JP4878925B2 - Resin hinge - Google Patents

Description

  The present invention relates to a hinge part, and more particularly to a resin hinge part used for a portable device having a hinge function.

  A portable device having a hinge function such as a foldable mobile phone, an electronic notebook, an electronic dictionary, a personal computer, and a video camera employs a method of folding a liquid crystal screen and a keyboard portion for the purpose of miniaturization. This folding system always requires a hinge part, and at present, many metal hinge parts are used. In the case of a metal hinge, it is necessary to apply grease because the slidability between metals is poor. When the opening / closing operation is repeated for a long period of time, the slidability due to running out of grease decreases and there is a problem in long-term durability. In addition, the degree of freedom in design is lost and it is difficult to achieve high performance and light weight.

  In recent years, switching from metal hinges to resin hinges is being made for the purpose of reducing the weight, size and performance of hinge parts. However, a general resin combination has a high friction coefficient due to poor slidability between resins, and at the same time as the friction coefficient increases, the amount of wear of the hinge parts also increases, resulting in a problem in long-term durability. Grease application has also been investigated for the purpose of improving the slidability degradation, but the problem of running out of grease as well as the metal hinge is not improved.

  Patent Documents 1 to 3 have proposed a hinge of a folding cellular phone. These patent documents describe the structure of the hinge part, and do not describe the material used for the hinge part.

Japanese Patent Laid-Open No. 10-311327 JP 2000-022790 A JP 2001-355371 A

  An object of this invention is to provide the resin hinge excellent in long-term durability which can be used for the portable apparatus which has a hinge function.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have improved hinge durability by combining specific thermoplastic resins, and have reached the present invention.

That is, the resin hinge of the present invention has a movable side cam part made of a thermoplastic resin (A) having a friction coefficient of 0.05 to 0.3, and a fixed side cam part made of a thermoplastic resin (B). The ratio (A) / (B) of the flexural modulus (ASTM, D790) between the thermoplastic resin (A) and the thermoplastic resin (B) is 0.1 to 0.6 .

  The resin hinge of the present invention smoothes the opening and closing of liquid crystal screens of folding mobile phones, electronic notebooks, electronic dictionaries, personal computers, video cameras, etc. it can.

  Hereinafter, the present invention will be described in detail.

  The resin hinge component of the present invention is a cam component of a portable device having a hinge function such as a folding cellular phone, an electronic notebook, an electronic dictionary, a personal computer, and a video camera. The shape is not particularly limited, but has the same troughs with 180 degree intervals as the crests with 180 degree intervals, and the crests and troughs are formed with a phase difference angle smaller than 90 degrees. It is a cam part provided with two slopes adjacent to the slope between the part and the valley part. One of the cam parts is movable and the other is fixed when the liquid crystal screen is opened and closed.

  The thermoplastic resin (A) used for the movable cam part has a friction coefficient of 0.05 to 0.3, preferably 0.05 to 0.25, and more preferably 0.05 to 0.20. If the coefficient of friction is less than 0.05, the slidability between the cam parts is too good, so that the cam parts rotate too smoothly, and the rotational torque decreases. On the other hand, when the friction coefficient exceeds 0.3, the friction coefficient between the cam parts is high, so that the amount of wear of the cam parts increases and there is a problem in long-term durability.

  The ratio (A) / (B) of the flexural modulus (ASTM, D790) between the thermoplastic resin (A) and the thermoplastic resin (B) used for the fixed cam component is 0.1 to 1, preferably Is 0.1 to 0.6, more preferably 0.1 to 0.4. If the ratio (A) / (B) of the flexural modulus is less than 0.1, the operating noise generated when the cam part is operated increases. On the other hand, if the ratio (A) / (B) of the flexural modulus exceeds 1, the amount of wear of the movable cam parts increases and there is a problem in long-term durability.

  In order to set the ratio (A) / (B) of the flexural modulus to the above range, the flexural modulus (ASTM, D790) of the thermoplastic resin (A) is preferably 2000 to 4000 MPa, more preferably 2500 to 3500 MPa, More preferably, it is 2500-3000 MPa. The flexural modulus (ASTM, D790) of the thermoplastic resin (B) is preferably 4000 to 20000 MPa, more preferably 5000 to 20000 MPa, and still more preferably 10,000 to 20000 MPa.

  Thermoplastic resins (A) and (B) include olefin-based resins such as polyethylene and polypropylene, general-purpose plastics such as polystyrene, ABS resin, and PMMA, and general-purpose engineering such as polyacetal resin, polyamide resin, polybutylene terephthalate resin, and polycarbonate resin. It can be suitably selected from super engineering plastics such as resin, polyphenylene sulfide, polyimide, polyamideimide, polyarylate, polyetheretherketone, and among them, polyacetal resin or polyacetal resin composition containing polyacetal resin is preferable.

  The polyacetal resin of the present invention is an oxymethylene homopolymer substantially composed of oxymethylene units produced from a formaldehyde monomer or a cyclic oligomer such as a trimer (trioxane) or tetramer (tetraoxane). Polyoxymethylene homopolymer obtained by end-stabilization, ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4 to which 10 to 500 ppm of the above raw material and a hindered phenol antioxidant were added -Terminal stabilization of an oxymethylene-oxyalkylene copolymer containing 0.1 to 20% by mass of an oxyalkylene unit having 2 to 8 carbon atoms produced from a cyclic formal such as butanediol, glycol formal or diglycol formal processing Go-obtained polyoxymethylene - include polyoxyalkylene copolymers. Further, 50 wt% or more of an oxymethylene-oxyalkylene copolymer and polyoxymethylene (POM) block comprising a branched molecular chain and 50 wt% of a polymer block different from POM containing 50 wt% or more of oxymethylene repeating units. Also included are oxyalkylene block copolymers such as block polymers consisting of less than%.

  Preferable examples of the thermoplastic resin (A) include polyacetal resin compositions (I) to (III) (I) described below.

<Polyacetal resin composition (I)>
The polyacetal resin composition (I) is a composition comprising a polyolefin resin grafted with a polyacetal resin and a silicone compound.

  The polyolefin resin is a polyolefin resin composed of at least one olefin unit represented by the following general formula (3).

(R ₃ and R ₄ are selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, and an ether group, and may be the same or different. K = 10 to 500)

  The polyolefin-based resin also includes polyethylene modified with an aromatic vinyl monomer alone or with an active hydrogen-containing vinyl monomer.

  The aromatic vinyl monomer is a vinyl monomer containing a benzene ring, and includes alkyl group-substituted styrene such as styrene, methylstyrene, and ethylstyrene.

  Active hydrogen-containing vinyl monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, p-hydroxyphenyl methacrylate, p-hydroxybenzyl methacrylate, glycerin monomethacrylate , Hydroxyl group-containing esters of α, β-unsaturated carboxylic acids such as polyethylene glycol methacrylate and polypropylene glycol methacrylate, acrylic acid, methacrylic acid, acrylamide, allylamine, and allyl alcohol.

  Polyethylene is polyethylene comprising 90% by weight or more of ethylene units and 10% by weight or less of vinyl monomer units such as butene-1 and propylene. Preferred examples include polyethylene wax, low density polyethylene, linear low density polyethylene, high density polyethylene, and ultrahigh molecular weight polyethylene. Among them, low density polyethylene that is a homopolymer of ethylene having a number average molecular weight of 2 to 50,000 is preferable. .

  Examples of the silicone compound include silicone compounds represented by polydimethylsiloxane represented by the following general formula (4).

  The methyl group in the general formula (4) is hydrogen, alkyl group, phenyl group, ether group, ester group or reactive substituent such as hydroxy group, amino group, epoxy group, carboxyl group, carbinol group, methacryl group, May be substituted with a substituent having a mercapto group, a phenol group, a vinyl group, an aryl group, a polyether group, a fluorine-containing alkyl group, etc., and for grafting, preferably a substituent having a vinyl group or an aryl group, preferably It is necessary to have a vinyl group.

  Moreover, in General formula (4), n shows an average degree of polymerization and is the range of n = 1000-10000. If n is less than 1000 or exceeds 10,000, sliding performance may be insufficient. Moreover, what reduced content of a cyclic | annular low molecular monomer and an oligomer as much as possible is preferable.

  The content of the polyolefin-based resin grafted with the silicone compound may be appropriately determined so that the flexural modulus is in the above range, but is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the polyacetal resin. is there.

<Polyacetal resin composition (II)>
The polyacetal resin composition (II) is a composition containing an ester compound and calcium silicate.

  Examples of the ester compound include ester compounds of alcohols and fatty acids and ester compounds of alcohols and dicarboxylic acids.

  Examples of the alcohols include monohydric alcohols having one hydroxyl group and polyhydric alcohols including glycols having 2 to 6 hydroxyl groups. Specifically, the alcohol having one hydroxyl group is methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, capryl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol. , Lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, seryl alcohol, melyl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol , Cyclopentanol, cyclohexanol, benzyl alcohol, cinnamel alcohol, furfuryl Alcohol, and the like. Examples of the polyhydric alcohol having 2 to 6 hydroxyl groups include ethylene glycol, propylene glycol, butylene glycol, glycerin, hexanetriol, pentaerythritol, arabitol, ribitol, xylitol, sorbite, sorbitol, mannitol and the like.

  The fatty acid is at least one of a saturated fatty acid and an unsaturated fatty acid. Specifically, capric acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, liglyceric acid, serotic acid, montanic acid, melicic acid , Celloplus acid, undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearic acid and the like.

  Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, etc. Can do.

  The content of the ester compound may be appropriately determined so that the flexural modulus is in the above range, but is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the polyacetal resin.

Calcium silicate is composed of silicon dioxide (SiO ₂ ) and calcium oxide (CaO), and the blending ratio of each is 30 to 70% by weight of silicon dioxide and 20 to 60% by weight of calcium oxide. 5 white fine powder.

  The content of calcium silicate may be appropriately determined so that the flexural modulus is in the above range, but is preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyacetal resin.

<Polyacetal resin composition (III)>
In the polyacetal resin composition (III), one end of a linear polymer composed of repeating oxymethylene units is converted to an alkylene oxide adduct and carboxylic acid to an alcohol represented by the following general formula (1) or (2). A composition comprising an oxyalkylene block copolymer having a number average molecular weight of 10,000 to 500,000, which is blocked with a compound selected from the group consisting of an alkylene oxide adduct and having a number average molecular weight excluding terminal groups, and an α-olefin copolymer.

(R ₁ and R ₁ ′ are selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and may be the same or different. R ₁ bonded to different carbon atoms. , R ₁ 'may be the same or different, and R ₂ is selected from an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, m = 2 to 6, n = 1 to 1000. )

  Examples of the α-olefin copolymer include a hydrocarbon-based synthetic oil which is a copolymer of ethylene and an α-olefin and has a number average molecular weight (Mn) of 500 to 4000 and no polar group in the molecular chain.

  The α-olefin copolymer content may be appropriately determined so that the flexural modulus falls within the above range, but is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the oxyalkylene block copolymer. is there.

  As a preferable example of the thermoplastic resin (B), a polyacetal resin composition comprising a polyacetal resin and an inorganic filler such as carbon fiber, glass fiber, glass bead, potassium titanate whiskerite, welastonite, or calcium carbonate. Among them, a polyacetal resin composition comprising a polyacetal resin and carbon fiber or calcium carbonate is preferable. The content of the inorganic filler may be appropriately determined so that the flexural modulus is in the above range, but is preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyacetal resin.

  The molding method for the resin hinge part of the present invention is not particularly specified, and can be obtained by generally used injection molding.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  In addition, the component used in the present Example is as follows.

(A) Polyacetal resin (A-1)
A polyoxymethylene copolymer containing 0.5 mol% of 1,3-dioxolane as a copolymer component and having a flexural modulus of 2900 MPa and a melt flow rate value of 10 g / 10 min (ASTM, D1238, condition E).

(A-2)
A polyoxymethylene copolymer containing 1,3-dioxolane as a copolymer component and having a flexural modulus of 2300 MPa and a melt flow rate value of 10 g / 10 min (ASTM, D1238, condition E).

(A-3)
A polyoxymethylene copolymer containing 1,3-dioxolane as a copolymer component and having a flexural modulus of 1900 MPa and a melt flow rate value of 10 g / 10 min (ASTM, D1238, Condition E).

(A-4)
Polyacetal block copolymer having a melt flow rate of 15 g / 10 min consisting of a stearyl alcohol group and an acetyl group added with propylene oxide (40 mol) as a terminal group of a polyacetal homopolymer (flexural modulus: 2600 MPa, number average molecular weight excluding terminal groups) : 50000).

(A-5)
Polyacetal resin (bending elastic modulus: 7000 MPa) obtained by melt-kneading the polyoxymethylene copolymer (A-2) and carbon fiber.

(A-6)
A polyacetal resin (bending elastic modulus: 14000 MPa) obtained by melt-kneading a polyoxymethylene copolymer (A-2) and carbon fiber.

(A-7)
A polyacetal resin (bending elastic modulus: 4500 MPa) obtained by melt-kneading a polyoxymethylene copolymer (A-2) and calcium carbonate (average particle size: 5 μm).

(B) Polyolefin resin grafted with a silicone compound (B-1)
Using Labo Plastmill (manufactured by Toyo Seiki Co., Ltd.), a melt index MI value (ASTM, D1238, condition E) containing 5% by weight of vinyl acetate 5 g / 10 min of low density polyethylene 36 g and the following formula (5) 24 g of the silicone compound represented by the formula (2) and 0.05 g of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane were added to the polyethylene by melting and kneading for 30 minutes at a temperature of 180 ° C. and a rotation speed of 60 rpm. A resin grafted with a silicone compound was obtained.

(Silicone compound in which 4 moles are substituted with dimethylvinyl groups for 100 moles of silicone in the formula)

(B-2)
Using Labo Plastmill (manufactured by Toyo Seiki Co., Ltd.), 30 g of ethylene-methyl methacrylate copolymer having 5 g / 10 min of melt index MI (ASTM-D1238, condition E) containing 5 wt% of methyl-methacrylate and 30 g of the silicone compound represented by the formula (6) and 0.4 g of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane are added, and melt-kneaded for 20 minutes at a temperature of 180 ° C. and a rotation speed of 60 rpm. As a result, a resin in which a silicone compound was grafted onto the polyolefin was obtained.

(Silicone compound in which 5 mol of methyl group in formula is substituted with dimethylvinyl group with respect to 100 mol of silicone)

(C) Other compounds (C-1)
Liquid ethylene and α-olefin copolymer (number average molecular weight (Mn) = 2500)
(C-2)
Cetyl myristate (C-3)
Calcium silicate (average particle size: 5μm)

  Moreover, the evaluation method in a present Example is as follows.

[Friction coefficient measurement]
The friction coefficient between the same materials was measured using a Suzuki type thrust friction tester. The measurement conditions were as follows.

Surface pressure: 1.5 kgf / cm ²
Sliding speed: 60cm / sec
Test environment temperature: 23 ° C

<Hinge durability test>
As shown in FIG. 2, a torque of 4 kg · cm is applied to the cam mechanism component and rotated at a speed of 30 times / second. After the start of the test, the weight change (%) of the cam mechanism parts (two on the left and right) and the number of times when the operation sound was generated when 5,000 times, 10,000 times, 20,000 times and 50,000 times were reached were observed.

<Example 1>
After 100 parts by weight of the polyacetal resin (A-1) is uniformly blended with a blender by 1 part by weight of a polyolefin resin (B-1) grafted with a silicone compound, L / D = 200 ° C. No. 42 25 mmφ twin screw extruder was used for melt kneading at a screw rotation speed of 200 rpm and 10 kg / hr. The extruded resin was pelletized with a strand cutter to form the movable cam part 1 shown in FIG. On the other hand, the fixed cam part 2 was molded using polyacetal resin (A-6). The results are shown in Table 1.

<Examples 2-7, Comparative Examples 1-3>
A cam part was molded in the same manner as in Example 1 except that the composition of the thermoplastic resin was changed as shown in Table 1. The results are shown in Table 1.

<Comparative example 4>
Olefin grease was applied to the cam part molded in Comparative Example 2 and a hinge durability test was performed. The results are shown in Table 1.

  The resin hinge of the present invention can be suitably used as a hinge component of a portable device having a hinge mechanism such as a folding cellular phone, an electronic notebook, an electronic dictionary, a personal computer, and a video camera.

It is a figure which shows the resin hinge components manufactured in the Example. It is a figure which shows the durability test method of the resin hinge components of FIG.

Explanation of symbols

1 Movable cam part 2 Fixed cam part 3 Metal shaft

Claims (1)

A movable cam part made of a thermoplastic resin (A) having a friction coefficient of 0.05 to 0.3 and a flexural modulus (ASTM, D790) of 2000 to 4000 MPa, and a flexural modulus (ASTM, D790) It has a fixed cam part made of a thermoplastic resin (B) of 4000 to 20000 MPa, and the ratio (A) of the flexural modulus (ASTM, D790) of the thermoplastic resin (A) and the thermoplastic resin (B) / (B) is a resin hinge of 0.1 to 0.6 ,
The thermoplastic resin (A) is a polyacetal resin composition (I) comprising a polyolefin resin grafted with a polyacetal resin and a silicone compound, or a polyacetal resin composition (II) containing an ester compound and calcium silicate, or One end of a linear polymer composed of repeating oxymethylene units is selected from the group consisting of an alkylene oxide adduct to alcohol and an alkylene oxide adduct to carboxylic acid represented by the following general formula (1) or (2). A polyacetal resin composition (III) comprising an oxyalkylene block copolymer and an α-olefin copolymer blocked with a selected compound and having a number average molecular weight of 10,000 to 500,000 excluding terminal groups,
The resin hinge, wherein the thermoplastic resin (B) is a polyacetal resin composition comprising a polyacetal resin and carbon fiber or calcium carbonate .

(R ₁ and R ₁ ′ are selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and may be the same or different. R ₁ bonded to different carbon atoms. , R ₁ 'may be the same or different, and R ₂ is selected from an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, m = 2 to 6, n = 1 to 1000. )

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