Method for producing polyacetal resin composition

Abstract

The purpose of the present invention is to provide a method for producing a polyacetal resin composition that is excellent in terms of rigidity and creep resistance characteristics. A method for producing a polyacetal resin composition according to the present invention includes: a step (I) for producing a polyacetal copolymer (A) by copolymerizing trioxane (a), a cyclic acetal compound (b), and an aliphatic glycidyl ether compound (c) that has a chlorine content of 4% or more in the presence of a linear formal compound (d); a step (II) for producing a linear polyacetal resin (B) by copolymerizing trioxane (a') and a cyclic acetal compound (b'); and a step (III) for mixing and melt-kneading the linear polyacetal resin (B) and the polyacetal copolymer (A).

Description

Method for producing polyacetal resin composition

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

[0002] Polyacetal resins have an excellent balance of mechanical properties, chemical resistance, sliding properties, etc., and are easy to process. Therefore, they are widely used as engineering plastics, primarily in electrical and electronic components, automotive parts, and various other mechanical components. In recent years, as their applications have expanded and diversified, the properties required of polyacetal resins have tended to become more sophisticated. Therefore, there is a demand for polyacetal resins that have rigidity and creep resistance while maintaining excellent fluidity, moldability, thermal stability, and sliding properties.

[0003] Known methods for obtaining polyacetal resins having the above-mentioned properties include the methods disclosed in Patent Documents 1 and 2. However, in order to satisfy the properties required of polyacetal resins, further improvements in rigidity and creep resistance are required.

[0004] JP 2003-342442 A Japanese Patent No. 7179046 A

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a polyacetal resin composition having excellent rigidity and creep resistance.

[0006] The present inventors have conducted extensive research and found that the above problems can be solved, leading to the completion of the present invention. Specifically, the present invention is configured as follows [1] to [6].

[0007] [1] A method for producing a polyacetal copolymer (A) comprising: a step (I) of copolymerizing 100 parts by mass of trioxane (a) with 0.05 to 5 parts by mass of a cyclic acetal compound (b) and 0.001 to 0.5 parts by mass of an aliphatic glycidyl ether compound (c) having a chlorine content of 4% by weight or more in the presence of a linear formal compound (d); a step (II) of copolymerizing 97.0 to 99.5% by weight of trioxane (a') with 0.5 to 3.0% by weight of a cyclic acetal compound (b') to produce a linear polyacetal resin (B); and a step (III) of mixing 0.1 to 10 parts by mass of the polyacetal copolymer (A) with 100 parts by mass of the linear polyacetal resin (B) and melt-kneading the mixture; the diglycidyl ether compound (c) is at least one selected from the group consisting of trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and pentaerythritol tetraglycidyl ether; the step (I) further comprises a step of determining the ratio (β + γ + δ) / α to be 10 μmol / g or less, where α is the total mass [g] of the compounds (a), (b), and (c), β is the number of moles of the compound (d), γ is the total number of moles of water contained in the compounds (a), (b), and (c), and δ is the total number of moles of methanol; and the chlorine content is calculated by a quantitative determination method using a fundamental parameter method based on the measured intensity of fluorescent X-rays.

[0008] [2] The method for producing a polyacetal resin composition according to [1], wherein the cyclic acetal compounds (b) and (b') are 1,3-dioxolane or 1,4-butanediol formal.

[0009] [3] The method for producing a polyacetal resin composition according to either [1] or [2], wherein the linear formal compound (d) is at least one selected from the group consisting of methylal, ethylal, and dibutoxymethane.

[0010] [4] The method for producing a polyacetal resin composition according to any one of [1] to [3], wherein the linear polyacetal resin (B) has a melt flow rate of 1 to 50 g / 10 min.

[0011] [5] A polyacetal resin composition produced by the method according to any one of [1] to [4].

[0012] According to the present invention, a method for producing a polyacetal resin composition excellent in rigidity and creep resistance can be provided.

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0014] <Method for producing polyacetal resin composition> The method for producing a polyacetal resin composition includes a step (I) of producing a polyacetal copolymer (A), a step (II) of producing a linear polyacetal resin (B), and a step (III) of melt-kneading the polyacetal copolymer (A) and the linear polyacetal resin (B). Each step will be described in detail below.

[0015] [Step (I)] Step (I) is a step of producing a polyacetal copolymer (A) by copolymerizing 0.05 to 5 parts by mass of a cyclic acetal compound (b) and 0.001 to 0.5 parts by mass of an aliphatic glycidyl ether compound (c) having a chlorine content of 4% by weight or more, relative to 100 parts by mass of trioxane (a), in the presence of a linear formal compound (d).

[0016] <<Trioxane (a)>> Trioxane is a cyclic trimer of formaldehyde. It is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is purified by distillation or the like.

[0017] <<Cyclic Acetal Compound (b)>> The cyclic acetal compound is a compound having an oxyalkylene group having two or more carbon atoms in the ring, and is a compound copolymerizable with trioxane.

[0018] Examples of cyclic acetal compounds include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolane, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, etc. Of these, 1,3-dioxolane and 1,4-butanediol formal are preferred.

[0019] The content of the cyclic acetal compound (b) is 0.05 to 5 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the trioxane (a).

[0020] <<Aliphatic Glycidyl Ether Compound (c)>> The aliphatic glycidyl ether compound has a structure that can form a branched or crosslinked structure in the skeleton of the polyacetal copolymer.

[0021] The aliphatic glycidyl ether compound according to one embodiment of the present invention is at least one selected from the group consisting of trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and pentaerythritol tetraglycidyl ether. By selecting the aliphatic glycidyl ether compound from the above compounds, a polyacetal resin composition excellent in rigidity and creep resistance can be produced.

[0022] The aliphatic glycidyl ether compound according to one embodiment of the present invention has a chlorine content of 4% by weight or more. By using the aliphatic glycidyl ether compound having a chlorine content of 4% by weight or more, a polyacetal resin composition excellent in rigidity and creep resistance can be produced.

[0023] The chlorine content is preferably 4% by weight or more and 10% by weight or less, and more preferably 4% by weight or more and 8.5% by weight or less.

[0024] The chlorine content of the aliphatic glycidyl ether compound is calculated by a quantitative method using a fundamental parameter (FP) method based on the measured intensity of fluorescent X-rays using an X-ray fluorescence analyzer.

[0025] The content of the aliphatic glycidyl ether compound having a chlorine content of 4% by weight or more is 0.001 to 0.5 parts by mass relative to 100 parts by mass of trioxane. By setting the content of the aliphatic glycidyl ether compound (c) to 0.001 to 0.5 parts by mass, a polyacetal resin composition excellent in rigidity and creep resistance can be produced.

[0026] The content of the aliphatic glycidyl ether compound is preferably 0.01 to 0.5 parts by mass, more preferably 0.05 to 0.5 parts by mass.

[0027] <Linear Formal Compound (d)> The linear formal compound according to one embodiment of the present invention is used as a molecular weight regulator.

[0028] Examples of linear formals include methylal, ethylal, dibutoxymethane, bis(methoxymethyl) ether, bis(ethoxymethyl) ether, bis(butoxymethyl) ether, etc. Among these, methylal, ethylal, or dibutoxymethane is preferred.

[0029] The content of the linear formal compound can be appropriately set in accordance with the desired molecular weight of the polyacetal copolymer (A).

[0030] Step (I) also includes a step of setting the ratio (β + γ + δ) / α to 10 μmol / g or less, where α is the total mass [g] of trioxane (a), cyclic acetal compound (b), and aliphatic glycidyl ether compound (c), β is the number of moles of linear formal compound (d), γ is the total number of moles of water contained in (a), (b), and (c), and δ is the total number of moles of methanol.

[0031] By setting (β + γ + δ) / α to 10 μmol / g or less, a polyacetal resin composition excellent in rigidity and creep resistance can be produced. Note that the water and methanol contained in (a), (b), and (c) above are derived from the respective impurities.

[0032] Furthermore, (β+γ+δ) / α is preferably 3 to 10 μmol / g, more preferably 4 to 8 μmol / g.

[0033] <<Production Method of Polyacetal Copolymer (A)>> The polyacetal copolymer (A) can be produced by continuously supplying trioxane (a), a cyclic acetal compound (b), an aliphatic glycidyl ether compound (c), and a linear formal compound (d) in the presence of a cationic polymerization catalyst and performing bulk polymerization under predetermined conditions using a known method and polymerization apparatus.

[0034] Examples of polymerization apparatus include batch and continuous types. In the batch type, a commonly used reaction vessel equipped with a stirrer can be used. In the continuous type, a co-kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle screw extruder, a vented twin-screw extruder, etc. can be used. The continuous type is the industrially preferred production method.

[0035] (Cationic Polymerization Catalyst) Examples of the cationic polymerization catalyst include Lewis acids and protonic acids.

[0036] Examples of Lewis acids include boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.

[0037] Examples of the protonic acid include perfluoroalkanesulfonic acids, heteropolyacids, and isopolyacids.

[0038] Examples of perfluoroalkanesulfonic acids include trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonafluorobutanesulfonic acid, undecafluoropentanesulfonic acid, tridecafluorohexanesulfonic acid, pentadecafluoroheptanesulfonic acid, and heptadecafluorooctane sulfonic acid. Examples of heteropolyacids include phosphotungstic acid, phosphomolybdic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silicomolybdic acid, silicomolybdotungstic acid, and silicomolybdotungstenovanadic acid. Examples of isopolyacids include paratungstic acid, metatungstic acid, paramolybdic acid, metamolybdic acid, metapolyvanadic acid, and isopolyvanadic acid.

[0039] The amount of the cationic polymerization catalyst added is preferably 0.1 ppm or more based on the total amount of all monomers. The upper limit of the amount of the polymerization catalyst added is not particularly limited, but is preferably 100 ppm or less.

[0040] [Step (II)] Step (II) is a step of producing a linear polyacetal resin (B) by copolymerizing 97.0 to 99.5% by weight of trioxane (a') and 0.5 to 3.0% by weight of a cyclic acetal compound (b').

[0041] The content of trioxane (a') is preferably 98.0 to 99.0% by weight.

[0042] The cyclic acetal compound (b') can be selected from the above-mentioned cyclic acetal compounds, and the content of the cyclic acetal compound (b') is preferably 1.0 to 2.5% by weight.

[0043] By setting the contents of trioxane (a') and cyclic acetal compound (b') as described above, the melt flow rate (MFR) described below can be adjusted to fall within a desired range.

[0044] The MFR of the linear polyacetal resin (B) is preferably 1 to 50 g / 10 min, more preferably 1 to 40 g / 10 min, and particularly preferably 2 to 35 g / 10 min. By using a linear polyacetal resin (B) having an MFR of 1 to 50 g / 10 min, a polyacetal resin composition excellent in rigidity and creep resistance can be produced.

[0045] The MFR of the linear polyacetal resin (B) can be measured, for example, using a Melt Indexer Model L220 (manufactured by Tateyama Scientific High-Technologies Co., Ltd.).

[0046] <<Method for Producing Linear Polyacetal Resin (B)>> The linear polyacetal resin (B) can be produced by a known method using the above-mentioned batch or continuous polymerization apparatus.

[0047] [Step (III)] Step (III) is a step of producing a polyacetal resin composition by mixing 100 parts by mass of the linear polyacetal resin (B) with 0.1 to 10 parts by mass of the polyacetal copolymer (A) and melt-kneading the mixture.

[0048] <<Method for Producing Polyacetal Resin Composition>> The polyacetal resin composition can be produced by melt-kneading the polyacetal copolymer (A) and the linear polyacetal resin (B) at a temperature of 180 to 270°C for at least 30 seconds or more using a known method and the above-mentioned batch-type or continuous-type polymerization apparatus.

[0049] <Other Additives> The polyacetal copolymer, linear polyacetal resin, and polyacetal resin composition obtained in steps (I) to (III) may contain various known stabilizers and additives.

[0050] Examples of stabilizers include hindered phenol compounds, hindered amine compounds, nitrogen-containing basic compounds, alkali or alkaline earth metal oxides, hydroxides, inorganic salts, carboxylates, etc. Examples of additives include colorants such as dyes and pigments, fluorescent brighteners, lubricants, nucleating agents, release agents, antistatic agents, surfactants, etc.

[0051] <Polyacetal Resin Composition> The polyacetal resin composition produced by the above steps (I) to (III) has excellent mechanical properties such as rigidity and creep resistance.

[0052] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0053] <Method for Producing Polyacetal Copolymer (A)> A continuous mixer / reactor consisting of a barrel with an outer jacket for passing a heat (cool) medium and a cross section shaped like two partially overlapping circles, and a rotating shaft with paddles, was used. While rotating the two rotating shafts with paddles at a constant speed so that the peripheral speed of the paddle tips was 0.5 m / s, trioxane (a), a cyclic acetal compound (b), an aliphatic glycidyl ether compound (c), and a linear formal compound (d) were continuously fed in the amounts shown in Table 1. Bulk polymerization was carried out by continuously feeding a homogeneous mixture of boron trifluoride gas catalyst, mixed at a concentration of 0.005% by mass relative to the trioxane, calculated as boron trifluoride, into the reactor. The reaction product discharged from the polymerization reactor was quickly passed through a crusher and added to an aqueous solution containing 0.1% by mass of triethylamine at 80°C to deactivate the catalyst. After separation, washing, and drying, a crude polyacetal copolymer was obtained.

[0054] To 100 parts by mass of the crude polyacetal copolymer obtained by the above method, 0.3 part by mass of pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as a stabilizer and 0.15 part by mass of melamine were added, and the mixture was melt-kneaded at 210°C in a twin-screw extruder to obtain polyacetal copolymers A-1 to A-14.

[0055] <Method for producing linear polyacetal resin (B)> Using the above-mentioned continuous mixer reactor, bulk polymerization was carried out by continuously feeding trioxane (a') and cyclic acetal compound (b') in the amounts shown in Table 2, and continuously feeding boron trifluoride as a catalyst in an amount of 0.005% by weight based on the trioxane. The reaction product discharged from the polymerization reactor was subjected to the same treatment as above, to obtain linear polyacetal resins B-1 to B-7.

[0056] <Method for producing polyacetal resin composition> Polyacetal copolymer (A) and linear polyacetal resin (B) were melt-kneaded at 210°C in a twin-screw extruder in the amounts shown in Tables 3 to 5 to obtain polyacetal resin compositions 1 to 27.

[0057] <Method for quantifying chlorine content> Aliphatic glycidyl ether compounds c-1 to c-5 in Table 1 were each placed in a liquid measuring container, and the chlorine content was calculated by the FP method using a fluorescent X-ray analyzer. <Measurement conditions> Measurement device: ZSX Primus IV (manufactured by Rigaku Corporation) Measurement type: EZ Scan Sample type: Liquid Component form: Metal Residue: C ９ H １０ O ３ Sample film absorption correction: P.E. Film Impurity correction: None Matching library: None Helium atmosphere correction: Yes

[0058] <Method for Measuring MFR> The MFR (g / 10 min) of the linear polyacetal resin (B) in Table 2 was measured using a Melt Indexer Model L220 manufactured by Tateyama Scientific High-Technologies Corporation.

[0059] The abbreviations and symbols in Tables 1 to 5 are as follows:

[0060] DO: 1,3-dioxolane BDF: butanediol formal MFR: melt flow rate c-1: trimethylolpropane triglycidyl ether (chlorine content: 6.3% by weight) c-2: trimethylolpropane triglycidyl ether (chlorine content: 7.9% by weight) c-3: glycerin triglycidyl ether (chlorine content: 4.2% by weight) c-4: pentaerythritol tetraglycidyl ether (chlorine content: 7.0% by weight) c-5: trimethylolpropane triglycidyl ether (chlorine content: 3.5% by weight) MeAL: methylal EtAL: ethylal DBM: dibutoxymethane

[0061] [Evaluation] Polyacetal resin compositions 1 to 27 were subjected to tensile tests and creep property evaluations as described below. The evaluation results are shown in Tables 3 to 5.

[0062] <Tensile Test Evaluation> Polyacetal resin compositions 1 to 27 were each placed in an injection molding machine to prepare Type A test pieces in accordance with ISO 3167. Using these test pieces, tensile strength was measured in accordance with ISO 527-1 and 2.

[0063] <Evaluation of Creep Properties> Test specimens were prepared using polyacetal resin compositions 1 to 27 in the same manner as the test specimens prepared for the tensile test evaluation. A high-temperature, high-load condition of 80°C in the atmosphere and a load of 21 MPa was applied using a creep tester, and the time (hr) until the test specimen broke was measured.

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] As shown in Tables 3 to 5, it was found that by using a polyacetal copolymer (A) prepared using an aliphatic glycidyl ether compound having a chlorine content of 4% by weight or more, a polyacetal resin composition excellent in rigidity and creep resistance can be produced.

[0070] The polyacetal resin composition of the present invention has excellent mechanical properties and is therefore expected to contribute to the development and widespread use of polyacetal resin compositions.

Claims

1. A method for producing a polyacetal copolymer (A) by copolymerizing, with respect to 100 parts by mass of trioxane (a), 0.05 to 5 parts by mass of a cyclic acetal compound (b) and 0.001 to 0.5 parts by mass of an aliphatic glycidyl ether compound (c) having a chlorine content of 4% by weight or more in the presence of a linear formal compound (d); a step (II) by copolymerizing, with respect to 100 parts by mass of trioxane (a), 97.0 to 99.5 parts by weight of trioxane (a') and 0.5 to 3.0 parts by weight of a cyclic acetal compound (b'), to produce a linear polyacetal resin (B); and a step (III) of mixing 0.1 to 10 parts by mass of the polyacetal copolymer (A) with 100 parts by mass of the linear polyacetal resin (B) and melt-kneading the mixture, the aliphatic glycidyl ether compound (c) is at least one selected from the group consisting of trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and pentaerythritol tetraglycidyl ether; and step (I) further comprises the step of: setting the total mass [g] of (a), (b), and (c) as α, the number of moles of (d) as β, the total number of moles of water contained in (a), (b), and (c) as γ, and the total number of moles of methanol as δ, so that (β + γ + δ) / α is 10 μmol / g or less; and the chlorine content is calculated by a quantitative method using a fundamental parameter method based on the measured intensity of fluorescent X-rays.

2. The method for producing a polyacetal resin composition according to claim 1, wherein the cyclic acetal compounds (b) and (b') are 1,3-dioxolane or 1,4-butanediol formal.

3. The method for producing a polyacetal resin composition according to claim 1, wherein the linear formal compound (d) is at least one selected from the group consisting of methylal, ethylal and dibutoxymethane.

4. The method for producing a polyacetal resin composition according to claim 1, wherein the linear polyacetal resin (B) has a melt flow rate of 1 to 50 g / 10 min.

5. A polyacetal resin composition produced by the method according to any one of claims 1 to 4.

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