Pulp molded body

Abstract

To provide a pulp molding which is free from breakage at a portion having a small taper angle.SOLUTION: A pulp molding includes a pulp. The pulp molding is provided with a portion having a taper angle of lower than 10°. The content of a softwood pulp in the pulp is 15 mass% or over on the total mass of the pulp, or the length-weighted mean length of the pulp is 0.88 mm or over.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a molded body made of pulp material.

Background Art

[0002] Conventionally, when packing various articles, cushioning materials such as expanded polystyrene have been used. While expanded polystyrene has excellent cushioning properties, there are problems such as the generation of harmful substances when incinerated after use, and it has an adverse impact on the environment such as not decomposing in the soil when landfilled.

[0003] Therefore, in order to address the above problems, etc., pulp molded bodies made of molding materials mainly composed of pulp are used. As manufacturing methods of pulp molded bodies, a dry molding method and a wet molding method are known.

[0004] In the dry molding method, for example, a pulp slurry is supplied onto a filtration molding die equipped with a screen, and a pulp layer is formed on the screen by a suction dewatering operation to prepare a preform having a predetermined shape. After drying the preform, compression molding is performed using a die having a desired shape.

[0005] In the wet molding method, for example, a pulp slurry is supplied onto a filtration molding die equipped with a screen, and a pulp layer is formed on the screen by a suction dewatering operation. Compression molding is performed using the die as it is to dehydrate the pulp layer, and further drying is performed in the die (Patent Document 1).

[0006] That is, in the dry molding method, the dried pulp preform is compressed to obtain a desired shape, while in the wet molding method, the pulp before drying is compressed and dried to obtain a desired shape.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the dry forming method, in the drying process of the preform, since moisture escapes from the preform, the shape of the preform changes greatly. Therefore, a separate compression molding process is required to obtain a molded product having a desired shape.

[0009] Also, in the dry forming method, it is difficult to manufacture a molded product having a small taper angle at a part such as a corner of a box-shaped container in order to compression-mold the dried preform.

[0010] On the other hand, in the wet forming method, since compression molding is performed with a high water content of the pulp molding material, the fluidity of the molding material is relatively high, the smoothness is high, and it is easy to manufacture a molded product excellent in cosmetic properties by having a part with a small taper angle.

[0011] However, since a particularly large force is applied to a part with a small taper angle during compression molding, the part may be damaged and cracked during compression molding. For this reason, for example, in the wet forming method, since compression molding is performed in a wet state, the pulp molded body at the bent part in the cavity of the mold is easily crushed and cracked. In addition, friction is likely to occur between the part with a small taper angle of the pulp molded body and the mold. In particular, in the case where the pulp molded body has a form including a bottom surface and a side surface, as the height of the side surface increases, damage is likely to occur, and thus a pulp molded body that is more resistant to damage is required.

[0012] An object of the present invention is to solve the above problems. Specifically, an object of the present invention is to provide a pulp molded body that is not damaged at a part with a small taper angle during manufacturing and has high smoothness.

Means for Solving the Problems

[0013] As a result of intensive studies, the inventors of the present invention have found that by devising the molding material used for producing the pulp molded body, it is possible to provide a pulp molded body having a smooth texture with high smoothness without damage to a portion having a small taper angle during production, and thus completed the present invention.

[0014] A first aspect of the present invention is a pulp molded body containing pulp, wherein the pulp molded body has a portion having a taper angle of less than 10°, and the content of softwood pulp in the pulp is 15% by mass or more based on the total mass of the pulp.

[0015] Preferably, the content of hardwood pulp in the pulp is 10% by mass or more based on the total mass of the pulp.

[0016] The pulp molded body according to the first aspect of the present invention may further contain recycled pulp.

[0017] The pulp molded body according to the first aspect of the present invention may be in the form of a container having a bottom surface and side surfaces. In that case, the taper angle can be the angle of inclination of the side surface with respect to a vertical plane from the bottom surface.

[0018] A second aspect of the present invention is a pulp molded body containing pulp, wherein the pulp molded body has a portion having a taper angle of less than 10°, and the length-weighted average fiber length of the pulp is 0.88 mm or more.

[0019] Preferably, the content of softwood pulp in the pulp is 15% by mass or more based on the total mass of the pulp.

[0020] Preferably, the content of hardwood pulp in the pulp is 10% by mass or more based on the total mass of the pulp.

[0021] The pulp molded body according to the second aspect of the present invention may further contain recycled pulp.

[0022] The pulp molded body according to the second aspect of the present invention may be in the form of a container having a bottom surface and side surfaces. In that case, the taper angle can be the angle of inclination of the side surface with respect to the vertical plane from the bottom surface.

Advantages of the Invention

[0023] During the production of the pulp molded body of the present invention, the portion with a small taper angle does not break.

[0024] In addition, the pulp molded body of the present invention has a high degree of freedom in three-dimensional shape and can have various designs.

[0025] Furthermore, since the pulp molded body of the present invention can be manufactured by a wet molding method, it has high dimensional accuracy and excellent surface smoothness.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0027] The present invention is a pulp molded body containing pulp, the pulp molded body having a portion with a taper angle of less than 10°, in the first aspect of the present invention, the pulp contains 15% by mass or more of softwood pulp based on its total mass, and in the second aspect of the present invention, the length-weighted average fiber length of the pulp is 0.88 mm or more.

[0028] Since the pulp molded body of the present invention contains 15% by mass or more of softwood pulp or uses pulp having a length-weighted average fiber length of 0.88 mm or more, the pulp molded body is excellent in strength, and even if the pulp molded body has a portion having a taper angle of less than 10°, the portion is not damaged during the production of the pulp molded body.

[0029] Hereinafter, the present invention will be described.

[0030] [Shape] The pulp molded body of the present invention has a portion having a taper angle of less than 10°. The "taper angle" in the present invention means the angle of inclination with respect to a reference plane, and the reference plane in the present invention is a vertical plane.

[0031] FIG. 1 is a cross-sectional view showing an example of a portion of the pulp molded body of the present invention having a taper angle of less than 10°.

[0032] In the example shown in FIG. 1, the pulp molded body 1 of the present invention, the illustration of which is omitted in its entirety, includes a plurality of convex portions 1a and a base portion 1b having a horizontal plane, and the plurality of convex portions 1a project from the horizontal plane of the base portion 1b. In the example shown in FIG. 1, since an arbitrary article can be sandwiched in the space between the plurality of convex portions 1a and the base portion 1b, the pulp molded body 1 can be used, for example, as a component of a package.

[0033] In the example shown in FIG. 1, for the convex portion 1a, the hook angle (taper angle) θ formed by the inclined surface of the convex portion 1a with respect to the vertical plane (indicated by a dotted line) from the base portion 1b is less than 10°. The hook angle θ is preferably less than 8°, more preferably less than 6°, still more preferably less than 4°, still more preferably less than 2°, and particularly preferably 1° or less. The pulp molded body 1 can include a portion composed of two planes intersecting at right angles. If the taper angle is below a certain level, the pulp molded body is excellent in decorative properties. Also, in the case of a container in which the pulp molded body has a lid shape, a male-female shape, etc., if the taper angle is small, the fitting property is improved, so that it does not separate during transportation and can protect the contents of the container.

[0034] The pulp molded body 1 having the convex portion 1a shown in FIG. 1 has improved strength by using softwood pulp or pulp having a length-weighted average fiber length of 0.88 mm or more. Therefore, even if the hook angle θ is small, the convex portion 1a will not be damaged during the production of the pulp molded body 1. In particular, breakage at the boundary between the convex portion 1a and the base portion 1b and / or at the tip of the convex portion 1a, where relatively large stress is applied during production, is avoided. That is, according to the present invention, breakage of the bent portion on the surface of the pulp molded body 1 can be avoided.

[0035] FIG. 2 is a cross-sectional view showing another example of a portion of the pulp molded body of the present invention having a taper angle of less than 10°.

[0036] In the example shown in FIG. 2, the pulp molded body 2 of the present invention is a container having a bottom surface 2a, a side surface 2b, and an opening 2c. One end of the side surface 2b is in contact with the bottom surface 2a, and the other end of the side surface 2b reaches the opening 2c. In the example shown in FIG. 2, since an arbitrary article can be accommodated in the accommodating portion 2d formed by the bottom surface 2a and the side surface 2b, the pulp molded body 2 shown in FIG. 2 can be used as a container for accommodating various articles. The bottom surface 2a is a horizontal plane.

[0037] In the example shown in FIG. 2, the hook angle θ formed by the side surface 2b with respect to the vertical plane (indicated by a dotted line) from the bottom surface 2a is less than 10°. The hook angle θ is preferably less than 8°, more preferably less than 6°, even more preferably less than 4°, even more preferably less than 2°, and particularly preferably 1° or less. The pulp molded body 2 can include a portion composed of two planes intersecting at right angles.

[0038] The pulp molded body 2 shown in FIG. 2 has improved strength by using softwood pulp or pulp having a length-weighted average fiber length of 0.88 mm or more. Therefore, even if the hook angle θ is small, the side surface 2b will not be damaged during the production of the pulp molded body 2. In particular, breakage at the boundary between the side surface 2b and the bottom surface 2a and / or at the free end of the side surface 2b (the end of the side surface 2b forming the opening 2c), where relatively large stress is applied during production, is avoided. Therefore, the pulp molded body 2 in the form of a container shown in FIG. 2 will not tear.

[0039] The pulp molded body of the present invention can have excellent strength. For example, the pulp molded body of the present invention can have excellent tear strength. For example, the pulp molded body of the present invention has a specific tear strength of 5.0 mN·m 2 / g or more. The specific tear strength of the pulp molded body of the present invention is 6.0 mN·m 2 / g or more is preferable, 7.0 mN·m 2 / g or more is more preferable, 8.0 mN·m 2 / g or more is still more preferable, 9.0 mN·m 2 / g or more is even more preferable, 10.0 mN·m 2 / g or more is still more preferable, 11.0 mN·m 2 / g or more is even more preferable, 12.0 mN·m 2 / g or more is still more preferable, 13.0 mN·m 2 / g or more is even more preferable. The specific tear strength is obtained by dividing the tear strength (mN) measured in accordance with JIS P8116 with the pulp molded body of the present invention in a sheet form by the basis weight (g / m 2 ) of the sheet-like pulp molded body and can be determined.

[0040] [Pulp] In the first aspect of the present invention, the pulp contained in the pulp molded body contains 15% by mass or more of softwood pulp based on its total mass, and in the second aspect of the present invention, the length-weighted average fiber length of the pulp contained in the pulp molded body is 0.88 mm or more.

[0041] Hereinafter, the first aspect and the second aspect of the present invention will be described.

[0042] (First aspect) In the first aspect of the present invention, the pulp contained in the pulp molded body of the present invention contains softwood pulp.

[0043] Coniferous pulp is pulp derived from coniferous trees, and its manufacturing method is not particularly limited, but coniferous bleached kraft pulp (NBKP), coniferous unbleached kraft pulp (NUKP), and coniferous bleached sulfite pulp (NBSP) are preferred. As coniferous trees, trees of the pine order are preferred. For example, cedar (pine order, Cupressaceae), hinoki (pine order, Cupressaceae), pine (pine order, Pinaceae), fir (pine order, Pinaceae), hemlock (pine order, Pinaceae), shirabe (pine order, Pinaceae), cedar (cedar order), hemlock (pine order, Pinaceae), hinoki (cedar order, Cupressaceae), Japanese red pine (pine order, Pinaceae), Douglas fir (pine order, Pinaceae), white fir (pine order, Pinaceae), spruce (pine order, Pinaceae), balsam fir (pine order, Pinaceae), cedar (pine order, Pinaceae), pine (pine order, Pinaceae), radiata pine (pine order, Pinaceae) can be mentioned. One type of coniferous pulp may be used, or two or more types of coniferous pulp may be used in combination.

[0044] The pulp used in the first aspect of the present invention contains 15% by mass or more of coniferous pulp based on the total mass of the pulp. The content of coniferous pulp in the pulp is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and particularly preferably 35% by mass or more based on the total mass of the pulp.

[0045] The upper limit of the content of coniferous pulp in the pulp used in the present invention is not particularly limited, and it is possible to use all of the pulp as coniferous pulp. However, for improving the surface characteristics of the pulp molded body, the content of coniferous pulp in the pulp is preferably 90% by mass or less, more preferably 70% by mass or less, and still more preferably 50% by mass or less based on the total mass of the pulp.

[0046] The content range of softwood pulp in the pulp used in the present invention is not particularly limited. For example, based on the total mass of the pulp, it can be in the range of 15% by mass to 90% by mass, 15% by mass to 70% by mass, 15% by mass to 50% by mass, 20% by mass to 90% by mass, 20% by mass to 70% by mass, 20% by mass to 50% by mass, 25% by mass to 90% by mass, 25% by mass to 70% by mass, 25% by mass to 50% by mass, 30% by mass to 90% by mass, 30% by mass to 70% by mass, 30% by mass to 50% by mass, 35% by mass to 90% by mass, 35% by mass to 70% by mass, or 35% by mass to 50% by mass.

[0047] The pulp used in the present invention may contain hardwood pulp. Hardwood pulp is pulp derived from hardwoods, and its manufacturing method is not particularly limited, but hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), and hardwood bleached sulfite pulp (LBSP) are preferred. Examples of hardwoods include beech, oak, aspen, mangrove, oak, eucalyptus, dronoki, hokoyanagi, sinanoki, hannoki, nara, tabu, shi, shirakaba, poplar, tamu, droyanagi, acacia, alder, lawan. One type of hardwood pulp may be used, or two or more types of hardwood pulp may be used in combination.

[0048] When the pulp used in the present invention contains hardwood pulp, the content of the hardwood pulp is preferably 85% by mass or less, more preferably 80% by mass or less, and still more preferably 75% by mass or less, based on the total mass of the pulp.

[0049] When the pulp used in the present invention contains hardwood pulp, the lower limit of the content of the hardwood pulp is not particularly limited. However, for improving the surface characteristics of the pulp molded body, the content of the hardwood pulp in the pulp is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass or more, based on the total mass of the pulp.

[0050] When the pulp used in the present invention contains hardwood pulp, the range of the hardwood pulp content is not particularly limited. For example, based on the total mass of the pulp, it can be in the range of 10% by mass to 85% by mass, 10% by mass to 80% by mass, 10% by mass to 75% by mass, 30% by mass to 85% by mass, 30% by mass to 80% by mass, 30% by mass to 75% by mass, 50% by mass to 85% by mass, 50% by mass to 80% by mass, or 50% by mass to 75% by mass.

[0051] The pulp used in the pulp molded body of the present invention is preferably wood pulp. In particular, the wood pulp is preferably virgin pulp in terms of drying efficiency. The wood pulp may include pulps other than chemical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP), and bleached chemi-thermomechanical pulp (BCTMP).

[0052] The pulp molded body of the present invention may contain non-wood pulp. The non-wood pulp is not particularly limited, and examples thereof include pulps derived from hemp, bamboo, straw, kenaf, bagasse, paulownia, paper mulberry, cotton, etc. One type of non-wood pulp may be used, or two or more types of non-wood pulp may be used in combination.

[0053] When the pulp molded body of the present invention contains non-wood pulp, the content of the non-wood pulp is not particularly limited, but based on the total mass of the pulp, 15% by mass or more is preferable, 20% by mass or more is more preferable, and 25% by mass or more is even more preferable. Also, the content of the non-wood pulp is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less based on the total mass of the pulp.

[0054] The pulp molded body of the present invention may contain recycled pulp. The recycled pulp is not particularly limited, and examples thereof include pulps derived from waste paper, rayon, cupra, etc. One type of recycled pulp may be used, or two or more types of recycled pulp may be used in combination.

[0055] When the pulp molded body of the present invention contains recycled pulp, the content of the recycled pulp is not particularly limited. However, for the purpose of reducing the environmental load, the content of the recycled pulp is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more based on the total mass of the pulp.

[0056] The above-mentioned wood pulp, non-wood pulp, and recycled pulp contain cellulose fibers.

[0057] The pulp molded body of the present invention can contain non-cellulose fibers selected from various organic fibers, inorganic fibers, or composite fibers thereof. One type of non-cellulose fiber may be used, or two or more types of non-cellulose fibers may be used in combination.

[0058] Examples of the organic fibers include polypropylene, polyethylene, polymethylpentene, polyester, polyester derivatives, acrylic polymers, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyvinyl ketone, polyether, polyvinyl alcohol, aliphatic polyamide, aromatic polyamide, wholly aromatic polyamide, wholly aromatic polyester, polyamideimide, polyimide, polyetheretherketone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylene benzobisthiazole, poly-p-phenylene benzobisoxazole, polytetrafluoroethylene, single fibers composed of these derivatives, or composite fibers formed by combining two or more of these resins. Examples of the inorganic fibers include silica-alumina fibers, alumina fibers, glass fibers, microglass fibers, zirconia fibers, silicon nitride fibers, silicon carbide fibers, and the like.

[0059] When the pulp molded body of the present invention contains non-cellulose fibers, the content of the non-cellulose fibers is not particularly limited, but based on the total mass of the pulp, 15% by mass or more is preferable, 20% by mass or more is more preferable, and 25% by mass or more is even more preferable. Further, the content of the non-cellulose fibers is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less based on the total mass of the pulp molded body.

[0060] The pulp molded body of the present invention may contain components other than cellulose fibers and non-cellulose fibers. The other components are not particularly limited, but examples include various polymers such as starch, polyacrylamide, polyvinyl alcohol, polyamine polyamide epichlorohydrin; sulfuric acid band; sizing agent; filler; coloring agent; fluorescent brightening agent; release agent; fixing agent and other various additives, and one of these can be used alone or in combination of two or more. As the sizing agent, known ones can be used without particular limitation, and examples include rosin sizing agents, alkyl ketene dimer sizing agents, alkenyl succinic anhydride sizing agents, higher fatty acid amide sizing agents, styrene-acrylic sizing agents, and the like. As the filler, known ones can be used without particular limitation, and examples include talc, kaolin, calcium carbonate, magnesium carbonate, clay, titanium oxide, barium sulfate, aluminum hydroxide, amorphous silica, zeolite, sand, ceramic, glass powder, pottery clay, kaolin, perlite, cellulose-based powder, plastic pigment, and other organic fillers. Similarly, the coloring agent is not limited, and examples include direct dyes, reactive dyes, sulfur dyes, building dyes, acid dyes, cationic dyes, inorganic pigments, organic pigments, and the like. Also, the release agent is not limited in the same way, and examples include fatty acid-based release agents, polyethylene wax, paraffin wax, and the like. Similarly, the fixing agent is not limited, and examples include polyamine-based compounds, dicyandiamide compounds, and the like.

[0061] As a method for analyzing the composition of pulp and fibers, various staining methods and qualitative and quantitative analysis methods of JIS P 8120 can be used. Since the materials used for the pulp molded body are the same as those for general paper and paperboard, the pulp molded body can be disintegrated by the disintegration method of "ordinary paper" in JIS P 8120. When disintegration is difficult due to the influence of a water resistance agent or the like, it is advisable to disintegrate by the disintegration method of "paper subjected to special treatment" in JIS P 8120.

[0062] (Second Aspect) In the second aspect of the present invention, the length-weighted average fiber length of the pulp contained in the pulp molded body of the present invention is 0.88 mm or more.

[0063] The pulp with a length-weighted average fiber length of 0.88 mm or more means that, targeting the fibers in the range of 0.20 to 7.00 mm contained in all the pulp in accordance with ISO16065-2, the length-weighted average fiber length is 0.88 mm or more by analysis with a fiber image analyzer described later.

[0064] The length-weighted average fiber length and the like of the pulp contained in the pulp molded body of the present invention can be obtained by the following method.

[0065] First, the pulp molded body is disintegrated using the disintegration method of JIS P 8120 to obtain pulp, and then the pulp is measured by a fiber image analyzer according to ISO16065-2. An ultra-high resolution (UHD) camera in the apparatus captures a grayscale image of the pulp fibers, and parameters such as the length-weighted average fiber length and the length-weighted average fiber width can be calculated by analyzing the image with an analyzer.

[0066] The number of fibers selected when measuring the length-weighted average fiber length and the length-weighted average fiber width is 1,000 or more, preferably 5,000 or more, and more preferably 10,000 or more.

[0067] The length-weighted average fiber length of the pulp is 0.88 mm or more, preferably 0.90 mm or more, and more preferably 1.00 mm or more.

[0068] The length-weighted average fiber length of the fibers contained in the pulp is preferably 2.00 mm or less, more preferably 1.80 mm or less, and even more preferably 1.60 mm or less.

[0069] The length-weighted average fiber width of the fibers contained in the pulp is preferably 18 μm or more, more preferably 19 μm or more, and even more preferably 20 μm or more.

[0070] The length-weighted average fiber width of the fibers contained in the pulp is preferably 40 μm or less, more preferably 30 μm or less.

[0071] It is preferable to use softwood pulp as the pulp. As the softwood pulp, those that can be used in the first aspect of the present invention can be used.

[0072] The pulp used in the present invention preferably contains 15% by mass or more of softwood pulp based on the total mass of the pulp. The content of softwood pulp in the pulp is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more based on the total mass of the pulp.

[0073] The upper limit of the content of softwood pulp in the pulp used in the present invention is not particularly limited, and it is also possible to use only softwood pulp for the entire pulp. However, in order to improve the surface characteristics of the pulp molded body, the content of softwood pulp in the pulp is preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 50% by mass or less based on the total mass of the pulp.

[0074] The content range of softwood pulp in the pulp used in the present invention is not particularly limited. For example, based on the total mass of the pulp, it can be in the range of 15% by mass to 90% by mass, 15% by mass to 70% by mass, 15% by mass to 50% by mass, 20% by mass to 90% by mass, 20% by mass to 70% by mass, 20% by mass to 50% by mass, 25% by mass to 90% by mass, 25% by mass to 70% by mass, 25% by mass to 50% by mass, 30% by mass to 90% by mass, 30% by mass to 70% by mass, 30% by mass to 50% by mass, 35% by mass to 90% by mass, 35% by mass to 70% by mass, or 35% by mass to 50% by mass.

[0075] The pulp used in the present invention may contain hardwood pulp.

[0076] In the second aspect of the present invention, it is preferable to use hardwood pulp. As the hardwood pulp, those that can be used in the first aspect of the present invention can be used.

[0077] When the pulp used in the present invention contains hardwood pulp, the content of the hardwood pulp is preferably 85% by mass or less, more preferably 80% by mass or less, and still more preferably 75% by mass or less based on the total mass of the pulp.

[0078] When the pulp used in the present invention contains hardwood pulp, the lower limit of the content of the hardwood pulp is not particularly limited. However, for improving the surface properties of the pulp molded body, the content of the hardwood pulp in the pulp is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass or more based on the total mass of the pulp.

[0079] When the pulp used in the present invention contains hardwood pulp, the content range of the hardwood pulp is not particularly limited. For example, based on the total mass of the pulp, it can be in the range of 10% by mass to 85% by mass, 10% by mass to 80% by mass, 10% by mass to 75% by mass, 30% by mass to 85% by mass, 30% by mass to 80% by mass, 30% by mass to 75% by mass, 50% by mass to 85% by mass, 50% by mass to 80% by mass, or 50% by mass to 75% by mass.

[0080] The pulp used in the pulp molded body of the present invention is preferably wood pulp. In particular, the wood pulp is preferably virgin pulp in terms of drying efficiency. The wood pulp may include pulp other than chemical pulp such as groundwood pulp (GP), thermomechanical pulp (TMP), and bleached chemi-thermomechanical pulp (BCTMP).

[0081] The pulp molded body of the present invention may contain non-wood pulp. The non-wood pulp is not particularly limited, and examples thereof include pulp derived from hemp, bamboo, straw, kenaf, magnolia, paper mulberry, cotton, bagasse, etc. One type of non-wood pulp may be used, or two or more types of non-wood pulp may be used in combination.

[0082] When the pulp molded body of the present invention contains non-wood pulp, the content of the non-wood pulp is not particularly limited, but based on the total mass of the pulp molded body, 15% by mass or more is preferable, 20% by mass or more is more preferable, and 25% by mass or less is even more preferable. Also, the content of the non-wood pulp is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less based on the total mass of the pulp.

[0083] The pulp molded body of the present invention may contain recycled pulp. The recycled pulp is not particularly limited, and examples thereof include pulp derived from waste paper, rayon, cupra, etc. One type of recycled pulp may be used, or two or more types of recycled pulp may be used in combination.

[0084] When the pulp molded body of the present invention contains recycled pulp, the content of the recycled pulp is not particularly limited, but for reducing the environmental load, the content of the recycled pulp is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more based on the total mass of the pulp.

[0085] The above-mentioned wood pulp, non-wood pulp, and recycled pulp contain cellulose fibers.

[0086] The pulp molded body of the present invention can contain non-cellulose fibers selected from various organic fibers, inorganic fibers, or composite fibers thereof. One type of non-cellulose fiber may be used, or two or more types of non-cellulose fibers may be used in combination.

[0087] Examples of the organic fibers include polypropylene, polyethylene, polymethylpentene, polyester, polyester derivatives, acrylic polymers, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyvinyl ketone, polyether, polyvinyl alcohol, aliphatic polyamides, aromatic polyamides, wholly aromatic polyamides, wholly aromatic polyesters, polyamide-imides, polyimides, polyether ether ketones, polyphenylene sulfides, polybenzimidazoles, poly-p-phenylene benzobisthiazoles, poly-p-phenylene benzobisoxazoles, polytetrafluoroethylene, single fibers composed of these derivatives, or composite fibers formed by compounding two or more of these resins. Examples of the inorganic fibers include silica-alumina fibers, alumina fibers, glass fibers, micro glass fibers, zirconia fibers, silicon nitride fibers, silicon carbide fibers, and the like.

[0088] When the pulp molded body of the present invention contains non-cellulose fibers, the content of the non-cellulose fibers is not particularly limited, but based on the total mass of the pulp molded body, 15% by mass or more is preferable, 20% by mass or more is more preferable, and 25% by mass or less is even more preferable. Further, based on the total mass of the pulp molded body, the content of the non-cellulose fibers is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0089] The pulp molded body of the present invention may contain components other than cellulose fibers and non-cellulose fibers. The other components are not particularly limited, and examples include various polymers such as starch, polyacrylamide, polyvinyl alcohol, polyamine polyamide epichlorohydrin; sulfate bands; sizing agents; fillers; various additives such as coloring agents, and one of these can be used alone or in combination of two or more. As the sizing agent, known ones can be used without particular limitation, and examples include rosin sizing agents, alkyl ketene dimer sizing agents, alkenyl succinic anhydride sizing agents, higher fatty acid amide sizing agents, styrene-acrylic sizing agents, and the like. As the filler, known ones can be used without particular limitation, and examples include talc, kaolin, calcium carbonate, magnesium carbonate, clay, titanium oxide, barium sulfate, aluminum hydroxide, amorphous silica, zeolite, sand, ceramic, glass powder, pottery clay, kaolin, perlite, cellulose-based powder, plastic pigment, and other organic fillers. Similarly, the coloring agent is not limited, and examples include direct dyes, reactive dyes, sulfur dyes, construction dyes, acid dyes, cationic dyes, inorganic pigments, organic pigments, and the like. Also, the release agent is not limited in the same way, and examples include fatty acid-based release agents, polyethylene wax, paraffin wax, and the like. The fixing agent is not limited in the same way, and examples include polyamine-based compounds, dicyandiamide compounds, and the like.

[0090] [Manufacturing method] The pulp molded body of the present invention can be manufactured by a wet molding method.

[0091] For example, a pulp slurry containing pulp is supplied onto a filtration molding die equipped with a screen, a pulp layer is formed on the screen by a suction dewatering operation, compression molding is performed using the die as it is to dewater the pulp layer, and further, drying is performed in the die to manufacture the pulp molded body of the present invention.

[0092] When preparing the pulp slurry used in the present invention, as the beating of the pulp progresses, the entanglement between cellulose fibers increases, and an effect of increasing the strength of the pulp molded body can be expected. The beating degree is preferably 350 mlcsf or more, more preferably 350 to 650 mlcsf, and even more preferably 350 to 550 mlcsf.

[0093] In the wet forming method, the pulp material before drying is compressed and dried into a desired shape. That is, in the wet forming method, since compression molding is performed in a state where the pulp material has a large amount of moisture and relatively high fluidity, the degree of freedom of the three-dimensional shape that can be imparted to the pulp material is high, and molded bodies of various designs can be easily manufactured. For example, in the example shown in FIG. 2, it is easy to manufacture a box-shaped container with a taper angle θ of 1° or less.

[0094] A particularly large force is applied to the portion with a small taper angle during compression molding, but since the strength of the pulp molded body of the present invention is improved by using softwood pulp or pulp with a length-weighted average fiber length of 0.88 mm or more, the portion does not break during compression molding.

[0095] In addition, the wet forming method has relatively high fluidity of the pulp material used and excellent reproducibility of the cavity shape of the mold, so a pulp molded body with high dimensional accuracy can be manufactured, and the surface smoothness of the obtained pulp molded body is also excellent.

[0096] The smoothness of the surface of the pulp molded body can be evaluated by surface roughness. The surface roughness is preferably 8.0 μm or less, more preferably 6.0 μm or less, and even more preferably 5.5 μm or less.

Industrial Applicability

[0097] The pulp molded body of the present invention can be suitably used for various applications.

[0098] The pulp molded body of the present invention can be used, for example, for food cushioning material applications such as egg cartons, food packaging applications such as food packages, cosmetic packaging applications such as cosmetic packages, home appliance cushioning material applications such as display cushioning materials, and various industrial parts cushioning material and packaging material applications. Further, the pulp molded body of the present invention can be used as various containers or parts of containers.

[0099] Since the pulp molded body of the present invention is composed of pulp, which is a carbon-neutral material, it has a small environmental impact and can suppress an increase in the amount of carbon dioxide in the atmosphere even when incinerated. Therefore, the pulp molded body of the present invention can address resource problems such as global warming due to an increase in carbon dioxide in the atmosphere and petroleum depletion.

Examples

[0100] Hereinafter, the present invention will be described more specifically using examples and comparative examples, but the scope of the present invention is not limited to the examples.

[0101] (Example 1) A slurry of pulp containing 20% by mass of softwood kraft pulp (NBKP) and 80% by mass of hardwood kraft pulp (LBKP) was used as the papermaking raw material, and a pulp molded body shown in FIG. 2 was manufactured by a wet molding method in which hot pressing was performed for 60 seconds or more with a metal mold heated to 150°C or higher. As a result, the taper angle of the pulp molded body was 0.4°.

[0102] (Example 2) A slurry of pulp containing 30% by mass of softwood kraft pulp (NBKP) and 70% by mass of hardwood kraft pulp (LBKP) was used as the papermaking raw material, and a pulp molded body shown in FIG. 2 was manufactured by the wet molding method in the same manner as in Example 1.

[0103] (Example 3) A slurry of pulp containing 37% by mass of softwood kraft pulp (NBKP) and 63% by mass of hardwood kraft pulp (LBKP) was used as the papermaking raw material, and a pulp molded body shown in FIG. 2 was manufactured by the wet molding method in the same manner as in Example 1.

[0104] (Example 4) A slurry of pulp consisting of 100% by mass of softwood kraft pulp (NBKP) was used as a papermaking raw material, and a pulp molded body shown in Fig. 2 was produced by a wet forming method in the same manner as in Example 1.

[0105] (Comparative Example 1) A slurry of pulp containing 10% by mass of softwood kraft pulp (NBKP) and 90% by mass of hardwood kraft pulp (LBKP) was used as a papermaking raw material, and a pulp molded body shown in Fig. 2 was produced by a wet forming method in the same manner as in Example 1. As a result, the taper angle of the pulp molded body was 0.4°.

[0106] (Comparative Example 2) Using the papermaking raw material of Example 1, a pulp molded body shown in Fig. 2 was produced using a dry forming method. As a result, the taper angle was 20°.

[0107] (Performance Evaluation) For each of the pulp molded bodies of Examples 1 to 4 and Comparative Examples 1 and 2, the length-weighted average fiber length and length-weighted average fiber width, specific tearing strength, and surface roughness of the pulp in the pulp molded body were measured or determined as follows, and it was visually observed whether cracks occurred in the portion with a small taper angle during production. The results are shown in Table 1.

[0108] Length-weighted average fiber length and length-weighted average fiber width: The pulp molded body was disintegrated by the disintegration method of JIS P 8120, and the obtained pulp was measured by a laboratory fiber property analyzer Valmet FS5 UHD (manufactured by Valmet Corporation).

[0109] Specific tearing strength: Using the sheet-like portion on the bottom surface of the pulp molded body, the tearing strength (mN) was measured according to JIS P 8116, and the tearing strength value was divided by the basis weight (g / m 2 ) of the sheet-like portion to determine.

[0110] Surface roughness: Measured using a PicoPrint surf tester according to JIS P 8151.

[0111]

Table 1

[0112] As shown in the results in Table 1, the pulp molded body produced by the wet forming method using a raw material containing a coniferous pulp in a certain amount or more or a pulp having a length-weighted average fiber length of a certain amount or more had no breakage at the site with a small taper angle during production and was also excellent in smoothness. On the other hand, in Comparative Example 1, cracks as shown in Figure 3 were observed at the site with a small taper angle.

Explanation of Signs

[0113] 1 Pulp molded body 1a Convex part 1b Base part 2 Pulp molded body 2a Bottom surface 2b Side surface 2c Opening 2d Accommodating part

Claims

1. A pulp molded body containing pulp, wherein the pulp molded body has a portion having a taper angle of less than 10°, the content of softwood pulp in the pulp is 15% by mass or more based on the total mass of the pulp, and the length-weighted average fiber width of the pulp is 19 μm or more. A pulp molded body.

2. The pulp molded body according to Claim 1, wherein the content of hardwood pulp in the pulp is 10% by mass or more based on the total mass of the pulp.

3. The pulp molded body according to Claim 1 or 2, wherein the pulp further contains recycled pulp.

4. A container having a bottom surface and side surfaces, the pulp molded body according to any one of Claims 1 to 3.

5. The pulp molded body according to Claim 4, wherein the taper angle is the angle of inclination of the side surface with respect to the vertical plane from the bottom surface.

6. A pulp molded body containing pulp, wherein the pulp molded body has a portion having a taper angle of less than 10°, the length-weighted average fiber length of the pulp is 0.88 mm or more, and the length-weighted average fiber width of the pulp is 19 μm or more. A pulp molded body.

7. The pulp molded body according to Claim 6, wherein the content of softwood pulp in the pulp is 15% by mass or more based on the total mass of the pulp.

8. The pulp molded body according to Claim 6 or 7, wherein the content of hardwood pulp in the pulp is 10% by mass or more based on the total mass of the pulp.

9. The pulp molded body according to any one of Claims 6 to 8, wherein the pulp further contains recycled pulp.

10. A container having a bottom surface and side surfaces, the pulp molded body according to any one of Claims 6 to 9.

11. The pulp molded body according to Claim 10, wherein the taper angle is the angle of inclination of the side surface with respect to the vertical plane from the bottom surface.

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