JP3249800B2 - Method for producing pulp molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pulp molded article having improved dewatering / drying efficiency.

[0002]

2. Description of the Related Art In the process of manufacturing a pulp molded article, a wet molded article obtained by papermaking is dewatered from the viewpoint of improving handleability and shortening a drying time. There is a step to do. For dehydration,
A method of performing press dehydration using an elastic body and a method of performing pressure dehydration using a flexible film are known.

However, in the above-mentioned method, since it is necessary to increase the pressing force in order to reduce the water content of the molded article, the pulp bites into the papermaking net, leaving a trace of the net on the surface of the molded article, and Gets worse. In addition, the apparatus is increased in size to increase the pressing force. Further, mechanical dehydration naturally has its limits, and it takes a long time to dehydrate to a satisfactory moisture content, and the dehydration efficiency is not good.

On the other hand, Japanese Patent Laid-Open Publication No.
Publications and JP-A public Sho 60-4320 9-316800
As described in Japanese Patent Application Laid-Open Publication No. H10-209, there is known a method in which a wet molded body is heated and dried by steam. However, this method is not advantageous in terms of energy because it attempts to dry the compact by heat exchange using the heat energy of the steam.

Accordingly, it is an object of the present invention to provide a method for producing a pulp molded article capable of efficiently dewatering and drying a wet molded article.

[0006]

In order to achieve the object of the present invention we have found that, superheated steam
Is blown at a specific pressure or more, by a physical mechanism not mainly heating and drying by heat exchange, it is possible to instantaneously remove moisture from the wet molded body, and that high dehydration efficiency is achieved. I learned.

[0007] The present invention has been made based on the above findings, and supplies pulp slurry into the cavity of a papermaking mold in which a cavity having a predetermined shape is formed, and sucks the inside of the cavity toward the outside of the papermaking mold. after forming the pulp molded article in a wet state the inner surface of the cavity Te, under a state where the inside the cavity in an airtight, pressure in the cavity is narrowing blowing superheated steam so as to 98kPa [gage] or more, The above object has been achieved by providing a method for producing a pulp molded article, in which the pulp molded article is dewatered.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. In FIG.
1 shows a papermaking / dewatering apparatus used in an embodiment of a method for producing a pulp molded article (hereinafter, also simply referred to as a molded article) of the present invention. The papermaking / dewatering apparatus 1 is used for producing a bottle-shaped molded body, and is roughly classified into a slurry supply section 2, a papermaking section 3, a heating fluid supply section 4, and a discharge section 5.

The slurry supply unit 2 stores a pulp slurry (hereinafter, also simply referred to as slurry) 21, and a slurry storage tank 23 provided with a stirrer 22 for the slurry 21. A pump 24 for supplying the slurry 21 into the mold 33,
A flow meter 25 for measuring the flow rate of the slurry 21 and a valve 26 are provided. The pump 24, the flow meter 25, and the valve 26 are connected in this order by a pipe 27. One end of the conduit 27 is immersed in the slurry 21, and the other end is connected to a cavity 34 of a papermaking mold 33 described later.

The papermaking section 3 has a papermaking mold 33 composed of two sets of split molds 31 and 32. The split faces of the two split molds 31 and 32 are brought into contact with each other to form a papermaking mold 3.
3, a cavity 34 having a predetermined shape is formed.
A number of grooves (not shown) are formed in the inner surface of the cavity 34 and communicate with the outside of the papermaking mold 33. Thus, rapid discharge of sufficient distribution and condensate fluid (superheated steam) to be described later is secured. The cavity 34 is provided with a net 3 having a mesh of a predetermined size.
5 coated. The cavity 34 is open toward the outside of the papermaking mold 33. This opening is 3
Blocked by 9. The aforementioned slurry 21 and a pressurized fluid described later are supplied into the cavity 34 through holes formed in the sealing plate 39.

A hollow manifold chamber 36 is formed inside each of the split dies 31 and 32. A plurality of communication holes 37 communicating with the manifold chamber 36 are formed in the inner surface of the cavity 34.
Are drilled. Further, a through hole 38 communicating with the manifold chamber 35 is formed in the outer surface of the papermaking mold 33.
As a result, the cavity 34, the communication hole 37, the manifold chamber 36, and the through hole 38 communicate with the papermaking mold 33 to form a communication passage communicating from inside to outside of the papermaking mold 33.

The heating fluid supply unit 4 includes a fluid supply source 41,
A conduit 42 for supplying a fluid from a supply source 41 into the cavity 34 and a heat exchanger 43 interposed in the conduit 42 and heating the fluid are provided. Supply source 41 and heat exchanger 4
A pressure adjusting valve (not shown) for the heating fluid is interposed between the heating fluid 3 and the heating fluid 3 so that the pressure of the heating fluid blown into the cavity 34 can be adjusted. In addition, the conduit 42 is
It is kept warm or heated to prevent the temperature of the heated fluid from dropping. However, when the unheated compressed air is used as the fluid, the heat exchanger 43 is unnecessary.

The discharge section 5 has an exhaust line 51 and a drain line 52. Each line is a through hole 3 of the papermaking mold 33.
8 is connected. In the middle of the exhaust line 51, the valve 5
1a is interposed. A valve 52a is also provided in the middle of the drain line 52. The end of the drain line 52 is connected to a suction pump 53. A steam separator is interposed between the pump 53 and the valve 52a. The sealing plate 39 for closing the upper opening of the papermaking mold 33 includes:
The second exhaust line 55 is connected. In the middle of the second exhaust line 55, a valve 55a is interposed.

A method for manufacturing a molded article using the papermaking / dewatering apparatus 1 will be described. First, the injection pump 24 is started, the slurry 21 is sucked up from the slurry storage tank 23, and passed through the flow meter 25 and the valve 26. Then, the slurry 21 is injected under pressure into the cavity 34 of the mold 33. At that time, the flow rate of the slurry 21 is measured in-line by the flow meter 25. The suction pump 53 is started together with the pressurized injection of the slurry 21, and the inside of the cavity 34 is suctioned under reduced pressure toward the outside of the papermaking mold 33 through the above-described communication path to suck water in the slurry 21.
The pulp fibers are deposited on the net 35 covering the inner surface of the pulp. As a result, the molded body 10 in a wet state in which the pulp fibers are deposited is formed on the net 35.

When a predetermined amount of the slurry 21 is supplied into the cavity 34, the injection pump 24 is stopped and the valve 2
6 is closed. Next, a predetermined fluid is blown from the fluid supply source 41 into the airtight cavity 34 through the upper opening of the papermaking mold 33 which is a blowing port. Here, the air-tight state does not mean a state in which the inside of the cavity 34 is completely air-tight, but means that the inside of the cavity 34 is air-tight so that the pressure inside the cavity 34 becomes higher than a pressure to be described later. When blowing, the valve 5 of the exhaust line 51
1a is in an open state. On the other hand, the valve 55a of the second exhaust line 55 is in a closed state. The valve 52a is in a closed state. The blown fluid passes through the molded body 10 and is exhausted from the exhaust line 51 through the communication hole 37, the manifold chamber 36, and the through hole 38. When superheated steam, which will be described later, is used as the fluid, condensed water may adhere to the surface of the cavity 34.
It is quickly discharged outside. This condensed water is separated by a steam separator 54 provided as needed.

[0016] as a fluid, overheat steam is used. Over <br/> Netsu蒸gas, the pressure in the cavity 98kPa [gage] or more, preferably 196kPa [gage] or more, more preferably blown write rarely so that 294kPa [gage] or
You. By performing the blowing like this, by physical mechanisms not mainly heat drying by heat exchange,
Moisture is instantaneously dehydrated (removed) from the wet molded body 10. In particular, the condensation heat transfer due to excessive hot vapor, the temperature of the molded body, almost reaches the saturation steam temperature instantaneously. As a result, the interfacial tension and viscosity of water are reduced, and the water held in the molded body is blown off very efficiently and instantaneously. Since this dehydration method does not mainly involve heat exchange, it is a very energy-efficient method. In addition, since the dehydration is completed instantaneously, the dehydration time can be reduced. Since a core made of an elastic material used in a heating and drying step described later is not used for dehydration, machine time for inserting the core into the cavity is not required, and the machine time can be reduced. Further, since the blowing pressure is lower than the pressure for press dewatering, there is an advantage that a trace of a net is less likely to be formed on the surface of the obtained molded product, and a molded product having a good appearance can be obtained.
Note that the pressure in the cavity 34, refers to the difference between the inlet pressure and the outlet pressure to superheat steam of cavitation <br/> I 34.

It is preferable that the pressure in the cavity 34 due to the blowing is higher as long as it is equal to or higher than the above-mentioned value. However, the degree of water removal gradually becomes saturated with the increase of the blowing pressure. Is 9 8
0kPa an extent.

The instantaneous dewatering of the molded body 10 by blowing of the superheated steam, complete when mold internal pressure is almost reached a certain value. Here, the mold internal pressure includes the original pressure, the blowing flow rate, and the molding 1
0. Therefore, when the air permeability of the molded body 10 is low and the blowing flow rate is large, the mold internal pressure rises instantaneously, and the dehydration is completed instantaneously. On the other hand, when the air permeability of the pulp is high and the blowing flow rate is low, the rise of the internal pressure of the mold tends to be slow, and the completion time of dehydration tends to be long. Generally, dehydration is completed in a very short time of about 0.1 second to 10 seconds, particularly about 1 second to 5 seconds. By this dehydration, for example, the water content before dehydration is 75 to 80% by weight.
Is dehydrated to about 40 to 60% by weight.

The overheating steam type pressure may if it is overheated to the extent that does not condense to just before that and the steam become the previous value or more is blown into the mold. The steam may be sufficiently heated, but the dewatering effect does not change significantly .

[0020] After dehydration of the molded body 10 by the blowing of the superheated steam, while continuing to continue blowing the, open the valve 55a of the second exhaust line 55. Then, a part or the whole of the superheated steam blown into the cavity 34, is exhausted from the second exhaust line 55 leading to the upper opening of the papermaking mold 33 is a blowing port of the blowing. The moisture content of the adult form 10 is high air permeability is low, there is a case where heat exchange is not enough can be blown overheating steam, the moment after dehydration,
By exhausting a part or the whole while blowing superheated steam, superheated steam flows and circulation into the cavity 34,
Heat exchange occurs between the inner surface of the molded body 10 and the inner surface is heated and dried. As a result, the drying efficiency is improved.
Further, a gradient of the water content occurs in the thickness direction of the molded body 10. Specifically, the water content gradually increases from the inner surface to the outer surface of the molded body 10. That is, the molded body 10 has the lowest moisture content on the inner surface and the highest moisture content on the outer surface. Since the molded body 10 has such a water content gradient, the cavity shape of the heating mold is easily transferred faithfully to the molded body 10 in the main step of heating and drying described later, that is, the transfer accuracy is improved. preferable.

[0021] After the moment dehydration, or continue the blowing of the superheated steam, or a portion or time to carry out the evacuation of all of them,
It may be determined in consideration of the surface properties and transferability of the molded body 10 and the efficiency of this step of heating and drying as the next step. If the water content is reduced in the dehydration step, the time of this step of heating and drying becomes shorter. However, since the water content of the outer surface is also low, the surface property and transferability in this step of heating and drying are reduced.

After the instantaneous dehydration, the flow rate and temperature when using superheated steam for heating and drying may be appropriately set in consideration of drying efficiency, discoloration of pulp, and the like .

Next, the molded body 10 is subjected to this step of heating and drying. FIG. 2 is a schematic view of this step of heating and drying, in which (a) is a step of loading a molded body into a heating die, (b) is a core inserting step, (c) is a pressing step, d) is a step of opening the heating mold.

First, a heating mold 63 in which a cavity 64 having a shape corresponding to the outer shape of a pulp molded article to be molded is formed by combining a set of split molds 61 and 62.
Are separately prepared, and the heating mold 63 is heated to a predetermined temperature. In the present embodiment, the cavity shape of the heating mold 63 and the cavity shape of the papermaking mold 33 are the same. Each of the split dies 61 and 62 is formed with a plurality of communication holes 37 that communicate from the inside (that is, the inner surface of the cavity 64) to the outside. Each communication hole 37 is connected to suction means (not shown) such as a suction pump. The molded body 10 taken out by opening the papermaking mold 33 is loaded into the cavity 64 of the heated mold 63 as shown in FIG.

Next, as shown in FIG.
While the tube 3 is sucked from the inside to the outside, the expandable and contractible hollow core 65 is inserted into the molded body 10 in the contracted state. In the present invention, the expansion and contraction means that the core 65 itself expands and contracts to change its volume, and the core 65 itself does not expand and contract, but the fluid is supplied to or removed from the inside to reduce its volume. Is changed. Examples of the former are urethane, fluoro rubber,
Examples include a core made of an elastic material such as a silicone rubber or an elastomer.Examples of the latter include plastic materials such as polyethylene and polypropylene, films in which aluminum or silica is deposited on a film of these plastic materials, Films, papers, etc. in which aluminum foil is laminated on a plastic material film
A core made of a flexible material such as cloth may be used.
In the present embodiment, a bag-shaped (balloon-shaped) core made of a stretchable elastic material is used as the core 65.

Next, as shown in FIG.
The core 65 is expanded by supplying a predetermined fluid into the inside, and the molded body 10 is pressed toward the inner surface of the cavity 64 by the expanded core 65. Thereby, the heating and drying of the molded body 10 proceeds, and the inner surface shape of the cavity 64 is transferred to the molded body 10. In this case, as described above, the molded body 10
The distribution of the water content in the thickness direction has a gradient, and the water content on the outer surface is highest. That is, the degree of freedom of the pulp on the outer surface of the molded body 10 and the vicinity thereof is kept relatively large. As a result, the pressed body 10
Thus, the shape of the cavity 64 is faithfully transferred, and the transfer accuracy is improved. Further, the inner surface of the molded body 10 and its vicinity are:
In the above-described dehydration step, dehydration is performed until the water content becomes sufficiently low, so that the drying efficiency of the entire molded body 10 is improved.

As the fluid used to expand the core 65, for example, air (pressurized air), hot air (heated pressurized air), superheated steam, oil (heated oil), and other various liquids are used. Is done. In particular, it is preferable to use air, hot air, or superheated steam from the viewpoint of operability and the like. The pressure for supplying the fluid is preferably 0.01 to 5 MPa, particularly preferably 0.1 to 3 MPa.

The molded article 10 is sufficiently dried and the molded article 10
When the shape of the inner surface of the cavity 64 is sufficiently transferred to
As shown in FIG. 2D, the fluid in the core 65 is drained, and the core 65 is reduced. Next, the reduced core 65 is taken out of the molded body 10, and the heating die 63 is further opened to take out the target pulp molded body 10.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the paper-formed and dehydrated molded article 10 in a wet state is taken out of the paper-making mold 33 and heated by the heating mold 6.
3 and heated and dried using the core 65. Instead, the molded body 10 was not taken out of the papermaking mold 33, and the core was heated and heated in the mold 65 using the core 65. The molded body 10 may be dried by heating.

After the instantaneous dehydration, the fluid (superheated steam)
In the case of performing the heat drying by (g ), it is not always necessary to separate the temperature of the fluid during the instant dehydration and the temperature of the fluid during the heat drying. At the time of flash dehydration, sufficiently superheated steam may be used. Further, the instant using superheated steam during dewatering, but it may also be used which is heated during heat drying compressed air.

Further, without performing the present step of heat drying shown in FIG. 2, in the dehydration step, the heated fluid (superheated steam) the molding 10 may be dried by heating to the final stage with. In this case, part or all of the heated fluid may be exhausted until the drying of the molded body 20 is completed.

In the above embodiment, the paper making mold 3
3 was used to perform papermaking and dewatering, but instead of this, the molded body 10 after papermaking was taken out of the papermaking mold 33, and the taken out molded body was loaded into a separately prepared dehydration mold, and the May be used for dehydration.

In the above-described embodiment, a pair of split dies is used, but three or more split dies may be used. Further, in the above-described embodiment, the bottle-shaped molded body is manufactured, but the shape of the molded body is not limited to this, and according to the present invention, molded bodies having various shapes can be manufactured.

[0034]

The present invention will be described in more detail with reference to the following examples. Unless otherwise specified, "%" represents% by weight.

Example 1 A pulp molded article in the form of a bottle was paper-made and dewatered using the paper-making mold shown in FIG. The moisture content of the molded article in a wet state before dehydration was 77%. During dehydration, superheated steam at 220 ° C. was blown into the cavity of the papermaking mold so that the pressure in the cavity became 294 kPa [gage], and dehydration was performed for 2 seconds. At this point, the water content of the molded article was reduced to 50%. While continuously blowing the superheated steam, a part of the superheated steam blown from the blowing port was exhausted, and the heat drying by heat exchange was performed for 8 seconds. Finally, the water content of the molded body was 41%. The moisture content on the outside of the molded body was 45%, and the moisture content on the inside was 3%.
2%.

Next, the papermaking mold was opened, and the wet molded product was taken out and loaded in a heating mold heated to 200 ° C. The heating mold has a cavity having the same shape as the papermaking mold. A hollow core made of an elastic material was inserted into the molded body loaded in the heating die, air was injected into the core at a pressure of 1.5 MPa, and the molded body was pressed against the inner surface of the cavity and dried by heating. When the molded body was sufficiently dried, the heating mold was opened, and the bottle-shaped molded body was taken out. The absolute dry weight of the obtained molded body was 35 g, the height was 240 mm, and the body diameter was 80 mm.

[Examples 2 to 4] The superheated steam used in Example 1 was blown so that the pressure in the cavity became 98 kPa [gage] (Example 2) and 196 kPa [gage] (Example 3). Dehydrated for seconds. At this point, the water content of the molded article was reduced to 61% (Example 2) and 52% (Example 3). In place of the superheated steam used in Example 1, 17
0 ° C superheated steam, the pressure inside the cavity is 294 kPa
[Gage], and dewatered for 2 seconds (Example 4). At this point, the water content of the molded article was reduced to 52%.

[0038]

[0039]

Comparative Example 1 The superheated steam used in Example 1 was blown so that the pressure in the cavity became 49 kPa [gage], and dewatered for 2 seconds. At this point, the water content of the molded article was reduced to 67%.

Comparative Example 2 In place of the superheated steam used in Example 1, heated and compressed air at 220 ° C. was blown so that the pressure in the cavity became 98 kPa [gage], and dehydration was performed for 2 seconds. At this point, the water content of the molded article was reduced to 66%.

Comparative Examples 3 to 5 Instead of the superheated steam used in Example 1, a bag-shaped core made of an elastic material was used. After inserting the core into the molded body, compressed air (490 kPa) at 30 ° C. was supplied into the core to expand the core, and the molded body was pressurized and dehydrated by the expanded core for 2 seconds. (Comparative Example 3). At this point, the water content of the molded article was reduced to 70 to 75%. In Comparative Example 3, the pressure dehydration time was changed to 10 seconds (Comparative Example 4) and 30 seconds (Comparative Example 5) instead of 2 seconds. At this time, the water content of the molded article was reduced to 63% (Comparative Example 4) and 60% (Comparative Example 5).

[0043]

According to the method for producing a pulp molded article of the present invention, a wet molded article can be efficiently dewatered and dried. Dehydration is energy-friendly because it does not mainly involve heat exchange, and can be performed in a very short time to shorten the production time. Furthermore, since the blowing pressure is relatively low, traces of the net hardly remain on the surface of the molded body, and the appearance is improved. In particular, after dewatering the pulp molded article blowing superheated steam into the cavity, while continuing the blowing, overheating <br/> steam blown in a Turkey it is exhausted from the blowing port of the blowing ,
The water content gradually increases from the inner surface to the outer surface of the molded body,
The transferability of the molded body is further improved, and heat exchange is promoted, so that the heating and drying efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a papermaking / dewatering apparatus used in an embodiment of the method for producing a pulp molded article of the present invention.

FIG. 2 is a schematic view of the present step of heating and drying a wet pulp molded article.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 papermaking / dewatering apparatus 10 pulp molded article 2 slurry supply section 21 pulp slurry 3 papermaking section 31, 32 split mold 33 papermaking mold 34 cavity 4 heating fluid supply section 41 supply source 43 heat exchanger 5 discharge section

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tokuo Tsuura 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Prefecture, Japan Kao Co., Ltd. References JP-A-11-314267 (JP, A) JP-A-9-316800 (JP, A) JP-B-35-9669 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) D21J 3/00-3/12

Claims (3)

(57) [Claims] 1. A pulp slurry is supplied into the cavity of a papermaking mold in which a cavity of a predetermined shape is formed, and the inside of the cavity is sucked toward the outside of the papermaking mold to form a wet pulp on the inner surface of the cavity. After forming the molded body, under a state where the inside of the cavity is airtight,
The pressure in the cavity narrowing blowing superheated steam so as to 98kPa [gage] or more, dewatering the pulp molded article, the manufacturing method of the pulp molded article. 2. The method for producing a pulp molded article according to claim 1, wherein dehydration is performed for 0.1 to 10 seconds after the blowing. After 3. A dehydrated the pulp molded article blowing superheated steam into the cavity, superheated steam of the blowing continuation article al, some or all of the blown superheated steam, The method for producing a pulp molded article according to claim 1, wherein the pulp molded article is heated and dried by exhausting air from a blowing port of the blowing.