JP7037960B2 - Polyacetal resin composition - Google Patents

Description

The present invention relates to a polyacetal resin composition having excellent processability and stability, significantly suppressing the amount of formaldehyde generated from the molded product, and stably suppressing the mold deposit during production.

Polyacetal resin has excellent properties, and its molded product is used in a wide range of fields. However, due to its chemical structural characteristics, it is easily decomposed under a heated oxidizing atmosphere or under acidic or alkaline conditions. Has. Therefore, the problem of the polyacetal resin is that it has high thermal stability and suppresses the generation of formaldehyde in the molding process or the molded product. If the thermal stability is low, the polymer is decomposed by heating in a processing process such as extrusion or molding, and deposits on the mold (mold deposit) are generated, and the moldability and mechanical properties are deteriorated.

In addition, although the amount of formaldehyde generated from the polyacetal resin molded product under normal use conditions is extremely small, the generated formaldehyde is chemically active and becomes formic acid due to oxidation, which adversely affects the heat resistance of the polyacetal resin. Or, when used for parts of electrical and electronic equipment, formaldehyde or formic acid, which is an oxide thereof, may corrode metal contact parts, and adhesion of organic compounds may cause discoloration or contact failure.

Therefore, in order to stabilize the polyacetal resin, an antioxidant and other stabilizers are added. As antioxidants added to polyacetal resins, phenol compounds having steric disorders (hindered phenols), amine compounds having steric disorders (hindered amines) and the like are known, and other stabilizers include melamine and polyamide. Alkaline metal hydroxides and alkaline earth metal hydroxides are used. Also, antioxidants are usually used in combination with other stabilizers.

However, it is difficult to significantly reduce the formaldehyde generated, particularly the formaldehyde generated from the molded product, only by blending such a general-purpose stabilizer with a polyacetal resin having a normal formaldehyde quality. Further, in order to solve the above-mentioned problems and reduce the amount of formaldehyde generated, a polyacetal resin composition containing various compounds has been disclosed.

For example, a technique for using a polyacetal resin having a specific terminal group, a hindered phenolic antioxidant, and a hydrazide in combination is disclosed (Patent Documents 1 and 2). Further, a technique for coexisting a graft copolymer, a fatty acid ester, a silicone oil, and calcium carbonate having a specific size is also disclosed (Patent Document 3).

Japanese Unexamined Patent Publication No. 2008-1564889 Japanese Unexamined Patent Publication No. 2009-286874 Japanese Unexamined Patent Publication No. 2016-176010

According to the techniques disclosed in Documents 1 and 2, it is possible to reduce the generation of formaldehyde from the polyacetal resin to a considerable level. However, although it is effective in significantly reducing the generation of formaldehyde, the actual situation is that the mold deposit cannot be sufficiently suppressed.
Further, according to the technique disclosed in Document 3, although the effect is exhibited, the expression of the effect varies, and it cannot be said that the technique is stable.

An object of the present invention is to provide a polyacetal resin composition capable of suppressing the generation of formaldehyde from a molded product to an extremely low level and stably suppressing the mold deposit during production.

The object of the present invention was achieved by the following.

1. 1. (A) With respect to 100 parts by mass of the polyacetal polymer
(B) Hindered phenolic antioxidant 0.01 to 3 parts by mass,
(C) 0.01 to 1 part by mass of the hydrazide compound,
(D) Fatty acid Calcium salt 0.01 to 0.5 parts by mass, and (E) At least one fatty acid selected from compounds having a fatty acid full ester of a 3 to 6-valent alcohol and having an acid value of 4 or less. Full ester compound 0.01-1.0 parts by mass,
A polyacetal resin composition comprising and.
2. 2. The polyacetal resin composition according to 1 above, wherein the (E) trihydric to hexahydric alcohol is at least one selected from pentaerythritol and glycerin.
3. 3. The polyacetal resin composition according to 1 or 2 above, wherein the acid value of the (E) fatty acid full ester is 2 or less.
4. A polyacetal resin molded product obtained by molding the compositions according to 1 to 3 above.

According to the present invention, there are provided a polyacetal resin composition in which the amount of formaldehyde generated is significantly reduced and the mold deposit during production is stably suppressed, and a molded product.

Hereinafter, the present invention will be described in detail.
<(A) Polyacetal polymer>
The polyacetal polymer used in the present invention may be a homopolymer having an oximethylene group (-OCH _2- ) as a constituent unit, or a copolymer having another comonomer unit in addition to the oximethylene unit. , It is preferable that it is a copolymer.

Generally, it is produced by copolymerizing formaldehyde or a cyclic oligomer of formaldehyde as a main monomer and a compound selected from cyclic ether or cyclic formal as a comonomer, and usually, the unstable portion at the end is removed by alkaline hydrolysis or the like. And is stabilized.

In particular, trioxane, which is a cyclic trimer of formaldehyde, is generally used as the main monomer. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is purified by a method such as distillation before use. The trioxane used for the polymerization preferably contains as little impurities as possible such as water, methanol and formic acid.
As the comonomer, general cyclic ether and cyclic formal, or a compound capable of forming a branched structure or a crosslinked structure can be used as a comonomer, and glycidyl ether or the like can be used alone or in combination of two or more.

The polyacetal copolymer as described above can generally be obtained by adding an appropriate amount of a molecular weight modifier and cationically polymerizing using a cationic polymerization catalyst. The molecular weight adjuster used, the cationic polymerization catalyst, the polymerization method, the polymerization apparatus, the deactivation treatment of the catalyst after the polymerization, the end stabilization treatment method of the crude polyacetal copolymer obtained by the polymerization, and the like are known from many documents. , Basically any of them can be used.

The molecular weight of the polyacetal copolymer used in the present invention is not particularly limited, but a polyacetal copolymer having a weight average molecular weight of about 10,000 to 400,000 is preferable. Further, the melt index (measured at 190 ° C. and a load of 2.16 kg according to ASTM-D1238), which is an index of the fluidity of the resin, is preferably 0.1 to 100 g / 10 minutes, more preferably 0.5. ~ 80g / 10 minutes.

It is particularly preferable that the polyacetal polymer (A) used in the present invention has specific terminal properties. Specifically, the hemiformal terminal group amount is 1.0 mmol / kg or less, the formyl terminal group amount is 0.5 mmol / kg or less, and the unstable terminal group amount is 0.5% by mass or less. Here, the hemiformal terminal group is represented by -OCH ₂ OH, and is also referred to as a hydroxymethoxy group or a hemiacetal terminal group. The formyl terminal group is indicated by -CHO. The amounts of such hemiformal terminal groups and formyl terminal groups can be determined by ¹ H-NMR measurement, and the specific measurement method thereof can be referred to the method described in JP-A-2001-11143.

The amount of unstable terminal groups indicates the amount of a portion that is present at the terminal portion of the polyacetal polymer and is unstable to heat or base and easily decomposed. The amount of unstable terminal groups is such that 1 g of a polyacetal copolymer is placed in a pressure-resistant airtight container together with 100 ml of a 50% (volume%) methanol aqueous solution containing 0.5% (% by volume) ammonium hydroxide, and the temperature is 180 ° C. for 45 minutes. The amount of formaldehyde decomposed and eluted in the solution obtained by heat treatment, cooling, and opening is quantified and expressed in% by volume with respect to the polyacetal copolymer.

The polyacetal polymer (A) used in the present invention preferably has a hemiformal terminal group amount of 1.0 mmol / kg or less, more preferably 0.6 mmol / kg or less. The amount of formyl terminal groups is preferably 0.5 mmol / kg or less, more preferably 0.1 mmol / kg or less. The amount of unstable terminal groups is preferably 0.5% by mass or less, more preferably 0.3% by mass or less. The lower limits of the hemiformal terminal group amount, the formyl terminal group amount, and the unstable terminal group amount are not particularly limited.

As described above, the polyacetal polymer (A) having specific terminal characteristics can be produced by reducing impurities contained in the monomer and the comonomer, selecting a production process, optimizing the production conditions thereof, and the like.

As the method for producing the polyacetal polymer (A) having specific terminal characteristics that satisfies the requirements of the present invention below, for example, the method described in JP-A-2009-286874 can be used. However, the method is not limited to this method.

In the present invention, when a polyacetal resin having a branched or crosslinked structure is added to the polyacetal polymer (A) and used, the blending amount thereof is 0.01 to 20 parts by mass with respect to 100 parts by mass of the polyacetal polymer (A). It is particularly preferably 0.03 to 5 parts by mass.

<(B) Hindered phenolic antioxidant>
The hindered phenolic antioxidant (B) used in the present invention includes a commonly used monocyclic hindered phenol compound, a polycyclic hindered compound linked with a group containing a hydrocarbon group or a sulfur atom. Examples thereof include a phenol compound, a hindered phenol compound having an ester group or an amide group, and specific examples thereof include the compounds described in JP-A-2009-286874 and JP-A-2008-156489, IRGANOX 1010, 1035 and 1076. , 1098, 1135, 1330, 1425, 245, 259, 565, 3114, etc. (the above product names, manufactured by BASF Japan, Inc.) and the like can be used.
These hindered phenolic antioxidants (B) can be used alone or in combination of two or more. The amount of the hindered phenol-based antioxidant (B) added is 0.01 to 3 parts by mass with respect to 100 parts by mass of the polyacetal polymer (A).

<(C) Hydrazide compound>
Examples of the hydrazide compound (C) used in the present invention include aliphatic carboxylic acid hydrazide compounds (stearic acid hydrazide, 12-hydroxystearic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, eikosan diacid hydrazide and the like. ), Unsaturated aliphatic carboxylic acid hydrazide-based compounds (7,11-octadecadien-1,18-dicarbohydrazide, etc.), alicyclic carboxylic acid hydrazide-based compounds (cyclohexanecarboxylic acid hydrazide, 1,4-cyclohexanedicarbonate, etc.) Acid dihydrazide, etc.), aromatic carboxylic acid hydrazide compounds (4-hydroxy-3,5-di-t-butylphenylbenzoic acid hydrazide, 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, isophthalic acid dihydrazide, 2,6 -Naphthalenedicarboxylic acid dihydrazide, etc.), heteroatom-containing carboxylic acid hydrazide-based compounds (1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydrandin, etc.), polymer-type carboxylic acid hydrazide-based compounds, and the like.

Further, the polymers described in JP-A-2009-286874, JP-A-2008-156489, JP-A-55-145259, JP-A-56-105905, and copolymers described in US Pat. No. 3,574,786. Such compounds can be used. These hydrazide compounds can be used alone or in combination of two or more.

In the present invention, the amount of the hydrazide compound (C) added as described above is 0.01 to 1.0 parts by mass, preferably 0.03 to 0.8 parts by mass with respect to 100 parts by mass of the polyacetal polymer (A). It is a mass part.

<(D) Fatty acid calcium salt>
The fatty acid constituting the fatty acid calcium salt of the present invention may be a saturated fatty acid or an unsaturated fatty acid. Examples of such fatty acids include monovalent or divalent fatty acids having 10 or more carbon atoms, for example, monovalent saturated fatty acids having 10 or more carbon atoms [capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, stearic acid. , 10-34 saturated fatty acids with 10-34 carbon atoms (preferably 10-30 saturated fatty acids with carbon atoms) such as araquinic acid, behenic acid, montanic acid, etc.], monovalent unsaturated fatty acids with 10 or more carbon atoms [oleic acid, linoleic acid, etc. 10-34 unsaturated fatty acids with 10-34 carbon atoms (preferably unsaturated fatty acids with 10-30 carbon atoms) such as linolenic acid, arachidonic acid, and erucic acid], divalent fatty acids with 10 or more carbon atoms (dibasic fatty acids) [sevacin Divalent 10-30 saturated fatty acids (preferably divalent 10-20 saturated fatty acids) such as acids, dodecanoic acid, tetradecanoic acid, and tapsia acid, and divalent carbons such as decenoic acid and dodecenedioic acid. Number 10-30 unsaturated fatty acid (preferably divalent 10-20 unsaturated fatty acid) and the like] can be exemplified.

Further, in the above fatty acid, a part of the hydrogen atom is substituted with a substituent such as a hydroxyl group, and the fatty acid having one or a plurality of hydroxyl groups in the molecule (for example, hydroxy saturation such as 12-hydroxystearic acid). Fatty acids having 10-26 carbon atoms, etc.) are also included, and fatty acids having slightly different carbon atoms depending on the accuracy of purification are also included. In the present invention, particularly preferable fatty acid calcium salts are calcium stearate, calcium 12-hydroxystearate, and calcium palmitate.

The content of the fatty acid calcium salt in the polyacetal resin composition is 0.01 part by mass or more and 0.5 part by mass or less with respect to 100 parts by mass of the polyacetal polymer. When the content of the fatty acid calcium salt is 0.01 parts by mass or more, it is preferable because the heat resistance of the molded body is improved, and when it is 0.5 parts by mass or less, it is preferable because the discoloration of the molded body is small. The content of the preferred fatty acid calcium salt is 0.02 parts by mass or more and 0.4 parts by mass or less.

<(E) At least one fatty acid full ester compound selected from compounds having an acid value of 4 or less, which is a fatty acid full ester of a 3- to 6-valent alcohol>
The (E) fatty acid full ester used in the present invention is preferably a polyhydric alcohol fatty acid ester which is a full ester compound of a fatty acid and a polyhydric alcohol having 3 or more and 6 or less hydroxyl groups. The esterification rate of the full ester does not necessarily have to be 100%, 80% or more is sufficient, 85% or more is preferable, and 90% or more is more preferable.

The polyhydric alcohol may be aliphatic or aromatic, but is preferably aliphatic in terms of affinity with the polyacetal polymer.

The valence of the polyhydric alcohol is 3 or more and 6 or less, but preferably 3 or more and 4 or less. The carbon number of the polyhydric alcohol is not particularly limited, but is preferably 3 or more and 10 or less, and more preferably 3 or more and 5 or less, in terms of affinity with the polyacetal resin.

Preferred polyhydric alcohols include, for example, glycerin, trimethylolpropane, pentaerythritol, mesoerythritol, pentitos, hexitol, sorbitol, diglycerin, triglycerin, dipentaerythritol and the like, with glycerin and pentaerythritol being more preferred. ..

The type of fatty acid is not particularly limited, but is preferably a fatty acid having 10 or more and 30 or less carbon atoms, and is an aliphatic carboxylic acid having 10 or more and 20 or less carbon atoms in terms of compatibility with the polyacetal resin. Is more preferable. Aliphatic carboxylic acids may be the same or different in the full ester in one molecule.

(E) Preferred fatty acids for forming the fatty acid full ester include, for example, stearic acid, palmitic acid, lauric acid and the like, and preferably stearic acid.

(E) As the fatty acid full ester, glycerin tristearate and pentaerythritol tetrastearate are preferably used, and pentaerythritol tetrastearate is more preferably used. As the component (E), two or more kinds of esterified products having different polyhydric alcohols and fatty acids and esterified products having different esterification rates may be used in combination.

The content of (E) fatty acid full ester in the present invention is 0.01 to 1.0 part by mass and 0.05 to 0.5 part by mass with respect to 100 parts by mass of the (A) polyacetal polymer. Is more preferable.
The fatty acid full ester of the present invention is characterized by having an acid value of 4 or less. Further, the acid value is preferably 2 or less.
The acid value of the present invention is a value that can be measured by a neutralization titration method according to JIS K0070 (1992). By setting the acid value in this range, it is possible to suppress the generation of formaldehyde and suppress the mold deposit at the same time.

It is presumed that the mechanism of effect manifestation is the suppression of decomposition of the unstable terminal group of the polyacetal polymer by an appropriate acid component and the resulting reduction in the formation of mold deposit, which is the reaction product of formaldehyde and the hydrazide compound.

<Other additives>
A compound (F) selected from metal oxides and metal hydroxides can be further added to the polyacetal resin composition of the present invention in order to further improve thermal stability, long-term thermal stability, and the like. Yes and preferable. The amount added is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the polyacetal polymer (A).

As the metal oxide and the metal hydroxide, calcium oxide, magnesium oxide, zinc oxide, calcium hydroxide, magnesium hydroxide and the like are preferable.

At least one mold release agent (G) selected from fatty acid amides, polyoxyalkylene glycols, and silicone compounds may be added to the polyacetal resin composition of the present invention in order to further improve molding processability and the like. It is possible and preferable. The amount added is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the polyacetal polymer (A).

The polyacetal resin composition of the present invention further comprises a weather resistance (light) stabilizer, an impact resistance improver, a gloss control agent, a slidability improver, a filler, a colorant, a nucleating agent, an antistatic agent, and a surfactant. It is possible to blend an activator, an antibacterial agent, an antifungal agent, a fragrance agent, a foaming agent, a compatibilizer, a physical property improving agent (boric acid or a derivative thereof, etc.), a fragrance, etc., which impairs the object of the present invention. It is possible to improve various properties according to each additive. Further, it is also possible to use an antioxidant, a heat-resistant stabilizer, a processability improver and the like other than those described above in combination.

Examples of the weather-resistant (light) stabilizer include (a) benzotriazole-based compounds, (b) benzophenone-based compounds, (c) aromatic benzoate-based compounds, (d) cyanoacrylate-based compounds, and (e) oxalic acid anilide-based compounds. Known and commercially available compounds such as (f) hydroxyphenyl-1,3,5-triazine compound and (g) hindered amine compound can be used.

The weather resistant (light) stabilizer may be used alone or in combination of two or more compounds of the same type or different types. As the weather resistant (light) stabilizer, it is preferable to use a hindered amine compound (g) in combination with at least one selected from other weather resistant (light) stabilizers (a) to (f), and in particular, a benzotriazole based agent. It is preferable to use the compound (a) in combination with the hindered amine compound (f).

The content of the weather-resistant (light) stabilizer is, for example, 0 to 5 parts by mass (for example, 0.01 to 5 parts by mass), preferably 0.1 to 4 parts by mass, based on 100 parts by mass of the polyacetal polymer. More preferably, it may be about 0.1 to 2 parts by mass.

Impact resistance improvers include thermoplastic polyurethane-based resins, acrylic core-shell polymers, thermoplastic polyester-based elastomers, styrene-based elastomers, olefin-based elastomers, polyamide-based elastomers, rubber components (natural rubber, etc.) and the like.

The gloss control agent includes acrylic core-shell polymer, thermoplastic polyurethane, thermoplastic polyester elastomer, polyamide-based elastomer, alkyl (meth) acrylate alone or copolymer (polymethylmethacrylate, etc.), polycarbonate-based resin, styrene-based resin (). Polystyrene, AS resin, AES resin, etc.), olefin resin (polypropylene, cyclic polyolefin, etc.) and the like are included.

Sliding properties include olefin polymers (polyethylene, polypropylene, copolymers of ethylene and α-olefins, modified products of these acid anhydrides, etc.), waxes (polyethylene wax, etc.), silicone oils and silicones. Includes fluororesins, fluororesins (polytetrafluoroethylene, etc.), fatty acid esters, etc.

Fillers include inorganic or organic fibrous fillers such as glass fiber, carbon fiber, boron fiber, potassium titanate fiber, metal fiber, and aramid fiber, plate-like filler such as glass flakes, mica, and graphite, and milled fiber. Examples thereof include glass beads, glass balloons, talc, kaolin, silica, caustic soil, clay, wallusnite, alumina, graphite fluoride, silicon carbide, boron nitride, and powder granular fillers such as metal powder.

As the colorant, various dyes and pigments can be used. Examples of the dye include an azo dye, an anthraquinone dye, phthalocyanine dye, and naphthoquinone dye. Both inorganic pigments and organic pigments can be used as pigments, and as inorganic pigments, titanium pigments, zinc pigments, carbon black, iron pigments, molybdenum pigments, cadmium pigments, lead pigments, cobalt pigments and Aluminum pigments can be exemplified, and examples of the organic pigments include azo pigments, anthracinone pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, perinone pigments, isoindolin pigments, dioxazine pigments and slen pigments. Etc. can be exemplified.

Of these, carbon black, titanium oxide, phthalocyanine pigments, and perylene pigments, which are colorants having a high light shielding effect, can be used to improve weather resistance (light). The amount of the colorant to be blended is not particularly limited, and a general amount for coloring is used.

The method for producing the polyacetal resin composition of the present invention is not particularly limited, and can be prepared by various methods conventionally known as a method for preparing a resin composition. For example, (1) a method of mixing all the components constituting the composition, supplying the mixture to an extruder and melt-kneading the mixture to obtain a pellet-shaped composition, and (2) a part of the components constituting the composition. A method of supplying residual components from the main feed port of the extruder and melt-kneading them to obtain a pellet-shaped composition, (3) once preparing pellets having different compositions by extrusion or the like, and mixing the pellets. Then, a method of adjusting to a predetermined composition can be adopted.

In the preparation of the composition using an extruder, it is preferable to use an extruder having one or more devolatilization vent ports, and further, water or a low boiling point can be found at any place from the main feed port to the devolatilization vent port. It is preferable to supply about 0.1 to 10 parts by mass of alcohols with respect to 100 parts by mass of the polyacetal resin, and to remove formaldehyde and the like generated in the extrusion step from the devolatilization vent port together with water and low boiling point alcohols. Thereby, the amount of formaldehyde generated from the polyacetal resin composition and the molded product thereof can be further reduced.

The polyacetal resin composition of the present invention thus prepared can be molded by various conventionally known molding methods such as injection molding, extrusion molding, compression molding, vacuum molding, blow molding, foam molding and the like. ..

The present invention also includes recycling of a molded product comprising the polyacetal resin composition and the colored polyacetal resin composition according to the above. Specifically, a recycled resin composition obtained by melt-kneading and extruding a molded product made of these resin compositions or a pulverized product thereof alone or together with a resin material or molded product having the same or different composition, and these. It is a recycled molded product obtained by melt-kneading a molded product made of the above resin composition or a pulverized product thereof alone or together with a resin material or a molded product having the same or different composition.

In this way, the recycled resin compositions and recycled molded products prepared by repeating the heat of fusion history also have an extremely low level of formaldehyde generation, similar to the polyacetal resin composition on which they are based. Is.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. In addition, all "parts" in an Example and a comparative example represent a mass part. In addition, various characteristics evaluated in Examples and Comparative Examples and their evaluation methods are as follows. The unit of the numerical values shown in Tables 1 and 2 is a mass part.

<Evaluation of formaldehyde generation (VOC) from molded products>
Using the polyacetal resin compositions prepared in Examples and Comparative Examples, a flat plate-shaped test piece (100 mm × 40 mm × 2 mm) was molded under the following conditions. Two of these flat plate-shaped test pieces were enclosed in a 10 L polyvinyl fluoride sampling bag, degassed, 4 L of nitrogen was added, and heated at 65 ° C. for 2 hours, and then 0.5 ml / ml of nitrogen in the sampling bag was added. 3 L was extracted with min, and the generated formaldehyde was adsorbed on a DNPH (2,4-dinitrophenylhydrazine) collecting tube (Sep-Pak DNPH-Silica manufactured by Waters).

After that, the reaction product of DNPH and formaldehyde was solvent-extracted from the DNPH collection tube with acetonitrile, and the amount of formaldehyde generated was determined by a calibration curve method using a standard substance of the reaction product of DNPH and formaldehyde by high performance liquid chromatography. , The amount of formaldehyde generated per unit mass of the test piece (μg / g) was calculated.

* Molding machine: FANUC ROBOSHOT α-S100ia (FANUC Corporation)
* Molding conditions: Cylinder temperature (° C) Nozzle-C1-C2-C3
190 190 180 160 ° C
Injection pressure 60 (MPa)
Injection speed 1.0 (m / min)
Mold temperature 80 (° C)

<Evaluation of mold deposit (MD)>
Using the polyacetal resin compositions prepared in Examples and Comparative Examples, a mold deposit test piece (20 mmφ × 1 mmt disk type) was molded under the following conditions.
[Evaluation methods]
After continuous molding of 10000 shots, the surface of the cavity in the mold was visually observed, and the amount of deposits was visually determined according to the following criteria.
0: No deposits are confirmed 1: No deposits are confirmed 2: Deposits are confirmed 3: A large amount of deposits are confirmed

* Molding machine: FANUC ROBOSHOT S-2000i 50B (FANUC Corporation)
* Molding conditions: Cylinder temperature (° C) Nozzle-C1-C2-C3
205 215 205 185 ° C
Injection pressure 40 (MPa)
Injection speed 1.5 (m / min)
Mold temperature 23 (° C)

Each component used in the examples is as follows.
-Polyacetal polymer (A)
a-1: Polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane (melt index (measured at 190 ° C., load 2160 g): 27 g / 10 min).
・ Hindered phenolic antioxidant (B)
b-1: Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (Irganox245, manufactured by BASF)
-Hydrazide compound (C)
c-1: Sebacic acid dihydrazide c-2: Adipic acid dihydrazide fatty acid calcium salt (D)
d-1: Calcium stearate / fatty acid full ester (E)
e-1: Pentaerythritol tetrastearate Acid value 1.8 (manufactured by Emery Oreo Chemicals Co., Ltd .: Roxyol VPG861)
e-2: Pentaerythritol tetrastearate Acid value 3.7 (manufactured by NOF CORPORATION: Unistar H-476)
e-3: Pentaerythritol tetrastearate Acid value 10 (manufactured by RIKEN Vitamin Co., Ltd .: Riquester EW-400)
e-4: Glycerin tristearate Acid value 2.8 (manufactured by RIKEN Vitamin Co., Ltd .: Poem S-95)

As described above, it is clear that the amount of formaldehyde generated and the amount of mold deposit generated are stably suppressed within the range of the acid value of the present invention.

Claims (4)

(A) With respect to 100 parts by mass of the polyacetal polymer
(B) Hindered phenolic antioxidant 0.01 to 3 parts by mass,
(C) 0.01 to 1 part by mass of the hydrazide compound,
(D) Fatty acid Calcium salt 0.01 to 0.5 parts by mass, and (E) At least one fatty acid selected from compounds having a fatty acid full ester of a 3 to 6-valent alcohol and having an acid value of 4 or less. Full ester compound 0.01-1.0 parts by mass,
A polyacetal resin composition comprising and. The polyacetal resin composition according to claim 1, wherein the (E) trihydric to hexahydric alcohol is at least one selected from pentaerythritol and glycerin. The polyacetal resin composition according to claim 1 or 2, wherein the acid value of the (E) fatty acid full ester is 2 or less. A polyacetal resin molded product obtained by molding the composition according to any one of claims 1 to 3.