JP2001329500A - Method for producing molded pulp product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded pulp product with homogeneous thickness even if the designed shape is a complex one such as curved surface. SOLUTION: This method for producing the molded pulp product by feeding a pulp slurry into a cavity of a pair of split molds capable of forming the cavity having a prescribed shape in the interior to form a pulp laminate, and dehydrating the resultant pulp laminate, comprises regulating the feeding concentration A of the pulp slurry and the feeding flow rate B of the pulp slurry may satisfy the formula (1): Ln(A)+3<=B<=20Ln(A)+200 (1) (wherein, A is the concentration [wt.%] of the fed pulp slurry; B is the flow rate [L/min/cavity volume L] of the fed pulp slurry).

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 Plastics having excellent moldability and high productivity are used for packaging containers such as containers and bottles having a lid. However, since plastic containers have various problems in disposal, it has been considered to use a pulp mold container that papers fibers such as pulp as a slurry raw material as an alternative. Slurry raw materials are mainly used paper such as newspapers, magazines, corrugated cardboard, and copy paper. Uses include cushioning materials for chicken and eggs, agricultural products such as melon, gift packages such as canned foods, small appliances, precision machine parts packaging materials. It is widely used as a buffer and fixing material. However, the pulp molded article for such an application is a product in which the surface of the molded article is rough and the dimensional accuracy and the like are not so required, and the dimensional and dimensional accuracy and surface roughness of a plastic container cannot be obtained. .

[0003] An object of the present invention is to provide a pulp molded article having a uniform thickness even in a complicated design shape such as a curved surface. Another object of the present invention is to provide a method for producing a pulp molded article capable of stably producing a pulp molded article.

[0004]

SUMMARY OF THE INVENTION The present invention comprises a set of split dies in which a cavity having a predetermined shape is formed, and a pulp slurry is supplied into the cavity to form a pulp laminate. A method for producing a pulp molded article for dewatering a pulp laminate, wherein a pulp slurry supply concentration A of the pulp slurry and a pulp slurry supply flow rate B to be supplied are represented by the following formula (1): The object has been achieved by providing a method.

[0005]

(Equation 2)

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail. 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 paper making section 3 is formed by abutting a pair of paper making split dies 31 and 32 each having a plurality of communication passages (see FIG. 2) communicating from the outside to the inside, thereby forming an outer shape of a formed body to be formed. A mold 34 in which a cavity 33 having a shape corresponding to the above 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 a mold 34 and a suction pump 36. And an on-off valve 37 for opening and closing between the two. The supply of the slurry from the slurry supply unit 2 into the cavity 33 is performed by the pipelines 2 connected to the second three-way valves 27, respectively.
8 and through the insertion line 29 in 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 is formed at an upper position thereof. 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.

A 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.
The water in the slurry injected into the cavity 3
Is discharged to the outside of the mold 34 through a communication passage (not shown) communicating with the outside of the mold 34 and the drain 35 from the inner surface of the mold 34. At the same time, pulp fibers contained in the slurry are deposited on the inner surface of the cavity 33 to form the pulp layer 15 (see FIG. 2). As described above, since the slurry is injected under pressure, the pressure of the slurry on the inner surface of the cavity 33 is the same at any position. As a result, even when a compact having a side wall angle close to a right angle and a deep bottom is obtained, the pulp layer 15 having a uniform thickness is formed on the inner surface of the cavity 33, and the finally obtained compact is obtained. The thickness is also uniform. Further, unlike the method described in JP-A-8-316800 described in the section of the related art, the amount of the pulp slurry injected into the cavity 33 is measured in-line, so that the pulp slurry supply amount is reduced. Since there is no need to weigh in the weighing tank,
Paper can be made faster. In addition, since the slurry is injected under pressure and water is forcibly discharged, papermaking can be performed at a higher speed. In addition, according to the method described in the above-mentioned publication, when a large molded body is to be obtained, a supply tank having a volume corresponding to that is necessary,
In the method of the present invention, since such a supply tank is not required, the flexibility in performing the step of changing the weight and the like of the molded body and the shape of the molded body can be easily changed.

From the slurry storage tank 23 to the cavity 3
The slurry concentration at the time of injecting the slurry into 3 was 0.1
It is preferably from 6 to 6% by weight, particularly preferably from 0.1 to 3% by weight. If the slurry concentration is less than 0.1% by weight, the slurry is difficult to deposit in a paper-mesh network, so that the paper-making efficiency becomes poor such that the paper-making time becomes long or the thickness of the molded product becomes uneven, and the slurry concentration becomes uniform. It is difficult to make a thick molded product. Further, when the slurry concentration is more than 6% by weight, the thickness of the formed body becomes uneven, and the surface smoothness of the inner surface of the formed body is deteriorated,
In some cases, it is difficult to produce a thin molded body having a thickness of 2 mm or less.

The flow rate at the time of supplying the slurry into the cavity 33 is preferably within a range satisfying the following equation (1).

[0013]

(Equation 3)

If the pulp slurry supply flow rate B deviates from the formula (1), a hole is formed in a part of the molded body when the molded body is formed into a hollow shape, and the pulp slurry has an uneven thickness. In some cases, inconveniences such as a decrease in the thickness of the bottom portion and the nozzle portion may occur. It is particularly preferable that the pulp slurry supply flow rate B is in a range satisfying the following expression (2) from the viewpoint of the mechanical strength of the molded body.

[0015]

(Equation 4)

The pressure at which the slurry is injected into the cavity 33 is such that the pulp layer 15 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 0.01 to 5 MPa, particularly preferably 0.01 to 3 MPa.

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 flow path of the second three-way valve 27 is switched, and the air press-fitting pipe 28 ''
A flow path is formed in which the and the in-cavity insertion pipe 29 communicate with each other. Then, air is press-fitted into the cavity 33 from an air supply source (not shown) through the air press-fitting pipe 28 ″ and the insertion pipe 29 in the cavity. Suction pump 3
6 is activated, the on-off valve 37 is opened, and the cavity 3 is opened.
The inside of 3 is sucked. By this series of operations, the liquid level of the pulp slurry filled in the cavity 33 can be quickly lowered. Further, the drain 35 is closed, the moisture in the cavity 33 is completely sucked, the moisture in the pulp layer formed on the inner surface of the cavity 33 is also sucked, and the pulp layer 15 is dehydrated to a predetermined moisture content. You. During suction dehydration of the pulp layer 15, the cavity 3
Since the inside of 3 is pressurized by air injection,
The slurry is easily convected in the cavity 33, the pulp layer is pressed more strongly against the inner surface of the cavity 33, and the thickness of the pulp layer becomes more uniform. Further, the shape of the inner surface of the cavity 33 is accurately transferred to the pulp layer 15. Further, suction dehydration of water is also performed promptly.

The pressure at the time of injecting air into the cavity 33 is 0.01 to 5 MPa in order to make the thickness of the pulp layer 15 more uniform and to quickly dehydrate the pulp layer.
a, particularly preferably 0.01 to 3 MPa.

FIG. 2A shows a state in which the pulp slurry is supplied into the cavity 33 and the pulp layer 15 is formed.
Thereafter, the steps shown in FIGS. 2B to 2D are performed. Here, FIG. 2B shows a core insertion step, and FIG.
The dehydration step, FIG. 2D, is a step of opening the mold and taking out an intermediate of the molded body.

The papermaking surfaces of the papermaking molds 31 and 32 are covered with a papermaking net (not shown). 2 for papermaking net
It is preferably a heavy papermaking net, and a molded article with clogging and uniform thickness can be obtained. Furthermore, it is more preferable to cover the papermaking surface of the papermaking mold with a sparse papermaking net over a dense papermaking net, and it is even better to obtain a molded body with clogging and uniform thickness, This is preferable because the molded body can be easily removed from the papermaking mold.

A plurality of communication holes 40 are formed on the papermaking surface of the papermaking dies 31, 32 facing the cavity 33. A manifold 41 is formed inside the paper splitting dies 31, 32, and communicates with the communication hole 40. The manifold 41 communicates with the outside through a discharge port. Thus, the communication hole 40, the manifold 41, and the discharge port 42 form a communication path for communicating with the outside of the papermaking split die combined with the cavity 33. The outlet 42 communicates with the drain 35 and the on-off valve 37.

After the pulp layer 15 is 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. After supplying the pulp slurry into the cavity 33, the core 16
Is inserted, the pulp slurry in the cavity 33 convects uniformly throughout the cavity, so that the pulp layer 15 having a uniform thickness can be formed.

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 good, which is preferable. As the pressurized fluid used to expand the core 16, for example, compressed air (heated air), oil, and other various liquids are used. The pressure for supplying the pressurized fluid is
It is preferable that the pressure be 0.01 to 5 MPa, particularly 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 / dewatering is not performed and the cavity is not covered with the paper making net. That is, first, the intermediate body in a wet state is loaded into 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. As described above, even during drying, the intermediate body 15 'is dried while pressing the inner surface and the outer surface by the mold and the core, so that the shape of the mold is more accurately transferred and the surface of the molded body is smoothed. A molded article having excellent properties can be obtained. In the present invention, “smooth” means that the centerline average roughness (Ra) of the surface irregularities on the outer surface or inner surface of the molded article is 50 μm or less and the maximum height (Ry) is 500 μm or less. .

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. The molded body 10 has an overall height of 50 m.
m 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.

The density of the molded body 10 (that is, the density of the meat portion of the molded body 10) is set to 0.4 to 2 g / cm ^3.
By doing so, 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 1.5.
By using g / cm ³ , the feeling of use can be improved.

Further, by setting the moisture permeability of the molded body 10 to 100 g / (m ² · 24 hr) or less based on JIS Z0208, it becomes difficult to absorb moisture in the atmosphere, and appropriate rigidity is maintained, and 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 heated air or heated steam instead of the air injected into 3, the moisture content of the intermediate of the molded article after papermaking can be reduced, and the molded article can be obtained at high speed. Also,
In order to increase the papermaking speed, the inside of the cavity 33 may be suctioned by the suction pump 36 at the same time as the slurry is injected under pressure. 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. Further, in addition to the use as a container used for accommodating the contents, the present invention may be applied to a use such as a container for a printing toner having a plurality of openings and an object such as an ornament.

[0034]

EXAMPLES The pulp molded article of the above embodiment was produced according to the above-mentioned production method, and the average thickness of the obtained molded article and the smoothness of the inner surface of the molded article were evaluated by the following procedures.
The volume and the weight after drying of each compact are as follows.
The evaluation results are shown in [Table 1]. Form A: 500 mL volume, Examples 1-8 and Comparative Example 1: 27-30 g weight Example 9-19 and Comparative Example 2: 38-42 g weight Form B: 600 mL volume, weight about 40 g Form C: 800 mL volume, weight About 45g

[0035] [average thickness] total height of the pulp molded article as shown in Figure 3: dividing the h ₀ longitudinally 3 equal parts, to each upper, middle, and lower. The thickness of the middle part was measured n = 5 times at intervals of about 10 mm with a micrometer,
The average value is defined as an average thickness T _ave , the upper and lower portions are similarly measured for thickness, the minimum thickness is defined as T _min , and the thickness ratio X =
(T _min / T _ave ). 0.7 ≦ X: It has an excellent wall thickness balance, excellent mechanical properties such as drop strength and buckling strength as a container, and was evaluated as ◎. 0.45 ≦ X <0.7: It has a good thickness balance, and has mechanical properties such as drop strength and buckling strength as a container. 0.3 ≦ X <0.45: Has a minimum wall thickness balance that is practically necessary as a container. However, there is a case where a container having a large content may be restricted, and the evaluation is set to “△”. X <0.3, or a hole was formed in the molded article: practically difficult as a container.

[Smoothness of Inner Surface] A sample of 30 mm square was cut from the above middle part of the pulp molded article, and the thickness was measured at 25 points evenly at 5 mm intervals using a micrometer. From the measured values, an average value: t _ave , a maximum thickness: t _max , and a minimum thickness: t _min were obtained, and Y = ｛(t
_max− t _min ) / t _{ave 評 価} . Y <0.2: A molded article having extremely high smoothness and good appearance was evaluated as ◎. 0.2 ≦ Y <0.4: A molded article having a high smoothness and a good appearance was evaluated as “○”. 0.4 ≦ Y <0.6: Although the appearance is slightly inferior, it has mechanical properties such as drop strength and buckling strength as a container, and was evaluated as Δ. 0.6 ≦ Y: The appearance is poor, and at the same time, the mechanical properties are not sufficient and it is difficult to use as a container. In addition, when coating the surface with a resin component, a defect such as unevenness may be caused.

[0037]

[Table 1]

[0038]

According to the present invention, a molded article having a uniform thickness is provided even if the shape is a complicated design such as a curved surface.
Further, a method for producing a pulp molded article capable of stably producing a molded article having a uniform thickness is provided. In addition, when 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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Tokito Sono, Inventor 2606, Kabanecho, Haga-gun, Tochigi Kao Co., Ltd. 3E033 BA10 FA10 4L055 BF08 EA03 EA26 EA40 FA23 GA05

Claims (2)

[Claims] 1. A pulp mold formed by supplying a pulp slurry into a pair of split mold cavities in which a cavity having a predetermined shape is formed to form a pulp laminate, and then dewatering the pulp laminate. The method for producing a pulp molded article, wherein a pulp slurry supply concentration A of the pulp slurry and a pulp slurry supply flow rate B to be supplied are represented by the following formula (1). (Equation 1) 2. The pulp slurry supply concentration is 0.1%.
The method for producing a pulp molded article according to claim 1, wherein the amount is from 6 to 6 wt%.