A polyoxymethylene composition, its preparation method and application

Abstract

The present invention discloses a polyoxymethylene composition, which comprises the following components in parts by weight: 100 parts of a copolymerized polyoxymethylene resin; 0.3 - 1 part of a hydroxybenzophenone ultraviolet light absorber; 1 - 10 parts of polyethylene glycol; the number average molecular weight range of the polyethylene glycol is 800 - 6000. By selecting a specific type of ultraviolet light absorber and polyethylene glycol with a specific molecular weight in the copolymerized polyoxymethylene resin as the resin matrix, the present invention can significantly reduce the odor of the composition and has good ultraviolet resistance effect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a polyoxymethylene composition, a preparation method thereof, and an application thereof. Background Art

[0002] Polyoxymethylene (POM) is a highly crystalline linear thermoplastic polymer, which has excellent mechanical properties, wear resistance and self-lubrication, oil resistance, chemical resistance, creep resistance, low water absorption, and can maintain its mechanical, chemical and electrical properties within a relatively wide temperature range. It is an engineering plastic with excellent comprehensive properties and is widely used in industries such as automobiles, electronics and household appliances.

[0003] Copolymer polyoxymethylene is mainly composed of (-CH2-O-) chain segments, with a small amount of (-CH2CH2O-) or (-CH2CH2CH2CH2O-) chain segments mixed therein, and the end groups are macromolecules with methoxy ether or hydroxyethyl ether structures. This results in that during the melt processing, POM is prone to chain scission under the action of heat and oxygen, and this thermal decomposition is autocatalytic, releasing a large amount of formaldehyde, resulting in a large odor. This strong pungent odor has greatly restricted the application of polyoxymethylene products in industries such as automobiles.

[0004] The methylene group in the molecular structure of polyoxymethylene has poor stability. Under the combined action of ultraviolet light and oxygen, the molecular chain breaks, releasing gases such as formaldehyde, and at the same time causing a decrease in mechanical properties and a change in surface color. Therefore, when applied to outdoor use scenarios, it is necessary to improve the weather resistance of POM materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyoxymethylene composition with low odor and good ultraviolet resistance, a preparation method thereof, and an application thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A polyoxymethylene composition, by weight, comprises the following components:

[0008] 100 parts of copolymer polyoxymethylene resin;

[0009] 0.3 - 1 part of a hydroxybenzophenone ultraviolet absorber;

[0010] 1 - 10 parts of polyethylene glycol;

[0011] The number-average molecular weight range of the polyethylene glycol is 800 - 6000. The test method can be: analyzing low-molecular-weight polyethylene glycol by liquid chromatography, using a C18 reversed-phase chromatographic column; the mobile phase includes two phases, A and B, with a total of 100%, where phase A is a mixed solvent of methanol and tetrahydrofuran, and phase B is water. After mixing phases A and B according to the volume ratio, gradient elution is carried out. The elution program is: the initial proportion of phase A is 5% - 15%, and the rest is phase B. Gradually transition to phase A accounting for 25 - 50% and the rest being phase B over a time period of 15 - 20 min, with a flow rate of 0.2 - 1 mL / min; the detector uses an evaporative light scattering detector: calculating the relative percentage content of each chromatographic peak by the area percentage method, and evaluating the number-average molecular weight of polyethylene glycol based on the number and relative percentage content of the chromatographic peaks. The copolyoxymethylene resin is a condensate of dioxolane and trioxymethylene, where dioxolane accounts for 1 - 3 wt% of the total weight of the copolyoxymethylene. Preferably, dioxolane accounts for 1.8 - 2.3 wt% of the total weight of the copolyoxymethylene.

[0012] In the technical solution of the present invention, the melt index range of the copolyoxymethylene resin that can be achieved is 2.5 g / 10 min - 27 g / 10 min, and the melt index test conditions are 190 °C / 2.16 KG.

[0013] The copolyoxymethylene can be a commercially available product or obtained by self-preparation. The self-preparation method is: according to the weight percentage of the dioxolane comonomer unit in the copolyoxymethylene resin, after thoroughly mixing trioxymethylene with the end-capping agent butyral (0.1% - 0.35 wt% of the total feed amount of trioxymethylene and dioxolane), it is mixed into the prepolymer formed by mixing the catalyst boron trifluoride (feed amount 200 - 300 ppm) and dioxolane. Then, the mixture is subjected to a polymerization reaction for 2 - 3 hours using a kneader at 80 - 100 °C. After uniformly mixing the reacted polymer powder with melamine, it is extruded and pelletized using a twin-screw extruder at 200 - 240 °C, and an aqueous solution of triethylamine is introduced into the middle of the extruder to finally obtain polyoxymethylene pellets.

[0014] The content of dioxolane in the total weight of the copolyoxymethylene can be measured by nuclear magnetic resonance hydrogen spectrum.

[0015] Preferably, 3 - 8 parts of polyethylene glycol.

[0016] The hydroxybenzophenone ultraviolet light absorber is selected from at least one of 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-acryloyloxyethoxybenzophenone, (1,4-butanediyl)bis[oxy(2-hydroxy-4,1-phenylene)]bis[benzophenone].

[0017] Preferably, the hydroxybenzophenone ultraviolet absorber is selected from at least one of 2,2'-hydroxy-4-methoxybenzophenone and 2,4-dihydroxybenzophenone.

[0018] Preferably, the number-average molecular weight range of the polyethylene glycol is 2000-4000.

[0019] It can be decided whether to add 0-1 part of antioxidant according to the actual situation.

[0020] The antioxidant can be 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 2,5-di-tert-butyl-4-hydroxybenzyl dimethylamine, diethyl 3,5-di-tert-butyl-4-hydroxybenzyl phosphate, stearyl 3,5-di-tert-butyl-4-hydroxybenzyl phosphate, 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distearyl-thiotriazolylamine, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylglycidyl allyl ether)-1,3,5-triazine, N,N'-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamide), N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythrityl tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], triethylene glycol bis[3-(3,5-dimethyl-4-hydroxyphenyl)propionate], diethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], etc.

[0021] It is also possible to consider adding 0-30 parts of filler. The filler can be a mineral filler or a fiber filler such as glass fiber.

[0022] The preparation method of the polyoxymethylene composition of the present invention includes the following steps: mixing each component evenly according to the ratio, and extruding and pelletizing through a twin-screw extruder at a temperature range of 180-200°C and a rotation speed of 300-400 revolutions per minute to obtain the polyoxymethylene composition.

[0023] The polyoxymethylene composition of the present invention is used for preparing vehicle components such as sunroof rails, passenger instrument panels, wiper components, etc.

[0024] The present invention has the following beneficial effects:

[0025] By introducing polyethylene glycol and hydroxybenzophenone ultraviolet absorbers with specific contents and molecular weights, the present invention can improve the defect of excessive odor caused by the easy decomposition of cyclic ether copolymerized polyoxymethylene, and has a preferable ultraviolet resistance effect. Detailed Embodiments

[0026] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0027] The sources of the raw materials used in the present invention are as follows:

[0028] The preparation method of the following copolymerized polyoxymethylene resin is as follows: According to the weight percentage of the dioxolane copolymerized unit in the copolymerized polyoxymethylene resin, trioxymethylene and the end-capping agent butyraldehyde (0.15 - 0.20 wt% of the total feed amount of trioxymethylene and dioxolane) are fully mixed and then introduced into the prepolymer formed by mixing the catalyst boron trifluoride (feed amount 200 ppm) and dioxolane. Then, the mixture is polymerized using a kneader at 80 - 100 °C for 2 - 3 hours. After the polymer powder obtained from the reaction is mixed evenly with melamine, it is extruded and pelletized using a twin-screw extruder. An aqueous solution of triethylamine is introduced into the middle of the extruder, and finally, a polyoxymethylene raw material is obtained, and the molecular weights of the following copolymerized polyoxymethylene resins are similar. The extrusion process is as follows: the temperature of the first zone is 200 - 210 °C, the temperature of the second zone is 200 - 210 °C, the temperature of the third zone is 210 - 220 °C, the temperature of the fourth zone is 210 - 220 °C, the temperature of the fifth zone is 220 - 230 °C, the temperature of the sixth zone is 220 - 230 °C, the temperature of the seventh zone is 220 - 230 °C, the temperature of the eighth zone is 220 - 230 °C, the temperature of the ninth zone is 230 - 240 °C; the main machine speed is 300 - 400 revolutions per minute.

[0029] Copolymerized polyoxymethylene resin A: A condensate of trioxymethylene and dioxolane, with dioxolane accounting for 1 wt% of the total weight of the copolymerized polyoxymethylene, self-made;

[0030] Copolymerized polyoxymethylene resin B: A condensate of trioxymethylene and dioxolane, with dioxolane accounting for 1.8 wt% of the total weight of the copolymerized polyoxymethylene, self-made;

[0031] Copolymerized polyoxymethylene resin C: A condensate of trioxymethylene and dioxolane, with dioxolane accounting for 2.3 wt% of the total weight of the copolymerized polyoxymethylene, self-made;

[0032] Copolymerized polyoxymethylene resin D: A condensate of trioxymethylene and dioxolane, with dioxolane accounting for 3 wt% of the total weight of the copolymerized polyoxymethylene, self-made;

[0033] Copolymerized polyoxymethylene resin E: A condensate of trioxymethylene and dioxolane, with dioxolane accounting for 5 wt% of the total weight of the copolymerized polyoxymethylene, self-made;

[0034] Homopolymerized polyoxymethylene resin: Grade POM 500P, homopolymerized POM grade, melt index of 14 g / 10 min, DuPont Company, USA;

[0035] Polyethylene glycol A: Number-average molecular weight is approximately 800, PEG800, Guangdong Nanhui New Materials Co., Ltd.;

[0036] Polyethylene glycol B: Number-average molecular weight is approximately 2000, PEG2000, Shanghai Dongda Chemical Co., Ltd.;

[0037] Polyethylene glycol C: Number-average molecular weight is approximately 4000, PEG4000, Shanghai Dongda Chemical Co., Ltd.;

[0038] Polyethylene glycol D: Number-average molecular weight is approximately 6000, PEG6000, Shanghai Dongda Chemical Co., Ltd.;

[0039] Polyethylene glycol E: Number-average molecular weight is 360 - 440, PEG200DL, Guangdong Nanhui New Materials Co., Ltd.;

[0040] Ultraviolet light absorber A: 2-hydroxy-4-octyloxybenzophenone, Cyasorb UV-531, Cytec Industries Inc., USA;

[0041] Ultraviolet light absorber B: 2-hydroxy-4-methoxybenzophenone, Cyasorb UV-9, Cytec Industries Inc., USA;

[0042] Ultraviolet light absorber C: 2,2'-dihydroxy-4-methoxybenzophenone, Cyasorb UV-24, Cytec Industries Inc., USA;

[0043] Ultraviolet light absorber D: 2,4-dihydroxybenzophenone, UV BP-1, Qingdao Deda Zhicheng Chemical Co., Ltd.;

[0044] Ultraviolet light absorber E: 2-hydroxy-4-dodecyloxybenzophenone, Chimassorb 125, BASF SE, Germany;

[0045] Ultraviolet light absorber F: 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole, UV-234, Qingdao Deda Zhicheng Chemical Co., Ltd.;

[0046] Ultraviolet light absorber G: 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-octyloxyphenol, UV-1164, Qingdao Deda Zhicheng Chemical Co., Ltd.;

[0047] Antioxidant: Irganox 245 / Irganox 1098 compounded in a weight ratio of 2:1, purchased from BASF.

[0048] Preparation method of the polyoxymethylene compositions in the examples and comparative examples: According to the ratio, mix each component evenly, and extrude and pelletize through a twin-screw extruder. The temperature range is 180 - 200 °C, and the rotation speed is 300 - 400 revolutions per minute to obtain the polyoxymethylene composition.

[0049] Test methods for each item:

[0050] (1) UV resistance test: Inject the sample into a square plate and conduct the test according to the Volkswagen PV3929-2008 standard. The blackboard temperature is 90 °C, the sample chamber temperature is 50 °C, the relative humidity is 20 ± 10%, and the irradiation intensity is 75 W / m 2 , and the UV wavelength range is 300 - 400 nm. The irradiation time is 1200 h, and the total irradiation dose is 300 MJ / m 2 . The test equipment is produced by ATLAS in the United States, model CI4000. Calculate the color difference change value through the following formula:

[0051]

[0052] L1, a1, b1: Test values before xenon lamp aging;

[0053] L2, a2, b2: Test values after xenon lamp aging;

[0054] The color difference test equipment is produced by X-Rite in the United States, model Color-Eye 7000A.

[0055] (2) Odor level test: The odor level test is carried out according to the Volkswagen PV3900 standard. The specific process is as follows: Take 20 g of the pellets extruded by the twin-screw extruder and put them into a 1 L glass bottle dedicated to testing odor. Seal it and put it into an 80 °C oven. Take it out after 2 hours to evaluate the odor and evaluate it according to the following standards. Evaluate by 5 professional odor testers and then take the average value.

[0056] Scoring Grade Judgment Criteria 1 Odorless 2 With odor, but no disturbing odor 3 With obvious odor, but no disturbing odor 4 With disturbing odor 5 With strong disturbing odor 6 With intolerable odor

[0057] Table 1: Weight parts of each component and test results of the polyoxymethylene compositions in Examples 1 - 5

[0058] Example 1 Example 2 Example 3 Example 4 Example 5 Types of Copolyoxymethylene Resin A B C D A Content of Copolyoxymethylene Resin 100 100 100 100 100 Ultraviolet Absorbent A 0.5 0.5 0.5 0.5 0.5 Polyethylene Glycol A 3 3 3 3 1 Antioxidant 0.1 0.1 0.1 0.1 0.1 ΔE 2.32 2.18 2.12 2.21 2.65 Odor Grade 3.5 3.4 3.2 3.4 4.0

[0059] As can be seen from Examples 1 - 4, it is preferred that the dioxolane accounts for 1.8 - 2.3 wt% of the total weight of the copolymerized polyoxymethylene.

[0060] Table 2: Weight parts of each component and test results of the polyoxymethylene compositions in Examples 6 - 9

[0061] Example 6 Example 7 Example 8 Example 9 Copolyoxymethylene Resin A 100 100 100 100 Ultraviolet Absorbent A 0.5 0.5 0.3 1 Polyethylene Glycol A 8 10 3 3 Antioxidant 0.1 0.1 0.1 0.1 ΔE 2.55 2.9 3.23 1.08 Odor Grade 3.1 2.9 3 3.6

[0062] As can be seen from Examples 5 / 1 / 6 / 7, when the content of polyethylene glycol is optimized, the ultraviolet resistance and odor grade are better.

[0063] Table 3: Parts by weight of each component of the polyoxymethylene composition in Examples 10 - 13 and test results

[0064] Example 10 Example 11 Example 12 Example 13 Copolyoxymethylene Resin A 100 100 100 100 Types of Ultraviolet Absorbent B C D E Content of Ultraviolet Absorbent 0.5 0.5 0.5 0.5 Polyethylene Glycol A 3 3 3 3 Antioxidant 0.1 0.1 0.1 0.1 ΔE 2.44 2.21 2.15 2.40 Odor Grade 3.5 3.3 3.3 3.4

[0065] As can be seen from Examples 1 / 10 - 13, when the ultraviolet absorber is optimized, ΔE is lower and the odor is smaller.

[0066] Table 4: Parts by weight of each component of the polyoxymethylene composition in Examples 14 - 16 and test results

[0067] Example 14 Example 15 Example 16 Copolyoxymethylene Resin A 100 100 100 Ultraviolet Absorbent A 0.5 0.5 0.5 Types of Polyethylene Glycol B C D Content of Polyethylene Glycol 3 3 3 Antioxidant 0.1 0.1 0.1 ΔE 2.21 2.14 2.08 Odor Grade 3.5 3.6 3.7

[0068] As can be seen from Examples 1 / 14 - 16, when the polyethylene glycol with an optimized number - average molecular weight is used, the comprehensive performance of ultraviolet resistance and odor grade is better.

[0069] Table 5: Parts by weight of each component of the polyoxymethylene composition in the comparative examples and test results

[0070] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Copolyoxymethylene Resin A 100 100 100 100 100 Copolyoxymethylene Resin E 100 Homopolyoxymethylene Resin 100 Types of Ultraviolet Absorbent F G A A A A A Content of Ultraviolet Absorbent 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Polyethylene Glycol A 3 3 3 3 0 12 Polyethylene Glycol E 3 Antioxidant 0.1 0.1 0.1 0.1 0.1 0.1 0.1 ΔE 4.23 3.85 3.76 3.96 3.89 4.65 5.23 Odor Grade 4.1 4 3.7 3.8 3.8 4.5 3.8

[0071] As can be seen from Comparative Examples 1 / 2, other types of ultraviolet absorbers have poor ultraviolet resistance and strong odors in the technical solution of the present invention.

[0072] As can be seen from Comparative Example 3, if the content of the comonomer in the copolymerized polyoxymethylene resin is too high, the ultraviolet resistance is poor.

[0073] As can be seen from Comparative Example 4, the homopolyoxymethylene resin cannot achieve the technical effects of the present invention.

[0074] As can be seen from Comparative Example 5, if the number - average molecular weight of polyethylene glycol is too low, the ultraviolet resistance is very poor, and due to the too - low number - average molecular weight, the odor grade is also high.

[0075] As can be seen from Comparative Examples 6 / 7, if polyethylene glycol is not contained or the content of polyethylene glycol is too high, the technical effects are poor, especially when the content of polyethylene glycol is too high, the ultraviolet resistance is very poor.

[0076] As can be seen from the above examples and comparative examples, ΔE of the technical solution of the present invention is < 3.3, and at the same time, the odor grade ≤ 4.

Claims

1. A polyoxymethylene composition, characterized in that, By weight, it comprises the following components: 100 parts of copolymerized polyoxymethylene resin; 0.3 - 1 part of hydroxybenzophenone ultraviolet light absorber; 3 - 8 parts of polyethylene glycol; The number-average molecular weight range of the polyethylene glycol is 800 - 6000; The copolymerized polyoxymethylene resin is a condensate of dioxolane and trioxymethylene, wherein dioxolane accounts for 1 - 3 wt% of the total weight of the copolymerized polyoxymethylene.

2. The polyoxymethylene composition according to claim 1, characterized in that, The copolymerized polyoxymethylene resin is a condensate of dioxolane and trioxymethylene, wherein dioxolane accounts for 1.8 - 2.3 wt% of the total weight of the copolymerized polyoxymethylene.

3. The polyoxymethylene composition according to claim 1, characterized in that, The hydroxybenzophenone ultraviolet light absorber is selected from at least one of 2-hydroxy-4-methoxybenzophenone, 2,2'-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-acryloyloxyethoxybenzophenone, and (1,4-butanediyl)bis[oxy(2-hydroxy-4,1-phenylene)]bis[benzophenone].

4. The polyoxymethylene composition according to claim 3, characterized in that, The hydroxybenzophenone ultraviolet light absorber is selected from at least one of 2,2'-hydroxy-4-methoxybenzophenone and 2,4-dihydroxybenzophenone.

5. The polyoxymethylene composition according to claim 1, wherein The number-average molecular weight range of the polyethylene glycol is 2000 - 4000.

6. The polyoxymethylene composition according to claim 1, characterized in that, By weight, it further comprises 0 - 1 part of antioxidant.

7. A method for preparing the polyoxymethylene composition according to any one of claims 1-6, characterized in that, It comprises the following steps: Mix each component evenly according to the ratio, and extrude and pelletize through a twin-screw extruder to obtain a polyoxymethylene composition.

8. Use of the polyoxymethylene composition according to any one of claims 1 to 6, characterized in that, It is used for preparing vehicle components.