JP2001039429A - Manufacture of pulp mold container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recyclable container which is formed of a small amount of raw materials and excellent in waterproof property and moisture-proof property by drying a pulp layer after dehydration in advance, forming a synthetic resin emulsion coating film on outer and inner surfaces of the pulp layer, and drying these coating films and pulp layers. SOLUTION: In manufacturing a container, a pulp slurry is poured into a cavity 13 formed by butting a set of split dies 11, 12 in a paper making die 10. The cavity 13 is evacuated to suck water in the pulp slurry, and pulp fibers are deposited on an inner surface of the cavity 13 to form a pulp layer 15. Then, an elastically deformable core 16 is inserted in the cavity 13, and a pressurized fluid is fed therein to inflate the core to give the shape of an inner surface of the cavity 13 to the pulp layer 15, and then, the pulp layer is preliminarily dried. Then, the synthetic resin emulsion is applied to the inside of the cavity 13 from which the core 16 is taken out, and a coating film is formed thereon, and dried by a heating die.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a pulp mold container.

[0002]

2. Description of the Related Art As a technique relating to a container in which a resin layer is formed on a pulp molded article, for example, the technique described in Japanese Patent Application Laid-Open No. 10-46500 is known. This publication discloses that after spraying an aqueous solution of a polymer compound on the inner surface of a pulp layer having a predetermined moisture content in a state before dehydration or after dehydration at room temperature, a drying process is performed by a heating press or the like to form a shallow bottom mold tray. A method of obtaining is disclosed.

[0003] However, in the method described in the above publication, the sprayed aqueous solution of the polymer compound penetrates into the pulp layer, so that a layer having a sufficient thickness to exhibit waterproofness and moistureproofness is formed. For this purpose, a large amount of an aqueous solution of a polymer compound is required, and the drying time becomes long, so that the production cost becomes high. In addition, since the aqueous solution of the polymer compound that has penetrated into the pulp layer acts as a binder for binding the pulp fibers, the disintegration of the pulp fibers is reduced, and the pulp fibers are not easily reused.

Accordingly, an object of the present invention is to provide a method of manufacturing a pulp mold container which can be provided with waterproof and moisture-proof properties with a smaller amount of raw materials than in the past and which is easy to reuse.

[0005]

According to the present invention, there is provided a pulp molded article having a resin layer having a thickness of 5 to 300 μm formed of a synthetic resin on an inner surface and / or an outer surface thereof. Ratio to the thickness (former / latter) is 1/2 to 1 /
The above object has been attained by providing a pulp mold container of 100.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pulp mold container according to the present invention will be described below based on a preferred embodiment with reference to the drawings. FIG. 1A is a perspective view of a pulp mold container (hereinafter, simply referred to as a container) according to an embodiment of the present invention, partially cut away. FIG.
FIG. 1B shows a longitudinal sectional view of FIG.

The container 1 of the present embodiment has an inner surface (accommodating surface) of a pulp molded product (hereinafter, also simply referred to as a molded product) 2.
It has a resin layer 3 as a whole, has an opening 4 at the top thereof, further has a trunk 5 and a bottom 6, and further has a concave portion 7 which is continuous over the entire circumference thereof. Are formed. This container 1 is used as a hollow container suitable for accommodating contents such as powders, granules, and liquids.

The outer surfaces of the front and rear walls constituting the body 5 are
Has a shape that forms a straight line over the height direction of the container 1 when viewed from the side (excluding the concave portion 7). Similarly, the outer surfaces on the left and right sides of the body 5 also have a shape that forms a straight line across the height direction of the container 1 when the container 1 is viewed from the front (similarly, the concave portion). 7 is excluded). Each wall rises so that the angle θ formed between the grounding surface 6 ′ of the bottom 6 and the outer surface of each wall of the body 5 is substantially 90 ° in both the front and rear walls and the left and right walls.

The resin layer 3 has a thickness of 5 to 300 μm,
Preferably it is 20 to 150 μm. 5μ thickness
When the thickness is less than m, sufficient storage stability of the contents is not obtained because a sufficient waterproof / moisture-proof effect cannot be obtained. When the thickness exceeds 300 μm, it takes time to dry the resin layer 3. Problems such as uneven thickness will occur. The thickness of the resin layer 3 is measured by observing a cross section of the container 1 with a microscope. The container 1 of the present embodiment is the same as the container disclosed in
Unlike the mold tray described in Japanese Patent Application Laid-Open No. 0-46500, the area of the pulp fiber constituting the molded body 2 and the resin layer 3
Are clearly distinguished from the synthetic resin region constituting
That is, in the mold tray described in the above publication, since the aqueous solution of the polymer compound penetrates into the inside of the pulp layer having a predetermined moisture content, the boundary between the pulp fiber region and the polymer compound region is not clear. In the container 1 of the embodiment, as is clear from the description of the manufacturing method described later, the boundary is clear because the penetration of the synthetic resin is small. as a result,
Waterproofing and moistureproofing can be imparted with a smaller amount of synthetic resin than before, and the pulp fiber disintegration during reuse is improved.

The relative relationship between the thickness of the resin layer 3 and the thickness of the molded body 2 is such that the ratio of the former / the latter is 1/2 to 1/100, preferably 1/5 to 1/50. The ratio of both is 1
If it is more than / 2, the disintegration at the time of reuse is inferior, and if it is less than 1/100, sufficient waterproof and moisture-proof properties cannot be obtained.
In addition, the thickness of the molded body 2 is appropriately adjusted within a range where the above ratio is 1/2 to 1/100, preferably 100 to 3000 μm, and more preferably 500 to
2000 μm.

The resin layer 3 is formed from various synthetic resins. As synthetic resins, acrylic, styrene-acrylic, ethylene-vinyl acetate, styrene-butadiene rubber, polyvinyl alcohol, vinylidene chloride,
Examples include wax-based, fluorine-based, and silicone-based resins, copolymers thereof, and combinations thereof.

The container 1 has a water vapor transmission rate (JIS) according to a cup method.
When Z 0208) is 100 g / (m ² · 24 hr) or less, particularly 60 g / (m ² · 24 hr) or less, it becomes difficult to absorb moisture in the atmosphere, and it is possible to maintain appropriate rigidity as a hollow container. It is preferable because the quality of the contents can be effectively prevented from being impaired by the absorption of moisture, that is, the storage stability of the contents can be improved. It is preferable that the lower limit of the moisture permeability is smaller since the waterproof / moisture-proof property is improved, but the lower limit that can be reached at present is 0.5 g / g.
(M ² · 24 hr).

Next, a preferred method for manufacturing the above-described container 1 will be described with reference to FIG. In FIG.
The papermaking process of the process of manufacturing the molded body 2 in the container 1 is sequentially shown. Specifically, (a) shows a papermaking process,
(B) is a core insertion step, (c) is a pressure / dehydration step,
(D) is a step of opening the papermaking mold and taking out the pulp layer.

First, as shown in FIG. 2 (a), a cavity 13 of a papermaking mold 10 in which a cavity 13 having a predetermined shape is formed by abutting a pair of split dies 11, 12.
The pulp slurry is poured into the inside. Each of the split dies 11 and 12 has a plurality of communication holes 1 for communicating the outside with the cavity 13.
4 are provided. In addition, each split mold 11, 12
Are respectively covered with a net (not shown) having a mesh of a predetermined size. In the present embodiment, the shape of the cavity 13 depends on the shape of the molding 2 to be molded.
It has a shape corresponding to the external shape of. However, the shape of the cavity 13 is not limited to this.

[0015] The pulp slurry is mainly made of pulp fibers. When another material is used in addition to the pulp fiber, the amount of the other material is preferably 1 to 70% by weight, particularly preferably 5 to 50% by weight based on the weight of the obtained molded body 2. Other materials include 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 polysaccharides.

Next, the inside of the cavity 13 is depressurized by sucking the split molds 11 and 12 from the outside, and the moisture in the pulp slurry is sucked and pulp fibers are deposited on the inner surface of the cavity 13. As a result, on the inner surface of the cavity 13,
A pulp layer 15 on which pulp fibers are deposited is formed.

A predetermined amount of pulp slurry is supplied to the cavity 13.
When the pulp slurry is injected into the inside, the injection of the pulp slurry is stopped, and the inside of the cavity 13 is completely sucked and dehydrated. Continuing with FIG.
As shown in (b), the inside of the cavity 13 is suctioned and decompressed, and a hollow core 16 which is elastic, expands and contracts, and is hollow is inserted into the cavity 13. Core 16
The pulp layer 15 is inflated like a balloon in the cavity 13 to press the pulp layer 15 against the inner surface of the cavity 13 to give the inner surface shape of the cavity 13 and pressurize / pull the pulp layer 15.
Used to dehydrate. The core 16 is formed of urethane, fluorine-based rubber, silicone-based rubber, elastomer, or the like, which is excellent in tensile strength, rebound resilience, elasticity, and the like. The core 16 may be a hollow bag.

Next, as shown in FIG.
The core 16 is expanded by supplying a predetermined pressurized fluid therein, and the pulp layer 15 is pressed against the inner surface of the cavity 13 by the expanded core 16. As a result, the pulp layer 15 is pressed against the inner surface of the cavity 13 by the expanded core 16, and the inner surface shape of the cavity 13 is transferred to the pulp layer 15, and pressurization and dehydration proceed. 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 for supplying the pressurized fluid is 0.01 to 5
It is preferable that it is MPa, especially 0.1-3 MPa.

Since the pulp layer 15 is pressed against the inner surface of the cavity 13 from the inside, the density of the pulp layer 15 increases (that is, the porosity decreases). Can be suppressed to a low amount permeating into the pulp layer 15. The porosity of the molded body 2 obtained by the present production method is preferably 30 to 70%, more preferably 40 to 60%. The porosity is calculated from the following equation (1). In addition, the following formula (1)
The density of the molded body is calculated from the weight and thickness of a part of the molded body, and the density of the material constituting the molded body is calculated from the content ratio and the density of pulp fiber and other components.

[0020]

(Equation 1)

Further, the inner surface and the outer surface of the pulp layer 15 are smoothed by the pressing. As a result, the center line average roughness (Ra, a value measured in accordance with JIS B 0601) of the outer surface or inner surface of the molded body 2 obtained by the present production method is preferably 0.1 to 50 μm. ,
More preferably, it is 0.5 to 20 μm, and the maximum height (Rma
x, a value measured in accordance with JIS B 0601) is preferably 1 to 500 μm, more preferably 5 to 100 μm.
μm. Thereby, it is possible to apply the synthetic resin emulsion without excessively penetrating the pulp layer 15. Further, printing on the outer surface of the molded body 2 can be easily and neatly performed. Further, the appearance impression of the container 1 is further improved. Surfcom 120 for measuring surface roughness
A [manufactured by Tokyo Seimitsu Co., Ltd.] was used, and the measurement conditions were cutoff: 0.8 mm, measurement length: 10 mm, and filter: 2
CR, measurement magnification: 500, inclination correction: linear, polarity: standard.

If the porosity of the pulp layer 15 and the molded body 2 is too low due to the above pressing, the permeability of the emulsion may be too low, and conversely, the adhesion to the resin layer 3 may be low. Therefore, in consideration of the permeability of the emulsion, the water absorption (JIS P 8140) of the molded article 2 is 5 to 600 g / (m ² · 2 minutes), particularly 10 to 200 g /
It is preferable to mold the molded body 2 so that (m ² · 2 minutes).

By the above pressing, the shape of the inner surface of the cavity 13 is accurately transferred to the pulp layer 15 even if the shape of the inner surface of the cavity 13 is complicated. In addition, unlike the conventional manufacturing method, there is no need to use a bonding step, and thus the obtained molded body 2 has no joints and thick portions due to bonding. As a result, the strength of the obtained molded body 2 is increased and the appearance impression is improved.

When the shape of the inner surface of the cavity 13 is sufficiently transferred to the pulp layer 15 and the pulp layer 15 can be dewatered under pressure to a predetermined moisture content, the core 1 is removed as shown in FIG.
6. Drain the pressurized fluid in 6. This causes the core 16 to shrink and return to its original size. Next, the contracted core 16 is taken out of the cavity 13, and the papermaking mold 10 is further opened to take out the wet pulp layer 15 having a predetermined moisture content.
At this time, the moisture content of the pulp layer 15 is preferably set to about 50 to 80% by weight in consideration of handleability and the like.

The removed pulp layer 15 is then subjected to predrying, emulsion coating and drying steps. In these steps, the same apparatus as that in the paper making step shown in FIG. 2 is used, and almost the same operation is performed, except that paper making and dewatering are not performed. That is, first, a heating mold in which a cavity having a shape corresponding to the outer shape of the molded body 2 to be molded is formed by abutting a pair of split molds is heated to a predetermined temperature, and the heating mold is wetted in the heating mold. Of the above pulp layer.

Next, a core similar to the core 16 used in the paper making step was inserted into the pulp layer, and a pressurized fluid was supplied into the core to expand the core, thereby expanding the core. The pulp layer is pressed against the inner surface of the cavity by the core and preliminarily dried. The material of the core and the supply pressure of the pressurized fluid can be the same as in the above-described papermaking process. The pressing of the core further increases the density of the pulp layer (ie, further lowers the porosity).

The pulp layer has a predetermined water content (0.1 to 2).
(5% by weight), the pressurized fluid in the core is drained, and the core is shrunk and taken out. Next, a synthetic resin emulsion is sprayed into the pulp layer by a predetermined spraying means, and the emulsion is applied to the inner surface of the pulp layer to form a coating film. In this case, since the density of the pulp layer is high and the porosity is low as described above, the emulsion is hardly permeated into the pulp layer. Therefore, most of the emulsion remains on the surface of the pulp layer, and sufficient waterproof and moisture-proof properties can be exhibited by applying a smaller amount of emulsion than before. In addition, it is possible to prevent the disintegration of the pulp fiber during the reuse. It is preferable to use a synthetic resin having a particle size of about 0.01 to 10 μm as the emulsion from the viewpoint of controlling the penetration of the emulsion into the pulp layer.

Under the above conditions, the coating film of the emulsion and the pulp layer are dried in a heating mold to form a resin layer from the coating film and to form a molded body 2 from the pulp layer. When both are sufficiently dried, the heating mold is opened, and the container 1 having the resin layer 3 on the inner surface of the molded body 2 is taken out.

The present invention is not limited to the embodiments described above,
For example, the resin layer may be formed only on the outer surface of the molded body 2 or on the inner and outer surfaces of the molded body 2. In addition, a reinforcing member made of plastic or the like may be provided at a portion where a load is applied when the container 1 is used, for example, at the opening 4 or the bottom 6 to improve the durability of the container 1. Further, some of these parts may be formed of plastic or the like. In addition, the container of the present invention may be a bottle-shaped container in which the opening area of the opening is smaller than the cross-sectional area of the body.

[0030]

According to the present invention, there is provided a method for producing a waterproof / moisture-proof pulp mold container capable of imparting waterproof / moisture-proof properties with a smaller amount of raw materials than before. Further, according to the present invention, there is provided a method for producing a pulp mold container having high waterproofing and moisture-proof properties in which pulp fibers have a high defibration property and are easy to reuse.

[Brief description of the drawings]

FIG. 1 (a) is a partially cutaway perspective view showing one embodiment of a waterproof / moistureproof pulp mold container of the present invention, and FIG. 1 (b) is FIG. 1 (a). II at
It is a line sectional view.

FIG. 2 is a schematic view sequentially showing a paper making step of a step of manufacturing a molded body 2 in a container 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water-proof and moisture-proof pulp mold container 2 Pulp molded product 3 Resin layer 4 Opening 5 Body 6 Bottom

Claims (3)

[Claims] The pulp layer after dehydration is pre-dried, a coating film of a synthetic resin emulsion is formed on the inner surface and / or outer surface of the pre-dried pulp layer, and the coating film and the pulp layer are dried. For producing a pulp mold container. 2. The method for producing a pulp mold container according to claim 1, wherein the pulp layer dehydrated to a water content of 50 to 80% by weight is preliminarily dried. 3. The above-mentioned pulp layer is formed on the inner surface of a cavity of a mold, and then a hollow core, which is elastic, expands and contracts and has a hollow shape, is inserted into the cavity. The method for producing a pulp mold container according to claim 1 or 2, wherein the core is expanded by supplying water, and the pulp layer is pressed against the inner surface of the cavity by the core to dehydrate and predry.