JP6383744B2 - Polyacetal resin molded product and method for producing the same - Google Patents

Description

  The present invention relates to a polyacetal resin molded product and a method for producing the same.

  Polyacetal resin has high mechanical strength and rigidity, is excellent in oil resistance, organic solvent resistance and self-lubricating properties, is a resin that balances these in a wide temperature range, and has easy workability. Therefore, as representative engineering plastics, it is widely used mainly for mechanical parts and sliding parts such as precision equipment, home appliances and OA equipment, automobiles, industrial materials, sundries. In recent years, the required performance has become higher due to the expansion of the application field of polyacetal resin in recent years. Among these, attempts have been made to improve the appearance and impart metallic luster to enhance the design of a molded article made of polyacetal resin.

  For example, in a hardly adhesive resin, a method for producing a molded body has been proposed which includes blasting the surface of a base material and forming a metal film on the surface by vacuum deposition (see, for example, Patent Document 1). ). In addition, when the method of painting is used to improve the appearance, the paint is also devised. For example, a metal pigment dispersion composed of a flaky metal pigment and a binder or a binder solution with a very low content of products resulting from fatty acid reaction or decomposition has been proposed (for example, see Patent Document 2). Furthermore, a powder coating composition containing a thermosetting resin powder having a flake pigment bonded to the surface has been proposed (see, for example, Patent Document 3).

  In addition, attempts have been made to express metallic luster and impart design properties by molding a resin containing a luster pigment. For example, a method of containing a predetermined amount of a metallic pigment and a colorant that can be optically changed in a thermoplastic resin and a method of containing a gloss pigment for resin addition made of specific aluminum particles have been proposed (for example, Patent Documents). 4, see Patent Document 5).

  Furthermore, a polytrimethylene terephthalate resin included in resin-made automobile exterior parts having excellent appearance, light resistance, and rigidity has been proposed (see, for example, Patent Document 6).

JP 2007-191738 A JP-T 8-510294 WO2002 / 094950 JP 2001-261978 A WO2004 / 026970 WO2003 / 022926

  However, the method for producing a molded article as described in Patent Documents 1 to 3 is not efficient because a molded article having a good appearance can be obtained, but requires a great number of and controlled processes. Furthermore, in consideration of the working environment and the influence of the solvent due to the solvent, it is not always a satisfactory production method.

  Moreover, when using the manufacturing method of a molded article as described in Patent Documents 4 and 5 for a polyacetal resin, the mechanical properties inherent to the polyacetal resin are due to the effects of heat generated during melt mixing and active points on the metal surface. May decrease or the appearance may be insufficiently improved.

  Furthermore, Patent Document 6 describes mixing polyacetal resin and glass fiber, adding aluminum powder to this, and melt-kneading. However, in such a method of manufacturing a molded article, The molded product does not have a good appearance, and a satisfactory molded product cannot be obtained. Further, no other effective method is mentioned as a method for improving the molded article having a good appearance.

  Therefore, in a polyacetal resin molded product used for design parts having mechanical characteristics and sliding characteristics in particular, it is possible to stably obtain a molded product that has both the mechanical properties inherent to the resin and an excellent appearance. A polyacetal resin composition that is gentle to the environment is desired.

  An object of the present invention is to provide a polyacetal resin molded article having an excellent appearance and excellent scratch resistance and chemical resistance.

  As a result of intensive studies to solve the problems of the prior art, the present inventors have found that a polyacetal resin containing a polyacetal resin and a predetermined range of a glittering material, and at least a part of the image definition is a predetermined value or more. By using a molded article, it was found that it had an excellent appearance and was excellent in scratch resistance and chemical resistance, and the present invention was completed.

That is, the present invention is as follows.
[1]
A molded product comprising a polyacetal resin and a bright material of 0.2 to 10 parts by mass with respect to 100 parts by mass of the polyacetal resin,
A polyacetal resin molded product, wherein an image definition of at least a part of the molded product is 20% or more.
[2]
The polyacetal resin molded article according to [1], wherein the polyacetal resin is a polyacetal copolymer.
[3]
The luster material is a metal pigment,
The polyacetal resin molding according to [1] or [2], wherein the shape of the metal pigment is a coin shape or flake shape, and the average particle diameter of the metal pigment is in the range of 3.0 μm or more and 80 μm or less. Goods.
[4]
The polyacetal resin molded product according to any one of [1] to [3], wherein the particle size distribution of the metal pigment has a plurality of peaks having different particle sizes.
[5]
The polyacetal resin molded product according to [4], wherein a difference between a particle diameter of the peak having the largest particle diameter and a particle diameter of the peak having the smallest particle diameter exceeds 5.0 μm.
[6]
The polyacetal resin molded product according to any one of [1] to [5], wherein the metal pigment is an aluminum pigment.
[7]
The polyacetal resin molded product according to any one of [1] to [6], wherein the image definition is 30% or more.
[8]
The polyacetal resin molded product according to any one of [1] to [7], wherein the pencil hardness in JIS-K5400 is H or more.
[9]
The polyacetal resin molded product according to any one of [1] to [8], wherein the maximum depth of corrosion marks after contact with 35% by mass hydrochloric acid for 1 hour is 150 μm or less.
[10]
The polyacetal resin molded product is any one of OA equipment, music, video or information equipment, parts used for communication equipment, industrial parts used for office furniture or residential equipment, and parts used for automobile interior and exterior The polyacetal resin molded product according to any one of [1] to [9].
[11]
A method for producing a polyacetal resin molded product, comprising a step of injection molding a resin using a mold having a mold temperature of 100 ° C. or higher to obtain a polyacetal resin molded product according to any one of [1] to [10] .

  The polyacetal resin molded article according to the present invention has an excellent appearance and is excellent in scratch resistance and chemical resistance.

It is an image figure which shows the process of obtaining a preparation polyacetal copolymer (component A) from a dry polymer. It is an image figure which shows the process of obtaining a polyacetal resin composition from the intermediate | middle pellet which consists of component A, and component B. FIG. It is an image figure of the polymerization apparatus of the polyacetal homopolymer used for the Example and the comparative example.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited to the following contents. The present invention can be implemented with various modifications within the scope of the gist.

[Polyacetal resin molded product]
The polyacetal resin molded product of the present embodiment (hereinafter also simply referred to as “molded product”) includes a polyacetal resin and a bright material having a mass of 0.2 to 10 parts by mass with respect to 100 parts by mass of the polyacetal resin. including. The image definition of at least a part of the molded product is 20% or more.

  In the polyacetal resin molded product of this embodiment, the image clarity of a part or the whole is 20% or more, preferably 25% or more, and more preferably 30% or more. When the image clarity of the polyacetal resin molded product is 20% or more, the polyacetal resin molded product exhibits a good appearance and can improve scratch resistance and chemical resistance.

  The method for setting the image clarity of a part or the whole of the polyacetal resin molded product to 20% or more is not particularly limited, but when the polyacetal resin molded product is molded by injection molding, for example, 100 ° C or higher, preferably It can be obtained by filling a mold cavity whose temperature is adjusted to 110 ° C. or higher with a molten polyacetal resin. Here, when the temperature of the mold cavity is set to 100 ° C. or more, the amorphous part of the molded product tends to be thinned, and not only the image sharpness is improved, but also scratch resistance and chemical resistance are improved. Tend to.

In addition, when a molding method having a process of heating and cooling a mold in a molding cycle, for example, when filling a mold with a molten polyacetal resin, the mold temperature is kept at 100 ° C. or more, and Use of heat and cool molding that lowers the mold temperature to about 80 ° C. upon completion of filling or at an arbitrary timing is also an effective means for increasing the image definition of a part or the whole of the polyacetal resin molded product to 20% or more. It is.
In the prior art, the mold temperature when the polyacetal resin is injection-molded is such that the molding cycle has an appropriate length, the dimensional change after molding, and the shrinkage rate are in an allowable range. Generally, it is in the range of ° C.

The image sharpness refers to a value measured according to “Plastics—How to determine image sharpness” defined in Japanese Industrial Standard (JIS K 7374). It is an index of the degree to which the image of an object that is reflected on the surface of the plastic looks clear and distorted. In this embodiment, an optical comb perpendicular to the beam axis of the reflected light from the test piece is obtained by measurement through an optical comb that moves the amount of light reflected from the test piece by incident light having an incident angle of 60 °. To obtain the light quantity (M) when there is a comb transmission part on the optical axis and the light quantity (m) when there is a comb light-shielding part, and the difference (M−m) and the sum ( M + m) and a ratio (%), which is obtained by the following formula.
Image sharpness (%) = (M−m) ÷ (M + m) × 100

  The image definition in the present embodiment is obtained when the width of the optical comb is set to 1.0 mm with respect to the amount of light reflected on the molded product using “image clarity measuring device“ ICM-1T ”” manufactured by Suga Test Instruments Co., Ltd. Measured value.

  In the molded product of this embodiment, the pencil hardness in JIS-K5400 is preferably H or higher, and more preferably 2H or higher. In order to obtain a molded article having a pencil hardness of H or higher, the thickness of the amorphous layer present in the surface layer of the polyacetal resin molded article may be reduced. The pencil hardness is measured by the method described in Examples described later.

  In the molded product of this embodiment, the maximum depth of corrosion marks after contact with 35% by mass hydrochloric acid (dilute hydrochloric acid having a total amount of 100% by mass) for 1 hour is preferably 150 μm or less, and is 120 μm or less. Is more preferable, and it is further more preferable that it is 100 micrometers or less. In order to obtain a molded product in which the maximum depth of the corrosion mark is 150 μm or less, the thickness of the amorphous layer present in the surface layer of the polyacetal resin molded product may be reduced. The maximum depth of the corrosion mark is measured by the method described in Examples described later.

[Polyacetal resin composition]
The polyacetal resin composition of the present embodiment (hereinafter also simply referred to as “composition”) includes a polyacetal resin and a glittering material. In addition, the polyacetal resin composition of the present embodiment preferably further includes a hindered amine-based material and a formaldehyde inhibitor, as described later, and further includes additives such as a polyalkylene glycol, a hydrazide compound, and a colorant. It is also preferable. The polyacetal resin molded product of the present embodiment is obtained by molding the polyacetal resin composition of the present embodiment.

[Polyacetal resin]
The polyacetal resins of the present embodiment are roughly classified into two types: polyacetal homopolymers (hereinafter also simply referred to as “homopolymers”) and polyacetal copolymers (hereinafter also simply referred to as “copolymers”). Is appropriately selected from these two types according to the environment in which the product is used, the required performance, and the like. Moreover, you may use a homopolymer and a copolymer together.

  The fluidity of the polyacetal resin is not particularly limited, and is selected depending on the required performance and moldability of the molded product to be used. The fluidity is preferably about 9.0 g / 10 min as a melt flow rate (hereinafter also referred to as “MFR”) value. The melt flow rate is measured in accordance with ISO standard 1133 condition D, and in particular, it is a measured value at a measurement temperature of 190 ° C. and a load of 2.16 kg.

  For the polyacetal resin, it is preferable to select a polymer with high fluidity for products with thin product thickness, products with a long flow length from the gate to the flow end, and products with high required dimensional accuracy. It is preferable to select a polymer having a high viscosity for products in which a load is applied.

[Polyacetal homopolymer]
The polyacetal resin of the present embodiment is preferably a polyacetal homopolymer because it can maintain high impact and durability when formed into a molded product. The polyacetal homopolymer of this embodiment can be obtained by the polymerization process shown below.

[Polymerization process]
The polymerization step for obtaining the polyacetal homopolymer can be carried out using a known slurry polymerization method (see, for example, Japanese Patent Publication Nos. 47-6420 and 47-10059). By the polymerization step, a crude polyacetal of a polyacetal homopolymer whose terminal is not stabilized can be obtained.

<Main raw material: Monomer>
The formaldehyde of the monomer (main monomer) that is the main raw material of the polyacetal homopolymer of the present embodiment is not particularly limited, but is purified to have a stable molecular weight resin continuously, and has a low impurity concentration, and A stable formaldehyde gas is preferred. As a purification method of formaldehyde, a known method (for example, see Japanese Patent Publication No. 5-32374 and Japanese Patent Publication No. 2001-521916) can be used.

  As the formaldehyde gas, it is preferable to use a gas that does not contain impurities such as water, methanol, formic acid and the like as much as possible, which has a polymerization termination or chain transfer action during the polymerization reaction. By preventing these impurities from being excessively present, it tends to be possible to prevent the target molecular weight product from being obtained due to an unexpected chain transfer reaction. In particular, the water content is preferably 100 mass ppm or less, and more preferably 50 mass ppm or less.

<Chain transfer agent>
In the polymerization step, it is preferable to use a chain transfer agent. The chain transfer agent is not particularly limited, and examples thereof include alcohols and acid anhydrides (for example, acetic anhydride). In order to obtain a block polymer or a polyacetal homopolymer of a branched polymer, examples of the chain transfer agent include polyols, polyether polyols, and polyether polyol polyol alkylene oxides.

  As the main monomer, it is preferable to use a chain transfer agent that does not contain impurities as much as possible. In particular, the content of water is preferably 2000 mass ppm or less, and more preferably 1000 mass ppm or less. As a method for obtaining such a chain transfer agent with few impurities, for example, when the moisture content of the obtained chain transfer agent exceeds a specified value, after bubbling with dry nitrogen, an adsorbent such as activated carbon or zeolite The method of adjusting to content of the target water by removing an impurity using and refine | purifying is mentioned.

  A chain transfer agent may be used individually by 1 type, and may use 2 or more types together.

<Polymerization catalyst>
In the polymerization step, it is preferable to use a polymerization catalyst. Although it does not specifically limit as a polymerization catalyst, For example, the onium salt type | system | group polymerization catalyst represented by following General formula (1) is mentioned.
[R ¹ R ² R ³ R ⁴ M] ⁺ X ⁻ (1)
In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent an alkyl group, M represents an element having an independent electron pair, and X represents a nucleophilic group. .

  Among the onium salt polymerization catalysts represented by the general formula (1), quaternary ammonium salt compounds and quaternary phosphonium salt compounds are preferable, and tetramethyl / ammonium / bromide, dimethyl / distearyl / Ammonium iodide and dimethyl distearyl ammonium acetate.

  Although a superposition | polymerization process is not specifically limited, It can carry out using a conventionally well-known reactor. Examples of the reactor include a batch type reaction tank with a stirrer, a continuous type kneader, a twin screw type continuous extrusion kneader, and a twin screw paddle type continuous mixer. Among these, a reactor having a structure capable of heating and cooling the reaction mixture is preferable.

[Terminal stabilization process]
The polyacetal homopolymer obtained by the above polymerization step is preferably subjected to a step of stabilizing the terminal (terminal stabilization step). The method for stabilizing the terminal is not particularly limited. For example, as shown below, there are a method of blocking the terminal with an ethyl group, a method of blocking the terminal with an acetyl group, and a method of blocking the terminal with an ester group. Can be mentioned.

  Examples of the method of blocking the end with an ethyl group (ethylation reaction) include the method described in JP-B 63-452. Further, as a method for blocking the end with an acetyl group (acetylation reaction), for example, a method in which a large amount of acid anhydride described in US Pat. No. 3,459,709 is used in a slurry state, and the US The method of performing in the gaseous phase using the acid anhydride gas as described in patent 3,172,736 is mentioned.

  In the method of blocking the terminal with an ethyl group, examples of the ethylating agent to be used include orthoester. Specific examples include orthoesters of aliphatic or aromatic acids and aliphatic, alicyclic or aromatic alcohols, specifically methyl or ethyl orthoformate, methyl or ethyl orthoacetate, methyl or ethyl It can be selected from orthoesters such as orthobenzoate and orthocarbonates such as ethyl orthocarbonate.

  In the ethylation reaction, Lewis acid type catalysts such as medium strength organic acids such as p-toluenesulfonic acid, acetic acid, and hydrobromic acid, and medium strength mineral acids such as dimethyl and diethyl sulfate are used for the above ethylation. It is preferable to carry out by introducing 0.001 part by mass or more and 0.02 part by mass or less with respect to 1 part by mass of the agent.

  The solvent used for the ethylation reaction is not particularly limited, but low-boiling point aliphatic, alicyclic, and aromatic hydrocarbons such as pentane, hexane, cyclohexane, and benzene, and halogens such as aromatic hydrocarbons, methylene chloride, chloroform, and carbon tetrachloride. Preferred is an organic solvent of a modified lower aliphatic compound.

When the terminal of the homopolymer is blocked with an ester group, an organic acid anhydride represented by the following general formula (2) is exemplified as the organic acid anhydride used for esterification.
R ¹ COOCOR ² (2)
In formula (2), R ¹ and R ² each independently represents an alkyl group. R ¹ and R ² may have the same structure or different structures.

  Among the organic acid anhydrides represented by formula (2). Propionic anhydride, benzoic anhydride, acetic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, and phthalic anhydride are preferred, and acetic anhydride is more preferred.

  Moreover, an organic acid anhydride can be used alone or in combination of two or more.

  In the method of performing ester group blocking in the gas phase, if the onium salt polymer catalyst remains in the homopolymer, the onium salt polymerization catalyst promotes the decomposition reaction of the homopolymer when end-blocking. As a result, the polymer yield in the terminal stabilization step is significantly reduced and the homopolymer may be colored. For example, the onium salt-based polymerization catalyst is removed by the method described in JP-A-11-92542. After that, it is preferable to perform end-capping.

It is preferable to reduce the concentration of the terminal hydroxyl group to 5 × 10 ⁻⁷ mol / g or less by blocking the end of the homopolymer with an ethyl group and / or an ester group, and to 0.5 ⁻⁷ mol / g or less. More preferably.

  The homopolymer that has undergone terminal stabilization is preferably pelletized using an extruder in order to ensure handling after the drying treatment.

[Polyacetal copolymer]
The polyacetal resin of the present embodiment is preferably a polyacetal copolymer, since production stability during melt kneading can be maintained. The polyacetal copolymer of this embodiment can be obtained by the polymerization process described below. The polyacetal copolymer of the present embodiment is not particularly limited, but is preferably a polymer having an oxymethylene group in the main chain and an oxyalkylene unit having 2 or more carbon atoms in the molecule.

[Polymerization process]
The polymerization step for obtaining the polyacetal copolymer of the present embodiment is not limited to the method described in the present specification, but may be a known polymerization method (for example, US-A-3027352, US-A-3803094, DE-C-1161421). DE-C-1495228, DE-C-1720358, DE-C-3018898, JP-A-58-98322, JP-A-7-70267). By the polymerization step, a crude polymer of polyacetal copolymer is obtained.

<Main raw material: Monomer>
The main raw material (main monomer) of the polyacetal copolymer of the present embodiment is not particularly limited, but is preferably a cyclic oligomer such as formaldehyde, trioxane that is a trimer thereof, or tetraoxane that is a tetramer.

  Although the monomer that is not the main raw material of the polyacetal copolymer of the present embodiment (a monomer having a smaller content in the copolymer than the main monomer, hereinafter referred to as “comonomer”) is not particularly limited, for example, the number of carbon atoms in the molecule Examples thereof include cyclic ethyl compounds having two or more oxyalkylene units. Among them, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-propanediol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, diethylene glycol formal, 1 1,3,5-trioxepane, 1,3,6-trioxocan, and a mono- or di-glycidyl compound capable of forming a branched or crosslinked structure in the molecule are preferably used. In this embodiment, when the main monomer is converted to trioxane (formaldehyde trimer), the copolymerization amount of the comonomer component is preferably 1.0 mol or more and 10 mol or less, more preferably 1.0 mol with respect to 100 mol of trioxane. It is 5.0 mol or less. By setting the copolymerization amount of the comonomer component within a preferable range, the stability of the polymerization reaction tends to be further improved, and mechanical properties such as strength and rigidity tend to be further improved.

  As the main monomer and comonomer of the polyacetal copolymer, it is preferable to use a monomer that does not contain impurities such as water, methanol, formic acid or the like that have a polymerization termination or chain transfer action during the polymerization reaction. By making these impurities not excessively present, it tends to be possible to prevent the desired molecular weight product from being obtained due to an unexpected chain transfer reaction. In particular, the content of impurities that induce hydroxyl groups in the polymer end groups is preferably 30 mass ppm or less, more preferably 10 mass ppm or less, and even more preferably 3.0 mass ppm, based on the total monomer amount. It is as follows. As a method for obtaining a desired low-impurity main raw material, a known method (for example, JP-A-3-123777 and JP-A-7-33761 for the main monomer, JP-A-49-62469 for the comonomer) is known. And Japanese Patent Application Laid-Open No. 5-271217).

<Chain transfer agent>
In the polymerization step, it is preferable to use a chain transfer agent. Although it does not specifically limit as a chain transfer agent, The dialkyl acetal (for example, methylal) of formaldehyde whose alkyl group is lower aliphatic alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl, and its oligomer, methanol, ethanol, propanol , Lower aliphatic alcohols such as isopropanol and butanol are preferred. In order to obtain a long-chain branched polyacetal copolymer, polyether polyol and polyether polyol alkylene oxide are preferred. In order to obtain a block polyacetal copolymer, a polymer having at least one hydroxyl group, carboxyl group, amino group, ester group or alkoxy group and having a number average molecular weight of 400 or more may be chain-transferred. preferable. In addition, the said chain transfer agent may be used individually by 1 type, or may use 2 or more types together. Among these chain transfer agents, those having less unstable terminal formation are preferred.

<Polymerization catalyst>
In the polymerization step, it is preferable to use a polymerization catalyst. The polymerization catalyst for the polyacetal copolymer is not particularly limited, but a cationically active catalyst such as a Lewis acid, a protonic acid, and an ester or an anhydride thereof is preferable. Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. Specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, pentachloride. Examples thereof include phosphorus, antimony pentafluoride, and complex compounds or salts thereof. Specific examples of the protonic acid, its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, and trimethyloxonium hexafluorophosphate. Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable. Specifically, boron trifluoride Preferred examples include diethyl ether and boron trifluoride di-n-butyl ether. The amount of the polymerization catalyst used is 1.0 with respect to 1 mol of the total amount of trioxane and cyclic ethyl and / or cyclic formal. The amount is preferably from 10 × 10 ⁻⁶ mol to 1.0 × 10 ⁻³ mol, and more preferably from 5.0 × 10 ⁻⁶ mol to 1.0 × 10 ⁻⁴ mol. By setting it as such a range, it exists in the tendency which the reaction stability at the time of superposition | polymerization and the thermal stability of the molded object obtained will improve more. In the present embodiment, a cocatalyst may be used as necessary.

[Terminal stabilization process]
It is preferable that the polyacetal copolymer of this embodiment performs the process (terminal stabilization process) which decomposes and removes the unstable terminal part contained in the copolymer obtained by the polymerization process. The method for decomposing and removing the unstable terminal portion is not particularly limited. For example, a decomposing / removing method that is a known basic substance using a vented single-screw extruder or a vented twin-screw extruder is used. In the presence of the agent, the crude polymer can be melted to decompose and remove unstable terminal portions. Here, when performing melt-kneading for terminal stabilization, it is preferable to perform deaeration by substitution with an inert gas or single-stage and multistage vents in order to maintain the quality and working environment. The melt kneading temperature is preferably not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. Furthermore, in the terminal stabilization step, it is preferable to perform granulation by adding a known stabilizer that can be added to the polyacetal resin, and granulating. Further, at the time of granulation, melt kneading may be performed while adding a hindered amine-based substance described later in advance.

  The MFR (melt flow rate; ISO 1133 condition D, load 2.16 kg, cylinder temperature 190 ° C.) of the obtained polyacetal copolymer is preferably adjusted to 2.5 g / 10 min to 40 g / 10 min. It is more preferable to adjust to 0 g / 10 min or more and 30 g / 10 min or less, and it is more preferable to adjust to 3.5 g / 10 min or more and 25 g / 10 min or less. By setting it as such a range, it exists in the tendency which can maintain productivity and the weld characteristic of the molded object obtained more favorably.

  The decomposition / removal agent used in the method for removing the unstable terminal portion is not particularly limited. For example, aliphatic amines such as ammonia, triethylamine, and tributylamine; alkali metals and alkaline earth metals represented by calcium hydroxide And known basic substances such as hydroxides, inorganic weak acid salts and organic weak acid salts.

Among the decomposition / removal agents, at least one quaternary ammonium compound represented by the following general formula (1) is preferable, and the polyacetal copolymer stabilized with the decomposition / removal agent is unstable. There is a tendency that the end portion hardly remains.
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ^n- (3)
In Formula (3), R ¹ , R ² , R ³ , and R ⁴ are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group in which an unsubstituted alkyl group having 1 to 30 or a substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms having 1 to 1 carbon atoms 30 shows an alkylaryl group substituted with 30 unsubstituted alkyl groups or substituted alkyl groups, and the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. In the unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group, a hydrogen atom may be substituted with a halogen. n shows the integer of 1-3. X represents a hydroxyl group or an acid residue of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid inorganic thioacid, or an organic thioacid having 1 to 20 carbon atoms.

  The compound of the quaternary ammonium salt is not particularly limited. For example, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexa Methylenebis (trimethylammonium), decamethylene-bis- (trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2 -Hydroxyethyl) ammonium, tri-n-butyl (2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammo , Tripropylbenzylammonium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2- And hydroxides such as hydroxyethyl) ammonium and tetrakis (hydroxyethyl) ammonium.

In addition, quaternary ammonium salt compounds include hydrates other than halogenated, such as hydrogen azide; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, hypochlorous acid, Oxo acid salts such as chloric acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid, tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, capron Examples thereof include carboxylic acid salts such as acid, caprylic acid, capric acid, benzoic acid and oxalic acid. Among these, hydroxide (OH ⁻ ), sulfuric acid (HSO ₄ −, SO ₄ ²⁻ ), carbonic acid (HCO ₃ ⁻ , CO ₃ ²⁻ ), boric acid (B (OH) ₄ ⁻ ), and carboxylic acid Of these carboxylic acids, formic acid, acetic acid, and propionic acid are more preferable. These quaternary ammonium compounds may be used alone or in combination of two or more.

The addition amount of the quaternary ammonium compound is 0.05 mass ppm or more and 50 mass ppm or less in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (A) with respect to the total amount of the copolymer. It is preferable that
P × 14 / Q (A)
In the formula (A), P represents a concentration (mass ppm) with respect to the copolymer of the quaternary ammonium compound, “14” represents the atomic weight of nitrogen, and Q represents the molecular weight of the quaternary ammonium compound.

  The quaternary ammonium compound may be added in advance before the copolymer is melted, or may be added to the melted crude polymer.

  In the present embodiment, ammonia, triethylamine, a boric acid compound or the like, which is a known decomposition / removal agent, and a quaternary ammonium compound may be used in combination.

(Bright material)
The polyacetal resin composition according to the present embodiment includes 0.2 to 10 parts by mass of a bright material with respect to 100 parts by mass of the polyacetal resin. The content of the glittering material is preferably 0.3 parts by mass or more and 8.0 parts by mass or less, and more preferably 0.4 parts by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin. When the content of the glittering material is 0.2 parts by mass or more and 10 parts by mass or less, the mechanical characteristics inherent in the resin can be maintained and a good appearance can be exhibited.

  The bright material is not particularly limited as long as it reflects light and improves the brightness of the polyacetal resin molded product, and examples thereof include metal pigments, metal-coated glass, and mica.

<Metal pigment>
The glitter material of the present embodiment is preferably a metal pigment. The shape of the metal pigment is not particularly limited, but it is more preferably a coin shape or flake shape.

  The “coin shape” is a shape called a disk shape or a disk shape, and indicates a shape in which the surface of the particle is high and the edge portion of the particle is smooth. Coin-like metal pigments tend to provide molded articles with relatively high brightness. On the other hand, the term “flakes” refers to a shape called corn flakes or scales, and the surface smoothness of the particles is lower than that of coins and the edges of the particles are jagged. .

  In the metal pigment, the average particle thickness t (average shape ratio: average particle thickness t / average particle size D) with respect to the average particle size D is preferably 0.6 or less, more preferably 0.4 or less. By making the shape of the metal pigment within this range, the metal pigment is well dispersed when melt-mixed with the polyacetal resin, and the appearance can be efficiently achieved with a smaller addition amount. The metal pigment is preferably one having a smooth surface and no cracks in the peripheral portion because the particles are less likely to be broken during kneading with the polyacetal resin.

The average particle thickness t of the metal pigment of the present embodiment can be determined by the following method, for example. After washing the metal pigment with acetone and drying it, the mass w (g) was measured, and the coating area S (cm ² ) when this was evenly floated on the water surface was measured, and the WCA (water surface diffusion coating area; S / w) was calculated. Derived and calculated by substituting into the following formula (B).
Average particle thickness t (μm) = 4000 / (S / w) (B)

Further, the average particle diameter D of the metal pigment of the present embodiment is a value (D ₅₀ ) of 50% of the particle diameter distribution measured by a laser diffraction particle size distribution measuring device. The average particle diameter (D ₅₀ ) of the metal pigment used in the present embodiment is preferably in the range of 3.0 μm or more and 80 μm or less, more preferably in the range of 4.0 μm or more and 50 μm or less, and 4.0 μm or more. More preferably, it is in the range of 40 μm or less. By using a metal pigment having an average particle diameter in such a range, the production stability at the time of granulation can be further maintained, and the resin composition can retain the toughness that is the mechanical characteristic inherent in the resin. There is a tendency.

  The average particle thickness t of the metal pigment is not particularly limited, but is preferably in the range of 0.05 μm to 1.0 μm, and more preferably in the range of 0.08 μm to 0.8 μm. preferable. By using a metal pigment having an average particle thickness in such a range, when kneading with a polyacetal resin, the particles are less likely to be damaged, and the physical properties balance between strength and toughness is maintained, and the weld appearance of the molded body is further improved. Tend to be.

  Further, depending on the combination, the physical property balance between strength and toughness can be improved, so two or more kinds of metal pigments may be used.

  At least one kind of metal pigment has a particle size distribution with a certain width, and its peak value is preferably the average particle size. Moreover, it is preferable that the particle size distribution of the metal pigment used for the polyacetal resin molded product of this embodiment has a plurality of peaks having different particle sizes. Such a metal pigment can be obtained by using a plurality of types of metal pigments having different average particle diameters in combination. By having a plurality of peaks with different particle size distributions, it tends to be possible to obtain a polyacetal resin molded article having a good balance between brightness and granularity, which is a measure of a design surface having metallic luster. .

Here, “luminance feeling” is indicated by “Fr value (flop value)” measured by “Spectrophotometer“ BYK-mac ”” manufactured by BYK-Gardner GmbH, and has a flop index, Flop Index (F. I.), and the brightness (L ^* ₁₅ °, L ^* ₄₅ °) of the light reflected at the angles of 15 °, 45 °, and 110 ° with the regular reflection angle of the incident light as the reference line , L ^* ₁₁₀ °), and is calculated from the following formula.
Fr value = 2.69 × (L ^* ₁₅ ° −L ^* ₁₁₀ °) ^1.11 ÷ L ^* ₄₅ ° ^0.86

  The “graininess” is a value indicated by a “G (Graininess) value” measured by the “BYK-mac”, and is also referred to as an AG value. It tends to be proportional to the diameter.

  As the particle diameter of the metal pigment increases, the G value tends to increase and the Fr value tends to decrease. Here, as a general criterion, it is often determined that the Fr value exceeds 14 and that the G value exceeds 1.8 is determined to be good. However, the superiority or inferiority of the design property of the molded product is not necessarily determined only by the Fr value and the G value. For this reason, for example, a molded product (designability) having an Fr value of 15 and a G value of 1.4 may be favored more than a molded product having an Fr value of 10 and a G value of more than 4.

  Further, in a molded article using a metal pigment and an organic and / or inorganic dye / pigment in combination, the Fr value tends to decrease, but this does not necessarily mean that the design property is poor.

  On the other hand, the particle size distribution of a metal pigment having a plurality of peaks with different particle sizes is such that the difference between the particle size of the peak with the largest particle size and the particle size of the peak with the smallest particle size exceeds 5.0 μm. Is preferably 10 μm or more. In order to obtain such a metal pigment, for example, metal pigments having a plurality of particle size peaks different in size may be mixed. When mixing and using metal pigments having a plurality of different particle sizes of different sizes, the mixing ratio is not limited. By increasing the mass ratio, it tends to be possible to obtain a polyacetal resin molded product having a good balance between brightness (Fr value) and graininess (G value). Here, the “peak particle size” refers to the particle size when the maximum value of the peak is shown in the particle size distribution of one peak.

  Although it does not specifically limit as a metal pigment used for this embodiment, An aluminum pigment is preferable. Among these, powder aluminum which has been produced mainly with high purity aluminum and has glitter is more preferable.

  The powdery aluminum of the present embodiment is one in which aluminum is in the form of particles, and it is more preferable to have an oxide film on the surface appropriately. By having an appropriate oxide film, it tends to be able to maintain the corrosion resistance and temporal stability of the particles while maintaining the high reflectivity unique to aluminum.

  Further, the purity of the powdered aluminum of the present embodiment is not particularly limited, but other metals may be contained as impurities or alloy components as long as the effects of the present invention are not hindered. Examples of impurities or alloy components include Si, Fe, Cu, Mn, Mg, and Zn.

  The powdered aluminum of the present embodiment can be produced, for example, by a known method. As the method, for example, atomized powder, cutting powder, foil powder, vapor deposited powder, aluminum powder obtained by other methods is selected in advance by primary classification, etc., in the coexistence of a grinding medium composed of a grinding aid or solvent. In addition, it can be obtained by wet pulverization with a ball mill, attritor, planetary mill, vibration mill, etc., and sieve classification under a wet condition, followed by solid-liquid separation with a filter press or the like. The end may be flaky (uneven) or curved. The pulverization medium used here is preferably as small as possible because the amount of oxygen contained in the particles increases when excessively added. The oxygen content is preferably 0.05% by mass or more and 1.0% by mass or less with respect to the total amount of powdered aluminum (100% by mass), and non-dispersed infrared absorption using an oxygen analyzer or the like. Measured by the method.

<Metal-coated glass>
Although it does not specifically limit as metal-coated glass of this embodiment, For example, what coated the metal oxide to the flake shaped glass used as a base material is mentioned. “Flake glass” refers to fine glass powder that is in the form of thin plates or scales. Although it does not specifically limit as a metal oxide to coat | cover, For example, a titanium oxide and an iron oxide are mentioned. Among these, titanium oxide is preferable from the viewpoint of brightness. The titanium oxide may be either anatase type or rutile type, but the rutile type is preferred from the viewpoint of stability with the resin. The metal-coated glass is white when the average thickness of the metal oxide to be coated is 40 nm or more and 60 nm or less, yellow when it is 60 nm or more and 80 nm or less, red when 80 nm or more and 100 nm or less, and blue when it is 100 nm or more and 130 nm or less. Tend to be able to. The method for coating the flaky glass powder with the metal oxide is not particularly limited, and generally known production methods can be used. Examples of the method include a sputtering method, a sol-gel method, a chemical vapor deposition method, and a liquid phase deposition method.

  The average particle size of the metal-coated glass is preferably in the range of 5.0 μm to 600 μm, more preferably in the range of 75 μm to 125 μm, from the balance with impact resistance. The aspect ratio is preferably in the range of 2.0 to 60 and more preferably in the range of 3.0 to 20 from the viewpoint of strength.

<Mica>
Although it does not specifically limit as mica of this embodiment, For example, natural mica and synthetic mica are mentioned.

  Although it does not specifically limit as natural mica, For example, muscovite, biotite, and phlogopite are mentioned. Mica may be coated with a metal oxide. The metal oxide in this case is not particularly limited, and examples thereof include titanium oxide, iron oxide, and zinc oxide. Among these, titanium oxide is preferable from the viewpoint of brightness. The titanium oxide may be either anatase type or rutile type, but the rutile type is preferred from the viewpoint of stability with the resin. The coverage of the metal oxide in mica is preferably in the range of 20% by mass to 50% by mass, and in the range of 20% by mass to 45% by mass with respect to the total amount of mica (100% by mass). It is more preferable. The method for producing mica is not limited and may be, for example, generally a highland production method (for example, the production method described in JP-A-10-279828).

  The average particle size of mica is preferably in the range of 2.0 μm to 200 μm, more preferably in the range of 5.0 μm to 100 μm, from the viewpoint of impact resistance. The aspect ratio of mica is preferably in the range of 2.0 to 2000, and more preferably in the range of 5.0 to 1000.

<Hindered amine substances>
It is preferable that the polyacetal resin composition of this embodiment further contains a hindered amine-based material. The content of the hindered amine material is preferably 0.20 parts by mass or more and 2.0 parts by mass or less, more preferably 0.25 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the polyacetal resin contained in the composition. It is not more than part by mass, and more preferably not less than 0.30 part by mass and not more than 1.2 parts by mass. By setting it as such a range, it exists in the tendency for a molded article to hold | maintain the outstanding external appearance. A hindered amine type material may be used individually by 1 type, and may use 2 or more types together.

式（４）中、Ｘは、水素原子、ヒドロキシル基、アルキル基、又はアシル基を示す。Ｒ₁〜Ｒ₄は、各々独立に、アルキル基を示す。この中でも、Ｘが水素原子を示す、下記一般式（５）で表されるヒンダードアミン系物質がより好ましい。この構造を有することにより、生産時に高い安定性を保持することが可能となる傾向にある。 The hindered amine-based substance preferably includes, for example, a substance having a piperidine derivative structure represented by the following general formula (4).

In formula (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, or an acyl group. R _{1 to} R ₄ each independently represents an alkyl group. Among these, a hindered amine material represented by the following general formula (5), in which X represents a hydrogen atom, is more preferable. By having this structure, it tends to be possible to maintain high stability during production.

式（５）中、Ｒ₁〜Ｒ₄は、一般式（４）で示すものと同義である。

In formula (5), R < ₁ > -R < ₄ > is synonymous with what is shown by General formula (4).

  Examples of the hindered amine-based substance represented by the general formula (5) include 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (phenylacetoxy) -2,2,6,6-tetramethylpiperidine 4-benzoyloxy-2,2,6,6-tetramethyl Examples include piperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, and 4-stearyloxy-2,2,6,6-tetramethylpiperidine. In addition, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethyl Piperidine, 4- (ethylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy)- 2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidine) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl)- Oxalate, bis (2,2,6,6-tetramethyl-4-piperidyl) -malonate, bis (2,2,6,6-tetramethyl-4-piperi Le) - sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) - adipate, and bis (2,2,6,6-tetramethyl-4-piperidyl) - terephthalate may be mentioned. In addition, 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -ethane, α, α′-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -P-xylene, bis (2,2,6,6-tetramethyl-4-piperidyl) tolylene-2,4-dicarbamate, bis (2,2,6,6-tetramethyl-4-piperidyl) -hexa Methylene-1,6-dicarbamate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,5-tricarboxylate, and tris (2,2,6,6- Mention may also be made of tetramethyl-4-piperidyl) -benzene-1,3,4-tricarboxylate. Of these, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate is preferred.

<Formaldehyde inhibitor>
The polyacetal resin composition of this embodiment further includes one or more formaldehyde inhibitors selected from the group consisting of aminotriazine compounds, guanamine compounds, urea compounds, and carboxylic acid hydrazide compounds. Is preferred. Further, the content of the formaldehyde inhibitor is more preferably 0.005 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin.

  Although it does not specifically limit as an amino triazine type compound, For example, Melamine; Melamine condensates, such as melam, melem, melon; Melamine resin, such as melamine formaldehyde resin; N, N ', N "-mono, bis, Tris, tetrakis , Pentakis, or hexakis (o-, m- or p-hydroxyphenylmethyl) melamine, and the like.

  Although it does not specifically limit as a guanamine type compound, For example, aliphatic guanamine type compounds, such as a valerologamine, a caproguanamine, a heptanoguanamine, a capriloganamin, a stealog anamine; , Cyclopentacarboguanamine, norbornenecarboguanamine, cyclohexenecarboguanamine, norbornanecarboguanamine, and alicyclic guanamine compounds such as functional group-substituted derivatives thereof, pimeloganamin, speroguanamine, azeroguanamine, sebacoguanamine, etc .; Aromatic guanamine compounds such as benzoguanamine, α- or β-naphthguanamine and their functional group-substituted derivatives; phthaloguanamine, isophthaloguanamine, tele; Polyguanamines such as phthaloguanamine, naphthalenediguanamine, biphenylene diguanamine; Aralkyl or aralkyleneguanamines such as phenylacetoguanamine, β-phenylpropioguanamine, o-, m- or p-xylylenebisguanamine; acetal group-containing Examples include heteroatom-containing guanamine compounds such as guanamines, dioxane ring-containing guanamines, tetraoxospiro ring-containing guanamines, and isocyanuric ring-containing guanamines.

  The functional group-substituted derivative in the alicyclic guanamine-based compound is not particularly limited. For example, alkyl group, hydroxy group, amino group, acetamino group, nitrile group, carboxy group, alkoxycarbonyl group, carbamoyl group, alkoxy group, phenyl And derivatives in which 1 to 3 functional groups such as a group, cumyl group, and hydroxyphenyl group are substituted with cycloalkane residues. In addition, the functional group-substituted derivative in the aromatic guanamine compound is not particularly limited. For example, an alkyl group, a hydroxy group, an amino group, an acetamino group, a nitrile group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, an alkoxy group, Derivatives in which functional groups such as phenyl group, cumyl group, hydroxyphenyl group and the like are substituted with 1 to 5 phenyl residues of benzoguanamine or naphthyl residue of naphthoguanamine, more specifically, o-, m- or p-toluguanamine, o-, m- or p-xyloganamine, o-, m- or p-phenylbenzoguanamine, o-, m- or p-hydroxybenzoguanamine, 4- (4'-hydroxyphenyl) benzoguanamine, o -, M- or p-nitrile benzoguanamine, 3,5-dimethyl- - hydroxy benzoguanamine, and 3,5-di -t- butyl-4-hydroxy benzoguanamine are exemplified.

  The acetal group-containing guanamines are not particularly limited, and examples thereof include 2,4-diamino-6- (3,3-dimethoxypropyl-s-triazine. Examples of the dioxane ring-containing guanamine include [2- (4′-6′-diamino-s-triazin-2′-yl) ethyl] -1,3-dioxane, and [2- (4′-6′-diamino-s-triazin-2′-yl) ethyl -4-ethyl-4-hydroxymethyl-1,3-dioxane, and examples of the tetraoxospiro ring-containing guanamines include CTU-guanamine and CMTU-guanamine, and examples of the isocyanuric ring-containing guanamines Is, for example, 1,3,5-tris [2- (4 ′, 6′-diamino-s-triazin-2′-yl) ethyl] isocyanurate And 1,3,5-tris [3- (4 ', 6'-diamino-s-triazin-2'-yl) ethyl] isocyanurate.

  The urea compound is not particularly limited, and examples thereof include a chain urea compound and a cyclic urea compound.

  Specific examples of the chain urea-based compound include condensates of urea and formaldehyde such as biurea, biuret, and form nitrogen, and polyalkylene or arylene urea such as polynanomethylene urea.

  Specific examples of the cyclic urea compounds include hydantoins, chlorotylidene diurea, acetylene urea, mono, di, tri or tetraalkoxymethyl glycoluril such as mono, di, tri or tetramethoxymethylene glycoluril, cyanuric acid, isocyanuric acid , Urea, and urazole.

  Examples of hydantoins include hydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-isopropylhydantoin, 5-phenylhydantoin, 5-benzylhydantoin, 5,5-dimethylhydantoin, 5,5-pentamethylenehydantoin, 5 Allanin Al salts such as methyl-5-phenylhydantoin, 5,5-diphenylhydantoin, 5- (o-, m- or p-aminophenyl) hydantoin, allantoin, 5-methylallantoin, and allantoin dihydroxyaluminum salt, etc. The metal salt is mentioned.

  Examples of the carboxylic acid hydrazide compound include an aliphatic carboxylic acid hydrazide compound, an alicyclic carboxylic acid hydrazide compound, and an aromatic carboxylic acid hydrazide compound.

  Specific examples of the aliphatic carboxylic acid hydrazide compounds include monocarboxylic acid hydrazides such as lauric acid hydrazide, stearic acid hydrazide, 12-hydroxystearic acid hydrazide, 1,2,3,4-butanetetracarboxylic acid hydrazide; Acid mono or dihydrazide, glutaric acid mono or dihydrazide, adipic acid mono or dihydrazide, pimelic acid mono or dihydrazide, suberic acid mono or dihydrazide, azelaic acid mono or dihydrazide, sebacic acid mono or dihydrazide, dodecanedioic acid mono or dihydrazide, hexadecanedi Examples thereof include polycarboxylic acid hydrazides such as acid mono- or dihydrazide, eicosane diacid mono- or dihydrazide, and 7,11-octadecadien-1,18-dicarbohydrazide.

  Specific examples of the alicyclic carboxylic acid hydrazide compounds include monocarboxylic acid hydrazides such as cyclohexanecarboxylic acid hydrazide; dimer acid mono or dihydrazide, trimer acid mono, di or trihydrazide, 1,2-, 1,3- Alternatively, carboxylic acid hydrazides such as 1,4-cyclohexanedicarboxylic acid mono- or dihydrazide, cyclohexanetricarboxylic acid mono-, di- or trihydrazide may be mentioned.

  Specific examples of the aromatic carboxylic acid hydrazide compound include monocarboxylic acid hydrazides such as benzoic acid hydrazide and functional group-substituted derivatives thereof, α- or β-naphthoic acid hydrazide and functional group-substituted derivatives thereof; Dihydrazide, 1,4- or 2,6-naphthalenedicarboxylic acid mono or dihydrazide, 3,3-, 3,4- or 4,4-diphenylcarboxylic acid mono or dihydrazide, diphenyl ether dicarboxylic acid mono or dihydrazide, diphenylmethane dicarboxylic acid mono Or dihydrazide, diphenylethane dicarboxylic acid mono or dihydrazide, diphenoxyethane dicarboxylic acid mono or dihydrazide, diphenyl sulfone dicarboxylic acid mono or dihydrazide, diphenyl ketone dicarboxylic acid mono or dihydrazide, 4, 4 ″ -terphenyl dicarboxylic acid mono or dihydrazide, 4,4 ′ ″-quarterphenyl dicarboxylic acid mono or dihydrazide, 1,2,4-benzenetricarboxylic acid mono, di or trihydrazide, pyromellitic acid mono, di, Examples thereof include polycarboxylic acid hydrazides such as tri- or tetrahydrazide, 1,4,5,8-naphthoic acid mono-, di-, tri- or tetrahydrazide.

  Examples of benzoic hydrazide and functional group-substituted derivatives thereof include o-, m- or p-methylbenzoic hydrazide, 2,4-, 3,4-, 3,5- or 2,5-dimethylbenzoic hydrazide. O-, m- or p-hydroxybenzoic acid hydrazide, o-, m- or p-acetoxybenzoic acid hydrazide, 4-hydroxy-3-phenylbenzoic acid hydrazide, 4-acetoxy-3-phenylbenzoic acid hydrazide, 4 -Alkyl such as phenyl benzoic acid hydrazide, 4- (4'-phenyl) benzoic acid hydrazide, 4-hydroxy-3,5-dimethylbenzoic acid hydrazide, 4-hydroxy-3,5-di-t-butylbenzoic acid hydrazide Group, hydroxy group, acetoxy group, amino group, acetamino group, nitrile group, carboxy group, alkoxycarbonyl group, Rubamoiru group, an alkoxy group, a phenyl group, a benzyl group, cumyl group, a functional group such as a hydroxyphenyl group is 1-5 substituted derivatives phenyl residues benzoguanamine.

  Examples of α- or β-naphthoic acid hydrazide and functional group-substituted derivatives thereof include 3-hydroxy-2-naphthoic acid hydrazide and 6-hydroxy-2-naphthoic acid hydrazide.

  In addition, the above formaldehyde inhibitor is supported in a layered material or a porous material (hydrotalcite, montmorillonite, silica gel, alumina, titania, zirconia, sepiolite, smectite, palygorskite, imogolite, zeolite, activated carbon, etc.). Use is also possible.

  Among the above formaldehyde inhibitors, aminotriazine compounds, guanamine compounds, particularly aromatic guanamine compounds; urea compounds, particularly cyclic urea compounds; carboxylic acid hydrazide compounds, particularly aliphatic carboxylic acid hydrazide compounds, and aromatic carboxylic acids. Acid hydrazide compounds are preferably used. Among these, aliphatic carboxylic acid hydrazide compounds and aromatic carboxylic acid hydrazide compounds are more preferable. Among aliphatic carboxylic acid hydrazide compounds and aromatic carboxylic acid hydrazide compounds, dihydrazides such as adipic acid dihydrazide, sebacic acid dihydrazide, dodecadioic acid dihydrazide, isophthalic acid dihydrazide, and terephthalic acid dihydrazide suppress formaldehyde generation. It is preferable in terms of effects.

  In the polyacetal resin in this embodiment, the content of the formaldehyde inhibitor is preferably 0.005 parts by mass or more and 5.0 parts by mass or less, more preferably 0.01 parts by mass with respect to 100 parts by mass of the polyacetal resin. The amount is 3.0 parts by mass or less, and more preferably 0.02 parts by mass or more and 2.0 parts by mass or less.

<Polyalkylene glycol>
It is preferable that the polyacetal resin composition of this embodiment further contains polyalkylene glycol. The content is preferably 0.3 parts by weight or more and 3.0 parts by weight or less, and 0.5 parts by weight or more and 2.0 parts by weight or less with respect to 100 parts by weight of the polyacetal resin. Is more preferably 0.7 parts by mass or more and 1.5 parts by mass or less. By setting it as such a range, it exists in the tendency which can improve production stability and can improve toughness more.

In the present embodiment, the polyalkylene glycol may be a copolymer or two or more types of polyalkylene glycols. The polyalkylene glycol of the present embodiment is preferably polyethylene glycol in terms of economy and handling. The polyethylene glycol is more preferably a polyethylene glycol having a number average molecular weight of 800 to 500,000, more preferably a polyethylene glycol having a number average molecular weight of 1,000 to 20,000, and a polyethylene having a number average molecular weight of 2,000 to 10,000. More preferably, it is glycol. By setting it within this range, the toughness and brightness tend to be further improved. In this embodiment, the number average molecular weight of polyethylene glycol is measured using, for example, a magnetic resonance spectrometer, and specifically measured as follows. First, polyethylene glycol to be measured is dissolved in a solvent: HFIP-d ₂ (D conversion rate 97%, Wako Pure Chemicals 98% assay) over 24 hours to prepare a 1.5% by mass resin solution. Next, for the resin solution, using an apparatus: JEOL-400 nuclear magnetic resonance spectrometer ( ¹ H: 400 MHz), temperature: 55 ° C., integration number: 500 times, integration of oxyethylene component and hydroxyl group attribution peaks The number average molecular weight is determined from the amount of the oxyethylene component relative to the terminal hydroxyl group.

<Hydrazide compound>
The polyacetal resin composition of the present embodiment preferably further contains a hydrazide compound in order to further improve production stability. As content of a hydrazide compound, it is more preferable that it is 0.03 mass part or more and 0.25 mass part or less with respect to 100 mass parts of polyacetal resin, and it is 0.05 mass part or more and 0.20 mass part or less. More preferably, it is 0.07 mass part or more and 0.15 mass part or less. The hydrazide compound may be added during the granulation of the polyacetal resin, added during the production of the polyacetal composition, or both.

Although it does not specifically limit as a hydrazide compound used by this embodiment, Dicarboxylic acid dihydrazide represented by following General formula (6) is preferable, Malonic acid dihydrazide, Succinic acid dihydrazide, Glutaric acid dihydrazide, Adipic acid dihydrazide, Pimelic acid Dihydrazide, speric acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, and phthalic acid dihydrazide are preferred.
^{_{H 2 NHNOC-R 1 -CONHNH 2}} ··· (6)
In formula (6), R < ¹ > shows a C2-C20 hydrocarbon.

  Among the dicarboxylic acid dihydrazides, preferred are sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, and adipic acid dihydrazide, and more preferred are sebacic acid dihydrazide and adipic acid dihydrazide. In this embodiment, the hydrazide compound may be contained individually by 1 type, and may be contained in combination of 2 or more types.

<Colorant>
The polyacetal resin composition of the present embodiment can further contain a colorant in order to enhance design properties. Although it does not specifically limit as a coloring agent, For example, an organic pigment and an inorganic pigment are mentioned. Further, the colorant may be a single type or a combination of two or more types. The organic pigment is not particularly limited, and examples thereof include phthalocyanine pigments, condensed azo pigments, azo lake pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments, and condensed polycyclic pigments. Examples of inorganic pigments include, but are not limited to, simple oxides such as zinc white, titanium dioxide, petal, chromium oxide, and iron black; sulfides such as cadmium yellow, cadmium orange, and cadmium red; yellow lead, zinc yellow And chromate such as chromium vermilion, ferrocyanide such as bitumen; silicate such as ultramarine; inorganic colorants such as carbon black and metal powder. Although content of a coloring agent is not specifically limited, It is preferable that it is 10 mass parts or less with respect to 100 mass parts of polyacetal resins. By setting it within this range, the appearance of the molded body can be further improved and the strength tends to be maintained.

<Other additives>
The polyacetal resin composition of this embodiment can further contain additives other than those described above (other additives). Examples of other additives include heat stabilizers used in conventional polyacetal resins. Examples of heat stabilizers include antioxidants, formaldehyde and formic acid scavengers, and combinations thereof.

  Although it does not specifically limit as antioxidant, A hindered phenolic antioxidant is preferable, As a hindered phenolic antioxidant, n-octadecyl-3- (3'5'-di-t-butyl) is mentioned, for example. -4'-hydroxyphenyl) -propionate, n-octadecyl-3- (3'-methyl-5'-t-butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3'5'- Di-t-butyl-4′-hydroxyphenyl) -propionate, 1,6-hexanediol-bis- (3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate), 1,4 -Butanediol-bis- (3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate), triethylene glycol-bis- A propionate) - 3- (3-t- butyl-5-methyl-4-hydroxyphenyl). Tetrakis- (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate methane, 3,9-bis (2- (3- (3-t-butyl) -4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl) 2,4,8,10-tetraoxaspiro (5,5) undecane, N, N'-bis-3- (3 '5'-di-t-butyl-4-hydroxyphenol) priionyl hexamethylenediamine, N, N'-tetramethylenebis-3- (3'-methyl-5'-t-butyl-4-hydroxyphenol) ) Propionyldiamine, N, N′-bis- (3- (3,5-di-t-butyl-4-hydroxyphenol) propionyl) hydrazine, N-salicyloyl-N′-salicylidenehydrazine, 3- ( -Salicyloyl) amino-1,2,4-triazole and N, N'-bis (2- (3- (3,5-di-butyl-4-hydroxyphenyl) propionyloxy) ethyl) oxyamide It is done.

  Among the hindered phenol antioxidants, triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate) and tetrakis- (methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate methane is preferred.

  The scavenger for formaldehyde and formic acid is not particularly limited. For example, (b) compounds and polymers containing formaldehyde-reactive nitrogen, (b) alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carvone Examples include acid salts and alkoxides.

  (I) The compound containing formaldehyde-reactive nitrogen is not particularly limited, and examples thereof include (1) dicyandiamide, (2) amino-substituted triazine, and (3) a co-condensate of amino-substituted triazine and formaldehyde.

  (2) The amino-substituted triazine is not particularly limited. For example, guanamine (2,4-diamino-sym-triazine), melamine (2,4,6-triamino-sym-triazine), N-butylmelamine, N -Phenyl melamine, N, N-diphenyl melamine, N, N-diallyl melamine, N, N ', N' '-triphenyl melamine, N-methylol melamine, N, N'-dimethylol melamine, N, N', N ''-trimethylol melamine and benzoguanamine (2,4-diamino-6-phenyl-sym-triazine). 2,4-diamino-6-methyl-sym-triazine, 2,4-diamino-6-butyl-sym-triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino -6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl-sym-triazine, 2,4-diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine 2,4-dioxy-6-amino-sym-triazine (Amelite), 2-oxy-4,6-diamino-sym-triazine (Ameline), and N, N ′, N′-tetracyanoethylbenzoguanamine. .

  (3) Although it does not specifically limit as a cocondensate of an amino substituted triazine and formaldehyde, For example, a melamine-formaldehyde polycondensate is mentioned. Among these, dicyandiamide, melamine, and melamine-formaldehyde polycondensate are preferable.

  (A) The polymer having a formaldehyde-reactive nitrogen group is not particularly limited. For example, (1) polyamide resin, (2) acrylamide and derivatives thereof, or acrylamide and derivatives thereof, and other vinyl monomers are metals. A polymer obtained by polymerization in the presence of an alcoholate, (3) a polymer obtained by polymerizing acrylamide and its derivatives, or acrylamide and its derivatives, and other vinyl monomers in the presence of radical polymerization, and ( 4) Polymers containing nitrogen groups such as amines, amides, ureas, urethanes, and the like.

  Although it does not specifically limit as a polyamide resin of (1), For example, nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, and these copolymers are mentioned. More specifically, nylon 6 / 6-6, nylon 6 / 6-6 / 6-10, and nylon 6 / 6-12 can be mentioned.

  Examples of the polymer obtained by polymerizing acrylamide and derivatives thereof (2) or acrylamide and derivatives thereof with other vinyl monomers in the presence of a metal alcoholate include, for example, poly-β-alanine copolymers. It is done. These polymers and copolymers are described in JP-B-6-12259 (corresponding to US Pat. No. 5,015,707), JP-B-5-87096, JP-B-5-47568, and JP-A-3-234729. It can manufacture by the method of each gazette of gazette.

  In addition, when the polyacetal resin composition of the present embodiment is a molded product used for design parts such as automobile interiors and exterior parts, benzotriazole-based and oxalic anilides used in conventional polyacetal resins It is preferable to further contain a UV absorber selected from the system UV absorbers. An ultraviolet absorber may be used individually by 1 type, and may use 2 or more types together.

  Although it does not specifically limit as a benzotriazole type ultraviolet absorber, For example, 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-). t-butyl-phenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-isoamyl-phenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis- (α , Α-dimethylbenzyl) phenyl] benzotriazole, and 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole.

  Although it does not specifically limit as an oxalic acid anilide type | system | group ultraviolet absorber, For example, 2-ethoxy-2'-ethyl oxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyl oxalitz Examples thereof include quartz bisanilide and 2-ethoxy-3′-dodecyloxalizic acid bisanilide.

  The polyacetal resin composition of the present embodiment includes, as desired, lubricants, various inorganic fillers, other thermoplastic resins, softeners, crystal nuclei conventionally used in polyacetal resins, as long as the object of the present invention is not impaired. An agent, a release agent and the like can be further included.

[Production Method of Polyacetal Resin Composition]
The manufacturing method of the polyacetal resin composition of this embodiment has the process of mix | blending polyacetal resin and a luster material. The blended polyacetal resin composition has a spherical or cylindrical shape called a pellet and is manufactured from the manufacturer to be processed into a granulated product (solid material) having a length of about 1 to several mm in diameter. From the viewpoint of distribution to a person. This granulated product can be produced, for example, by using a melt kneader used for processing plastic materials.

  In order to improve the uniform dispersibility of the glittering material in the polyacetal resin, the powder obtained by pulverizing a part or all of the polyacetal resin / pellets and the glittering material may be mixed in advance and then melt mixed. Moreover, when using a polyacetal resin and a pellet, you may improve the dispersibility of a glittering material using an additive. Examples of the additive include aliphatic hydrocarbons, aromatic hydrocarbons, modified products thereof, and mixtures thereof (liquid paraffin, mineral oil, etc.), and in addition, fatty acid esters of polyols.

  The production of the polyacetal resin composition of this embodiment can also be carried out by melt-kneading (pre-kneading) a polyacetal resin, a bright material, and other additives in advance. For this pre-kneading, a generally used melt-kneader can be used. Although it does not specifically limit as a melt-kneader, For example, a kneader, a roll mill, a single screw extruder, a twin screw extruder, and a multi-screw extruder are mentioned. The processing temperature at the time of pre-kneading is not particularly limited, but is preferably 180 to 230 ° C, more preferably 190 to 210 ° C.

  In order to maintain the quality and working environment, and to suppress the occurrence of dust explosion, pellets of polyacetal resin, glittering material, and other additives alone, or a container for mixing these, Replace the container to be stored, the flow path between the container and the extruder, the hopper of the extruder, etc. with an inert gas upstream from the point where the mixture melts, and / or remove with a single-stage or multistage vent. It is preferable to care.

Furthermore, when the polyacetal resin composition of the present embodiment is produced, it is preferable that the glittering material is sufficiently dried in advance before the polyacetal resin and the glittering material are mixed. The term “drying” as used herein means that a bright material having a mass W ₁ (g) before mixing is dried in an oven at 80 ° C. for 2 hours, and the mass W ₂ (g) after the drying is expressed by a relational expression [(W ₁ −W ₂ ) / W ₂ ] is adjusted to 0.0015 or less, preferably 0.001 or less. Thereby, it exists in the tendency which can maintain stability and productivity at the time of production of a polyacetal resin composition highly.

[Production Method of Polyacetal Resin Molded Product]
The manufacturing method of the polyacetal resin molding of this embodiment has the process of shape | molding the polyacetal resin composition of this embodiment. The molding method is not particularly limited. For example, in addition to a general injection molding method used for molding a thermoplastic resin into a desired shape, extrusion molding, foam molding, injection compression molding, two-color molding, insert Examples thereof include molding, outsert molding, blow molding, and gas assist molding using nitrogen gas or carbon dioxide gas. These molding methods may be used singly or in combination of two or more.

  The method of making the image definition of a part or the whole of the polyacetal resin molded product 20% or more, that is, the method for producing the polyacetal resin molded product of the present embodiment is as long as the polyacetal resin composition of the present embodiment is molded. Although not particularly limited, it is preferable to have a step of injection molding the polyacetal resin composition of the present embodiment. The step of injection molding is a step of injection molding a resin using a mold that is more preferably 100 ° C. or higher, and still more preferably 110 ° C. or higher. Specifically, it can be obtained by filling a mold cavity with a molten polyacetal resin composition. Here, when the temperature of the mold cavity is set to 100 ° C. or more, the amorphous part of the molded product tends to be thinned, and not only the image sharpness is improved, but also scratch resistance and chemical resistance are improved. Tend to.

  Also, a molding method having a process of heating and cooling a mold in a molding cycle, for example, when filling a mold with molten polyacetal resin, keep the mold temperature at 100 ° C. or higher and filling the resin Using heat and cool molding that lowers the mold temperature to about 80 ° C. upon completion or at an arbitrary timing is also an effective means for increasing the image clarity of a part or the whole of the polyacetal resin molded product to 20% or more. is there.

  The above "gas assist molding method" is a generally known injection molding method using nitrogen gas or carbon dioxide gas. More specifically, as described in Japanese Patent Publication No. 57-14968, etc., After injecting the resin composition into the mold cavity, a method of injecting pressurized gas into the molded product, as described in Japanese Patent No. 3819972, etc., after injecting the resin composition into the mold cavity, molding There are a method of injecting a pressurized gas into a cavity corresponding to one side of a product, and a method of filling a thermoplastic resin with a gas in advance as described in Japanese Patent No. 3349070. These gas assist molding methods are appropriately selected depending on the molded product and the product shape. In particular, from the viewpoint of quality, production stability, economy, etc., injection molding / injection compression molding and a molding method in which these are combined with in-mold composite molding are preferable.

  Furthermore, the manufacturing method of the molded product includes adhesion between the polyacetal resin composition of the present embodiment and various resins including rubber and elastomer (ultrasonic bonding, high frequency bonding, hot plate bonding, hot press molding, multilayer injection molding, multilayer injection molding). Blow molding and other methods do not matter) By providing a molded product with two or more layers, it gives excellent performance (impact resistance, slidability, chemical resistance, etc.) of various resins, and is excellent It is possible to obtain a molded body having an appearance having a good design property.

[Use]
The polyacetal resin molded product of the present embodiment can be used for a design part having a mechanism part and a sliding part. Specifically, the molded product is, for example, any one of parts used for OA equipment, music, video or information equipment, communication equipment, industrial parts used for office furniture or housing equipment, and parts used for automobile interior and exterior. These parts are preferable. The molded article is also suitable for use in automobile interior parts, such as inner handles, shift knobs, steering and wheels, levers, switches, buttons and other functional parts, and decorative parts.

  Furthermore, depending on the appearance part, there may be a case where a design property is imparted by using a mold having a texture in part or in whole at the time of molding. The polyacetal resin molded product according to the present embodiment is more preferable because it is excellent in the transferability of the texture and can maintain high lightness, so that the effect is remarkably exhibited.

  Hereinafter, the present embodiment will be specifically described by way of examples and comparative examples, but the present embodiment is not limited to these examples and comparative examples unless they exceed the gist of the present embodiment.

(1) Main raw materials [Prepared polyacetal copolymers A1 to A5: Components A1 to A5]
Each polyacetal copolymer used in Examples and Comparative Examples, and each prepared polyacetal copolymer A1 to A5 containing additives and the like (hereinafter referred to as “component A1”, “component A2”, “component A3”, “ Component A4 "and" Component A5 ") were prepared as follows. In addition, component A1-A5 is also named the component A collectively with the component A11 mentioned later.

Self-cleaning type twin screw paddle type continuous mixing reactor with a jacket that allows heat medium to pass through (screw diameter 3 inches, ratio of screw length L to screw diameter D (L / D) = 10) to 80 ° C. Adjusted, 2625 g / hr of trioxane as the main monomer, 12 g / hr of 1,3-dioxolane as the comonomer, methylal as the chain transfer agent (both impurities reduced), a static mixer (manufactured by Noritake Company Limited, T-type element number 21) is continuously fed to the reactor, and a 1% by mass cyclohexane solution of boron trifluoride di-n-butyl etherate is used as the polymerization catalyst. Polymerization was performed by adding to 0 × 10 ⁻⁵ mol to obtain polymerization flakes. Here the chain transfer agent was adjusted from 2 to 5 g / hr depending on the MFR of the desired prepared polyacetal copolymer.

Each of the obtained polymer flakes was finely pulverized and then poured into a 1% aqueous solution of triethylamine and stirred to deactivate the polymerization catalyst, followed by filtration, washing and drying to obtain a crude polymer. The obtained crude polymer is triethyl (2-hydroxyethyl) ammonium formate as a quaternary ammonium compound with respect to 1 part by mass of the crude polymer, converted to the amount of nitrogen using the following formula (A), and 20 mass ppm. And mixed uniformly and then dried at 120 ° C. for 3 hours to obtain a dry polymer.
P × 14 / Q (A)
(In formula (A), P represents the concentration (mass ppm) of the quaternary ammonium compound relative to the crude polymer, “14” represents the atomic weight of nitrogen, and Q represents the molecular weight of the quaternary ammonium compound. .)

  As shown in FIG. 1, this dry polymer is introduced from the top feeder into the front stage of a screw type twin screw extruder with a vent (plastic industry; BT-30, L / D = 44, set temperature 200 ° C., rotation speed 80 rpm). Then, 0.5% by mass of water was added to the dried polymer, the polymer terminal was stabilized with an average residence time of 1 minute, and vacuum degassing was performed. Next, 0.05 parts by mass of polyamide 66 as a heat stabilizer, 0.1 parts by mass of calcium stearate, 2- [2′-hydroxy-3 ′, Granulation was carried out after adding 0.5 parts by mass of 5′-bis- (α, α-dimethylbenzyl) phenyl] benzotriazole and further adding the additives shown in Table 1 and melt-mixing with an average residence time of 1 minute. . This was dried at 80 ° C. for 3 hours to obtain intermediate pellets composed of the prepared polyacetal copolymer (components A1 to A5). From the raw material input to the intermediate pellet collection, the operation was performed while avoiding oxygen contamination as much as possible. The obtained prepared polyacetal copolymer was measured for MFR (melt flow rate; g / 10 min) under ISO 1133 condition D (load 2.16 kg, cylinder temperature 190 ° C.). The results are shown in Table 1.

Further, the prepared polyacetal copolymers A1 to A5 shown in Table 1 were dissolved in a solvent: HFIP-d ₂ (D conversion rate 97%, Wako Pure Chemicals 98% assay) over 24 hours to obtain a 1.5% by mass resin solution. Was prepared. For the resin solution, using an apparatus: JEOL-400 nuclear magnetic resonance spectrometer ( ¹ H: 400 MHz), temperature: 55 ° C., integration number: 500 times, integration of assigned peaks of oxymethylene component and oxyethylene component And the copolymerization amount of the comonomer component was determined. When the oxymethylene component was converted to trioxane (formaldehyde trimer), the comonomer component was 3.5 to 4.5 mol with respect to 100 mol of trioxane.

[Prepared polyacetal homopolymer A11: Component A11]
The polyacetal homopolymer used in Examples and Comparative Examples, and the prepared polyacetal homopolymer A11 containing these additives and the like were prepared as follows.

  A polymerization apparatus 100 shown in FIG. 3 was prepared. In the polymerization apparatus 100, slurry circulation lines 3 a and 3 b were provided in a 5 L tank type polymerizer 2 with a jacket through which a heating medium attached with a stirrer driven by a stirring motor 1 with a stirring blade 4 can pass. This was filled with 2 L of n-hexane. The total size of the slurry circulation line was 3φ and 3b to 6φ × 2.5 m, and n-hexane was circulated by the slurry circulation pump 9 at 20 L / hr. Into this, 200 g / hr of dehydrated formaldehyde gas was directly supplied from the supply line 5. Dimethyl distearyl ammonium acetate was used as a polymerization catalyst, and the polymerization catalyst was supplied via a supply line 7 to a circulation line immediately before the reactor. In addition, a chain transfer agent (acetic anhydride) for supplementing the slurry extracted from the system through the line 8 is added from the supply line 6 to the circulation line 3a, and polymerization is performed at 58 ° C. while continuously supplying. A polymerization slurry containing the polymer was obtained. The polymerization catalyst and chain transfer agent to be added were adjusted according to the MFR of the target prepared polyacetal homopolymer.

  Stabilization was performed by reacting the resulting slurry in a 1: 1 (volume ratio) mixture of hexane and acetic anhydride at 140 ° C. for 2 hours and acetylating the molecular ends. The polymer after the reaction was collected by filtration, dried under a reduced pressure drier set at 80 ° C. under a reduced pressure of 2 mmHg or less for 3 hours to obtain a polyacetal homopolymer powder. Thereafter, 0.05 parts by mass of polyamide 66 and 0.5 parts by mass of 2- [2′-hydroxy-3 ′, 5′-bis- (α, α-dimethylbenzyl) phenyl] benzotriazole were added as heat stabilizers. Further, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate (Sanol LS-770 / X = H) was added in the amount shown in Table 1, and melt mixed with an average residence time of 1 minute. After that, granulation was performed. This was dried at 80 ° C. for 3 hours to obtain an intermediate pellet composed of the prepared polyacetal homopolymer (component A11). From the raw material input to the intermediate pellet collection, the operation was performed while avoiding oxygen contamination as much as possible.

  The obtained adjusted polyacetal homopolymer was measured for MFR (melt flow rate; g / 10 min) under ISO 1133 condition D (load 2.16 kg, cylinder temperature 190 ° C.). The results are shown in Table 1.

[Aluminum pigment / component B]
The aluminum pigments used in the examples and comparative examples (hereinafter also referred to as “component B1,” “component B2,” and “component B3”) are aluminum paste “Sylbeads” manufactured by Asahi Kasei Metals Corporation. The product name, shape, and particle size are shown in Table 2. The particle size in Table 2 is an average particle size, and the particle size distribution shows one peak. Components B1 to B3 are also collectively referred to as components.

(2) Polyacetal resin composition The intermediate pellet composed of the above component A and component B are blended as shown in Tables 3 and 4, and melt-mixed under a nitrogen purge, granulated, and dried at 80 ° C for 3 hours. A resin composition (final pellet) was obtained. As shown in FIG. 2, a screw type twin screw extruder (plastic industry; BT-30, L / D = 44, set temperature 200 ° C., rotation speed 100 rpm) was used for melt mixing. The feed of the raw material was 12.5 kg / hr. Unless otherwise specified, adipic acid dihydrazide, which is a hydrazide compound, was added as Component C from a 0.1 part by mass side feeder with respect to 100 parts by mass of the polyacetal resin component.

(3) Sample [Sample flat plate]
In order to measure the image definition, chemical resistance, pencil hardness, Fr value, and G value using the final pellet, a molding machine (Toshiba Machine; IS-100E, cylinder temperature 200 ° C., mold temperature 80 to A flat plate having a width of 50 mm, a length of 90 mm, and a thickness of 2.5 mm was formed using 110 ° C. and a cooling time of 20 seconds. The molded product was confirmed to be free of short shots and burrs, and used as a test piece. The mold temperature was adjusted as shown in Tables 3 and 4.

(4) Characteristics [image definition]
The amount of light reflected from the test piece by an incident angle of 60 ° was measured through an optical comb according to “Plastics—Determination of image definition” defined in Japanese Industrial Standard (JIS K 7374). The optical comb perpendicular to the beam axis of the reflected light from the test piece is moved, and the amount of light (M) when the comb is on the optical axis and the amount of light (m) when the comb is shielded. It calculated | required from the following formula as a ratio (%) of both difference (M-m) and sum (M + m). In the measurement, “image clarity measuring device“ ICM-1T ”” manufactured by Suga Test Instruments Co., Ltd. was used to measure the amount of light reflected on the molded product when the width of the optical comb was 1.0 mm.
Image sharpness (%) = (M−m) ÷ (M + m) × 100

[chemical resistance]
3 mL of 35% hydrochloric acid was dropped with a dropper on the upper surface of a test piece (flat plate product) placed horizontally in a draft and left standing. After 1 hour, the hydrochloric acid on the flat plate was washed away with running water, and after drying, the maximum depth of corrosion marks (maximum height: Rmax value) by hydrochloric acid was measured with a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., “ Surfcom 575A ").

[Pencil hardness]
According to the JIS-K5400 standard, the pencil hardness of the surface of the test piece (molded product) was measured.

[Fr value and G value]
The Fr value and the G value were measured using “Spectrophotometer“ BYK-mac ”” manufactured by BYK-Gardner GmbH. Here, the Fr value is an index of a feeling of brightness, and is indicated by the “Fr value (flop value)” measured by the “BYK-mac”, and is a flop index, Flop Index (FI). This value is also referred to as a value calculated from values obtained by measuring the lightness (L *) of light reflected at angles of 15 °, 45 °, and 110 ° with the regular reflection angle of incident light as a reference line. It is. The G value is an index of graininess, and is a value indicated by a “G (Graininess) value” measured by the “BYK-mac”.

(5) Results [Examples 1-8, Comparative Examples 1-5]
Table 3 shows the composition, mold temperature, and characteristics of component A (prepared polyacetal) and component B (aluminum pigment) in the polyacetal resin compositions of Examples 1 to 8 and Comparative Examples 1 to 5.

  Molded products with an image clarity exceeding 20% tend to have a depth of at least 35% hydrochloric acid with a shallow depth of corrosion and a high pencil hardness. By making the molded product with an image clarity exceeding 20%, It can be seen that the balance of surface appearance characteristics, chemical resistance, and hardness is excellent.

[Examples 9 to 13, Comparative Examples 6 to 10]
Polyacetal resins used are homopolymers and copolymers, and polyacetal resins are fluid regardless of shape, and molded products with image clarity exceeding 20% have a shallow depth of corrosion traces due to 35% hydrochloric acid. It turns out that it is excellent in the balance of surface appearance characteristics, chemical resistance, and hardness by making a molded product having a tendency of high hardness and an image clarity exceeding 20%.

  The polyacetal resin molded product according to the present invention is environmentally friendly, retains the mechanical properties inherent to the resin, and can stably obtain a molded product having an excellent appearance. Is preferred.

  DESCRIPTION OF SYMBOLS 1 ... Motor for stirring with a stirring blade, 2 ... Polymerizer with jacket, 3a, 3b ... Slurry circulation line, 4 ... Stirring blade, 5 ... Supply line for formaldehyde gas, 6 ... Supply line for chain transfer agent, 7 ... Polymerization catalyst Supply line, 8 ... slurry collection line, 9 ... slurry circulation pump, 100 ... polymerization apparatus.

Claims (9)

A molded product comprising a polyacetal resin and a bright material of 0.2 to 10 parts by mass with respect to 100 parts by mass of the polyacetal resin,
The glitter material is a mixture of a metal pigment having a large particle size and a metal pigment having a small particle size,
The difference between the peak particle size in the particle size distribution of the large-sized metal pigment and the peak particle size in the particle size distribution of the small-sized metal pigment exceeds 5.0 μm,
The mass ratio of the small particle size metal pigment to the large particle size metal pigment is high,
A polyacetal resin molded product, wherein an image definition of at least a part of the molded product is 20% or more.   The polyacetal resin molded article according to claim 1, wherein the polyacetal resin is a polyacetal copolymer. The luster material is a metal pigment,
The polyacetal resin molded product according to claim 1 or 2, wherein the shape of the metal pigment is a coin shape or flake shape, and the average particle diameter of the metal pigment is in the range of 3.0 µm to 80 µm. The polyacetal resin molded product according to any one of claims 1 to 3 , wherein the metal pigment is an aluminum pigment. The polyacetal resin molded product according to any one of claims 1 to 4 , wherein the image definition is 30% or more. The polyacetal resin molded product according to any one of claims 1 to 5 , wherein the pencil hardness in JIS-K5400 is H or more. The polyacetal resin molded product according to any one of claims 1 to 6 , wherein the maximum depth of corrosion marks after contact with 35% by mass hydrochloric acid for 1 hour is 150 µm or less. The polyacetal resin molded product is any one of OA equipment, music, video or information equipment, parts used for communication equipment, industrial parts used for office furniture or residential equipment, and parts used for automobile interior and exterior The polyacetal resin molded product according to any one of claims 1 to 7 , wherein A method for producing a polyacetal resin molded product, comprising a step of obtaining a polyacetal resin molded product according to any one of claims 1 to 8 by injection molding a resin using a mold having a mold temperature of 100 ° C or higher. .

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