JP2002105900A - Low-density molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lightweight low-density molded article having excellent cushioning properties by a wet molding method. SOLUTION: This low-density molded form with thick-walled ribs is obtained by the following process: a mold with a number of perforations on the wall surface is fed with a slurry having a Canadian standard freeness of >=550 mL to remove water as the slurry medium through the perforations to accumulate a perforation-impassable fine component in the slurry in the mold, thus forming a wet molded product, which is then dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet-processed molded product which is easy to recycle and dispose, is lightweight, and has excellent buffer characteristics.

[0002]

2. Description of the Related Art Styrofoam, which is most widely used as a cushioning material for packaging, has excellent shock absorbing properties, is easy to be processed into an arbitrary shape, is inexpensive, lightweight, and has a good appearance. Etc. However, in recent years, as interest in environmental issues has increased, as with other so-called plastic products, there has been an increasing demand for post-use treatment. In other words, it has been pointed out that in the case of incineration after use, damage to the furnace and generation of toxic gas due to high temperature are pointed out. In addition, landfill disposal has no decomposability and is bulky, which is considered to be one of the causes of shortage of disposal sites. Recently, pulp molds using recycled pulp as a raw material have attracted attention as a solution to the problem of the disposal of styrofoam, and are increasingly used as substitutes. However, this pulp mold method is obtained by depositing pulp in slurry in a mold having many small holes while sucking and dewatering, and then drying the pulp. Because it is inferior, only thin layers can be efficiently produced,
The obtained thin material is inferior in characteristics and has a limit as a cushioning material. In contrast, prior to the filing of the present application, the present inventors removed water, which is a medium of the slurry, from the small holes of the mold having a large number of small holes to thereby remove the fine pore non-passing fine components in the slurry. A low-density molded product having a thick and excellent buffering property by using, as a raw material, a highly drainable slurry having a Canadian Standard Freeness (CSF) of 550 ml or more as a raw material in the same wet process as the pulp mold to be deposited therein. Is proposed to be obtained.

[0003]

However, the low-density molded article having a thick wall obtained by using a highly drainable slurry having a Canadian Standard Freeness (CSF) of 550 ml or more as a raw material is made of styrene foam. In comparison, since the density is considerably high, there is a problem that the weight increases when the thickness is increased in order to obtain a material having a good cushioning property, and the weight becomes considerably heavy as compared with the styrene foam cushioning material. An object of the present invention is to provide a low-density molded article that is lightweight and has excellent buffer characteristics by the above-mentioned wet process.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the present situation, and as a result, have found that by devising the structure of a molded article, a lightweight and excellent cushioning material can be obtained. The present invention has been completed. That is, according to the present invention, the Canadian standard freeness (CSF) of the slurry composition is 550 m in a mold having a large number of small holes on the wall surface.
1 or more of the slurry is supplied, and water, which is a medium of the slurry, is removed from the pores of the molding die, thereby depositing fine components that do not pass through the pores in the slurry in the molding die to form a wet molded product. A low-density molded article characterized by having a thick rib obtained by drying the molded article. Especially, it is preferable that the rib distance of the thick rib is 5 mm or more. Further, it is preferable that the mold is a concave mold having an open surface. Further, when forming a wet molded product, it is preferable to deposit the material over the open surface of the mold, and to cut off the portion deposited beyond the open surface as an unnecessary portion before the drying step. Further, the main component of the slurry composition is preferably a cellulosic fiber.

The success of the present invention has arisen when a low-density molded article obtained by a wet method employs a thick rib structure to simply increase the thickness of the molded article in order to increase the cushioning property. The point is that it has been found that an increase in weight can be suppressed and that a sufficient buffer effect can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings to specifically show the present invention, but the present invention is not limited thereto. In addition, here, the description will be made using a pulp slurry, but the raw material of the present invention is not limited to this pulp. FIG. 1 is a perspective view showing an example of a low-density molded body 10 of the present invention having a structure in which a rib 13 is attached to a side wall 14,
FIG. 2 is a perspective view of a low-density compact 11 as a comparative example of the present invention having no rib. FIG. 3 is a perspective view showing an example of a low-density molded body 12 having another type of thick rib structure. The difference between FIG. 1 and FIG. 3 is that in FIG.
Is attached to the side wall 14, whereas in the case of FIG. 3, the rib also serves as the side wall. 1, 2, and 3 each have a concave portion 15 for storing and protecting a product in the center, and is used as a cushioning material for packaging. The low-density compacts (10, 12) having the rib structure of FIGS. 1 and 3 have substantially the same buffer characteristics as the compact (11) of FIG. 2 without the rib structure. Nevertheless the weight is quite light. FIG. 4 is a perspective view of the concave mold 16 used for manufacturing the low-density molded body of FIG. 1, and FIG. 5 is a cross-sectional view taken along line AA. 6 to 11 are cross-sectional views illustrating an embodiment of the present invention performed using the mold. The concave mold 16 used as shown in FIG. 5 is a concave shape of an open top having a double wall composed of an inner wall 17 and an outer wall 18, and the inner wall 17 has a number of small holes 19 for dewatering. A suction chamber 20 is formed by the inner and outer double walls, and a suction port 21 is attached to the bottom of the outer wall.
The molding process is performed on the mold 16 as shown in FIG.
The pulp slurry 24 having good drainage is supplied from the upper guide 23 in this state, and is filled up to the upper portion of the hopper. Next, as shown in FIG.
The pulp sediment 25 is formed in the mold by performing suction dehydration from the suction port 21 provided at the lower part of the mold 6. At that time, the pulp is deposited in a state of rising on the open surface of the mold 16. Subsequently, as shown in FIG. 8, the hopper 22 is removed, and then, as shown in FIG.
It is resected at 7. Next, as shown in FIG.
8 is set on the upper side, hot air is sent from the hot air port 29 while being sucked from the suction port 21, released from the small holes 30, passed through the pulp sedimentary layer, dried, and taken out from the molding die. A molded body 10 (cross-sectional view of FIG. 1) is obtained.

[0007] The mold used for producing the molded article of the present invention is not particularly limited, but it is an excellent mold in that the slurry can easily enter into the details of the mold, and the molded article is less likely to generate porosity. A concave mold having a large number of small holes on one wall and one surface being open is preferred.
As a material for the molding die, a material known in the pulp mold industry can be used, and usually, a metal material such as iron or aluminum is used. As a molding die, a mold having a 15-200 mesh wire mesh attached to the surface of a mold having small holes is usually used. It is not always necessary to use the same wire mesh as the entire surface. For example, different types such as a low mesh on the bottom surface and a high mesh on the side surface can be used in combination. Further, the bonding of the metal mesh is not necessarily performed on the entire surface of the mold, but may be performed on only a part of the surface of the mold. As the small hole of the mold, a circular hole having a diameter of 1 to 10 mm is usually used, and a small hole of the same size may be provided on the entire surface of the mold. It is common to change. As a normal mold, it is preferable to increase the opening ratio as it goes deeper, but it is preferable to provide a large number of small holes in the place where the opening ratio is to be increased, and to provide a small hole in a portion where the opening ratio is to be lowered. It is common to provide small holes. Further, a mold having a draft angle (taper) of 1 to 5 ° is usually used so that the molded body can be easily taken out.

In the present invention, a slurry composition having a filterability of 550 ml or more, which is a Canadian standard freeness, capable of efficiently forming a molded article having a thick sedimentary layer is used as the slurry composition. When a molded article is used as a buffer, a natural organic polymer fiber is usually preferably used as a main raw material. But,
In the present invention, the present invention is not limited to this, and other examples include coarse powder and fine particles made of a natural organic polymer, which can be appropriately selected depending on the application. These may be used alone or in combination.

Hereinafter, the natural organic polymer fiber-containing system which is most suitable as a raw material of the cushioning material will be mainly described in more detail, but the present invention is not particularly limited thereto. Examples of natural organic polymer fibers include (1) unbleached or bleached chemical pulp obtained by kraft pulping, sulfite pulping, alkali pulping, etc. of coniferous or hardwood, or GP, TMP (thermomechanical pulp) Mechanical pulp such as, or cotton pulp, linter pulp, water repellency, water resistance described in Japanese Patent Application No. 10-0322920,
Waste paper pulp, liquid ammonia-treated pulp, mercerized pulp, and curled fiber (manufactured by Warehauser, USA, trade name:
HBA-FF, NHB405, NHB416), cellulosic fibers such as hemp fibers described in Japanese Patent Application No. 10-377923, (2) protein fibers such as wool, silk, and collagen fibers, and (3) chitin. Complex sugar chain fibers such as chitosan fiber and alginic acid fiber are exemplified. Among them, cellulosic fibers are particularly preferable because they are excellent in performance and easy to procure.

When it is desired to increase the interlaminar strength of the molded article, the pulp is mechanically treated with a sand grinder or the like to be fibrillated to obtain a number average fiber length of 0.01 to 0.80.
Slurry composition comprising fine fibers in the range of mm or thermoplastic fibers such as polyethylene fibers, polypropylene fibers, polyethylene-polypropylene sheath core fibers, copolymerized polyester-polyethylene terephthalate sheath core fibers, and biodegradable aliphatic polyester fibers. Is effective. Among them, a combination of pulp-based fine fibers and thermoplastic synthetic fibers is particularly preferable because a molded article having less deformation and excellent surface smoothness can be obtained. In addition, as the thermoplastic synthetic fiber, a short fiber having a number average fiber length in a range of 2 to 20 mm, which is easily dispersed in a medium at the time of preparing a slurry, is particularly preferable. These pulp-based fine fibers and thermoplastic synthetic fibers are used alone or in combination of two or more, and are usually blended in a range of 2 to 40% by dry weight with respect to the composition.

The strip-shaped waste paper described in Japanese Patent Application No. 2000-105555 is excellent in performance and is preferable as a material used in combination with the above-mentioned cellulosic fiber. Formulation is usually 5 to 8 on a dry weight basis relative to the composition.
It is blended in the range of 0%.

The slurry composition may further contain an adhesive, a waterproofing agent, a water repellent, a dye, a pigment, a drainage improver, a pH adjuster, a slime control agent, a thickener, and the like, if necessary.
Preservatives, fungicides, antibacterial agents, flame retardants, rodenticides, insecticides, humectants, freshness preservatives, oxygen scavengers, foaming agents, surfactants, electromagnetic shielding materials, antistatic agents, rust inhibitors, fragrances ,Deodorants,
Thermoplastic resin powder, foamable thermoplastic resin powder, various microcapsules having foaming properties, aromatic properties and the like can be selected and blended. These may be used in combination of two or more.

The slurry composition of the present invention is prepared by blending the above materials so that the Canadian Standard Freeness (CSF) becomes 550 ml or more. Incidentally, in the present invention, the Canadian Standard Freeness (CSF) of the slurry composition is JIS-
It is measured by a method based on P-8121.

As the medium used for forming the slurry, water is usually used, but a mixture of water and an alcohol (methanol or ethanol) can also be used. The concentration of the slurry is usually 0.05 to
5% by weight, but 0.03
Those having a range of 5 to 2% by weight are preferred.

In the case of using a concave mold having an open surface on one side, the slurry is injected into the mold by using a pump having an open port facing upward by a pump from the open port as in a normal pulp mold. Immerse the slurry in the slurry tank with the opening facing downward, and suck the slurry into the mold from the downward opening by sucking through the small holes.
It is possible to adopt a method in which the mold is sucked while sinking the mold into the slurry tank with the open port facing upward, and the slurry is sucked into the mold through the open port.

As a method for removing the medium of the slurry from the small holes, there are, for example, a suction dehydration method, a gas pressure dehydration method, a mechanical pressure dehydration method, an electroosmotic dehydration method and the like, and these can be combined. The type of slurry used for pouring is usually one type, but the pouring of the slurry is divided into two or more stages, and the composition of the slurry used at that time is changed to form a state in which deposited layers of different compositions are sequentially laminated. You can also get things.

In the present invention, the Canadian Standard Freeness (CS)
F) Since a highly drainable slurry composed of a composition of 550 ml or more is used, the fluidity is poor, and when formed using a concave mold having an open surface, the deposited layer on the open surface is likely to have irregularities. When compressed and dried with a plate having a flat and smooth surface and dried, the molded product becomes uneven in density. Therefore, as described in Japanese Patent Application Laid-Open No. 10-49985, a wet molded product is used. In the formation, it is desirable to deposit so as to exceed the open surface of the lower mold, and to cut off unnecessary portions that have accumulated beyond the open surface of the mold before the drying step. Examples of the unnecessary portion removing device include a belt saw, a tip saw, a chain saw, a chain slitting machine, a high-pressure water curtain, a sander, and the like.

Drying after dehydration can be performed in a molding die or outside a molding die, but in terms of quality, drying in a die is more excellent. As a drying method, a method known in the paper industry such as hot air drying, infrared drying, and microwave drying can be used.However, since the cushioning material of the present invention is excellent in air permeability, it is preferable to dry the deposited layer in a wet state. It is desirable to use a method for efficiently passing heated air. Specifically, inject heating air into a wet molded product, suction while supplying heating air from the opposite side of the molded product, and inject heating air into the wet molded product from the opposite side of the molded product. For example, a method of suctioning can be used. Considering the production efficiency of the cushioning material, it is desirable to dry under the condition that the heating air flows in the deposition layer at a flow rate of 1 liter / cm ² · min or more. Particularly preferably, it is 5 liter / cm ² · min or more.

The thickness of the deposited layer of the low-density molded product of the present invention is preferably 10 mm or more, particularly preferably 15 mm or more, in terms of buffer characteristics and strength. In addition, the rib distance, that is, the protrusion distance from the side wall in the case of the structure in which the rib is attached to the side surface (FIG. 1A), and the protrusion distance of the rib itself in the case of the structure having no side wall other than the rib (FIG. 3). B) is preferably 5 mm or more, particularly preferably 10 mm or more, from the viewpoint of the buffer characteristics and the effect of reducing the weight. As a low-density molded body having a thick rib,
In addition to the above, corner materials (31, 32) as shown in FIGS. 12 and 13 can be used, but the present invention is not limited to these. Incidentally, the rib of the present invention may be of a shape known in the art, and is not particularly limited.

The low density molded article of the present invention having a rib structure is sprayed, impregnated,
The adhesive can be contained by means such as coating. Examples of the adhesive include starch, processed starch, vegetable gum, gelatin, casein, PVA, CMC, hydroxyethyl cellulose, urea formaldehyde resin, melamine formaldehyde resin, vinyl acetate resin emulsion, acrylic ester resin emulsion, ethylene- Examples thereof include those known in the art, such as a vinyl acetate copolymer emulsion and a styrene-butadiene copolymer emulsion. In addition to the adhesive, if necessary, a water resistance agent, a water repellent, a dye, a pigment, a preservative, a fungicide, an antibacterial agent, a flame retardant, a rodenticide, an insect repellent, a freshness preserving agent, a deoxidizing agent, An electromagnetic shielding material, an antistatic agent, a rust preventive, a fragrance, a deodorant, and the like can be contained by the same means.

A film or paper can be attached to the surface of the low-density molded article of the present invention in order to prevent the fibers from falling off and to increase the strength. For the film, for example, polyethylene, polypropylene, polystyrene,
Polyvinyl chloride, polyvinylidene chloride, aromatic polyester, aliphatic polyester, polylactic acid, acetylcellulose, ionomer, ethylene vinyl acetate copolymer (E
VA), ethylene vinyl acetate, nylon, polyvinyl alcohol, starch and the like. Among them, biodegradable or water-soluble ones that are easy to dispose are preferable.

As the main raw material of the slurry composition used in the present invention, an environmentally friendly natural organic polymer is used. In addition, a synthetic organic polymer, a semi-synthetic organic polymer, and a fiber made of an inorganic substance are used. -Even when coarse powder, fine particles, etc. are used as the main raw material, the effects of the present invention can be expected in parts other than the environment. Hereinafter, the present invention will be described more specifically with reference to examples. However, needless to say, the present invention is not limited to these examples. In Examples and Comparative Examples, “parts” and “%” indicate “parts by weight” and “% by weight” unless otherwise specified.

Example 1 Jute hemp bags were pulverized by a pulverizer (Atoms Model 14-1200, manufactured by Hyakuma Yamamoto Seisakusho), and then the fibers were softened by a grinder mill (GM4-25, manufactured by Glow Engineering). To obtain hemp fibers having a number average fiber length of 7 mm. The Canadian Standard Freeness of this fiber was measured to be 752 ml. Further, a 1.5-liter sand grinder filled with 80% glass beads having an average particle size of 2 mmΦ is prepared by using a water slurry of waste corrugated paper pulp having a solid concentration of 1% (Dynomill KDL-PIL manufactured by Shinmaru Enterprises).
OT) was introduced and passed at 350 ml / min to obtain fine fibers having a number average fiber length of 0.30 mm. Next, 85 parts (dry weight) of the hemp fiber and 5 parts (dry weight) of the fine fiber were further combined with a copolyester-polyethylene terephthalate sheath-core fiber (TSF. TJ04CN manufactured by Teijin).
2.2 × 5) A mixture of 10 parts (dry weight) was mixed with water to adjust the solid content concentration to 1%, and sufficiently stirred to obtain a slurry. The slurry composition was found to have a Canadian standard freeness of 697 ml. Subsequently, a concave mold 16 having a capacity of 4.5 L shown in FIG. 5 is prepared.
Further, as shown in FIG.
After the suction chamber 20 was first filled with water, the slurry was supplied from the guide 23 into the hopper. Subsequently, as shown in FIG.
After dehydrating by suction from No. 1, the fibers were deposited so as to swell on the open surface of the mold. Next, as shown in FIG. 8, the hopper 22 was removed, and then unnecessary portions deposited so as to rise on the open surface of the mold as shown in FIG. Next, as shown in FIG. 10, a drying device 28 is set in close contact with the smooth surface of the wet molded product, and hot air is sent from a hot air port 29 while being sucked from the suction port 21 for drying. A molded article having a structure was obtained. For drying, hot air at 210 ° C. was used and suction was performed under the condition of −600 mmHg. As a result, it took 4 minutes. The obtained molded body was light as 380 g, and as a result of evaluation, was found to have excellent buffer properties similar to those of the following comparative examples.

<Comparative Example 1> Except that a different mold was used, molding and drying were performed in exactly the same manner as in Example 1 to obtain a molded body without a rib structure as shown in FIG. The obtained molded body is 54
It had a weight of 5 g.

[0025]

As described above, according to the present invention, a slurry having a Canadian standard freeness (CSF) of 550 ml or more is supplied to a mold having a large number of small holes on a wall surface, and the small size of the mold is reduced. By removing water, which is the medium of the slurry, from the pores, the small pore-impermeable fine components in the slurry are deposited in a mold to form a wet molded article, and then the molded article is dried. Since it is a low-density molded article characterized by having a thick rib, it is lightweight and has excellent cushioning characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a low density molded body having a thick rib structure.

FIG. 2 is a perspective view of a low density molded body having no rib structure.

FIG. 3 is a perspective view showing another example of a low density molded body having a thick rib structure.

FIG. 4 is a perspective view of a concave mold used for manufacturing the low-density molded body of FIG. 1;

FIG. 5 is a cross-sectional view of the concave mold of FIG. 4 taken along the line AA.

6 is a cross-sectional view showing a state in which a hopper, which is an enclosure for slurry storage, is mounted on the concave mold of FIG. 5, and pulp slurry is supplied from an upper guide.

FIG. 7 is a cross-sectional view showing a state in which pulp is deposited in a mold by suction dehydration.

FIG. 8 is a cross-sectional view showing a state where a hopper is removed from the state of FIG. 7;

FIG. 9 is a cross-sectional view showing a state where unnecessary portions accumulated on the open surface of the mold are cut off.

FIG. 10 is a cross-sectional view showing a state where hot air is injected into a wet pulp molded product and dried.

FIG. 11 is a cross-sectional view showing the dry molded product thus obtained.

FIG. 12 is a perspective view of a corner member having a thick rib structure.

FIG. 13 is a perspective view of a corner member having a thick rib structure.

[Explanation of symbols]

10: low-density compact having a thick rib structure, 11: low-density compact having no rib structure, 12: low-density compact having a thick rib structure, 13: rib, 14: side wall, 15: concave portion, 16: concave mold, 17: inner wall, 18: outer wall, 1
9: small hole, 20: suction chamber, 21: suction port, 22: hopper, 23: guide, 24: pulp slurry, 25: pulp sediment, 26: water drop, 27: chip saw, 28: drying device, 29: hot air Mouth, 30: small hole, 31: corner material having a thick rib structure, 32: corner material having a thick rib structure, a: protrusion distance of a rib from a side wall, b: protrusion distance of a rib itself.

Continued on the front page F term (reference) 3E066 AA01 BA01 CA05 CA08 CB01 LA07 LA19 LA20 MA05 4L055 AA07 AA11 AC01 AF33 AF47 BF07 BF08 EA05 EA15 FA20 GA04 GA50

Claims (3)

[Claims] 1. A mold having a large number of small holes in a wall surface,
Canadian Standard Freeness (CSF) of the slurry composition is 5
A slurry of 50 ml or more is supplied, and water, which is a medium of the slurry, is removed from the pores of the molding die, thereby depositing fine components that do not pass through the pores in the slurry in the molding die to form a wet molded product. Characterized by having a thick rib obtained by drying the molded product. 2. The low-density molded product according to claim 1, wherein a rib distance of the thick rib is 5 mm or more. 3. The low-density molded product according to claim 1, wherein the molding die is a concave molding die whose one surface is open.