JP7528636B2 - Pulp Molding - Google Patents

Description

The present invention relates to a pulp molded body.

In recent years, in light of growing awareness of environmental issues related to the increase in waste, etc., pulp molded bodies, which are made by using pulp as the raw material and molding the pulp slurry using a wet suction molding method, have been attracting attention as a variety of packaging materials to replace plastic and metal containers. Pulp molded bodies contribute to resource and energy conservation, and are highly recyclable when disposed of, making them suitable for incineration even if they are disposed of, making them a packaging material that contributes to environmental conservation.

Patent Document 1 describes a pulp mold packaging material in which 50-100% (bone dry) of the pulp components that make up the pulp mold is deinked waste paper pulp with a Hunter brightness of 65-85%, and the remaining pulp is bleached pulp.

Japanese Unexamined Patent Publication No. 7-119100

Depending on the application, a pulp molded article is required to have a hinge portion (folded portion, bent portion) such as a lid portion, but there has been a problem in that the hinge portion can be damaged by repeated use.
The pulp molded product described in Patent Document 1 is intended to obtain a pulp molded product having a vivid whiteness and color tone, but does not have sufficient flex resistance.
An object of the present invention is to provide a pulp molded article which has a hinge portion and is excellent in folding resistance even with repeated use.

As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a specific mixed pulp as the pulp constituting the pulp molded article.
That is, the present invention relates to the following <1> to <15>.
<1> An openable and closable pulp molded body having an integrally molded hinge portion, the pulp raw material of the pulp molded body containing 50% by mass or more of non-wood pulp.
<2> The pulp molded product according to <1>, wherein the non-wood pulp is at least one selected from the group consisting of bagasse and bamboo.
<3> The pulp molded body according to <1> or <2>, wherein the pulp raw material contains non-wood pulp and wood pulp, and the content ratio of the wood pulp and the non-wood pulp in the pulp raw material (wood pulp/non-wood pulp) is 5/95 or more and 50/50 or less.
<4> The pulp molded body according to any one of <1> to <3>, wherein the width of the hinge portion is 50% or more and 100% or less of the maximum width of the movable member of the openable/closable pulp molded body.
<5> The pulp molded article according to any one of <1> to <4>, wherein the thickness of the pulp molded article excluding the hinge portion is 0.4 mm or more and 3 mm or less.
<6> The pulp molded product according to any one of <1> to <5>, wherein the hinge portion is formed by providing a groove on the upper surface or the lower surface, by providing a groove on the upper surface and the lower surface, by providing a ruled line, or by using any of these in combination with a through hole provided in the hinge portion.
<7> The pulp molded article according to any one of <1> to <6>, wherein the Canadian standard freeness of the pulp constituting the pulp molded article is 100 mL or more and 700 mL or less.
<8> The pulp molded article according to any one of <1> to <7>, wherein the density of the pulp molded article is 0.45 g/ ^cm3 or more and 1.0 g/ ^cm3 or less.
<9> The pulp molded article according to any one of <1> to <8>, wherein the pulp molded article has a single layer structure.
<10> A secondary processed pulp molded article obtained by surface-treating the pulp molded article according to any one of <1> to <9>.
<11> The secondary processed pulp molded article according to <10>, wherein the surface treatment is at least one of a direct printing method, a lamination method, a transfer method, and a vapor deposition method.
<12> The secondary processed pulp molded product according to <10> or <11>, wherein the surface treatment is at least one of a vacuum lamination method and a hot stamp transfer method.
<13> A method for producing a pulp molded body according to any one of <1> to <9>, comprising: a pulp suspension preparation step of preparing a pulp suspension; a papermaking step of papermaking pulp from the pulp suspension through a papermaking mold; and a hot pressing step of hot pressing a molded intermediate obtained after the papermaking step, while heating the molded intermediate, using a first press die and a second press die positioned in the opposite direction to the first press die.
<14> The method for producing a pulp molded product according to <13>, wherein the pressure in the hot pressing step is 0.1 MPa or more and 3.0 MPa or less.
<15> The method for producing a pulp molded article according to <13> or <14>, wherein the temperature in the hot pressing step is 130° C. or higher and 280° C. or lower.

The present invention provides a pulp molded product that has a hinge portion and is highly resistant to folding even with repeated use.

FIG. 1 is a cross-sectional view of a hinge portion of a pulp molded body. FIG. 2A is a front perspective view and FIG. 2B is a rear perspective view of an example of a pulp molded body.

[Pulp molded body]
The pulp molded article of the present invention is an openable/closable pulp molded article having an integrally molded hinge portion, and the pulp raw material of the pulp molded article contains 50% by mass or more of non-wood pulp.
According to the present invention, a pulp molded article having a hinge portion can be obtained that has excellent folding resistance even when the hinge portion is repeatedly opened and closed.
Although the detailed reasons why the above effects are obtained are unclear, some of the reasons are thought to be as follows.
It is believed that the non-wood pulp used as the pulp raw material contains parenchyma cells, which improves the folding resistance. The inclusion of wood pulp improves the smoothness. Therefore, it is believed that by using non-wood pulp and wood pulp as the pulp raw material and by including 50% by mass or more of non-wood pulp, a pulp molded body having excellent folding resistance and excellent smoothness was obtained.

<Raw pulp>
In the present invention, the raw material pulp contains non-wood pulp in an amount of 50% by mass or more.
Non-wood pulp is a fiber obtained from the bark, stems, leaves, leaf sheaths, etc. of plants. Specific examples include pulp obtained from cotton linters, cotton, linen, hemp, ramie, straw, esparto, Manila hemp, sisal, jute, flax, kenaf, bamboo, bagasse, ganpi, mitsumata, kozo, and mulberry.
From the viewpoint of further improving the folding resistance of the pulp molded body, the non-wood pulp preferably contains at least one selected from bagasse and bamboo, more preferably at least one selected from bagasse and bamboo, and even more preferably bagasse.
From the viewpoint of further improving the folding resistance and surface smoothness of the pulp molded body, the content of non-wood pulp in the raw material pulp is 50% by mass or more, preferably 55% by mass or more, and may be 100% by mass, but is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and even more preferably 75% by mass or less.

From the viewpoint of surface smoothness, the raw material pulp preferably contains wood pulp in addition to the above-mentioned non-wood pulp.
Examples of wood pulp include wood pulp generally used for papermaking purposes, and are classified according to their preparation method into chemical pulps such as kraft pulp (KP), sulfite pulp (SP), soda pulp (AP), etc.; semi-chemical pulps such as semi-chemical pulp (SCP) and chemi-ground wood pulp (CGP); mechanical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP, BCTMP), refiner ground wood pulp (RGP), etc.; recycled paper pulp, etc.
Examples of wood pulp include coniferous pulp and hardwood pulp, depending on the raw material. Examples of coniferous pulp include pulp obtained from the fir and pine genus. Examples of hardwood pulp include pulp obtained from the acacia, eucalyptus, beech, and poplar genus.
Among these, softwood kraft pulp (NKP) and hardwood kraft pulp (LKP) are more preferable as wood pulp.

In the present invention, it is preferable that the wood pulp contains hardwood pulp. It is more preferable that the hardwood pulp contains at least one of the wood pulps of the Acacia, Eucalyptus and Beech genera. In the present invention, it is preferable that the raw material pulp contains wood pulp obtained from at least one of the woods of the Acacia, Eucalyptus and Beech genera. For example, wood pulp obtained from woods of the Acacia and Eucalyptus genera may be used in combination, but it is preferable to contain only wood pulp of one of the genera. By containing hardwood pulp as the wood pulp, a pulp molded product with excellent smoothness can be obtained. In addition, by containing at least one of the wood pulps of the Acacia, Eucalyptus and Beech genera, a pulp molded product with even better surface smoothness can be obtained. Among these, from the viewpoints of surface smoothness and oil resistance, it is more preferable that the hardwood pulp is at least one selected from the Acacia and Eucalyptus genera, and even more preferable that it is wood pulp from the Acacia genus.

The content of hardwood pulp (preferably wood pulp belonging to at least one of the genera Acacia, Eucalyptus and Beech) in the raw material pulp may be 0% by mass, from the viewpoint of the folding resistance and surface smoothness of the pulp molded body, and is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 25% by mass or more, and 50% by mass or less.

In the present invention, the raw material pulp may contain softwood pulp, and the softwood pulp is preferably softwood kraft pulp. By containing softwood pulp, a pulp molded article having superior strength can be obtained.
As the coniferous wood pulp, coniferous wood pulp of the genus Pinus is preferred, and radiata pine is more preferred.
When the raw material pulp contains softwood pulp, the content is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 5 mass% or more, and preferably 30 mass% or less, more preferably 20 mass% or less, even more preferably 15 mass% or less.

The ratio of wood pulp to non-wood pulp in the raw pulp (mass ratio, wood pulp/non-wood pulp) may be 0/100, from the viewpoint of further improving the folding resistance and surface smoothness of the pulp molded body, and is preferably 5/95 or more, more preferably 10/90 or more, even more preferably 15/85 or more, even more preferably 25/75 or more, and is 50/50 or less.

In the present invention, as described above, it is preferable to use a mixed pulp of wood pulp and non-wood pulp as the pulp raw material. Here, waste paper such as waste paper and corrugated waste paper may be used as the pulp raw material, but if the waste paper content is high, there is a problem that the fibers of the waste paper are frayed and deformed, resulting in poor surface smoothness and surface design. From the viewpoint of improving the surface smoothness and surface design of the pulp molded body, the content of waste paper in the raw pulp is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 3% by mass or less, and it is even more preferable that no waste paper is used.

In the present invention, the Canadian standard freeness of the mixed pulp is preferably 100 mL or more, more preferably 200 mL or more, even more preferably 300 mL or more, and even more preferably 350 mL or more, from the viewpoint of productivity of the pulp raw material and papermaking properties during production of the pulp molded body, and is preferably 700 mL or less, more preferably 600 mL or less, and even more preferably 550 mL or less, from the viewpoint of surface smoothness.
The degree of beating may be adjusted so that the Canadian standard freeness falls within the above range.
Canadian standard freeness is measured in accordance with JIS P 8121-2:2012.

<Other ingredients>
The pulp molded body is formed using the above-mentioned pulp as a main raw material. The pulp molded body may be formed from 100% pulp, but other materials such as various internal additives can be added in addition to the pulp.
Examples of internal additives include inorganic substances such as talc and kaolin, inorganic fibers such as glass fiber and carbon fiber, powders or fibers of synthetic resins such as polyolefin, polysaccharides such as carboxymethylcellulose, sizing agents, wet strength agents, oil-resistant agents, retention agents, drainage improvers, bulking agents, aluminum sulfate, pH adjusters, pitch control agents, slime control agents, colorants such as pigments, etc. Among these, it is preferable to contain a sizing agent.

Examples of sizing agents include rosin-based sizing agents (e.g., acidic rosin-based sizing agents, neutral rosin-based sizing agents), alkyl ketene dimers, alkenyl succinic anhydrides, and styrene-containing polymers such as styrene-(meth)acrylate copolymers, with alkyl ketene dimers being preferred.

Examples of the wet strength enhancer for internal addition include polyamide polyamine-epichlorohydrin resin, dialdehyde starch, urea formaldehyde resin, melamine-formaldehyde, polyacrylamide, methylolated polyacrylamide, polyethyleneimine, and the like.
Examples of water repellents include wax emulsions, metal soaps (alkali salts of sodium, potassium, zinc, lithium, magnesium, etc.), fatty acid chromium complex salts (myristic complex salts, stearic acid chromic chloride complex salts, etc.), zirconium water repellents, silicone emulsions, etc.
Since the pulp molded product of the present invention contains non-wood pulp and can improve oil resistance and water resistance using only the pulp raw material, sufficient oil resistance and water resistance can be obtained even if the amount of wet strength agent, water repellent agent, and water resistance agent added is reduced or not added. However, this does not exclude the addition of a wet strength agent, water repellent agent, or oil resistance agent in order to obtain higher oil resistance and water resistance.

<Hinge>
The pulp molded body of the present invention has a hinge portion. The hinge portion means a portion that connects a portion of the pulp molded body that can be opened and closed freely but cannot move up, down, left, or right. In other words, the hinge portion refers to a folding portion that allows the pulp molded body to be opened and closed by folding the pulp molded body. The hinge portion is preferably a linear portion. In the present invention, the pulp molded body is preferably molded as an integral body, and the folding portion of the integrally molded pulp molded body is preferably referred to as the hinge portion.

The hinge portion of the pulp molded article may be provided by any method, but is preferably provided by any of the following three methods.
(i) Providing a groove on the upper or lower surface of the hinge portion; (ii) Providing grooves on the upper and lower surfaces of the hinge portion; (iii) Providing lines on the hinge portion. In addition to (i) to (iii), these may be used in combination with a through hole provided in the hinge portion.
The hinge portion will be described in detail below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a hinge portion. FIGS. 1(a1) and (a2) show an embodiment in which a groove is provided on the upper or lower surface of the hinge portion. The groove may be provided after obtaining a pulp molded body, or may be provided so as to reduce the thickness of the hinge portion when manufacturing the pulp molded body. The groove is not limited to a V-shape as shown in FIG. 1(a1), and may be provided in a trapezoidal shape so that the thickness of a part of the hinge portion is reduced as shown in FIG. 1(a2). The groove is preferably provided after manufacturing the pulp molded body. At this time, the angle, depth, and shape of the groove are adjusted to balance the folding resistance and ease of opening and closing. As a method for providing a groove after manufacturing the molded body, a method of forming a groove by cutting (removing) or pressing the molded body (the pressed part has a high density) is exemplified.
In addition, Fig. 1 (b1) and (b2) show an embodiment in which grooves are provided on the upper and lower surfaces of the hinge portion. The grooves may be provided after the pulp molded body is obtained, or the hinge portion may be provided during the manufacture of the pulp molded body. The grooves are not limited to the V-shape shown in Fig. 1 (b1), and may be provided in a trapezoidal shape so that the thickness of a portion of the hinge portion is thin, as shown in Fig. 1 (b2). It is preferable that the grooves are provided after the pulp molded body is manufactured.
In the above cases (i) and (ii), from the viewpoint of ease of opening and closing, the thickness of the thinnest part of the groove is preferably 90% or less, more preferably 80% or less, even more preferably 70% or less, and particularly preferably 60% or less of the thickness of the other parts, and from the viewpoint of folding resistance, it is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more.
In the above-mentioned Fig. 1 (a1), (a2), (b1) and (b2), a groove is provided to form a thin portion. In contrast, in Fig. 1 (c1) and (c2), the thickness of the hinge portion is constant, but the hinge portion is configured by providing a ruled line (a folding line formed by at least one selected from a convex portion and a concave portion) in the hinge portion. As shown in Fig. 1 (c1), a ruled line may be provided with the center of two convex portions as the folding line, or as shown in Fig. 1 (c2), a ruled line may be provided by providing a concave portion.
Furthermore, these hinge portions may further have through holes, and the total length of the through holes is preferably 70% or less, more preferably 50% or less, and even more preferably 30% or less of the length of the hinge portion from the viewpoint of folding resistance.

The shape of the hinge portion and the opening/closing direction are not particularly limited. For example, in the case of a hinge portion as shown in Fig. 1 (a1) and (a2), it may be opened and closed in an upward direction, i.e., bent in a direction in which the slopes of the V shape approach each other, or conversely, it may be bent in a direction in which the V shape widens. Although there are no particular limitations, from the viewpoint of improving folding resistance, it is preferable to bend in a direction in which the V shape widens.

From the viewpoint of further improving folding resistance, the width of the hinge part is preferably 50% or more of the maximum width of the movable member of the openable/closable pulp molded body, more preferably 60% or more, and even more preferably 70% or more. Also, in consideration of ease of opening and closing, it is preferable to make the width of the hinge part narrower than the maximum width of the movable member, and the width of the hinge part is 100% or less of the maximum width of the movable member, preferably 95% or less, more preferably 90% or less, and even more preferably 80% or less.
In FIG. 2, W _H denotes the width of the hinge portion, W _M denotes the maximum width of the movable member, and W _H is 80% of W _M.

<Characteristics of pulp mold>
In the present invention, the thickness of the pulp molded body is not particularly limited, but from the standpoints of durability, shape stability, ease of manufacture, etc., the thickness other than the hinge portion is preferably 0.4 mm or more, more preferably 0.6 mm or more, even more preferably 0.8 mm or more, and preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1.5 mm or less.
The thickness of the pulp molded body can be measured in accordance with JIS P 8118:2014.

In the present invention, from the viewpoints of surface smoothness and folding endurance, the density of the pulp molded body is preferably 0.45 g/ ^cm3 or more, more preferably 0.50 g/ ^cm3 or more, even more preferably 0.55 g/ ^cm3 or more, and is preferably 1.0 g/ ^cm3 or less, more preferably 0.90 g/ ^cm3 or less, even more preferably 0.80 g/ ^cm3 or less, and still more preferably 0.70 g/ ^cm3 or less.
The density of the pulp molded body can be measured according to JIS P 8118:2014. JIS P 8118:2014 is a method used for paper and paperboard, and in the present invention, the size of the sample may not be as specified. In such a case, the sample size is appropriately adjusted for measurement. The basis weight is measured according to JIS P 8124:2011, and the adjustment of the sample size is also the same as above. The flat part of the molded body is used for the measurement.

The pulp molded product of the present invention may be made into a multi-layer structure by performing the papermaking process described below multiple times or by hot pressing multiple molded intermediates in a hot pressing process, but from the viewpoint of superior surface smoothness and folding resistance, a single-layer structure is preferred.

<Secondary processed pulp molded body>
The pulp molded article of the present invention may be surface-treated to form a secondary processed pulp molded article. In the present invention, the secondary processed pulp molded article is a pulp molded article that has been surface-treated. The pulp molded article of the present invention has an advantage that it is easy to apply surface treatment to the pulp molded article because of its excellent surface smoothness.
The method of secondary processing is not particularly limited as long as it is a method capable of surface processing of the pulp mold, but it is preferable that the secondary processed pulp mold body is surface-processed by at least one surface processing method of direct printing, lamination, transfer, and vapor deposition, more preferably at least one surface processing method of direct printing, lamination, and transfer, and even more preferably at least one surface processing method of lamination and transfer.
However, the method is not limited to these, and a pre-printed sticker or the like may be affixed.

(Direct printing method)
The direct printing method involves directly applying ink or resin to the surface of a pulp molded article for the purpose of imparting color, design, pattern, etc., or imparting waterproofness, moisture resistance, etc., and examples of the direct printing method include methods of surface treating the pulp molded article by impregnation, printing, etc.
The printing may be performed by any printing means such as letterpress printing using a rubber plate or a resin plate, silk screen printing, pad printing, electrostatic printing, thermal transfer printing, etc. By printing, patterns, letters, etc. can be provided on the surface of the obtained pulp molded product.
Alternatively, the resin may be directly applied to the pulp molded body by brushing, spraying, etc. Among these, spray application is preferred from the viewpoint of uniformly applying the resin, etc. The spray application may be performed by any of air spray, airless spray, electrostatic spray, etc.
To impart waterproof and moisture-proof properties to the surface of a pulp molded body, a water-based emulsion paint containing a resin such as an acrylic resin, a styrene resin, a urethane resin, a melamine resin, an olefin resin, an epoxy resin, a polyvinyl alcohol resin, or a vinylidene chloride resin as a solid component, or a water-based paint or an organic solvent-based paint of these resins may be applied.

(Lamination method)
The lamination is preferably performed by covering with a resin film, and examples of the resin film used include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon, polyvinyl resins such as polyvinyl chloride, styrene resins such as polystyrene, thermoplastic resin films such as ethylene-vinyl alcohol copolymers and polyacrylonitrile, and biodegradable resin films such as modified polyethylene terephthalate and aliphatic polyester. Considering the manufacturing cost and moldability, polyolefin resins are preferred, and from the viewpoint of environmentally friendly disposal, biodegradable resin films are preferred. The lamination may be formed by laminating two or more of these resin films.
The thickness of the resin film is not particularly limited, but is preferably 10 μm or more and 300 μm or less.

By laminating the above-mentioned resin film, functions such as water resistance, oil resistance, and gas barrier properties can be improved or imparted.
Furthermore, a pattern may be printed on the resin film to be laminated in advance, or coloring pigments, fine particles (pearl pigments, holograms, etc.), luminous dyes, luminous pigments, etc. may be added. By using such resin films, it is possible to impart gloss and design properties to the surface of the pulp molded article.

The lamination may be performed on the pulp molded article by a known method such as extrusion lamination, heat lamination, dry lamination, or wet lamination.
Among these, heat lamination is preferred, vacuum lamination and vacuum pressing are preferred, and vacuum lamination is more preferred.
Vacuum lamination may be performed by deforming a sheet placed on top of the substrate by suction from the substrate side (pulp mold side), or by dividing upper and lower chambers, which have been evacuated in advance, into two by a resin film, and applying compressed air to the upper chamber equipped with a resin film heating device, thereby laminating the substrate (pulp molded product) placed in the lower chamber.
In addition, vacuum pressing involves sucking silicone rubber or the like into the substrate (pulp molded body) by vacuum from the side, and in some cases applying compressed air from above, to deform the material into the shape of the substrate, and the resin film sandwiched between the silicone rubber or the like and the substrate is laminated to the substrate by the pressure of the silicone rubber.
Alternatively, a resin film may be preformed in a mold to match the shape of the pulp molded article, and then laminated to the pulp molded article.

The lamination process may be carried out by a conventionally known method, and an example of a vacuum lamination device is a TOM molding machine (manufactured by Fuse Vacuum Co., Ltd.).
The conditions for lamination, such as temperature and pressure, may be appropriately selected depending on the material and thickness of the resin film to be laminated, the shape of the substrate, the presence or absence of an adhesive, etc., but for example, lamination is performed at a heater heating temperature of 80 to 200°C.

During lamination, an adhesive may or may not be applied between the resin film and the pulp molded body. The adhesive may be a polyurethane adhesive, a polyacrylic adhesive, a polyester adhesive, an epoxy adhesive, a polyvinyl acetate adhesive, a cellulose adhesive, or any other adhesive for lamination. When an adhesive is applied, a pigment having coloring properties, a pearl pigment, fine particles (such as holograms), a luminous pigment, a luminous dye, etc. may be added to the adhesive.

(Transfer Method)
Examples of the transfer method include hot stamp transfer, in-mold transfer, hydraulic transfer, and the like, and may be either a dry transfer method or a wet transfer method. In the in-mold transfer method, a preforming step may be added.
Among the transfer methods, the hot stamp transfer method (hereinafter, simply referred to as the "hot stamp method") is preferred. The hot stamp method is a method in which a film on which metal, called "foil," is vapor-deposited or a pigment is applied is used, and the film is thermally transferred to a substrate via a thermal adhesive layer provided on the surface of the foil. The foil used in the hot stamp method is laminated in the order of a base film having releasability (for example, a biaxially oriented polyester film), a peeling layer (protective layer), a pattern layer/vapor deposition layer, and a thermal adhesive layer, and a release layer is provided between the base film and the protective layer as necessary. Examples of the hot stamp method include (i) the up-down method and (ii) the roll transfer method, and the principle is the same that the pattern layer/vapor deposition layer in the part where heat pressure is present is transferred to the substrate (pulp molded body). In the up-down method, a template with a built-in heater is pressed against the substrate from the base film side, and the pattern layer/vapor deposition layer is transferred to the substrate via the thermal adhesive layer. Similarly, in the roll transfer method, the pattern layer/vapor deposition layer is transferred to the substrate by pressing a heated roller against the base film side. It is also possible to subject the base film to grinding, gloss treatment, unevenness processing, etc., so as to impart a shape (to give unevenness) to the design layer and vapor deposition layer at the time of transfer.

(Vapor deposition)
The vapor deposition may be any vapor deposition method known in the art, and may be either physical vapor deposition or chemical vapor deposition, but is not particularly limited. Vacuum vapor deposition, which is a form of physical vapor deposition, is preferred for the purpose of imparting a metallic luster to the pulp molded article.
As the deposition material, it is preferable to use metals such as aluminum, chromium, zinc, gold, silver, platinum, and nickel, and oxides and fluorides such as SiO ₂ , TiO ₂ , ZrO ₂ , and MgF ₂ .
The thickness of the vapor-deposited layer is not particularly limited, but is preferably 0.1 μm or more.

[Method for producing pulp molded body]
The method for producing the pulp molded article is not particularly limited, but it is preferable to produce the article by a method including the following steps 1 to 3 in this order.
Step 1: A pulp suspension preparation step for preparing a pulp suspension Step 2: A papermaking step for papermaking pulp from the pulp suspension through a papermaking mold Step 3: A hot pressing step for hot pressing the mold intermediate obtained after the papermaking step with a first press die and a second press die positioned in the opposite direction to the first press die while heating In step 1, a pulp suspension (pulp slurry) is prepared by adding pulp raw materials and other additives such as a sizing agent. The concentration of the suspension (slurry concentration) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and is preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, from the viewpoints of surface smoothness, dimensional stability, and productivity.

Step 2 is a papermaking step in which pulp is papered from a pulp suspension through a papermaking mold.
A molding die, such as a wire mesh die with a vacuum-drawn water-permeable structure, is immersed in the pulp suspension, and the pulp suspension is sucked into the molding die to expel water, while at the same time the pulp fibers are stacked and adsorbed onto the die to form a three-dimensional wet paper that is symmetrical to the die. The molding die is then lifted out of the pulp suspension, and the water-absorbed three-dimensional wet paper is subjected to suction dehydration or pressure dehydration.
In this case, while continuing to apply vacuum suction to the molding die with the pulp laminated and adsorbed to its surface, a release device with vacuum suction is brought close to the pulp adsorption surface, and the pulp mold intermediate is dehydrated by compressed vacuum suction. After that, the vacuum pressure of the molding die is returned to normal pressure, and the release device is pulled back with the pulp mold intermediate still adsorbed to the release die, thereby releasing it.

Step 3 is a hot pressing step in which the mold intermediate obtained after the papermaking step is hot pressed with a first press die and a second press die positioned in the opposite direction to the first press die while being heated.
In step 3, the dehydrated pulp mold intermediate obtained in step 2 is transferred to a first press die for hot pressing, which is made of, for example, a porous die. The pulp mold intermediate transferred to the first press die is heated and pressurized by the first press die and a second press die for hot pressing, which is positioned in the opposite direction to the first press die and engages with the first press die, to obtain a predetermined pulp molded product.
It is preferable that at least one of the first press die and the second press die for hot pressing has an electric heater built therein, thereby heating at least one of the first press die and the second press die. Also, the entire die including the first press die and the second press die may be housed in a furnace into which hot air is introduced, so that hot air passes through the inside of the die.

In step 3 (hot pressing step), the pressure during pressing with the first press die and the second press die is preferably 0.1 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.4 MPa or more, and even more preferably 0.6 MPa or more, from the viewpoint of obtaining a pulp molded body with excellent surface smoothness, and is preferably 3.0 MPa or less, more preferably 2.0 MPa or less, and even more preferably 1.5 MPa or less, from the viewpoint of power consumption and equipment load.

In step 3 (hot pressing step), the temperature during hot pressing is preferably 130°C or higher, more preferably 150°C or higher, and even more preferably 170°C or higher, from the viewpoints of obtaining a pulp molded body with excellent surface smoothness, and is preferably 280°C or lower, more preferably 250°C or lower, and even more preferably 230°C or lower, from the viewpoints of power consumption, device load, and suppression of discoloration.

The pulp molded article obtained as described above may be further processed by cutting off unnecessary portions and, if necessary, drilling holes.
The pulp molded article of this embodiment is a molded article with excellent smoothness called a fine mold, and taking advantage of its excellent folding resistance and surface smoothness, it can be suitably used as a packaging material for foods, medical products, cosmetics, electronic parts, etc. In addition, since it has excellent surface smoothness and is easy to process the surface such as printing, coating, lamination, etc., it can be widely used not only for the above-mentioned applications but also for small item containers, cup lids, ornaments, etc.

The features of the present invention are explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. In the examples and comparative examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified.

Example 1
15 parts by mass of acacia bleached virgin pulp (LBKP), which is a hardwood pulp, and 85 parts by mass of bagasse bleached virgin pulp, which is a non-wood pulp, were mixed and beaten to a Canadian standard freeness (CSF) of 510 mL to obtain a pulp slurry of 2% by mass. AKD (alkyl ketene dimer, manufactured by Seiko PMC Co., Ltd.) was added as a sizing agent in terms of solid content to 100 parts by mass of pulp (solid content) of this pulp slurry, and the slurry concentration was adjusted to 0.7% by mass after stirring. In order to remove agglomerates, the slurry was filtered, and a papermaking mold with a metal mesh attached on the surface was immersed in the filtered slurry, and vacuum suction was applied from inside the mold to suck the pulp slurry onto the mesh to form a three-dimensional wet paper. The wet paper was transferred to a dewatering mold and dewatered under pressure at 0.7 MPa, then transferred to a mold heated to 180°C and further dried under pressure at 1.2 MPa, the excess was cut off, and the top surface of the hinge (the outside when opening and closing) was cut with a blade to form a groove (Figure 1(a1)) (the thickness of the thinnest part was 50% of that before cutting), to obtain a container as shown in Figure 2. Figure 2 shows (A) a front perspective view and (B) a rear perspective view of the container, which is a pulp molded product with the lid open.
The width (W _H ) of the hinge portion was 75% of the maximum width (W _M ) of the openable/closable portion, the thickness of the container excluding the groove of the hinge portion was 1 mm, and the density was approximately 0.60 g/cm ³ .

Example 2
A container was obtained in the same manner as in Example 1, except that the amounts of bleached acacia virgin pulp and bleached bagasse virgin pulp were changed to 30 parts by mass and 70 parts by mass, respectively.

Example 3
A container was obtained in the same manner as in Example 1, except that the amounts of bleached acacia virgin pulp and bleached bagasse virgin pulp were changed to 45 parts by mass and 55 parts by mass, respectively.

Example 4
A container was obtained in the same manner as in Example 2, except that the bleached virgin bagasse pulp was changed to unbleached bamboo pulp.

Example 5
A container was obtained in the same manner as in Example 2, except that the mixture was beaten to a Canadian Standard Freeness (CSF) of 400 mL.

Example 6
A container was obtained in the same manner as in Example 1, except that the pulp was made of only bleached bagasse virgin pulp and was beaten to a Canadian standard freeness (CSF) of 400 mL.

Example 7
A container was obtained in the same manner as in Example 2, except that the width of the hinge portion was changed to 55% of the maximum width of the openable and closable portion.

Example 8
A container was obtained in the same manner as in Example 2, except that the width of the hinge portion was changed to 95% of the maximum width of the openable and closable portion.

Example 9
A container was obtained in the same manner as in Example 1 up until just before the groove of the hinge portion was formed. A polypropylene film (manufactured by Toray Industries, Inc., film thickness = 50 μm) was laminated by vacuum lamination to the entire inner surface (including the hinge portion) of the obtained container when opening and closing, to obtain a secondary processed pulp molded product. The lower surface of the hinge portion (the surface opposite to the laminated surface, the outer side when opening and closing) was cut with a blade to form a groove (FIG. 1(a1)) (the thickness of the thinnest part was 50% of that before lamination, excluding the laminated portion), to obtain a container.
After lamination, the container has excellent surface gloss and improved design.

Example 10
A container was obtained in the same manner as in Example 1 up until just before the groove of the hinge portion was formed. A film that had been printed on the inside of a polypropylene film (the surface that contacts the outside surface when opening and closing the container) was laminated to the entire outside surface (including the hinge portion) of the obtained container when opening and closing using a vacuum lamination method, to obtain a secondary processed pulp molded product. The bottom surface of the hinge portion (laminated surface, the outside when opening and closing) was cut with a blade to form a groove (FIG. 1(a1)) (the thickness of the thinnest part was 50% of that before lamination), and a container was obtained.
The printed pattern is clear, and the decorativeness has been significantly improved. In addition, by printing on the inside of the resin film, the surface performance of the printed area has also been improved in terms of scratch resistance and stain resistance.

Comparative Example 1
A container was obtained in the same manner as in Example 1, except that the amounts of bleached acacia virgin pulp and bleached bagasse virgin pulp were changed to 55 parts by mass and 45 parts by mass, respectively.

Comparative Example 2
A container was obtained in the same manner as in Example 1, except that the amounts of bleached acacia virgin pulp and bleached bagasse virgin pulp were changed to 70 parts by mass and 30 parts by mass, respectively.

Comparative Example 3
A container was obtained in the same manner as in Example 1, except that the amounts of acacia bleached virgin pulp and bagasse bleached virgin pulp were changed to 85 parts by mass and 15 parts by mass, respectively.

Comparative Example 4
A container was obtained in the same manner as in Comparative Example 3, except that the mixture was beaten to a Canadian Standard Freeness (CSF) of 620 mL.

Comparative Example 5
A container was obtained in the same manner as in Example 1, except that the pulp was made of only bleached acacia virgin pulp and was beaten to a Canadian standard freeness (CSF) of 510 mL.

<Evaluation of smoothness (surface smoothness)>
Ten containers from each of the Examples and Comparative Examples were prepared and left to stand for 24 hours in an environment conforming to ISO 187:1990 (temperature 23±1° C., relative humidity 50±2%) to adjust the temperature and humidity.
The surface of the container was touched in the above environment and evaluated as follows. The evaluation was performed by five trained panelists.
4: Very smooth and silky 3: The surface has a slight fiber presence, but is smooth 2: The surface has a lot of fiber, but feels smooth 1: The surface has a very high fiber presence, or the surface feels rough.
The values in the table are the average values of the results of 50 items in total, with each person evaluating 10 items, and are rounded off to the first decimal place.

<Folding resistance (opening and closing damage)>
Three containers were prepared for each of the Examples and Comparative Examples, and were left to stand in an environment conforming to ISO 187:1990 (temperature 23±1° C., relative humidity 50±2%) for 24 hours to adjust the temperature and humidity.
The container was opened and closed 500 times in the above environment (opened at 180° and closed), and evaluated as follows. When different results were obtained, the average of the three values (rounded off to the nearest whole number) was used as the evaluation result of folding endurance.
5: The hinge portion is hardly damaged.
4: Only slight damage was observed in the hinge portion.
3: There is damage to the hinge, but it does not affect practical use.
2: The hinge is damaged to a level that makes it unusable.
1: There is significant damage to the hinge or the hinge has broken off midway, causing the container to separate into two.

<Thickness and density>
Measurements were performed in accordance with JIS P 8118:2014.

The pulp molded product of the present invention has excellent folding resistance and is expected to be used in a variety of applications, including as a packaging material for food, medical products, cosmetics, etc.

Claims (15)

The molded pulp body has an integrally molded hinge and is capable of being opened and closed.
The pulp raw material of the pulp molded body contains non-wood pulp and wood pulp,
The pulp raw material of the pulp molded body contains 50% by mass or more of non-wood pulp,
The pulp raw material of the pulp molded body contains 5% by mass or more and 50% by mass or less of at least one hardwood pulp selected from the Acacia genus, the Eucalyptus genus, and the Beech genus ;
The non-wood pulp is at least one selected from the group consisting of bagasse and bamboo;
Pulp molded body. 2. The pulp molded body according to claim 1 , wherein the width of the hinge portion is 50% or more and 100% or less of the maximum width of the movable member of the openable and closable pulp molded body. 3. The pulp molded article according to claim 1 , wherein the thickness of the pulp molded article excluding the hinge portion is 0.4 mm or more and 3 mm or less. The pulp molded product according to any one of claims 1 to 3, wherein the hinge portion is formed by providing a groove on the upper or lower surface, by providing a groove on the upper and lower surfaces, by providing a line, or by using these in combination with a through hole provided in the hinge portion. 5. The pulp molded article according to claim 1 , wherein the pulp constituting the pulp molded article has a Canadian standard freeness of 100 mL or more and 700 mL or less. 6. The pulp molded article according to claim 1 , wherein the pulp constituting the pulp molded article has a Canadian standard freeness of 350 mL or more and 600 mL or less. 7. The pulp molded article according to claim 1 , wherein the content ratio of wood pulp to non-wood pulp in the pulp raw material (wood pulp/non-wood pulp) is 25/75 or more and 50/50 or less. The pulp molded article according to any one of claims 1 to 7 , wherein the density of the pulp molded article is 0.45 g/ ^cm3 or more and 1.0 g/ ^cm3 or less. The pulp molded article according to any one of claims 1 to 8 , which has a single layer structure. A secondary processed pulp molded article, which is obtained by subjecting the pulp molded article according to any one of claims 1 to 9 to a surface treatment. The processed pulp molded article according to claim 10 , wherein the surface treatment is performed by at least one of a direct printing method, a lamination method, a transfer method, and a vapor deposition method. The processed pulp molded article according to claim 10 or 11 , wherein the surface treatment is performed by at least one of a vacuum lamination method and a hot stamp transfer method. A method for producing the pulp molded article according to any one of claims 1 to 9 ,
a pulp suspension preparation step of preparing a pulp suspension;
a papermaking process in which pulp is papered from the pulp suspension through a papermaking mold;
and a hot pressing step of hot pressing the molded intermediate body obtained after the papermaking step while heating it, using a first press die and a second press die positioned in the opposite direction to the first press die. The method for producing a pulp molded article according to claim 13 , wherein a pressure in the hot pressing step is 0.1 MPa or more and 3.0 MPa or less. The method for producing a pulp molded article according to claim 13 or 14 , wherein a temperature in the hot pressing step is 130°C or higher and 280°C or lower.