JP2012071617A - Method of manufacturing compression molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a compression molded product which does not use petroleum-based resin or reduces use amount of petroleum-based resin, has high mechanical strength and uses a plant material suitable for a casing of electronic equipment.SOLUTION: First, wooden chips are treated to have a predetermined shape. Next, while the treated wooden chips are heated, pressure is applied, so as to precipitate a plant-derived adhesion component from the wooden chips. Thus, the compression molded product having high mechanical strength and using the plant material suitable for the casing of the electronic equipment can be obtained.

Description

  The present invention relates to a method for manufacturing a compression molded product using a plant such as wood or bamboo as a main raw material, and particularly relates to a method for manufacturing a compression molded product suitable for a housing of an electronic device.

  In recent years, fossil resources represented by petroleum have been consumed in large quantities, and there is a concern about the exhaustion of those fossil resources. In addition, it is pointed out that a large amount of carbon dioxide is generated with the large consumption of fossil resources, which causes global warming. Currently, petroleum-based resins are used in many products, but in view of the above-mentioned problems, the movement of using plant-based resins such as polylactic acid instead of petroleum-based resins has become popular worldwide.

  Polylactic acid is made from plants such as corn, and after disposal, it is decomposed into water and carbon dioxide by microorganisms in the soil. Also, when polylactic acid is incinerated, water and oxygen dioxide are generated. These carbon dioxides are taken into plants by photosynthesis and used for plant growth. In this way, plant-based resins such as polylactic acid are environmentally friendly and recyclable materials.

  In recent years, it has been proposed to use a plant-based resin such as polylactic acid in a casing of an electronic device such as a notebook personal computer (PC) or a mobile phone (for example, Patent Document 1). However, plant-based resins such as polylactic acid generally have high rigidity such as flexural strength, but they do not have sufficient impact resistance such as Izod impact strength and low heat resistance such as deflection temperature under load. It is difficult to use it for a housing of an electronic device. Therefore, formation of the housing | casing of an electronic device using resin which mixed vegetable resin and petroleum resin is examined (for example, patent document 2).

  In addition, as a member using plant material, there is a wood board (also called a particle board) (for example, Patent Documents 3 and 4). Wood boards are crushed wood, thin timber made of paper, or waste paper (hereinafter referred to as “crushed material”) impregnated with an adhesive (binder) and compressed and laminated. It is characterized by relatively hard and high rigidity. However, petroleum-based adhesives and solvents are used for the wood board, and there are cases where the ratio exceeds 30%. In addition, the wood board has a large variation in the size of the crushed material and the like, and is not suitable for precise processing. Furthermore, since the flame | frame property prescribed | regulated to UL specification is requested | required by the housing | casing of electronic devices, such as a notebook type personal computer, it is difficult to use a wooden board for the housing | casing of an electronic device as it is.

  As described above, conventionally, it has been difficult to produce a molded product having high strength and high processing accuracy using only plant materials, and many petroleum resins have been required even when plant materials are used. Therefore, there is a demand for a molded product that does not use petroleum-based resin or uses a small amount of petroleum-based resin, and a manufacturing method thereof.

JP 2001-244645 A JP 2006-182994 A Japanese Patent No. 2888153 Japanese Patent No. 2580522

  An object of the present invention is to provide a method for producing a compression molded product using a plant material that does not use petroleum resin or uses less petroleum resin, has high mechanical strength, and is suitable for a housing of an electronic device. It is to provide.

  According to one aspect of the present invention, a step of processing a piece of wood into a predetermined shape, and a pressure molding step of depositing a plant-derived adhesive component from the piece of wood by applying pressure while heating the piece of wood after processing A method for producing a compression-molded article having the above is provided.

  According to the one aspect described above, a compression molded product using a plant material having high mechanical strength and suitable for a housing of an electronic device can be obtained.

FIG. 1 is a flowchart showing a method for manufacturing a compression molded product according to the first reference embodiment. FIG. 2 is a schematic diagram showing a method of manufacturing a compression molded product according to the first reference embodiment in the order of steps. FIG. 3 is a perspective view showing an example in which the compression molded product according to the first reference embodiment is adopted as a casing part (lid part) of a notebook computer. FIG. 4 is a diagram showing an example in which the compression molded product according to the first reference embodiment is adopted as a casing component of a mobile phone. FIG. 5 is a flowchart showing a method for manufacturing a compression molded product according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First reference form)
FIG. 1 is a flowchart showing a method for manufacturing a compression molded product according to the first embodiment, and FIG. 2 is a schematic diagram showing the manufacturing method in the order of steps.

  First, wood or bamboo (hereinafter referred to as “wood” or the like) is pulverized as a raw material to obtain a pulverized product (hereinafter also referred to as “wood powder”) having a particle size (average particle size) of, for example, 5 to 100 μm ( Step S11). There are no particular restrictions on the type of wood or bamboo used as the raw material, but cedar (cedar), hinoki (cypress), beech, paulownia (kiri), persimmon (keyaki), persimmon (maple), mulberry (kuwa), It is possible to use bamboo grass, nara, bamboo core, skin or the like. A plurality of types of pulverized materials such as wood may be mixed and used.

  When creating a casing for an electronic device, it is preferable that the average particle diameter of the wood flour is 5 to 100 μm as described above in order to ensure processing accuracy and uniformity. However, depending on the application, the particle size may be out of this range.

  Next, as shown in FIG. 2 (a), wood powder is filled in the first mold 11, the mold temperature is set to 100 to 250 ° C., the pressure is set to, for example, 30 MPa to 300 MPa, and the first pressurization is performed. A molding process is performed (step S12). This first processing and molding step is a step of temporarily molding the wood powder into a loosely coupled state, and is performed under temperature and pressure conditions that can maintain the shape of the molded body. If the temperature condition and pressure condition in the first pressure molding process are too high, there arises a problem that it becomes impossible to impregnate the molded body with the flame retardant in the next flame retardant impregnation process. Hereinafter, the molded body molded in the first pressure molding process is referred to as a temporary molded body 12.

  Next, the temporary molded body 12 is taken out from the first mold 11, and the surface thereof is impregnated with a flame retardant (step S13). In this flame retardant impregnation step, the temporary molded body 12 may be immersed in the liquid flame retardant 13 as shown in FIG. Further, the surface of the temporary molded body 12 may be impregnated with the flame retardant by heating the flame retardant and bringing the vapor into contact with the temporary molded body 12. The flame retardant may be shallowly impregnated so that the concentration becomes the highest in the vicinity of the surface of the temporary molded body 12, and it is not necessary to penetrate the flame retardant to the center.

  As the flame retardant, for example, a boron-based aqueous solution can be used. Examples of the boron-based flame retardant include sodium polyborate (borate ion polymer salt) and zinc borate. Examples of flame retardants other than boron-based flame retardants include organic flame retardants such as phosphate esters or triazine compounds. Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, ammonium polyphosphate, and the like. Moreover, as a triazine compound, a melamine cyanurate, a tris isocyanurate, etc. can be used, for example.

  Next, as shown in FIG. 2 (c), a temporary molded body 12 having a surface impregnated with a flame retardant is placed in the second mold 14, and the first molding is performed under conditions higher than those in the first pressure molding step. 2 is performed. The mold temperature in the second pressure molding process is, for example, 160 to 250 ° C., and the molding pressure is, for example, 50 to 500 Pa (step S14).

  In the second pressure molding step, components such as lignin and hemicellulose are precipitated from the wood powder constituting the temporary molded body 12 in a softened state. These components function as a natural adhesive (binder), and the wood powder in the second mold 14 is firmly bonded and integrated with each other, whereby a compression molded product 15 having a predetermined shape is obtained. The mold temperature and the molding pressure in this second pressure molding process may be appropriately determined according to the type and application of the wood used as the raw material, but as described above, the component that becomes the adhesive precipitates from the wood powder. It is necessary to set the temperature and pressure at which the wood flour in the mold is integrated.

  Next, as shown in FIG. 2D, the compression molded product 15 is taken out from the second mold 14. The compression molded product 15 manufactured in this way has high mechanical strength and good dimensional accuracy. It is also possible to make the specific gravity 1 or less. Furthermore, since only plants are used as raw materials, the burden on the environment is small. Furthermore, it has the property that it is hard to burn by containing a flame retardant.

  In order to further improve the rigidity of the compression molded product 15, an inorganic material such as carbon fiber, glass fiber, glass frame, glass bead, talc or mica is added to the raw wood flour. May be. In place of these inorganic materials, plant fibers such as kenaf or manila hemp may be added. In addition, plasticizer, weather resistance improver, antioxidant, heat stabilizer, light stabilizer, UV absorber, lubricant, mold release agent, pigment, colorant, antistatic agent can be added to the raw wood powder as necessary. Agents, fragrances, foaming agents, antibacterial agents, antifungal agents and the like may be added. In selecting these additives, it is preferable to select an additive that is harmless to living organisms and does not generate toxic gas by combustion, and that has a low environmental load.

  Furthermore, you may mix petroleum-type resin etc. with the wood flour used as a raw material as needed. However, in that case, considering the environmental load, the ratio of the plant-based material should be 25% or more, more preferably 50% or more.

  According to the present embodiment, it is possible to effectively use waste materials generated during wood processing, bamboo that is generated in large quantities, and the like. Moreover, according to this reference form, since a compression molding product can be manufactured only with plant material or only with plant material and a small amount of additives, it is possible to leave the texture of wood in the compression molding product or to reduce the specific gravity to 1 or less. Is possible. Furthermore, the compression molded product produced according to the present embodiment has high mechanical strength, good dimensional accuracy, light weight and flame resistance, so that it can be used for electronic devices such as notebook computers and mobile phones. Suitable for the body. FIG. 3 shows an example in which the compression molded product according to the present embodiment is adopted as a casing part (lid part) of a notebook computer. FIG. 4 shows an example in which the compression molded product according to the present embodiment is adopted as a casing component for a mobile phone.

  Hereinafter, the result of actually manufacturing a compression molded product by the method of this embodiment and examining the characteristics thereof will be described.

(Preparation of test piece)
First, the bending test piece prescribed | regulated to the industry standard of American Society for Testing and Material (ASTM) was produced by the method mentioned above. That is, Akita cedar was pulverized as a raw material to obtain wood flour having an average particle size of about 10 μm. This wood powder is filled into a first mold, and the first pressurization is performed under the conditions of a molding temperature of 160 ° C., a molding pressure of 30 MPa, and a press time of 3 minutes using a heat press manufactured by Sansho Industry. A pressure molding process was performed to obtain a temporary molded body.

  Next, the temporary molded body was taken out from the first mold and immersed in an aqueous solution (flame retardant) of sodium polyborate for 10 minutes to impregnate the surface with the flame retardant. Thereafter, the temporary molded body was put in a drying furnace and dried.

  Next, the temporary molded body is put into a second mold, and a second pressurization is performed using a heating press manufactured by Sansho Industry Co., Ltd. under conditions of a molding temperature of 200 ° C., a molding pressure of 100 MPa, and a press time of 3 minutes. A pressure forming process was performed. Thus, an ASTM bending test piece (compression molded product) having a size of 12.7 mm × 64 mm × 3.2 mm was obtained.

(Measurement of bending strength)
Next, the bending strength was measured using the bending test piece. Specifically, a universal testing machine (INSTORON5581) manufactured by Instron was used, and the flexural modulus was measured according to Japanese Industrial Standard (JIS K 7203) except for the size of the test piece. In addition, after preparing five bending test pieces and measuring the flexural modulus of each of these test pieces, the average value is calculated by excluding the maximum and minimum values in accordance with the standard for flexural modulus measurement. It was adopted as the flexural modulus.

  As a result, the bending elastic modulus of the test piece produced according to the first reference embodiment was 6 GPa. Generally, the casing material of an electronic device is required to have a flexural modulus of 3 GPa to 6 GPa, and a compression molded product manufactured according to the first reference form is required for the casing of the electronic device from the above test. It was confirmed to have a bending elastic modulus.

(Measurement of flame retardancy)
Next, based on the flame retardancy test of UL94 standard, the flame retardance of said test piece produced by the 1st reference form was investigated. That is, the test piece was supported vertically, a flame of a gas burner was applied to the lower end of the test piece and held for 10 seconds, and then the flame of the gas burner was separated from the test piece. When the flame disappeared, the gas burner flame was immediately applied to the test piece for 10 seconds.

  In the UL94 standard, the total of the flammable combustion duration after the first and second flame contact, the flammable combustion duration and the flameless combustion duration after the second flame contact, and the presence of five test pieces. The total flame combustion duration and the presence or absence of combustion drops (drip) are examined, and the grade (V-0, V-1, V-2) is determined based on the result.

  Grade V-0 is that the flaming combustion time after the first and second flame contact is within 10 seconds, and the total of the flammable combustion duration and the flameless combustion time after the second flame contact. Is within 30 seconds, the total flame burning time of the five test pieces is within 50 seconds, and there is no burning fallen object.

  Grade V-1 is that the flaming combustion time after the first and second flame contact is within 30 seconds, the flaming combustion duration and the flameless combustion time after the second flame contact, Is required to be within 60 seconds, the total flaming combustion time of the five test pieces must be within 250 seconds, and there should be no combustion drops.

  Furthermore, the grade V-2 is that the flaming combustion time after the first and second flame contact is within 30 seconds, the flammable combustion duration and the flameless combustion time after the second flame contact, Is required to be within 60 seconds, and the total flame burning time of the five test pieces is required to be within 250 seconds. In grade V-2, combustion drops are allowed. In addition, when a test piece burns out, it does not correspond to any of the grades V-0, V-1, and V-2.

  As a result of carrying out the flame retardant test of UL94 standard, the test piece produced according to the first reference form immediately disappears when the burner is released even if the flame of the gas bar bar is applied, and no combustion drops are generated. It was confirmed to have flame retardancy equivalent to V-0.

(Second reference form)
FIG. 5 is a flowchart showing a method for manufacturing a compression molded product according to the second embodiment.

  First, wood or bamboo as a raw material is pulverized to obtain a pulverized product having an average particle diameter of about 500 μm (step S21).

  Next, the surface of the pulverized material is impregnated with a flame retardant (step S22). For example, the pulverized product is immersed in an aqueous solution of a boron-based flame retardant, and the surface of the pulverized product is impregnated with the flame retardant. In this case, the flame retardant may be shallowly impregnated on the surface of the pulverized material, and the time for immersing the pulverized material in the flame retardant may be short.

  Next, the pulverized material impregnated with the flame retardant is placed in a mold, and a pressure molding process is performed (step S23). The mold temperature in this pressure molding step is, for example, 160 to 250 ° C., and the molding pressure is, for example, 50 to 500 Pa. In this pressure molding process, components such as plant-derived lignin and hemicellulose are precipitated from the pulverized product of wood or bamboo in a softened state, and these components work as an adhesive to integrate the pulverized product in the mold. Thus, a compression molded product having a predetermined shape is obtained. Thereafter, the compression molded product is taken out from the mold. In this way, a compression molded product is completed.

  In this reference form, pulverized wood or bamboo is used as a raw material, but carbon fiber, glass fiber, vegetable fiber, plasticizer, weather resistance improver, antioxidant is added to the pulverized wood or bamboo. An agent, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a lubricant, a release agent, a pigment, a colorant, an antistatic agent, a fragrance, a foaming agent, an antibacterial agent or an antifungal agent may be added as a raw material.

  Also in the compression molded product manufactured by this reference form, since only plants or only plants and a small amount of additives are used as raw materials, the burden on the environment is small. Moreover, since the compression molded product manufactured by this reference form contains the flame retardant, it has the property of being hard to burn.

(Embodiment)
In each of the first and second reference embodiments described above, a case has been described in which a plant pulverized product is put in a mold and compression molded to produce a compression molded product. Alternatively, using the cut wood pieces, the wood pieces are compressed while being heated to deposit plant-derived adhesive components such as lignin and hemicellulose to produce a compression-molded product as a product. In this case, plant fibers are firmly joined by the plant-derived adhesive component, and a compression-molded product having high strength can be obtained. In addition, petroleum-based resin or the like is unnecessary, and the burden on the environment is small.

  DESCRIPTION OF SYMBOLS 11 ... 1st metal mold | die, 12 ... Temporary molded object, 13 ... Flame retardant, 14 ... 2nd metal mold | die, 15 ... Compression molding product.

Claims (1)

Processing a piece of wood into a predetermined shape;
A pressure molding step of depositing a plant-derived adhesive component from the wood piece by applying pressure while heating the wood piece after processing.

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