JPH0827700A - Molded article of pulp - Google Patents

Abstract

PURPOSE:To obtain a molded article of pulp useful as a packing material replacing expanded polystyrene, having the same cushioning characteristics as those of the expanded polystyrene free from removal of fibers and paper powder during transportation. CONSTITUTION:Thermally expandable microcapsules comprising an acrylonitrile- based resin as a wall material is heated to give hollow particles, which are mixed with a vinyl acetate-based resin-containing emulsion by ultrasonic wave to form a solution of mixing he hollow particles. The solution of mixing the hollow particles is added to a pulp slurry and uniformly mixed so as to give 5-10wt.% of the hollow particles based on the pulp. The mixture is poured into a mold of a fixed shape, dehydrated and dried to form a premolded article, which is dipped in a coating solution for forming a biodegradable surface protecting layer composed of a water-soluble polysaccharide such as chitosan and dried to give the objective molded article of pulp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulp-molded article containing pulp as a main component, which is useful as a substitute material for expanded polystyrene.

[0002]

2. Description of the Related Art Conventionally, styrofoam having excellent cushioning properties has been used as a packaging material for electric equipment such as televisions, video decks, and cassette tape recorders.

However, a molded packaging material made of styrofoam will not be soiled if it is buried when it is discarded, and toxic gas will be generated if it is incinerated. Therefore, the disposal method becomes a global environmental problem.

Therefore, in recent years, there has been a demand for the development of a pollution-free molded article of packaging material, which replaces the Styrofoam molded article.
As one of them, a molded product made from pulp molding material, which is mainly made of waste paper such as newspaper, is drawing attention.

Such a pulp-molded product is a vinyl acetate-based resin in order to increase the water resistance of the pulp-molded product, if necessary, by adding a pulp slurry obtained by treating waste paper such as newspapers by a conventional method. Is prepared by pouring the obtained slurry into a mold and dehydrating and drying.

However, such a pulp-molded product has a problem that it has a low cushioning property as compared with a Styrofoam molded product and is not suitable as a packing material for heavy goods such as a video deck and a television.

Therefore, in order to improve the cushioning characteristics of the pulp molded product, there has been proposed a pulp molded product in which hollow particles which are crushed by compression and absorb compressive stress are mixed (Japanese Patent Laid-Open No. 6-10300). Gazette). Here, as the hollow particles, the polymer of the outer shell covers the hydrocarbon of the inner shell, and the polymer of the outer shell is softened by heating and the hydrocarbon of the inner shell is gasified, and the volume expands to several tens of times. Expanded particles (heat-expandable microcapsules) are preferably used.

[0008]

However, the pulp molded product disclosed in Japanese Unexamined Patent Publication (Kokai) No. 6-10300 is loaded with a heavy item to be packed such as a video deck, and it is subjected to a vibration test. In that case, there is a problem that fine particles such as paper powder fall off from the surface of the molded product and adhere to the surface of the product to be packaged or to an electronic substrate inside the product to be packaged.

The present invention is intended to solve the problems of the prior art as described above, has the same cushioning characteristics as those of the Styrofoam molded product, and does not generate dust such as paper powder during transportation or vibration. An object is to provide a pulp molded product.

[0010]

The present inventors have found that the above object can be achieved by providing a surface protective layer on the surface of a pulp molded product containing pulp and hollow particles, and completed the present invention. Came to let.

That is, the present invention provides a pulp mold molded article containing pulp and hollow particles, characterized in that a surface protective layer is formed on the surface thereof.

The present invention will be described in detail below.

The pulp mold-molded product of the present invention is characterized in that a surface protective layer is formed on the surface thereof. This surface protective layer prevents fine particles such as paper powder from peeling off from the surface of the pulp mold molded product even when the product to be packed is mounted on the pulp molded product and transported or vibrated.

Such a surface protective layer can be formed from various materials as long as it does not impair the buffering characteristics of the pulp molded product and can form a thin film. For example, polyolefin resin coating agent, vinyl acetate resin coating agent, water-soluble polysaccharide coating agent,
An acrylic resin coating agent or the like can be used. These can be used in the form of a solution dissolved in an organic solvent or an emulsion emulsified in an aqueous medium.

The surface protective layer can be formed by a conventional method, for example, by spraying the above-mentioned coating agent on a pulp mold-molded product and drying it to form a film,
A film can be formed by dipping a molded product in a liquid coating agent and drying.

From the viewpoint of suppressing an increase in compressive stress that deteriorates the cushioning characteristics of the pulp molded product, among the above-mentioned materials for forming the surface protective layer,
It is preferable to use a polyolefin-based coating agent or the like, which has a relatively low degree of hydrogen bonding with the cellulose constituting the pulp. However, from the viewpoint of consideration for environmental problems, it is more preferable to use a biodegradable material even if the compressive stress is slightly increased. As such a biodegradable material, water-soluble polysaccharides such as chitosan can be preferably exemplified. The term "biodegradable" as used herein means the property of being degraded by organisms and microorganisms existing in nature.

The thickness of the surface protective layer is not particularly limited and can be appropriately determined as needed.

Next, the pulp mold material composition used for producing the pulp mold molded article of the present invention will be described.

The pulp mold material composition contains pulp as main components and hollow particles or thermally expandable microcapsules described later. As the pulp used in such a composition, the same pulp as that used in conventional pulp mold-molded products can be used. For example, pulp obtained from waste paper such as newspaper can be used, and in this case, a small amount of components such as the binder contained in the waste paper may remain.

On the other hand, the hollow particles remarkably improve the cushioning property of the pulp molded product of the present invention. Further, since the hollow particles have a low specific gravity, the pulp mold-molded product of the present invention is lighter than the conventional pulp mold-molded product.

As the hollow particles used in the present invention, the polymer of the outer shell covers the hydrocarbon of the inner shell, the polymer of the outer shell is softened by heating, and the hydrocarbon of the inner shell is gasified, and the volume thereof is several. Particles that expand ten times (thermally expandable microcapsules) may be heated to form hollow particles. As such hollow particles, it is preferable to use those whose outer shell has excellent elasticity, absorbs stress well, and has a heat deformation temperature of 130 ° C. or higher and good heat resistance. More specifically, for example,
Thermally expandable microcapsules (particle size distribution: 10) in which an organic solvent having a boiling point of 50 to 100 ° C. such as isobutane, pentane, petroleum ether, and hexane is wrapped with a thermoplastic resin such as vinylidene chloride, acrylonitrile, acrylic acid ester, and methacrylic acid ester. ~ 30 μm), 100 ~
Heat to 150 ℃ for a short time to increase the diameter 4-5 times and the volume to 50
Hollow particles (true specific gravity 0.015 to 0.025, particle size distribution 10 to 2) that are expanded by 100 times and elastically deformed.
00μm, average particle size 100μm or less, pressure resistance 300Kg
/ Cm ² or more) can be preferably used.

Further, when such a heat-expandable microcapsule is used in the production of the pulp molded article of the present invention, it may be expanded in advance to be hollow particles before being mixed with the pulp, and may be expanded after being mixed with the pulp. It may be hollow particles.

The blending amount of the hollow particles can be appropriately determined according to the kind of pulp used and the like. Usually, the blending effect of 2% by weight or more with respect to the pulp is effective in improving the cushioning property of the pulp molded product, but it is 5 to 10
It is preferable to set the weight%. Further, as will be described later, when a foaming agent is used in the production of a pulp molded product, the amount of hollow particles can be further reduced.

The pulp mold material composition used in the present invention may contain various additives, if necessary, in addition to the above-mentioned pulp and hollow particles.

For example, a pulp plasticizer may be blended in order to improve the cushioning characteristics of the pulp molded product.
As such a pulp plasticizer, for example, glycerin or the like can be used. The blending amount of the pulp plasticizer such as glycerin depends on the properties required according to the application of the pulp molded product, the type of the pulp to be used, other blending components, etc., but is usually 5 to 50 with respect to the pulp. It is preferable to set the content to 10% by weight, and in particular, when a binder or a non-pulp natural fiber having a fiber length of 10 mm or more is blended in the pulp mold material composition as described below, the blending amount of the pulp plasticizer such as glycerin is 10 to 10. It is preferably 20% by weight. If the amount is too small, the compounding effect does not appear, and if the amount is too large, the water resistance of the pulp molded product decreases.

Further, the pulp mold material composition used in the present invention may be blended with a water resistance-imparting agent which reduces the moisture absorption rate of the pulp molded product. As such a water resistance-imparting agent, for example, a vinyl acetate-based resin conventionally used as a binder, a known internally added sizing agent, or the like can be used.

Generally, the internally added sizing agent is appropriately used depending on the pH of the solution used for papermaking. For example, a rosin-based sizing agent is known as a sizing agent used when papermaking is carried out in an acidic atmosphere by adding aluminum sulfate, but in the present invention, such a rosin-based sizing agent is particularly used as a water resistance-imparting agent. Preference is given to using. That is,
Since the rosin-based sizing agent is a biodegradable substance synthesized from natural pine resin, it is preferable to use it in comparison with non-biodegradable synthetic resin from the viewpoint of suppressing environmental pollution at the time of discarding the pulp molded product. it can. In addition, since the pulp mold-molded product using the rosin-based sizing agent can be dispersed again in water and reused after use, environmental pollution due to waste can be reduced also from this point, which is preferable. Furthermore, the rosin-based sizing agent is preferable because it has a high adsorptivity to pulp and the moisture absorption rate of the pulp molded product can be reduced by adding a very small amount.

As the rosin-based sizing agent, rosin (containing abietic acid (main component), parastrinic acid, neoabietic acid and levopimaric acid) obtained by steam distillation of pine resin is maleated or fumarized, and To be a reinforced rosin sizing agent (for example, Arakawa Chemical Co., size pine E, size pine C) or emulsified emulsion rosin sizing agent (for example, Arakawa chemical size pine N) Are known, but any of them can be used in the present invention.

The content of the rosin-based sizing agent is usually preferably 0.5 to 5.0% by weight based on the pulp. Further, in order to improve the adsorptivity of the rosin-based sizing agent to the pulp, it is usually preferable to use aluminum sulfate in an amount of 2 to 3% by weight based on the pulp in addition to the rosin-based sizing agent.

The pulp mold material composition used in the present invention may contain various binders in order to improve the strength of the pulp molded product. Further, as described below, when a foaming agent is used in the production of a pulp mold molded article in order to reduce the amount of hollow particles to be used, by mixing a binder, the gas generated by the foaming agent is added to the pulp mold molded article. It is preferable because it can be effectively used for forming voids inside.

The type of binder that can be used is not particularly limited, and various coating agents for forming the above-mentioned surface protective layer can be diverted. In this case, it is preferable to use a biodegradable binder because of the problem of environmental pollution at the time of discarding the pulp molded product. Among biodegradable binders, in particular, polysaccharides having basic nitrogen such as chitosan have a large hydrogen bonding ability with cellulose of pulp,
It can be preferably used because the breaking strength can be remarkably improved.

The content of such a polysaccharide is usually preferably 2 to 10% by weight based on the pulp. If it is too small, the compounding effect does not appear, and if it is too large, the drying time of water required for the production of a pulp molded product increases and the cost also increases, which is not preferable.

The pulp mold material composition of the present invention preferably contains fibers having a fiber length of 10 mm or more in order to improve the extensibility of the pulp molded product.
That is, the pulp fiber, which is the main raw material of the pulp mold material composition used in the present invention, usually has a fiber length of 2 to 10 mm.
It is preferable that the fibers contain 0 mm or more. For this purpose, it is preferable to blend non-pulp fibers having a fiber length of 10 mm or more. Further, as such non-pulp fibers, natural fibers should be used because of the problem of environmental pollution at the time of discarding pulp molded products. Is preferred. As such non-pulp natural fiber, for example, Manila hemp can be preferably used.

The amount of the non-pulp natural fiber having a fiber length of 10 mm or more is usually preferably 5 to 30% by weight based on the pulp. If it is too small, the compounding effect does not appear, and if it is excessively compounded, the effect corresponding to the compounding amount cannot be obtained.

The pulp mold molded product of the present invention can be molded by a conventional method. For example, the pulp and hollow particles as described above, or a slurry-like pulp mold material composition further containing various blending components as necessary, is prepared, put into a mold, dried and molded, the surface thereof It can be produced by forming a surface protective layer by a conventional method.

In this case, in order to further improve the cushioning characteristics of the pulp molded product, it is preferable to use a foaming agent to form voids inside the molded product. This makes it possible to reduce the blending amount of hollow particles and reduce the material cost of the pulp molded product.

As the foaming agent, those having a foaming temperature of 150 ° C. or lower and having a non-toxic residue after foaming are preferable. Examples of such a foaming agent include azodicarbonamide added with a foaming catalyst (manufactured by Sankyo Kasei, Selmac CAP, etc.),
Azobisbutyronitrile (AIBN), baking soda, etc. can be used. Usually, the amount of the foaming agent used is preferably 2 to 4% by weight based on the pulp. If the amount is too small, the effect of using the foaming agent does not appear, and even if it is used in excess, the effect corresponding to the amount used cannot be obtained, which is not preferable. When a foaming agent is used, it is preferable to use a relatively large amount of binder such as chitosan because the voids can be formed efficiently.

[0038]

In the pulp mold-molded product of the present invention, as shown in the schematic view of the SEM photograph shown in FIG. 1 (a), a hollow hollow cell having a spherical independent cell structure having a void 2a in a material made of pulp 1. The particles 2 are present, and the surface protection layer 3 is formed on the surface of the molded product. This surface protection layer 3
This makes it possible to prevent fine particles such as paper dust from falling off the surface of the pulp mold molded product even when the product to be packed is mounted on the pulp mold molded product and transported or vibrated.

The voids 2a of the hollow particles 2 of the pulp molded product of the present invention are compressed and crushed when the pulp molded product is impacted as shown in FIG. Therefore, the impact is absorbed by the hollow particles 2, and the pulp molded product of the present invention has excellent cushioning properties.

[0040]

EXAMPLES The present invention will be described in detail below based on examples.

Examples 1 to 4 and Comparative Example 1 In an emulsion (made by Kuraray Co., Ltd.) containing 5% by weight of vinyl acetate-based resin with respect to pulp, 10% by weight of hollow particles with respect to pulp was ultrasonicated. Mix and mix with the pulp slurry prepared from waste paper (solid content 24%)
By uniformly mixing and, a pulp mold material slurry was obtained. This slurry was added to an 8 mm camcorder (TR
55, manufactured by Sony Corporation), put into a mold for a pulp mold, dehydrated, and dried at 100 ° C. to obtain a preformed product. This pre-molded product corresponds to the pulp mold-molded product of Comparative Example 1.

As the hollow particles, heat-expandable microcapsules (F-80S manufactured by Matsumoto Yushi Co., Ltd.) using acrylonitrile resin as a wall material are preheated to 160 ° C. and expanded to an average particle size of 100 μm or less. I used the one.

Next, on the surface of the obtained pre-molded article, Table 1
A pulp mold-molded article was manufactured by applying the coating agent for forming the surface protective layer shown in 1 above by dipping and drying.

[0044]

[Table 1] Examples Coating agent Usage (g / m ² ) 1 Polyolefin coating agent 10 (Brighton XMO2, manufactured by Sakata Inx Co., Ltd.) 2 β, 1,3-linked polysaccharide coating agent 10 (Biopoly, manufactured by Takeda Pharmaceutical Co., Ltd.) 3 Basic Polysaccharide (Chitosan) Coating Agent 10 4 Acrylamide Coating Agent 10 (Evaluation) Obtained Molded Articles (Examples 1 to 4 and Comparative Example 1)
On the other hand, an 8 mm camcorder (TR55, manufactured by Sony Corporation) was actually wrapped in a dedicated sheet and mounted, and a transportation test was conducted under the following conditions.

Low temperature and low humidity transportation test (transportation equivalent to dry season in winter)
(Test) First, the pulp mold-molded product was placed in a test chamber set to an environmental condition of 20 ° C. and 65% RH and left for 24 hours.
After that, the environmental conditions of the test room are kept at 10 ° C. for 10 hours and 10 hours.
% RH. The state is maintained for 24 hours, and the vibration load test (condition: vibration wave component 5 to 50H
z; power spectrum density 0.015 G / Hz; overall effective value 0.83 G) was performed for 1 hour. 24
After 2 hours, set the environmental conditions in the test room at 20 ° C, 6 hours for 2 hours.
It was returned to 5% RH and left for 24 hours. Then, an 8 mm camcorder was taken out from the pulp molded product, and the surface thereof was visually observed and evaluated for the paper powder and the fibers that had fallen off the surface of the pulp molded product and the like.
The results are shown in Table 2.

In Table 2, "○" indicates the case where fibers or paper powder were not adhered or there was no problem in practical use even if adhered, and "X" was above a certain level of practical problems. It shows the case where fibers and paper powder are attached to the.

High temperature and high humidity transportation test (transportation equivalent to dry season in summer
(Test) First, the pulp mold-molded product was placed in a test chamber set to an environmental condition of 20 ° C. and 65% RH and left for 24 hours.
After that, the environmental conditions of the test room are kept at 60 ° C and 80 ° C for 3 hours.
% RH. The state was held for 24 hours, and during the holding, a vibration load test similar to the low temperature and low humidity transportation test was performed for 1 hour. After 24 hours, the environmental conditions in the test room were returned to 20 ° C. and 65% RH over 3 hours, and the test was left for 24 hours. Then, an 8 mm camcorder was taken out from the pulp molded product, and the surface thereof was visually observed and evaluated for the paper powder and the fibers that had fallen off the surface of the pulp molded product and the like. The results are shown in Table 2.

During the high temperature and high humidity holding, the molded product was dropped from a height of 0.6 m onto a flat concrete floor three times, and the degree of deformation of the molded product was visually observed and evaluated. As a result, the molded articles of Examples and Comparative Examples did not show any deformation that would pose a practical problem.

[0049]

[Table 2] As is clear from Table 2, the pulp mold-molded articles of the examples having the surface protective layer were able to substantially prevent the dropping of paper powder and fibers from the surface.

Next, the obtained molded articles (Examples 1 to 4 and Comparative Example 1) were subjected to a compression test as shown below to find the relationship between the compressive deformation rate and the compressive stress to obtain the surface protective layer. Was evaluated for its effect on buffering properties.

Compression test A test piece of 20 × 20 × 10 (thickness) mm was cut out from each molded product, and a compression tester (NMB, manufactured by Keiaisha Co., Ltd.)
Was tested. In this case, the compression speed is 5 mm /
It was set to min. The relationship between the obtained compressive deformation rate and compressive stress is shown in FIG. In addition, from this test result, the compression deformation rate was 5
The compressive stress at 0% was determined, and the results are shown in Table 3. In this case, an increase in compressive stress means that the molded product becomes hard and the cushioning effect decreases.

[0052]

[Table 3] From the results shown in FIG. 2 and Table 3, the molded product of each example in which the surface protective layer was formed showed a tendency that the compressive stress increased as compared with the molded product of Comparative Example 1 having no surface protective layer. The rate of increase was 20% or less, and it was found that there was no practical problem.

[0053]

Industrial Applicability The pulp mold-molded product of the present invention has the same cushioning characteristics as the Styrofoam molded product and does not generate dust such as paper powder during transportation or vibration.

[Brief description of drawings]

FIG. 1 S of the surface portion of the pulp mold-molded product of the present invention
It is a schematic diagram of the EM photograph (the same figure a), and a schematic diagram of the SEM photograph when the molded product is impacted (the same figure b).

FIG. 2 is a diagram showing a relationship between a compressive deformation rate and a compressive stress of a pulp molded product.

[Explanation of symbols]

 1 Pulp 2 Hollow Particles 2a Voids 3 Surface Protection Layer

Claims (6)

[Claims] 1. A pulp mold molded article containing pulp and hollow particles, wherein a surface protective layer is formed on the surface of the pulp mold molded article. 2. The pulp mold molded article according to claim 1, wherein the surface protective layer is formed of a biodegradable material. 3. The pulp mold molded article according to claim 2, wherein the biodegradable material is a water-soluble polysaccharide. 4. The water-soluble polysaccharide is chitosan.
Pulp molded article described. 5. The pulp molded product according to claim 1, wherein the hollow particles are heat-expandable microcapsules. 6. The pulp mold-molded product according to claim 5, wherein the hollow particles are contained in an amount of 5 to 10% by weight based on the pulp.