Method for producing polyacetal resin composition and polyacetal resin composition

Abstract

This invention provides a method for manufacturing a polyacetal resin composition that reduces formaldehyde production and mold deposits, as well as the polyacetal resin composition itself. More specifically, this invention provides a method for manufacturing a polyacetal resin composition containing 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea. The method includes a mixing step of incorporating ethylene urea into the polyacetal resin. In this mixing step, the heating and melting mixing time for incorporating ethylene urea into the polyacetal resin is 10 to 60 minutes, and the heating and melting mixing temperature is 220°C to 240°C.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a polyacetal resin composition and to the polyacetal resin composition itself. More specifically, this invention relates to a method for manufacturing a polyacetal resin composition that reduces formaldehyde production and mold deposits, and to the polyacetal resin composition itself. This invention also relates to granules, molded articles, vehicle parts, etc., formed from the above-described polyacetal resin compositions. Background Technology

[0002] Polyacetal resin, also known as formaldehyde polymer, includes homopolymers formed by the polymerization of formaldehyde and copolymers formed by the polymerization of cyclic oligomers such as trioxane and comonomers. Polyacetal resin exhibits excellent balance in mechanical properties, chemical resistance, and lubrication, and is also easy to process. Therefore, as a representative engineering plastic, it is widely used, primarily in electrical and electronic components, automotive parts, and various other mechanical components.

[0003] However, due to the thermal processes during resin manufacturing and molding, polyacetal resin undergoes slight thermal decomposition. As a result, although in extremely small amounts, formaldehyde is still produced, leading to mold contamination and a deterioration of the working (hygienic) environment during molding operations. Furthermore, formaldehyde from resin products may also contribute to sick building syndrome. In response to this situation, the Japanese Ministry of Health, Labour and Welfare has issued guidelines for indoor formaldehyde concentrations in buildings (upper limit 0.08 ppm), requiring further reductions in formaldehyde emissions from polyacetal resin molded products.

[0004] Therefore, various methods have been proposed to improve the thermal stability of polyoxymethylene copolymers. One method to improve thermal stability is the addition of additives such as amines, amides, and hydrazines that can react with decomposition gases such as formaldehyde produced by thermal decomposition. The technique of suppressing formaldehyde production from granules or molded products by incorporating additives into polyacetal resins is well known. In the prior art, various substances have been studied as additives. Proposed additives include melamine-formaldehyde polymers (Patent Document 1), polyamine reactants obtained by reacting ammonia or its derivatives with the reaction products of polyamines and cyanuric chloride (Patent Document 2), dicyandiamide compounds (Patent Document 3), silane compounds (Patent Document 4), nitrogen-containing compounds—borates (Patent Document 5), glyoxal diurea compounds (Patent Document 6), urea derivatives and / or amidine derivatives (Patent Document 7), condensates of phenols and basic nitrogen-containing compounds and aldehydes (Patent Document 8), and spirocyclic compounds containing triazine rings (Patent Document 9).

[0005] However, the above methods only address one aspect of improving moldability: either suppressing formaldehyde production or suppressing the formation of mold deposits caused by additive bleed-out.

[0006] Therefore, it is desirable to develop polyacetal resin compositions that reduce formaldehyde production and mold deposits.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 5-271516 Patent Document 2: Japanese Patent Application Publication No. 7-207118 Patent Document 3: Japanese Patent Application Publication No. 8-208946 Patent Document 4: Japanese Patent Application Publication No. 9-235447 Patent Document 5: Japanese Patent Application Publication No. 10-36630 Patent Document 6: Japanese Patent Application Publication No. 10-182928 Patent Document 7: Japanese Patent Application Publication No. 2000-34417 Patent Document 8: Japanese Patent Application Publication No. 2002-212384 Patent Document 9: Japanese Patent Application Publication No. 2003-113289 Summary of the Invention

[0008] The technical problem that the invention aims to solve The present invention provides a method for manufacturing a polyacetal resin composition that reduces formaldehyde production and mold deposits, as well as the polyacetal resin composition.

[0009] Technical means for solving technical problems The inventors of this invention have conducted repeated and in-depth research, resulting in the development of a method for manufacturing a polyacetal resin composition that reduces formaldehyde production and mold deposits, as well as the polyacetal resin composition itself. That is, this invention includes the following methods.

[0010] <1> A method for manufacturing a polyacetal resin composition, wherein the polyacetal resin composition contains 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea, the method comprising a mixing step of mixing ethylene urea into the polyacetal resin, wherein the heating and melting mixing time for mixing ethylene urea into the polyacetal resin in the mixing step is 10 to 60 minutes and the heating and melting mixing temperature is 220°C to 240°C.

[0011] <2> The method for manufacturing a polyacetal resin composition as described in <1>, wherein the amount of hot water extracted ethylene urea after freezing and pulverizing the polyacetal resin composition and then hot water extracting it at 120°C for 3 hours is less than 0.10% by mass relative to the total amount of the polyacetal resin composition.

[0012] <3> The method for manufacturing a polyacetal resin composition as described in <1> or <2>, wherein the formaldehyde production of the above-mentioned polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

[0013] <4> A polyacetal resin composition manufactured using any one of <1> to <3>.

[0014] <5> A polyacetal resin composition containing 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea, wherein the amount of ethylene urea extracted by hot water extraction at 120°C for 3 hours after freezing and pulverizing the above polyacetal resin composition is less than 0.10% by weight relative to the total amount of the above polyacetal resin composition.

[0015] <6> The polyacetal resin composition as described in <5>, wherein the formaldehyde production of the above polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

[0016] <7> The polyacetal resin composition as described in <5> or <6>, wherein the polyacetal resin composition is prepared by mixing ethylene urea into the polyacetal resin, and the heating and melting mixing time for mixing ethylene urea into the polyacetal resin is 10 minutes to 60 minutes.

[0017] <8> The polyacetal resin composition as described in any one of <5> to <7>, wherein the polyacetal resin composition is prepared by mixing ethylene urea into the polyacetal resin, and the heating and melting mixing temperature for mixing ethylene urea into the polyacetal resin is 220°C to 240°C.

[0018] <9> A granule formed from any one of <4> to <8> of a polyacetal resin composition.

[0019] <10> A molded article formed from any one of <4> to <8> of a polyacetal resin composition.

[0020] <11> A vehicle component formed from any one of <4> to <8> of a polyacetal resin composition.

[0021] Invention Effects By employing the manufacturing method of the polyacetal resin composition of the present invention, it is possible to manufacture a polyacetal resin composition that reduces formaldehyde production and mold deposits. Attached Figure Description

[0022] Figure 1 It is a droplet mold designed so that the resin composition is introduced from the gate G and the generated gas easily accumulates at the tip P. Detailed Implementation

[0023] The present invention will be described in detail below, but the following description is not intended to limit the scope of the invention.

[0024] <1> Polyacetal resin composition The polyacetal resin composition of the present invention contains polyacetal resin and ethylene urea. The components are described below.

[0025] <1-1> Polyacetal resin The polyacetal resin used in this invention has the following properties: -(-O-CRH-). n Polyacetals with repeating units of the acetal structure (where R represents a hydrogen atom or an organic group) typically have an oxymethylene group (-CH2O-) where R is a hydrogen atom as the main structural unit. The polyacetal resin used in this invention can be a homopolymer composed solely of this oxymethylene unit, or it can be a copolymer (block copolymer) or ternary polymer containing structural units other than the oxymethylene unit. Furthermore, it can be not only linear but also branched or cross-linked.

[0026] As structural units other than the oxymethylene unit, examples include oxyalkylene groups with 2 to 10 carbon atoms, such as oxyethylene (-CH2CH2O-), oxypropylene (-CH2CH2CH2O-), and oxybutylene (-CH2CH2CH2CH2O-), which may have branched chains. Among these, oxyalkylene groups with 2 to 4 carbon atoms that may have branched chains are preferred, and oxyethylene is particularly preferred. The content of oxyalkylene groups other than the oxymethylene unit in the polyacetal resin is typically 0.1 to 20% by mass. The content of oxyalkylene groups with 2 or more carbon atoms in the formaldehyde polymer can be determined by... 1 H-NMR determination.

[0027] Several methods for manufacturing polyacetal resins are known, and in this invention, polyacetal resins obtained by any method can be used. For example, as a method for manufacturing polyacetal resins with oxymethylene and oxyalkylene groups having 2 to 4 carbon atoms as structural units, it can be manufactured by copolymerizing cyclic oligomers containing oxymethylene groups, such as formaldehyde trimer (trioxane) or tetraoxane (tetraoxane), with cyclic oligomers containing oxyalkylene groups having 2 to 4 carbon atoms, such as ethylene oxide, 1,3-dioxane, 1,3,6-trioxane-octane, and 1,3-dioxane-heptane. As the polyacetal resin, copolymers of cyclic oligomers such as trioxane or tetraoxane with ethylene oxide or 1,3-dioxane are preferred, and copolymers of trioxane and 1,3-dioxane are particularly preferred. The melt index (ASTM-D1238 standard: 2.16 kg at 190°C) of polyacetal resin is typically 1 to 100 g / 10 minutes, preferably 0.5 to 80 g / 10 minutes.

[0028] <1-2> Ethylene urea Ethylene urea is added as a formaldehyde scavenger. By adding ethylene urea, the formaldehyde release from the granules and molded sheets of the polyacetal resin composition can be reduced.

[0029] As ethylene urea, a product obtained by reacting 1,2-ethylenediamine with urea using conventional methods can be used, and the material can be in flake, granule, or particulate form. Its content is not limited, and it can be used in an amount of 0.001 to 2 parts by weight, specifically 0.01 to 1 part by weight, more specifically 0.1 to 1 part by weight, and more preferably 0.2 to 0.5 parts by weight, relative to 100 parts by weight of the polyacetal copolymer. When the ethylene urea content is within the above range, the formaldehyde generation of the polyacetal resin composition granules and molded sheets can be reduced. Since the product and the formaldehyde polymer obtained by melt mixing are less prone to decomposition and degradation, the formaldehyde generation is reduced, and the volatility of ethylene urea is reduced due to the condensation reaction between ethylene urea and formaldehyde, thereby reducing the amount of mold deposits.

[0030] In a preferred embodiment of the present invention, the polyacetal resin composition contains 0.2 to 0.5 parts by weight of ethylene urea relative to 100 parts by weight of the polyacetal resin. In embodiments of the present invention, the ethylene urea relative to 100 parts by weight of the polyacetal resin may, for example, be 0.20 parts by weight, 0.25 parts by weight, 0.30 parts by weight, 0.35 parts by weight, 0.40 parts by weight, 0.45 parts by weight, or 0.50 parts by weight. In one embodiment of the present invention, the ethylene urea relative to 100 parts by weight of the polyacetal resin may, for example, be: 0.20 parts by weight to 0.25 parts by weight, 0.20 parts by weight to 0.30 parts by weight, 0.20 parts by weight to 0.35 parts by weight, 0.20 parts by weight to 0.40 parts by weight, 0.20 parts by weight to 0.45 parts by weight, 0.20 parts by weight to 0.50 parts by weight; 0.25 parts by weight to 0.30 parts by weight, 0.25 parts by weight to 0.35 parts by weight, 0.25 parts by weight to 0.4 parts by weight, 0.25 parts by weight to 0.45 parts by weight, 0.25 parts by weight to 0.50 parts by weight; 0.30-0.35 parts by weight, 0.3-0.40 parts by weight, 0.30-0.45 parts by weight, 0.30-0.50 parts by weight; 0.35 parts by weight to 0.40 parts by weight, 0.35 parts by weight to 0.45 parts by weight, 0.35 parts by weight to 0.50 parts by weight; 0.40 to 0.45 parts by weight, 0.40 to 0.50 parts by weight; 0.45 parts by weight to 0.50 parts by weight.

[0031] In a preferred embodiment of the present invention, a polyacetal resin composition is provided containing 0.2 to 0.5 parts by weight of ethylene urea relative to 100 parts by weight of polyacetal resin.

[0032] <1-3> Other ingredients The polyacetal resin composition of the present invention may also contain hydroxides of alkali metals or alkaline earth metals (calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, etc.), inorganic acid salts, or alkoxides. For example, hydroxides of sodium, potassium, calcium, magnesium, etc., carbonates, phosphates, silicates, borates, etc., inorganic acid salts, methoxides, ethanolates, etc., and alkoxides.

[0033] In the polyacetal resin composition of the present invention, in addition to the above-mentioned components, various known additives or fillers may be added as needed, without prejudice to the purpose of the present invention. Examples of additives include antioxidants, formaldehyde or formic acid removers, end-group stabilizers, fillers, colorants, lubricants, release agents, antistatic agents, flame retardants, reinforcing agents, light stabilizers, and pigments; examples of fillers include glass fibers, glass sheets, glass beads, talc, mica, and potassium titanate whiskers.

[0034] <2> Method for manufacturing polyacetal resin composition The method for manufacturing the polyacetal resin composition of the present invention is a method for manufacturing a polyacetal resin composition containing polyacetal resin and ethylene urea, including a mixing step of mixing ethylene urea into the polyacetal resin.

[0035] After the polyacetal resin (formaldehyde polymer) is discharged from the polymerizer, it can be pulverized as needed using a turbo mill or similar equipment before heating and melting it (or before blending during mixing).

[0036] When blending the crude polymer with the stabilizer, the blending can be carried out using known methods. For example, a mixer connected in series with the aforementioned polymerizer for mixing the product and the terminator can be used for melt blending. The apparatus for melt blending preferably has a venting function. Examples of such apparatus include single-shaft or multi-shaft continuous extrusion mixers with at least one vent, and bi-shaft surface-renewal horizontal mixers. These apparatuses can be used individually or in combination.

[0037] Without pre-blending the crude polymer with the stabilizer, the stabilizer can be continuously supplied to the crude polymer feed line. Alternatively, the crude polymer and stabilizer can be supplied to the twin-screw extruder via different feed lines, where they are heated and melt-blended within the twin-screw extruder.

[0038] Known stabilizers include, for example, antioxidants such as triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] {sometimes called ethylene bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxym-tolyl)propionate]}, heat stabilizers such as melamine, additional formaldehyde scavengers, acid supplements, etc. Furthermore, additives such as inorganic fillers like glass fiber, crystallization promoters (nucleating agents), release agents, lubricants, and colorants can be added.

[0039] In the stabilization process, from the viewpoint of more effectively suppressing the odor generated during molding and the odor generated by the molded body, layered composite hydroxides such as hydrotalcite can be used to replace known stabilizers or used together with known stabilizers.

[0040] The amount of layered composite hydroxide added can be appropriately determined. Relative to 100 parts by weight of formaldehyde polymer, it is preferably 0.003 to 1 part by weight, more preferably 0.003 to 0.6 parts by weight, 0.004 to 0.6 parts by weight, or 0.005 to 0.5 parts by weight, even more preferably 0.005 to 0.2 parts by weight, and particularly preferably 0.01 to 0.2 parts by weight.

[0041] Like stabilizers, layered composite hydroxides can be blended with crude polymers and then melt-mixed under heat. They can also be continuously supplied to the crude polymer feed line or to a twin-screw extruder using a different feed line. Layered composite hydroxides can be added simultaneously with known stabilizers or added separately.

[0042] In the above-described mixing process, the heating and melting mixing time for mixing ethylene urea with polyacetal resin is not particularly limited, but is preferably 5 to 60 minutes, more preferably 10 to 60 minutes. When the heating and melting mixing time for mixing ethylene urea with polyacetal resin is within the above range, the product and the formaldehyde polymer obtained through melt mixing are less prone to decomposition and degradation, thereby reducing formaldehyde production. The volatility of ethylene urea is also reduced due to the condensation reaction between ethylene urea and formaldehyde, thereby reducing the amount of deposits adhering to the mold.

[0043] In embodiments of the present invention, the heating, melting, and mixing time can be, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes. In one embodiment of the present invention, the heating, melting, and mixing time can be, for example,: 5 minutes to 10 minutes, 5 minutes to 15 minutes, 5 minutes to 20 minutes, 5 minutes to 25 minutes, 5 minutes to 30 minutes, 5 minutes to 35 minutes, 5 minutes to 40 minutes, 5 minutes to 45 minutes, 5 minutes to 50 minutes, 5 minutes to 55 minutes, 5 minutes to 60 minutes; 10-15 minutes, 10-20 minutes, 10-25 minutes, 10-30 minutes, 10-35 minutes, 10-40 minutes, 10-45 minutes, 10-50 minutes, 10-55 minutes, 10-60 minutes; 15-20 minutes, 15-25 minutes, 15-30 minutes, 15-35 minutes, 15-40 minutes, 15-45 minutes, 15-50 minutes, 15-55 minutes, 15-60 minutes; 20-25 minutes, 20-30 minutes, 20-35 minutes, 20-40 minutes, 20-45 minutes, 20-50 minutes, 20-55 minutes, 20-60 minutes; 25-30 minutes, 25-35 minutes, 25-40 minutes, 25-45 minutes, 25-50 minutes, 25-55 minutes, 25-60 minutes; 30-35 minutes, 30-40 minutes, 30-45 minutes, 30-50 minutes, 30-55 minutes, 30-60 minutes; 35-40 minutes, 35-45 minutes, 35-50 minutes, 35-55 minutes, 35-60 minutes; 40-45 minutes, 40-50 minutes, 40-55 minutes, 40-60 minutes; 45-50 minutes, 45-55 minutes, 45-60 minutes; 50-55 minutes, 50-60 minutes; 55 to 60 minutes.

[0044] In a preferred embodiment of the present invention, the heating and melting mixing time is 5 to 60 minutes. In a preferred embodiment of the present invention, a method for manufacturing a polyacetal resin composition is provided, wherein the heating and melting mixing time is 5 to 60 minutes. In a more preferred embodiment of the present invention, the heating and melting mixing time is 10 to 60 minutes. In a more preferred embodiment of the present invention, a method for manufacturing a polyacetal resin composition is provided, wherein the heating and melting mixing time is 10 to 60 minutes.

[0045] In a preferred embodiment of the present invention, a polyacetal resin composition is provided, which is prepared by mixing ethylene urea into a polyacetal resin, wherein the heating and melting mixing time is 10 minutes to 60 minutes.

[0046] In the above-described mixing process, the mixing temperature when mixing ethylene urea into the polyacetal resin is only required to be above the melting point of the product obtained through the polymerization reaction, and is not particularly limited, but preferably 220°C to 240°C. When the mixing temperature when mixing ethylene urea into the polyacetal resin is within the above range, the product and the formaldehyde polymer obtained through melt mixing are less likely to decompose and deteriorate, thereby reducing the amount of formaldehyde produced. The volatility of ethylene urea is reduced due to the condensation reaction between ethylene urea and formaldehyde, thus reducing the amount of deposits adhering to the mold.

[0047] In embodiments of the present invention, the mixing temperature can be, for example, 220°C, 225°C, 230°C, 235°C, 240°C, etc. In one embodiment of the present invention, the mixing temperature can be, for example,: 220℃~225℃, 220℃~230℃, 220℃~235℃, 220℃~240℃; 225℃~230℃, 225℃~235℃, 225℃~240℃; 230℃~235℃, 230℃~240℃; 235℃~240℃.

[0048] In a preferred embodiment of the present invention, a method for manufacturing a polyacetal resin composition is provided, wherein the mixing temperature is 220°C to 240°C.

[0049] In a preferred embodiment of the present invention, a polyacetal resin composition is provided, which is prepared by incorporating ethylene urea into a polyacetal resin, wherein the heating and melting temperature for incorporating ethylene urea into the polyacetal resin is 220°C to 240°C.

[0050] In an embodiment of the present invention, a method for manufacturing the above-described polyacetal resin composition is provided, wherein the polyacetal resin composition is obtained by incorporating ethylene urea into the polyacetal resin, the heating and melting mixing time for incorporating ethylene urea into the polyacetal resin is 10 to 60 minutes, and the heating and melting mixing temperature for incorporating ethylene urea into the polyacetal resin is 220°C to 240°C.

[0051] In an embodiment of the present invention, the above-described polyacetal resin composition is provided, which is prepared by incorporating ethylene urea into polyacetal resin. The heating and melting mixing time for incorporating ethylene urea into polyacetal resin is 10 to 60 minutes, and the heating and melting mixing temperature for incorporating ethylene urea into polyacetal resin is 220°C to 240°C.

[0052] The pressure during melt mixing is not particularly limited, but in order to remove unreacted cyclic oligomers, formaldehyde components from cyclic oligomers, formaldehyde from the hemiacetal terminus, etc., it is preferable to perform the process under reduced pressure along with degassing. Degassing under reduced pressure is performed through the aforementioned vent. Therefore, when atmospheric pressure is 100 kPa, the melt mixing pressure, measured by an absolute pressure gauge, is preferably in the range of 10–100 kPa, more preferably in the range of 10–70 kPa, and particularly preferably in the range of 10–50 kPa. The rotational speed of the agitator blades during melt mixing is preferably 50–200 rpm in a twin-screw extruder, and preferably 1–100 rpm in a twin-shaft surface-renewal type horizontal mixing mill.

[0053] In a preferred embodiment of the present invention, a method for manufacturing a polyacetal resin composition is provided, the polyacetal resin composition comprising 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea. The above method includes a compounding step of mixing ethylene urea into polyacetal resin. In the above mixing process, the heating and melting mixing time for mixing ethylene urea into polyacetal resin is 10 to 60 minutes, and the heating and melting mixing temperature is 220°C to 240°C.

[0054] Thus, a composition of polyacetal resin (formaldehyde polymer) as the target product is obtained.

[0055] The manufacturing process described above is an example, and steps can be added or omitted as appropriate, or the content of each step can be changed. For example, after the polymerization reaction stops but before stabilization, the crude polymer can be washed, unreacted monomers can be separated and recovered, and dried as needed. Furthermore, if purification is required, washing, separation and recovery of unreacted monomers, and drying can also be performed after stabilization.

[0056] Furthermore, without prejudice to the purpose of this invention, known additives and other materials besides those described above may be used. Also, without prejudice to the purpose of this invention, the aforementioned materials may be used in processes different from those described above; for example, antioxidants and heat stabilizers that can be used in the stabilization process may be used in the polymerization termination process.

[0057] <3> Properties of polyacetal resin compositions <3-1> Formaldehyde production As mentioned above, there is a need to further reduce the formaldehyde generation from polyacetal resin molded articles. The formaldehyde generation from polyacetal resin molded articles can be measured, for example, according to the German Association of the Automotive Industry (DA) standard VDA275, but the method is not limited thereto. In the method of the present invention, the measurement is performed according to the DA standard VDA275.

[0058] In embodiments of the present invention, the formaldehyde emission of the above-mentioned polyacetal resin composition, as measured according to the German Association of the Automotive Industry (DA) standard 275, is 3 ppm or less. In embodiments of the present invention, the lower the formaldehyde emission of the above-mentioned polyacetal resin composition, as measured according to the DA standard 275, the better; for example, it is 3 ppm or less, 2.5 ppm or less, 2 ppm or less, 1.5 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, 0.2 ppm or less, or 0.1 ppm or less. In embodiments of the present invention, the formaldehyde emission of the above-mentioned polyacetal resin composition, as measured according to the DA standard 275, is, for example, 3 ppm, 2.5 ppm, 2 ppm, 1.5 ppm, 1 ppm, 0.5 ppm, 0.4 ppm, 0.3 ppm, 0.2 ppm, 0.1 ppm, or 0 ppm. In one embodiment of the present invention, a method for manufacturing the above-described polyacetal resin composition is provided, wherein the formaldehyde production of the above-described polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

[0059] In an embodiment of the present invention, a polyacetal resin composition containing 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea is provided, wherein the formaldehyde production of the above-mentioned polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

[0060] By reducing formaldehyde production, it is possible to improve the pollution of molding molds or the deterioration of the working (hygienic) environment during molding operations, thereby reducing the possibility of developing sick building syndrome and other problems.

[0061] <3-2> Hot water extraction volume The extraction of unreacted ethylene urea from the polyacetal resin composition prepared by the method of the present invention is carried out by hot water extraction. More specifically, the polyacetal resin composition is frozen and pulverized, and then subjected to hot water extraction at 120°C for 3 hours, during which the amount of ethylene urea extracted is measured.

[0062] In embodiments of the present invention, the amount of ethylene urea extracted by the above-described hot water extraction method is 0.10% by mass or less relative to the total amount of the polyacetal resin composition. In embodiments of the present invention, the amount of ethylene urea extracted by the above-described hot water extraction method is, for example, 0.10% by mass or less, 0.09% by mass or less, 0.08% by mass or less, 0.07% by mass or less, 0.06% by mass or less, 0.05% by mass or less, 0.04% by mass or less, 0.03% by mass or less, 0.02% by mass or less, or 0.01% by mass or less. In embodiments of the present invention, the amount of ethylene urea extracted by the above-described hot water extraction method is, for example, 0.10% by mass, 0.09% by mass, 0.08% by mass, 0.07% by mass, 0.06% by mass, 0.05% by mass, 0.04% by mass, 0.03% by mass, 0.02% by mass, 0.01% by mass, or 0% by mass.

[0063] In one embodiment of the present invention, a method for manufacturing the above-mentioned polyacetal resin composition is provided, wherein, regarding the above-mentioned polyacetal resin composition, the amount of hot water extracted ethylene urea after freezing and pulverizing the above-mentioned polyacetal resin composition and then hot water extracting it at 120°C for 3 hours is less than 0.10% by mass relative to the total amount of the above-mentioned polyacetal resin composition.

[0064] In an embodiment of the present invention, a polyacetal resin composition containing 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea is provided, wherein the amount of ethylene urea extracted by hot water extraction at 120°C for 3 hours after freezing and pulverizing the above polyacetal resin composition is less than 0.10% by weight relative to the total amount of the above polyacetal resin composition.

[0065] <3-3> Mold Deposits (MD, Mold Attachments) Mold deposits refer to substances that adhere to the mold used during molding, significantly reducing the operating environment during the molding of thermoplastic resin compositions. Less mold deposits result in better moldability. Mold deposit properties can be determined, for example, using the Sumitomo Heavy Industries, Ltd. Mini-mat M14 / 7B and the droplet-shaped mold shown in the figure, but are not limited to this method.

[0066] <4> Polyacetal resin composition obtained by the manufacturing method of the present invention In embodiments of the present invention, a polyacetal resin composition obtained by the above-described method for manufacturing a polyacetal resin composition is provided.

[0067] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is a polyacetal resin composition containing 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea, wherein the amount of ethylene urea extracted by hot water extraction at 120°C for 3 hours after freezing and pulverizing the above-mentioned polyacetal resin composition is less than 0.10% by weight relative to the total amount of the above-mentioned polyacetal resin composition.

[0068] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is prepared by mixing ethylene urea into polyacetal resin, and the heating and melting mixing time for mixing ethylene urea into polyacetal resin is 10 minutes to 60 minutes.

[0069] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is prepared by mixing ethylene urea into polyacetal resin, and the heating and melting mixing temperature for mixing ethylene urea into polyacetal resin is 220°C to 240°C.

[0070] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is prepared by mixing ethylene urea into polyacetal resin. The heating and melting mixing time for mixing ethylene urea into polyacetal resin is 10 minutes to 60 minutes, and the heating and melting mixing temperature for mixing ethylene urea into polyacetal resin is 220°C to 240°C.

[0071] <5> Molded products This invention provides molded articles formed from the polyacetal resin composition of this invention. The polyacetal resin composition of this invention can be molded using molding methods for polyacetal resins known in the art. Examples of molding methods include injection molding, extrusion molding, blow molding, vacuum forming, compression molding, pressing, and 3D printing, but are not limited to these methods.

[0072] <5-1> As molded articles formed from the polyacetal resin composition of the present invention, examples include raw materials such as granules, round bars, and thick plates, sheets, pipes, various containers, machinery, electrical equipment, automobiles, building materials, and other various parts, vehicle parts, and various other products that have been known to be used as polyacetal resins. The polyacetal resin composition of the present invention can be used for, for example, automotive parts, clothing parts, electrical and electronic molded parts and information recording equipment molded parts, medical equipment molded parts, household molded parts, rotating parts such as gears, bearing parts, sliding parts, press-fit parts, hinge parts, automotive fuel system parts, insert parts, snap-fit ​​parts, wading parts, various handles, various armrests, various chassis, side panel parts, spring parts, seat belt parts, automotive load-bearing plates, automotive combination switches, clips, pipe racks, wire racks, connectors, auxiliary clips, bumper storage materials, center consoles, door panels, door limiters, ball joints, undercut parts, optical fiber core wire connection storage boxes, disc boxes, magnetic tape boxes, trays for disc-shaped recording media, toner cartridges, film cartridges, protective covers, artificial joints, medical device insertion valves, vascular insertion devices, lids, powder containers, zipper parts, card holders, toothbrushes, eating utensils, covered curtain tracks, curtain track end caps, liquid container lids, writing instruments, folding storage baskets, baskets and their handles, etc.

[0073] <5-2> Granular material The polyacetal resin composition of the present invention can be shaped into granules using molding and processing methods for polyacetal resins known in the art. The present invention provides granules formed from the polyacetal resin composition of the present invention.

[0074] <5-3> Vehicle Components The polyacetal resin composition of the present invention can be molded into vehicle parts according to molding and processing methods of polyacetal resin known in the art. The present invention provides vehicle parts formed from the polyacetal resin composition of the present invention. Examples of vehicle parts include, but are not limited to, automotive parts, electrical-electronic molded parts and information recording device molded parts, rotating parts such as gears, bearing parts, sliding parts, press-fit parts, hinge parts, automotive fuel system parts, insert parts, snap-fit ​​parts, wading parts, various handles, various armrests, various chassis, side panel parts, spring parts, seat belt parts, automotive load-bearing plates, automotive combination switches, clips, tube racks, wire racks, connectors, auxiliary clips, bumper storage materials, center consoles, door trim panels, door limiters, etc.

[0075] Example The following description is based on embodiments of the present invention. However, the following embodiments are merely illustrative and are not intended to limit the scope of the present invention to the following embodiments.

[0076] <Preparation of Crude Formaldehyde Copolymer> In a biaxial continuous polymerizer with self-cleaning blades and a temperature set at 85°C, 4.2 parts by mass of 1,3-dioxane relative to 100 parts by mass of trioxane, 0.03 mmol of boron trifluoride diethyl ether as a polymerization catalyst relative to 1 mol of trioxane, and 0.6 mmol of methyl acetal as a molecular weight regulator were continuously added. The residence time of the polymerization product in the continuous polymerizer was maintained at 15 minutes, and the polymerization reaction was carried out continuously. N,N-diethylhydroxylamine as a polymerization terminator was added to the obtained polymerization product to a molar amount twice that of the polymerization catalyst, and then the product was pulverized to obtain a crude formaldehyde copolymer.

[0077] <Evaluation Method 1: Formaldehyde Production> Regarding the formaldehyde production, the amount produced per 1g of formaldehyde copolymer resin (unit: μg / g) was determined according to the following steps.

[0078] 1) The formaldehyde copolymer resin composition was pre-dried at 80°C for 3 hours and then molded into a circular test piece with a diameter of 50 mm and a thickness of 3 mm using a SAV-30-30 molding machine manufactured by Yamashiro Co., Ltd. at a barrel temperature of 215°C.

[0079] 2) Using the obtained test piece, the formaldehyde production was determined the day after molding according to the method described in the German Association of the Automotive Industry standard VDA275 (Automotive interior components - Quantification of formaldehyde release by the revised flask method).

[0080] Samples with a formaldehyde production of 3 μg / g per 1g of formaldehyde copolymer resin were evaluated as qualified.

[0081] <Evaluation Method 2: Hot Water Extraction Volume> Regarding the extraction of ethylene urea from the granules, the hot water extraction yield (phr) relative to 100 parts by weight of the formaldehyde copolymer resin composition was determined according to the following steps.

[0082] 1) After freezing and crushing the granules, take 2g of the powder that has passed through a 60-mesh metal sieve and put it into 25mL of pure water, and reflux at 120℃ for 3 hours.

[0083] 2) After reflux, the extract was filtered to remove powder, and the ethylene urea in the extract was quantified by liquid chromatography. The liquid chromatography conditions are as follows.

[0084] Device: SHIMADZU LC-10AD Chromatographic column: L-column 2 ODS (particle size 5 μm, φ4.6 mm × 250 mm) Column temperature: 40℃ Mobile phase: 10 mM potassium dihydrogen phosphate aqueous solution (5 mM potassium dihydrogen phosphate + 5 mM phosphoric acid) / acetonitrile = 25:2 (v / v) Flow rate: 0.5 mL / min Detector: Ultraviolet-Visible detector (detection wavelength: 215 nm) Samples with an extraction yield of less than 0.1 phr relative to 100 parts by weight of the formaldehyde copolymer resin composition were evaluated as qualified.

[0085] <Evaluation Method 3: Mold Deposits (MD, Mold Attachments)> Using an injection molding machine: a Mini-mat M14 / 7B manufactured by Sumitomo Heavy Industries, Ltd. and a droplet-shaped mold shown in the figure, 4000 continuous molding cycles were performed at a barrel temperature of 220°C and a mold temperature of 40°C. The amount of deposits on the mold was evaluated at four levels, A to D.

[0086] Figure 1 The droplet-shaped mold is designed so that the resin composition is introduced through the gate G, and the generated gas easily accumulates at the tip P. The gate G is 1mm wide and 1mm thick. Figure 1 In the middle, the width h1 is 14.5mm, the length h2 is 7mm, the length h3 is 27mm, and the thickness of the forming part is 3mm.

[0087] Samples A and B from the following categories are evaluated as acceptable.

[0088] A: There are absolutely no mold residues, and the mold contamination inhibition effect is excellent. B: Very few deposits on the mold, excellent mold contamination inhibition effect. C: Although there is a small amount of mold residue, the mold contamination suppression effect is good. D: The mold has many deposits, resulting in poor mold contamination control. <Examples 1-9, Comparative Examples 1-5> Relative to 100 parts by weight of the crude formaldehyde copolymer, 0.3 parts by weight of ethylene bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxym-tolyl)propionate] (IRGANOX (registered trademark) 245, manufactured by BASF) and 0.05 parts by weight of melamine (manufactured by Mitsui Chemicals) as stabilizers, along with the formulations described in the examples and comparative examples, were added and premixed using a Henschel mixer. The premixed crude formaldehyde copolymer was fed at a rate of 60 kg / h from a hopper equipped with an automatic metering feed function into a co-rotating twin-screw extruder (inner diameter 69 mm, L / D = 31.5), whereby the crude formaldehyde copolymer was melted at 220–250°C and continuously fed into a twin-shaft surface-renewal type horizontal mixer. The molten resin continuously extracted using a gear pump was formed into a strand, impregnated in a cooling water tank, and then fed to a granulator for granulation. The obtained granules were dried at 120°C for 12 hours using a hot air dryer to prepare the final sample.

[0089] <Comparative Example 6> Relative to 100 parts by weight of the crude formaldehyde copolymer, 0.3 parts by weight of ethylene bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxym-tolyl)propionate] (IRGANOX (registered trademark) 245, manufactured by BASF) as a stabilizer, 0.05 parts by weight of melamine (manufactured by Mitsui Chemicals), and the formulations described in the examples and comparative examples were added, and the mixture was premixed using a Henschel mixer. The premixed crude formaldehyde copolymer was fed into a co-rotating twin-screw extruder (inner diameter 29 mm, L / D = 18) with an automatic metering feed function from a hopper at a rate of 10 kg / h, and the crude formaldehyde copolymer was melted at 220°C. The molten resin extruded from the die was formed into a strand, which was impregnated in a cooling water tank and then fed to a granulator for granulation. The resulting granules were dried in a hot air dryer at 120°C for 12 hours to produce the final sample.

[0090] For Examples 1-9 and Comparative Examples 1-6, the proportions of each component, the manufacturing method of the resin composition, the mixing time and mixing temperature, as well as the evaluation results of formaldehyde production, hot water extraction, and mold deposit (MD) are shown in Tables 1 and 2 below.

[0091] Table 1 Table 2 As shown above, it is evident that by using the manufacturing method of the polyacetal resin of the present invention, it is possible to manufacture a polyacetal resin composition that reduces formaldehyde production and mold deposits. According to the method of the present invention, not only is the operating environment improved, but the amount of formaldehyde produced by the polyacetal resin composition and the molded articles using the composition is reduced, mold deposits are also reduced, and thus molding processability is improved. Therefore, it can be used as a countermeasure against so-called sick building syndrome and is applicable to automotive interior parts, interior parts of houses (such as hot and cold water mixing faucets), clothing parts (such as zippers and belt buckles), or building material applications (such as pipes and pump parts), and mechanical parts (such as gears).

[0092] Explanation of reference numerals in the attached figures G: Gate; P: Tip; h1: Width; h2: Length (the distance from the gate G to the portion of width h1); h3: Length (total length).

Claims

1. A method for manufacturing a polyacetal resin composition, characterized in that: The polyacetal resin composition contains 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea. The method includes a compounding step of mixing ethylene urea into polyacetal resin. In the mixing process, the heating and melting mixing time for mixing ethylene urea into polyacetal resin is 10 to 60 minutes, and the heating and melting mixing temperature is 220°C to 240°C.

2. The method for manufacturing a polyacetal resin composition as described in claim 1, characterized in that: In the polyacetal resin composition, the amount of ethylene urea extracted by hot water extraction at 120°C for 3 hours after freezing and pulverizing the polyacetal resin composition is less than 0.10% by mass relative to the total amount of the polyacetal resin composition.

3. The method for manufacturing a polyacetal resin composition as described in claim 1 or 2, characterized in that: The formaldehyde emission of the polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

4. A polyacetal resin composition manufactured using the method of any one of claims 1 to 3.

5. A polyacetal resin composition, characterized in that: It contains 100 parts by weight of polyacetal resin and 0.2 to 0.5 parts by weight of ethylene urea. After the polyacetal resin composition is frozen and pulverized, the amount of ethylene urea extracted by hot water extraction at 120°C for 3 hours is less than 0.10% by mass relative to the total amount of the polyacetal resin composition.

6. The polyacetal resin composition according to claim 5, characterized in that: The formaldehyde emission of the polyacetal resin composition, as measured according to the German Association of the Automotive Industry standard VDA275, is less than 3 ppm.

7. The polyacetal resin composition according to claim 5 or 6, characterized in that: The polyacetal resin composition is prepared by incorporating ethylene urea into polyacetal resin, wherein the heating and melting incorporation time for ethylene urea into polyacetal resin is 10 to 60 minutes.

8. The polyacetal resin composition according to any one of claims 5 to 7, characterized in that: The polyacetal resin composition is prepared by incorporating ethylene urea into polyacetal resin, wherein the heating and melting temperature for incorporating ethylene urea into polyacetal resin is 220°C to 240°C.

9. A granule formed from the polyacetal resin composition according to any one of claims 4 to 8.

10. A molded article formed from the polyacetal resin composition according to any one of claims 4 to 8.

11. A vehicle component formed from the polyacetal resin composition according to any one of claims 4 to 8.

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