JP2023021922A - Pulp molded product and production method thereof - Google Patents

Abstract

To provide a pulp molded product having a small thickness and a high strength, excellent in mold releasability in production.SOLUTION: A pulp molded product MP2 of the present invention includes pulp with a fiber length of 1 mm or less at a proportion in the range of 35% to 50% in the whole pulp having an average fiber length in the range of 1.2 to 1.5 mm, a density of 0.65 to 1.3 g/cm3, and a nitrogen content in the range of 400 to 2000 μg/g.SELECTED DRAWING: Figure 1

Description

The present invention relates to pulp molded articles.

In recent years, environmental problems related to an increase in waste and the like have occurred frequently. In view of this, paper containers are being used in place of plastic and metal containers for storing toiletries, beverages, food, and the like. For example, paper containers for liquids such as milk containers are made of paperboard coated with polyethylene resin on both sides of the paper and have a gable-topped upper portion, so-called gable-top paper containers. Such a paper container contributes not only to resource saving and energy saving, but also to environmental protection such as being easy to recycle or incinerate when discarded. Therefore, paper containers are popular in various fields.

However, the paper container as described above is formed by folding and pasting paperboard, and therefore the manufacturing process is complicated and the manufacturing cost increases. In addition, paper containers as described above have a low degree of freedom in their shape, and thus have problems such as being unable to sufficiently demonstrate the appealing power of products based on the shape of the container.

As one means for increasing the degree of freedom in the shape of paper containers, there is a pulp mold for producing a molded product from a slurry containing pulp and water. Pulp molding generally involves depositing pulp in a slurry onto a paper mold to form a pulp layer, dewatering the pulp layer, and then drying it in an oven. Molded articles obtained by this technology, that is, pulp molded articles, are excellent in heat resistance, cold resistance, moisture absorption and desorption, etc., which are characteristics of paper-based packaging materials. It has come to be widely used as a fixing cushioning material for containers, fruits, etc. (Patent Document 1).

JP 2008-285188 A

An object of the present invention is to realize a pulp molded article having a small thickness, high strength, and excellent releasability during production.

According to one aspect of the present invention, the ratio of fibers having a fiber length of 1 mm or less in the pulp is in the range of 35 to 50%, and the average fiber length of the pulp is in the range of 1.2 to 1.5 mm. and having a density in the range of 0.65 to 1.3 g/cm ³ and a nitrogen content in the range of 400 to 2000 μg/g.

According to another aspect of the present invention, there is provided a pulp molded article according to the above aspect having a thickness in the range of 0.5 to 1 mm.

According to still another aspect of the present invention, the pulp according to any of the above aspects having a density in the range of 0.65 to 0.80 g/cm ³ and a nitrogen content in the range of 500 to 1000 μg/g A molded article is provided.

According to still another aspect of the present invention there is provided a pulp molded article according to any of the above aspects having a tensile strength in the range of 30 to 55 kN/m.

According to still another aspect of the present invention, there is provided a pulp molded article according to any of the aspects above, wherein the peel strength is in the range of 0.3 to 0.9 N/mm ² .

According to still another aspect of the present invention, there is provided a pulp molded article according to any of the above aspects, wherein the standard deviation of basis weight is within the range of 2 to 30 g/m ² .

According to still another aspect of the present invention, there is provided a pulp molded article according to any of the above aspects, which is a container.

According to still another aspect of the present invention, preparing a slurry containing pulp and water and having a fiber length of 1 mm or less in the pulp in a range of 35 to 50%; Dehydrating the pulp layer to obtain an intermediate molded product; A method for producing a pulp molded article is provided comprising heating to a temperature in the range of 150-220° C. while applying a pressure in the range of 0.4-4.5 MPa between.

According to still another aspect of the present invention, the pulp is deposited on the mold by preparing a cover body as a hollow body having an opening, and fixing the mold to the opening. , immersing the mold fixed to the opening in the slurry; and depressurizing a space surrounded by the cover body and the mold immersed in the slurry. A method of manufacturing a pulp molded article according to aspects is provided.

According to still another aspect of the present invention, there is provided a method for producing a pulp molded product according to any one of the above aspects, wherein the mold is immersed in the slurry so that the mold is positioned above the cover body. be done.

According to still another aspect of the present invention, the pressure and heat applied to the undried intermediate molded product sandwiched between the male mold and the female mold are each within the range of 0.4 to 2.0 MPa. and a temperature in the range of 150 to 200°C.

According to the present invention, it is possible to realize a pulp molded article having a small thickness, high strength, and excellent releasability during production.

BRIEF DESCRIPTION OF THE DRAWINGS The perspective view which shows the pulp molded article which concerns on one Embodiment of this invention. The figure which shows roughly an example of the manufacturing apparatus which can be utilized for manufacture of the pulp molded article of FIG. FIG. 3 is a view showing a pulp layer forming step in pulp molding using the apparatus of FIG. 2; Sectional drawing which shows roughly an example of the pulp layer formed on the papermaking mold. FIG. 3 is a diagram showing a dehydration process in pulp molding using the apparatus of FIG. 2; The figure which shows the conveyance process of the pulp layer in pulp mold molding using the apparatus of FIG. FIG. 3 is a view showing a hot press forming process in pulp molding using the apparatus of FIG. 2; BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows roughly an example of the pulp molded article obtained by a hot-press process. FIG. 3 is a diagram showing a process of conveying a molded pulp product in pulp molding using the apparatus of FIG. 2 ; The figure which shows the state which completed the conveyance process of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Components having the same or similar functions are denoted by the same reference numerals throughout the drawings, and overlapping descriptions are omitted.

<1> Pulp Molded Product FIG. 1 is a perspective view showing a pulp molded product according to one embodiment of the present invention.
The pulp molded product MP2 shown in FIG. 1 is a container. The pulp mold MP2 includes a bottom and side walls and is open at the top.

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

The side wall has a tubular shape extending upward from the edge of the bottom. The side wall portion widens 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 whose side wall portion expands from the bottom toward the opening is advantageous in achieving high releasability and is easy to stack.

The pulp molded article MP2 can have various shapes such as cup-shaped, bowl-shaped, tray-shaped, and box-shaped. The pulp molded product MP2 does not have to be a three-dimensional molded product, that is, a molded product having a three-dimensional shape such as a sheet, and may not be a container.

The pulp molded article MP2 has a thickness of 1 mm or less. That is, the pulp molded article MP2 has a wall thickness of 1 mm or less, in this case, the thickness of the bottom and side walls. The pulp molded product MP2 preferably has a thickness of 0.8 mm or less. Thick pulp molds MP2 are bulky, especially when stacked. In addition, thinning the walls of the pulp molded article MP2 is advantageous in that the drying process during manufacture can be completed in a short period of time.

The pulp molded article MP2 preferably has a thickness of 0.5 mm or more, more preferably 0.6 mm or more, and even more preferably 0.7 mm or more. The pulp molded product MP2 having thin walls is likely to have uneven wall thicknesses.

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 molded pulp MP2. The thickness is then measured for each specimen. For thickness measurement, for example, a Mitutoyo thickness gauge is used. The thickness of the molded pulp MP2 is the average value of the measurement results obtained for five test pieces.

In the pulp molded product MP2, the proportion of fibers having a fiber length of 1 mm or less in the pulp is in the range of 35 to 50%. This percentage is preferably in the range of 40-50%, more preferably in the range of 40-48%. When this ratio is increased, it becomes easier to increase the density of the pulp molded article MP2, and the strength thereof increases. Furthermore, when this ratio is increased, it becomes easier to obtain a pulp molded article MP2 with excellent cosmetic properties. However, if this ratio is excessively increased, it becomes difficult to complete drying in a short period of time during production, or cracks due to poor drying and deterioration of releasability tend to occur.

Here, the ratio of fibers having a fiber length of 1 mm or less in the pulp is the ratio of the number (fibers) of fibers having a fiber length of 1 mm or less to the total number of fibers (fibers) of the pulp. This ratio is obtained by the following method.

First, a 5 g test piece is obtained from the pulp molded product MP2. Next, this test piece is finely shredded and soaked in water overnight so that the total mass becomes 500 g. This is then agitated with an agitator to disaggregate the pulp from each other. Thus, a dispersion containing pulp is obtained. Next, an appropriate amount is sampled 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 in accordance with JIS P8226-2:2011 "Pulp-Method for measuring fiber length by automatic optical analysis method-Part 2: Non-polarization method". The fiber length measurement ends when 20,000 or more fibers having a fiber length of 0.2 mm or more are detected. From the frequency distribution of the fiber lengths obtained by this fiber length measurement, the ratio of fibers having a fiber length of 1 mm or less in the pulp is determined.

In the pulp molded article MP2, the proportion of fibers having a fiber length of 0.2 mm or less in the pulp is preferably in the range of 20 to 35%, more preferably in the range of 25 to 33%. When this ratio is increased, a dense layer can be formed with a small amount of pulp, and improvement in strength and smoothness of the surface can be expected. However, if this ratio is excessively increased, the resulting pulp layer becomes uneven due to a decrease in freeness, the dewatering process takes a long time and the production efficiency drops, or the pulp cannot be dewatered to a predetermined moisture content and the shape cannot be maintained. .

Here, the ratio of fibers having a fiber length of 0.2 mm or less in the pulp is the ratio of the number (fibers) of fibers having a fiber length of 0.2 mm or less to the total number of fibers (fibers) of the pulp. This ratio is obtained by the following method.

First, a 5 g test piece is obtained from the pulp molded product MP2. Next, this test piece is finely shredded and soaked in water overnight so that the total mass becomes 500 g. This is then agitated with an agitator to disaggregate the pulp from each other. Thus, a dispersion containing pulp is obtained. Next, an appropriate amount is sampled 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 in accordance with JIS P8226-2:2011 "Pulp-Method for measuring fiber length by automatic optical analysis method-Part 2: Non-polarization method". The fiber length measurement ends when 20,000 or more fibers having a fiber length of 0.2 mm or more are detected. From the frequency distribution of the fiber length obtained by this fiber length measurement, the proportion of pulp having a fiber length of 0.2 mm or less is determined.

In the molded pulp MP2, the average fiber length of the pulp is preferably in the range of 1.2 to 1.5 mm, more preferably in the range of 1.3 to 1.5 mm. Increasing the average fiber length reduces the strength of the molded pulp MP2. If the average fiber length is reduced, a longer drying time is required during manufacture. The average fiber length is the length-weighted average fiber length LL obtained by measuring the fiber length according to the method described above regarding the ratio of fibers having a fiber length of 1 mm or less in the pulp.

The pulp suspension obtained by dispersing the pulp contained in the pulp molded article MP2 in water preferably has a Canadian Standard Freeness (CSF) of 640 mL or less, more preferably 620 mL or less, and 610 mL. More preferably: When the Canadian standard freeness is high, the strength of the molded pulp MP2 tends to be low.

The Canadian standard freeness is preferably 500 mL or more, more preferably 530 mL or more, and even more preferably 550 mL or more. If the Canadian standard freeness is high, the molded pulp MP2 tends to require a long drying time during its production.

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 pulp-containing dispersion is obtained in the same manner as described above. Next, this dispersion is diluted with water so that the solid content concentration becomes 0.3% by mass to obtain an aqueous suspension of pulp. Then, 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. Further, the measured value is corrected by referring to a correction table for the suspension temperature measured in advance. Thus, the Canadian Standard Freeness is obtained.

It is assumed that the pulp molded article MP2 or a containerized article containing this as a container body will be piled up during transportation, display, and the like, for example. Stacked containerized articles may break the container body, for example, due to the impact caused by dropping. The pulp molded article MP2 is required to have sufficient strength, especially sufficient impact resistance under such circumstances.

The pulp molded product MP2 preferably has a tensile strength in the range of 30 to 55 kN/m, more preferably in the range of 35 to 55 kN/m, and in the range of 40 to 55 kN/m. is more preferred. Strengthening the interfiber bonding in the in-plane direction tends to increase the tensile strength. Therefore, increasing the tensile strength can improve impact resistance. However, if the tensile strength is excessively increased, for example, it is likely to be damaged under conditions where a large impact such as dropping is applied. That is, the pulp molded product MP2 becomes brittle.

The pulp molded product MP2 preferably has a tensile elongation at break in the range of 5 to 25%, more preferably in the range of 10 to 25%, and further preferably in the range of 15 to 25%. preferable. If the tensile elongation at break of the pulp molded article MP2 is increased, it will deform and absorb the impact when a large impact is applied, so that it can withstand the impact without cracking or the like.

Here, the above tensile strength and tensile elongation at break are values obtained by the following method. First, a strip-shaped test piece with a width of 15 mm and a length of 40 mm is cut out from a portion of the pulp molded article MP2 where the surface is not curved. Next, the thickness and mass of this test piece are measured. Then, using this test piece, the measurement specified in JIS P8113:2006 "Paper and paperboard-Testing methods for tensile properties-Part 2: Constant rate stretching method" is performed. Here, the strip is gripped so that the distance between the grippers is 20 mm. Also, the moving speed of the grippers, that is, the elongation speed of the test piece is set to 20 mm/min. Each of tensile strength and tensile elongation at break is an average value of values obtained by three measurements.

The pulp molded article MP2 preferably has a peel strength in the range of 0.3 to 0.9 N/mm ² , more preferably in the range of 0.5 to 0.9 N/mm ² , More preferably, it is in the range of 0.6 to 0.9 N/ ^mm2 . Strengthening the interfiber bonding in the thickness direction of the pulp molded article MP2, ie, in the direction perpendicular to the surface, tends to increase the peel strength. If the peel strength is low, the fiber bonding in the thickness direction is weak, and when a large impact is applied to the pulp molded product 2, there is a risk that cracks will occur from the inside. In addition, if the peel strength is low, surface peeling or the like is likely to occur when a force such as rubbing is applied in a direction parallel to the surface. Thus, from the viewpoint of strength, it is preferable that the peel strength is high. However, in order to achieve a peel strength exceeding the upper limit, excessive densification is required, which may lead to a decrease in productivity.

Here, the above-mentioned peel strength is a value obtained by "Internal bond strength test method-Part 1: Z-axis direction tensile test method" described in JAPAN TAPPI 18-1. First, a square test piece having a side of 25 mm is cut out from the molded pulp MP2. Next, double-sided adhesive tapes are attached to both sides of this test piece, and the test piece is fixed to upper and lower jigs via these double-sided adhesive tapes. As the double-sided adhesive tape, for example, 3M Scotch Tape (registered trademark) #400 is used. These jigs are pressed against each other with a load of 150 kgf, and this state is maintained for 20 seconds. As a result, the sample piece is crimped to the jig. Thereafter, while fixing the position of the lower jig, the upper jig is raised at a speed of 20 mm/min to cause delamination of the test piece and obtain the maximum load at that time. The peel strength is the average value of the maximum load obtained by two measurements.

Pulp molded article MP2 has a density in the range of 0.65 g to 1.3/cm ³ . The density of the pulp molded article MP2 is preferably in the range of 0.7 g to 1.3/cm ³ and more preferably in the range of 0.8 g to 1.3/cm ³ . The density of the pulp molded article MP2 may be in the range of 0.65 to 0.80 g/ ^cm3 .

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 product MP2 where the surface is not curved, and the dimensions, mass and thickness are measured. Calculate the density from the obtained value.

The pulp molded article MP2 preferably further contains a paper strength agent such as polyacrylamide. Using a paper strength agent can increase the strength of the molded pulp MP2. Among the paper strength agents, polyacrylamide is particularly convenient in the production of molded pulp MP2.

The pulp molded article MP2 produced using the paper strength agent has a higher nitrogen content than the pulp molded article MP2 produced without using the paper strength agent. The nitrogen content of the pulp molded product MP2 produced using the paper strength agent is in the range of 400 to 2000 µg/g, preferably in the range of 500 to 1500 µg/g, more preferably 600 to 1500 µg/g. It is in the range of 1500 μg/g. The nitrogen content of the pulp molded article MP2 may be in the range of 500-1000 μg/g.

When the nitrogen content of the pulp molded article MP2 is reduced, the strength of the pulp molded article MP2 is lowered, and damage, etc., is likely to occur when a large impact is applied. If the nitrogen content is reduced, there is a possibility that the shape retention of the container may deteriorate when used as a product in a container. If the nitrogen content is excessively increased, fiber aggregates become large, and the effect of improving the strength due to the increase in the nitrogen content reaches a ceiling.

The nitrogen content of pulp molded article MP2 is obtained by the following method. First, two test pieces are taken from arbitrary positions of the molded pulp MP2. The mass of each test piece shall be 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 Air Analytic Tech can be used. The nitrogen content is the mean value of the measurements obtained on two test pieces.

<2> Production Apparatus for Pulp Molded Article Next, a production apparatus that can be used for producing the pulp molded article MP2 will be described.
FIG. 2 is a diagram schematically showing an example of manufacturing equipment that can be used to manufacture the molded pulp product of FIG.

The manufacturing apparatus 1 shown in FIG. 2 includes a support 10 , a first station 20 , a second station 30 and a third station 40 .

The support 10 includes a frame and rails installed thereon.

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

The container 210 is installed inside the frame of the support 10 . Container 210 is open at the top. The container 210 contains slurry S containing pulp and water.

The lifting device 220 is attached to the frame of the support 10 above the container 210 . Lifting device 220 includes, for example, a hydraulic cylinder. The lifting device 220 supports the cover body 230 . The lifting device 220 can lift and lower the cover body 230 at the position of 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 papermaking mold 240 is fixed to the opening of the cover body 230 . Specifically, the mold making 240 is fixed to the opening of the cover body 230 so that the space adjacent to one surface of the mold making 240 is surrounded by the mold making 240 and the cover body 230 .

The papermaking mold 240 is a liquid-permeable mold. The papermaking mold 240 has a three-dimensional shape. That is, the papermaking mold 240 has one or more convex portions and/or one or more concave portions on the surface on which the pulp is deposited. Specifically, the outer surface of the 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 mold 240 is a male mold with a protruding upper surface.

The mold 240 includes, for example, a 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 mold main body provided on the outer surface along the outer surface. and 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 transferred between the first station 20 and the second station 30 .

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

The upper mold 270 is a holder that sandwiches a pulp layer, which will be described later, between itself and the mold 240 and holds the pulp layer by vacuum adsorption. The lower surface of the upper mold 270 has a shape corresponding to the outer surface of the mold 240 . Here, the upper mold 270 is a female mold with a concave lower surface. The upper die 270 has, for example, a large number of through-holes, one end of which is open on the bottom surface and the other end of which is 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 platform 310 is installed inside the frame of the support 10 . A lower mold 320 is installed on the base 310 .

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

The moving device 330 is movable along the rails of the support 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 positioned at the second station 30, movement in the vertical, horizontal, and longitudinal directions can be restricted by the lock mechanism. A press device 340 is also attached to the transfer 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. A press device 340 supports an upper die 350 . The press device 340 can raise and lower the upper die 350 .

Upper mold 350 is a mold that is not permeable to gas or liquid. The lower surface of the upper mold 350 has a shape corresponding to the outer surface of the mold 240 . Here, the upper mold 350 is a female mold with a concave lower surface. The upper mold 350 has a smooth surface having a shape corresponding to the outer surface of the mold 240 .

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

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

The base 410 is installed inside the frame of the support 10 . A pulp mold is placed on the table 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 transferred between the second station 30 and the third station 40 .

Lifting device 430 is attached to moving device 420 as described above. Lifting device 430 includes, for example, a hydraulic cylinder. Lifting device 430 supports holder 440 . Lifting device 430 may raise and lower retainer 440 .

The holder 440 is a holder that holds a pulp molded article, 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 mold 240 . Here, the holder 440 has a shape with a concave lower surface. The holder 440 has, for example, a large number of through-holes, one end of which is open on the bottom surface and the other end of which is connected to a pump.

<3> Manufacturing method of pulp molded article In the manufacturing method according to one embodiment of the present invention, for example, the pulp molded article MP2 is manufactured using the manufacturing apparatus 1 described above. This will be described with reference to FIGS. 1 to 10. FIG.

FIG. 3 is a diagram showing a pulp layer forming step in pulp molding using the apparatus of FIG. FIG. 4 is a cross-sectional view schematically showing an example of a pulp layer formed on a papermaking mold. FIG. 5 is a diagram showing a dewatering process in pulp molding using the apparatus of FIG. FIG. 6 is a diagram showing a transfer process of a pulp layer in pulp molding using the apparatus of FIG. FIG. 7 is a diagram showing a hot press molding process in pulp molding using the apparatus of FIG. FIG. 8 is a cross-sectional view schematically showing an example of a pulp molded article obtained by a hot press process. FIG. 9 is a diagram showing a transfer process of a pulp molded article in pulp molding using the apparatus of FIG. FIG. 10 is a diagram showing a state after the transfer process of FIG. 9 is completed.

In this method, first, slurry S is prepared.
The slurry S contains pulp and water as described above. The slurry S is a suspension of pulp dispersed in water and having a high viscosity.

The pulp contained in slurry S has substantially the same characteristics as described above for the pulp contained in pulp mold MP2.

The type of pulp used for the slurry S is not particularly limited. Examples of 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 consideration such as forest conservation and utilization of unused resources.

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

Wood pulp can be classified by source. Wood pulps include softwood pulps and hardwood pulps. Examples of softwood pulp include pulp obtained from the genus Fir, Pinus, and the like. Examples of hardwood pulp include pulp obtained from the genus Acacia, the genus Eucalyptus, the genus Beech, the genus Aspen (for example, poplar), and the like.

Non-wood pulp is obtained from fibers harvested from plant skins, stems, leaves and sheaths. Specifically, pulp obtained from cotton linter, cotton, linen, hemp, ramie, straw, esparto, manila hemp, zeisal hemp, jute, flax, kenaf, bamboo, sugar cane, gampi, mitsumata, kozo, and mulberry. mentioned. Among them, bamboo and sugarcane pulp are preferred.

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

Pulp differs in fiber length and the like 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. Also, the average fiber length of the pulp can be adjusted by any method, for example, by mechanical treatment such as beating and pulverization. Therefore, a pulp having a certain characteristic can be obtained, for example, by selecting an appropriate one from a plurality of types of pulp, or by appropriately combining two or more types of pulp. As the pulp, it is preferable to use non-wood pulp, and it is preferable to use pulp made from sugar cane, pulp made from bamboo, or a combination thereof.

The pulp content of 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. Low pulp content makes it difficult to achieve high productivity. A high pulp content can lead to large variations in the thickness of the pulp layer.

The slurry S preferably further contains a paper strength agent. The ratio of the paper strength agent to the total of the pulp and the paper strength agent (solid content basis) is preferably in the range of 0.3 to 3% by mass, and in the range of 0.5 to 2% by mass more preferably in the range of 0.7 to 2% by mass.

The slurry S can further contain other additives. As additives, organic low-molecular-weight materials, organic high-molecular-weight materials, inorganic materials, or combinations thereof can be used. A chemical agent may be selected according to the required performance as a container.

The ratio of the additive to the total of the pulp and the additive is preferably 10% by mass or less, more preferably 5% by mass or less. That is, the proportion of pulp in the total solid content of the slurry S is preferably 90% by mass or more, more preferably 95% by mass or more.

Next, slurry S is supplied into container 210 . Next, as shown in FIG. 3, the cover body 230 is lowered by the lifting device 220 to position the upper surface of the mold 240 sufficiently below the liquid surface of the slurry S. Then, as shown in FIG. In this state, the pump is driven to depressurize the space surrounded by the cover body 230 and the mold 240 . This causes the slurry S to flow across the mold 240 and deposit the pulp on the mold 240 . As described above, the pulp layer MP1 is formed on the mold 240 as shown in FIG.

Next, while driving the pump, as shown in FIG. As a result, the pulp layer MP1 is dehydrated under reduced pressure. Next, the lifting device 260 is driven to lower the upper mold 270 until its lower surface contacts the pulp layer MP1. In addition, the pulp layer MP1 is not drawn in FIG. This dehydration step is performed without heating either the upper mold 270 or the papermaking mold 240 .

The decompression 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 in the range of 60 to 70% by mass. It is even more preferable to have If the moisture content is low, the movement of the fibers in the in-plane direction within the pulp layer may be insufficient in the hot press step. If the moisture content is high, the movement of fibers in the in-plane direction within the pulp layer becomes excessive in the hot press process, or within the period from the end of the dehydration process to the start of the hot press process , the shape retention of the pulp layer MP1 may be insufficient.

After stopping the depressurization of the space and the pressurization, the pump is driven to cause the upper mold 270 to adsorb and hold the pulp layer MP1. The suction by the pump and the upper mold 270 does not cause further dehydration of the pulp layer MP1.

Next, the lifting device 260 is driven while the upper mold 270 is holding the pulp layer MP1 by suction, and the upper mold 270 is lifted as shown in FIG. As a result, the pulp layer MP1 is separated from the mold 240. As shown in FIG.

Next, the moving devices 250 and 330 are driven to move the pressing device 340 and the upper die 350 from the second station 30 to the fourth station as shown in FIG. 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 to release the pulp layer MP1 from the upper mold 270 . Next, the lifting device 260 is driven to lift the upper die 270 . In this manner, 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. As shown in FIG.

Next, the moving devices 250 and 330 are driven to move the lifting device 260 and the upper die 270 from the second station 30 to the first station 20 as shown in FIG. Move from the fourth station to the second station 30 . Subsequently, the press device 340 is driven to lower the upper die 350 as shown in FIG. Then, the upper mold 350 and the lower mold 320 press the pulp layer MP1 sandwiched therebetween. At the same time, the heater is driven to heat the pulp layer MP1. Furthermore, along with this, the pump is driven to suck and remove water and/or water vapor from the space sandwiched between the upper mold 350 and the lower mold 320 . As a result, the surface shape of the pulp layer MP1 is adjusted, and the pulp layer MP1 is densified and dried. As described above, a molded pulp MP2 shown in FIG. 8 is obtained.

The moisture content of the pulp layer MP1 immediately before starting the hot pressing process is substantially equal to the moisture content of the pulp layer MP1 immediately after finishing the dehydration process.

In this hot press step, the press pressure is preferably in the range of 0.4 to 4.5 MPa, more preferably in the range of 0.8 to 2.5 MPa. If the pressing pressure is too low, there is a possibility that a high-density pulp molded article MP2 cannot be obtained. The pulp layer MP1 contains a lot of pulp with short fiber length. Such pulp is prone to migration within the pulp layer MP1, especially if the pressing pressure is too high. Therefore, if the press pressure is excessively high, the thickness of the pulp molded product MP2 tends to vary. The pressing pressure may be in the range of 0.4-2.0 MPa.

In this hot press step, the heating temperature of the pulp layer MP1, that is, the temperature of the upper mold 350 or the lower mold 320 heated by the heater is preferably in the range of 150 to 220°C, more preferably in the range of 150 to 200°C. and more preferably in the range of 165 to 190°C. Since the pulp layer MP1 contains a large amount of pulp having a 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. If the heating temperature is increased, the shrinkage of the pulp layer MP1 due to drying becomes greater, which may result in greater strain in the molded pulp MP2.

The pressing time in the hot pressing process is preferably in the range of 10 to 300 seconds, more preferably in the range of 20 to 200 seconds, depending on the heating temperature, the shape of the molded product, and the like.

When the pressing device 340 is driven so as to raise the upper mold 350 at the end of the hot press process, the pulp molded product MP2 is separated from the upper mold 350. As shown in FIG.

Next, the moving devices 330 and 420 are driven to move the pressing device 340 and the upper die 350 from the second station 30 to the fourth station as shown in FIG. It is moved from the 3rd station 40 to the 2nd station 30 . Subsequently, the lifting device 430 is driven to lower the holder 440 until the holder 440 comes into contact with the pulp molded product MP2. Air is ejected from the inside of 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. The lifting device 430 is driven to lift the holder 440 while the molded product MP2 is held by suction. 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. Move 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. FIG. In this manner, 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 table 410. FIG.
As described above, the molded pulp MP2 is produced.

After that, if necessary, the pulp molded article MP2 is subjected to post-treatment, for example, printing such as pattern printing and plain printing, coating, or a combination thereof. The coating layer formed by post-treatment is, 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-treatment, for example, it is possible to further enhance the cosmetic properties of the pulp molded article MP2 and to impart new functions to the pulp molded article MP2.

According to the above method, it is possible to achieve excellent releasability during production, and to produce a pulp molded article MP2 having a small thickness and high strength. The excellent releasability means that the pulp molded product MP2 can be released from the lower mold by blowing air, and that the release does not cause peeling or cracking of the surface. means.

Since the pulp molded article MP2 has a small wall thickness, it is lightweight and has a small stacking height. Therefore, the pulp molded article MP2 can achieve high transportation efficiency.

Furthermore, according to the above method, drying can be completed in a short time. Therefore, improvement of production efficiency and reduction of energy can be expected.

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

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

In addition, after the dehydration step, drying using an oven is performed, this dried product is humidified as necessary, and when this is subjected to heat press treatment, the height difference of unevenness generated on the surface due to drying is It can be made smaller by subsequent humidification and heat press treatment. Also, the porosity can be reduced by humidification and heat press treatment. However, since the unevenness produced on the surface due to drying using an oven is very large, it cannot be sufficiently reduced by subsequent humidification and heat press treatment. Moreover, it is difficult to sufficiently reduce the porosity even if humidification and heat press treatment are performed after drying.

In the method described with reference to FIGS. 2 to 10, the pulp layer MP1 is dried in the hot press step. That is, in the above method, after the dehydration step, the hot press step is performed without passing through the drying step. The pulp used has an average fiber length within the range described above.

Since the drying process is not performed before the hot pressing process, the surface of the pulp layer MP1 does not have unevenness with a large height difference. In the hot press process, the upper mold 350 and the lower mold 320 prevent deformation of the pulp layer MP1 due to drying. In addition, since the hot pressing step is performed on the pulp layer MP1 having a high water content and an average fiber length within the above range, the movement of the fibers in the in-plane direction in the pulp layer MP1 is moderate. can occur in The pulp layer MP1 can be densified without thickness variations.

Therefore, according to the method described with reference to FIGS. 2 to 10, a pulp molded product MP2 having excellent surface properties can be produced. Specifically, a pulp molded article MP2 having a surface region in which one or more of the arithmetic mean roughness Ra, the maximum height roughness Rz, and the mean length RSm of roughness curve elements is small is obtained. Such a pulp molded product MP2 has excellent cosmetic properties and facilitates formation of a printed layer and a coating layer.

The arithmetic mean roughness Ra is preferably in the range of 2 to 10 μm, more preferably in the range of 2.5 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 15 to 30 μm. The average length RSm of the roughness curvilinear element is preferably in the range of 90 to 300 μm, more preferably in the range of 90 to 150 μm, even more preferably in the range of 90 to 130 μm.

Here, "arithmetic mean roughness Ra", "maximum height roughness Rz" and "mean length RSm of roughness curve element" 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 Corporation (tip radius 2 μm, measuring force 0.75 mN) under the following conditions.
Filter: Gasussian
Cutoff λc: 0.25mm
Cutoff λs: 8 μm
Measurement speed: 0.25mm/s
Number of sections: 5
A plate-like piece is collected from the pulp molded article MP2, measured at any five points, and the average value is calculated.

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

Further, according to the method described with reference to FIGS. 2 to 10, it is possible to produce a pulp molded article 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, according to one example 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 strip-shaped test pieces each having a width of 15 mm and a length of 40 mm were cut out from a plurality of regions positioned within a certain plane of the pulp molded product MP2. Next, the mass of these specimens is measured. Then, for each test piece, the basis weight is calculated from its mass and area (600 mm ² ). The standard deviation is calculated from the grammage thus obtained.

Next, nine test pieces are cut out of the pulp molded article MP2 from a plurality of regions located in another plane in the same manner as described above. These test pieces are also measured for mass and calculated for basis weight and its standard deviation.

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

According to the method described by the present inventors with reference to FIGS. 2 to 10 (hereinafter referred to as the first method), it is , for the following reasons.

A pulp molded product can also be produced, 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. The mold consists of a mold main body having a large number of through-holes and an upper surface recessed in a shape corresponding to the pulp molded product, and a mesh provided on the inner surface of the mold main body along the inner surface. and

Next, the mold is placed so that the opening faces upward. Next, a slurry containing pulp and water is supplied into the cavity of the papermaking mold to fill the inside of the papermaking mold with the slurry. Furthermore, the supply of the slurry into the mold is continued to deposit the pulp on the mesh. The slurry is supplied into the papermaking mold so that the slurry in the papermaking mold is pressurized.

After a sufficient amount of pulp has accumulated on the mesh, the supply of slurry into the mold is stopped. Subsequently, the water remaining in the papermaking mold is discharged from the papermaking mold. For example, air is forced into the mold to expel water remaining in the mold.

Next, the pulp layer is pressed between the paper mold and the upper mold, which is a male 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 upper mold is made to hold the pulp layer by suction, and the upper mold is raised in this state. This separates the pulp layer from the mold.

Next, the upper mold holding the pulp layer by suction is moved to the position of the lower mold, which is the female mold. Subsequently, the upper mold is lowered until the pulp layer contacts the lower mold. The suction is then stopped to release the pulp layer from the upper mold. Thus, the pulp layer is placed on the lower mold.

Next, the pulp layer is sandwiched between an upper mold and a lower mold for hot pressing, and the pulp layer therebetween is pressed. At the same time, the heater is driven to heat the pulp layer. Furthermore, along with this, the pump is driven to suck and remove water and/or steam from the space sandwiched between the upper mold and the lower mold. In the second method, a molded pulp product is obtained as described above.

In the second method, during the period from when the supply of the slurry into the mold is started until the inside of the mold is completely filled with the slurry, the slurry can flow circulating inside the mold. This circulation flow can prevent the pulp from settling. However, in the second method, it is necessary to fill the inside of the papermaking mold with slurry, so that the papermaking mold cannot adopt a structure in which water can be discharged quickly. Therefore, after the inside of the mold is completely filled with the slurry, even if the pressure of the slurry is increased, a circulation flow of the slurry that can prevent the sedimentation of the pulp does not occur, and the sedimentation of the pulp in the slurry inside the mold does not occur. produces

As a result, the amount of pulp deposited on the side walls of the 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 mold, an excessive amount of pulp will be deposited on the bottom of the mold. If the pulp is deposited excessively, variations in the amount of pulp deposited will increase. For example, there can be a large difference in the amount of accumulated pulp between the vicinity of the through-holes provided in the mold main body and the position away from them.

Thus, in the second method, the piled amount of pulp varies greatly. 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. In other words, the variation in the piled amount of pulp cannot be eliminated by movement of the fibers during the hot press treatment. Therefore, according to the second method, it is not possible to produce a molded pulp product with a small standard deviation of basis weight.

On the other hand, in the first method, a mold 240 is placed on top of the cover body 230 and these composites are immersed in the slurry S. As shown in FIG. The depth of the slurry S is far greater than the height of the mold 240 . Therefore, even if pulp sedimentation occurs in the slurry S, there is not a large difference in pulp concentration between the upper portion of the papermaking mold 240 and the lower portion of the papermaking mold 240 . Therefore, according to the first method, the pulp can be deposited substantially uniformly on the mold 240, and the pulp molded product MP2 with a small standard deviation of basis weight can be produced.

The pulp molded article MP2 has an opening and does not expand in the direction away from the opening. Here, the pulp molded article MP2 has an opening and tapers away from the opening. With such a shape, it is possible to reduce the volume of a laminate obtained by stacking a plurality of pulp molded articles MP2.

In the first method, instead of pressing the pulp layer MP1 by 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 then pressed. When pressed, deformation of the elastic occurs. Therefore, sufficient pressure is not applied to the pulp layer MP1, and a molded pulp article having excellent surface properties cannot be obtained.

Even in the second method, if one of the upper mold and the lower mold used in the hot press treatment is made of an elastic body, it is not possible to obtain a molded pulp product with excellent surface properties. Moreover, in this case, as described above, the standard deviation of the basis weight increases.

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 having a three-dimensional shape, unlike a sheet having a two-dimensional shape.

2 to 10 are intended to facilitate understanding of the manufacturing method of the pulp molded product according to one embodiment of the present invention. The method described above can also be implemented 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 papermaking mold 240 and the lower mold 320 are male molds. The upper mold 270 and upper mold 350 may be male molds, and the papermaking mold 240 and lower mold 320 may be female molds. Thus, various modifications are possible for the manufacturing apparatus 1 and the manufacturing method described above.

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

<1> Production of molded pulp products (Example 1)
A pulper was used to prepare a slurry consisting of pulp, paper strength agent and water. The pulp content of the slurry was 0.3% by mass. Pulp A having an average fiber length of 1.6 mm and pulp B having an average fiber length of 0.94 mm were used. The amount of pulp A was 80 parts by mass with respect to 100 parts by mass of the total amount of pulp. Polystrone (registered trademark) 1280 manufactured by Arakawa Chemical Industries, Ltd. was used as the paper strength agent. The ratio of the paper strength agent to the solid content of the slurry was 1% by mass.

Using this slurry, a molded pulp article was produced by the method described with reference to FIGS. Here, the dehydration step was performed so that the moisture content of the pulp layer immediately after dehydration was 65% by mass. The hot press process was performed at a heating temperature of 150° C., a press pressure of 1.2 MPa, and a press time of 5.0 minutes. In the dehydration process and the hot press process, the clearance between the upper mold and the lower mold was set to 1.0 mm so as to obtain a pulp molded article having a wall thickness of 1.0 mm.
As described above, a container was produced as a molded pulp product.

(Example 2)
A pulp molded product was produced in the same manner as in Example 1, except that instead of pulp B, pulp C having an average fiber length of 0.86 mm was used.

(Example 3)
A pulp molded article was produced in the same manner as in Example 1 except that the amount of pulp A was 70 parts by mass with respect to the total amount of pulp of 100 parts by mass, and the ratio of the paper strength enhancer to the solid content of the slurry was 3% by mass. manufactured.

(Example 4)
A pulp molded product was produced in the same manner as in Example 1, except that the amount of pulp A was 70 parts by mass with respect to the total amount of 100 parts by mass of pulp.

(Example 5)
Pulp mold was performed in the same manner as in Example 1 except that the amount of pulp A was 70 parts by mass with respect to the total amount of pulp of 100 parts by mass, and the ratio of the paper strength enhancer to the solid content of the slurry was 0.5% by mass. Moldings were produced.

(Example 6)
A pulp molded article was produced in the same manner as in Example 1, except that the amount of pulp A was 50 parts by mass with respect to the total amount of 100 parts by mass of pulp.

(Example 7)
Pulp mold was performed in the same manner as in Example 1 except that the amount of pulp A was 50 parts by mass with respect to the total amount of pulp of 100 parts by mass, and the ratio of the paper strength enhancer to the solid content of the slurry was 0.5% by mass. Moldings were produced.

(Example 8)
In the dewatering step and the hot press step, the upper mold and the lower mold are separated so that the amount of pulp A is 70 parts by mass with respect to the total amount of 100 parts by mass of pulp, and a pulp molded article having a wall thickness of 0.7 mm is obtained. A pulp molded product was produced in the same manner as in Example 1, except that the clearance was 0.7 mm.

(Example 9)
In the dewatering step and the hot press step, the upper mold and the lower mold are separated so that the amount of pulp A is 70 parts by mass with respect to the total amount of 100 parts by mass of pulp, and a pulp molded article having a wall thickness of 0.7 mm is obtained. A pulp molded product was produced in the same manner as in Example 1, except that the clearance was 0.7 mm. In addition, in this example, compared with Example 8, the density of the pulp molded article was set to be low.

(Example 10)
A pulp molded product was produced in the same manner as in Example 1 except that the amount of pulp A was 50 parts by mass with respect to the total amount of pulp of 100 parts by mass, and the ratio of the paper strength enhancer to the solid content of the slurry was 2% by mass. manufactured.

(Comparative example 1)
A pulp molded product was produced in the same manner as in Example 1, except that pulp A was used as the entire amount of pulp.

(Comparative example 2)
A pulp molded product was produced in the same manner as in Example 1, except that the amount of pulp A was 30 parts by mass with respect to the total amount of pulp of 100 parts by mass.

(Comparative Example 3)
A pulp molded product was produced in the same manner as in Example 1, except that pulp B was used as the entire amount of pulp.

(Comparative Example 4)
A pulp molded product was produced in the same manner as in Example 1 except that the amount of pulp A was 70 parts by mass with respect to the total amount of 100 parts by mass of pulp and no paper strength agent was used.

(Comparative Example 5)
Pulp mold was performed in the same manner as in Example 1 except that the amount of pulp A was 70 parts by mass with respect to the total amount of pulp of 100 parts by mass, and the ratio of the paper strength enhancer to the solid content of the slurry was 0.3% by mass. Moldings were produced.

(Comparative Example 6)
A pulp molded product was produced in the same manner as in Example 1, except that the amount of pulp A was 70 parts by mass with respect to the total amount of 100 parts by mass of pulp. In addition, in this example, the density of the pulp molded article was set to be low.

(Comparative Example 7)
In the dehydration process and the hot press process, the upper mold and the lower mold are separated so that the amount of pulp A is 70 parts by mass with respect to the total amount of 100 parts by mass of pulp, and a pulp molded article having a wall thickness of 0.7 mm is obtained. A pulp molded article was produced in the same manner as in Example 1, except that the clearance was 0.7 mm. In addition, in this example, the density of the pulp molded article was set to be low.

<2> Evaluation For each of the pulp molded articles produced in Examples 1 to 10 and Comparative Examples 1 to 7, various measurements were performed by the methods described above. The results are described in Tables 1 to 3 below.

In Tables 1 to 3, the evaluation of releasability is as follows. If insufficient drying occurs in the pulp molded product MP2, cracks or peeling will occur on the surface of the pulp molded product MP2, or mold release failure such that the pulp molded product MP2 will not be released from the mold will occur. You cannot obtain a molded product.
A: Releasable by blowing air, good surface B: Releasable by blowing air, peeling or cracking on surface C: Unable to release by blowing air In addition, in Tables 1 to 3, "short The "fiber ratio" represents the ratio of fibers having a fiber length of 1 mm or less in the pulp. In Comparative Example 3, the tensile strength, peel strength and density values are not shown because the molded pulp product could not be released from the mold.

As is clear from the comparison between Examples 1 to 10 and Comparative Examples 1 to 7, the ratio of fibers having a fiber length of 1 mm or less in the pulp, the average fiber length, the density, and the nitrogen content are within predetermined ranges. The molded product had high strength and excellent releasability in spite of the small wall thickness. The pulp molded articles of Examples 1 to 10 all have an arithmetic mean roughness Ra within the range of 2 to 10 μm, a maximum height roughness Rz within the range of 10 to 60 μm, and a roughness curve element was in the range of 90 to 300 μm. Moreover, the standard deviation of the basis weight of the molded pulp products of Examples 1 to 10 was within the range of 2 to 30 g/m ² .

DESCRIPTION OF SYMBOLS 1... Manufacturing apparatus, 10... Support body, 20... 1st station, 30... 2nd station, 40... 3rd station, 210... Container, 220... Lifting device, 230... Cover body, 240... Mold, 250... Movement Apparatus 260 Lifting device 270 Upper mold 310 Base 320 Lower mold 330 Moving device 340 Pressing device 350 Upper mold 410 Base 420 Moving device 430 Lifting device 440... Holder, MP1... Pulp layer, MP2... Pulp molded article, S... Slurry.

Claims (11)

The percentage of pulp having a fiber length of 1 mm or less is in the range of 35 to 50%,
The pulp has an average fiber length in the range of 1.2 to 1.5 mm,
having a density in the range of 0.65 to 1.3 g/ ^cm3 ;
A pulp molded article having a nitrogen content in the range of 400 to 2000 μg/g. 2. A molded pulp article according to claim 1, having a thickness in the range of 0.5 to 1 mm. 3. A molded pulp article according to claim 2, having a density in the range of 0.65 to 0.80 g/cm ^<3> and a nitrogen content in the range of 500 to 1000 [mu]g/g. 2. A pulp molded article according to claim 1, having a tensile strength in the range of 30 to 55 kN/m. 2. The molded pulp article according to claim 1, wherein the peel strength is in the range of 0.3 to 0.9 N/mm ^<2> . 2. The molded pulp article of claim 1, wherein the standard deviation of basis weight is in the range of 2 to 30 g/m ^<2> . The molded pulp article according to any one of claims 1 to 6, which is a container. preparing a slurry containing pulp and water and having a fiber length of 1 mm or less in the pulp at a rate of 35 to 50%;
forming a pulp layer by depositing the pulp on a paper mold having a three-dimensional shape;
dewatering the pulp layer to obtain an intermediate molded product;
Heating the undried intermediate molded product to a temperature within the range of 150 to 220° C. while sandwiching the undried intermediate molded product between a male mold and a female mold and applying pressure within the range of 0.4 to 4.5 MPa. A method for producing a pulp molded article containing and. Deposition of the pulp on the mold is
preparing a cover body as a hollow body having an opening;
fixing the mold to the opening;
immersing the mold fixed to the opening in the slurry;
9. The method of manufacturing a pulp molded product according to claim 8, further comprising depressurizing a space surrounded by the cover body and the mold immersed in the slurry. 10. The method for producing a molded pulp product according to claim 9, wherein the mold is immersed in the slurry so that the mold is located above the cover body. Pressurization and heating of the undried intermediate molded product sandwiched between the male mold and the female mold are performed at a pressure within the range of 0.4 to 2.0 MPa and within the range of 150 to 200° C., respectively. 11. The method for producing a pulp molded product according to any one of claims 8 to 10, wherein the method is carried out at a temperature of

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