Polyformaldehyde composition as well as preparation method and application thereof

Abstract

The invention discloses a polyformaldehyde composition as well as a preparation method and application thereof. The polyformaldehyde composition is prepared from the following components in parts by weight: 100 parts of polyformaldehyde resin, 5 to 15 parts of thermoplastic polyurethane elastomer, 10 to 20 parts of methyl methacrylate-butadiene-styrene copolymer, 0.1 to 0.5 part of antioxidant and 0.1 to 0.8 part of formaldehyde absorbent, the average particle size of the methyl methacrylate-butadiene-styrene copolymer is less than or equal to 280 nm; the antioxidant is a thioester antioxidant; the polyformaldehyde resin is copolymerized polyformaldehyde resin; the melt flow rate of the polyformaldehyde resin under the conditions of 190 DEG C and 2.16 kg is 2.5-9 g / 10 min. The prepared polyformaldehyde composition also has low formaldehyde release and baking discoloration resistance on the premise of keeping excellent low-temperature mechanical properties.

Description

Technical Field

[0001] This invention belongs to the technical field of engineering plastics, and more specifically, relates to a polyoxymethylene composition, its preparation method, and its application. Background Technology

[0002] Polyoxymethylene (POM), as an engineering plastic with excellent comprehensive performance, possesses superior wear resistance and self-lubricating properties, making it widely used in automotive products such as door handles and dashboards. However, due to its high crystallinity, POM has relatively low notched impact strength, especially at low temperatures. Even after toughening with conventional toughening agents, its low-temperature performance still fails to meet requirements in some applications. Furthermore, the confined space of a car must comply with volatile organic compound (VOC) standards to avoid excessive formaldehyde levels that could harm health; and in summer, the interior temperature of a car can reach 70-90°C, requiring materials to withstand long-term high temperatures without yellowing or releasing odors. Therefore, providing a POM composition with low formaldehyde release, resistance to baking discoloration, and good low-temperature toughness has become a pressing technical problem to be solved. Summary of the Invention

[0003] In view of the above-mentioned existing technical problems, the primary objective of the present invention is to provide a polyoxymethylene composition that has low formaldehyde release and good resistance to baking discoloration; at the same time, it can maintain excellent low-temperature mechanical properties.

[0004] A second objective of this invention is to provide a method for preparing a polyoxymethylene composition.

[0005] A third objective of this invention is to provide an application of a polyoxymethylene composition in the fields of automotive interior and exterior trim and photovoltaics.

[0006] The fourth object of the present invention is to provide an injection molded part.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention claims protection for a polyoxymethylene composition, comprising, by weight, the following components: 100 parts polyoxymethylene resin, 5-15 parts thermoplastic polyurethane elastomer, 10-20 parts methyl methacrylate-butadiene-styrene copolymer, 0.1-0.5 parts antioxidant, and 0.1-0.8 parts formaldehyde absorbent. The antioxidant is a thioester antioxidant; The polyoxymethylene resin is a copolymerized polyoxymethylene resin; the melt flow rate of the polyoxymethylene resin at 190°C and 2.16 kg is 2.5-9 g / 10 min. The average particle size of the methyl methacrylate-butadiene-styrene copolymer is ≤280nm.

[0008] The thermoplastic polyurethane elastomer and the methyl methacrylate-butadiene-styrene copolymer are matched in the present application, so that the low-temperature mechanical properties of the polyformaldehyde composition are improved. The average particle size of the methyl methacrylate-butadiene-styrene copolymer affects its uniform dispersion in the polyformaldehyde matrix. When the particle size of the methyl methacrylate-butadiene-styrene copolymer is small, more stress concentration points are formed, energy is absorbed without causing macroscopic cracks, and the low-temperature toughness of the polyformaldehyde system is improved. Uniform dispersion also reduces the formation of local overheating spots, thereby improving the discoloration resistance of the polyformaldehyde system. In addition, the small particle size of the methyl methacrylate-butadiene-styrene copolymer also increases the contact area with the polyformaldehyde system, which helps to quickly annihilate free radicals at the interface, reduces the thermal oxidative cracking of formaldehyde, and thus reduces the release of formaldehyde.

[0009] Further, compared with other types of antioxidants, the thioester antioxidant can effectively reduce the molecular chain rupture of polyformaldehyde under high-temperature baking, reduce the release of formaldehyde gas, and thus inhibit the yellowing and degradation of the material. The thioester antioxidant also helps to maintain the integrity of the polyformaldehyde molecular chain by inhibiting the degradation of polyformaldehyde, thereby maintaining the mechanical properties of the polyformaldehyde composition at low temperatures.

[0010] By limiting the average particle size of the methyl methacrylate-butadiene-styrene copolymer, matching the thermoplastic polyurethane elastomer, the thioester antioxidant, and the copolymer polyformaldehyde with a specific melt flow rate, and combining with other components in the system, the prepared polyformaldehyde composition has excellent low-temperature mechanical properties, low formaldehyde release, and excellent discoloration resistance under the premise of maintaining excellent low-temperature mechanical properties.

[0011] Specifically, the polyformaldehyde resin accounts for not less than 73.3% of the mass percentage of the polyformaldehyde composition.

[0012] Specifically, the thermoplastic polyurethane elastomer accounts for 3.9-11.9% of the mass percentage of the polyformaldehyde composition. Specifically, the methyl methacrylate-butadiene-styrene copolymer accounts for 7.9-16.0% of the mass percentage of the polyformaldehyde composition. Specifically, the sum of the thermoplastic polyurethane elastomer and the methyl methacrylate-butadiene-styrene copolymer accounts for 17.1-20.0% of the mass percentage of the polyformaldehyde composition.

[0013] Specifically, the thermoplastic polyurethane elastomer can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, etc., or an interval range formed by any of the above values, and the application is not limited to this. Specifically, the methyl methacrylate-butadiene-styrene copolymer can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, etc., or an interval range formed by any of the above values, and the application is not limited to this. Specifically, the antioxidant can be 0.2 parts, 0.3 parts, 0.4 parts, etc., or an interval range formed by any of the above values, and the application is not limited to this. Specifically, the formaldehyde absorber can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, etc., or an interval range formed by any of the above values, and the application is not limited to this.

[0014] Preferably, the methyl methacrylate-butadiene-styrene copolymer has a core-shell structure, with polybutadiene as the core and methyl methacrylate-styrene copolymer as the shell. Among them, the rubber particles refer to the inner core polybutadiene.

[0015] Preferably, the mass content of the rubber particles in the methyl methacrylate-butadiene-styrene copolymer is 60-85%. Further preferably, the mass content of the rubber particles is 60-80%. More preferably, the mass content of the rubber particles is 70-80%. More preferably, the mass content of the rubber particles is 75-80%. Preferably, the polyformaldehyde composition prepared has more excellent mechanical properties, lower formaldehyde release, and more excellent resistance to baking discoloration.

[0016] Specifically, the mass content of the rubber particles in the methyl methacrylate-butadiene-styrene copolymer can be 62%, 64%, 66%, 68%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 81%, 83%, etc., or an interval range formed by any of the above values, and the application is not limited to this. Specifically, the test method for the mass content of the rubber particles in the methyl methacrylate-butadiene-styrene copolymer is: analysis by GC-MS, cracking the material at high temperature, quantitative analysis of the butadiene component in the cracking fragments, and then obtaining the mass content of the rubber particles.

[0017] Preferably, the average particle size of the methyl methacrylate-butadiene-styrene copolymer is ≤ 250 nm; further preferably, the average particle size is 100-250 nm; more preferably, the average particle size is 130-200 nm; more preferably, the average particle size is 150-180 nm. Specifically, the average particle size of the methyl methacrylate-butadiene-styrene copolymer can be 10 nm, 30 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 180 nm, 200 nm, 220 nm, 240 nm, or an interval range formed by any of the above values, and the present application is not limited thereto. Specifically, the test method of the average particle size of the methyl methacrylate-butadiene-styrene copolymer can be: using a transmission electron microscope to measure, the observation magnification is 10,000 times, at least 50 particles per photo, 10 photos are taken for statistics, the average value of all particles in the photos is counted by statistical software to obtain the average particle size.

[0018] Specifically, the melt flow rate of the polyformaldehyde resin at 190°C, 2.16 kg can be 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, or an interval range formed by any of the above values, and the present application is not limited thereto. Specifically, the test method of the melt flow rate of the polyformaldehyde resin is: ISO 1133-2011.

[0019] Preferably, the thioester antioxidant is at least one selected from pentaerythritol tetra(3-dodecylthiopropionate), distearyl thiodipropionate, dilauryl thiodipropionate, ditridecyl thiodipropionate, didodecanol thiodipropionate.

[0020] Preferably, the mass ratio of the thermoplastic polyurethane elastomer and the methyl methacrylate-butadiene-styrene copolymer is 1: (1.5-5).

[0021] Preferably, the thermoplastic polyurethane elastomer is at least one of an aliphatic thermoplastic polyurethane elastomer and an aromatic thermoplastic polyurethane elastomer.

[0022] More specifically, the polyol in the thermoplastic polyurethane elastomer can be a polyester polyol or a polyether polyol; more specifically, the polyether polyol includes but is not limited to polyether glycol, polyether triol, polypropylene oxide glycol, polypropylene oxide triol, polytetrahydrofuran ether glycol, etc. More specifically, the hardness of the thermoplastic polyurethane elastomer is 80-90A.

[0023] Preferably, the formaldehyde absorbent is at least one selected from allantoin, dicyandiamide, and alkyl diacid dihydrazide.

[0024] Preferably, the polyformaldehyde composition further comprises a lubricant.

[0025] Preferably, the lubricant is at least one of stearic acid lubricant or amide lubricant. The lubricant includes but is not limited to at least one of calcium stearate, zinc stearate, glyceryl stearate, bis-ethylenestearoamide, oleamide, erucamide.

[0026] Specifically, the polyformaldehyde composition comprises 0-1 parts by weight of the lubricant. Specifically, the polyformaldehyde composition comprises 0.2-1 parts by weight of the lubricant.

[0027] Further, the present application claims a preparation method of the polyformaldehyde composition, which uniformly mixes raw materials and then melt extrudes to obtain the polyformaldehyde composition.

[0028] Preferably, the melt extrusion is performed by using a twin-screw extruder, and the length-diameter ratio of the twin-screw extruder is 40-50:1. Preferably, the temperature of the melt extrusion is 150-200℃.

[0029] Further, the present application claims an application of the polyformaldehyde composition in the field of automotive interior and exterior decoration and photovoltaic.

[0030] Further, the present application claims an injection molded part, which is prepared by using the polyformaldehyde composition.

[0031] Compared with the prior art, the present application has the following beneficial effects: The present application limits the average particle size of the methyl methacrylate-butadiene-styrene copolymer, matches the thermoplastic polyurethane elastomer, the thioester antioxidant and the copolymer polyformaldehyde with a specific melt flow rate, and combines other components in the system, so that the prepared polyformaldehyde composition has low formaldehyde release and excellent resistance to baking discoloration on the premise of maintaining excellent low-temperature mechanical properties. DETAILED DESCRIPTION

[0032] The present application is further illustrated below in combination with the specification and specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0033] Polyformaldehyde resin 1, copolymer polyformaldehyde, melt flow rate under the condition of 190℃, 2.16kg is 2.5g / 10min, M25-44, Nantong Dabaoli.

[0034] Polyformaldehyde resin 2, copolymer polyformaldehyde, melt flow rate under the condition of 190℃, 2.16kg is 9g / 10min, M90-44, Nantong Dabaoli.

[0035] Polyformaldehyde resin 3, copolymer polyformaldehyde, melt flow rate at 190℃, 2.16kg condition is 27g / 10min, M270-44, Nantong Dabao.

[0036] Polyformaldehyde resin 4, homopolymer polyformaldehyde, melt flow rate at 190℃, 2.16kg condition is 2.5g / 10min, POM 3010, Japan Asahi Kasei.

[0037] Toughening agent 1, methyl methacrylate-butadiene-styrene copolymer, the mass content of rubber particles is 75%, the average particle size of copolymer is 150nm, M-910, Japan Zhongyuan.

[0038] Toughening agent 2, methyl methacrylate-butadiene-styrene copolymer, the mass content of rubber particles is 80%, the average particle size of copolymer is 150nm, M-732, Japan Zhongyuan.

[0039] Toughening agent 3, methyl methacrylate-butadiene-styrene copolymer, the mass content of rubber particles is 60%, the average particle size of copolymer is 250nm, M-521, Japan Zhongyuan.

[0040] Toughening agent 4, methyl methacrylate-butadiene-styrene copolymer, the mass content of rubber particles is 85%, the average particle size of copolymer is 350nm, EM500, LG, Korea.

[0041] Toughening agent 5, ethylene-methyl acrylate-glycidyl methacrylate, AX 8900, Arkema.

[0042] Thermoplastic polyurethane elastomer 1, 9180AP, Dongcheng, Korea.

[0043] Thermoplastic polyurethane elastomer 2, HF3080-AST2, Huafeng.

[0044] Antioxidant 1, thioester antioxidant, pentaerythritol tetra(3-dodecylthiopropionate), 412S, Tianjin Li'anlong.

[0045] Antioxidant 2, thioester antioxidant, didodecylthiodipropionate, RIANOX DSTDP, Li'anlong.

[0046] Antioxidant 3, phosphite antioxidant, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, PEP-36, Japan Aideluo.

[0047] Antioxidant 4, phosphite antioxidant, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, SONOX 626, Linyi Sanfeng Chemical, Tianjin Li'anlong.

[0048] Formaldehyde absorbent, allantoin, Ningbo Yongning Chemical.

[0049] Lubricant, bis(ethylene) stearamide, commercially available.

[0050] Unless otherwise specified, all components (such as formaldehyde absorbent and lubricant) used in the parallel examples and comparative examples are the same commercially available products.

[0051] Examples 1-8 A polyoxymethylene composition is prepared according to the formula weight parts in Table 1 and the preparation method including the following steps: the raw materials in Table 1 are placed in a high-speed mixer and mixed according to the stated weight parts, and the resulting mixture is added to a twin-screw extruder (length-to-diameter ratio 40:1). The barrel temperatures of the twin-screw extruder from the feed port to the die head are 160℃, 175℃, 180℃, 190℃, 185℃, 185℃, 185℃, 185℃, 185℃, 185℃, 185℃, 185℃, and 185℃, respectively. The screw speed is 250 rpm, the feed rate is 100 kg / h, and the vacuum degree is -0.1 MPa.

[0052] Table 1

[0053] Comparative Examples 1-8 The weight proportions of raw materials used in the following comparative examples are shown in Table 2. The preparation method is the same as that in Example 1 above.

[0054] Table 2

[0055] Test case The polyoxymethylene compositions obtained in the above examples and comparative examples were tested, and the specific test methods are shown below.

[0056] (1) Low-temperature simply supported beam notched impact strength test (KJ / m) 2 The ISO standard specimen prepared from the polyoxymethylene composition was placed in a low-temperature chamber (-40℃) for 4 hours and then tested. The test standard refers to ISO 179.

[0057] (2) Low temperature elongation at break (%): The tensile specimens made of polyoxymethylene composition according to ISO standard were placed in a freezer (-40℃) for 4 hours and then tested. The test standard was based on ISO 527 and the tensile speed was 50 mm / min.

[0058] (3) Formaldehyde (mg / kg): After drying the polyoxymethylene composition at 95°C for 5 hours, it was injection molded into a 100*100*1.5mm square plate at 200°C and tested with reference to standard PV3925.

[0059] (4) Low temperature falling ball test: the 100*100*1.5mm square plate after injection molding was placed in a freezer (-35℃) for 4h and then tested (the test should be completed within 30s), a 800g steel ball was dropped freely, and the falling ball height when the sample cracked was recorded.

[0060] (5) Baking discoloration: the 100*100*1.5mm square plate after injection molding was placed in a 110℃ oven for thermal oxidative aging, and the aging time was 400h. The difference in B value before and after aging was tested. The greater the change in B value, the more serious the discoloration.

[0061] The test results are shown in Table 3 below.

[0062] Table 3

[0063] From Table 3 above, it can be seen that the polyformaldehyde composition provided by the present application has excellent low temperature mechanical properties, low formaldehyde release, and low baking discoloration performance. Specifically, the low temperature notched impact strength is ≥12.2KJ / m 2 , the low temperature elongation at break is ≥46%, the low temperature falling ball test is cracked to 1420mm, the formaldehyde release is ≤5.5mg / kg, and the B value change of baking discoloration is ≤5.9.

[0064] From Examples 1-3, it can be seen that when the mass ratio of the thermoplastic polyurethane elastomer and the methyl methacrylate-butadiene-styrene copolymer is 1:1.5-5, the prepared polyformaldehyde composition has more excellent low temperature mechanical properties.

[0065] From Examples 2, Comparative Examples 1 and 2, it can be seen that when the polyformaldehyde resin has a high melt flow rate, or a homopolymer polyformaldehyde is used, the prepared polyformaldehyde composition cannot simultaneously achieve excellent low temperature mechanical properties, low formaldehyde release, and baking discoloration resistance.

[0066] From Examples 2, Comparative Examples 3-4, it can be seen that when the average particle size of the methyl methacrylate-butadiene-styrene copolymer is not within a specific range, or other toughening agents are used, it is difficult to achieve the technical effects of the present application.

[0067] From Examples 2, Comparative Examples 5 and 6, it can be seen that a thioester antioxidant needs to be used to achieve the technical effects of the present application.

[0068] From Examples 2, Comparative Examples 7 and 8, it can be seen that when the methyl methacrylate-butadiene-styrene copolymer is excessive in the system, or the thermoplastic polyurethane elastomer is excessive, the prepared polyformaldehyde composition cannot simultaneously achieve excellent low temperature mechanical properties, low formaldehyde release, and baking discoloration resistance.

[0069] The foregoing examples are illustrative only and are not intended to limit the scope of the methods described herein. The appended claims are intended to claim as broad a range as possible as the inventors can conceive of at the time of filing. The examples presented herein are intended to demonstrate the inventors' knowledge of the present application and are not intended to limit the scope of the claims. Some of the numerical ranges recited in the claims are inclusive of the integers within the defined range. Unless otherwise specified, all ranges include endpoints.

Claims

1. A polyoxymethylene composition, characterized in that, By weight, it includes the following components: 100 parts polyoxymethylene resin, 5-15 parts thermoplastic polyurethane elastomer, 10-20 parts methyl methacrylate-butadiene-styrene copolymer, 0.1-0.5 parts antioxidant, and 0.1-0.8 parts formaldehyde absorbent. The antioxidant is a thioester antioxidant; The polyoxymethylene resin is a copolymerized polyoxymethylene resin; the melt flow rate of the polyoxymethylene resin at 190°C and 2.16 kg is 2.5-9 g / 10 min. The average particle size of the methyl methacrylate-butadiene-styrene copolymer is ≤280nm.

2. The polyoxymethylene composition according to claim 1, characterized in that, The thioester antioxidant is selected from at least one of pentaerythritol tetra(3-dodecylthiopropionate), distearate thiodipropionate, dilauryl thiodipropionate, di(tridecyl) thiodipropionate, and didodecyl thiodipropionate.

3. The polyoxymethylene composition according to claim 1, characterized in that, The mass ratio of the thermoplastic polyurethane elastomer to the methyl methacrylate-butadiene-styrene copolymer is 1:(1.5-5).

4. The polyoxymethylene composition according to claim 1, characterized in that, The thermoplastic polyurethane elastomer is at least one of aliphatic thermoplastic polyurethane elastomer and aromatic thermoplastic polyurethane elastomer.

5. The polyoxymethylene composition according to claim 1, characterized in that, The formaldehyde absorbent is selected from at least one of allantoin, dicyandiamide, and alkyl diacid dihydrazide.

6. The polyoxymethylene composition according to claim 1, characterized in that, The polyoxymethylene composition also includes a lubricant; Preferably, the lubricant is at least one of stearic acid lubricants or amide lubricants.

7. The polyoxymethylene composition according to claim 1, characterized in that, The mass content of rubber particles in the methyl methacrylate-butadiene-styrene copolymer is 60-85%.

8. A method for preparing the polyoxymethylene composition according to any one of claims 1-7, characterized in that, After the raw materials are mixed evenly, they are melt-extruded to prepare the polyoxymethylene composition.

9. The application of the polyoxymethylene composition according to any one of claims 1-7 in the fields of automotive interior and exterior trim and photovoltaics.

10. An injection-molded part, characterized in that, It is prepared by injection molding using the polyoxymethylene composition according to any one of claims 1-7.

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