can be manufactured continuously over a long period of time and which is extremely easy to implement industrially.

〔composition〕

In the method of the present invention, a thermoplastic resin foam molded article containing a pyrolyzable blowing agent is introduced into a heating device and heated and foamed. The hot atmosphere is drawn into the cooling device, and is brought into contact with the cooling surface in the cooling device to cause the sublimate in the atmosphere to precipitate and adhere to the cooling surface, and the hot atmosphere from which the sublimate has been removed is heated. It is characterized by being sent back into the device. The apparatus of the present invention also provides a thermoplastic resin foam manufacturing apparatus equipped with a heating device for heating and foaming a thermoplastic resin foam molded article containing a pyrolyzable blowing agent. A suction port for a thermal atmosphere containing sublimate generated when the substance is thermally decomposed and a return port for the thermal atmosphere from which the sublimate has been removed are provided, and the suction port and the return port are connected by a pipe. They are connected to form a closed circuit, and are characterized in that a cooling device having a cooling surface for cooling and removing the sublimate is interposed in the closed circuit.

The method of the present invention will be explained in detail below.

In the present invention, a thermoplastic resin foamable molded article (hereinafter also simply referred to as a foamable molded article) is composed of a foamable thermoplastic resin composition containing at least a pyrolyzable foaming agent, and is A molded article made of a crosslinked thermoplastic resin foamable composition obtained by crosslinking treatment, a molded article made of a crosslinked thermoplastic resin foamable resin composition containing a crosslinking agent, and a molded article that is not crosslinked and A molded article made of a non-crosslinked thermoplastic resin composition that does not contain a crosslinking agent is also included. Among these, crosslinking or crosslinkable thermoplastic resin foaming is advantageous because it is easy to adjust the viscosity to a state suitable for foaming during heating and foaming of the foamable molded product, and it is also easy to achieve high foaming. A molded article made of a synthetic resin composition is preferably used. In this case, a molded article made of a crosslinked thermoplastic resin composition is obtained by heating or exposing a molded article made of a composition of a thermoplastic resin, a pyrolytic foaming agent, and a crosslinking agent to cause crosslinking. Alternatively, it can be obtained by crosslinking a molded article made of a thermoplastic resin and a foaming agent by irradiating it with ionizing radiation.

Note that the shape of the foamable molded product includes not only a sheet shape but also arbitrary shapes such as a tube shape, a rond shape, a prismatic shape, and the like.

In addition to conventionally known polyolefin resins, thermoplastic resins used in the present invention include polyvinyl chloride resins, polystyrene, 1,2-polybutadiene, thermoplastic polyurethane, and the like. Density polyethylene, linear low density polyethylene, ultra low density polyethylene, medium high density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene propylene rubber, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl chloride copolymer, Examples of polyvinyl chloride resins include ethylene-vinyl acetate-backoxidation element copolymer, ethylene-acrylic acid ester copolymer, ethylene-vinyl chloride copolymer, chlorinated polyethylene, and polybutene. , vinyl chloride
Ethylene copolymer, vinyl chloride-vinyl acetate copolymer,
There are vinyl chloride-ethylene-vinyl acetate copolymers and the like, and these can be used alone or in combination of two or more as necessary.

Examples of thermally decomposable blowing agents include azodicarbonamide, N,N'-dinitrosopentamethylenetetramine,
Examples include P, P'-oxybisbenzenesulfonyl hydrazide. Among these, azodicarbonamide decomposes rapidly, but it generates little heat during decomposition, is less likely to burn the foam, has no risk of explosion, and has a low melt-kneading temperature for thermoplastic resins, especially polyolefin resins. When crosslinking with a foaming temperature and a crosslinking agent is required, it is the most preferred because it is well balanced with the crosslinking temperature and a foam with fine cells can be obtained.

In addition, the sublimate in the present invention is a component in the foaming gas generated when a thermoplastic resin containing a pyrolyzable blowing agent is heated and foamed, and is a substance that normally becomes solid when the temperature is lowered, but depending on the temperature conditions and It may become liquid depending on humidity conditions, and is mainly a decomposed sublimated product of a thermally decomposable blowing agent. Urea, cyanuric acid, cyanomerite, etc. are known as sublimated products generated during thermal decomposition of azodicarbonamide.

In addition, as a crosslinking method when crosslinking is required with a crosslinking agent, there are a chemical crosslinking method and a silane crosslinking method (water crosslinking method). 2-bis(1-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)valerate, di-t-butylperoxide, t
-butylcumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane,
Examples include organic peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, and in the latter case, the crosslinking agent that decomposes by heating etc. and crosslinks the thermoplastic resin is: It is a silane compound having a vinyl group and a silanol condensation catalyst, and a silane-modified thermoplastic resin is crosslinked in the presence of moisture. Examples of the silane compound having a vinyl group include vinyltrimethoxysilane, and examples of the silanol catalyst include dibutyltin laurate.

In the present invention, various known additive components such as crosslinking aids, foaming aids, anti-aging agents, antistatic agents, flame retardants, inorganic fillers, pigments, conductive materials, etc. are appropriately blended as necessary. I can do that.

In the present invention, the thermal atmosphere containing the sublimate that is continuously drawn in the heating device is supplied to the cooling device for removing the sublimate, where it is cooled by contacting the cooling surface. At this time, there is no extreme drop in the temperature of the thermal atmosphere. The present invention does not precipitate sublimate by directly cooling the hot atmosphere itself, but sublimates the sublimate at a temperature higher than the freezing point in the hot atmosphere by cooling surfaces such as cooling pipes and cooling walls at a temperature lower than the freezing point. The substance is brought into contact with the sublimate catcher, thereby bringing the temperature below the freezing point of the sublimate, and depositing it on the cooling surface.There is no need for the temperature of the entire thermal atmosphere to be below the freezing point temperature of the sublimate, much less to lower the temperature to room temperature. In addition, when the blowing agent is azodicarbonamide, the freezing point of the sublimate is as high as 132°C, which is relatively high even for urea, which is a sublimate with the lowest freezing point.
This is because there is no need to make the temperature extremely low.

The temperature of the sublimate-containing thermal atmosphere and the thermal atmosphere after sublimate removal differs depending on the type of blowing agent, compounding ratio, heating conditions for the foamable molded product, etc., so it cannot be unambiguously discussed. When introducing a foamable molded product containing 14 parts by weight of azodicarbonamide to 100 parts by weight of low-density polyethylene into a heating device with a maximum temperature of 240°C and foaming it, the suction temperature of the sublimate-containing thermal atmosphere is is about 220°C, and the temperature of the hot atmosphere after removing the sublimate is about 190°C, which is much higher than the freezing point temperature of urea, which is the main component of the sublimate, at 132°C. The temperature of the refrigerant in contact with the cooling surface is usually 0 to 130°C, preferably 3 to 100°C. Further, the area of the cooling surface is 0.01 rrr or more, preferably about 0.05 to 50 i per thermal atmosphere 1rr11/SeC.

In the present invention, since all of the thermal atmosphere after sublimate removal is normally returned to the heating device, there is no loss of thermal energy due to exhaustion of the thermal atmosphere to the outside of the system (atmosphere). There is also little energy loss.Therefore, the present invention can be said to be an innovative method in which thermal energy loss is extremely low, even though it is a method for cooling and removing sublimate.

In the present invention, the hot atmosphere returned to the heating device after sublimate removal can be used for heating, including preheating the foamable molded product, but normally, it is not used for foaming molded products or molded products in the foaming process. Return it to an appropriate location within the heating device to prevent it from being sprayed directly and use it to keep the temperature inside the device. The reason is,
The cooling device in the present invention is only for removing sublimate, and it is not intended to keep the amount and temperature of the hot atmosphere constant after passing through the device, and if you try to forcefully control the temperature and amount, This is because not only is it difficult to control, but also the sublimate removal ability is reduced or thermal energy loss is increased. Furthermore, even if it were possible to install a cooling device or ancillary devices that do not reduce the removal capacity or increase heat energy loss, in this case, these devices would become expensive.

In the present invention, it is desirable that the hot atmosphere containing the sublimate be suctioned at one or more locations, preferably two or more locations, at least from just before the start of foaming of the thermoplastic resin foam molding to just after the end of foaming. The reason for this is that the generation of sublimate occurs during the foaming process of the foamable molded product, and the hot atmosphere with a high concentration of sublimate can be sucked in before the sublimate diffuses, reducing the suction of the hot atmosphere. This is because thermal energy loss and sublimate removal can be achieved at a high rate. In this case, in order to further increase the sublimate removal rate, it is recommended to suction the sublimate-containing hot atmosphere over a width of 172 or more from the surface direction of the foamed molded article, the molded article in the foaming process, and the foamed body. It is preferable to suction with a width of 273 or more, and more preferably. If the suction width is set to 172 or more times the width of the foamable molded object, the molded object in the foaming process, or the foamed object, it is possible to effectively prevent the sublimate from diffusing outside the foaming zone, and to efficiently suction the sublimate. It becomes possible. It is preferable to apply suction from both sides of the foamable molded article, etc., except in cases where suction from both sides is not possible, such as in bath foaming methods. In the present invention, the sublimate can be sucked from a location other than the foaming zone, and in that case, the sublimate is most likely to accumulate and precipitate in the heating device, for example, at the highest location and the lowest temperature. It is desirable to choose the case and inhale.

In addition, the suction width as used in the present invention is defined as the width of the suction opening of the suction device in the width direction of the foamable molded article, the molded article in the foaming process, or the foam, and the suction width is defined as the width of the suction opening of the suction device in the width direction of the foamed molded article, the molded article in the foaming process, or the foamed article, and the suction width is defined as the width of the suction opening of the suction device in the width direction of the foamed molded article, the molded article in the foaming process, or the foamed article. In this case, it means the distance between the outer ends of both end holes in the width direction.

In addition, suction in one direction means suctioning the hot atmosphere in a direction perpendicular to the surface of the foamable molded article, the molded article in the foaming process, or the foamed article.

Next, a manufacturing apparatus directly used for carrying out the method of the present invention will be explained with reference to the drawings.

Although FIGS. 1, 2, and 3 are diagrams schematically showing embodiments of the foam manufacturing apparatus of the present invention, the present invention is not limited to these illustrated apparatuses.

In FIG. 1, ▪ indicates a horizontal heating device, in which preheating of the foamable molded product, crosslinking heating when crosslinking by heating is required, and foaming heating are all performed in a horizontal or nearly horizontal state. The heating device 1 is a preheating chamber or a crosslinking chamber 2
(hereinafter referred to as bridging chamber 2) and bridging foaming chamber or foaming chamber 3
(hereinafter referred to as the foaming chamber 3), and a pair of rolls 6 are provided at the entrance of the crosslinking chamber 2 to supply the foamable molded product 4 into the apparatus (inside the crosslinking chamber). ,
A pair of rollers are provided at the outlet of the foaming chamber 3 to take away the foam 5. A partition wall 11 is provided between the bridging chamber 2 and the foaming chamber 3, and has an opening through which moving objects such as a foamed molded article and a wire mesh conveyor belt 8 can pass, and the thermal atmosphere of the bridging chamber 2 and the foaming chamber 3 is This is done so that the temperature difference can be maintained. The wire mesh conveyor belt 8 is driven by conveyor driving rolls 10 and the like.

In the crosslinking chamber 2, far infrared heaters 9 for preheating or crosslinking heating the foamable molded product 4 are installed on the upper and lower surfaces of the wire mesh conveyor belt 8.

In the foaming chamber 3, hot air blowing nozzles 15 are attached to the upper and lower surfaces of the wire mesh conveyor belt 8 for heating for crosslinking or foaming the foamable molded product 4, and for supplying hot air to the blowing nozzles 15. A suction port 12 and a circulation fan 14 for the atmosphere inside the device are arranged in the bubbling chamber 3, and a heater 13 for heating the atmosphere sucked through the suction port 12 is interposed between the pipes connecting these. There is.

The overall structure of such a heating device 1 is not particularly different from that of the conventional one, and the features of the present invention are the suction port 16 for the sublimate-containing thermal atmosphere and the purified thermal atmosphere return port 22.
are installed in the heating device and connected through a pipe to form a closed circuit,
A cooling device 19 having a cooling surface for cooling and removing the sublimate is interposed in this closed circuit. The suction ports 15 are installed so as to be located on both sides of the foamable molded product from just before the foaming of the foamable molded product starts to after the foaming ends. Further, although the width of the suction port is not shown, the width at each position is 1/2 or more of the width of each of the foamable molded article, the molded article in the foaming process, and the foamed article. Although the suction ports 16 and the hot air blowing nozzles 15 are installed alternately in the latter half of the foaming chamber 3, the present invention is not limited to such an arrangement.

The return port 22 is installed in a place where the purifying heat atmosphere after sublimate removal is not directly blown onto the foamable molded article and the molded article in the foaming process.

To explain the peripheral equipment of the cooling device 19, 20 is a circulation fan for suctioning a hot atmosphere containing sublimate;
．． Reference numeral 21 denotes a suction amount adjusting valve which also makes it possible to shut off the thermal atmosphere containing sublimated substances. If the purpose is only to adjust the amount of suction, the valve is
Although only one of the 18 valves is required, 21 valves are necessary in order to shut off the pipeline to the foaming chamber when cleaning the inside of the cooling device and drying after cleaning.

Measuring instruments 23 and 24 are installed at the entrance and exit portions of the cooling device to measure the temperature of the sublimate-containing thermal atmosphere sucked into the cooling device and the purified thermal atmosphere discharged from the cooling device.

The wall of the cooling device 19 has a jacket structure through which cooling water, air, etc. can pass, forming a cooling surface. Further, a coiled cooling pipe 29 is installed in the device, and water or ventilation can be passed through the pipe to form a cooling surface. The sublimate cooled on the cooling device wall and the cooling surface of the cooling pipe 29 is deposited on these surfaces and removed. FIG. 1 shows a case where the refrigerant of the cooling device is cold water, and 25.26 is a cooling water supply port, and 27.28 is a cooling water discharge port. Note that the cooling pipe in the device is not limited to a coil-shaped one, and various shapes such as a fin-shaped one can be used.

When a large amount of sublimate has accumulated in the cooling device 19 over time, the circulation fan 20 is stopped and the suction amount adjustment valve 18.
21 is fully opened, and the cleaning liquid is injected into the apparatus through the cleaning liquid inlet 30. In this case, since the sublimate is mainly a compound that is easily soluble in water, the cleaning liquid is usually water. However, for poorly soluble substances, a solubilizing agent such as a surfactant can also be injected through the same injection port or another injection port.

After the cleaning liquid is injected, the cleaning liquid is stirred by the stirring blade 32 to clean the inside of the apparatus. After washing, the washed dirty liquid discharge port 31 is opened to discharge the sublimate-containing dirty liquid to the outside of the cooling device.

After draining the dirty liquid, the discharge port 31 is closed, the circulation fan 20 is started, and the suction amount adjustment valve 18 and the purification heat atmosphere discharge valve 33 are opened, so that a hot atmosphere passes through the cooling device wet with the cleaning liquid. The inside of the device can be dried in an instant.

Even during this drying process, the sublimate is removed within the cooling device, so the thermal atmosphere released into the atmosphere is purified. After drying, the discharge valve 33 is closed and the other suction amount adjusting valve 21 is opened to perform continuous removal of the sublimate again.

In the present invention, the most efficient method is to discharge the sublimate out of the device as described above, but the cooling device is not limited to that shown in FIG. The cooling device may have a structure in which the sublimate can be taken out directly from the device.

Figure 2 shows an apparatus for producing thermoplastic resin foam in which the foaming chamber is vertical. using
This is an example in which a far-infrared heater 9 is used in the foaming chamber 3.

In addition, in Fig. 2, two cooling devices are placed in parallel in a closed circuit for removing sublimate (19a, 19b), which is the first point.
Different from the example in the figure. In the example of FIG. 1, there is no cooling device 19 in the circuit, so sublimate removal must be temporarily interrupted when cleaning the inside of the device, but in the example of FIG. 2, the cooling device 19 is placed in parallel. Complete continuous removal of the sublimate is possible by using them alternately. Therefore, sufficient time can be taken to clean the cooling device, and maintenance and inspection of the cooling device can be performed while manufacturing the foam. Due to these factors, the continuous operation time of the foam manufacturing apparatus is further extended than in the example shown in FIG.

FIG. 3 shows a manufacturing device in which the foaming chamber 3 is vertical as in FIG.
This is an example of heating with hot air via 4. A far-infrared heater 9 for heating the hanging foamable molded product before it enters the foaming chamber 3 is installed for the purpose of appropriately controlling heating on the front and back sides and left and right sides of the foamable molded product. The foamable molded product is divided into several blocks not only in the surface direction but also in the width direction, so that each block can be independently controlled. By appropriately controlling this heater 9, it is possible to prevent or correct the curling of the hanging foam molded product and to stabilize the expansion of the foam in the width direction. The former is achieved mainly by heating the front and back sides of the foamed molded product, and the latter is achieved by controlling heating in the width direction.

In FIG. 3, one cooling device is installed in each closed circuit of the bridging chamber 2 and the foaming chamber 3 (19a, 19b).

In FIG. 3, most of the sublimate generated during foaming of the foamable form is absorbed by the sublimate-containing thermal atmosphere suction port 16 before being diffused.
The sublimate that cannot be suctioned through a is diffused into the foaming chamber, moves to the upper part, and enters the bridging chamber 2 located at the upper part of the foaming chamber 3 through the opening that communicates them. . Therefore, if a foam is produced for a long time using suction only from 168, the concentration of sublimate in the atmosphere of the crosslinking chamber 2 will gradually increase over time, and the highest and lowest temperature location in the crosslinking chamber 2 will gradually increase. For example, sublimate deposits are deposited on the ceiling near the inlet of the foamed molded product, fall and contaminate the foamed molded product, resulting in contamination of the product. Therefore, by installing the suction port 16b at this location, it is possible to further extend the distance between the suction ports 16b during continuous operation of the foam manufacturing apparatus. In this case, the size, particularly the width, of the suction port does not need to be limited by the width of the foamable molded article, and can be made to any size depending on the amount of suction.

FIG. 4 is a drawing of the apparatus shown in FIG. 3 as viewed from the surface direction of the foamable molded body and the foamed body. As is clear from this, the foaming and heating of the foamable molded product by the hot air from the hot air blowing perforated plate 34 is completed before the foaming is completed, and the sublimated product having a width of 172 or more than the width of the foam is formed at a position before and after the foaming is completed. A suction port (perforated plate) 16a for containing thermal atmosphere is installed. The foamable molded product in the middle of foaming continues to foam even after heating is finished due to self-heat generation due to the residual heat and the reaction heat when the foaming agent is separated.
(The decomposition reaction of blowing agents is often an exothermic reaction).

Therefore, the suction port for the sublimate-containing thermal atmosphere, which is installed from immediately after the start of foaming of the foamable sheet to immediately after the completion of foaming, is used for heating the foaming molded product as shown in Figures 1 and 2. It is not limited to installation alternately with heating sources. Rather, in terms of heating efficiency, the devices shown in FIGS. 3 and 4 are preferable.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

In the following examples, a thickness of 100 parts by weight of low-density 28 polyethylene with a density of 0.92 g/cJ, 15 parts by weight of azodicarbonamide as a blowing agent, and 0.8 parts by weight of dicumyl peroxide as a crosslinking agent is used. 1, 8mm, width 3
A 40 mm thermoplastic resin foam molded sheet is fed at a speed of 2.2 m/min to the heating device 1 shown in FIG. At other times, a sublimate removal circuit was used to continuously remove the sublimate. The foam sheets obtained in all Examples had a density of 0.036 g/J, a thickness of 5 mm, and a width of 1000 mm.

Example 1 In the apparatus shown in FIG. 3, the circulation fan 20a is not started,
The suction amount adjusting valves 18a and 21a were fully closed, and the foam was continuously produced without using the cooling device 19a attached to the foaming chamber 3. That is, the sublimate was continuously removed using only the closed circuit provided for the crosslinking chamber 2. The circulation rate of the hot air circulation circuit for heating the foamable molded product sheet is 120ITi'/win for both the crosslinking chamber 2 and the foaming chamber 3,
The circulation rate of the hot air in the sublimate removal circuit was 40 rn'/min, and the temperatures of the hot air at the inlet and outlet of the cooling device 19b were 190° C. and 170° C., respectively. Moreover, the power consumption of the entire device was 70Kw.

When continuous production of foam sheets was carried out under these conditions,
The continuous operation time was 4 months, and during this period there was no obvious product contamination due to dripping of sublimate, etc. However, after about 2 months, I began to notice the odor of the sublimate in the product. Example 2 Contrary to Example 1, the sublimate was continuously removed using only the closed circuit provided for the foaming chamber 3. I did it.

The hot air @ calibration of the sublimation removal circuit is 20 sheets/min,
The temperature of the hot air at the inlet and outlet of the cooling device 19a is 22
The temperatures were 0°C and 200°C. Further, the power consumption of the entire device was 65 kW. Continuous production of foam sheets was carried out under the same conditions as in Example 1, and the continuous operation time was 8.
During this period, there was no clear contamination of the product due to dripping of the sublimate, and the product had almost no odor of the sublimate.

Example 3 In FIG. 3, both sublimate removal circuits provided in the bridging chamber 2 and the foaming chamber 3 were used simultaneously to continuously remove the sublimate. The amount of hot air circulated in the sublimate removal circuit is 20 m' each for the closed circuit for the bridging chamber 2 and the closed circuit for the foaming chamber 3.
/min, and the temperature of the hot air at the inlet and outlet of the cooling device is 190°C and 170°C at 19b, and 220°C at 19a.
, 200°C. Also, the power consumption of the entire device is 70
It was kw. Other conditions were the same as in Example 1, and when continuous production of foam sheets was carried out, it was confirmed that the continuous operation time was over 1 year.

Continuous operation beyond this point was not possible because inspection and maintenance of equipment other than the cooling system was required. Of course, there was no product contamination due to sublimate over the past year, and no odor of sublimate was detected in the product.

Comparative Example 1 Continuous production of a foam sheet was carried out without using both of the two sublimate removal circuits in FIG.

A sublimate odor was detected in the product just two hours after the start of operation, and there was clear product contamination by sublimate after one day of continuous operation. Power consumption was 60kw. The product foam sheets obtained were the same as those of Examples 1 to 3, except for contamination.

Comparative Example 2 In Example 2, the foam sheet was manufactured with the suction amount adjustment valve 21a fully open, the purification heat atmosphere discharge valve 33a fully open, and the supply of cooling water to the cooling device stopped. Heater 1.3a is installed to compensate for the temperature drop caused by
However, due to insufficient capacity of the heater, the foamable molded sheet suffered from insufficient foaming due to insufficient heating. Therefore, the feeding speed of the foamable molded sheet was set at 2.2 m/mi.
By decreasing the speed from n to 1.1 m/min, the foaming failure was resolved. Power consumption was 140 kW, and since cooling water was not supplied to the cooling device, the hot atmosphere discharged into the atmosphere contained sublimate and had a strong odor. Although the continuous operation time was not examined, it should be equal to or longer than Example 2. However, this method is not suitable for industrial use because it causes very large thermal energy loss and air pollution.

The results of Examples 1 to 3 and Comparative Examples 1.2 are summarized in Table 1.

Table 1 [Effects] According to the present invention, since the cooling device for removing sublimate has an extremely simple structure, the equipment cost is low, but as is clear from the results in Table 1, production and performance are reduced. There is no
With low thermal energy loss, it allows good removal of sublimate and allows continuous production of pollution-free foams over long periods of time.

[Brief explanation of the drawing]

1 to 3 are drawings schematically showing an embodiment of the foam manufacturing apparatus of the present invention. FIG. 1 shows an example of a horizontal device in which a bridging chamber and a foaming chamber are arranged horizontally, and a cooling device is attached to the foaming chamber. FIG. 2 shows an example of a device in which a vertically elongated foaming chamber is disposed below the bridging chamber, and two cooling devices are attached to the foaming chamber in parallel. FIG. 3 shows the same external shape of the device as in FIG. 2, but shows an example in which cooling devices are attached to both the bridging chamber and the foaming chamber. Figure 4 shows the bridging chamber and foaming chamber in the apparatus of Figure 3.
FIG. 2 is a construction view of a foamable molded article and a foamed article viewed from the surface direction. 1... Heating device, 2... Crosslinking chamber (or preheating chamber), 3
... Foaming chamber (or crosslinking foaming chamber), 4... Foamable molded product, 5... Foamed body, 8... Wire mesh conveyor belt, 9
... Far infrared heater, 12... Intake port for atmosphere inside the device, 13... Heater, 14.20... Circulation fan,
15...Hot air blowing nozzle, 16, 16a, 16b...
・Suction port for thermal atmosphere containing sublimate, 19, 19a, 19
b... Cooling device, 22... Purification heat atmosphere return port, 2
5.26... Cooling water supply port, 27.28... Cooling water outlet, 29... Coiled cooling pipe, 30... Cleaning liquid inlet, 31... Washing liquid discharge port, 34 ...Hot air blowing perforated plate.

Claims (5)

[Claims] (1) In a method of introducing a thermoplastic resin foamable molded article containing a pyrolytic foaming agent into a heating device and heating and foaming it,
The hot atmosphere containing the sublimate generated during decomposition of the blowing agent is continuously sucked, the hot atmosphere is introduced into the cooling device, and the sublimate in the hot atmosphere is brought into contact with the cooling surface in the cooling device. A method for producing a thermoplastic resin foam, characterized in that the purified heat atmosphere from which the sublimate has been removed is returned to a heating device. (2) Apply suction of the hot atmosphere containing the sublimate to 1/2 or more of the width of each of the foamable molded product, the molded product in the foaming process, and the foamed product from just before the start of foaming to just after the end of foaming. The method according to claim 1, wherein the method is carried out from the widthwise direction. (3) In a thermoplastic resin foam manufacturing apparatus equipped with a heating device that heats and foams a thermoplastic resin foamable molded product containing a pyrolyzable blowing agent, the blowing agent is thermally decomposed within the heating device. A suction port for a thermal atmosphere containing sublimate generated during the process and a return port for a purified heated atmosphere from which the sublimate has been removed are provided, and the suction port and the return port are connected by a pipe. 1. An apparatus for producing a thermoplastic resin foam, characterized in that a closed circuit is formed, and the closed circuit is provided with a cooling device having a cooling surface for cooling and removing sublimate and removing precipitation. (4) A hot atmosphere suction port with a width of 1/2 or more of the width of each of the foamable molded product, the molded product in the foaming process, and the foam is provided in the section from just before the start of foaming to just after the end of foaming in the heating device. , and the suction port is located in the direction of these surfaces. (5) At least one cooling device interposed in the closed circuit for cooling and removing the sublimate is installed in the closed circuit, and a hot atmosphere inlet/outlet of the cooling device or a pipe leading to the inlet/outlet of the cooling device is provided. Each channel is equipped with a shutoff device that blocks the entry and exit of the hot atmosphere, and the cooling device has a cleaning liquid inlet leading to the inside and an outlet for discharging the dirty liquid after cleaning. The device according to claim 3 or 4, which is provided with a stirring blade for use.