Polyformaldehyde composition, polyformaldehyde material and preparation method of polyformaldehyde material

Abstract

The invention provides a polyformaldehyde composition, a polyformaldehyde material and a preparation method of the polyformaldehyde material. The polyformaldehyde composition comprises polyformaldehyde resin, an ultraviolet light absorber, a light stabilizer, a matte modifier and optional auxiliaries, wherein the matte modifier is a terpolymer and comprises a first monomer, a second monomer and a third monomer, the first monomer is a styrene compound, and the styrene compound comprises at least one of styrene, 1-methylstyrene, 2-methylstyrene and 3-methylstyrene; the second monomer is at least one of maleimide, N-phenylmaleimide and N-(4-acetylphenyl) maleimide, and the third monomer is divinyl benzene; the molar ratio of the first monomer to the second monomer to the third monomer is (70-95): (30-5): 1. The polyformaldehyde material prepared from the polyformaldehyde composition not only has a matte effect on the surface, but also has higher weather resistance and heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of polyoxymethylene materials, and in particular to a polyoxymethylene composition, a polyoxymethylene material and a preparation method thereof. Background Art

[0002] Polyoxymethylene, also known as polyoxymethylene, is a thermoplastic engineering plastic with excellent mechanical properties. It is widely used in the electrical, electronic, automotive and construction industries of contemporary society to replace metal materials such as copper, aluminum and zinc. Therefore, it is also called "metal plastic". Copolymer polyoxymethylene is copolymerized by trioxymethylene and a small amount of dioxopentacyclic. However, polyoxymethylene is mostly used outdoors. Under long-term ultraviolet radiation, the carbon-oxygen bonds of polyoxymethylene become active, resulting in the degradation of the polyoxymethylene molecular chain, which seriously affects its performance. The surface gloss of polymer products is related to the molecular structure and crystallinity of the polymer. Generally speaking, the gloss is high at 75-90°, flat at 50-75°, and sub-gloss at 30-50°. Due to the high crystallinity of polyoxymethylene, the common polyoxymethylene products on the market have a smooth surface and high gloss, and their gloss can reach 85°. The common method for preparing matte or matte polymer materials is to add particles of a certain size to the polymer material. In this way, during the processing of the product, the particles will form a tiny uneven surface on the surface of the product, and visible light will scatter on this surface, thereby reducing the surface gloss of the product. Common additives that reduce the gloss of polymers are mostly inorganic compounds, such as calcium carbonate, talc, silicon dioxide, aluminum oxide, magnesium hydroxide, etc., but these compounds have poor compatibility with polymers and have aggregated in the resin.

[0003] To solve the above problems, the present invention has invented a polyoxymethylene composition, a polyoxymethylene material and a preparation method thereof through a large amount of research work. The polyoxymethylene composition provided in the present invention not only has excellent weather resistance, but also has matte performance, and can significantly improve the heat deformation temperature of polyoxymethylene. Summary of the invention

[0004] The main purpose of the present invention is to provide a polyformaldehyde composition, a polyformaldehyde material and a preparation method thereof, so as to solve the problems of poor weather resistance, high gloss and poor heat resistance of common polyformaldehyde products on the market. Although the glossiness of the surface of the polyformaldehyde products can be reduced by adding inorganic substances into the products, the inorganic substances have poor compatibility with polyformaldehyde and are prone to agglomeration, which cannot meet the requirements of weather resistance, matteness and heat resistance of the polyformaldehyde products.

[0005] To achieve the above object, according to one aspect of the present invention, a polyoxymethylene composition is provided, comprising the following components in parts by weight: 100 parts of polyoxymethylene resin, 0.10-1.0 parts of ultraviolet absorber, 0.10-1.0 parts of light stabilizer, 5.0-10.0 parts of matte modifier and 0.01-5.0 parts of optional auxiliary agent; wherein the matte modifier is a terpolymer, which comprises a first monomer, a second monomer and a third monomer, the first monomer is a styrene compound, and the styrene compound comprises at least one of styrene, 1-methylstyrene, 2-methylstyrene and 3-methylstyrene; the second monomer is at least one of maleimide, N-phenylmaleimide and N-(4-acetylphenyl)maleimide, and the third monomer is divinylbenzene; the molar ratio of the first monomer, the second monomer and the third monomer is (70-95):(30-5):1.

[0006] Furthermore, the matte modifier is at least one of styrene-N-phenylmaleimide-divinylbenzene terpolymer, 1-methylstyrene-N-phenylmaleimide-divinylbenzene terpolymer, 2-methylstyrene-N-phenylmaleimide-divinylbenzene copolymer, 3-methylstyrene-maleimide-divinylbenzene terpolymer, and 3-methylstyrene-N-(4-acetylphenyl)maleimide-divinylbenzene.

[0007] Furthermore, the matte modifier is in granular form, and the particle size of the matte modifier is 5-75 μm.

[0008] Furthermore, the polyoxymethylene resin is a copolymer polyoxymethylene resin, and the copolymer polyoxymethylene resin is a copolymer of trioxymethylene and dioxolane. Furthermore, the weight content of dioxolane is 1.5-5.0%.

[0009] Furthermore, the melt index of the polyoxymethylene resin is 2.5-45 g / 10 min.

[0010] Furthermore, the content of unstable terminal groups in the polyoxymethylene resin is not more than 9000 mg / kg, and further, the content of unstable terminal groups in the polyoxymethylene resin is 1000-4000 mg / kg.

[0011] Further, the ultraviolet absorber is at least one of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, and 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole;

[0012] Furthermore, the light stabilizer is at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}, and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester.

[0013] Furthermore, the auxiliary agent includes at least one of a first formaldehyde absorbent, a second formaldehyde absorbent, a lubricant, and a composite antioxidant.

[0014] Furthermore, in parts by weight, the auxiliary agent includes 0.02-1.0 parts of a first formaldehyde absorbent, 0.02-1.0 parts of a second formaldehyde absorbent, 0.05-1.0 parts of a lubricant, and 0.20-1.0 parts of a composite antioxidant.

[0015] Furthermore, the first formaldehyde absorbent is melamine.

[0016] Furthermore, the second formaldehyde absorbent is a melamine derivative containing a benzene substituent, and further, the melamine derivative containing a benzene substituent includes at least one of benzoguanamine, 1-methylbenzoguanamine, 2-methylbenzoguanamine, 1,2-dimethylbenzoguanamine, 1,4-dimethylbenzoguanamine, and 2,3-dimethylbenzoguanamine.

[0017] Furthermore, the lubricant is selected from at least one of N,N-ethylene bisstearamide and glyceryl monostearate.

[0018] Further, the composite antioxidant is selected from triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine [(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)] pentaerythritol diphosphite / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / dioctadecyl pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis- (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxyphenyl) propionate At least one of β-(3-tert-butyl-4-hydroxyphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite.

[0019] Furthermore, the weight ratio of the three components in the composite antioxidant is (1-2):1:(0.5-2).

[0020] According to a second aspect of the present invention, a polyoxymethylene material is provided, wherein the raw material of the polyoxymethylene material is the polyoxymethylene composition provided in the first aspect.

[0021] According to a third aspect of the present invention, there is provided a method for preparing a polyformaldehyde material, comprising the following steps: S1, mixing components of a polyformaldehyde composition comprising a polyformaldehyde resin, an ultraviolet absorber, a light stabilizer, a matte modifier and optional auxiliary agents to obtain a mixture; S2, melt-granulating the mixture to obtain a polyformaldehyde material.

[0022] Furthermore, a twin-screw extruder is used for melt granulation, the temperature of the twin-screw extruder is 170-245° C., and the speed of the screw on the twin-screw extruder is 20-600 r / min.

[0023] Furthermore, the length-to-diameter ratio of the twin-screw extruder is 25-70:1.

[0024] Furthermore, the vacuum degree of each exhaust section in the twin-screw extruder is not greater than -0.07 MPa.

[0025] By applying the technical solution of the present application, the polyoxymethylene composition provided by the present application adds a terpolymer formed by copolymerization of a first monomer, a second monomer and a third monomer, all of which are organic monomers, as a matte modifier. By using the principle of similar compatibility, the matte modifier has good compatibility with the polyoxymethylene resin, thereby enabling it to be evenly dispersed during the preparation of the polyoxymethylene material, thereby effectively improving the matte performance of the polyoxymethylene material. In addition, the matte modifier used in the present application selects at least one of maleimide, N-phenylmaleimide, and N-(4-acetylphenyl)maleimide) as the second monomer, which, on the one hand, helps to improve the absorption performance of formaldehyde and a small amount of formic acid generated by degradation in the polyoxymethylene resin, and on the other hand, can improve the heat resistance of the polyoxymethylene material.

[0026] In addition, the ultraviolet absorber, light stabilizer, matte modifier and polyformaldehyde resin in the polyformaldehyde composition provided by the present application work together, not only slowing down the photodegradation process and effectively absorbing ultraviolet light, reducing the aging rate of the polyformaldehyde material, but also utilizing the compatibility of the matte modifier with the polyformaldehyde material to reduce the surface gloss of the polyformaldehyde material, achieving a matte effect with a gloss of 30-50°, thereby greatly improving the weather resistance and heat resistance of the polyformaldehyde material formed by the polyformaldehyde composition.

[0027] The polyoxymethylene material provided by the present application, under the combined action of the ultraviolet absorber, the light stabilizer, and the matte modifier, not only improves the weather resistance of the polyoxymethylene material, but also makes it matte and has a higher thermal deformation temperature. After aging, the molecular weight of the polyoxymethylene material reaches at least 77% of that before aging, the weather resistance of the polyoxymethylene material is greatly improved, the surface is matte, and the thermal deformation temperature is higher than 110°C, which broadens the scope of use of polyoxymethylene composite materials, especially the use of outdoor materials. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0029] As analyzed in the background technology of this application, commercially available polyformaldehyde products have the problems of poor weather resistance, high gloss and poor heat resistance. Although the addition of inorganic compounds can reduce the glossiness of polyformaldehyde materials, inorganic compounds have poor biocompatibility with polyformaldehyde materials and are prone to agglomeration, and cannot meet the matte requirements. In order to solve this problem, this application provides a polyformaldehyde composition, a polyformaldehyde material and a preparation method thereof.

[0030] In a typical embodiment of the present application, a polyoxymethylene composition is provided, comprising the following raw materials in parts by weight: 100 parts of polyoxymethylene resin, 0.10-1.0 parts of ultraviolet absorber, 0.10-1.0 parts of light stabilizer, 5.0-10.0 parts of matte modifier and 0.01-5.0 parts of optional auxiliary agent; wherein the matte modifier is a terpolymer, which includes a first monomer, a second monomer and a third monomer, the first monomer is a styrene compound, and the styrene compound includes at least one of styrene, 1-methylstyrene, 2-methylstyrene, and 3-methylstyrene; the second monomer is at least one of maleimide, N-phenylmaleimide, and N-(4-acetylphenyl)maleimide, the third monomer is divinylbenzene, and the molar ratio of the first monomer, the second monomer, and the third monomer is (70-95):(30-5):1.

[0031] By applying the technical solution of the present application, the polyoxymethylene composition provided by the present application adds a terpolymer formed by copolymerization of a first monomer, a second monomer and a third monomer, all of which are organic monomers, as a matte modifier. By using the principle of similar compatibility, the matte modifier has good compatibility with the polyoxymethylene resin, thereby enabling it to be evenly dispersed during the preparation of the polyoxymethylene material, thereby effectively improving the matte performance of the polyoxymethylene material. In addition, the matte modifier used in the present application selects at least one of maleimide, N-phenylmaleimide, and N-(4-acetylphenyl)maleimide) as the second monomer, which, on the one hand, helps to improve the absorption performance of formaldehyde and a small amount of formic acid generated by degradation in the polyoxymethylene resin, and on the other hand, can improve the heat resistance of the polyoxymethylene material.

[0032] In addition, the ultraviolet absorber, light stabilizer, matte modifier and polyformaldehyde resin in the polyformaldehyde composition provided by the present application work together, not only slowing down the photodegradation process and effectively absorbing ultraviolet light, reducing the aging rate of the polyformaldehyde material, but also utilizing the compatibility of the matte modifier with the polyformaldehyde material to reduce the surface gloss of the polyformaldehyde material, achieving a matte effect with a gloss of 30-50°, thereby greatly improving the weather resistance and heat resistance of the polyformaldehyde material formed by the polyformaldehyde composition.

[0033] The polyoxymethylene material provided by the present application, under the combined action of the ultraviolet absorber, the light stabilizer, and the matte modifier, not only improves the weather resistance of the polyoxymethylene material, but also makes it matte and has a higher thermal deformation temperature. After aging, the molecular weight of the polyoxymethylene material reaches at least 77% of that before aging, the weather resistance of the polyoxymethylene material is greatly improved, the surface is matte, and the thermal deformation temperature is higher than 110°C, which broadens the scope of use of polyoxymethylene composite materials, especially the use of outdoor materials.

[0034] Typically but not limiting, in the polyoxymethylene composition provided in the present application, based on 100 parts by weight of the polyoxymethylene resin, the amount of the ultraviolet absorber is 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1.0 part or a range of any two values; the amount of the light stabilizer is 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1.0 part or a range of any two values. 0 parts or a range consisting of any two numerical values; the amount of the matte modifier is 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, 8.0 parts, 8.5 parts, 9.0 parts, 10.0 parts or a range consisting of any two numerical values; the amount of the auxiliary agent is 0.01 parts, 0.02 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.5 parts, 1.0 parts, 2.0 parts, 3.0 parts, 5.0 parts or a range consisting of any two numerical values.

[0035] Typically but not limitatively, in the matte modifier provided in the present application, the molar ratio of the first monomer, the second monomer, and the third monomer is 70:30:1, 75:25:1, 77.5:22.5:1, 80:20:1, 82.5:17.5:1, 85:15:1, 87.5:12.5:1, 90:10:1, 95:5:1 or a range consisting of any two values.

[0036] Due to the poor compatibility of inorganic compounds with polymers, inorganic compounds are easily agglomerated when added to polyoxymethylene materials, which reduces the matt effect. In order to improve the matt effect, the matt modifier is a terpolymer composed of the above-mentioned first monomer, the second monomer, and the third monomer, and the first monomer, the second monomer, and the third monomer are all organic monomers, so that the matt modifier is an organic matter, and according to the similar compatibility principle, it has excellent compatibility with the polyoxymethylene resin. Therefore, the matt modifier with a specific composition is selected to cooperate with the polyoxymethylene resin and the light stabilizer and the ultraviolet absorber, so that the prepared polyoxymethylene products can present a matt effect and have excellent weather resistance. In addition, by selecting maleimide, N-phenylmaleimide, N-(4-acetylphenyl) maleimide as the second monomer, on the one hand, the absorption performance of formaldehyde and a small amount of formic acid generated by decomposition in the polyoxymethylene resin is improved, and on the other hand, the heat resistance of the polyoxymethylene material is also improved.

[0037] In order to further improve the matte effect and heat resistance of the matte modifier on the surface of the polyformaldehyde material, the matte modifier is preferably any one or more of styrene-N-phenylmaleimide-divinylbenzene terpolymer, 1-methylstyrene-N-phenylmaleimide-divinylbenzene terpolymer, 2-methylstyrene-N-phenylmaleimide-divinylbenzene copolymer, 3-methylstyrene-maleimide-divinylbenzene terpolymer, and 3-methylstyrene-N-(4-acetylphenyl)maleimide-divinylbenzene.

[0038] In order to improve the uniformity of dispersion of the matte modifier in the polyformaldehyde material, the matte modifier is preferably in granular form, and the particle size of the matte modifier is 5-75 μm. The matte modifier particles are easier to mix evenly with other components of the polyformaldehyde composition, so that the polyformaldehyde material prepared from the polyformaldehyde composition has excellent matte properties. Visible light is scattered on the surface of the polyformaldehyde material, thereby reducing the surface gloss and presenting a matte effect.

[0039] Typically but not limiting, the particle size of the matte modifier is 5 μm, 15 μm, 15 μm, 35 μm, 45 μm, 55 μm, 65 μm, 75 μm or a range consisting of any two values.

[0040] In some embodiments, the matte modifier is prepared as follows:

[0041] With the addition of an initiator and a molecular weight regulator, the first monomer, the second monomer and the third monomer are polymerized by heating to generate a matte modifier.

[0042] The above-mentioned initiator is not specifically limited, and any commonly used initiator in the art can be used, such as azo compounds: azobisisobutyronitrile, azobisisoheptanenitrile; organic peroxides: dibenzoyl peroxide, isopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, tert-butyl peroxybenzoate; inorganic peroxides: sodium persulfate, potassium persulfate. The above-mentioned molecular weight regulator is not specifically limited, and any commonly used molecular weight regulator in the art can be used, such as n-dodecyl mercaptan, tert-dodecyl mercaptan.

[0043] In some specific embodiments, the matte modifier is prepared according to the following steps:

[0044] In a 1000ml three-necked flask equipped with a thermometer, nitrogen protection, reflux device and stirring device, the first monomer: styrene 178g (1.71mol), the second monomer: N-phenylmaleimide 32.9g (0.19mol), the third monomer: divinylbenzene 2.5g (0.019mol), the molecular weight regulator: n-dodecyl mercaptan 0.5g, the initiator: azobisisobutyronitrile 0.75g, and deionized water 200g were added, nitrogen was introduced into the three-necked flask, and stirred for 15min to exclude the air in the system, and then reacted at a temperature of 70°C for 30min. After the reaction was completed, 50mL of 1wt% sodium sulfate aqueous solution was added dropwise into the three-necked flask, and the reaction was again carried out at a temperature of 80°C for 1h to obtain a matte modifier with a particle size distribution of 15-35μm.

[0045] It should be noted that the preparation methods of matte modifiers with other monomer compositions and particle size distributions are similar to the above-mentioned preparation process and will not be presented one by one here.

[0046] The polyoxymethylene resin is a commonly used polyoxymethylene resin in the art. To improve the thermal stability and chemical stability of the polyoxymethylene resin, the polyoxymethylene resin is preferably a copolymer polyoxymethylene resin generated by copolymerization of trioxymethylene and dioxolane. To improve the bending modulus and thermal deformation temperature of the copolymer polyoxymethylene resin, the weight content of dioxolane is preferably 1.5-5.0%.

[0047] The melt index of polyoxymethylene resin can be used to indicate flowability. A high melt index indicates high flowability and the polyoxymethylene resin is easier to process. In order to further improve the processing performance of the polyoxymethylene resin, the melt index of the polyoxymethylene resin is preferably 2.5-45 g / 10 min.

[0048] The above melt index is measured according to standard ISO1133 at 190°C and 2.16 kg.

[0049] The molecular chain end of the polyoxymethylene resin contains an unstable terminal group structure of hemiacetal, which is easily decomposed to generate formaldehyde when heated. A high content of unstable terminal groups can easily affect the thermal stability of the polyoxymethylene resin. In order to make the polyoxymethylene resin have good thermal stability, the content of unstable terminal groups in the polyoxymethylene resin is preferably not more than 9000 mg / kg, more preferably 1000-4000 mg / kg.

[0050] In this application, the content of unstable end groups of polyoxymethylene is determined according to the following steps:

[0051] (1) 2 g of a polyoxymethylene resin sample is placed in a sealed round-bottom flask prepared with a gas washing bottle and heated to melt. High-purity nitrogen is used as a carrier gas to purge the molten polyoxymethylene sample in the sealed flask. The purge gas is bubbled into the gas washing bottle filled with 400 mL of deionized water, so that the formaldehyde gas released by the thermal decomposition of the unstable terminal groups in the polyoxymethylene resin sample is completely absorbed by the deionized water. The polyoxymethylene resin sample is heated to 200° C. in the sealed round-bottom flask to completely melt the polyoxymethylene resin and completely decompose the unstable terminal groups into formaldehyde. The heating and melting time is continued for 50 minutes to ensure that the unstable terminal groups in the polyoxymethylene resin have sufficient time to be thermally decomposed.

[0052] (2) The formaldehyde concentration absorbed by the deionized water in the gas washing bottle is accurately measured by the acetylacetone ultraviolet spectrophotometry method, and then converted into the unstable end group content by using the principle that one formaldehyde molecule corresponds to one hemiacetal end group. Among them, the acetylacetone method principle is to use formaldehyde, acetylacetone and ammonia to generate a yellow compound 3,5-diacetyl 1,4-dihydrolutidine, and perform spectrophotometric determination at a wavelength of 412nm.

[0053] Typically but not limitatively, the weight content of dioxolane in the polyoxymethylene resin is 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range consisting of any two values; the melt index of the polyoxymethylene resin is 2.5g / 10min, 9g / 10min, 13g / 10min, 27g / 10min, 45g / 10min or a range consisting of any two values; the content of unstable end groups in the polyoxymethylene resin is 1000mg / kg, 2000mg / kg, 3000mg / kg, 4000mg / kg or a range consisting of any two values.

[0054] Under long-term ultraviolet irradiation, the carbon-oxygen bonds of polyoxymethylene resin become active, which in turn causes the degradation of the molecular chains in the polyoxymethylene resin and accelerates the aging of the polyoxymethylene resin. In order to reduce the aging problem caused by ultraviolet irradiation of polyoxymethylene resin, an ultraviolet absorber is added to the polyoxymethylene composition provided by the present application. In order to further improve the weather resistance of the polyoxymethylene material, the ultraviolet absorber is preferably at least one of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, and 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole.

[0055] Light stabilizers can directly absorb ultraviolet light of 290nm-400nm, first transform from the ground state to the excited state, and then transfer energy, emit weaker fluorescence or phosphorescence, or transform into heat, or transfer energy to other molecules and finally return to the ground state. Light stabilizers are added to the polyoxymethylene composition provided by the present application to slow down the photodegradation of polyoxymethylene resin. At the same time, the light stabilizer is compounded with ultraviolet absorbers and sub-light stabilizers to produce good synergistic effects, which greatly improves the weather resistance of polyoxymethylene materials.

[0056] In order to further improve the weather resistance of the polyoxymethylene material prepared from the polyoxymethylene composition, the light stabilizer is preferably selected from any one or more of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}, and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester.

[0057] In the present application, the specific type of the auxiliary agent is not limited. The auxiliary agent may be added or not added according to different application scenarios of the polyoxymethylene material, and the specific type of the auxiliary agent is selected according to the application scenario.

[0058] In some embodiments, the auxiliary agent in the polyoxymethylene composition includes, but is not limited to, any one or more of a first formaldehyde absorber, a second formaldehyde absorber, a lubricant, and a composite antioxidant.

[0059] In order to further improve the oxidation resistance and thermal stability of the polyformaldehyde material prepared from the polyformaldehyde composition, preferably, based on 100 parts by weight of the polyformaldehyde resin, the amount of the first formaldehyde absorber is 0.02-1.0 part by weight, the amount of the second formaldehyde absorber is 0.02-1.0 part by weight, the amount of the lubricant is 0.05-1.0 part by weight, and the amount of the composite antioxidant is 0.20-1.0 part by weight.

[0060] Under the action of heat and oxygen, the molecular chain of polyoxymethylene resin is easily broken to generate formaldehyde, which is oxidized to generate formic acid. Formaldehyde and formic acid further promote thermal decomposition and accelerate the degradation of polyoxymethylene. In order to reduce the degradation rate of polyoxymethylene, it is preferred to add a variety of different formaldehyde absorbers and composite antioxidants to the polyoxymethylene composition, which can not only absorb the formaldehyde generated by the polyoxymethylene resin at high temperature and inhibit the release of formaldehyde, but also inhibit the chain reaction of oxidative degradation of the polyoxymethylene resin, further improve the thermal stability of the polyoxymethylene resin, and further improve the heat resistance of the prepared polyoxymethylene material.

[0061] The composite antioxidant is a commonly used antioxidant in the art. In order to further improve the thermal stability of the polyoxymethylene material formed by the polyoxymethylene composition, the composite antioxidant is preferably triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5 -methylphenyl) propionate / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / dioctadecyl pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy -5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3 Any one or more of β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / dioctadecyl pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite.

[0062] The above “ / ” means “and”, for example, the above “triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl)hexanediamine / tris(2,4-di-tert-butylphenyl) phosphite” refers to a composite antioxidant composed of three components: triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl)hexanediamine and tris(2,4-di-tert-butylphenyl) phosphite.

[0063] In order to improve the thermal stability of the polyoxymethylene material formed by the polyoxymethylene composition, the weight ratio of the three components in the composite antioxidant is preferably (1-2):1:(0.5-2), such as 1:1:1, 1:1:2 or 2:1:0.5.

[0064] In order to further promote the absorption of formaldehyde released by the breakage of the molecular chain of polyoxymethylene resin, in some embodiments, the first formaldehyde absorbent is preferably melamine; and the second formaldehyde absorbent is preferably a melamine derivative containing a benzene substituent.

[0065] The specific type of the second formaldehyde absorbent is not specifically limited, and any formaldehyde absorbent commonly used in the field of polyoxymethylene materials can be used, including but not limited to melamine derivatives containing benzene substituents, such as benzoguanamine, 1-methylbenzoguanamine, 2-methylbenzoguanamine, 1,2-dimethylbenzoguanamine, 1,4-dimethylbenzoguanamine, 2,3-dimethylbenzoguanamine, etc.

[0066] The specific type of the lubricant is not specifically limited, and any lubricant commonly used in the field of polyoxymethylene materials can be used, including but not limited to any one of N,N-ethylene bisstearamide or glyceryl monostearate or a mixture of both.

[0067] In a second typical embodiment of the present application, a polyoxymethylene material is further provided, and the raw material of the polyoxymethylene material is the polyoxymethylene composition provided in the first typical embodiment.

[0068] In a third typical embodiment of the present application, a method for preparing a polyformaldehyde material is also provided, the preparation method comprising: mixing components of a polyformaldehyde composition including a polyformaldehyde resin, an ultraviolet absorber, a light stabilizer, a matte modifier and optional auxiliary agents to obtain a mixture; and then subjecting the mixture to melt granulation to obtain a polyformaldehyde material.

[0069] The above-mentioned melt granulation is carried out in a melt granulation equipment commonly used in the art, including but not limited to screw extruders, etc. In order to further improve the preparation efficiency of the polyoxymethylene material, it is preferred that the above-mentioned melt granulation is carried out in a twin-screw extruder (multi-stage exhaust twin-screw extruder), especially when the temperature of the twin-screw extruder is 170-245°C, the aspect ratio of the twin-screw extruder is 25-70:1, the speed of the screw is 20-600r / min, and the vacuum degree of each exhaust section is ≤-0.7MPa, the polyoxymethylene resin, ultraviolet absorber, light stabilizer, matte modifier and optional auxiliary agents in the polyoxymethylene material are mixed more evenly, which is more conducive to the preparation of a polyoxymethylene material with excellent performance.

[0070] Typically but not limitatively, the aspect ratio of the twin-screw extruder is 25:1, 30:1, 35:1, 40:1, 50:1, 70:1 or a range consisting of any two values; during melt granulation, the speed of the screw on the twin-screw extruder is 20r / min, 50r / min, 80r / min, 100r / min, 150r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min or a range consisting of any two values.

[0071] The beneficial effects of the present application will be further illustrated below in combination with embodiments and comparative examples.

[0072] Example 1

[0073] The present embodiment provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition. The polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.03 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 1.0 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 6.0 parts of a matte modifier.

[0074] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, with a melt index of 9.0 g / 10 min, a weight content of dioxolane of 1.5%, and an unstable end group content of 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / tris(2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the three components is 1:1:1; the ultraviolet absorber It is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole; the light stabilizer is poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}; the lubricant is N,N-ethylenebisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 85:15:1, and the particle size of the matte modifier is 30μm.

[0075] The polyformaldehyde material is prepared according to the following steps: adding polyformaldehyde resin, a first formaldehyde absorber, a second formaldehyde absorber, a composite antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, and a matte modifier into a mixer and mixing them evenly, and adding them into a twin-screw extruder for melt granulation, wherein the temperature of the twin-screw extruder is 170-245°C, the speed of the screw is 600r / min, the aspect ratio of the twin-screw extruder is 50:1, and the vacuum degree of each exhaust section in the twin-screw extruder is -0.07MPa.

[0076] Example 2

[0077] The present embodiment provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.03 parts of a first formaldehyde absorber, 0.03 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 1.0 parts of a light stabilizer, 0.05 parts of a lubricant, and 5.5 parts of a matte modifier;

[0078] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, with a melt index of 9.0 g / 10 min, a weight content of dioxolane of 1.5%, and an unstable end group content of 1000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / dioctadecyl pentaerythritol diphosphite, and the trioxymethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / dioctadecyl pentaerythritol diphosphite. The weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole; the light stabilizer is poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate; the lubricant is N,N-ethylenebisstearamide / glyceryl monostearate, and the weight ratio of the two components is 1:1; the matte modifier is 2-methylstyrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 70:30:1, and the particle size of the matte modifier is 35μm.

[0079] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0080] Example 3

[0081] The present embodiment provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.03 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 1.0 parts of a lubricant, and 7.5 parts of a matte modifier;

[0082] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is 1,2-dimethylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol ester / bis(2 ,4-di-tert-butylphenol) pentaerythritol diphosphite, and the weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate; the lubricant is N,N-ethylenebisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 90:10:1, and the particle size of the matte modifier is 25μm.

[0083] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0084] Example 4

[0085] The difference between Example 4 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 75:25:1.

[0086] Example 5

[0087] The difference between Example 5 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 95:5:1.

[0088] Example 6

[0089] The difference between Example 6 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 87.5:12.5:1.

[0090] Example 7

[0091] The difference between Example 7 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 77.5:22.5:1.

[0092] Example 8

[0093] The difference between Example 8 and Example 3 is that, by weight, the polyoxymethylene composition comprises 100 parts of polyoxymethylene resin, 0.1 parts of a first formaldehyde absorber, 0.1 parts of a second formaldehyde absorber, 0.5 parts of a composite antioxidant, 0.4 parts of an ultraviolet absorber, 0.4 parts of a light stabilizer, 0.5 parts of a lubricant, and 10 parts of a matte modifier;

[0094] Among them, the polyoxymethylene resin is a trioxymethylene-dioxolane copolymer with a melt index of 45g / 10min, a weight content of dioxolane of 1.5%, and an unstable end group content of 4000mg / kg; the matte modifier is a 3-methylstyrene-maleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 82.5:17.5:1.

[0095] Example 9

[0096] The difference between Example 9 and Example 3 is that, by weight, the polyoxymethylene composition comprises 100 parts of polyoxymethylene resin, 0.7 parts of a first formaldehyde absorber, 0.7 parts of a second formaldehyde absorber, 0.8 parts of a composite antioxidant, 0.8 parts of an ultraviolet absorber, 0.8 parts of a light stabilizer, 0.6 parts of a lubricant, and 5 parts of a matte modifier;

[0097] Among them, the polyoxymethylene resin is a trioxymethylene-dioxolane copolymer with a melt index of 2.5g / 10min, a weight content of dioxolane of 1.5%, and an unstable end group content of 1000mg / kg; the matte modifier is a 3-methylstyrene-N-(4-acetylphenyl)maleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 80:20:1.

[0098] Example 10

[0099] The present embodiment provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 6.5 parts of a matte modifier;

[0100] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0g / 10min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / dioctadecyl pentaerythritol diphosphite, and the weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(4,6-diphenyl-1,3,5-triazine-2 -yl)-5-hexyloxy-phenol; the light stabilizer is N,N"'-1,2-ethanediylbis[N-[3-[[4,6-di[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]amino]propyl]-N,N"-dibutyl-N,N"-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,3,5-triazine-2,4,6-triamine; the lubricant is N,N-ethylenebisstearamide; the matte modifier is a styrene-N-phenylmaleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 85:15:1, and the particle size of the matte modifier is 20μm.

[0101] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0102] Comparative Example 1

[0103] The present comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.03 parts of a first formaldehyde absorber, 0.03 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 1.0 parts of an ultraviolet absorber, 1.0 parts of a light stabilizer, 0.05 parts of a lubricant, and 1.8 parts of a matte modifier;

[0104] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 10.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 2000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, the weight of the three components is 1.5%. The ratio is 1:1:1; the ultraviolet absorber is 2,4-bis[2,2'-bis(5-butoxyphenol)]-6-(2,4-dibutoxybenzene)-1,3,5-triazine; the light stabilizer is 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-[(2-ethylhexyl)oxy]-2-hydroxypropoxyphenol; the lubricant is glyceryl monostearate; the matte modifier is a styrene-N-phenylmaleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 90:10:1, and the particle size of the matte modifier is 20μm.

[0105] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0106] Comparative Example 2

[0107] This comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.05 parts of a lubricant, and 7.0 parts of a matte modifier;

[0108] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol di-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl The weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole; the lubricant is N, N-ethylene bisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 92.5:7.5:1, and the particle size of the matte modifier is 20μm.

[0109] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0110] Comparative Example 3

[0111] This comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.05 parts of a lubricant, and 2.4 parts of a matte modifier;

[0112] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) The weight ratio of the three components of octadecyl propionate / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; the lubricant is N,N-ethylenebisstearamide; the matte modifier is a styrene-maleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 95:5:1, and the particle size of the matte modifier is 30μm.

[0113] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0114] Comparative Example 4

[0115] This comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition. The polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 7.1 parts of a matte modifier.

[0116] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 10.0g / 10min, the weight content of dioxolane is 1.5%, and the unstable end group content is 2000mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate The light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; the lubricant is glyceryl monostearate; the matte modifier is a styrene-maleimide-divinylbenzene terpolymer, and the molar ratio of the three monomers is 87.5:12.5:1, and the particle size of the matte modifier is 30 μm.

[0117] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0118] Comparative Example 5

[0119] This comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition. The polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 1.0 parts of a light stabilizer, 0.05 parts of a lubricant, and 2.6 parts of a matte modifier.

[0120] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 10.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 2000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxy-5-methylphenyl) propionate The invention discloses a light stabilizer comprising poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate and a matte modifier comprising a terpolymer of styrene-maleimide-divinylbenzene and a molar ratio of the three monomers of 77.5:22.5:1. The particle size of the matte modifier is 30 μm.

[0121] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0122] Comparative Example 6

[0123] This comparative example provides a polyoxymethylene material, which is prepared by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorbent, 0.02 parts of a second formaldehyde absorbent, 0.20 parts of a composite antioxidant, and 0.05 parts of a lubricant;

[0124] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is benzoguanamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester / tris(2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the three components is 1:1:1; the lubricant is N,N-ethylene bisstearamide;

[0125] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0126] Comparative Example 7

[0127] The present comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 1.5 parts of a matte modifier;

[0128] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is 1,2-dimethylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis-decylamine Octaalkyl pentaerythritol diphosphite, the weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; the lubricant is N,N-ethylene bisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three components is 87.5:12.5:1, and the particle size of the matte modifier is 10μm.

[0129] The preparation steps of the polyoxymethylene material are the same as those in the embodiment and will not be repeated here.

[0130] Comparative Example 8

[0131] The present comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 1.0 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 2.0 parts of a matte modifier;

[0132] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0g / 10min, the weight content of dioxolane is 5%, and the unstable end group content is 1000mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is 2-methylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester / tris(2,4-di-tert-butylphenyl) phosphite, and the weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2 '-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole; the light stabilizer is poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}; the lubricant is glyceryl monostearate; the matte modifier is 1-methylstyrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 82.5:17.5:1, and the particle size of the matte modifier is 25μm.

[0133] The preparation steps of the polyoxymethylene material are the same as those in Example 1 and will not be repeated here.

[0134] Comparative Example 9

[0135] The present comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 1.0 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 1.5 parts of a matte modifier;

[0136] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is 1-methylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / dioctadecyl quaternary Pentaerythritol diphosphite, the weight ratio of the three components is 1:1:2; the ultraviolet absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole; the light stabilizer is poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate; the lubricant is N,N-ethylene bisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 92.5:7.5:1, and the particle size of the matte modifier is 30μm.

[0137] The preparation steps of the polyoxymethylene material are the same as those in Example 1 and will not be repeated here.

[0138] Comparative Example 10

[0139] The present comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.05 parts of a second formaldehyde absorber, 1.0 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 4.5 parts of a matte modifier;

[0140] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorber is melamine; the second formaldehyde absorber is 2-methylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N, N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite, the weight ratio of the three components is 2:1:0.5; the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate; the lubricant is glyceryl monostearate; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 95:5:1, and the particle size of the matte modifier is 25μm.

[0141] The preparation steps of the polyoxymethylene material are the same as those in Example 1 and will not be repeated here.

[0142] Comparative Example 11

[0143] The comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition. The polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.02 parts of a second formaldehyde absorber, 0.20 parts of a composite antioxidant, 0.10 parts of an ultraviolet absorber, 0.10 parts of a light stabilizer, 0.05 parts of a lubricant, and 3.5 parts of a matte modifier.

[0144] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, with a melt index of 9.0 g / 10 min, a weight content of dioxolane of 1.5%, and an unstable end group content of 1000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is 1,2-dimethylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol ester / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, and the weight ratio of the three components is 1:1:1; UV The light absorber is 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; the light stabilizer is poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}; the lubricant is glyceryl monostearate; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 87.5:12.5:1, and the particle size of the matte modifier is 15μm.

[0145] The preparation steps of the polyoxymethylene material are the same as those in Example 1 and will not be repeated here.

[0146] Comparative Example 12

[0147] The comparative example provides a polyoxymethylene material, which is formed by melt granulation of a polyoxymethylene composition, wherein the polyoxymethylene composition comprises, by weight, 100 parts of a polyoxymethylene resin, 0.02 parts of a first formaldehyde absorber, 0.03 parts of a second formaldehyde absorber, 1.0 parts of a composite antioxidant, 1.0 parts of an ultraviolet absorber, 1.0 parts of a light stabilizer, 1.0 parts of a lubricant, and 0.5 parts of a matte modifier;

[0148] The polyoxymethylene resin is a trioxymethylene-dioxolane copolymer, the melt index is 9.0 g / 10 min, the weight content of dioxolane is 1.5%, and the unstable end group content is 1000 mg / kg; the first formaldehyde absorbent is melamine; the second formaldehyde absorbent is 1,2-dimethylbenzene melamine; the composite antioxidant is triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol ester / bis(2,4-di-tert-butyl-4-hydroxyphenyl) propionate The weight ratio of the three components is 1:1:1; the ultraviolet absorber is 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; the light stabilizer is poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate; the lubricant is N,N-ethylenebisstearamide; the matte modifier is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three monomers is 77.5:22.5:1, and the particle size of the matte modifier is 15μm.

[0149] The preparation steps of the polyoxymethylene material are the same as those in Example 1 and will not be repeated here.

[0150] Comparative Example 13

[0151] The difference between Comparative Example 13 and Example 3 is that the matte modifier in the polyoxymethylene composition is a styrene-N-phenylmaleimide binary copolymer.

[0152] Comparative Example 14

[0153] The difference between Comparative Example 14 and Example 3 is that the matte modifier in the polyoxymethylene composition is a terpolymer of methyl methacrylate-styrene-N-substituted maleimide.

[0154] Comparative Example 15

[0155] The difference between Comparative Example 15 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three components is 60:40:1.

[0156] Comparative Example 16

[0157] The difference between Comparative Example 16 and Example 3 is that the matte modifier in the polyoxymethylene composition is styrene-N-phenylmaleimide-divinylbenzene, and the molar ratio of the three components is 99:1:1.

[0158] Comparative Example 17

[0159] The difference between Comparative Example 17 and Example 3 is that, by weight, the amount of the matte modifier in the polyoxymethylene composition is 13 parts.

[0160] Test Example 1

[0161] The molecular weight of polyformaldehyde before aging, the molecular weight of polyformaldehyde after aging after irradiation with ultraviolet light, the molecular weight retention rate of polyformaldehyde after aging, the thermal deformation temperature and the glossiness of the polyformaldehyde materials provided in the above embodiments and comparative examples were measured respectively, and the results are shown in Table 1 below.

[0162] (1) Thermal deformation temperature determination method: Tested in accordance with national standard GB / T 1634-2004.

[0163] (2) Gloss measurement method: Tested in accordance with national standard GB / T 9754-2007.

[0164] (3) The molecular weight of polyoxymethylene before aging is determined according to the following steps:

[0165] The polyoxymethylene materials provided in the examples and comparative examples of the present application were dissolved in a mixed solvent consisting of 98 g of p-chlorophenol and 2 g of α-pinene, and placed in a 60.0°C (±0.1) water bath. The viscosity average molecular weight of the polyoxymethylene was measured using the classical Ubbelohde viscometer method known in the art.

[0166] (4) The molecular weight of polyoxymethylene after aging is determined according to the following steps:

[0167] First, the polyoxymethylene materials provided in the examples and comparative examples of the present application are placed in an ultraviolet aging test box, the ultraviolet light intensity is 0.74-0.78W, and the ultraviolet lamp is kept at a constant temperature of 50°C for 100 hours; then the aged polyoxymethylene material is dissolved in a mixed solvent consisting of 98g of p-chlorophenol and 2g of α-pinene, and placed in a 60.0°C (±0.1) water bath. The viscosity average molecular weight of the polyoxymethylene is measured using the classic Ubbelohde viscometer method known in the art.

[0168] (4) Polyoxymethylene molecular weight retention after aging:

[0169] It is the ratio of the molecular weight of polyoxymethylene after aging to the molecular weight of polyoxymethylene before aging.

[0170] Table 1

[0171]

[0172]

[0173] According to Examples 1-9, Example 10, and Comparative Example 1, when the types of ultraviolet absorbers and light stabilizers are changed in Example 10 or Comparative Example 1, that is, the ultraviolet light does not use any one or more of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, and 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; the light stabilizer does not use bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, poly-{[6-[(1,1,3, Any one or more of [3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl] [2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexyl-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester, the molecular weight retention rate of polyformaldehyde after aging is significantly reduced, indicating that the type of ultraviolet absorber or light stabilizer is related to weather resistance, and the specific type of ultraviolet absorber or light stabilizer in the present application is beneficial to improving the weather resistance of the polyformaldehyde material.

[0174] According to Examples 1-9 and Comparative Examples 2-3, when no light stabilizer is added in Comparative Examples 2-3, the molecular weight retention rate of polyoxymethylene after aging is significantly reduced, and the weather resistance is significantly reduced, indicating that the addition of light stabilizer can slow down the photodegradation of polyoxymethylene resin and improve the weather resistance of polyoxymethylene materials.

[0175] According to Examples 1-9 and Comparative Examples 4-5, when no ultraviolet absorber is added to Comparative Examples 4-5, the molecular weight retention rate of polyformaldehyde after aging is significantly reduced, and the weather resistance is significantly reduced, indicating that the addition of ultraviolet absorber can effectively inhibit the aging problem caused by ultraviolet irradiation, thereby improving the weather resistance of the polyformaldehyde material.

[0176] According to Examples 1-9 and Comparative Example 6, it can be seen that when no ultraviolet absorber, light stabilizer, or matte modifier is added to Comparative Example 6, the molecular weight retention rate and thermal deformation temperature of the polyformaldehyde after aging are significantly reduced, that is, the weather resistance and heat resistance are significantly reduced, and the surface gloss of the polyformaldehyde material is significantly increased, showing a high-gloss effect, indicating that the ultraviolet absorber, light stabilizer, matte modifier and polyformaldehyde resin work together, not only slowing down the photodegradation process and effectively absorbing ultraviolet light, reducing the aging rate of the polyformaldehyde material, but also utilizing the compatibility of the matte modifier with the polyformaldehyde material to reduce the surface gloss of the polyformaldehyde material to achieve a matte effect, thereby greatly improving the weather resistance and heat resistance of the polyformaldehyde material formed by the polyformaldehyde composition.

[0177] According to Examples 1-9, Comparative Examples 7-12, and Comparative Example 17, when the matte modifier in the polyformaldehyde composition is less than 5.0 parts by weight, or greater than 10.0 parts by weight, the surface gloss of the polyformaldehyde material is significantly increased, showing a flat or high gloss effect, indicating that only an appropriate amount of matte modifier can produce excellent compatibility with the polyformaldehyde resin according to the principle of similar compatibility, thereby making the prepared polyformaldehyde product present a matte effect. When the weight portion of the matte modifier is too small, the matte modifier particles are not enough to form a tiny uneven surface on the surface of the polyformaldehyde material, and therefore are not enough to scatter visible light on the surface, and thus it is difficult to reduce the surface gloss. When the weight portion of the matte modifier is too large, the matte modified particles are difficult to disperse evenly in the polyformaldehyde material, and thus it is difficult to reduce the surface gloss.

[0178] According to Examples 1-9, Comparative Examples 13-14, and Comparative Examples 15-16, when the type, quantity or ratio of the monomers in the matte modifier changes, the surface gloss of the polyformaldehyde material is significantly reduced, indicating that the matte modifier composed of specific monomers and proportions in the present application can have a matte effect on the surface of the polyformaldehyde material, reduce the surface gloss, and present a matte effect.

[0179] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0180] A terpolymer in which the first monomer, the second monomer and the third monomer are all organic monomers is added to the polyformaldehyde composition as a matte modifier. The matte modifier and the polyformaldehyde resin utilize the similar compatibility principle between the two to make them have good compatibility, so that they can be evenly dispersed during the preparation of the polyformaldehyde material, thereby reducing the surface gloss of the polyformaldehyde material and achieving a matte effect with a gloss of 30-50°.

[0181] In addition, the ultraviolet absorber, light stabilizer, matte modifier and polyformaldehyde resin in the polyformaldehyde composition provided in the present application work together, not only reducing the surface gloss of the polyformaldehyde material, but also slowing down the photodegradation process and effectively absorbing ultraviolet light, reducing the aging rate of the polyformaldehyde material, thereby greatly improving the weather resistance and heat resistance of the polyformaldehyde material formed by the polyformaldehyde composition.

[0182] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A polyoxymethylene composition, characterized in that: The invention comprises the following components in parts by weight: 100 parts of polyoxymethylene resin, 0.10-1.0 parts of ultraviolet absorber, 0.10-1.0 parts of light stabilizer, 5.0-10.0 parts of matte modifier and 0.01-5.0 parts of optional auxiliary agent; wherein the matte modifier is a terpolymer, which comprises a first monomer, a second monomer and a third monomer, wherein the first monomer is a styrene compound, and the styrene compound comprises at least one of styrene, 1-methylstyrene, 2-methylstyrene and 3-methylstyrene; the second monomer is at least one of maleimide, N-phenylmaleimide and N-(4-acetylphenyl)maleimide, and the third monomer is divinylbenzene; the molar ratio of the first monomer, the second monomer and the third monomer is (70-95):(30-5):

1.

2. The polyoxymethylene composition according to claim 1, characterized in that The matte modifier is at least one of styrene-N-phenylmaleimide-divinylbenzene terpolymer, 1-methylstyrene-N-phenylmaleimide-divinylbenzene terpolymer, 2-methylstyrene-N-phenylmaleimide-divinylbenzene copolymer, 3-methylstyrene-maleimide-divinylbenzene terpolymer, and 3-methylstyrene-N-(4-acetylphenyl)maleimide-divinylbenzene.

3. The polyoxymethylene composition according to claim 1, characterized in that The matte modifier is in granular form, and the particle size of the matte modifier is 5-75 μm.

4. The polyoxymethylene composition according to claim 1, characterized in that The polyoxymethylene resin is a copolymer polyoxymethylene resin, and the copolymer polyoxymethylene resin is a copolymer of trioxymethylene and dioxolane, and preferably the weight content of the dioxolane is 1.5-5.0%; The melt index of the polyoxymethylene resin is 2.5-45 g / 10 min, the content of unstable end groups in the polyoxymethylene resin is not more than 9000 mg / kg, and preferably the content of unstable end groups in the polyoxymethylene resin is 1000-4000 mg / kg.

5. The polyoxymethylene composition according to claim 1, characterized in that: The ultraviolet absorber is at least one of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, and 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole; And / or, the light stabilizer is at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]}, and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) ester.

6. The polyoxymethylene composition according to claim 1, characterized in that The auxiliary agent includes at least one of a first formaldehyde absorbent, a second formaldehyde absorbent, a lubricant, and a composite antioxidant; Preferably, in parts by weight, the auxiliary agent includes 0.02-1.0 part of the first formaldehyde absorbent, 0.02-1.0 part of the second formaldehyde absorbent, 0.05-1.0 part of the lubricant, and 0.20-1.0 part of the composite antioxidant.

7. The polyoxymethylene composition according to claim 6, characterized in that: The first formaldehyde absorbent is melamine; And / or, the second formaldehyde absorbent is a melamine derivative containing a benzene substituent, preferably the melamine derivative containing a benzene substituent includes at least one of benzoguanamine, 1-methylbenzoguanamine, 2-methylbenzoguanamine, 1,2-dimethylbenzoguanamine, 1,4-dimethylbenzoguanamine and 2,3-dimethylbenzoguanamine; And / or, the lubricant is selected from at least one of N,N-ethylene bisstearamide and glyceryl monostearate.

8. The polyoxymethylene composition according to claim 6, characterized in that The composite antioxidant is selected from triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) [Propionic acid] Pentaerythritol ester / Tris(2,4-di-tert-butylphenyl) phosphite, Triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / dioctadecyl pentaerythritol diphosphite, Triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / N,N-bis-( 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol / tris(2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxyphenyl) propionate At least one of β-(3-tert-butyl-4-hydroxyphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / dioctadecyl pentaerythritol diphosphite, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate / β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate / bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite; Preferably, the weight ratio of the three components in the composite antioxidant is (1-2):1:(0.5-2).

9. A polyoxymethylene material, characterized in that: The raw material of the polyoxymethylene material is the polyoxymethylene composition according to any one of claims 1 to 8.

10. The method for preparing the polyoxymethylene material according to claim 9, characterized in that: The preparation method comprises the following steps: S1, mixing the components of the polyoxymethylene composition including the polyoxymethylene resin, the ultraviolet absorber, the light stabilizer, the matte modifier and the optional auxiliary agent to obtain a mixture; S2, melt-granulating the mixture to obtain the polyoxymethylene material; Preferably, a twin-screw extruder is used for the melt granulation, the temperature of the twin-screw extruder is 170-245° C., and the speed of the screw on the twin-screw extruder is 20-600 r / min; Preferably, the aspect ratio of the twin-screw extruder is 25-70:1; Preferably, the vacuum degree of each exhaust section in the twin-screw extruder is not greater than -0.07 MPa.

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