JP2024038851A - Pulp molded products and embossed pulp molded products - Google Patents

Abstract

The present invention provides a technique that is advantageous for manufacturing a pulp molded product having a concave-convex pattern on its surface. The pulp molded product MP2 has a puncture strength in the range of 40 to 85 N. [Selected Figure]

Description

The present invention relates to a pulp molded product and an embossed pulp molded product.

In recent years, environmental problems related to an increase in waste have been occurring frequently. In view of this, paper containers are being used instead of plastic containers and metal containers for storing toiletry products, drinks, food, and the like. For example, as liquid paper containers such as milk containers, there is a so-called gable-top paper container, which is made of paperboard coated with polyethylene resin on both sides of the paper and has a gable roof shape at the top. Such paper containers not only contribute to resource and energy conservation, but also contribute to environmental conservation by being easy to recycle or incinerate when disposed of. Therefore, paper containers have become popular in various fields.

However, since the above paper containers are formed by folding and pasting paperboard, the manufacturing process is complicated and the manufacturing cost increases. In addition, paper containers such as those described above have a low degree of freedom in shape, and therefore have problems such as not being able to fully demonstrate the appeal of the product based on the shape of the container.

One of the means for increasing the degree of freedom in the shape of paper containers is a pulp mold, which manufactures a molded article from a slurry containing pulp and water. In a pulp mold, typically pulp in a slurry is deposited onto a paper mold to form a pulp layer, the pulp layer is dehydrated, and then it is dried in an oven. Molded products obtained by this technology, that is, pulp molded products, have excellent physical properties such as heat resistance, cold resistance, and moisture absorption and desorption properties, which are characteristics of paper packaging materials, and are suitable for paper trays for food. It has come to be widely used as a fixed cushioning material for containers, fruits, etc. (Patent Document 1).

JP2008-285188A

An object of the present invention is to provide an advantageous technique for manufacturing a pulp molded product having a pattern of protrusions and recesses on the surface.

According to one aspect of the present invention, a pulp molded product having a puncture strength within a range of 40 to 85N is provided.
According to another aspect of the present invention, there is provided a pulp molded article according to the above aspect, which has a density within the range of 0.5 to 1.1 g/cm ³ .

According to still another aspect of the present invention, there is provided a pulp molded article according to any of the above aspects, in which the wall thickness is within a range of 0.6 to 1.2 mm.
According to still another aspect of the present invention, there is provided a pulp molded product according to any of the above aspects, in which the average fiber length of the pulp is within the range of 0.7 to 2.0 mm.

According to still another aspect of the present invention, there is provided a pulp molded product according to any of the above aspects, which contains a paper strength enhancer.
According to still another aspect of the present invention, there is provided a pulp molded article according to any of the above aspects, which contains a sizing agent.

According to yet another aspect of the present invention, there is provided an embossed pulp molded article having a puncture strength in the range of 40 to 85 N and whose wall portion includes an embossed portion.
According to still another aspect of the present invention, there is provided a method for manufacturing an embossed pulp molded product, which includes embossing a wall portion of the pulp molded product according to any of the above aspects.

According to the present invention, it is possible to provide an advantageous technique for manufacturing a pulp molded product having a concavo-convex pattern on the surface.

FIG. 1 is a perspective view showing a pulp molded product according to an embodiment of the present invention. FIG. 1 is a perspective view showing an embossed portion of an embossed pulp molded product according to an embodiment of the present invention. 2 is a diagram schematically showing an example of a manufacturing apparatus that can be used to manufacture the pulp molded product of FIG. 1. FIG. 4 is a diagram showing a pulp layer forming process in pulp molding using the apparatus of FIG. 3. FIG. FIG. 2 is a cross-sectional view schematically showing an example of a pulp layer formed on a paper mold. FIG. 4 is a diagram showing a dehydration process in pulp molding using the apparatus of FIG. 3. FIG. 4 is a diagram showing a pulp layer conveyance process in pulp molding using the apparatus of FIG. 3; 4 is a diagram showing a hot press forming process in pulp molding using the apparatus of FIG. 3. FIG. FIG. 1 is a cross-sectional view schematically showing an example of a pulp molded product obtained by a hot press process. FIG. 4 is a diagram showing a conveyance process of a pulp molded product in pulp molding using the apparatus of FIG. 3; FIG. 11 is a diagram showing a state in which the conveyance process of FIG. 10 has been completed.

The circumstances in which the present inventor tackled the above problem will be explained below.
The embossed pulp molded article of the present invention is manufactured by forming an uneven pattern on the surface of the pulp molded article by embossing. A structure similar to the embossed pulp molded article of the present invention can also be manufactured, for example, by the following method. That is, embossing is omitted, and instead, an uneven pattern corresponding to the uneven pattern to be formed on the surface of the pulp molded product by embossing is provided on a mold for manufacturing the pulp molded product. Thereby, it is possible to manufacture a pulp molded product having an uneven pattern on the surface.

This method also makes it possible to produce structures similar to embossed pulp molded articles. However, with this method, for example, when changing the information displayed by the uneven pattern, it is also necessary to change the mold for manufacturing the pulp molded product. Since molds for producing pulp molded products are expensive, this method is expensive, for example, when changing the information displayed by the uneven pattern.

On the other hand, with the method of forming a concave-convex pattern on the surface of a pulp molded product by embossing, if you want to change the information displayed by the concave and convex pattern, you only need to change the plate used for embossing, and the pulp molded product can be manufactured. There is no need to change the mold for this. Embossed plates are less expensive than molds for producing pulp molded products. Therefore, this method is low cost even when changing the displayed information by using a concavo-convex pattern, for example.

In this way, the above method using embossing is advantageous in terms of cost. However, the present inventor discovered that in the above method using embossing, the embossing process causes tears in the wall of the pulp molded article, or even if the embossing process is performed, an uneven pattern that is clearly visible to the naked eye is formed. We have newly discovered that there is a possibility that it may not be possible to form on the walls of pulp molded products. The present inventor has worked to solve this new problem and has completed the present invention.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are more specific implementations of any of the above aspects. The matters described below can be incorporated into each of the above aspects alone or in combination.

In addition, the embodiments shown below illustrate configurations for embodying the technical idea of the present invention, and the technical idea of the present invention includes the materials, shapes, structures, etc. of the following constituent members. It is not limited by. Various changes can be made to the technical idea of the present invention within the technical scope defined by the claims.

Note that elements having the same or similar functions are designated by the same reference numerals in the drawings referred to below, and redundant explanation will be omitted. In addition, the drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, and the relationship between the dimensions of a certain member and the dimensions of other members, etc. may differ from the actual one. It can be different.

<1> Pulp molded product In this specification, a product before embossing is referred to as a “pulp molded product”, and a product after embossing is referred to as an “embossed pulp molded product”.

FIG. 1 is a perspective view showing a pulp molded product according to an embodiment of the present invention.
The pulp molded product MP2 shown in FIG. 1 is a container. This pulp molded product MP2 includes a bottom part and a side wall part, and is open at the top.

The bottom has a disc shape. The bottom may have a shape other than a circle when orthogonally projected onto a plane perpendicular to the depth direction of the container, for example, a polygonal shape such as a square shape.

The side wall portion has a cylindrical shape extending upward from the edge of the bottom portion. The diameter of the side wall increases from the bottom toward the opening. The inner and outer surfaces of the sidewalls may be perpendicular to the top surface of the bottom. However, the pulp molded product MP2, in which the side wall portion increases in diameter from the bottom toward the opening, is advantageous in achieving high mold releasability and is easy to stack.

The pulp molded article MP2 may have various shapes such as a cup shape, a bowl shape, a tray shape, and a box shape. The pulp molded product MP2 does not need to be a container as long as it is a three-dimensional molded product, that is, a molded product that has a three-dimensional shape rather than a two-dimensional shape like a sheet.

The pulp molded product MP2 has a puncture strength in the range of 40 to 85N. The pulp molded article MP2 preferably has a puncture strength in the range of 45 to 85N, more preferably in the range of 50 to 80N. If the puncture strength of the pulp molded product MP2 is too low, the pulp molded product MP2 is likely to break when subjected to a process such as embossing to form an uneven pattern. When the pulp molded product MP2 has a high puncture strength, it tends to become difficult to tear when subjected to a process such as embossing to form an uneven pattern. However, if the puncture strength of the pulp molded product MP2 is too high, it will be difficult to form an uneven pattern that is clearly visible to the naked eye.

Here, the puncture strength of the pulp molded article MP2 is a value obtained by the method specified in JIS Z1707:2019 "General Rules for Plastic Films for Food Packaging."

The thickness of the pulp molded product MP2 is preferably in the range of 0.6 to 1.2 mm. That is, it is preferable that the thickness of the wall portion of the pulp molded product MP2, in this case, the thickness of the bottom portion and the side wall portion, be within the range of 0.6 to 1.2 mm. The thickness of the pulp molded article MP2 is more preferably within the range of 0.7 to 1.2 mm, and even more preferably within the range of 0.7 to 1.1 mm. As the pulp molded product MP2 becomes thicker, the puncture strength tends to increase. Furthermore, when the pulp molded article MP2 is made thicker, its bending rigidity tends to increase. The thick pulp molded articles MP2 are bulky, especially when stacked. When the wall portion of the pulp molded product MP2 is made thinner, it tends to become easier to form an uneven pattern that is clearly visible to the naked eye. Furthermore, making the wall portion of the pulp molded article MP2 thinner is advantageous in that drying during its manufacture can be completed in a short time.

Here, the thickness of the pulp molded article MP2 is a value obtained by the following method. That is, five test pieces are cut out from arbitrary positions of the pulp molded article MP2. The thickness of each test piece is then measured. For example, a thickness gauge manufactured by Mitutoyo is used to measure the thickness. The thickness of the pulp molded product MP2 is the average value of the measurement results obtained for five test pieces.

In the pulp molded article MP2, the average fiber length of the pulp is preferably within the range of 0.7 to 2.0 mm. This average fiber length is more preferably within the range of 0.8 to 2.0 mm, and even more preferably within the range of 0.8 to 1.9 mm. As the average fiber length decreases, the puncture strength tends to increase. When the average fiber length is increased, drying during production can be completed in a shorter time. However, if the average fiber length is excessively increased, the strength (that is, resistance to deformation and destruction) of the pulp molded article MP2 decreases.

Here, the average fiber length of pulp is a value obtained by the following method. That is, first, a 5 g test piece is obtained from the pulp molded article MP2. Next, this test piece is cut into small pieces, water is added so that the total mass becomes 500 g, and the pieces are soaked overnight. This is then stirred with a stirrer to disintegrate the pulp from each other. In this way, a dispersion containing pulp is obtained. Next, an appropriate amount is taken from this dispersion and further diluted with water to prepare an aqueous dispersion having a pulp solid content of 0.05% by mass. Using the sample thus obtained, the fiber length is measured according to JIS P8226-2:2011 "Pulp - Fiber length measurement method by optical automatic analysis - Part 2: Non-polarization method". The average fiber length of pulp refers to the length weighted average fiber length _LL .

The pulp suspension obtained by dispersing the pulp contained in the pulp molded product MP2 in water preferably has a Canadian Standard Freeness (CSF) of 500 mL or more, more preferably 530 mL or more. When this Canadian standard freeness is low, it tends to take a long time for drying during production of the pulp molded article MP2.

The above Canadian standard freeness is preferably 700 mL or less, more preferably 680 mL or less. When this Canadian standard freeness is high, the strength of the pulp molded product MP2 tends to be low.

Here, the above Canadian standard freeness is a value obtained by the following method. First, a test piece is obtained from the pulp molded product MP2, and a dispersion containing pulp is obtained by the same method as above. Next, this dispersion liquid is diluted with water so that the solid content concentration is 0.3% by mass to obtain an aqueous suspension of pulp. Next, using 1 L of this suspension, the measurement specified in JIS P8121-2:2012 "Pulp - Freeness Test Method - Part 2: Canadian Standard Freeness Method" is performed. For this measurement, for example, a Canadian Free Tester manufactured by Kumagai Riki Kogyo Co., Ltd. is used. Moreover, the measured value is corrected by referring to the correction table for the temperature of the suspension measured in advance. In this way, the Canadian Standard Freeness is obtained.

It is preferable that the pulp molded product MP2 has a density within the range of 0.5 to 1.1 g/cm ³ . The density of the pulp molded article MP2 is more preferably within the range of 0.6 to 1.1 g/cm ³ , even more preferably within the range of 0.6 to 1.0 g/cm ³ . A high density means that the denseness of the pulp mold is improved, and when the density is increased, the puncture strength tends to be increased.

Here, the above density is a value obtained by the following method. That is, a square or rectangular test piece is cut out from a portion of the pulp molded article MP2 whose surface is not curved, and its dimensions, mass, and thickness are measured. Calculate the density from the obtained value.

It is preferable that the pulp molded article MP2 further contains a paper strength enhancer. By using a paper strength enhancer, the puncture strength of the pulp molded product MP2 can be increased. Note that among paper strength enhancers, polyacrylamide is particularly convenient in producing the pulp molded product MP2. As the polyacrylamide as the paper strength enhancer, those sold by Arakawa Chemical Industry Co., Ltd., Seiko PMC Co., Ltd., or Harima Kasei Group Co., Ltd. can be used. Alternatively, starch may be used as a paper strength agent.

The pulp molded product MP2 produced using a paper strength enhancer has a higher nitrogen content than the pulp molded product MP2 produced without using a paper strength enhancer. The nitrogen content of the pulp molded product MP2 produced using the paper strength agent is 300 μg/g or more according to one example, and 500 μg/g or more according to another example. There is no upper limit to the nitrogen content of the pulp molded product MP2, but according to one example, it is 1000 μg/g or less.

The nitrogen content of the pulp molded article MP2 is obtained by the following method. First, two test pieces are taken from arbitrary positions on the pulp molded article MP2. The mass of each test piece is 10 mg. Next, each test piece is measured by the chemiluminescence method specified in JIS K2609:1998 "Crude oil and petroleum products - Nitrogen analysis test method". For this measurement, for example, TN-2100H manufactured by Nitto Seiko Airalytech Co., Ltd. can be used. The nitrogen content is the average value of the measurement results obtained for two test pieces. Note that the pulp molded product MP2 described above can achieve high puncture strength even if the paper strength enhancer is omitted.

It is preferable that the pulp molded article MP2 further contains a sizing agent. Use of the sizing agent can increase the puncture strength of the pulp molded product MP2. The sizing agent is, for example, an alkyl ketene dimer (AKD)-based sizing agent. Note that the pulp molded product MP2 described above can achieve high puncture strength even if the sizing agent is omitted.

<2> Embossed pulp molded product By embossing the wall of the pulp molded product MP2 described above, an embossed pulp molded product can be manufactured. In this way, with the method of forming a concave-convex pattern on the surface of a pulp molded product by embossing, when changing the information displayed by the concave and convex pattern, it is only necessary to change the plate used for embossing. There is no need to change the mold for manufacturing. Embossed plates are less expensive than molds for producing pulp molded products. Therefore, this method is low cost even when changing the displayed information by using a concavo-convex pattern, for example.

According to the above method, an embossed pulp molded article having a puncture strength in the range of 40 to 85 N and whose wall portion includes an embossed portion is provided. FIG. 2 is a perspective view showing an embossed portion of an embossed pulp molded product according to an embodiment of the present invention. In the embossed portion shown in FIG. 2, the characters are recessed. On the other hand, the embossed portion may be formed so that the characters or patterns are raised in a convex shape.

As described above, the pulp molded product MP2 has a puncture strength in the range of 40 to 85N. When such a pulp molded product is embossed, it is possible to form a concavo-convex pattern with excellent visibility without causing tears in the embossed part.

The pulp molded article MP2 can also exhibit effects different from the above-mentioned effects obtained when embossing is performed. That is, since the pulp molded article MP2 has sufficiently high puncture strength, it is unlikely to be punctured or torn even when the tip of a cutlery such as a fork is strongly pressed against it. In addition, because this pulp molded product has sufficiently high puncture strength, end users can use the walls of their own pulp molded products to distinguish it from pulp molded products used by others. When a mark is made by pressing a nail against the wall, the wall portion is unlikely to be torn, and a mark that is clearly visible to the naked eye can be provided. In this way, the pulp molded article does not need to be embossed.

<3> Manufacturing device for pulp molded product Next, a manufacturing device that can be used to manufacture the pulp molded product MP2 will be described. FIG. 3 is a diagram schematically showing an example of a manufacturing apparatus that can be used to manufacture the pulp molded product of FIG. 1.

The manufacturing apparatus 1 shown in FIG. 3 includes a support 10, a first station 20, a second station 30, and a third station 40.

The support body 10 includes a frame body and a rail installed on the top of the frame body.

The first station 20 includes a container 210, a lifting device 220, a cover body 230, a paper mold 240, a moving device 250, a lifting device 260, and an upper mold 270.

The container 210 is installed within the frame of the support 10. The container 210 is open at the top. The container 210 contains a slurry S that contains pulp and water.

The lifting device 220 is attached to the frame of the support 10 above the container 210. The lifting device 220 includes, for example, a hydraulic cylinder. The lifting device 220 supports the cover body 230. The lifting device 220 can raise and lower the cover body 230 at the opening of the container 210.

The cover body 230 is a hollow body having an opening at the top. A pump (not shown) is connected to the cover body 230.

The paper mold 240 is fixed to the opening of the cover body 230. Specifically, the paper die 240 is fixed to the opening of the cover body 230 so that a space adjacent to one surface thereof is surrounded by the paper die 240 and the cover body 230.

The paper mold 240 is a mold that is liquid permeable. The paper mold 240 has a three-dimensional shape. That is, the paper mold 240 has one or more convex portions and/or one or more concave portions on the surface on which pulp is deposited. Specifically, the outer surface of the paper mold 240, that is, the back surface of the surface adjacent to the space, has a shape corresponding to a pulp molded product. Here, the paper mold 240 is a male mold with a protruding upper surface.

The paper mold 240 includes, for example, a paper mold main body having a large number of through holes and an outer surface having a shape corresponding to a pulp molded product, and a paper mold main body provided on the outer surface of the paper mold main body along this outer surface. It includes a mesh body.

The moving device 250 is movable between the first station 20 and the second station 30 along the rails of the support 10 . The moving device 250 includes, for example, a motor as a power source. A lifting device 260 is attached to the moving device 250 and can be moved between the first station 20 and the second station 30.

The lifting device 260 is attached to the moving device 250 as described above. The lifting device 260 includes, for example, a hydraulic cylinder. The lifting device 260 supports an upper mold 270. The lifting device 260 can raise and lower the upper die 270.

The upper die 270 is a holder that holds a pulp layer, which will be described later, between it and the papermaking die 240 and holds the pulp layer by vacuum suction. The lower surface of the upper mold 270 has a shape corresponding to the outer surface of the paper mold 240. Here, the upper mold 270 is a female mold with a concave lower surface. The upper mold 270 has, for example, a large number of through holes with one end open on the lower surface and the other end connected to a pump.

The second station 30 is provided near the first station 20. The second station 30 includes a table 310, a lower mold 320, a moving device 330, a press device 340, and an upper mold 350.

The stand 310 is installed within the frame of the support body 10. A lower mold 320 is installed on the stand 310.

The lower mold 320 is a mold that is permeable to gas and/or liquid. The lower mold 320 has an upper surface that corresponds to the outer surface of the paper mold 240. Here, the lower mold 320 is a male mold with a protruding upper surface. The lower die 320 has, for example, a large number of through holes, and has a smooth surface having a shape corresponding to the outer surface of the papermaking die 240.

The moving device 330 is movable along the rails of the support body 10 between the second station 30 and a fourth station (not shown). The moving device 330 includes, for example, a motor as a power source. When the moving device 330 is located at the second station 30, movement in the up-down, left-right, and front-back directions can be restricted by the lock mechanism. Further, a press device 340 is attached to the moving device 330, and can be transferred between the second station 30 and the fourth station.

The press device 340 is attached to the moving device 330 as described above. Press device 340 includes, for example, a hydraulic cylinder. The press device 340 supports an upper die 350. The press device 340 can raise and lower the upper die 350.

The upper mold 350 is a mold that does not have gas permeability or liquid permeability. The lower surface of the upper mold 350 has a shape corresponding to the outer surface of the paper mold 240. Here, the upper mold 350 is a female mold with a concave lower surface. The upper die 350 has a smooth surface that has a shape corresponding to the outer surface of the papermaking die 240.

The second station 30 further includes a heater and a pump (neither shown). The heater heats the lower mold 320 and the upper mold 350 from both sides. The pump is connected to the lower space of the lower mold 320.

The third station 40 is provided near the second station 30. The third station 40 includes a table 410, a moving device 420, a lifting device 430, and a holder 440.

The stand 410 is installed within the frame of the support body 10. A pulp molded product is placed on the stand 410.

The moving device 420 is movable between the second station 30 and the third station 40 along the rails of the support 10 . The moving device 420 includes, for example, a motor as a power source. A lifting device 430 is attached to the moving device 420 and can be moved between the second station 30 and the third station 40.

The lifting device 430 is attached to the moving device 420 as described above. The lifting device 430 includes, for example, a hydraulic cylinder. The lifting device 430 supports a holder 440. The lifting device 430 can raise and lower the holder 440.

The holder 440 is a holder that holds a pulp molded product, which will be described later, by vacuum suction. The lower surface of the holder 440 has a shape corresponding to the outer surface of the paper mold 240. Here, the holder 440 has a concave lower surface. The holder 440 has, for example, a number of through holes with one end open at the bottom surface and the other end connected to a pump.

<4> Method for manufacturing a pulp molded product In a manufacturing method according to an embodiment of the present invention, a pulp molded product MP2 is manufactured using, for example, the manufacturing apparatus 1 described above. This will be explained with reference to FIGS. 3 to 11.

FIG. 4 is a diagram showing a pulp layer forming process in pulp molding using the apparatus shown in FIG. 3. FIG. 5 is a cross-sectional view schematically showing an example of a pulp layer formed on a paper mold. FIG. 6 is a diagram showing a dewatering process in pulp molding using the apparatus shown in FIG. 3. FIG. 7 is a diagram showing a process of conveying a pulp layer in pulp molding using the apparatus shown in FIG. 3. FIG. 8 is a diagram showing a hot press forming process in pulp molding using the apparatus shown in FIG. 3. FIG. 9 is a cross-sectional view schematically showing an example of a pulp molded product obtained by a hot press process. FIG. 10 is a diagram showing a conveyance process of a pulp molded product in pulp molding using the apparatus shown in FIG. 3. FIG. 11 is a diagram showing a state in which the conveyance process of FIG. 10 has been completed.

In this method, first, slurry S is prepared.
Slurry S contains pulp and water. It is preferable that the slurry S further contains a paper strength enhancer. Moreover, it is preferable that the slurry S further contains a sizing agent. Here, as an example, it is assumed that the slurry S is a suspension having high viscosity, in which pulp is dispersed in a solution containing water, a paper strength agent, and a sizing agent.

The average fiber length of the pulp contained in the slurry S is preferably within the range described above for the pulp contained in the pulp molded product MP2. Preferably, the pulp contained in the slurry S further has one or more of the other characteristics described above for the pulp contained in the pulp molded product MP2. More preferably, the pulp contained in slurry S has substantially the same characteristics as described above for the pulp contained in pulp molded article MP2.

There are no particular restrictions on the type of pulp used for slurry S. Examples of the pulp include wood pulp, non-wood pulp, and waste paper, with wood pulp and non-wood pulp being preferred. It is preferable to use non-wood pulp from the viewpoint of environmental considerations such as forest conservation and utilization of unused resources.

Pulp can be classified according to its method of preparation. For example, in the case of wood pulp, chemical pulps such as kraft pulp (KP), sulfite pulp (SP), and soda pulp (AP); semi-chemical pulps such as semi-chemical pulp (SCP) and chemical ground wood pulp (CGP); ; Examples include groundwood pulp (GP) and thermomechanical pulp (TMP). Among these, it is preferable to use chemical pulp.

Wood pulp can be classified by raw material. Wood pulps include softwood pulps and hardwood pulps. Examples of softwood pulp include pulps obtained from Abies, Pinus, and the like. Further, examples of the hardwood pulp include pulps obtained from the genus Acacia, genus Eucalyptus, genus Beech, genus Asus (for example, poplar), and the like.

Non-wood pulp is obtained from fibers harvested from plant skins, stems, leaves, and leaf sheaths. Specifically, pulps obtained from cotton linters, cotton, linen, hemp, ramie, straw, esparto, manila hemp, zyzal hemp, jute, flax, kenaf, bamboo, sugar cane, ganpi, mitsumata, kozo, and mulberry are used. Can be mentioned. Among these, bamboo and sugarcane pulps are preferred.

These pulps can be used alone or in combination of two or more in any ratio.

Pulp has different fiber lengths depending on its raw material and manufacturing method. For example, pulp made from sugarcane generally has a shorter average fiber length than pulp made from bamboo. Further, the average fiber length of the pulp can be adjusted by any method, for example, by mechanical treatment such as beating or crushing.

Therefore, a pulp having certain characteristics can be obtained, for example, by selecting an appropriate pulp from a plurality of types of pulp, or by appropriately combining two or more types of pulp.

The pulp content of the slurry S is preferably in the range of 0.01 to 3.0% by mass, more preferably in the range of 0.01 to 0.5% by mass. It is desirable that the pulp content of the slurry S immediately before starting pulp molding is within the above range. When the pulp content is low, it is difficult to achieve high productivity. A high pulp content can lead to high variations in the thickness of the pulp layer.

The paper strength agent included in the slurry S is, for example, a nitrogen-containing compound. Preferably, the paper strength agent is polyacrylamide.

The proportion of the paper strength enhancer in the solid content of slurry S is preferably in the range of 0.3 to 3.0% by mass, more preferably in the range of 0.5 to 2.0% by mass, More preferably, it is within the range of 0.7 to 2.0% by mass.

The sizing agent contained in the slurry S is, for example, an alkyl ketene dimer (AKD)-based sizing agent.

The proportion of the sizing agent in the solid content of the slurry S is preferably in the range of 0.1 to 1.0% by mass, more preferably in the range of 0.2 to 0.5% by mass.

Slurry S can further contain additives other than the paper strength agent and the sizing agent. As additives, organic low-molecular materials, organic polymer materials, inorganic materials, or combinations thereof can be used, such as agents that impart water resistance or oil resistance. It is sufficient to select a drug according to the required performance of the container. The ratio of the total of the paper strength enhancer, sizing agent, and additive to the total of the pulp, paper strength enhancer, sizing agent, and additive is preferably 10% by mass or less, and 5% by mass or less. It is more preferable that there be. That is, the proportion of pulp in the total solid content contained in the slurry S is preferably 90% by mass or more, more preferably 95% by mass or more.

Next, the slurry S is supplied into the container 210. Next, as shown in FIG. 4, the cover body 230 is lowered by the lifting device 220, so that the upper surface of the paper mold 240 is positioned sufficiently below the liquid level of the slurry S. In this state, the pump is driven to reduce the pressure in the space surrounded by the cover body 230 and the paper mold 240. This causes the slurry S to flow across the paper mold 240 and deposit pulp on the paper mold 240. In the manner described above, the pulp layer MP1 is formed on the paper mold 240, as shown in FIG.

Next, while the pump is being driven, the cover body 230 is raised by the lifting device 220, as shown in FIG. 6, so that the lower part of the paper mold 240 is positioned sufficiently above the liquid level of the slurry S. Thereby, the pulp layer MP1 is dehydrated under reduced pressure. Next, the lifting device 260 is driven to lower the upper die 270 until its lower surface contacts the pulp layer MP1. Note that the pulp layer MP1 is not depicted in FIG. 6. This dehydration process is performed without heating either the upper die 270 or the papermaking die 240.

The depressurization time in the dehydration step is preferably in the range of 1 to 60 seconds, more preferably in the range of 1 to 10 seconds.

The moisture content of the pulp layer MP1 immediately after dehydration is preferably in the range of 40 to 90% by mass, more preferably in the range of 50 to 70% by mass, and more preferably in the range of 50 to 65% by mass. It is even more preferable that there be. If the water content is low, the movement of fibers in the in-plane direction within the pulp layer may become insufficient during the hot pressing process. If the moisture content is high, fibers will move excessively in the in-plane direction within the pulp layer during the hot pressing process, or during the period from the end of the dehydration process to the start of the hot pressing process. In this case, the shape retention of the pulp layer MP1 may become insufficient.

After stopping the pressure reduction in the space and the pressure increase, the pump is driven to cause the upper mold 270 to adsorb and hold the pulp layer MP1. Note that the suction by the pump and the upper mold 270 does not cause further dehydration of the pulp layer MP1.

Next, with the pulp layer MP1 adsorbed and held on the upper mold 270, the lifting device 260 is driven to raise the upper mold 270, as shown in FIG. As a result, the pulp layer MP1 is peeled off from the paper mold 240.

Next, the moving devices 250 and 330 are driven to move the press device 340 and the upper mold 350 from the second station 30 to the fourth station, and move the lifting device 260 and the upper mold 270 to the It is moved from the first station 20 to the second station 30. Subsequently, the lifting device 260 is driven to lower the upper mold 270 until the pulp layer MP1 comes into contact with the lower mold 320. After that, the suction by the pump and the upper mold 270 is stopped, and the pulp layer MP1 is released from the upper mold 270. Next, the lifting device 260 is driven to raise the upper die 270. In this way, the pulp layer MP1 is transferred from the first station 20 to the second station 30, and the pulp layer MP1 is placed on the lower mold 320.

Next, the moving devices 250 and 330 are driven to move the lifting device 260 and the upper mold 270 from the second station 30 to the first station 20, as shown in FIG. It is moved from the fourth station to the second station 30. Subsequently, the press device 340 is driven to lower the upper mold 350 as shown in FIG. Then, the pulp layer MP1 sandwiched between the upper mold 350 and the lower mold 320 is pressurized. At the same time, the heater is driven to heat the pulp layer MP1. Furthermore, at the same time, the pump is driven to suction and remove water and/or water vapor from the space sandwiched between the upper mold 350 and the lower mold 320. Thereby, the surface shape of the pulp layer MP1 is adjusted, and the pulp layer MP1 is densified and dried. In the manner described above, a pulp molded article MP2 shown in FIG. 9 is obtained.

Note that the water content of the pulp layer MP1 immediately before starting this hot pressing step is approximately equal to the water content of the pulp layer MP1 immediately after the dehydration step is finished.

In this hot pressing step, the press pressure is preferably in the range of 0.5 to 10.0 MPa, more preferably in the range of 1.0 to 10.0 MPa. If the press pressure is low, there is a possibility that a pulp molded product MP2 with high puncture strength cannot be obtained.

In this hot pressing step, the heating temperature of the pulp layer MP1, that is, the temperature of the upper die 350 or the lower die 320 heated by the heater, is preferably within the range of 130 to 200°C, and preferably within the range of 150 to 185°C. It is more preferable that the Since the pulp layer MP1 contains a large amount of pulp with short fiber length, it is difficult for water vapor to escape to the outside. Therefore, if the heating temperature is low, it takes a long time to dry the pulp layer MP1. When the heating temperature is increased, the shrinkage of the pulp layer MP1 due to drying becomes larger, and as a result, there is a possibility that the distortion in the pulp molded product MP2 becomes larger.

The pressing time in the hot pressing step depends on the heating temperature, the shape of the molded product, etc., but is preferably in the range of 10 to 140 seconds, more preferably in the range of 20 to 140 seconds.

When the press device 340 is driven so that the upper mold 350 rises to end the above hot press step, the pulp molded product MP2 is peeled off from the upper mold 350.

Next, by driving the moving devices 330 and 420, as shown in FIG. 3 station 40 to the second station 30. Subsequently, the lifting device 430 is driven to lower the holder 440 until it comes into contact with the pulp molded product MP2. Air is blown out from inside the lower mold to release the pulp molded product MP2 from the lower mold, and then the pump is driven to cause the holder 440 to adsorb and hold the pulp molded product MP2.

Next, the elevating device 430 is driven to raise the holder 440 with the pulp molded article MP2 being sucked and held by the holder 440. Subsequently, the moving devices 330 and 420 are driven to move the lifting device 430 and the holder 440 from the second station 30 to the third station 40, as shown in FIG. It is moved from the fourth station to the second station 30. Subsequently, the suction by the pump and the holder 440 is stopped, and the pulp molded article MP2 is released from the holder 440. In this way, the pulp molded article MP2 is transferred from the second station 30 to the third station 40, and the pulp molded article MP2 is placed on the stand 410.
In the manner described above, a pulp molded article MP2 is manufactured.

Thereafter, if necessary, the pulp molded product MP2 is subjected to post-processing, such as embossing, printing such as pattern printing and plain printing, coating, or a combination thereof. The coating layer formed by post-treatment may be, for example, a layer containing a chemical that imparts water resistance or oil resistance, a layer filled with a material that imparts heat insulation, a layer foamed with a foaming agent, or a combination thereof. be. By performing the post-processing, for example, the cosmetic properties of the pulp molded article MP2 can be further enhanced, or a new function can be imparted to the pulp molded article MP2.

According to the above method, it is possible to produce a pulp molded product MP2 that not only can dry in a short time but also has high puncture strength.

Further, the pulp molded product MP2 obtained by the above method has excellent surface properties. The reason for this will be explained below.

When drying is performed using an oven instead of the hot pressing process, the pulp layer has irregularities with large height differences on the surface due to the shrinkage. Also, in such a method, the pulp layer is not sufficiently densified and therefore the pulp molded article has a high porosity. Therefore, in this case, it is not possible to produce a pulp molded product with excellent surface properties.

In addition, after the dehydration process, if drying is performed using an oven, the dried product is humidified as necessary, and then subjected to heat press treatment, the difference in height of the unevenness that occurs on the surface due to drying is It can be made smaller by subsequent humidification and hot press treatment. Furthermore, the porosity can be reduced by humidification and hot press treatment. However, since the difference in height of the unevenness that occurs on the surface due to drying using an oven is very large, it cannot be sufficiently reduced by subsequent humidification and hot press treatment. Further, even if humidification and hot press treatment are performed after drying, it is difficult to sufficiently reduce the porosity.

In the method described with reference to FIGS. 3 to 11, the pulp layer MP1 is dried in the hot press step. That is, in the above method, after the dehydration step, the hot pressing step is performed without passing through the drying step.

Since a drying process is not performed before the hot pressing process, irregularities with large height differences do not occur on the surface of the pulp layer MP1. In the hot press step, the upper die 350 and the lower die 320 prevent deformation of the pulp layer MP1 due to drying. Further, since the hot pressing step is performed on the pulp layer MP1 having a high water content, movement of fibers in the in-plane direction within the pulp layer MP1 may occur appropriately. The pulp layer MP1 can be densified without causing variations in thickness.

Therefore, according to the method described with reference to FIGS. 3 to 11, it is possible to manufacture a pulp molded article MP2 with excellent surface properties. Specifically, a pulp molded article MP2 is obtained which has a region on the surface in which at least one of the arithmetic mean roughness Ra, the maximum height roughness Rz, and the average length RSm of the roughness curve elements is small. Such a pulp molded product MP2 has excellent cosmetic properties and also has excellent visibility of the uneven pattern when embossed. Further, in such a pulp molded product MP2, a printing layer and a coating layer can be easily formed.

The arithmetic mean roughness Ra is preferably within the range of 2 to 10 μm, more preferably within the range of 3 to 4.5 μm. The maximum height roughness Rz is preferably in the range of 10 to 60 μm, more preferably in the range of 20 to 35 μm. The average length RSm of the roughness curve elements is preferably within the range of 90 to 300 μm, more preferably within the range of 90 to 150 μm, and even more preferably within the range of 90 to 130 μm.

Here, "arithmetic mean roughness Ra", "maximum height roughness Rz", and "average length RSm of roughness curve elements" are surface texture parameters defined in JIS B0601:2001. The surface texture parameters are measured using, for example, a surface roughness measuring machine SJ-210 manufactured by Mitutoyo (tip radius: 2 μm, measuring force: 0.75 mN) under the following conditions.
Filter: Gasussian
Cutoff λc: 0.25mm
Cutoff λs: 8μm
Measurement speed: 0.25mm/s
Number of sections: 5
A plate-like piece is taken from the pulp molded product MP2, and measurements are performed at five arbitrary locations, and the average value is calculated.

The entire surface of the pulp molded article MP2 may have the above surface texture, or only a part of the surface may have the above surface texture. For example, only a region including a portion to be subjected to post-processing such as embossing or printing may have the above-mentioned surface texture, and other regions may not have the above-mentioned surface texture. Alternatively, one side of the pulp molded product MP2 may have the above-mentioned surface texture, and the back side may not have the above-mentioned surface texture. Such a structure can be realized, for example, by making the surface properties of some regions of the surfaces of the upper mold 350 and the lower mold 320 that are in contact with the pulp layer MP1 different from other regions.

Further, according to the method described with reference to FIGS. 3 to 11, it is possible to manufacture a pulp molded product MP2 with a small standard deviation of basis weight. The standard deviation of the basis weight of the pulp molded article MP2 is preferably 30 g/m ² or less, more preferably 15 g/m ² or less. The lower limit of this standard deviation is zero, and according to one example is 2 g/m ² .

Here, the standard deviation of the basis weight of the pulp molded article MP2 is a value obtained by the following method.

First, nine test pieces each having a rectangular shape with a width of 15 mm and a length of 40 mm are cut out from a plurality of regions located within a certain plane of the pulp molded product MP2. Next, the masses of these test pieces are measured. Thereafter, the basis weight of each test piece is calculated from its mass and area (600 mm ² ). From the basis weight obtained in this way, its standard deviation is calculated.

Next, nine test pieces are cut out from a plurality of regions located in different planes of the pulp molded product MP2 in the same manner as described above. For these test pieces as well, measure the mass and calculate the basis weight and its standard deviation.

If the pulp molded product MP2 has another surface, cut out a test piece, measure the mass, and calculate the basis weight and standard deviation for each of the remaining surfaces in the same manner as above. conduct.
The maximum value of these standard deviations is defined as the standard deviation of the basis weight of the pulp molded article MP2.

The present inventors have found that according to the method described with reference to FIGS. 3 to 11 (hereinafter referred to as the first method), it is possible to manufacture a pulp molded product MP2 with a small standard deviation of basis weight. , I believe this is due to the following reasons.

The pulp molded article can also be manufactured, for example, by the method described below (hereinafter referred to as the second method).

In the second method, first, a female mold is prepared as a paper mold. This paper mold consists of a paper mold main body with a large number of through holes and a recessed upper surface in a shape corresponding to a pulp molded product, and a mesh body provided on the inner surface of the paper mold main body along this inner surface. Contains.

Next, this paper mold is installed so that its opening faces upward. Next, a slurry containing pulp and water is supplied into the cavity of the paper mold to fill the inside of the paper mold with the slurry. Further, the supply of slurry into the paper mold is continued to deposit pulp on the net body. The slurry is supplied into the paper mold so that the slurry inside the paper mold is pressurized.

After a sufficient amount of pulp has been deposited on the net, the supply of slurry into the paper mold is stopped. Subsequently, the water remaining in the paper mold is discharged from the paper mold. For example, air is forced into the paper mold to drain water remaining in the paper mold from the paper mold.

Next, the pulp layer is pressed with the paper mold and the male upper mold to dehydrate the pulp layer. This dehydration step is performed without heating either the upper mold or the paper mold. The moisture content of the pulp layer immediately after dehydration is the same as the moisture content of the pulp layer MP1 immediately after dehydration in the first method.

Next, the pulp layer is adsorbed and held on the upper mold, and the upper mold is raised in this state. Thereby, the pulp layer is peeled off from the paper mold.

Next, the upper mold holding the pulp layer by suction is moved to the position of the lower mold, which is a female mold. Subsequently, the upper mold is lowered until the pulp layer comes into contact with the lower mold. Then, stop the suction and release the pulp layer from the upper mold. In this way, the pulp layer is placed on the lower mold.

Next, a pulp layer is sandwiched between an upper mold and a lower mold for hot press, and pressure is applied to the pulp layer between them. At the same time, the heater is driven to heat the pulp layer. Furthermore, at the same time, the pump is driven to suction and remove water and/or water vapor from the space sandwiched between the upper mold and the lower mold. In the second method, a pulp molded product is obtained as described above.

In the second method, a flow of slurry circulating within the paper mold can be generated during a period from when the supply of slurry to the paper mold is started until the inside of the paper mold is completely filled with slurry. This circulating flow may prevent settling of the pulp. However, in the second method, since it is necessary to fill the inside of the paper mold with slurry, it is not possible to adopt a structure in which water is quickly discharged from the paper mold. Therefore, after the inside of the paper mold is completely filled with slurry, even if the pressure of the slurry is increased, the circulating flow of the slurry will not be sufficient to prevent the pulp from settling, and the pulp will not settle in the slurry inside the paper mold. occurs.

As a result, the amount of pulp deposited on the sidewalls of the paper mold is greater at the bottom than at the top. If the slurry is supplied until a sufficient amount of pulp is deposited above the side walls of the paper mold, an excessive amount of pulp will be deposited at the bottom of the paper mold. If excessive pulp is deposited, the variation in the amount of pulp deposited will increase. For example, there can be a large difference in the amount of pulp deposited near the through holes provided in the paper mold body and at locations away from them.

Thus, in the second method, large variations occur in the amount of pulp deposited. During hot press treatment, fibers can move in the in-plane direction within the pulp layer, but the movement of each fiber is limited to a narrow range. That is, the variation in the amount of pulp deposited is not eliminated by the movement of fibers during hot press treatment. Therefore, according to the second method, it is not possible to produce a pulp molded product with a small standard deviation of basis weight.

On the other hand, in the first method, a paper mold 240 is installed on the top of the cover body 230, and these composites are immersed in the slurry S. The depth of the slurry S is much larger than the height of the paper mold 240. Therefore, even if pulp sedimentation occurs in the slurry S, the pulp concentration does not differ greatly between the upper position of the paper mold 240 and the lower position of the paper mold 240. Therefore, according to the first method, pulp can be deposited substantially uniformly on the paper mold 240, and a pulp molded product MP2 with a small standard deviation of basis weight can be manufactured.

The pulp molded article MP2 has an opening and does not expand in diameter in the direction away from the opening. Here, the pulp molded product MP2 has an opening and tapers in a direction away from the opening. According to such a shape, the volume of a laminate formed by stacking a plurality of pulp molded products MP2 can be reduced.

Note that in the first method, instead of pressurizing the pulp layer MP1 with the upper mold 350 and the lower mold 320, the pulp layer MP1 is sandwiched between one of the upper mold 350 and the lower mold 320 and an elastic body, and this is applied. When pressed, the elastic body deforms. Therefore, sufficient pressure is not applied to the pulp layer MP1, making it impossible to obtain a pulp molded article with excellent surface properties.

In the second method as well, if one of the upper and lower molds used in the hot press treatment is made of an elastic body, a pulp molded product with excellent surface properties cannot be obtained. Moreover, in this case, as described above, the standard deviation of basis weight becomes large.

The pulp molded article MP2 is, for example, a container. The pulp molded article MP2 may be an article other than a container. The pulp molded product MP2 may be a three-dimensional molded product, that is, a molded product that does not have a two-dimensional shape like a sheet but has a three-dimensional shape.

Note that FIGS. 3 to 11 are provided to facilitate understanding of the method for manufacturing a pulp molded product according to an embodiment of the present invention. The method described above can also be carried out using manufacturing equipment having other configurations. For example, in the manufacturing apparatus 1, the upper mold 270 and the upper mold 350 are female molds, and the paper mold 240 and the lower mold 320 are male molds. The upper mold 270 and the upper mold 350 may be male molds, and the paper mold 240 and the lower mold 320 may be female molds. In this way, various modifications can be made to the manufacturing apparatus 1 and manufacturing method described above.

Specific examples of the present invention will be described below. The present invention is not limited to these specific examples.

<1> Manufacturing of pulp molded products (Example 1)
A slurry consisting of pulp, water, and a sizing agent was prepared using a pulper. The pulp content of the slurry was 1.0% by mass. Bamboo pulp was used as the pulp. As the sizing agent, an alkyl ketene dimer (AKD)-based sizing agent (trade name: Sizepine (registered trademark) K-903-20) manufactured by Arakawa Chemical Industries, Ltd. was used. The solid content of the sizing agent in the solid content of the slurry was 0.3% by mass.

Using this slurry, a pulp molded article was manufactured by the method described with reference to FIGS. 3 to 11. Here, the dehydration step was performed such that the water content of the pulp layer immediately after dehydration was 69.5% by mass. The hot pressing step was carried out at a heating temperature of 180° C., a pressing pressure of 3.0 MPa, and a pressing time of 120 seconds. In the dehydration step and hot press step, the clearance between the upper mold and the lower mold was set to 1.0 mm so that a pulp molded product with a wall thickness of 1.0 mm was obtained.
In the manner described above, a container was manufactured as a pulp molded product.

(Example 2)
A pulp molded article was produced in the same manner as in Example 1, except that a mixture of 80 parts by mass of bamboo pulp and 20 parts by mass of sugarcane pulp was used as the pulp.

(Example 3)
A mixture of 70 parts by mass of bamboo pulp and 30 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 1.1 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the diameter was 1.1 mm.

(Example 4)
A mixture of 70 parts by mass of bamboo pulp and 30 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 1.2 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the diameter was 1.2 mm.

(Example 5)
A mixture of 70 parts by mass of bamboo pulp and 30 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 0.74 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the diameter was 0.74 mm.

(Example 6)
A mixture of 70 parts by mass of bamboo pulp and 30 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 0.70 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the pressure was 0.70 mm and the press pressure was 10 MPa.

(Example 7)
A mixture of 60 parts by mass of bamboo pulp and 40 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 1.01 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the diameter was 1.01 mm.

(Example 8)
A pulp molded article was produced in the same manner as in Example 1, except that a mixture of 50 parts by mass of bamboo pulp and 50 parts by mass of sugarcane pulp was used as the pulp.

(Example 9)
A pulp molded article was produced in the same manner as in Example 1, except that a mixture of 40 parts by mass of bamboo pulp and 60 parts by mass of sugarcane pulp was used as the pulp.

(Example 10)
A pulp molded product was produced in the same manner as in Example 1, except that a mixture of 20 parts by mass of bamboo pulp and 80 parts by mass of sugarcane pulp was used as the pulp.

(Example 11)
A pulp molded product was produced in the same manner as in Example 1 except that sugarcane pulp was used as the pulp.

(Example 12)
A slurry consisting of pulp, water, a sizing agent, and a paper strength enhancer was used as the slurry, and the clearance between the upper mold and the lower mold was adjusted so that a pulp molded product with a wall thickness of 0.72 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the thickness was 0.72 mm and the pressing time was 140 seconds. As the paper strength enhancer, Polystron (registered trademark) 1280 (polyacrylamide) manufactured by Arakawa Chemical Industries, Ltd. was used. The solid content of the paper strength enhancer in the solid content of the slurry was 1.0% by mass.

(Example 13)
A slurry consisting of pulp, water, a sizing agent, and a paper strength enhancer was used as the slurry, and the clearance between the upper mold and the lower mold was adjusted so that a pulp molded product with a wall thickness of 0.70 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the thickness was 0.70 mm and the pressing time was 140 seconds. In Example 13, a mixture of 80 parts by mass of bamboo pulp and 20 parts by mass of sugarcane pulp was used as the pulp. As the paper strength enhancer, Polystron (registered trademark) 1280 (polyacrylamide) manufactured by Arakawa Chemical Industries, Ltd. was used. The solid content of the paper strength enhancer in the solid content of the slurry was 1.0% by mass.

(Example 14)
A slurry consisting of pulp, water, a sizing agent, and a paper strength enhancer was used as the slurry, and the clearance between the upper mold and the lower mold was adjusted so that a pulp molded product with a wall thickness of 0.70 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the thickness was 0.70 mm and the pressing time was 140 seconds. In Example 14, a mixture of 70 parts by mass of bamboo pulp and 30 parts by mass of sugarcane pulp was used as the pulp. As the paper strength enhancer, Polystron (registered trademark) 1280 (polyacrylamide) manufactured by Arakawa Chemical Industries, Ltd. was used. The solid content of the paper strength enhancer in the solid content of the slurry was 1.0% by mass.

(Example 15)
A pulp molded product was produced in the same manner as in Example 14, except that DS4424 (polyacrylamide) manufactured by Seiko PMC Co., Ltd. was used as the paper strength enhancer. In Example 15, the proportion of the solid content of the paper strength enhancer in the solid content of the slurry was 1.0% by mass, as in Example 14.

(Example 16)
Except that DS4424 (polyacrylamide) manufactured by Seiko PMC Co., Ltd. was used as the paper strength enhancer, and the solid content of the paper strength enhancer in the solid content of the slurry was 2.0% by mass. A pulp molded article was produced in the same manner as in Example 14.

(Example 17)
A mixture of 50 parts by mass of bamboo pulp and 50 parts by mass of sugarcane pulp was used as the pulp, and the clearance between the upper and lower molds was adjusted so that a pulp molded product with a wall thickness of 0.72 mm was obtained. A pulp molded product was produced in the same manner as in Example 1, except that the pressure was 10 MPa, and the press time was 140 seconds.

(Comparative example 1)
A pulp molded product was produced in the same manner as in Example 1, except that sugarcane pulp was used as the pulp, the press pressure was 30 MPa, and the press time was 300 seconds.

(Comparative example 2)
Except that a mixture of 50 parts by mass of bamboo pulp and 50 parts by mass of sugarcane pulp was used as the pulp, and instead of the heat pressing process, heat drying was performed at 180 ° C. for 140 seconds using an oven. A pulp molded article was produced in the same manner as in Example 1.

<2> Evaluation For each of the pulp molded products manufactured in Examples 1 to 17 and Comparative Examples 1 and 2, various measurements were performed using the methods described above (i.e., pulp average fiber length, Canadian standard freeness, density, thickness). , and measurement of puncture strength).

Further, each of the pulp molded products produced in Examples 1 to 17 and Comparative Examples 1 and 2 was embossed to produce embossed pulp molded products. Embossing was performed by pressing an embossing roll provided with an uneven pattern onto the pulp molded product under heat and pressure (hot stamping method).

It was visually confirmed whether or not any tears occurred due to the embossing process. In addition, the formability of the uneven pattern formed by the embossing process was visually confirmed.

The evaluation criteria were as follows.
(occurrence of tear)
1. Tears can be seen in many places in the embossed part by visual inspection.
2 A tear can be confirmed in a part of the embossed part by visual observation.
3 No tears were observed in the embossed part by visual observation, and there were no problems in actual use.
4 No tears were observed in the embossed area when observed using a scale magnifying glass.
(Formability)
1. The uneven pattern is hardly visible when observed with the naked eye.
2 The uneven pattern is barely visible when observed with the naked eye.
3 The uneven pattern can be confirmed by visual observation, but it is partially unclear.
4. The entire uneven pattern can be clearly seen by observing with the naked eye.

The results of measurement and evaluation are shown in Tables 1 to 3 below.

In Examples 1 to 17, it was possible to produce pulp molded articles having puncture strengths within the range of 40 to 85N. When such a pulp molded product was subjected to embossing, a concavo-convex pattern that was visible to the naked eye could be formed without causing any tearing in the embossed part.

On the other hand, the pulp molded product of Comparative Example 1 had excessively high puncture strength. When such a pulp molded article was subjected to embossing, no breakage occurred in the embossed part, but it was not possible to form an uneven pattern that was visible to the naked eye. Further, the pulp molded product of Comparative Example 2 had excessively low puncture strength. When such a pulp molded article was subjected to embossing, it was possible to form a concavo-convex pattern that was visible to the naked eye, but the embossed part was broken at many locations.

DESCRIPTION OF SYMBOLS 1... Manufacturing device, 10... Support body, 20... First station, 30... Second station, 40... Third station, 210... Container, 220... Lifting device, 230... Cover body, 240... Paper mold, 250... Movement Device, 260... Lifting device, 270... Upper die, 310... Stand, 320... Lower die, 330... Moving device, 340... Pressing device, 350... Upper die, 410... Stand, 420... Moving device, 430... Elevating device, 440... Holder, MP1... Pulp layer, MP2... Pulp molded product, S... Slurry.

Claims (8)

Pulp molded product with puncture strength within the range of 40 to 85N. The pulp molded product according to claim 1, having a density within the range of 0.5 to 1.1 g/cm ³ . The pulp molded product according to claim 1, wherein the thickness of the wall portion is within the range of 0.6 to 1.2 mm. The pulp molded product according to claim 1, wherein the average fiber length of the pulp is within the range of 0.7 to 2.0 mm. The pulp molded product according to claim 1, containing a paper strength enhancer. The pulp molded article according to claim 1, containing a sizing agent. An embossed pulp molded product with a puncture strength in the range of 40 to 85N and whose wall portion includes an embossed part. A method for producing an embossed pulp molded product, comprising embossing a wall portion of the pulp molded product according to any one of claims 1 to 6.