Polyacetal resin composition

Abstract

To provide a polyacetal resin composition that is well suppressed in the generation of formaldehyde and mold deposits.SOLUTION: A resin composition contains (A) polyacetal resin 100 pts.mass, (B) a fatty acid dihydrazide compound of formula (1) with a fat chain having an even carbon number of 0.01-1 pt.mass, and (C) a fatty acid dihydrazide compound of formula (2) with a fat chain having an odd carbon number of 0.01-1 pt.mass.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyacetal resin composition.

Background Art

[0002] Polyacetal resin is a material excellent in rigidity, strength, toughness, slidability and creep properties. The applications of polyacetal resin cover a wide range as resin materials for various mechanical parts such as automotive parts, electrical and electronic parts, and industrial parts.

[0003] When polyacetal resin is decomposed by the action of heat, light, oxygen, acid, alkali, etc., formaldehyde is generated. In particular, there are concerns that formaldehyde gas is generated by thermal decomposition during production or molding processing, deteriorating the working environment, and that formaldehyde gas is generated from resin products, deteriorating the indoor environment.

[0004] As a method for suppressing the generation of formaldehyde from polyacetal resin, a method of adding a fatty acid dihydrazide compound is known. However, a polyacetal resin composition containing a hydrazide compound is likely to generate mold deposits during molding. The generation of mold deposits reduces work efficiency and is a factor in deteriorating the surface state of molded products.

[0005] As a method of using a hydrazide compound to reduce mold deposits while suppressing the amount of formaldehyde generated, a method of using two different fatty acid dihydrazide compounds in combination is disclosed (Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in recent years, the demand for simultaneously suppressing the amount of formaldehyde generation and mold deposit has been further increasing, and the method described in the above Patent Document 1 may not be sufficient.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a polyacetal resin composition excellent in suppressing the amount of formaldehyde generation and mold deposit.

Means for Solving the Problems

[0009] The present inventors have found that when fatty acid dihydrazide compounds having different molecular symmetries are used in combination, the aggregation of fatty acid dihydrazide on the mold is inhibited, and the generation of mold deposit can be significantly reduced, thereby completing the present invention.

[0010] That is, the present invention is as follows. [1] (A) 100 parts by mass of a polyacetal resin, (B) 0.01 to 1 part by mass of a fatty acid dihydrazide compound represented by the following general formula (1) in which the number of carbon atoms in the fatty chain is an even number, (C) 0.01 to 1 part by mass of a fatty acid dihydrazide compound represented by the following general formula (2) in which the number of carbon atoms in the fatty chain is an odd number, and A polyacetal resin composition characterized by comprising

Chemical formula

Chemical formula

[0011] According to the present invention, it is possible to provide a polyacetal resin composition having both a low formaldehyde generation amount and a low mold deposit. [Mode for Carrying Out the Invention]

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following description and can be variously modified and implemented within the scope of the gist.

[0013] [Polyacetal Resin Composition] The polyacetal resin composition of the present embodiment contains (A) a polyacetal resin, (B) a fatty acid dihydrazide compound having an even number of carbon atoms in the fatty acid chain, and (C) a fatty acid dihydrazide compound having an odd number of carbon atoms in the fatty acid chain. Hereinafter, each component constituting the polyacetal resin composition of the present embodiment will be described in detail.

[0014] [(A) Polyacetal Resin] The (A) polyacetal resin contained in the polyacetal resin composition of the present embodiment (hereinafter, may be simply referred to as the “(A) component”) has a repetition of oxymethylene units (acetal structure) represented by (-CH2O-) as the main constituent unit, and known ones may be used. The (A) polyacetal resin used in the present embodiment may be a homopolymer composed only of these oxymethylene units, or may be a copolymer (including block copolymers) or terpolymer containing constituent units other than oxymethylene units. Furthermore, it may have not only a linear structure but also a branched or crosslinked structure. The above polyacetal resin may be used alone or in combination of two or more. The (A) polyacetal resin preferably contains 30 to 100% by mass, more preferably 50 to 100% by mass, and still more preferably 70 to 100% by mass of polyacetal copolymer, with the total amount of the (A) polyacetal resin being 100% by mass.

[0015] As the method for producing the (A) polyacetal resin in the present embodiment, known methods may be used. For example, a polyacetal homopolymer can be obtained by homopolymerizing a monomer of formaldehyde or a cyclic oligomer of formaldehyde such as its trimer (trioxane) and tetramer (tetraoxane). Furthermore, the obtained polyacetal homopolymer can be stabilized by a known method (for example, a method of reacting the polymerization terminal with an ether group or an ester group). Strictly speaking, a polyacetal homopolymer has a main chain substantially composed of only oxymethylene units, but in the embodiments of the present invention, those containing 99% by mass or more of oxymethylene units can be regarded as substantially equivalent to a homopolymer.

[0016] As the constituent unit (copolymer unit) other than the oxymethylene unit in the polyacetal copolymer, an oxyethylene unit (-CH2CH2O-) is preferable. Such polyacetal copolymers can be obtained by copolymerizing a monomer of formaldehyde or a cyclic oligomer of formaldehyde such as its trimer (trioxane) and tetramer (tetraoxane) with a cyclic ether such as ethylene oxide or 1,3-dioxolane or a cyclic formal. When obtaining a polyacetal copolymer from trioxane and 1,3-dioxolane, it is preferable to use 0.1 to 60 mol% of 1,3-dioxolane based on 100 mol% of trioxane, more preferably 0.1 to 20 mol%, and even more preferably 0.13 to 10 mol%. Furthermore, the obtained polyacetal copolymer can be stabilized by a known method (for example, a method of melting with a quaternary ammonium compound and decomposing unstable terminal portions). The polyacetal copolymer preferably contains oxyethylene units in an amount of 1 to 10% by mass, more preferably 1 to 5% by mass, and even more preferably 1 to 3% by mass of the entire main chain of the polymer.

[0017] In this embodiment, the melt flow rate (MFR) of the (A) polyacetal resin is preferably 2 to 50 g / 10 min, more preferably 2 to 30 g / 10 min, and even more preferably 5 to 15 g / 10 min. By setting the MFR value within the above range, a polyacetal resin composition excellent in fluidity and mechanical strength can be obtained. Note that the MFR can be measured under the conditions of 190°C and a load of 2.16 kg in accordance with ISO 1133-1.

[0018] The content of the (A) polyacetal resin is preferably 60% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of the polyacetal resin composition.

[0019] <(B) Fatty acid dihydrazide having an even number of carbon atoms in the fatty chain> The (B) fatty acid dihydrazide having an even number of carbon atoms in the fatty acid chain contained in the polyacetal resin composition of the present embodiment is a fatty acid dihydrazide having 2n carbon atoms in the fatty acid chain represented by the following general formula (1) being 2, 4, 6, 8, 10, 12 (n = 1 to 6). (Hereinafter, the (B) fatty acid dihydrazide having an even number of carbon atoms in the fatty acid chain may be simply referred to as the “(B) component”).

[0020]

Chemical formula

[0021] The (B) component in the present embodiment is represented by the above general formula (1), n is an integer from 1 to 6, and it is preferably an integer from 2 to 5 (that is, 2n is 4, 6, 8, or 10), and more preferably 2, 4, or 5 (that is, 2n is 4, 8, or 10). Specific examples of the (B) component include succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and tetradodecanedioic acid dihydrazide. Among them, adipic acid dihydrazide, sebacic acid dihydrazide, and dodecanedioic acid dihydrazide are preferred, and sebacic acid dihydrazide is more preferred. The (B) component may be used alone or in combination of two or more.

[0022] In the polyacetal resin composition of the present embodiment, the content of the (B) component is 0.01 to 1 part by mass with respect to 100 parts by mass of the (A) polyacetal resin. Preferably it is 0.01 to 0.7 part by mass, and more preferably 0.01 to 0.5 part by mass. If the content of the (B) component is less than 0.01 part by mass, the amount of formaldehyde generated may not be sufficiently suppressed, and if it is more than 1 part by mass, the generation of mold deposits may not be sufficiently suppressed.

[0023] <(C) Fatty acid dihydrazide having an odd number of carbon atoms in the fatty acid chain> The fatty acid dihydrazide (C) contained in the polyacetal resin composition of the present embodiment, in which the fatty acid has an odd number of carbon atoms in the fatty acid chain, is a fatty acid dihydrazide represented by the following general formula (2) and having 1, 3, 5, 7, 9, or 11 carbon atoms (2m - 1) in the fatty acid chain (m = 1 to 6). (Hereinafter, the fatty acid dihydrazide in which the fatty acid chain has an odd number of carbon atoms may be simply referred to as the "(C) component".)

[0024] [Chemical formula] (In the formula, m is an integer from 1 to 6)

[0025] The (C) component in the present embodiment is represented by the above general formula (2), m is an integer from 1 to 6, and it is preferably an integer from 2 to 5 (that is, as (2m - 1), it is 3, 5, 7, or 9), and more preferably 2, 4, or 5 (that is, as (2m - 1), it is 3, 7, or 9). Specific examples of the (C) component include malonic acid dihydrazide, glutaric acid dihydrazide, pimelic acid dihydrazide, azelaic acid dihydrazide, undecanedioic acid dihydrazide, and tridecanedioic acid dihydrazide. Among them, glutaric acid dihydrazide, azelaic acid dihydrazide, and undecanedioic acid dihydrazide are preferable, and azelaic acid dihydrazide is more preferable from the viewpoint of suppressing the amount of formaldehyde generated. The (C) component may be used alone or in combination of two or more.

[0026] In the polyacetal resin composition of the present embodiment, the content of the (C) component is 0.01 to 1 part by mass with respect to 100 parts by mass of the (A) polyacetal resin. Preferably, it is 0.01 to 0.7 part by mass, and more preferably 0.01 to 0.5 part by mass. If the content of the (C) component is less than 0.01 part by mass, the amount of formaldehyde generated may not be sufficiently suppressed, and if it is more than 1 part by mass, the generation of mold deposits may not be sufficiently suppressed.

[0027] In this embodiment, the difference 2n - (2m - 1) between the number of carbon atoms 2n of the fatty acid chain of component (B) and the number of carbon atoms (2m - 1) of the fatty acid chain of component (C) is preferably an integer from -7 to 9, more preferably an integer from -5 to 5, still more preferably an integer from -3 to 3, and particularly preferably -1 or 1. When the difference in the number of carbon atoms of the fatty acid chains of component (B) and component (C) is within the above range, aggregation on the mold can be more inhibited, and the occurrence of mold deposits can be more suppressed.

[0028] In this embodiment, the ratio (B):(C) of the number of moles of component (B) to the number of moles of component (C) is preferably from 10:90 to 90:10, more preferably from 30:70 to 70:30, and still more preferably from 40:60 to 60:40. When the molar ratio (B):(C) is within this range, mold deposits generated when molding the polyacetal resin composition of this embodiment can be more suppressed.

[0029] Conventionally known additives can be blended into the polyacetal resin composition of this embodiment as needed. Examples of such additives include aging property improvers such as fatty acid metal salts, lubricants, weathering agents, light-resistant agents, mold release agents, nucleating agents, colorants, organic and inorganic reinforcing agents, and various thermoplastic elastomers. The content of the additive is preferably 40% by mass or less based on 100% by mass of the polyacetal resin composition.

[0030] The polyacetal resin composition of this embodiment can be produced by a known melt-kneading method. For example, component (A), component (B), component (C), and, if necessary, the additive can be mixed with a stirrer such as a Henschel mixer, and then supplied to a single-screw or twin-screw melt-kneading apparatus (extruder) for melt-kneading. Alternatively, component (A) can be supplied from the upstream of a single-screw or twin-screw extruder to be melted, and then component (B), component (C), and, if necessary, the additive can be supplied downstream for melt-kneading.

[0031] The polyacetal resin composition of this embodiment can be molded and used as a molded article. The molding method of the polyacetal resin composition is not particularly limited, and known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, molding with other materials, gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin-wall injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outser molding), melt blow molding, etc. can be mentioned. The shape of the molded body is not particularly limited, and examples include injection molded products, fibers / non-woven fabrics, sheets / films, and shaped extruded products. The molded product of the polyacetal resin composition of this embodiment can be used as molded products for various applications. For example, mechanical parts represented by gears, cams, sliders, levers, shafts, bearings, and guides, resin parts for outser molding or resin parts for insert molding (chassis, trays, side plate parts), parts for printers or copiers, parts for digital cameras or digital video equipment, parts for music, video, or information equipment, parts for communication equipment, parts for electrical equipment, and parts for electronic equipment. Also, as parts for automobiles, it is preferably used for fuel-related parts represented by gasoline tanks, fuel pump modules, valves, gasoline tank flanges, etc.; parts around doors; parts around seat belts; combi switch parts; and switches. Furthermore, it can also be preferably used as industrial parts represented by housing equipment.

[0032] The embodiments for carrying out the present invention have been described above, but the present invention is not limited to these embodiments. The present invention can be variously modified without departing from the gist thereof.

Examples

[0033] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited thereto.

[0034] Each raw material component used in the examples and comparative examples is as follows.

[0035] (A) Polyacetal resin Using boron trifluoride-di-n-butyl etherate as the polymerization catalyst and methylal as the molecular weight regulator, trioxane and 1,3-dioxolane were copolymerized to obtain a polyacetal copolymer. The polymerization was carried out by continuously feeding into a twin-screw paddle type continuous polymerization reactor (manufactured by Kurimoto Iron Works, Ltd., L / D = 14.8) set at 80°C. The supply amount of 1,3-dioxolane was set to 4.2 mol% based on the total supply amount of trioxane and 1,3-dioxolane. The obtained polyacetal copolymer was put into an aqueous solution of 0.5 mass% triethylamine to deactivate the polymerization catalyst. Subsequently, it was supplied to a twin-screw extruder with a vent (manufactured by Schloemann, L / D = 40) set at 200°C, melted, and then an aqueous solution of 0.8 mass% triethylamine was added in liquid form so as to be 20 mass ppm in terms of the mass of nitrogen, and the unstable part was decomposed while performing vacuum degassing to stabilize the polyacetal copolymer. After pelletization with a pelletizer, it was dried at 100°C for 2 hours. The MFR of the obtained polyacetal copolymer was 9.0 g / 10 min. The MFR value was measured using a MELT INDEXER manufactured by Toyo Seiki at a cylinder temperature of 190°C and a load of 2.16 kg in accordance with ISO 1133-1.

[0036] (B) Fatty acid dihydrazide with an even number of carbon atoms in the fatty chain (B1) Adipic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.) (B2) Sebacic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.) (B3) Dodecanedioic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0037] (C) Fatty acid dihydrazide with an odd number of carbon atoms in the fatty chain (C1) Malonic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.) (C2) Azelaic acid dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0038] The measurement methods and evaluation methods used for the examples and comparative examples are as follows.

[0039] (1) Formaldehyde generation amount Using an injection molding machine (IS-100GN manufactured by Toshiba Machine Co., Ltd.), under the conditions of a mold temperature of 80 °C, a cylinder temperature of 220 °C, an injection pressure of 35 MPa, an injection time of 15 seconds, and a cooling time of 20 seconds, test pieces (flat plates of 100 mm × 40 mm × 3 mm) were molded from the pellets of the polyacetal resin compositions obtained in the examples and comparative examples, and the formaldehyde generation amount released from the test pieces was measured. Specifically, the test piece was suspended in a 1 L polyethylene bottle containing 50 mL of distilled water so as not to touch the distilled water and sealed. This was heated at 60 °C for 3 hours and left standing at room temperature for 60 minutes. Formaldehyde in the distilled water was reacted with acetylacetone in the presence of ammonium ions, and the absorption peak at a wavelength of 412 nm was measured with a UV spectrometer for the reaction product to determine the formaldehyde generation amount. The formaldehyde generation amount was expressed as the amount of formaldehyde (μg / g) per 1 g of the polyacetal resin. The smaller this value is, the more the formaldehyde generation amount is suppressed, indicating a preferable situation. In automotive interior applications, it is preferable that this value is less than 2 μg / g.

[0040] (2) Mold deposit property Molded products (arrow-shaped molds of 30 mm × 12 mm × 2 mm) were continuously molded from the pellets of the polyacetal resin compositions obtained in the examples and comparative examples, and the presence or absence of mold deposits (MD) was confirmed after 500 shots and 1000 shots. The presence or absence of mold deposits was observed from a direction perpendicular to the surface on the fixed side of the mold. When no MD was observed at all, it was rated as "〇 (good)"; when even a little colorless MD was observed, it was rated as "△ (bad)"; when interference colors (interference fringes) occurred (presumed to be MD with a thickness of about 200 nm or more), it was rated as "× (inferior)". An injection molding machine (Ti-30G manufactured by Toyo Seiki Co., Ltd.) was used for molding, and the mold setting temperature was 60 °C, the cylinder temperature was 200 °C, the injection pressure was 34 MPa, the injection time was 20 seconds, and the cooling time was 15 seconds.

[0041] [Examples 1 to 20, Comparative Examples 1 to 9] The components were mixed to have the composition shown in Table 1, supplied to a twin-screw extruder (PCM30 manufactured by Ikegai), melt-kneaded under the conditions of a screw rotation speed of 60 rpm and a cylinder set temperature of 200 °C, and then pelletized. The obtained pellets were dried using a hot air dryer at 80 °C for 3 hours. The evaluation results were summarized in Table 1.

[0042]

Table 1

[0043]

Table 2

Industrial Applicability

[0044] The polyacetal resin composition of the present invention has a low formaldehyde generation amount and mold deposit, and thus can be suitably used in fields such as electrical and electronic applications that require high precision and good appearance, and automotive interior applications that require reduction of volatile organic compounds.

Claims

1. (A) 100 parts by mass of a polyacetal resin, and (B) 0.01 to 1 part by mass of a fatty acid dihydrazide compound represented by the following general formula (1) in which the fatty acid has an even number of carbon atoms in the fatty acid chain, and (C) 0.01 to 1 part by mass of a fatty acid dihydrazide compound represented by the following general formula (2) in which the fatty acid has an odd number of carbon atoms in the fatty acid chain, A polyacetal resin composition, characterized by containing the same. 【Chemical 1】 (In the formula, n is an integer of 1 to 6.) [Chemical 2] (In the formula, m is an integer of 1 to 6.)

2. The polyacetal resin composition according to claim 1, wherein the difference 2n - (2m - 1) between the number of carbon atoms 2n of the fatty acid chain of the component (B) and the number of carbon atoms (2m - 1) of the fatty acid chain of the component (C) is an integer of -5 to 5.

3. The polyacetal resin composition according to claim 1 or 2, wherein the molar ratio of the component (B) to the component (C) is in the range of 10:90 to 90:

10.

4. The polyacetal resin composition according to any one of claims 1 to 3, wherein the number of carbon atoms 2n of the fatty acid chain of the component (B) is 4, 6, 8, or 10.

5. The polyacetal resin composition according to any one of claims 1 to 3, wherein the number of carbon atoms (2m - 1) of the fatty acid of the component (C) is 3, 5, 7, or 9.

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