JP2005139582A - Pulp formed body and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a formed body exhibiting high convenience by locally arranging a low density part excellent in a cushioning performance and a heat-insulating performance regardless of the part being inferior to strength while the part has strength enough to basically maintain a three-dimensional shape and to provide a method for simply producing the formed product having various shapes and exhibiting a high cushioning performance and a heat-insulating performance at a low cost in a short time. <P>SOLUTION: The pulp formed body obtained by partially fixing mats each composed of a pulp fiber and a core-sheath structure type binder fiber composed of a thermoplastic resin fiber, particularly the pulp formed body in which the binder fiber is a chopped strand fiber arranging polypropylene in the core part and arranging polyethylene in the sheath part and cut into 4-7 mm length and further provides the method for producing the pulp formed body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a molded body such as a container or a tray, and particularly relates to a molded body having buffering properties and heat insulating properties, and a method for manufacturing the same.

Conventionally, in order to impart a buffering function to a pulp-derived structure, as represented by a corrugated cardboard, a method of attaching a flute layer as a buffering material to an intermediate layer of front and back liner paper, a nonwoven fabric, a polycap, etc. A technique is used in which a bulky material is bonded to a material with poor buffering properties. Moreover, in order to give a heat insulation function, in addition to the above-mentioned two methods, by applying heat to a thermoplastic resin having a relatively low melting point such as polyethylene previously laminated on a base material, several hundred μm to several mm A technique for providing a resin foam layer is widely known.
Japanese Patent No. 3272316 JP 2001-247171 A

  However, in the manufacture using the above-described conventional method, there is no method other than three-dimensional forming except that a ruled line is processed on a paperboard and then folded along the ruled line to assemble, so that usually corner portions exist. Further, even when a three-dimensional shape is given by drawing, there is a problem that paper is wrinkled or the shape is not flexible.

  In addition, regarding the method of bonding another member having an excellent buffering action, a molding process for the base molded body and a buffering material bonding process are required at the minimum, which increases costs.

  The present invention has been made to solve the above-described problems, and proposes a molded body that can exhibit high productivity and high shape freedom during molding, and a method for manufacturing the same.

  The molded body of the present invention is a partial press of a composite material composed of pulp fibers and binder fibers with a special press die having recesses in male or female molds or both molds as shown in FIG. It is characterized in that it is processed to obtain a molded body having parts with different densities. The molded body of the present invention can be applied to a wide variety of shapes. It is possible to control the density of the low density part by controlling the depth of the concave part.

  The method for producing a molded body of the present invention is a process in which pulp fibers and binder fibers are mixed by a dry method, subjected to heat treatment to melt the binder fibers, fused, matted, and then partially heat-pressed again. It is characterized by having.

  Specifically, in the invention according to claim 1, a pulp molded body characterized in that a pulp fiber and a mat made of a core-sheath structure type binder fiber made of a thermoplastic resin fiber are partially fixed. Is to provide.

The invention according to claim 2 is characterized in that the binder fiber is a chopped fiber having a length of 4 to 7 mm in which polypropylene is disposed in the core and polyethylene is disposed in the sheath. Provide the body.

  In invention of Claim 3, the resin layer which consists of a thermoplastic resin is provided in the surface, The pulp molded object of Claim 1 or 2 characterized by the above-mentioned is provided.

  In the invention according to claim 4, a mat obtained by dry-mixing and stacking a core-sheath type binder fiber composed of pulp fibers and thermoplastic resin fibers is subjected to heat treatment with hot air, and then a male and female pair. The present invention provides a method for producing a pulp molded body, characterized in that the mixed material is fixed by heating and pressurizing with a press die of the above, and melted thermoplastic fibers.

  The invention according to claim 5 is characterized in that the binder fiber is a chopped fiber cut to a length of 4 to 7 mm in which polypropylene is disposed in the core and polyethylene is disposed in the sheath. Provide the body.

  In invention of Claim 6, the emulsion or dispersion which consists of a thermoplastic resin is apply | coated to the surface, and the resin layer is provided in a surface layer, The pulp molded object of Claim 4 or 5 provided is provided. is there.

  The pulp molded body of the present invention basically has a sufficient strength to maintain a three-dimensional shape, and locally arranges a low-density portion that is inferior in strength but excellent in buffer performance and heat insulation performance, It is highly convenient.

  With the method for producing a molded article of the present invention, it is possible to produce a molded article that has various shapes at a low cost in a simple manner and exhibits high buffering performance and heat insulation performance.

  Therefore, according to the present invention, it is extremely useful as a supplementary material for physical distribution packaging that requires high buffering performance, hot beverages that require heat insulation performance, and cup noodle packages.

The molded body of the present invention is formed of a composite material in which pulp fibers and a binder resin are integrated, and both a low density portion and a high density portion are present in the final product. The high density portion is 0.80 to 0.95 g / cm ^{3 in} terms of strength, and the low density portion is 0.06 to 0.15 g / cm ^{3 in} terms of the occurrence of paper dust and fluffing of pulp fibers on the surface layer. Is desirable.

  As the pulp fiber, for example, herbaceous fibers such as hardwood, conifer, rice, straw and bagasse are suitable. In addition to deinked pulp (DIP) derived from waste paper, defibrated pulp obtained by defibrating waste paper is also possible. Furthermore, not only plant-derived fibers but also fibers including materials such as synthetic fibers may be used in combination, and may contain additives such as sizing agents used in ordinary wet papermaking. I do not care.

  The above-mentioned pulp fiber bears the main component of the composite material in the present invention and contributes to the strength as a molded body.

As the binder fiber, various thermoplastic resins can be applied, depending on chemical compatibility with pulp fiber and other mixed materials, and use of the molded body. However, from the viewpoint of ease of fusion processing, those having a low melting point are good. Polyolefin, especially polyethylene and polypropylene when considering the cost aspect, and polylactic acid and polybutylene succinate as resins having biodegradability, Polyhydroxybutyrate hexanoate and the like are preferable. As the cross-sectional structure of the binder fiber, a fiber having a core-sheath type double structure is optimal in consideration of strength retention after heat fusion treatment, a low melting point resin in the outer sheath part, and a core in the inner core part. It is optimal to arrange a resin having a melting point higher than that of the sheath.

  This binder fiber is also preferably a fiber having a fiber length of 1 to 25 mm before melting for ease of entanglement with plant fibers and activated carbon fibers and prevention of dropout in the fiber production process.

  Among these, 4 to 7 mm is particularly preferable in order to facilitate mixing of different components.

  Also, the fiber diameter is preferably 0.5 to 50 dtex for the same reason. Furthermore, it is also effective to perform crimping with the aim of entanglement with pulp fibers.

  The presence of this binder fiber makes it possible to form a three-dimensional molded body in which the mixed materials are integrated and the shape can be maintained.

  Coating liquids for preventing paper dust scattering include acrylic resins such as polyethylene wax and polymethylmethacrylic acid and their copolymers, modified starch, polylactic acid, polybutylene succinate, and polyhydroxybutyrate hexanoate. Any material that melts at an appropriate temperature and solidifies after heating can be used, such as a biodegradable resin emulsified with an emulsifier or a dispersion at high temperature and pressure. is there.

  The proportions in the composite material are preferably 51 to 95% by weight for pulp fibers and 5 to 49% by weight for binder fibers. Although a more appropriate ratio of these depends on the application to which the molded body is applied, when the pulp fiber is less than 70 to 90% by weight, the strength as the molded body is excellent.

  It is also possible to mix other components in the composite material without departing from the gist of the present invention. For example, if necessary, various known additives, that is, antioxidants, plasticizers, slip agents, various stabilizers, antiblocking agents, antistatic agents, dyes, pigments, weathering stabilizers, antistatic agents Anti-fogging agent, leveling agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, silane coupling agent, deodorant, fragrance, inorganic filler, organic filler, surface-organized inorganic filler, etc. It is possible to add a filler or the like.

  An example of a manufacturing method is described below about the pulp molding in this invention.

  The method for producing a molded body is a molding using a plurality of the aforementioned materials. When molding the composite material, pulp fibers and binder fibers, which are the main constituent components, are mixed by a dry method and subjected to heat treatment. The binder fibers are melted, fused, and integrated.

  Specifically, as shown in FIG. 2, the pulp fibers and binder fibers sufficiently defibrated from the two hoppers 4 and 5 are quantitatively supplied to the kneading rotor 6 that moves at a rotational speed of 3000 rpm or more, These are mixed and spread on the belt conveyor 7 on the air flow flowing in the box to form a web 8. As the conveyor 6 used at this time, a forming conveyor having a mesh-like conveyance belt is preferable from the viewpoint of preventing the material from falling off and the surface property of the belt contact surface of the web. A uniform sheet (mat) is obtained.

Thereafter, heat treatment is performed to melt the binder fiber. In order to perform the heat treatment, as shown in FIG. The heating device 9 in the illustrated example blows hot air toward the web 8 on the mesh conveyor 7 from above or from below to control the air volume so that hot air penetrates in the thickness direction. Depending on the type of binder fiber, for example, if the binder fiber is a core-sheath type in which polypropylene is the core and polyethylene is the sheath, it is optimal to blow hot air heated to 120 to 160 ° C. In addition, examples of the heating device include those using an infrared heater or an electron beam. However, the heating device using hot air is most excellent in applying heat to the inside of the web, which is advantageous in terms of productivity. .

  Further, by applying pressure treatment using a nip roll or the like after the heat treatment, the balance of the surface property and thickness of the web is improved, and subsequent processing becomes easy. Thereafter, a desired molded body is obtained by pressing with a male-female integrated die having a recess on the male die side as shown in FIG. 1 heated to 130 to 150 ° C.

  In the present invention, it is important to use the dry method in this way. That is, a pulp slurry in which pulp fibers are dispersed in water, which is generally used in the past and is called a so-called wet pulp molding method, is made with a paper net having a specific shape and press dried to form. In the method of obtaining a body, it is difficult to control the density, and all the parts are uniformly the same density, and it seems impossible to obtain a molded body having a clear difference in density as in the present invention. .

  In addition, in order to make it into a mat shape, it is preferable to manufacture by a fiber-laying process in which fibers are piled down like web-like cotton.

<Example 1> Physical distribution packaging material with buffer function: see FIG. 4 90 parts by weight of defibrated pulp fibers defibrated from sheet pulp made of softwood-derived bleach kraft pulp (NBKP), polyethylene for the sheath and polypropylene for the core 10 parts by weight of 5 mm long cut core-sheath type thermoplastic resin fibers were mixed by a dry method and piled by the airlaid method to prepare a mixed mat of 400 g / m ² . Further, by passing hot air at 165 ° C. through the aforementioned mat, the sheath portion of the resin fiber was melted and combined with the pulp fiber to give a tensile strength of about 2N. Next, this heated mat is heated and pressed at a pressure of 200 kN per molded body with a male-female mold (see FIG. 1) heated to 140 to 150 ° C., and a part of the bottom surface portion has excellent buffering effect. A tray-shaped three-dimensional molded article 11 having a depth of 40 mm provided with a low-density portion 10 and a high-density portion 11 having excellent strength at a part of the bottom surface in order to express the strength of the side surface portion, the bottom corner portion, and the bottom surface portion. It was. At that time, the molding time was set so that the density of the high density portion was 0.90 g / cm ³ and the density of the low density portion was 0.15 g / cm ³ . Finally, for the purpose of preventing the scattering of paper dust from the surface, the acrylic styrene copolymer emulsion is spray-coated at a coating amount of 3 g / m ² , and quickly heated at 150 ° C. × 30 with a warm air / infrared hybrid heater. Second drying was performed, and a thin resin layer was provided on the surface layer.

<Example 2> Heat insulation jacket material for hot beverages: See FIG. 5 FIG. 5 shows a two-mixed mat manufactured in the same process as in Example 1 and is pressed under the same hot press conditions and partially has a low-density part. The heat insulating jacket material for hot beverages described was obtained. At the time of use, as shown in FIG. 5, the jacket material 13 is attached to the outside of the paper cup 12 containing the hot beverage, and a hand is put on it to drink. Since the gap between the convex portion formed by the low density portion and the side wall of the paper cup constitutes a heat insulating air layer and the heat of the hot beverage is not transmitted to the hand holding the cup, it is effective as a measure for preventing a cup drop accident during drinking.

It can be used as logistics packaging that requires buffering performance, as a supplement for hot beverages and cup noodle packaging that require heat insulation performance.

It is sectional drawing of the metal mold | die used for this invention. It is a conceptual sectional view of a process explaining an example of a manufacturing method of a forming object of the present invention. It is a conceptual sectional view of a process different from FIG. 2 for explaining an example of a method for producing a molded article of the present invention. It is sectional drawing (1) and top view (2) which show the Example of this invention. It is the side view and sectional drawing which show the usage example of the Example different from FIG. 4 of this invention.

Explanation of symbols

1: Male mold (bottom recessed)
2: Female mold 3: Mold recess 4: Hopper A
5: Hopper B
6: Kneading rotor 7: Web 8: Conveyor 9: Heating device 10: Low density part of pulp molding 11: High density part of pulp molding 12: Cup 13: Thermal insulation jacket material

Claims (6)

  A pulp molded product, characterized in that a pulp fiber and a mat made of a core-sheath structure type binder fiber made of a thermoplastic resin fiber are partially fixed.   The pulp molded body according to claim 1, wherein the binder fiber is a chopped fiber cut to a length of 4 to 7 mm in which polypropylene is disposed in a core portion and polyethylene is disposed in a sheath portion.   The pulp molded body according to claim 1 or 2, wherein a resin layer made of a thermoplastic resin is provided on the surface.   A mat obtained by dry-mixing and stacking a core-sheath binder fiber composed of pulp fibers and thermoplastic resin fibers, heat-treated with hot air, and then heated and pressurized with a pair of male and female press dies, A method for producing a pulp molded body, comprising fixing a mixed material through melted thermoplastic fibers.   The pulp molded body according to claim 4, wherein the binder fiber is a chopped fiber having a length of 4 to 7 mm in which polypropylene is disposed in a core portion and polyethylene is disposed in a sheath portion.   The pulp molded body according to claim 4 or 5, wherein an emulsion or dispersion comprising a thermoplastic resin is applied to the surface and a resin layer is provided on the surface layer.

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