JP2007084640A - Colored polyacetal resin hinged cap element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hinged cap elements excellent in hinge properties and coatability and of portable audio instruments, cellular telephones, personal computers and PDA instruments. <P>SOLUTION: The resinous hinged cap element has 300-1,000 MPa flexural modulus, comprises (A) polyacetal resin and (B) thermoplastic elastomer polyacetal resin composition having ≤60°C glass transition temperature, has both of hinge properties and molded product surface coatability and comprises a cap part 1 and a hinge part 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin hinged cap component having excellent flexibility. More specifically, the present invention provides cap parts with hinges for portable audio devices, mobile phones, personal computers, PDA devices and the like having excellent hinge characteristics and paintability.

  In recent years, thermoplastic elastomer cap parts are often used for connection terminals of portable audio devices, mobile phones, personal computers, PDAs and the like. These resin caps and hinge parts are required to have hinge characteristics, and a thermoplastic elastomer has been conventionally used. Thermoplastic elastomer can be made flexible by arbitrarily changing the soft segment and hard segment, and is suitable as a member for connection terminals of portable audio equipment, mobile phones, personal computers, PDAs, etc. .

  On the other hand, if the chemicals such as hair styling agents or sweat adhere to and contact for a long period of time, the resin cap and hinge parts swell and cause a problem of appearance failure. Incompatibility with the outside may not occur due to incompatibility with the housing portion and entry of dust into the connection terminal portion. In recent years, the design of portable audio devices, mobile phones, personal computers, and PDAs is also an important characteristic, and there is an increasing demand for the same color of the casing, cap, and hinge parts. Therefore, there is a demand for a resin cap and a hinge part that are excellent in hinge characteristics and paintability (paintability for providing the same color with the casing).

As a clip and hinge part made of polyacetal resin, the invention described in Patent Document 1 has been proposed. This is a cap and hinge part made of polyacetal resin in which a core shear polymer and a polyester elastomer are blended with polyacetal resin, and does not simultaneously impart hinge characteristics and paintability, which are the objects of the present invention.
Japanese Patent No. 3357548

  In order to solve the above problems, the present invention has been studied by paying attention to the flexural modulus of polyacetal resin. As a result, a resin composition excellent in hinge property paintability has been found, and the present invention has been achieved. That is, an object of the present invention is to provide a resin hinged cap part having excellent hinge characteristics and paintability.

  Under these circumstances, the present inventors have intensively studied to achieve the above object, and as a result, the present invention has been completed. That is, the present invention is as described below.

1. A cap part with a resin hinge in which the surface of a molded article made of a polyacetal resin composition having a flexural modulus of 300 to 1000 MPa is coated.
2. 2. The resin hinged cap part according to 1 above, wherein the polyacetal resin composition comprises (A) a polyacetal resin and (B) a thermoplastic elastomer polyacetal resin composition having a glass transition temperature of 60 ° C. or less. .
3. The polyacetal resin (A) is a polyoxymethylene block copolymer (A-1) having a number average molecular weight of 10,000 to 500,000 represented by the following formula (1), an oxymethylene group as a main repeating unit, and a carbon number of 2 The above oxyalkylene group is used in combination with the polyoxymethylene copolymer (A-2) containing 0.1 to 10 mol% with respect to the oxymethylene unit, and the weight ratio thereof is (A-1) / (A-2) = 100/0 to 10/90, The cap part with a resin hinge as described in 1 or 2 above.

[In the formula, other than A (hereinafter referred to as B block) is m = 2 to 98 mol%, n = 2 to 98 mol%, m + n = 100 mol%, and m is present randomly or in blocks with respect to n. Hydrogenated liquid polybutadiene residues having a number average molecular weight of 500 to 10,000 and hydroxyalkylated at both ends. However, B block may be those having the following unsaturated bond iodine value _20g-I 2 / 100g. k is an integer selected from 2 to 6, and two k's may be the same or different. R is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. A is a polyoxymethylene copolymer residue represented by the following formula (2).

(R ₁ is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. J is an integer selected from 2 to 6. x = 95 to 99.9 mol%, y = 5 to 0.1 mol%, x + y = 100 mol%, y is present randomly with respect to x, in formula (1), the average number average molecular weight of the two A blocks is 5, 000-250,000)]

  ADVANTAGE OF THE INVENTION According to this invention, the cap part with a resin hinge which has both hinge characteristics and paintability can be provided by combining the thermoplastic elastomer whose glass transition temperature is 60 degrees C or less with polyacetal resin.

  Hereinafter, the present invention will be described in detail. The polyacetal resin used in the present invention is a homopolymer obtained by polymerizing cyclic oligomers such as formaldehyde or its trimer trioxane or tetramer tetraoxane, and capping both ends of the polymer with ether and ester groups. First, it was obtained by copolymerizing formoxane or its trimer trioxane or tetramer tetraoxane with ethylene oxide, propylene oxide, 1,3-dioxolane, glycol formal, diglycol formal, etc. An oxymethylene copolymer containing 0.1 to 40 mol% of an oxyalkylene unit having 2 to 8 carbon atoms with respect to oxymethylene, one having a branched molecular chain, 50% by weight or more of a segment comprising an oxymethylene unit And 50% by weight of different segments It is at least one selected from oxymethylene block polymers containing a lower.

  Among these, a preferred polyacetal resin is a polyoxymethylene block copolymer (A-1) having a number average molecular weight of 10,000 to 500,000 represented by the following formula (1), an oxymethylene group as a main repeating unit, and a carbon number Two or more oxyalkylene groups are used in combination with a polyoxymethylene copolymer (A-2) containing 0.1 to 10 mol% with respect to the oxymethylene unit, and the weight ratio thereof is (A-1). / (A-2) = 100/0 to 10/90.

[In the formula, other than A (hereinafter referred to as B block) is m = 2 to 98 mol%, n = 2 to 98 mol%, m + n = 100 mol%, and m is present randomly or in blocks with respect to n. Hydrogenated liquid polybutadiene residues having a number average molecular weight of 500 to 10,000 and hydroxyalkylated at both ends. However, B block may be those having the following unsaturated bond iodine value _20g-I 2 / 100g. k is an integer selected from 2 to 6, and two k's may be the same or different. R is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. A is a polyoxymethylene copolymer residue represented by the following formula (2).

(R ₁ is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. J is an integer selected from 2 to 6. x = 95 to 99.9 mol%, y = 5 to 0.1 mol%, x + y = 100 mol%, y is present randomly with respect to x, in formula (1), the average number average molecular weight of the two A blocks is 5, 000-250,000)]

This polyoxymethylene block copolymer (A-1) can be produced by the method described in WO 01/009213.
The polyoxymethylene block copolymer (A-1) is effective in improving the compatibility with the thermoplastic elastomer component, and in this respect, the single use of (A-1) is most effective. When used together with the methylene copolymer (A-2), the weight ratio of (A-1) / (A-2) can be arbitrarily used within the range of 100/0 to 10/90. The range of / 0 to 20/80 is preferable, and the range of 100/0 to 30/70 is particularly preferable.

  In addition, the melt flow rate (measured under the conditions of ASTM-D1238-57T) of the polyoxymethylene resin used in the present invention is 0.5 g / 10 min or more from the surface of molding and 100 g / from the surface of durability. The range is 10 minutes, preferably 1.0 to 80 g / 10 minutes, more preferably 5 to 60 g / 10 minutes, and most preferably 7 to 50 g / 10 minutes. The polyacetal resin of the present invention may be prepared by using conventionally known additives, for example, hindered phenol antioxidants, heat stabilizers such as fatty acid metal salts and nitrogen-containing compounds, and nucleating agents represented by boron nitride and calcium carbonate. , Antistatic agents typified by glyceryl stearate, lubricants typified by ethylene bisstearic acid amide, ultraviolet absorbers, weathering (light) stabilizers, pigments, and other various additives conventionally added to polyacetal resins Can be melt-kneaded.

  The thermoplastic elastomer used for the component (B) of the present invention is not particularly limited as long as it is a thermoplastic elastomer having a glass transition temperature of 60 ° C. or lower. Examples of thermoplastic elastomers having a glass transition temperature of 60 ° C. or lower include vinyl aromatic compounds, polyolefin elastomers, polyurethane elastomers, polyester elastomers, and polyamide elastomers. Among these, from the viewpoint of compatibility with the polyacetal resin (A), a hydrogenated vinyl aromatic compound-conjugated diene compound random copolymer, a maleic anhydride-modified ethylene-butene copolymer, and an olefin resin are preferable.

  As a specific example of the thermoplastic elastomer, the vinyl aromatic compound is a polymer having at least one hydrogenated vinyl aromatic compound-conjugated diene compound random copolymer block, A polymer having at least one block randomly copolymerized with a conjugated diene compound is hydrogenated. Also included are olefin elastomers, polyester elastomers, and polyamide elastomers.

Specific examples of the random copolymer of the vinyl aromatic compound and the conjugated diene compound include the following.
(1) At least one polymer block A mainly composed of a vinyl aromatic compound (the content of the vinyl aromatic compound is at least 90% by weight or more) and at least one vinyl aromatic compound-conjugated diene compound Block copolymer comprising random copolymer block B (vinyl aromatic compound content is 3% by weight or more and less than 90% by weight) (2) At least one polymer mainly comprising a conjugated diene compound Block C (the content of the conjugated diene compound is at least 97% by weight or more) and at least one vinyl aromatic compound-conjugated diene compound random copolymer block B (the content of the vinyl aromatic compound is 3% by weight) (3) at least one polymer block mainly composed of a vinyl aromatic compound. A (vinyl aromatic compound content is at least 90% by weight) and at least one vinyl aromatic compound-conjugated diene compound random copolymer block B (vinyl aromatic compound content is 3% by weight) And a block copolymer (4) containing at least one polymer block C mainly composed of a conjugated diene compound (content of the conjugated diene compound is at least 97% by weight or more). ) Vinyl aromatic compound-conjugated diene compound random copolymer

  As the vinyl aromatic compound used in the polymer having at least one vinyl aromatic compound-conjugated diene compound random copolymer block listed above, styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1 -Diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene and the like may be used, and two or more of these may be used, and styrene is particularly preferable. Conjugated dienes are diolefins having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene and the like, and particularly common ones include 1,3-butadiene and isoprene. Two or more of these may be used.

  Examples of olefin resins include homopolymers / copolymers of compounds such as ethylene, propylene, butene, pentene, methylpentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, butadiene, isoprene, norbornene, and hydrogen thereof. It is an additive and a copolymer with other copolymerizable compounds. Specifically, polyethylene (high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene), polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene Copolymer, propylene-butene copolymer, polybutene, polybutadiene, hydrogenated product of isoprene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl Examples thereof include alcohol copolymers.

  Furthermore, these are made of α, β-unsaturated carboxylic acid (acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid) and / or acid anhydrides thereof (peroxide if necessary). It is an acid-modified olefin resin modified in combination). Moreover, what copolymerized these olefinic compounds and acid anhydrides may be used. Two or more kinds of these unmodified olefin resins and acid-modified olefin resins can be used in combination. Among these, the use of an acid-modified olefin resin is preferable from the viewpoint of compatibility. When the acid-modified olefin resin is used, the acid modification rate is preferably in the range of 3 to 0.01% by weight, more preferably in the range of 2 to 0.05% by weight, and particularly preferably in the range of 1 to 0.1% by weight. It is a range. If the acid modification rate exceeds 3% by weight, the thermal stability is impaired, which is not preferable, and if it exceeds 0.01, an improvement effect is exhibited. The acid modification rate of this acid-modified olefin resin can be determined by dissolving a resin sample with hot xylene and titrating with sodium methylate using phenolphthalein as an indicator.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, these Examples do not limit the scope of the present invention at all.
First, resins used in Examples and Comparative Examples will be described.

[Contents of ingredients used]
(A) Polyacetal resin (A-1) Polyoxymethylene block copolymer: Trioxane having a water + formic acid = 4 ppm, adjusted to 80 ° C. with a jacketed biaxial paddle type continuous polymerizer capable of passing a heat medium. At 30 mol / hr, and simultaneously with 1,3-dioxolane as a cyclic formal at 2 mol / hr to the polymerization machine, and boron trifluoride di-n-butyl etherate dissolved in cyclohexane as a polymerization catalyst was trioxane 1 mole to be 5 × 10 ^-5 mol, and as a chain transfer agent, 1 × 10 ^-3 mole of trioxane 1 mole of both terminal hydroxyl groups hydrogenated polybutadiene (Mn = 2330) of the following formula (3) Then, the polymerization was carried out by continuously feeding. After the polymer discharged from the polymerization machine is put into a 1% aqueous solution of triethylamine to completely deactivate the polymerization catalyst, the polymer is filtered and washed, and 1 part by weight of the crude polyoxymethylene copolymer after filtration and washing On the other hand, as a quaternary ammonium compound, triethyl (2-hydroxyethyl) ammonium formate was added in an amount of 20 ppm by weight in terms of nitrogen, mixed uniformly, and dried at 120 ° C.
Next, triethylene glycol bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is added as an antioxidant to 100 parts by weight of the dried crude polyoxymethylene copolymer. .3 parts by weight and 0.02 part by weight of calcium stearate were added and fed to a twin screw extruder with a vent. If necessary, water and / or triethylamine is added to the molten polyoxymethylene copolymer in the extruder, and the unstable end portion is decomposed at a set temperature of the extruder of 200 ° C. and a residence time of 5 minutes in the extruder. Went. The polyoxymethylene copolymer decomposed at the unstable end was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die, and pelletized. The obtained polyoxymethylene copolymer had a flexural modulus of 2550 MPa and a melt flow rate of 9.3 g / 10 min (ASTM D-1238-57T).

(A-2) Polyoxymethylene copolymer A jacketed biaxial paddle type continuous polymerization machine capable of passing a heating medium was adjusted to 80 ° C., and water and formic acid = 4 ppm of trioxane at 40 mol / hr, at the same time 1,3-dioxolane as a cyclic formal were fed to the polymerizer at a 2 mol / hr, a boron trifluoride di -n- butyl etherate dissolved in cyclohexane as a polymerization catalyst of trioxane 1 mol 5 × 10 ^- so that ⁵ moles, also was methylal _{[(CH 3 O) 2 CH} 2] was continuously fed so as to 2 × 10 ^-3 moles trioxane 1 mole polymerization as chain transfer agents. After the polymer discharged from the polymerization machine is put into a 1% aqueous solution of triethylamine to completely deactivate the polymerization catalyst, the polymer is filtered and washed, and 1 part by weight of the crude polyoxymethylene copolymer after filtration and washing On the other hand, as a quaternary ammonium compound, triethyl (2-hydroxyethyl) ammonium formate was added in an amount of 20 ppm by weight in terms of nitrogen, mixed uniformly, and dried at 120 ° C.
Next, triethylene glycol bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is used as an antioxidant with respect to 100 parts by weight of the dried crude polyoxymethylene copolymer. 0.3 parts by weight and 0.02 part by weight of calcium stearate were added and fed to a twin screw extruder with a vent. If necessary, water and / or triethylamine is added to the molten polyoxymethylene copolymer in the extruder, and the unstable end portion is decomposed at a set temperature of the extruder of 200 ° C. and a residence time of 5 minutes in the extruder. Went. The polyoxymethylene copolymer decomposed at the unstable end was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die, and pelletized. The resulting polyoxymethylene copolymer had a flexural modulus of 2600 MPa and a melt flow rate of 9.0 g / 10 min (ASTM D-1238-57T).

(B) Thermoplastic elastomer having a glass transition temperature of 60 ° C. or less (polymer having at least one aromatic vinyl compound-conjugated diene compound random copolymer block)
(B-1) Thermoplastic elastomer (1)
N-Butyllithium is used as a polymerization initiator in a cyclohexane solvent in a reactor equipped with a stirrer substituted with nitrogen gas, has an ABA structure, a number average molecular weight of 190,000, a molecular weight distribution of 1.9, all bonds A styrene-butadiene random copolymer having a styrene content of 70% by weight, a content of all block styrenes in the polymer of 5% by weight, and a 1,2-vinyl bond content of the butadiene portion of 14% by weight was polymerized. Thereafter, the polymerization liquid was transferred to another reactor substituted with nitrogen gas, and the hydrogenation catalyst was used to carry out the ethylenic unsaturated bond of the polybutadiene portion using a hydrogenation catalyst, and the hydrogenation rate was 98.9%. A polymer was obtained. To this polymer solution after the hydrogen reaction, 3 parts of 2,6-di-tert-butyl-p-cresol as a heat deterioration stabilizer is added with respect to 100 parts by weight of the polymer, and the cyclohexane as a solvent is removed by heating. Thus, a polymer [thermoplastic elastomer (1)] having at least one aromatic vinyl compound-conjugated diene compound random copolymer block having an ABA structure was obtained. The glass transition temperature (tan δ) of this polymer was 15 ° C.

(B-2) Thermoplastic elastomer (2)
N-Butyllithium is used as a polymerization initiator in a cyclohexane solvent in a reactor equipped with a stirrer substituted with nitrogen gas, has an ABA structure, a number average molecular weight of 180,000, a molecular weight distribution of 1.8, all bonds A styrene-butadiene random copolymer having a styrene content of 68% by weight, a content of all blocks A in the polymer of 13% by weight, and a 1,2-vinyl bond content of the butadiene portion of 14% was polymerized. Thereafter, the polymerization liquid was transferred to another reactor substituted with nitrogen gas, and the hydrogenation catalyst was used to carry out the ethylenic unsaturated bond of the polybutadiene portion under a hydrogen pressure, and the hydrogenation rate was 98.0%. A polymer was obtained. To this polymer solution after the hydrogen reaction, 3 parts of 2,6-di-tert-butyl-p-cresol as a heat deterioration stabilizer is added with respect to 100 parts by weight of the polymer, and the cyclohexane as a solvent is removed by heating. Thus, a polymer [thermoplastic elastomer (2)] having at least one aromatic vinyl compound-conjugated diene compound random copolymer block having an ABA structure was obtained. The glass transition temperature (tan δ) of this polymer was 5 ° C.

(C) Olefin-based resin (C-1) Maleic anhydride-modified ethylene-butene copolymer (trade name Tafmer MH7010, manufactured by Mitsui Chemicals, Inc., maleic acid modification rate: 0.5% by weight)

Various measurement methods for evaluating the characteristics of the samples obtained in the examples will be described.
[Measurement method and evaluation method]
(1) Measuring method of flexural modulus Measured according to ASTM D790.
(2) Method for evaluating hinge characteristics Cap parts shown in FIG. 1 (main body length: 20 m, width: 7 mm, wall thickness: 2 mm, hinge part dimensions: 2φ × 6 mm) are formed, and the hinge part of the cap part is fixed with a jig. did. Thereafter, a load of 50 g was applied to the anti-hinge part side to repeatedly bend it to an angle of 90 ° C., and whether or not the hinge part was broken when it was repeated 10,000 times was evaluated according to the following criteria.
<Hinge characteristic criteria>
○: Neither crack nor fracture was observed. Δ: A fine crack of 1 mm or less was observed.

(3) Paintability evaluation method The surface of the test piece is degreased with methanol, primed with Nippon Oil (Prime) 1000S, and then coated with a urethane paint (Kansai Paint Soflex 500) and dried. I let you. At that time, coating was performed while adjusting the coating film to 1 to 20 μm. The obtained test piece was made of 100 grids at 1 mm intervals on the surface of the molded product, cellotape (registered trademark) was applied, peeled off, and how far it was peeled was determined according to the following criteria.
<Criteria for paintability>
○: Less than 5 peeled out of 100 grids. Δ: 5 to 10 peeled out of 100 grids. ×: 10 or more peeled out of 100 grids.

[Example 1]
Polyacetal resin (A-1) 40% by weight, aromatic vinyl compound-conjugated diene compound random copolymer block 60% by weight (B-2) and triethylene glycol-bis- [3- ( 3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 0.3% by weight, polyamide 66 0.05% by weight, calcium stearate 0.10% by weight, blended uniformly with a blender, and then 200 ° C. Was melt-kneaded at a screw rotation speed of 200 rpm and 10 kg / hr using a 25 mmφ twin-screw extruder with L / D = 42 set to. The extruded resin was pelletized with a strand cutter. A test piece was prepared using this pellet, and hinge characteristics and paintability were evaluated. The results are shown in Table 1.

[Example 2]
The pellets of Example 2 were obtained in the same manner as in Example 1 except that the weight ratio 60% by weight of the component (B-2) in Example 1 was changed to 50% by weight. A test piece was prepared using this pellet, and hinge characteristics and paintability were evaluated. The results are shown in Table 1.
[Example 3]
A pellet of Example 3 was obtained in exactly the same manner as in Example 1 except that 30% by weight of the component (B-1) was used instead of the component (B-2) in Example 1. A test piece was prepared using this pellet, and hinge characteristics and paintability were evaluated. The results are shown in Table 1.

[Comparative Example 1]
20% by weight of component (A-2) was used in place of component (A-1) in Example 1, and 80% by weight of olefin resin (C-1) was used in place of component (B-2). The same procedure as in Example 1 was performed to obtain a pellet of Comparative Example 1. A test piece was prepared using this pellet, and hinge characteristics and paintability were evaluated. The results are shown in Table 1.
[Comparative Example 2]
Polyacetal resin (A-2) 100% by weight, triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 0.3% by weight, polyamide 66 0.05% by weight %, Calcium stearate 0.10% by weight, and blended uniformly with a blender, and then melt-kneaded at a screw rotation speed of 200 rpm and 10 kg / hr using a L / D = 42 25 mmφ twin screw extruder set at 200 ° C. Went. The extruded resin was pelletized with a strand cutter. A test piece was prepared using this pellet, and hinge characteristics and paintability were evaluated. The results are shown in Table 1.

  Since the polyacetal resin composition in the present invention is excellent in both hinge characteristics and paintability (paintability for providing the same color with the casing), portable audio equipment, mobile phones, personal computers, PDAs, etc. It can be suitably used as a cap part with a resin hinge.

It is a figure which shows the cross section of the cap component with a hinge which evaluated the hinge characteristic. It is a figure which shows the design surface of the cap components with a hinge which evaluated the hinge characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cap component main body 2 Hinge part 3 Cap component design surface 4 Hinge part

Claims (3)

  A cap part with a resin hinge in which the surface of a molded article made of a polyacetal resin composition having a flexural modulus of 300 to 1000 MPa is coated.   2. The resin hinged cap according to claim 1, wherein the polyacetal resin composition comprises (A) a polyacetal resin and (B) a thermoplastic elastomer polyacetal resin composition having a glass transition temperature of 60 ° C. or less. parts. The polyacetal resin (A) is a polyoxymethylene block copolymer (A-1) having a number average molecular weight of 10,000 to 500,000 represented by the following formula (1), an oxymethylene group as a main repeating unit, and a carbon number of 2 The above oxyalkylene group is used in combination with the polyoxymethylene copolymer (A-2) containing 0.1 to 10 mol% with respect to the oxymethylene unit, and the weight ratio thereof is (A-1) / (A-2) = 100/0 to 10/90, The resin hinged cap part according to claim 1 or 2.

[In the formula, other than A (hereinafter referred to as B block) is m = 2 to 98 mol%, n = 2 to 98 mol%, m + n = 100 mol%, and m is present randomly or in blocks with respect to n. A hydrogenated liquid polybutadiene residue having a number average molecular weight of 500 to 10,000 and having both ends hydroxyalkylated. However, B block may be those having the following unsaturated bond iodine value _20g-I 2 / 100g. k is an integer selected from 2 to 6, and two k's may be the same or different. R is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. A is a polyoxymethylene copolymer residue represented by the following formula (2).

(R ₁ is selected from hydrogen, an alkyl group, a substituted alkyl group, an aryl group, and a substituted aryl group, and each may be the same or different. J is an integer selected from 2 to 6. x = 95 to 99.9 mol%, y = 5 to 0.1 mol%, x + y = 100 mol%, y is present at random with respect to x, in formula (1), average number average molecular weight of two A blocks 5000 to 5000 250,000)]

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