JPH08325431A - Hinge part made of polyacetal resin - Google Patents

Abstract

PURPOSE: To obtain from a polyacetal resin with improved flowability a hinge part which has excellent hinge properties and retains the mechanical properties, frictional and wear properties, moldability, toughness, etc., inherent in polyacetals. CONSTITUTION: This hinge part is obtained by molding a polyacetal resin composition comprising (A) 100 pts.wt. polyacetal resin having a melt index of 0.1-15g/10min as measured in accordance with ASTMD 1238-89E at a cylinder temp. of 190 deg.C, (B) 1-50 pts.wt. core-shell polymer comprising cores made of a rubbery polymer and shells made of a vitreous polymer, and (C) 1-20 pts.wt. oxyalkylene polymer having a mol.wt. of 10,000-300,000 and containing two to eight adjacent carbon chains.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hinge component made of a specific resin composition and made of polyacetal resin having extremely excellent hinge properties. The hinge component referred to herein is, for example, one as shown in FIG. 1, and refers to a thin wall portion to which a bending or bending load is applied one or more times in a certain portion of the component. The hinge (indicated by 1 in the figure) Call. There are no particular restrictions on the shape of the hinge, and it may be a sheet, a strip,
It can be string-shaped or the like. The thickness and the length of the hinge are not specified, and those having a function substantially as a hinge are included in the elbow part according to the present invention. In addition, in the present specification, the hinge characteristic is defined as durability against one or more bending or bending loads of the hinge as described above.

[0002]

2. Description of the Related Art As is well known, a polyacetal resin is an engineering material having excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. Recently, it has been used as a resin in a very wide range of fields. However, with the expansion of fields in which polyacetal resins are used, the properties of the materials may be required to be more specific. As one of such properties, there is a demand for development of a material having excellent flexibility, that is, a material having excellent hinge characteristics. In recent years, in particular, due to the need to reduce costs by reducing the number of parts, it has been increasingly desired that several parts be integrated with a hinge so that assembly can be performed easily and inexpensively. There are many factors that deteriorate the hinge characteristics, such as those used below, or those in which the preferable hinge shape cannot be obtained due to the structure, and the requirement for the essentially excellent hinge characteristics has become more severe.
Further, in the fields of general electric equipment, building materials, etc., there are increasing opportunities to use various materials in combination depending on the purpose, but further improvement in impact resistance of polyacetal resin is required. As a method for satisfying the requirement of the hinge characteristic, there is known a method of improving the hinge characteristic or the impact resistance by adding a rubber-like substance such as thermoplastic polyurethane to a polyacetal resin. Even with this method, it is possible to show an improvement in hinge characteristics, etc., but by incorporating a rubber-like substance, a peeling phenomenon easily occurs on the surface of the molded product, and there is a problem that the appearance of the molded product is significantly impaired,
Further, there are various problems such as a decrease in the thermal stability, a decrease in the weld strength and elongation of the molded product, a decrease in the fluidity, and a decrease in the degree of freedom in the hinge design. It was being done. Further, in recent years, the functions required of hinges have increased and the shape has become complicated, and the thickness has been reduced for the purpose of cost reduction and weight reduction. Further, in order to improve the productivity at the time of injection molding, it is necessary to shorten the molding cycle and take a large number of molds to increase the number of molded products obtained by one injection molding. To meet such demands,
There is a need for improved high flowability of materials. An object of the present invention is to provide a hinge component made of a polyacetal resin, which has more excellent hinge characteristics than conventional ones without impairing other physical properties.

[0003]

The present inventors have excellent impact resistance and have excellent hinge characteristics without sacrificing the original characteristics of the polyacetal resin as much as possible.
As a result of repeated intensive studies to develop a polyacetal resin material, it was found that it is effective to add a core-shell polymer and an oxyalkylene polymer having a specific molecular weight to a polyacetal resin having a specific viscosity, and the present invention is completed. It came to. That is, the present invention relates to (A) 100 parts by weight of a polyacetal resin having a melt index of 0.1 to 15 g / 10 minutes measured according to the ASTM D1238-89 E method at a cylinder temperature of 190 ° C. 1 to 50 parts by weight of a core-shell polymer having a core and a shell of a glassy polymer, and (C) 1 to 20 parts by weight of an oxyalkylene polymer having 2 to 8 carbon chains and having a molecular weight in the range of 10,000 to 300,000. The present invention relates to a polyacetal resin hinge part formed by molding a polyacetal resin composition containing the above.

First, the (A) polyacetal resin used in the present invention is a polymer compound having an oxymethylene group (—CH ₂ O—) as a main constituent unit, and other than polyoxymethylene homopolymer and oxymethylene group. It may be a copolymer, terpolymer or block copolymer having a small amount of other constitutional units, and the molecule may have not only a linear structure but also a branched or crosslinked structure. In the present invention, the melt index measured according to the ASTM D1238-89 E method at a cylinder temperature of 190 ° C. is 0.1 to 15 g / 10 minutes,
Preferably, 0.5 to 10 g / 10 min of polyacetal resin is used. The melt index of polyacetal is 0.1
If it is less than g / 10 minutes, it is difficult to secure the fluidity required for a hinge part, and if it exceeds 15 g / 10 minutes, good hinge properties may not be obtained.

The core-shell polymer (B) used in the present invention is an organic compound having a rubber-like polymer core and a glass-like polymer shell, and can be prepared by a known method, or a commercially available product can be used. It can also be used. Typical examples are Acryloid KM330 and KM653 manufactured by Rohm and Haas, Paraloid KCA-102 and KCA-301 manufactured by Kureha Chemical Industry Co., Ltd., and Takeda Pharmaceutical Co., Ltd.
STAPHYLOID PO-0143 and 0148, Kane Ace FM of Kanegafuchi Chemical Industry Co., Ltd., and METABLEN C-102, E-901, W-800 and S-2001 of Mitsubishi Rayon Co., Ltd. Among such core-shell polymers, preferred are core-shell polymers having a rubbery polymer core and a glassy polymer shell containing methyl methacrylate as a main component, and particularly a core-shell polymer in which anions are not substantially detected. When a core-shell polymer in which anions are detected is used, decomposition of polyacetal may be promoted during melt-kneading or injection molding, and desired clip properties may not be obtained. In some cases, too much decomposition may make melting and kneading impossible. Here, the core-shell polymer in which an anion is not substantially detected means a core-shell polymer in which an anion is not detected by a usual qualitative test of anion. For example, as a measuring method, 5 g of the sample (core shell polymer) is weighed in a 50 ml Erlenmeyer flask, 20 ml of ion-exchanged water is added, the mixture is stirred with a magnetic stirrer for 3 hours, and then the filtrate obtained by filtering with No. 5 C filter paper is divided into two parts. 1% barium chloride solution in one side
Add 0.5 ml and compare and observe the occurrence of turbidity (sulfate ion qualitative test). Also, perform the same treatment and add 0.1 N silver nitrate aqueous solution instead of 1% barium chloride aqueous solution.
The presence of anions can be confirmed by a method for comparatively observing the occurrence of turbidity (a qualitative test for halogen ions). A core-shell polymer in which these anions are not present is preferably used.

The core-shell polymer preferably used in the present invention is one obtained by emulsion polymerization using a nonionic surfactant and a polymerization initiator in which the radicals generated are neutral. Such a core-shell polymer can be produced, for example, by using the emulsion polymerization technique described in JP-A-3-14856. The emulsion polymerization can be carried out, for example, using the following surfactants and polymerization initiators. Nonionic surfactants include ether type such as polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, ester type such as polyoxyethylene monostearate, polyoxyethylene sorbitan monolaurate and the like. Most of the widely used nonionic surfactants such as sorbitan ester type and block polymer type such as polyoxyethylene polyoxypropylene block copolymer can be used. The amount of addition is appropriately selected according to the particle stabilizing ability of the surfactant. As the polymerization initiator, azobisisobutyronitrile, 2,2 '
-Azo-based polymerization initiators such as dimethyl azobisisobutyrate and 2,2'-azobis (2-aminopropane) dihydrochloride, start of peroxide-based polymerization such as cumene hydroperoxide, diisopropylbenzene hydroperoxide and hydrogen peroxide The agents are used alone or in combination of two or more kinds. If emulsion polymerization is carried out in such a reaction system using a surfactant containing no anion and a polymerization initiator other than persulfate, the obtained core-shell polymer contains substantially no anion, or contains anion. Even if it is, a very small amount of core-shell polymer can be obtained. The polyacetal resin composition using such a core-shell polymer that does not substantially contain anions has excellent hinge properties.

The (B) core-shell polymer in the present invention has a rubber-like polymer core and a glass-like polymer shell. It is obtained by a continuous multi-stage emulsion polymerization method in which the coalescence is sequentially coated. When the core-shell polymer has an intermediate phase to be described later, the intermediate phase may be formed by a multi-step emulsion polymerization method in which the polymer of the later step penetrates into the polymer of the earlier step.
At the time of particle generation polymerization, it is preferable to start the emulsion polymerization reaction by adding a monomer, a surfactant and water to a reactor, and then adding a polymerization initiator. The first stage of polymerization is a reaction that forms a rubbery polymer. Examples of the monomer that constitutes the rubber-like polymer include conjugated dienes, alkyl acrylates having an alkyl group with 2 to 8 carbon atoms, and mixtures thereof. By polymerizing these monomers, the glass transition temperature of −30
It forms a rubbery polymer below ° C. Examples of such conjugated dienes include butadiene, isoprene, chloroprene, and the like, but butadiene is particularly preferably used. Examples of the alkyl acrylate having an alkyl group having 2 to 8 carbon atoms include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc., but butyl acrylate is particularly preferably used. In the first-stage polymerization, a copolymerizable monomer such as a conjugated diene and an alkyl acrylate, for example, styrene, vinyltoluene, aromatic vinyl such as α-methylstyrene, aromatic vinylidene, acrylonitrile, methacrylonitrile, and other cyanide vinyl are used. It is also possible to copolymerize vinylidene cyanide, alkyl methacrylate such as methyl methacrylate and butyl methacrylate. If the first-stage polymerization does not contain conjugated dienes, or if it contains conjugated dienes and is 20% by weight or less of the total amount of monomers in the first stage, use a small amount of crosslinking monomer and grafting monomer. It is possible to obtain a polymer having higher impact resistance. As the crosslinkable monomer, for example, an aromatic divinyl monomer such as divinylbenzene, ethylene glycol diacrylate,
Ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, Examples thereof include alkane polyol polyacrylates such as trimethylolpropane trimethacrylate, alkane polyol polymethacrylates, and the like, but butylene glycol diacrylate and hexanediol diacrylate are particularly preferably used. As a grafting monomer,
Examples thereof include allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate, unsaturated carboxylic acid allyl esters such as diallyl itaconate, and the like, and allyl methacrylate is particularly preferably used. Such a crosslinkable monomer and a grafting monomer are each contained in an amount of 0 to 5 of the total amount of the first stage monomer.
It is used in an amount of 0.1% by weight, preferably 0.1 to 2% by weight.

The core of the rubber-like polymer is preferably in the range of 50 to 90% by weight based on the whole core-shell polymer. When the core is less than this weight range or more than this weight range, the effect of improving impact resistance of the resin composition obtained by melt-mixing the produced core-shell polymer may not be sufficient. When the glass transition temperature of the core is higher than −30 ° C., the effect of improving the low-temperature impact resistance may not be sufficient. A glassy polymer is formed in the outermost shell phase (shell phase). Examples of the monomer constituting the glassy polymer include methyl methacrylate and a monomer copolymerizable with methyl methacrylate. These monomers are methyl methacrylate alone or a mixture of monomers copolymerizable with methyl methacrylate, and form a glassy polymer having a glass transition temperature of 60 ° C. or higher. As the monomer copolymerizable with methyl methacrylate,
For example, alkyl acrylate such as ethyl acrylate and butyl acrylate, alkyl methacrylate such as ethyl methacrylate and butyl methacrylate, styrene,
Vinyltoluene, aromatic vinyl such as α-methylstyrene, aromatic vinylidene, acrylonitrile, vinyl cyanide such as methacrylonitrile, vinyl polymerizable monomers such as vinylidene cyanide, but particularly preferably ethyl acrylate, Styrene, acrylonitrile, etc. are used. The outermost shell phase (shell phase) is preferably in the range of 10 to 50% by weight based on the whole core-shell polymer.
When the outermost shell phase is less than or more than this weight range, the effect of improving the impact resistance of the resin composition obtained by melt mixing the resulting core-shell polymer may not be sufficient. Further, an intermediate phase may be present between the first stage and the final polymerization phase. For example, polymerizable monomers having functional groups such as glycidyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, etc.,
The intermediate phase is formed by seed emulsion polymerization of a polymerizing monomer that forms a glassy polymer such as methyl methacrylate, a polymerizing monomer that forms a rubbery polymer such as butyl acrylate, and the like. Such an intermediate phase can be variously selected depending on the desired properties of the core-shell polymer. Further, the polymerization ratio may be appropriately selected depending on the monomer used. For example, when the glassy polymer is used as the intermediate phase, its polymerization rate may be calculated as a part of the shell, and in the case of a rubbery polymer, it may be calculated as a part of the core.

The structure of the core-shell polymer having such an intermediate phase has, for example, a multi-layered structure in which another layer is present between the core and the shell, or the intermediate phase has a fine granular structure in the core. One that has a salami structure that is dispersed. In a more extreme case of a core-shell polymer having a salami structure, the mesophase to be dispersed may form a new core at the center of the core. The core-shell polymer having such a structure may occur when a monomer represented by styrene is used as a monomer constituting the mesophase. In addition, when a core-shell polymer having an intermediate phase is used, in addition to improving impact resistance, the flexural modulus is improved, the heat deformation temperature is increased, the appearance (surface peeling and pearl luster is suppressed, and the change in color tone due to the change in the refractive index). ) Is also improved. In the present invention, the amount of the core-shell polymer (B) added to 100 parts by weight of the polyacetal resin is 1 to 50 parts by weight, preferably 3 to 20 parts by weight. If the addition amount of the core-shell polymer is too small, impact resistance is not sufficiently exerted, and even if it is added excessively, a mechanical property, particularly rigidity, is significantly reduced, and the heat stability is not adversely affected. Occurs.

By adding and blending the core-shell polymer (B) into the polyacetal resin, the toughness can be improved without deteriorating the excellent mechanical properties of the polyacetal resin, but the hinge property is inferior and it is not suitable for hinge parts. It could not be used. Therefore, the present invention is
The component (A) and the component (B) further comprise (C) an oxyalkylene polymer having a molecular weight in the range of 10,000 to 300,000 and having 2 to 8 carbon chains in the main chain. By blending the three components (A), (B), and (C),
It is extremely effective for improving hinge characteristics without impairing the well-balanced characteristics inherent in the polyacetal resin.

In the present invention, examples of the oxyalkylene polymer (C) having 2 to 8 adjacent carbon chains used for such purpose include poly (ethylene oxide), poly (propylene oxide) and poly (butylene-1). , 2-oxide), polyoxolane, polyoxane, polyoxepane, polyoxocan and polyoxonan, and ethylene oxide / propylene oxide copolymers and ethylene oxide / oxolane copolymers. Here, the copolymer means a random copolymer, a block copolymer, a graft copolymer and a mixture thereof. Of these, oxyalkylene polymers having 2 to 4 carbon chains adjacent to each other are preferable, and poly (ethylene oxide),
Poly (propylene oxide), poly (butylene-1,2-
Oxide), polyoxolane and ethylene oxide
Examples thereof include propylene oxide copolymer. Particularly, poly (ethylene oxide) is most preferable. The amount of oxyalkylene polymer (C) added is (A) polyacetal resin 1
1 to 20 parts by weight is suitable for 00 parts by weight, especially 5 to
15 parts by weight is preferred. When the amount is less than 1 part by weight, the effect of improving the hinge properties is small, and when the amount is more than 20 parts by weight, the effect of the improvement reaches saturation, and the original properties of the polyacetal resin are adversely affected.

Such an oxyalkylene polymer (C) gives a hinge molded part made of a polyacetal resin having excellent hinge properties even if it is blended alone with a polyacetal resin, but its impact resistance is not sufficient. Therefore, it is recognized that the combined use of the three components (A + B + C) with the (B) core-shell polymer exerts a remarkable improving effect and has an excellent hinge property. That is, in the molded article obtained by adding and blending the core-shell polymer into the polyacetal resin,
The core-shell polymer is dispersed on the surface in the form of particles of about 0.5 to 2 μm, and when the molded part is bent, the core-shell polymer becomes the starting point and breaks or breaks. Therefore, the one obtained by blending the (A) polyacetal resin with the (B) core-shell polymer is significantly inferior in hinge characteristics. However, when three components (A + B + C) are used in combination, a remarkable improving effect is exhibited, and a remarkable effect of having excellent hinge properties is recognized. Such an effect is that the oxyalkylene polymer (C) has a compatibilizing effect on both the polyacetal resin (A) and the core-shell polymer (B), and therefore lowers the high crystallinity of a normal polyacetal resin and reduces the elastic modulus. It is presumed that this is due to the decrease. When the molecular weight of the oxyalkylene polymer (C) is higher than 300,000, the hinge property is not improved because the oxyalkylene polymer (C)
It is presumed that this is because it is repelled from the amorphous component of the polyacetal resin (A) and does not lower the elastic modulus of the polymer. The action and effect are not always clear, and the present invention is not limited thereby.

The composition of the present invention is preferably supplemented with various known stabilizers to reinforce the heat stabilizer. For this purpose, known antioxidants, nitrogen-containing compounds, alkali or alkaline earth metal compounds are added. It is desirable to use one kind or a combination of two or more kinds. In order to further impart desired properties to the composition of the present invention depending on its purpose, conventionally known additives such as lubricants, nucleating agents, release agents, antistatic agents and other surfactants, or other than the component (C) Organic polymer materials,
It is possible to add one or more kinds of inorganic or organic fibrous, powdery or plate-like fillers. The hinge part of the present invention can be easily prepared by known manufacturing methods and molding methods used as conventional methods for preparing resin compositions. That is, the necessary components are mixed and uniaxial or biaxial
It can be kneaded using a shaft extruder and extruded into pellets for molding, and the composition can be prepared simultaneously with molding by a molding machine. Further, in order to improve the dispersion and mixing of the respective components, a method of pulverizing a part or all of the resin components, mixing and molding the pellets melt-extruded, or the like is possible. Further, the compounds such as the stabilizers and additives may be added at any arbitrary stage, and it is of course possible to add and mix them just before obtaining the final molded product.

[0014]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.
The characteristic evaluations in Examples and Comparative Examples were performed according to the following methods. (1) Evaluation of Hinge Property A test piece having the shape shown in FIG. 1 was molded and evaluated based on the following criteria. Number of samples: n = 10 Test method: Samples at -10 ° C and 50% RH for 24 hours
After leaving it for more than an hour, the hinge part was repeatedly bent 100 times at an angle of 180 degrees under the same conditions.

Evaluation A: The number of broken hinge parts during 100 bendings (the smaller the number, the better).

Evaluation B: The state of the hinge portion after bending 100 times was evaluated by the following criteria and expressed as an average point (the larger the value, the better).

5: Almost no abnormality was observed 4: Micro cracks were generated on the surface of the hinge part 3: Cracks on the surface of the hinge part grew and became large 2: Cracks on the hinge part were further centered That grows toward the edge and the hinge becomes extremely thin 1: The thinned hinge has a cut and is about to cut 0: Broken (2) Surface layer peeling test 1/32 inch test piece surface After the cellophane tape was attached to and peeled off, the peeling condition was visually observed to evaluate the presence or absence of the peeled surface layer. (3) Measurement of melt viscosity Using a Capillograph manufactured by Toyo Seiki Co., Ltd., a melt retention time of 7 minutes after sample introduction, temperature 190 ° C., L = 10 mm, D = 1 m
It was measured at m and a shear rate of 121.6 sec ^-1 . (4) Impact characteristics (Izod impact strength) The resin pellets prepared in the examples and comparative examples were used for in-line injection molding with a mold clamping force of 80 tons (IS80, manufactured by Toshiba).
Test sample at a cylinder temperature of 190 ° C (width
12.7mm, 6.4mm thick, 64mm long)
The Izod impact value was measured with a notch according to the method of TM D 256. A higher Izod impact value is judged to be better. In the Examples and Comparative Examples, "parts" all indicate parts by weight. The methods used in the evaluation of the characteristic values such as mechanical properties in the examples are as follows.・ Molding conditions Nozzle C1 C2 C3 Cylinder temperature (℃) 200 190 180 160 Injection pressure 650 (kg / cm ² ) Injection speed 4.0 (m / min) Mold temperature 80 (℃) Examples 1-6 Various polyacetals shown below A resin (DURACON (trade name) manufactured by Polyplastics Co., Ltd.) was blended with various core-shell polymers shown below and various oxyalkylene polymers shown below in a composition shown in Table 1, and after mixing using a Henschel mixer. A pellet composition was prepared by melt-kneading with a 30 mm twin-screw extruder, and then using this injection molding machine, a test piece was molded under the above-mentioned molding conditions to obtain hinge characteristics and other characteristics. The results are shown in Table 1. Comparative Examples 1 to 8 As shown in Table 2, one or both of the core-shell polymer and the oxyalkylene polymer were blended in the above Examples. Like the case did, was obtained in the same manner polyacetal compositions. In the same manner to prepare test pieces from this composition were evaluated. The results are shown in Table 2.

The abbreviations of the components shown in the table are as follows.

<Polyacetal> A-1 melt index (190 ° C) 2.5 (g / 10min) A-2 melt index (190 ° C) 9.0 (g / 10min) A'-1 melt index (190 ° C 45.0 (g / 10min) ) <Core-shell polymer> B-1 Takeda Yakuhin Kogyo Co., Ltd. Staphyloid (trade name) PO-01143 B-2 Takeda Yakuhin Kogyo Co., Ltd. Staphyloid (trade name) PO-0148 <Oxyalkylene polymer> C -1 Poly (ethylene oxide) molecular weight 20000 C-2 Poly (ethylene oxide) molecular weight 70000 C-3 Poly (ethylene oxide) molecular weight 300000 C'-1 Poly (ethylene oxide) molecular weight 6000 C'-2 Poly (ethylene oxide) molecular weight 500000 <Thermoplastic polyurethane > Takeda Birdish Urethane Co., Ltd., trade name [Elastollan-S80A]

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

As is apparent from the above description and Examples, a polyacetal resin having a specific melt index has a specific core-shell polymer and a molecular weight of 1%.
The hinge part of the present invention comprising a resin composition obtained by adding and blending together an oxyalkylene polymer in the range of 10,000 to 300,000 exhibited excellent hinge characteristics and impact resistance. Examples of applications of such hinge parts include various hinge parts in the fields of automobiles, electric / electronics, building materials, sundries, etc., but more specifically, automotive connectors, electrical equipment connectors, and the like. It is suitable for use in.

[Brief description of drawings]

FIG. 1 is a schematic view of a test piece used for measuring hinge characteristics, and (a), (b), and (c) are a plan view, a side view, and an enlarged view of a hinge portion, respectively. The unit of other numerical values is mm.

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Claims (5)

[Claims] 1. A) ASTM D1238 with a cylinder temperature of 190 ° C.
Melt index measured according to -89 E method is 0.1 ~
To 100 parts by weight of polyacetal resin which is 15 g / 10 minutes (B)
1-50 parts by weight of a core-shell polymer having a rubbery polymer core and a glassy polymer shell and (C) an oxyalkylene polymer 1 having 2 to 8 carbon chains adjacent to each other and having a molecular weight in the range of 10,000 to 300,000 A polyacetal resin hinge part formed by molding a polyacetal resin composition containing up to 20 parts by weight. 2. The core-shell polymer (B) is a core-shell polymer in which substantially no anion is detected.
Hinge parts made of the described polyacetal resin. 3. The (B) core-shell polymer is obtained by emulsion polymerization using a nonionic surfactant and a polymerization initiator in which radicals generated are neutral.
Hinge parts made of the described polyacetal resin. 4. The hinge component made of a polyacetal resin according to claim 1, wherein the shell of the core-shell polymer (B) is a polymer containing methyl methacrylate as a main component. 5. The (C) oxyalkylene polymer is one or more selected from the group consisting of poly (ethylene oxide), poly (propylene oxide) and ethylene oxide / propylene oxide copolymers. 5. The hinge component made of the polyacetal resin according to any one of items 1 to 4.