WO2007088920A1

WO2007088920A1 - Exterior structure member for electronic device, and electronic device having the exterior structure member

Info

Publication number: WO2007088920A1
Application number: PCT/JP2007/051672
Authority: WO
Inventors: Shinichi Kanazawa; Yoshito Sakamoto; Shouhei Okabe; Kiyoshi Kawano; Satoshi Yamasaki; Shun Kayama; Yukiko Shimizu
Original assignee: Sumitomo Electric Fine Polymer, Inc.; Sony Corporation
Priority date: 2006-02-02
Filing date: 2007-02-01
Publication date: 2007-08-09
Also published as: JPWO2007088920A1; TW200732403A

Abstract

Disclosed is an exterior structure member for an electronic device, which is produced by mixing a biodegradable polyester with at least a polyfunctional polymer, kneading the mixture, molding the kneaded product into a predetermined shape, and irradiating the molded product with an ionizing radiation at a radiation dose amount of 50 to 200 kGy (inclusive) to cause the crosslinking to such a degree that the gel fraction of the biodegradable polyester becomes 50 to 90% (inclusive).

Description

Exterior member for electronic device, and electronic device provided with the exterior member

Technical field

TECHNICAL FIELD [0001] The present invention relates to an exterior member for an electronic device, and is particularly preferably used as a cap or casing for an external connection terminal of a mobile phone or the like, and aims to reduce the amount of waste at the time of disposal after use. is there.

Background art

[0002] An opening for an external connection terminal is provided in a housing of a portable device such as a mobile phone, a portable CD player, a video camera, etc., and a cap (or a cover) integrally formed with rubber resin. Is attached. For example, in Japanese Patent Laid-Open No. 2002-111240 (Patent Document 1), the cap is made of a resin such as ABS (acrylonitrile butadiene styrene), PCZABS (polycarbonate Z acrylonitrile butadiene styrene), PA (polyamide), PC (polycarbonate). It is disclosed to form.

Similarly, for housings of mobile devices such as mobile phones, portable CD players, and video cameras, ABS (acrylonitrile butadiene styrene), PCZABS (polycarbonate Z acrylonitrile butadiene styrene), PA (polyamide), Resins such as PC (polycarbonate) are widely used.

[0003] Patent Document 1: Japanese Patent Laid-Open No. 2002-111240

Disclosure of the invention

Problems to be solved by the invention

[0004] When the external connection terminal cap and the casing are made of resin as described above, a problem occurs when they are subjected to combustion disposal after use. In other words, global warming due to heat and exhaust gas generated during combustion, problems such as effects on food and health due to toxic substances in combustion gas and post-combustion residues, securing of disposal treatment disposal buried land, etc. Has become a social problem

[0005] In response to these problems, biodegradable polymers such as starch and polylactic acid have been attracting attention as materials for solving the problems of disposal of petroleum synthetic polymers. Material. Biodegradable polymers do not have a negative impact on the global environment, including ecosystems, because they produce less heat than combustion and maintain the cycle of decomposition and resynthesis in the natural environment. Among these, aliphatic polyester-based rosin, which has properties comparable to petroleum synthetic polymers in terms of strength and processability, has recently attracted attention.

[0006] In particular, polylactic acid is made from starch supplied from plants, and is currently becoming cheaper than other biodegradable polymers due to cost reduction due to mass production in recent years. Many studies have been made on applications.

Polylactic acid is the closest biodegradable resin to its alternative material because it has processability and strength comparable to general-purpose petroleum synthetic polymers in terms of its characteristics. In addition, it is expected to be applied to various applications such as its transparency, which is comparable to acrylic resin, and its high Young's modulus and its shape retention. The

[0007] However, polylactic acid has a glass transition point at a relatively low temperature of around 60 ° C, and the so-called glass plate suddenly becomes a Bühl tablecloth around that temperature. The rate is drastically reduced and it is difficult to maintain the shape.

Thus, a biodegradable resin molded product represented by polylactic acid is an effective material for disposal, but has a problem in terms of heat resistance. For example, portable devices are released into automobiles. If left unattended, the cabin temperature will rise to 60 ° C or higher at high temperatures in summer, and deformation may occur.

On the other hand, from the viewpoint of flexibility, polylactic acid, as described above, has a glass transition temperature of around 60 ° C and lower than the glass transition temperature at room temperature. There is a problem that the shaped product is easily damaged depending on the usage form.

[0008] The present invention has been made in view of the above problems, and can improve the heat resistance and strength of a molding material formed from a biodegradable material, maintain the shape even in a high temperature environment, and It has the flexibility to prevent damage at normal temperatures, and can be used as an external connection terminal cap for mobile phones made of biodegradable materials that are as strong as the currently used PCZABS, and for exterior components of electronic devices such as housings. The challenge is to provide.

[0009] Further, there is a problem associated with providing a highly flame-retardant material that is a characteristic necessary for an external connection terminal cap or an exterior member for a housing. Means for solving the problem

[0010] As a result of intensive research on this problem, the present inventor has solved this problem by mixing polyfunctional monomers into biodegradable polyester and cross-linking molecules under a certain condition by irradiation or the like. I found that it can be solved.

[0011] Based on the above knowledge, as a first invention, at least a polyfunctional monomer is mixed with the biodegradable polyester, and the gel fraction (gel content dry weight Z initial dry weight) of the biodegradable polyester is 50. Provided is an exterior member for an electronic device, characterized by having a cross-linked structure of at least 90% and at most 90%.

[0012] In addition, as a second invention, at least a polyfunctional monomer is mixed and kneaded with a biodegradable polyester, the kneaded product is molded into a required shape, and ionizing radiation is applied to the obtained molded product. Caps and housings for external connection terminals of mobile phones, characterized by being irradiated with an irradiation dose of OkGy or more and 200 kGy or less, and crosslinked so that the gel fraction of the biodegradable polyester is 50% or more and 90% or less The manufacturing method of exterior members, such as a body, is provided.

[0013] The biodegradable polyester used in the present invention includes, for example, ε poly force prolatatone or δ polylatatanes represented by polypuchi-mouth ratataton, succinic acid, adipic acid, sebacic acid, dartaric acid, decanedicarboxylic acid, terephthalic acid Copolymers of dicarboxylic acids typified by acid or isophthalic acid and polyhydric alcohols typified by ethanediol, propanediol, butanediol, octanediol, dodecanediol, etc., that is, polyethylene succinate, polybutylene Succinate, polybutylene adipate, polybutylene adipate terephthalate, etc., and a copolymer with polylactic acid added thereto, that is, polybutylene succinate lactide, polybutylene succinate adipate acetate, or poly In addition to polyhydroxycarboxylic acids such as richolic acid, polyhydroxybutyric acid, polyhydroxyvaleric acid or polyhydroxycabronic acid, polylactic acid with L-lactic acid power, D-lactic acid power polylactic acid, L-lactic acid and D-lactic acid Examples thereof include polylactic acid obtained by polymerizing the above mixture, and may be a mixture of two or more homopolymers and copolymers described above. In particular, many of the above-described biodegradable polyesters such as polybutylene succinate excluding polylactic acid alone have a glass transition temperature of room temperature or lower, and the present invention aims to maintain flexibility at room temperature. Use it properly! be able to. In particular, if these are the main components, polymers with a glass transition temperature below room temperature can dominate the overall strength, so the preferred glass transition temperature is 50-60 ° C, which exceeds the normal temperature. It is possible to add a part of a polymer or the like containing a certain polylactic acid alone as a component. The main component here refers to the case where the biodegradable polyester contains the most natural or petroleum-derived biodegradable polymer having a glass transition temperature of room temperature or lower. Furthermore, natural or petroleum-derived biodegradable polymers having a glass transition temperature of room temperature or lower are contained in 50 parts by weight or more in 100 parts by weight of biodegradable polyester, and biodegradable glass transition temperatures of polylactic acid and the like exceeding room temperature. It is preferable that the functional polymer is less than 50 parts by mass in 100 parts by mass of the biodegradable polyester. In the present specification, normal temperature refers to a normal temperature at which heating / cooling is not performed, and the biodegradable ¾ polymer such as polybutylene succinate, polybutylene succinate lactide, or polybutylene succinate adipate lactide is As described above, it may be either petroleum-derived or partly or entirely naturally-derived polymer.

The polyfunctional monomer is not particularly limited as long as it is a monomer that can be cross-linked by irradiation with ionizing radiation, such as triallyl isocyanurate, but it has two or more double bonds in one molecule. Acrylic and methacrylic polyfunctional monomers are preferably used.

Examples of this type of monomer include 1, 6 hexanediol di (meth) acrylate, 1, 4 butanediol di (meth) acrylate, trimethylol propane tri (meth) acrylate, ethylene oxide modified trimethylol propane Tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, ethylene oxide modified bisphenol A di (meth) acrylate, diethylene glycol di (meth) acrylate, dipentaerythritol hexa acrylate , Dipentaerythritol monohydroxypentaacrylate, force Prolataton-modified dipentaerythritol hexaatalylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, polyester Tylene glycol Di (meth) atalylate, Tris (Atari mouth kichetil) isocyanurate, Tris (methacryloxy) Ethyl) isocyanurate and the like.

[0015] The polyfunctional monomer used in the present invention is preferably blended in an amount of 2 to 15 parts by mass with respect to 100 parts by mass of the biodegradable polyester.

If it is less than 2 parts by mass, the cross-linking effect of the biodegradable polyester due to the polyfunctional monomer will not be sufficiently exerted, and the strength at high temperatures will decrease, and in the worst case, the shape will not be maintained. It depends. On the other hand, when the amount exceeds 15 parts by mass, it becomes difficult to uniformly mix the entire amount of the polyfunctional monomer with the biodegradable polyester, so that the bridge effect is not substantially different.

In order to ensure the shape maintaining effect at high temperatures, it is preferably 3 parts by mass or more. In order to increase the biodegradable polyester content and increase biodegradability, it is 10 parts by mass or less. Preferred.

[0016] Further, in addition to the biodegradable polyester and the polyfunctional monomer, other components may be combined with the composition constituting the molded product of the biodegradable polyester unless the object of the present invention is contrary. May be. For example, you may mix | blend biodegradable materials other than biodegradable polyester. Examples of biodegradable materials other than the biodegradable polyester include synthetic biodegradable resin such as polyvinyl alcohol, or natural biodegradable resin such as natural linear polyester such as polyhydroxypropylate valerate. Can be mentioned.

Further, a synthetic polymer having biodegradability and Z or a natural polymer may be mixed as long as the melting characteristics are not impaired. Examples of biodegradable synthetic polymers include cellulose acetate, cellulose acetate butyrate, cellulose alcohol propionate, cellulose nitrate, cellulose cellulose sulfate, cellulose acetate such as cellulose acetate butyrate or cellulose nitrate acetate, Polypeptides such as glutamic acid, polyaspartic acid or polyleucine can be mentioned. Examples of the natural polymer include starch, raw starch such as corn starch, wheat starch or rice starch, or processed starch such as acetate esterified starch, methyl ether starch or amylose.

[0017] Furthermore, it is preferable that 1 to 150 parts by mass of an inorganic filler or Z and a dye are blended with 100 parts by mass of the biodegradable polyester. In particular, when used as a housing, it is preferable to add an inorganic filler as a reinforcing material. In order to make the exterior member of the slave device, it is preferable to blend a dye or a pigment. Apply paint to the outer surface of the cross-linked molded product without blending dyes or pigments in the composition.

The blending amount of the inorganic filler or the Z and the dye is within the above range because if the amount is less than 1 mass with respect to 100 parts by mass of the biodegradable polyester, a reinforcing effect can be obtained by covering the inorganic filler. If it exceeds 150 parts by mass, it will lose flexibility and become brittle.

[0018] Examples of the inorganic filler include glass fiber, glass, beads, metal powder, talc, my strength, calcium carbonate, clay, wollastonite, silica, and the like. These may be used untreated or may be surface treated with silane or stearic acid.

Among the inorganic fillers, it is particularly preferable to use wollastonite.

[0019] Furthermore, it is preferable that the exterior member for an electronic device according to the present invention contains at least one of the following flame retardants (a) to (e).

(a) Phosphorus flame retardant, (b) Melamine flame retardant, (c) Metal hydrate, (d) Nitrogen flame retardant, (e) Silane flame retardant

[0020] Flame resistance is one of the important performance requirements for external connection terminal caps and exterior members for electronic devices such as housings. In the study by the present inventors, among the generally used flame retardants, in particular, one or more of the flame retardants (a) to () are blended to impart flame retardancy! / I like it! /

Examples of the phosphorus-based flame retardant (a) include condensed phosphate ester, phosphate ester, polyphosphate ammonium salt, intomescent, cyclic phosphate, and the like.

Examples of the melamine flame retardant (b) include melamine cyanurate,

As the metal hydrate (c), aluminum hydroxide and the like can be preferably used, and (d) nitrogen flame retardant, (e) silane flame retardant and the like can be suitably used.

These flame retardants (a) to (e) can be used alone, but as shown in the examples, different types of flame retardants can be used. It is effective in achieving both flame retardancy.

[0021] In addition, the composition includes a resin component other than biodegradable resin, a curable oligomer, Various stabilizers, hydrolysis inhibitors, antistatic agents, antifungal agents, polylactic acid crystallization accelerating nucleating agents, additives such as viscosity imparting agents, organic fillers, coloring agents such as dyes or pigments, etc. I'll do it with you.

[0022] A composition containing the above-described biodegradable polyester, polyfunctional monomer and optionally other components is formed into a desired shape.

A shaping | molding method is not specifically limited, You may use a well-known method. For example, known molding machines such as an extrusion molding machine, a compression molding machine, a vacuum molding machine, a blow molding machine, a T-die molding machine, an injection molding machine, and an inflation molding machine are used.

[0023] After the biodegradable polyester composition is molded into a required shape, the biodegradable polyester molded product is cross-linked, and the cross-linking method is not particularly limited, and a known method can be used. It is most preferable to irradiate with actinic radiation to crosslink.

As ionizing radiation, γ-rays, X-rays, β-rays or a-rays can be used, but for industrial production, γ-ray irradiation with cobalt 60 and electron beam irradiation with an electron beam accelerator are preferred. Ionizing radiation exposure removes air! It is preferable to carry out in an inert atmosphere or under vacuum. This is because when the active species generated by the irradiation of ionizing radiation are combined with oxygen in the air and deactivated, the crosslinking efficiency is lowered.

[0024] The dose of ionizing radiation is preferably 50 kGy or more and 200 kGy or less U.

Depending on the amount of polyfunctional monomer, the ability of crosslinking of biodegradable polyester is recognized even when the dose of ionizing radiation is lkGy or more and lOkGy or less. Almost 100% of biodegradable polyester is ionized to crosslink polyester molecules. It is preferable that the irradiation amount of the actinic radiation is 50 kGy or more. Furthermore, in order to complete the cross-linking integration, it is more preferable that the ionizing radiation dose is 8 OkGy or more.

On the other hand, the irradiation dose of ionizing radiation is 200 kGy or less because the biodegradable polyester has the property of being disintegrated by radiation when it is used alone, so if the irradiation dose of ionizing radiation exceeds 20 OkGy, it is opposite to crosslinking. This is because the decomposition will proceed. The upper limit of the dose of ionizing radiation is preferably 150 kGy, more preferably lOOkGy.

More preferably ί is 60kGy ~ 150kGy, especially 80kGy ~ 120kGy power ^ Preferred! / ヽ. [0025] Instead of crosslinking by irradiating with ionizing radiation, a polyfunctional monomer and a chemical initiator are mixed in a biodegradable polyester and then molded into a desired shape, and the chemical initiator is thermally decomposed. The biodegradable crosslinked body can also be produced by increasing the thickness.

As the polyfunctional monomer, the same substance as in the above embodiment can be used. Chemical initiators include dicumyl peroxide that generates peroxide radicals by thermal decomposition, propionitryl peroxide, benzoyl peroxide, tert-butyl peroxide, diacyl peroxide, pelargonyl peroxide, myristyl peroxide, Any catalyst that initiates the polymerization of monomers such as t-butyl perbenzoate or 2,2 'azobisisobutyoxy-tolyl peroxyacid catalyst can be used!

The temperature conditions for crosslinking can be appropriately selected depending on the type of chemical initiator. As in the case of irradiation, the crosslinking is preferably performed in an inert atmosphere or air except for air.

[0026] In the biodegradable fatty polyester molding material produced by the above-mentioned method, the gel fraction (gel content dry weight Z initial dry weight) is 50% or more and 90% or less by crosslinking. The In the present invention, the degree of crosslinking is defined by the gel fraction.

The gel fraction is obtained by wrapping a predetermined amount of irradiated or chemical crosslinked film in a 200 mesh wire net and boiling in N, N dimethylformamide (DMF) solution for 48 hours. Next, after removing the dissolved sol, the gel remaining in the gold-copper is dried at 50 ° C for 24 hours to determine its weight. The gel fraction is calculated by the following formula.

Gel fraction (%) = (gel dry weight) Z (initial dry weight) X 100

[0027] When the gel fraction is 50% or more in the cross-linked type, an infinite three-dimensional network structure is generated in the polymer, and heat resistance that does not deform even in a high temperature environment can be imparted. On the other hand, when the gel fraction exceeds 90%, it becomes too hard, lacks flexibility, and there is a problem that bending strength is lowered. The gel fraction is preferably 60-75%.

[0028] The molded product of the biodegradable polyester composition having a gel fraction of 50% or more and 80% or less by the crosslinking has a melting point of 150 ° C to 200 ° C, a flexural modulus of 600 to 2400 MPa, Young's modulus Can be imparted with a physical property of 500 to 2000 MPa and a Young's modulus retention at high temperatures of 70% or more. The invention's effect

[0029] The crosslinked body composed of the biodegradable polyester composition serving as the external member of the electronic device of the present invention can improve the heat distortion temperature of the biodegradable polyester by the effect of crosslinking. In other words, the cross-linking network of biodegradable polyester formed by cross-linking can reliably maintain the shape even at high temperatures.

In addition, since the present invention is molded with biodegradable resin, it can solve various problems associated with the disposal of conventional plastics that have very little impact on the ecosystem in nature.

In particular, when the exterior member of the electronic device according to the present invention is used in a detachable cap, cover material, housing, and housing, for example, an external connection terminal cap or housing of a mobile phone, damage is unlikely to occur. Strength is required. In this case, if a polymer having a glass transition temperature of room temperature or lower is used as the biodegradable polyester, there is an advantage that damage is caused because the flexibility is maintained at room temperature.

Brief Description of Drawings

[0030] FIG. 1 (A), (B), and (C) are drawings showing a mobile phone including a cap and a casing according to an embodiment of the present invention.

FIG. 2 is a drawing showing an electron beam irradiation process.

Explanation of symbols

[0031] 1 Mobile phone

2 opening

3 cap

4 Enclosure

BEST MODE FOR CARRYING OUT THE INVENTION

[0032] Embodiments of the present invention will be described below.

The exterior member of the electronic device of the present invention is used as a cap 3 that covers the opening 2 provided at the connection portion with the external terminal of the mobile phone 1 shown in FIG.

The cap 3 is molded from a heat-resistant biodegradable polyester composition and has the following properties. Manufactured according to the procedure.

[0033] As the biodegradable polyester, polybutylene succinate (hereinafter referred to as PBS) having a glass transition temperature of 32 ° C or lower is used. First, the force of softening PBS pellets by heating, or PBS Dissolve PBS in a soluble solvent.

Next, the biodegradable polyester is softened by heating, and a polyfunctional monomer is added. Trimethylolpropane trimetatalylate (TMPT) is added as a multifunctional monomer. The addition amount is 5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the biodegradable polyester. After the addition, the mixture is stirred and mixed so that the polyfunctional monomer is uniform.

Subsequently, the solvent may be further removed by drying.

[0035] The composition is softened again by heating or the like and formed into the shape of the cap 3.

The molding may be carried out after the composition has been prepared, for example, in the state of being dissolved in a solvent, or after cooling or drying and removal.

[0036] Next, the obtained biodegradable polyester molding is irradiated with ionizing radiation to crosslink the biodegradable polyester to obtain a heat-resistant biodegradable polyester. The ionizing radiation is appropriately selected according to the blending amount of the polyfunctional monomer, etc., within the range of 80 kGy to 150 kGy.

In particular, the gel fraction of the heat-resistant biodegradable polyester obtained after irradiation with ionizing radiation is selected based on 50% or more.

Next, a second embodiment will be described.

The exterior member of the electronic device of the second embodiment is used as the casing 4 of the mobile phone 1 shown in FIG. The casing 4 is molded from a heat-resistant biodegradable polyester composition as in the first embodiment, and is manufactured by the following procedure.

In the second embodiment, polybutylene succinate adipate lactide and polylactic acid (polybutylene succinate adipate lactide: polylactic acid) = (55 to 100 parts by mass: 0 to 45 parts by mass) as the biodegradable polyester In addition, it is different from the first embodiment in that it is mixed with a flame retardant or Z and an inorganic filler. As the flame retardant, use at least one of phosphoric acid ester which is a phosphorus flame retardant, melamine cyanurate which is a melamine flame retardant, and aluminum hydroxide which is a metal hydrate! / These are 100 parts by weight of the biodegradable polyester, 5 parts by weight of phosphate ester, 20 to 40 parts by weight of melamine cyanurate, and 100 to 120 parts by weight of aluminum hydroxide. is doing. In particular, by using a mixture of three types, both high flame retardancy and flexural elasticity can be achieved.

Further, as the inorganic filler, wollastonite is blended. The wollastonite is blended in an amount of 45 parts by mass with respect to 100 parts by mass of the biodegradable polyester.

By blending the flame retardant in this way, it can be suitably used in the case of an exterior member of an electronic device that requires flame retardancy, and by blending an inorganic filler, the strength required particularly as a casing can be obtained. It is out.

Other configurations and effects are the same as those of the first embodiment, and thus description thereof is omitted.

Example

[0038] The power of the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited to these examples.

[0039] (Example 1)

As the biodegradable polyester, polybutylene succinate “Pionore # 1020” manufactured by Showa Polymer Co., Ltd. was used.

TMP T, a kind of polyfunctional monomer, is finally added to the biodegradable polyester that has been melted and kneaded in advance at a cylinder temperature of 150 ° C using an extruder (PCM30, manufactured by Ikeji Iron Works Co., Ltd.). In particular, the mixture was adjusted by adding a small amount so as to be 5 parts by weight with respect to 100 parts by weight of the biodegradable polyester. The melt index MI (190 ° C X 2.16 kg) of the prepared mixture was 30.

The mixture was cooled and then pelletized with a pelletizer to obtain a pellet-like kneaded product of biodegradable polyester and polyfunctional monomer. The kneaded product was hot-pressed into a sheet at 150 ° C and then rapidly cooled with water to produce a sheet.

The sheet was irradiated with an electron beam at 60 kGy by an electron accelerator (acceleration voltage 10 MeV, current amount 12 mA) in an inert atmosphere excluding air to obtain a heat-resistant biodegradable polyester. Specifically, as shown in FIG. 2, the electron beam irradiation is carried out in a vacuum atmosphere by the high voltage in the high voltage accelerator 11 in which electrons emitted from the electron gun 10 are combined with a capacitor. After the direction is controlled by the polarizing coil 12, the molded product 20 is irradiated through the thin film 13 such as titanium.

Irradiation to the molded product 20 is performed stably with the same voltage and the same amount of current, and is therefore moved at a constant speed by the conveyor 15 or the like.

(Example 2)

The procedure was the same as Example 1 except that the electron beam irradiation dose was 120 kGy.

[Example 3]

As a biodegradable polyester, “Pionole # 1020X30” manufactured by Showa Polymer Co., Ltd., which is a polybutylene succinate containing 30% mineral filler, was used.

TMP T, a kind of polyfunctional monomer, is finally added to the biodegradable polyester that has been melted and kneaded in advance at a cylinder temperature of 150 ° C using an extruder (PCM30, manufactured by Ikeji Iron Works Co., Ltd.). In particular, the mixture was adjusted by adding a small amount so as to be 5 parts by weight with respect to 100 parts by weight of the biodegradable polyester. The melt index MI (190 ° C X 2.16 kg) of the prepared mixture was 38.

The sheet was irradiated with an electron beam at 60 kGy by an electron accelerator (acceleration voltage 10 MeV, current amount 12 mA) in an inert atmosphere excluding air to obtain a heat-resistant biodegradable polyester. (Example 4)

Example 3 was repeated except that the electron beam irradiation amount was 120 kGy.

[0042] (Comparative Example 1)

The procedure was the same as Example 1 except that the electron beam irradiation was not performed.

(Comparative Example 2)

Example 3 was the same as in Example 3 except that the electron beam irradiation was not performed.

[0043] (Evaluation of Examples 1 to 4 and Comparative Examples 1 and 2) In Examples 1 to 4 and Comparative Examples 1 and 2, the gel fraction was evaluated by the following method.

Further, a bending strength test was conducted according to ASTM D-790.

In addition, as an evaluation of heat resistance and hydrolyzability, the tensile strength before and after immersion for 4 days in 60 ° C or 80 ° C hot water was evaluated by Young's modulus. Furthermore, the water absorption rate and the combustion test were also evaluated.

[0044] (Evaluation of gel fraction)

After accurately measuring the dry weight of each Example and Comparative Example sample, wrap in a 200 mesh stainless steel wire, boil in N, N-dimethylformamide (DMF) solution for 48 hours, and then dissolve in DMF. The remaining sol was removed to obtain the remaining gel. After drying at 50 ° C. for 24 hours, DMF in the gel was removed, and the dry weight of the gel was measured. Based on the obtained value, the gel fraction was calculated based on the following formula.

Gel fraction (%) = (Dry weight of gel fraction Z Dry weight of sample) X 100

[0045] Melt index (Ml), flexural modulus (MPa), flexural strength (MPa), flexural fracture strength (MPa), Young's modulus (MPa), Young's modulus retention rate (%) of Examples and Comparative Examples The elongation (%) Z tensile strength (MPa) and water absorption are shown in Table 1 to Table 10 below.

Each measurement method is melt index (Ml) 〖IS K7210, ISO 1130 and AS TM D1238, gel fraction ί IS IS K7210 and ISO 527, flexural modulus, bending strength and bending fracture strength 〖IS The test was carried out in accordance with K7171, ISO 178 and ASTM D790, Young's modulus, elongation and tensile strength, IS K 7127, ISO 527 and ASTM D882, respectively.

In Tables 5 to 9, in terms of Young's modulus, Young's modulus retention, and elongation Z tensile strength, the original indicates the state before heating.

[0046] [Table 1]

Flexural modulus (MPa)

Comparative Example 1, 2 OkGy 431 1490 Example 1, 3 60 kGy 657 2391 Example 2, 4 120 kGy 657 2381 [0048] [Table 3]

Flexural strength (MPa)

One: Nylon does not break

[0049] [Table 4]

Bending fracture strength (MPa)

One: N

Five]

Young's modulus (MPa)

OkGy (Comparative Examples 1 and 2) 451 1225 Original 60kGy (Examples 1 and 3) 598 1509

120 ^ So (Example 2, 4) 598 1715

OkGy (Comparative Examples 1 and 2) 402 941

60 ° C hot water 4D 60kGy (Example 1, 3) 549 1519

120 kGy (Examples 2 and 4) 529 1597

OkGy (Comparative Example 1 and 2) 421 872

80 ° C hot water 4D 60kGy (Example 1, 3) 529 1 176

120 kGy (Examples 2 and 4) 539 1245 [0051] [Table 6] Young's modulus retention

[0052] [Table 7] Elongation (% tensile strength (MPa)

[0053] [Table 8] Elongation retention (%) Tensile retention (%)

9]

Elongation (%) Z Tensile Strength (MPa)

Ten]

Water absorption rate (%)

[0056] As shown in Table 1, the gel fractions of Examples 1 to 4 are 61 to 71%, whereas Comparative Examples 1 and 2 that were not subjected to electron beam irradiation were crosslinked. The gel fraction was 0% due to its remarkable nature.

As a result, as shown in Table 2, Examples 1 to 4 have a flexural modulus of 600 to 2400 MPa, while Comparative Example 1 has a 431 MPa of less than 600 MPa and was crosslinked by electron beam irradiation. Was confirmed to be excellent.

As shown in Table 5 to Table 8, the Young's modulus and the Yang's retention rate before and after immersion for 4 days in 60 ° C or 80 ° C hot water were compared to Comparative Examples 1 and 2 that did not perform electron beam irradiation. Thus, it was confirmed that Examples 1 to 4 irradiated with an electron beam showed excellent numerical values of deviation and excellent tensile strength.

With regard to the elongation Z tensile strength, Comparative Examples 1 and 2, which were not subjected to electron beam irradiation, had a large elongation ratio, V 抗, whereas the tensile strength was low.

Furthermore, as shown in Table 10, it was confirmed that the water absorption was less in Examples 1 to 4 than in Comparative Examples 1 and 2.

[0057] In the measurement of bending strength and bending fracture strength, the glass transition temperature (Tg) of the polybutylene succinate used was -32 ° C, and the normal temperature was higher than the glass transition temperature. Hold. Therefore, the sample of Example 2 was flexible and did not break. In addition, when crosslinked without electron beam irradiation, Comparative Examples 1 and 2 were flexible and did not break. Thus, it was confirmed that when polybutylene succinate is used even when crosslinked by electron beam irradiation, it has physical properties that are difficult to break in order to maintain flexibility.

[0058] (Example 5)

As biodegradable polyester, polybutylene succinate adipate lactide “GsPLa AZ91NT (trade name)” manufactured by Mitsubishi Chemical Corporation and polylactic acid “LAC EA” H-280 (trade name) manufactured by Mitsui Chemicals Co., Ltd. )"It was used. 10 parts by mass of Glacea H-280 per 100 parts by mass of GsPLa, 5 parts by mass of polyfunctional monomer TMPT, 5 parts by mass of phosphate ester as a flame retardant, and 40 parts by mass of melamine cyanurate, Example 5 was carried out in the same manner as in Example 1 except that the electron beam irradiation amount was 120 kGy.

(Example 6)

As a biodegradable polyester, 55 parts by mass of GsPLa and 45 parts by mass of Lacier H-280 are blended, and 100 parts by mass of the biodegradable polyester is kneaded with 45 parts by mass of wollastonite as an inorganic filler. Example 6 was made in the same manner as Example 1 except that

(Example 7)

Example 7 was carried out in the same manner as in Example 6 except that 120 parts by mass of hydroxyaluminum hydroxide was mixed with 100 parts by mass of the biodegradable polyester without blending wollastonite.

(Example 8)

Example 8 was carried out in the same manner as Example 7 except that 120 parts by mass of aluminum hydroxide and 20 parts by mass of melamine cyanurate and 5 parts by mass of phosphate ester were kneaded.

(Comparative Examples 3 and 4)

Comparative Examples 3 and 4 were made in the same manner as Examples 7 and 8 except that they were not able to perform electron beam irradiation.

[0059] Table 11 below shows the production conditions and gel fraction, bending strength test, heat resistance, hydrolyzability, and flame retardancy evaluation results of Examples 5 to 8 and Comparative Examples 3 and 4. Each evaluation was performed by the same measurement method as in the above example. For the evaluation of heat resistance and hydrolyzability, the original sample before heating was subjected to 80 ° C hot water for 24 hours (1 day), 120 ° C in air for 7 days, and 140 ° C in air for 7 days. This was carried out by measuring the elongation (%) and tensile strength (MPa) after standing under conditions. In addition, flame retardant evaluation was performed in accordance with UL94.

[Table 11]

[0061] As shown in Table 11, the gel fractions of Examples 5 to 8 were 77 to 88%, and crosslinking was confirmed. On the other hand, Comparative Examples 3 and 4 which were not irradiated with an electron beam had a gel fraction of 0% and were not crosslinked.

As a result, Examples 6-8 were able to maintain their shape and strength even at high temperatures of 120 ° C and 140 ° C for 7 days, but Comparative Examples 3 and 4 were able to maintain their shape at 140 ° C. However, the strength decreased significantly at high temperatures (Example 5 was evaluated at 140 ° C! /).

Further, Examples 5, 7, and 8 using phosphoric acid ester, melamine cyanurate, and aluminum hydroxide as flame retardants were able to achieve flame retardancy of V-1 or higher.

In particular, Example 5 using a phosphate ester and melamine cyanurate in combination as a flame retardant and Example 8 using a phosphate ester, melamine cyanurate and hydroxyaluminum hydroxide achieved V-0 flame retardancy. did it. In Example 7 and Example 8, the total amount of the flame retardant is close, but the flame retardancy of Example 8 is superior to that of Example 7 because three types of flame retardant are mixed. The effect was considered. Example 8 also has a high flexural modulus and is particularly useful as a housing material.

[0062] As described above, a molded product containing the biodegradable polyester of the present invention as a main component, cross-linked by irradiation with ionizing radiation, and having a gel fraction of 50% or more has heat resistance, bending strength, and tensile strength. In addition, since it is provided, it can be suitably used as a cap for an external connection terminal of an electronic device or a housing, and has the advantage of reducing the amount of waste during disposal because it is biodegradable.

Industrial applicability

[0063] Since the molded article made of the biodegradable resin of the present invention has heat resistance and strength, it is not limited to a cap or casing for an external connection terminal of a mobile phone, but a notebook computer, electronic notebook, electronic camera, It is suitably used as a cap case for external connection terminals of various portable electronic devices such as portable audio devices. Furthermore, from the viewpoint of reducing the amount of garbage at the time of disposal, it can be used not only for portable devices but also for cases and covers of electronic devices.

Claims

The scope of the claims

[1] A cross-linked structure in which at least a polyfunctional monomer is mixed with the biodegradable polyester, and the gel fraction (gel content dry weight Z initial dry weight) of the biodegradable polyester is 50% or more and 90% or less. The exterior member for electronic devices characterized by the above-mentioned.

[2] The polyfunctional monomer also has an acrylic or methacrylic monomer power, and the multifunctional monomer is blended in an amount of 2 to 15 parts by mass with respect to 100 parts by mass of the biodegradable polyester! The exterior member for an electronic device according to claim 1.

[3] The exterior member for an electronic device according to claim 1 or 2, further comprising 1 to 150 parts by mass of an inorganic filler or Z and a dye per 100 parts by mass of the biodegradable polyester.

4. The exterior member for an electronic device according to claim 3, wherein the inorganic filler is wollastonite.

[5] The exterior member for an electronic device according to any one of claims 1 to 4, further comprising one or more of the following flame retardants (a) to (e).

[6] The electronic device according to any one of claims 1 to 5, wherein the biodegradable polyester is a natural or petroleum-derived polymer having a glass transition temperature of room temperature or lower. Exterior member.

[7] The biodegradable polyester is naturally derived having a glass transition temperature of room temperature or lower.

The exterior member for an electronic device according to claim 6, wherein V ヽ is a petroleum-derived polymer as a main component.

[8] The exterior member for an electronic device according to any one of claims 1 to 7, wherein the flexural modulus power is 00 to 2400 MPa, and the Young's modulus is 500 to 2000 MPa.

[9] An electronic device comprising the external connection terminal cap or Z and the casing made of the exterior member according to any one of [1] to [8].

[10] At least a polyfunctional monomer is blended in the biodegradable polyester and kneaded, the kneaded product is molded into a required shape, and the resulting molded product is irradiated with ionizing radiation at an irradiation dose of 50 kGy or more and 200 kGy or less. The gel fraction of the biodegradable polyester is 50% or more and 90% or less. The manufacturing method of the exterior member for electronic devices characterized by making it bridge | crosslink.