JP3125993B2 - Method for producing pulp molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a pulp molded article.

[0002]

2. Description of the Related Art Plastic materials are generally used as raw materials for containers such as containers and bottles having a lid, because they have excellent moldability and are advantageous in terms of productivity. ing. However, since plastic containers have various problems in disposal, pulp containers can be considered as an alternative, and such containers are easy to dispose, and are manufactured using waste paper as a raw material. It is economical because it is possible.

As a technique relating to a method of manufacturing a pulp container, for example, a technique described in Japanese Patent Application Laid-Open No. 9-316800 is known. According to the method described in this publication, a predetermined amount of slurry in a pulp storage tank is measured and temporarily stored in a supply tank, and the slurry in the supply tank is injected into a mold using pressurized air. Is pressed by a pressurized cylinder to pressurize and dewater the pulp layer to precisely control the weight of the product. However, in this method, the slurry is injected between the fixed mold and the movable mold, and the molded body is obtained by closing the mold. Therefore, even if a dish or a tray with a shallow bottom can be manufactured, the side wall can be manufactured. It is extremely difficult to produce a formed body having a near right angle and a deep bottom with a uniform thickness distribution. Further, the method described in the above publication employs a so-called batch method in which a predetermined amount of slurry in a pulp storage tank is measured and temporarily stored in a supply tank, so that a satisfactory production rate cannot be obtained. Sometimes.

[0004] Japanese Patent Publication No. 35-9669 and Japanese Patent Publication No. 42-9086 also disclose a method of injecting a slurry into a cavity by applying pressure. However, according to the methods described in these publications, the slurry is merely injected into the cavity by a pressing force, and the inside of the cavity is not pressurized. It is difficult to manufacture with a good thickness distribution.

Accordingly, an object of the present invention is to provide a method for producing a pulp molded article capable of producing a molded article having a uniform thickness more quickly and stably.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a metal mold in which a cavity having a predetermined shape is formed by abutting a pair of papermaking split dies having a plurality of communication passages communicating the outside and the inside. The pulp slurry injected into the cavity of the mold is pressurized and injected while measuring the flow rate of the pulp slurry to pressurize the interior of the cavity to a predetermined pressure. The above object has been achieved by providing a method for producing a pulp molded article in which gas is injected into a cavity.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a pulp molded article of the present invention will be described based on preferred embodiments with reference to the drawings. FIG. 1 is a schematic diagram of a papermaking apparatus preferably used in a method of manufacturing a pulp molded article (hereinafter, simply referred to as a molded article) of the present embodiment. The papermaking apparatus 1 includes a slurry supply unit 2 and a papermaking apparatus. It is roughly divided into section 3.

The slurry supply unit 2 stores a pulp slurry (hereinafter, simply referred to as a slurry) 21 and
A slurry storage tank 23 provided with a stirrer 22; and an injection pump 2 for sucking the slurry 21 from the slurry storage tank 23 and injecting the slurry 21 into a mold 34 described below under pressure.
4. A flow meter 25 for measuring the flow rate of the slurry 21; a first three-way valve 26 for changing the flow path of the slurry 21 to one of the mold direction and the slurry storage tank 23 direction according to an instruction from the flow meter 25; A second three-way valve 27 for switching the flow of the slurry 21 and the air into the mold 34 is provided. The slurry storage tank 23, the injection pump 24, the flow meter 25, the first three-way valve 26, and the second three-way valve 27 are connected in series in this order by a pipe 28.

The papermaking section 3 is formed by abutting two papermaking mold dies 31 and 32 in each of which a plurality of communication paths (not shown) which form a set of two and communicate the outside with the inside are formed. A mold 34 in which a cavity 33 having a shape corresponding to the outer shape of a molded body to be molded is formed; a drain 35 for discharging water from slurry injected into the cavity 33;
A suction pump 36 for sucking the inside of the cavity 33 and an on-off valve 37 for opening and closing the mold 34 and the suction pump 36 are provided. From the slurry supply unit 2, the cavity 33
The supply of the slurry into the inside is performed through a pipe 28 connected to the second three-way valve 27 and a pipe 29 inserted into the cavity.

The mold 34 has a cavity 33 formed therein by abutting the split molds 31 and 32, and a slurry flow communicating with the cavity 33 and opening to the outside at a position above the cavity 33. An inlet 38 is formed. Then, through the slurry inflow port 38, the in-cavity insertion pipe line 29 connected to the second three-way valve 27 is inserted into the cavity 33.

The method of manufacturing a molded article using the above-described papermaking apparatus 1 will be described. First, the injection pump 24 is started, the slurry 21 is sucked from the slurry storage tank 23, and the flow meter 25, the first three-way valve 26 and The slurry 21 is injected under pressure into the cavity 33 of the mold 34 via the second three-way valve 27. At that time, the flow rate of the slurry 21 is measured in-line by the flow meter 25. The slurry is injected into the cavity 33 under pressure and the upper end of the slurry inlet 38 is closed.
3 is pressurized to a predetermined pressure. Therefore, the cavity 33
The water in the slurry injected into the inside of the mold is connected to a communication path (not shown) communicating from the inner surface of the cavity 33 to the outside of the mold 34.
Then, it is discharged to the outside of the mold 34 through the drain 35. In this case, since the supply amount of the slurry is larger than the discharge amount of the water in the slurry, the inside of the cavity 33 is gradually filled with the slurry. A pulp layer (not shown) is formed by depositing pulp fibers contained in the slurry on the inner surface of the cavity 33 together with the discharge of the water in the slurry. As mentioned above, the slurry is injected under pressure,
Since the inside of the cavity 33 is pressurized to a predetermined pressure, the pressure of the slurry on the inner surface of the cavity 33 is the same at any position. As a result, Japanese Patent Publication No. 35-9669 and Japanese Patent Publication No.
Unlike the method described in Japanese Patent Application Laid-Open No. 9086, even when a molded body having a side wall angle close to a right angle and a deep bottom is obtained, a pulp layer having a uniform thickness is formed on the inner surface of the cavity 33, and the final pulp layer is formed. Thus, the thickness of the molded article obtained becomes uniform. Further, Japanese Unexamined Patent Publication No. 9-31680 described in the section of the prior art described above.
Unlike the method described in Japanese Patent Publication No. 0, the amount of the slurry injected into the cavity 33 is measured in-line, so that the paper can be formed at a higher speed. Moreover, since the slurry is injected under pressure and water is forcibly discharged,
Paper can be made even faster. In addition, in the method described in the above-mentioned publication, a supply tank having a volume corresponding to that is required when obtaining a molded article having a large weight, but such a supply tank is unnecessary in the method of the present invention. ,
Great flexibility when changing the weight of the molded body.

The pressure at which the slurry is injected into the cavity 33 is set at 0.0 because the pulp layer having a uniform thickness is formed on the inner surface of the cavity 33 and the paper is formed at a higher speed.
It is preferably from 1 to 5 MPa, particularly preferably from 0.01 to 3 MPa.

When the slurry used has a concentration of 0.1 to 3% by weight, particularly 0.3 to 2% by weight, convection in the cavity becomes easy when the slurry is injected under pressure, and the slurry becomes more uniform. It is preferable because the pulp layer is formed with a thickness.

When the injection of the predetermined amount of slurry is completed, the flow meter 25 issues a flow switching command to the first three-way valve 26. According to this command, the flow path of the first three-way valve 26 is switched, and the slurry returns to the slurry storage tank 23 via the return line 28 '.

When the injection of the slurry is completed, the drain 35 is closed and the drainage is stopped. Further, the flow path of the second three-way valve 27 is switched to form a flow path in which the air press-fitting pipe 28 "and the insertion pipe 29 in the cavity communicate with each other.
Air is injected as a gas into the cavity 33 through the 8 ″ and the insertion pipe 29 into the cavity. At the same time, the suction pump 36 is activated, the on-off valve 37 is opened, and the inside of the cavity 33 is sucked. By the operation of
The water in the cavity 33 is completely sucked, the water in the pulp layer formed on the inner surface of the cavity 33 is also sucked, and the pulp layer is dehydrated to a predetermined moisture content. At the time of suction dehydration of the pulp layer, since the inside of the cavity 33 is in a pressurized state by pressurizing air, the pulp layer is
The inner surface of the cavity 33 is more strongly pressed. As a result, the thickness of the pulp layer becomes more uniform, and the shape of the inner surface of the cavity 33 is accurately transferred to the pulp layer. Further, suction dehydration of water is also performed promptly.

The pressure at which air is injected into the cavity 33 is 0.01 to 5 MPa, particularly 0.01 to 3 MPa, in order to make the thickness of the pulp layer more uniform and to quickly dehydrate the pulp layer. It is preferred that

FIG. 2A shows a state in which the pulp layer 15 is formed in the cavity 33. After this, FIG.
The step shown in (d) is performed. Here, FIG. 2B shows a core insertion step, FIG. 2C shows a pressurization / dehydration step, and FIG.
Is a step of opening the mold and taking out an intermediate of the molded body.
2 (a) to 2 (d), the mold 3 is used for simplicity.
Only 4 is shown, and other members are omitted.

After the pulp layer 15 has been formed in the cavity 33, the insertion pipe 29 in the cavity is pulled out, and then, as shown in FIG. The core 16, which is freely and hollow, is inserted into the cavity 33. Core 16
Is used to give the inner shape of the cavity 33 by inflating it like a balloon in the cavity 33 and pressing the pulp layer 15 against the inner surface of the cavity 33. Therefore, the core 16 is formed of urethane, fluorine-based rubber, silicone-based rubber, elastomer, or the like having excellent tensile strength, rebound resilience, elasticity, and the like.

Next, as shown in FIG.
A pressurized fluid is supplied to the inside to expand the core 16, and the expanded core 16 presses the pulp layer 15 against the inner surface of the cavity 33. Then, the pulp layer 15 becomes the expanded core 1.
6 further presses against the inner surface of the cavity 33,
The inner shape of the cavity 33 is transferred to the pulp layer 15 and dehydration further proceeds. Thus, cavity 3
Since the pulp layer 15 is pressed against the inner surface of the cavity 33 from the inside of the cavity 3, the shape of the inner surface of the cavity 33 is accurately transferred to the pulp layer 15 even if the shape of the inner surface of the cavity 33 is complicated. . In addition, unlike the conventional manufacturing method, there is no need to use a bonding step, so that the obtained molded article does not have a seam or a thick portion due to bonding. As a result, the strength of the obtained molded body is increased and the appearance impression is improved. As the pressurized fluid used to expand the core 16, for example, compressed air (heated air), oil (heated oil), and other various liquids are used. The pressure at which the pressurized fluid is supplied is set to 0.1.
It is preferable that the pressure is from 0.01 to 5 MPa, particularly from 0.1 to 3 MPa.

When the shape of the inner surface of the cavity 33 is sufficiently transferred to the pulp layer 15 and the pulp layer 15 can be dehydrated to a predetermined moisture content, as shown in FIG. Pull out. Then, the core 16 automatically shrinks and returns to its original size. Next, the contracted core 16 is taken out of the cavity 33, and the mold 34 is further opened to take out the wet molded intermediate 15 ′ having a predetermined moisture content.

The removed intermediate 15 'is then subjected to a heating and drying step. In the heating / drying step, the same operations as those in the paper making steps shown in FIGS. 2A to 2D are performed except that the paper making and dewatering are not performed. That is, first, the intermediate body in a wet state is loaded in a mold in which a cavity having a shape corresponding to the outer shape of the molded body 10 to be molded is formed by abutting a pair of split molds.

Next, a core similar to the core 16 used in the papermaking process is inserted into the intermediate body, and a pressurized fluid is supplied into the core to expand the core, thereby expanding the core. The core presses the intermediate against the inner surface of the cavity. The material of the core and the supply pressure of the pressurized fluid can be the same as in the above-described papermaking process. In this state, the mold is heated to a predetermined temperature, and the intermediate is dried by heating. When the intermediate is sufficiently dried, drain the pressurized fluid in the core,
Shrink and remove the core. Further, the mold is opened, and the molded article 10 is taken out.

The molded body 10 thus obtained is a container suitable for accommodating contents such as a powdery body and a granular body. As shown in FIG. Further, it has a body portion 12 and a bottom portion 13 and has a cylindrical shape, and the diameter of the opening portion 11 is smaller than the diameter of the body portion 12. Further, the body 12 is formed at right angles to the bottom 13. That is, the taper angle of the body 12 is set to about 0 degrees. The molded body 10 has an overall height of 50 m.
m, preferably 100 mm or more.

According to the above-described manufacturing method, it is possible to easily manufacture a formed body having a sidewall close to a right angle and a deep bottom with a uniform thickness distribution. Furthermore, there are no seams or thick portions due to bonding. As a result, the mechanical strength of the molded body 10 is improved, and the appearance impression is also improved. Further, the outer surface and the inner surface of the obtained molded body 10 are made smooth. Thereby, for example, when a plastic layer or a coating layer is formed on the outer surface and / or the inner surface, the adhesiveness is improved, and printing on the outer surface can be performed easily and neatly. Further, the appearance impression is further improved.
In the present specification, “smooth” means that the center line average roughness (Ra) of the surface irregularities on the outer surface or inner surface of the molded product is 5%.
0 μm or less and the maximum height (Ry) is 500 μm or less (a value measured in accordance with JIS B 0601). Surfcom 120A for surface roughness measurement
Using [manufactured by Tokyo Seimitsu Co., Ltd.], the measurement conditions were cutoff: 0.80 mm, measurement length: 10.00 mm, filter: 2CR, measurement magnification: 500, tilt correction: linear, and polarity: standard. .

The density of the molded body 10 (that is, the density of the meat portion of the molded body 10) is 0.4 to 2.0 g / c.
By setting it to m ³ , mechanical properties such as tensile strength and compressive strength of the molded body 10 are satisfied, and appropriate rigidity can be given. The density of the molded body 10 is more preferably 0.6 to
By adjusting the amount to 1.5 g / cm ³ , the usability can be improved.

When the moisture permeability of the molded body 10 based on JIS Z0208 is set to 100 g / (m ² · 24 hr) or less, the moisture in the atmosphere is hardly absorbed, the appropriate rigidity is maintained, and the content is reduced. Can be effectively prevented from being impaired by the absorption of moisture. In particular, when the moisture permeability is set to 50 g / (m ² · 24 hr) or less, the storage stability of the contents is further improved.

The slurry used in the above-mentioned production method is as follows:
It may be composed of pulp fiber and water, or in addition to these, inorganic substances such as talc and kaolinite, inorganic fibers such as glass fiber and carbon fiber, powder or fiber of synthetic resin such as polyolefin, non-wood or vegetable fiber And components such as polysaccharides. The amount of these components is 1 to 7 with respect to the total amount of the pulp fiber and the components.
It is preferably 0% by weight, particularly preferably 5 to 50% by weight.

The present invention is not limited to the above-described embodiment.
By using superheated steam instead of the air injected into 3,
The temperature of the moisture contained in the intermediate of the molded article after papermaking is quickly increased, the moisture content of the molded article can be quickly reduced, and the molded article can be obtained at high speed. Further, the inside of the cavity 33 may be suctioned by the suction pump 36 at the same time as the pressure injection of the slurry for the purpose of increasing the papermaking speed. As the gas to be injected into the cavity 33, it is convenient to use air, but a gas other than air, for example, heated air, superheated steam, or various inert gases may be used. Further, after the slurry is injected under pressure and before the gas is injected, a predetermined amount of water or an extremely thin slurry is injected into the cavity 33 and then dewatered to reduce the slurry concentration remaining in the cavity 33. Can be. As a result, since the slurry is drained while lowering the water level of the slurry in the cavity 33 by gas injection, the thickness of the molded body can be made more uniform. Further, the molded product obtained by the production method of the present invention may be a substantially rectangular parallelepiped carton-shaped container in which the cross-sectional shape of the opening and the cross-sectional shape of the body are substantially the same. In addition to the use as a container used to store contents, the present invention may be applied to uses such as objects such as ornaments.

[0029]

According to the present invention, there is provided a method for producing a pulp molded article capable of producing a molded article having a uniform thickness more quickly and stably. According to the production method of the present invention,
Since a molded body can be obtained at a higher speed, manufacturing costs can be reduced. Further, since the molded article obtained by the production method of the present invention is mainly composed of pulp, it can be reused or incinerated after use, which leads to reduction of waste.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a papermaking apparatus preferably used in a method for producing a pulp molded article of the present invention.

FIGS. 2A to 2D are process diagrams sequentially showing a paper making process in the method for producing a pulp molded article of the present invention.

FIG. 3 is a perspective view showing an example of a molded article obtained by the method for producing a pulp molded article of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 papermaking apparatus 2 slurry supply section 3 papermaking section 15 pulp layer 16 core 21 pulp slurry 31 split mold 32 split mold 33 cavity 34 mold

Continuation of the front page (56) References JP-A-9-316800 (JP, A) JP-B-35-6996 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21J 3 / Ten

Claims (7)

(57) [Claims] 1. A mold for forming a cavity having a predetermined shape is injected into a cavity of a mold having a predetermined shape by abutting a pair of papermaking molds each having a plurality of communication paths communicating the outside and the inside. that the pulp slurry, the pulp slurry
And pressurizing the inside of the cavity to a predetermined pressure while measuring the flow rate of the pulp slurry. Then, after completing the injection of a predetermined amount of the pulp slurry, a gas is pressed into the cavity to produce a pulp molded article. 2. The method for producing a pulp molded article according to claim 1, wherein the inside of the cavity is sucked simultaneously with or after the pressure of the pulp slurry is injected into the cavity. 3. The method for producing a pulp molded article according to claim 1, wherein the inside of the cavity is sucked while air is pressed into the cavity. 4. The method according to claim 1 , further comprising the step of:
The method for producing a pulp molded article according to any one of claims 1 to 3 , wherein a core having a hollow shape is inserted into the inside, and the core is expanded . 5. A supply of 0.01 to 5 MPa into the core.
A fluid is supplied under pressure to expand the core.
The method for producing a pulp molded article according to any one of the above. 6. The pulp slurry having a concentration of 0.1-3.
The pulp mold according to any one of claims 1 to 5, which is a weight percent.
Manufacturing method of molded body. 7. The pulp slurry of 0.01 to 5M
The pressure injection at a pressure of Pa is performed according to any one of claims 1 to 6.
A method for producing a pulp molded article.