JP2001032198A - Method for producing pulp molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a pulp molded article capable of improving the drying efficiency of a molded wet molded article and accurately transferring the shape of a mold inner surface to the molded article. SOLUTION: A molded article 7 is formed in a papermaking mold 1, then the molded article 7 is dehydrated in the papermaking mold 1, and the dehydrated wet molded article 7 is demolded from the papermaking mold 1 and dried in a dry mold. And load
In the method for producing a pulp molded article 7 in which the wet molded article 7 is heated and dried in the drying mold,
A method for producing a pulp molded article 7 in which dehydration is performed such that the moisture content of a predetermined portion of the molded article 7 is higher than the moisture content of other parts.

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, and more particularly, to a method for improving the drying efficiency of a molded wet molded article and faithfully transferring the shape of a mold inner surface to the molded article. The present invention relates to a method for producing a pulp molded article.

[0002]

2. Description of the Related Art A wet pulp molded article formed in a papermaking mold is dewatered to a predetermined moisture content, then removed from the papermaking mold and placed in a drying mold. And dried by heating. In this case, the lower the moisture content of the demolded compact, the shorter the drying time in the drying mold.

However, when the moisture content of the molded article is low, the mobility of the pulp is reduced. Therefore, when the shape of the molded article is imparted in a dry mold, the shape of the inner surface of the mold is not faithfully transferred to the molded article. Sometimes. In particular, the transferability of the shape of a screw portion, or the shape of a concavo-convex portion in which characters, figures, symbols, and the like are embossed is reduced.

Accordingly, an object of the present invention is to provide a method for producing a pulp molded article capable of improving the drying efficiency of a molded wet molded article and accurately transferring the shape of the inner surface of the mold to the molded article. And

[0005]

According to the present invention, a molded article is formed in a papermaking mold, and then the molded article is dehydrated in the papermaking mold, and the dehydrated wet molded article is removed from the papermaking mold. In the method for producing a pulp molded article, which is demolded and charged in a drying mold, and heat-drys the molded article in a wet state in the drying mold, a water content of a predetermined portion of the molded article during the dehydration is as follows: The object has been achieved by providing a method for producing a pulp molded article in which dewatering is performed so as to be higher than the water content of other parts.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. FIG. 1 is a process diagram schematically showing a paper making / dewatering step in the first embodiment of the method for producing a pulp molded article of the present invention. In FIG. 1, (a) is a paper making step, and (b) is a drawing. A pressing member insertion step, (c) is a pressure / dehydration step, and (d) is a step of taking out a wet undried molded body.

The present embodiment relates to the production of a hollow container (pulp molded article) in the form of a cylindrical bottle having an open mouth and neck. First, as shown in FIG. A papermaking mold 1 in which a cavity 4 having a predetermined shape is formed by abutting the split molds 2 and 3 is prepared. When the split molds 2 and 3 are abutted with each other, as shown in FIG. 1A, an opening 5 communicating with the cavity 4 from the outside is formed on the upper part of the papermaking mold 1. The mouth 5 has a thread. Each of the split dies 2 and 3 is provided with a plurality of communication holes 6 communicating with the cavities 4 from the outer surfaces thereof. The inner surfaces of the split dies 2 and 3 are covered with nets (not shown) each having a mesh of a predetermined size.

Next, pulp slurry is injected into the cavity 4 through the mouth 5. At the same time, the split dies 2 and 3 are sucked from the outside through the communication holes 6 to depressurize the inside of the cavity 4, suck the moisture in the pulp slurry and deposit pulp fibers on the net covering the inner surface of the cavity 4. As a result, a compact 7 formed by depositing pulp fibers is formed on the net. The molded body 7 has an open mouth and neck 7 a formed near the mouth 5 of the papermaking mold 1.

When a predetermined amount of the pulp slurry is injected into the cavity 4, the injection of the pulp slurry is stopped and the inside of the cavity 4 is completely sucked and dehydrated. Continuing with FIG.
As shown in (b), the inside of the cavity 4 is suctioned and depressurized, and the pressing member 8 is inserted into the molded body 7 through the mouth 5 of the papermaking mold 1.

The pressing member 8 includes a core 81, a core 82 inserted in the core 81, and a rigid protective member 85 surrounding the upper part of the core 81. Then, the core 81 is twisted around the core 82 in advance, and the cross-sectional shape of the pressing member 8 is made smaller than the cross-sectional shape of the mouth-neck portion 7a of the molded body 7 (hereinafter, this state is referred to as a twisted state). ), And the pressing member 8 in the twisted state is inserted into the molded body 7.

FIGS. 2A and 2B are a side view and an enlarged longitudinal sectional view of a main part of the pressing member 8, respectively. Core 81
Is expandable and contractible and has a hollow shape, and a flange 81 ′ is formed at an opening thereof. And flange 8
The core 81 is fixed to these fixed plates by sandwiching 1 ′ between the upper fixed plate 9a and the lower fixed plate 9b. The core 81 used in the present embodiment is formed of a material having elasticity and capable of expanding and contracting. For example, urethane excellent in tensile strength, rebound resilience and elasticity, fluorine-based rubber,
It is formed from a material such as silicone rubber or elastomer. Further, these materials can be formed by coating a stretchable cloth or the like.

The core 82 is constituted by a cylindrical pipe. As shown in FIGS. 2A and 2B, a large number of openings 83 are formed on the side surface of the core. A number of annular idle rings 84 are fitted around the core 82 made of this pipe. There is a predetermined clearance between the core 82 and the idling ring 84 so that the idling ring 84 can rotate.

As shown in FIG. 2A, a lower end 82 'of the core 82 is open, and the core 8 is attached to the lower end 82'.
The lower end 82 'is fixed to the core 81 by fitting a projection 81 "having a predetermined shape formed on the inner surface of the lower end of the core 1. The cross-sectional shape of the projection 81" is more elliptical than circular. A polygon or a polygon is preferable because the rotational torque can be increased. The upper end of the core 82 is also open. This upper end is connected to one end of a tubular joint 9c fixed to the upper fixing plate 9a via a ball bearing (not shown). Joint part 9c
Is connected to driving means (not shown) such as a motor,
By the driving means, the joint portion 9c is rotatable around its central axis. The joint 9c
Is connected via a ball bearing (not shown) to a connection portion 9d used for supplying a pressurized fluid described later. As a result, the connection portion 9d moves to the joint portion 9c.
A communication passage for supplying a pressurized fluid to the opening 83 through the inside of the core 82 is formed.

As shown in FIG. 2A, the upper fixing plate 9a
Protection member 8 having a flange 85a on its lower surface.
5 are arranged. The protection member 85 is made of a rigid body, and is fixed to the upper fixing plate 9 by a fixing member 86 via a flange 85a.
a. The inner diameter of the protection member 85 is larger than the outer diameter of the core 81 in the twisted state and smaller than the inner diameter of the mouth and neck portion 7 a of the molded body 7 formed in the papermaking mold 1. The height of the protective member 85 is adjusted so that the protective member 85 is located at a position facing the mouth and neck 7a of the molded body 7 when the pressing member 8 is inserted into the molded body 7. The protection member 85 is made of metal, resin, or the like.
Specifically, it is formed of a material that has high tensile strength and high rebound resilience and does not easily stretch, for example, urethane, rubber, silicon, or the like.

To twist the core 81 around the core 82, the joint 9c is rotated by the driving means. Since the core 82 is directly connected to the joint 9c,
The core 82 also rotates with the rotation of the joint 9c. However, the connecting portion 9d does not rotate because it is connected to the joint portion 9c via the ball bearing. On the other hand, in the core 81, the flange 81 'of the opening is sandwiched and fixed by the upper and lower fixing plates 9a and 9b and the lower end inner surface is fixed to the lower end 82' of the core 82. As the core 82 rotates under the state, the core 82 is gradually twisted. Since the idle ring 84 is fitted around the core 82, the core 81 is twisted along the surface of the idle ring 84. In this case, since the idling ring 84 is rotatable, it does not rotate with the rotation of the core 82 but idles. As a result, the core 81 twists very smoothly starting from the fixing point with the core 82. The core 82 is twisted around the core 82 by rotating the core 82 by about 2 to 2.5 times, depending on the shapes of the core 81 and the core 82.

When the core 81 is twisted around the core 82,
The cross-sectional shape of the pressing member 8 is the mouth and neck portion 7a of the molded body 7.
Is smaller than the cross-sectional shape. More preferably, the pressure member 8 can be further reduced by suctioning the inside of the core 81 under reduced pressure. Moreover, in the twisted state of the core 81, since the protective member 85 surrounds the periphery of the upper part of the core 81, the pressing member 8 is inserted into the molded body 7 without contacting the mouth and neck 7a, The pulp of the mouth and neck 7a is prevented from falling off. In addition, the shape of the core 81 (shape in a non-twisted state) is substantially the same as or larger than the shape of the cavity 4, so that the expansion magnification of the core 81 can be reduced. It is preferable because durability can be improved.

Returning to FIG. 1, as shown in FIG. 1C, the pressing member 8 is inserted into the molded body 7 and the lower fixing plate 9 is inserted.
The mouth 5 is closed by b. In this state, the protection member 85 of the pressing member 8 is located at a position opposed to the mouth and neck 7a of the molded body 7 and the protection member 8
A predetermined clearance is formed between the head 5 and the mouth and neck 7a. In this state, the joint portion 9c is rotated in the reverse direction to release the twisted state of the core 81. Along with this operation,
A predetermined pressurized fluid is supplied into the core 82 from a pressurized fluid supply source through the connection portion 9d. The supplied pressurized fluid is
Via an opening 83 formed in the side surface of the core 82, a clearance between the core 82 and an idling ring (not shown),
And the inside of the core 81 through the gap between the two idle rings. The split dies 2 and 3 are sucked from the outside together with the supply of the pressurized fluid. Thereby, the core 81 is expanded, and the molded body 7 is pressed against the inner surface of the cavity 4 by the expanded core 81. Since many openings 83 are formed in the side surface of the core 82, the core 81 expands as a whole and simultaneously, and the molded body 7 is pressed uniformly against the inner surface of the cavity 4. However, since the protective member 85 is disposed at the position of the mouth and neck 7a in the molded body 7, the mouth and neck 7a
Pressing by the core 81 is hindered. As the pressurized fluid used to expand the core 81, for example, compressed air (heated air), oil (heated oil), and various other liquids are used. The supply pressure of the pressurized fluid is preferably 0.01 to 5 MPa, particularly preferably 0.1 to 3 MPa.

Due to the pressing by the core 81, the inner surface shape of the cavity 4 is transferred to the molded body 7, and the pressure dehydration proceeds. As described above, since the molded body 7 is pressed from the inside of the cavity 4 to the inner surface of the cavity 4, dehydration of the molded body 7 is performed more efficiently than suction dehydration. Moreover, even if the shape of the inner surface of the cavity 4 is complicated, the shape of the inner surface of the cavity 4 is accurately transferred to the molded body 7. Further, the molded body 7 is pressed with substantially the same pressure in any part except the mouth and neck 7a. The pressure at which the mouth and neck 7a is pressed is lower than the pressure at other parts of the molded body 7. As a result, the moisture content of the mouth and neck portion 7a of the molded body 7 becomes higher than that of the other portions, and the thickness of the molded body 7 other than the mouth and neck portion 7a becomes uniform. In the present embodiment, the water content of the mouth and neck 7a in the molded body 7 is:
It is preferably from 65 to 80% by weight, particularly from 70 to 75% by weight, from the viewpoint of balance between the shape retention of the mouth and neck 7a and the ease of imparting a shape in the heating and drying step described later. Molded body 7
The water content of the portion other than the mouth and neck 7a is 40 to 70
%, Especially 55 to 65% by weight,
Is preferred from the viewpoint that the network pattern of the net is not transferred to the surface and the surface property is improved, and the efficiency in the heating and drying step is good.

When the shape of the inner surface of the cavity 4 is sufficiently transferred to the molded body 7 and the molded body 7 can be dehydrated to a predetermined moisture content, as shown in FIG. Pull out. Along with this operation, the joint part 9 c is rotated to rotate the core 82, and the core 81 is twisted around the core 82. As a result, the core 81 returns to the twisted state before insertion. Next, the pressing member 8 is taken out of the cavity 4.
Since the pressing member 8 has the same size as that before being inserted into the cavity 4, it is taken out of the molded body 7 without contacting the mouth and neck 7 a of the molded body 7 and the pulp of the mouth and neck 7 a is removed. Peeling is prevented. Next, the papermaking mold 1 is opened together with the removal of the pressing member 8, and the wet pulp molded article 7 in a wet state is released. In this molded body 7,
The water content of the mouth and neck 7 is higher than the water content of the other parts.

The demolded molded body 7 is then subjected to a heating and drying step. In the heating and drying step, a final shape is imparted to the molded body and drying is performed. In the heating and drying step, substantially the same operation as in the paper making and dewatering step shown in FIG. 1 is performed, except that a heating mold in a heated state is used without performing paper making and dewatering. That is, first, a heating mold in which a cavity having a shape corresponding to the outer shape of the pulp molded article to be molded is formed by abutting a pair of split molds, and the heating mold is heated to a predetermined temperature. And heat it. In the present embodiment, the cavity shape of the heating mold and the cavity shape of the papermaking mold are the same. The wet undried molded body 7 is loaded into the cavity of the heated heating mold, and the molded body 7 is pressed by using the same pressing member as the pressing member 8 under the same twisting state. Then, the shape of the cavity inner surface is transferred to the molded body 7 and the molded body 7 is heated and dried. However, unlike the pressing member 8 used in the paper making / dehydrating step, the protective member 85 is not attached to the pressing member used in the heating and drying step. Therefore, in the pressing by the pressing member, the entire molded body 7 is pressed unlike the paper making / dewatering step. As described above, in the molded body 7, since the water content of the mouth and neck 7 is higher than the water content of the other parts, the mobility of the pulp fiber is high in the mouth and neck 7 having a high water content, By the pressing by the pressing member, the shape of the thread formed at the mouth of the heating mold is faithfully transferred to the mouth and neck 7. On the other hand, the portion of the molded body 7 excluding the mouth and neck 7a has already been dehydrated to a predetermined moisture content in the paper making and dewatering step, and is therefore quickly dried. As described above, according to the present embodiment, the drying efficiency of the wet molded article is improved, and the complicated shape of the inner surface of the mold is faithfully transferred to the molded article. When the entire molded body 7 has been dried to a predetermined moisture content, the heating mold is opened and the pulp molded body is taken out.

Next, a second embodiment of the present invention will be described. In the second embodiment, only the points different from the first embodiment will be described, and as for the points which are not particularly described, the detailed description regarding the first embodiment will be appropriately applied.

The second embodiment is different from the first embodiment in that a pressing member used in the second embodiment has a first member.
Unlike the pressing member 8 used in the paper making / dewatering step of the embodiment, the protection member 85 is not attached. Instead of this, in the pressing member 8 used in the second embodiment, the thickness of the portion of the core 81 that presses the mouth-and-neck portion 7a of the molded body 7 (hereinafter referred to as the mouth-and-neck portion) is different from that of the core 81. It is thicker than the part. That is, when the core 81 expands, the portion of the molded body 7 that presses the mouth-neck portion 7a (the mouth-neck portion corresponding portion) is thicker than the other portions, and the mouth-neck portion corresponding portion. Are less likely to expand than other portions of the core 81. As a result, in the pressurized dehydration of the undried molded body 7 by the core 81, the pressure of pressing the mouth and neck 7a by the mouth and neck corresponding portion of the core 81 becomes lower than other parts of the core 81. In addition, the moisture content of the mouth and neck 7a of the molded body 7 is lower than the moisture content of other parts of the molded body 7. The water content of the mouth and neck 7a and the water content of the other portions in the molded body 7 are the same as those in the first embodiment.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the portion that increases the water content during dehydration is the mouth and neck portion 7a of the molded body 7, but any portion may be used as long as the shape of the inner surface of the cavity 4 is complicated. For example, when it is desired to transfer a concavo-convex portion in which characters, figures, symbols, and the like are embossed on the body of the molded body 7, the water content of the body is dehydrated so as to be higher than other parts of the molded body. do it.

In adjusting the moisture content of the molded body 7 during dehydration, suction dehydration with a locally changed suction force is used instead of pressure dehydration using a core as in the above embodiment. Is also good.

The production method of the present invention may be applied to the production of a box-shaped carton having a wide opening.

When a molded body having a wide opening and having a shape that does not require much expansion and contraction of the core 81 is formed, the core 81 only needs to have expandable and contractible flexibility. (Expansion contraction property) is not required. Such materials include
For example, polyethylene, polypropylene and the like can be mentioned.

The pressing members (core, core, etc.) used in the papermaking step and the heating and drying step may be of different shapes and materials.

[0028]

According to the present invention, there is provided a method for producing a pulp molded article capable of improving the drying efficiency of a molded wet molded article and accurately transferring the shape of the inner surface of the mold to the molded article. .

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing a paper making / dewatering step in a first embodiment of a pulp molded article of the present invention.

FIG. 2A is a side view of a pressing member, and FIG.
FIG. 2B is an enlarged vertical sectional view of a main part in FIG.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 mold 2, 30 split mold 4 cavity 5 mouth 6 communication hole 7 pulp layer 8 pressing member 81 core 82 core 83 opening hole 84 idling ring 85 protective member 9c joint portion

Claims (5)

[Claims] 1. A molded article is formed in a papermaking mold, and after the molded article is dehydrated in the papermaking mold, the dehydrated wet molded article is removed from the papermaking mold and placed in a drying mold. In the method for producing a pulp molded article, wherein the molded article in a wet state is charged and heated and dried in the drying mold, the moisture content of a predetermined portion of the molded article is lower than the moisture content of the other portions during the dehydration. A method for producing a pulp molded article in which dehydration is performed to increase the height. 2. An expandable and contractible hollow core is inserted into the molded body, and the core is expanded to press the molded body against the inner surface of a papermaking mold to perform pressure dehydration. 2. The method for producing a pulp molded article according to claim 1, wherein the pressure of the predetermined part of the molded article by the core is set lower than other parts. 3. The method for producing a pulp molded article according to claim 2, wherein a protective member for preventing the core from being pressed by the core is disposed at the predetermined section of the molded article during the pressure dehydration. 4. The method for producing a pulp molded product according to claim 2, wherein a portion of the core pressing the predetermined portion of the molded product is thicker than other portions. 5. A hollow container having a mouth, a neck, and a body, wherein the molded body is opened, and dewatering so that the water content in the vicinity of the mouth, neck, or body is higher than the water content in other parts. The method for producing a pulp molded article according to any one of claims 1 to 4, wherein