AU2021105994A4 - Polyoxymethylene composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a polyoxymethylene composite material, which comprises the following components by weight: 70-95 parts of polyoxymethylene; 5-20 parts of SEBS; SEBS is modified by acid or amine. Due to the use of acid or amine modification and the existence of polystyrene chain segments, SEBS has reduced compatibility with polyoxymethylene due to steric hindrance effect, which reduces the ability of regular arrangement of POM molecular chains. When injection molded into products ortemplates, the incompatibility of the material itself will form a micro rough effect on the material surface. When the incident light reaches the micro rough surface, the reflection direction of light will change, resulting in diffuse reflection and low gloss materials.

Description

The invention discloses a polyoxymethylene composite material, which comprises the following components by weight: 70-95 parts of polyoxymethylene; 5-20 parts of SEBS; SEBS is modified by acid or amine. Due to the use of acid or amine modification and the existence of polystyrene chain segments, SEBS has reduced compatibility with polyoxymethylene due to steric hindrance effect, which reduces the ability of regular arrangement of POM molecular chains. When injection molded into products ortemplates, the incompatibility of the material itself will form a micro rough effect on the material surface. When the incident light reaches the micro rough surface, the reflection direction of light will change, resulting in diffuse reflection and low gloss materials.

EDITORIAL NOTE 2021105994

There are 6 pages of description only.

Polyoxymethylene composite material and preparation method thereof

TechnicalField The invention relates to the technical field of polymer materials, in particular to a polyoxymethylene composite material, a preparation method thereof and the use of SEBS as a matting agent in polyoxymethylene.

Background Technique Polyoxymethylene (POM) is divided into formaldehyde homopolymer or formaldehyde copolymer. Around 1955, DuPont Company of USA polymerized formaldehyde to obtain formaldehyde homopolymer. Polyoxymethylene is easy to crystallize, with a crystallinity of more than 70%. The melting temperature of homoformaldehyde is about 180 C. It is another engineering plastic with excellent comprehensive properties after polyamide. It has high mechanical properties, such as strength, modulus, wear resistance, toughness, fatigue resistance and creep resistance. It also has excellent electrical insulation, solvent resistance and processability. It is one of the five general engineering plastics. Acetal polymer, namely polyoxymethylene, is formed by the polymerization of formaldehyde. It is also often called Polyoxymethylene (POM). The preparation of polymers from formaldehyde was studied as early as the 1920s, but thermally stable materials were not prepared until DuPont developed Delrin in 1959. Homopolymer is prepared by anionic polymerization of very pure formaldehyde. Copolyformaldehyde was first developed and commercialized by Celanese in 1962, with the trade name "Celcon". The polymer is mainly polymerized with trimeric formaldehyde and dioxolane under the combined action of catalyst (BF3 and its ether/ butyl ether /ester complex are the main catalysts at present, the catalyst has appropriate reaction rate and is easy to be separated from the product after reaction) and molecular weight regulator (methylal meal). Compared with homoformaldehyde, the presence of C-C chain in the molecular chain of copolyformaldehyde makes the chain degradation of formaldehyde terminate when the decomposition reaction reaches the C-C bond, so as to improve the thermal stability of the material and be more conducive to processing. SEBS is a linear triblock copolymer with polystyrene as terminal segment and ethylene butene copolymer obtained by hydrogenation of polybutadiene as intermediate elastic block. SEBS is mainly used as toughening agent in various thermoplastic resins, and it is also modified. Chinese patent 201210572164.2 discloses an ABS / POM alloy. SEBS grafted maleic anhydride is added as a compatibilizer, but other aspects of SEBS modification (such as acid modification or amine modification) are not deeply explored to reduce the surface gloss of polyoxymethylene. Chinese patent 201611151834.8 discloses a composite modified SEBS sheath material toughened by ethylene vinyl acetate copolymer, which uses a large amount of stearic acid to swell SEBS. When SEBS is fully swollen in stearic acid, oily SEBS is obtained to reduce the agglomeration effect of components such as ethylene vinyl acetate copolymer and limestone in the system. The effect of modifying SEBS to bring low gloss to POM has not been recorded.

Summary of the Invention The invention aims to provide a polyoxymethylene composite material and a preparation method thereof, which has the advantages of low gloss. Another object of the invention is to provide the use of SEBS as a matting agent in polyformaldehyde. The invention is realized by the following technical scheme: A polyoxymethylene composite material is characterized in that it comprises the following components by weight: Polyoxymethylene 70-95 parts; SEBS 5-20 parts; SEBS is modified by acid or amine. The acid modification method of SEBS is bromination or acetylation, connecting a bromine or acetyl group to the para position of the benzene ring, and then acidifying with acid or oxidizing the acetyl group to obtain the carboxylic acid functional group. The amine modification method is to introduce nitro into the para position of the benzene ring in SEBS, and then convert nitro into amino through reduction reaction. Preferably, SEBS is amine modified. Compared with acid modification, amine modified SEBS has better extinction effect. Specifically, the acid modification method of SEBS is as follows: dissolve 5g SEBS in 50ml trichloromethane solution, then add 0.2g anhydrous FeCl3 to it, slowly add 2ml bromine solution under stirring conditions, stir the solution at room temperature under dark conditions for 1 day, precipitate the polymer with excess ethanol, then filter the solution, wash it with acetone and water in turn, and then dry it at 100 C, obtain brominated SEBS; dissolve 4g of brominated SEBS in 15 ml ofdiphenyl ether, and a mixture of 16 ml of diethyl phosphite, 0.08 g of PD (dbac) .CHCl 3 3 and 1.2 ml of triethylamine was added to the solution, and then refluxed under nitrogen at 155°C for 2 days. The polymer was precipitated with ethanol / aqueous solution (volume ratio 90 / 10), filtered and dried to obtain acid modified SEBS. PD (dbac)3 is a transition metal palladium catalyst, which can also be replaced by other catalysts. Specifically, the SEBS amine modification method is as follows: dissolve 5g SEBS in 50ml chloroform solution, slowly drop 60ml nitric acid and 40ml concentrated sulfuric acid into the solution under stirring conditions, stir at 70 C for 1h after the heat is completely dissipated, then neutralize the excess acid with 20% (w/w) NaOH solution, pour the chloroform layer into ethanol, precipitate the polymer, filter and dry, Nitro SEBSwas obtained; 4g of nitrogenated SEBS was dissolved in 30ml THF, 60g of stannous chloride was dissolved in 60ml HCI and stirred at 60 C to prepare the reduction mixture. The reduced mixture was added to the previous solution and refluxed at 85 C for 3 hours, then neutralized with 10% (w/w) NaOH, precipitated the polymer with ethanol, filtered and dried to obtain aminated SEBS. The general idea of acid modification and amine modification of SEBS can be as above, but the above reagents, dosage and reaction conditions can be adjusted according to the actual situation. It can also be that SEBS is grafted with GMA, and then the branched chain of GMA is acid modified. The invention utilizes the steric effect of polystyrene chain segments in SEBS on polyoxymethylene and poor compatibility, and then uses acid or amine to modify SEBS, which further reduces the compatibility between SEBSand polyoxymethylene and reduces theability of regular arrangement of polyoxymethylene molecular chains. When injection molding into products or templates, the incompatibility of the material itself will form a micro rough effect on the material surface, When the incident light reaches the slightly rough surface, the reflection direction of the light will change and diffuse reflection will appear, so as to obtain the low gloss polyoxymethylene composite. The acid value of the SEBS is 5-15 (mg CH 30Na/g). Generally, SEBS has a certain acid value only after it is modified with acid or amine. Theacid-base titration method is used to test the acid value of SEBS: themodifiedSEBS istitrated with0.1mol/I CH 30Na solution, andthe acid value of SEBS is calculated through thetitrationend point. Take a certain amount of SEBS, add it into 50ml of chloroform, completely dissolve it, add bromofen blue indicator, shake it well, titrate it with CH 30Na solution, stop the titration when the solution changes from yellow to blue, and calculate the acid value" mg CH 30Na/g "represents the milligram of sodium methoxide required to neutralize 1g of sample. The weight average molecular weight of the acid or amine modified SEBS of the invention is 30000-100000. Preferably, the styrene segment content of the SEBS is 10-40%. Due to the steric hindrance effect, the compatibility with POM is reduced, so as to effectively reduce the gloss. During the test, it is found that when the content of styrene segment is too high, the compatibility is too poor and the extinction performance can be improved, but it will lead to poor other properties of polyoxymethylene composites. When the content of styrene segment is too low, the extinction effect is greatly reduced. As found in the experiment, when the styrene segment content is about 43%, compared with the test case with styrene segment content of about 37%, the impact strength is reduced by 15%, and the application is limited; When the styrene segment content is about 8%, the extinction performance is only 35% of that of the test example with the styrene segment content of about 37%. The polyoxymethylene is at least one of homopolyoxymethylene or copolymerized polyoxymethylene; The melting index of the polyoxymethylene is 2 ~ 28g/10min (190°C/2.16kg). It also includes 0.5-1.2 parts of formaldehyde absorbent by weight; The formaldehyde absorbent is selected from at least one of magnesium oxide, magnesium hydroxide, alumina and aluminum hydroxide. Polyoxymethylene may decompose toxic gas of formaldehyde during use, melt extrusion, molding and injection molding, and formaldehyde absorbent shall be added according to the situation. It also includes 0.1-10 parts by weight of auxiliary agent; The auxiliary agent is selected from at least one of antioxidant, lubricant, heat stabilizerand UV absorption additive. The lubricant is selected from at least one of stearate lubricant, fatty acid lubricant and stearate lubricant; The stearate lubricant is selected from at least one of calcium stearate, magnesium stearate and zinc stearate; The fatty acid lubricant is selected from at least one of fatty acid, fatty acid derivative and fatty acid ester; The stearate lubricant is selected from at least one of pentaerythritol stearate; Preferably, the lubricant is selected from at least one of fatty acid lubricant and stearate lubricant. Antioxidants include primary antioxidants or stabilizers (such as hindered phenols and / or secondary arylamines) and optional auxiliary antioxidants (such as phosphate and / or thioesters). Suitable antioxidants include, for example, organic phosphate esters, such as tris (nonylphenyl) phosphite, tris (2,4-di-tert-butyl phenyl) phosphite, di (2,4-di-tert-butyl phenyl) pentaerythritol diphosphate, Distearyl pentaerythritol diphosphate, etc., alkylated monophenols or polyphenols; Alkylation reaction products of polyols and dienes, such as tetramethylene (3,5-di-tert-butyl-4-hydroxy hydrogenated cinnamate)] methane, etc; Butylation reaction products of p-cresol or dicyclopentadiene; Alkylated hydroquinone; Hydroxylated thiodiphenyl ether; Alkyl bisphenol; Benzyl compound; P-( Ester of 3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with monohydric alcohol or polyol; P-( Ester of -tert-butyl-4-hydroxy-3-methylphenyl) - propionic acid with monohydric alcohol or polyol; Esters of thioalkyl or thioaryl compounds, such as Distearyl thiopropionate, lauryl thiopropionate, di (tridecyl) thiopropionate, octadecyl-3 - (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetra [3 - (3,5-di-tert-butyl-4-hydroxyphenyl)] propionate, etc; P-( Amide of 3,5-di-tert-butyl-4-hydroxyphenyl) - propionic acid, etc; Or a combination comprising at least one of the aforementioned antioxidants. Suitable heat stabilizers include, for example, organic phosphite, such as triphenyl phosphite, tris (2,6-Dimethylphenyl) phosphite, tris (mixed mono and dinonylphenyl) phosphite, etc; Phosphonate esters, such as dimethyl phenylphosphonate, etc; Phosphate esters, such as trimethyl phosphate, etc; Or a combination comprising at least one of the aforementioned heat stabilizers. Light stabilizers and / or ultraviolet (UV) absorbing additives can be added. Suitable light stabilizers include, for example, benzotriazoles, such as 2 - (2-hydroxy-5-methylphenyl) benzotriazoles, 2 - (2-hydroxy-5-tert octylphenyl) - benzotriazoles and 2-hydroxy-4-n-octyloxybenzophenone, etc., as well as UV absorbers of triazines or combinations containing at least one of the aforementioned light stabilizers. Suitable UV absorbing additives include, for example, hydroxybenzophenones; Hydroxybenzotriazoles; Hydroxybenzotriazines; Cyanoacrylate; Oxalyl diphenylamine; Benzoxazinones; 2 - (2 h-be nzot riazole-2-yl) - 4 - (1,1,3,3-tetramethylbutyl) phenol (cya sorm 5411); 2-hydroxy-4-n-octoxybenzophenone (cyasorm 531); 2 - [4,6-bis (2,4-dimethylphenyl) 1,3,5-triazine-2-yl] - 5 - (octyloxy) phenol (1164); 2,2 '- (1,4-Phenylene) bis (4h-3,1-benzoxazine-4-one) (cyasorm uv-3638); 1,3-bis [(2-cyano-3,3-diphenylacryloyl) oxy] 2,2-bis [[(2-cyano-3,3-diphenylacryloyl) oxy] methyl] propane (uvinul 3030); Nano sized inorganic materials, such astitanium oxide, cerium oxide and zinc oxide, all of which have a particle size of less than 100 nm, orthe like; Or a combination containing at least one of the aforementioned UV absorbers. The preparation method of the polyoxymethylene composite comprises the following steps: adding polyoxymethylene, SEBS, auxiliary agent and formaldehyde absorbent into a high-speed mixer to mix evenly, and then obtaining the polyoxymethylene composite through screw extrusion and granulation; The temperature range of the screw is 120-200 C, and the rotating speed is 250-500 rpm. The use of SEBS as a matting agent in polyoxymethylene includes the following components by weight: 70-95 parts of polyoxymethylene; 5-20 parts of SEBS; SEBS is modified by acid or amine. Compared with the prior art, the invention has the following beneficial effects: The invention can reduce the gloss of polyoxymethylene by adding SEBS modified with acid or amine to polyoxymethylene with an acid value of 5-15 (mg CH 30Na/g). Specifically, SEBS modified by acid or amine is added to the system. The compatibility between such SEBS and polyoxymethylene resin matrix becomes worse, which reduces the ability of regular arrangement of polyoxymethylene molecular chains. When injection molding into products or templates, the incompatibility of the material itself will form a micro rough effect on the material surface. When the incident light reaches the micro rough surface, the reflection direction of the light will change,

Diffuse reflection occurs, resulting in low gloss polyoxymethylene composites.

Detailed Description of preferred Embodiment The invention is further described below through specific embodiments. The following embodiments of the invention that can better reflect the idea of the invention, but the invention is not limited by the following embodiments. The raw materials used in the example and comparative examples are as followings, but are not limited to the following raw materials: Polyoxymethylene: Longyu POM MC90, copolymerized POM, melting index: 9g/10min (190°C /2.16kg); SEBS-A:acid modification. The raw material of SEBS is Kraton g1650. It is self-made and modified by the acid modification method in the description, and the acid value is 10.2 mg CH 30Na/g, the weight average molecular weight is about 70000, styrene segment content is about 30%; SEBS-B: amine modification. The raw material of SEBS is Kraton G1652. It is self-made and modified by the acid modification method in the description, and the acid value is 5.1 mg CH 30Na/g, the weight average molecular weight is about 50000, and the content of styrene segment is about 30%; SEBS -C: ordinary SEBS, SEBS 3151, without acid or amine modification, with a molecular weight of about 40000 and a styrene segment content of about 32%; SEBS-D: S902, GMA grafting rateof 3%, without acid or amine modification. SEBS -E: acid modification, GMA grafting SEBS, self-made modification by using the acid modification method in the description, with an acid value of 9.7 mg CH 30Na/g, the weight average molecular weight of about 65000 and a styrene segment content of about 27%; Magnesium oxide: KYOWAMAG 150; Antioxidant: hindered phenolic antioxidant IRGANOX 245 / hindered phenolic antioxidant RIANOX 1098; The preparation method of the polyoxymethylene composite of the examples and the comparative examples comprises the following steps: adding polyoxymethylene, SEBS, formaldehyde absorbent and additives into the high-speed mixer to mix evenly, and then obtaining the polyoxymethylene composite through screw extrusion and granulation; The temperature of the screw is 120 /160/ 170 /180 /180/ 180 /180 /180/ 180 /190 °C,andthe

rotating speed is 300 rpm. Various performance test methods: (1) Glossiness: the glossiness is tested by photoelectric glossiness meter, 100mm*100mm *2.0mm square plates are injected, the glossiness of 10 square plates is tested by photoelectric glossiness meter(60 0 angle), and the averagevalue is taken. Table 1: distribution ratio (parts by weight) of each group and performance test results of examples and comparative examples(CE) Exam Exam Exam Exam Exam Exam CE1 CE 2 CE 3 plel ple 2 ple 3 ple 4 ple 5 ple 6 polyoxymet 85 85 85 85 85 85 85 85 85 hylene SEBS-A 5 8 12 20 - - - - SEBS-B - - - - 12 - - - -

SEBS-C - - - - - - 12 - SEBS-D - - - - - - - 12 SEBS-E - - - - 12 - - Magnesium oxide Antioxidant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Glossiness 26.2 21.5 16.8 4.3 11.3 19.7 75.2 69.8 86.5

It can be seen from examples 1-4 and comparative example 3 that the addition of acid modified SEBS increases, and the gloss of the surface of polyoxymethylene composite decreases. It can be seen from example 3 / 5 and comparative example 1 / 2 / 3 that ordinary SEBS can not effectively reduce the surface gloss of polyoxymethylene composites. It can be seen from examples 3 and 5 that the extinction effect of amine modified SEBS is better.

EDITORIAL NOTE 2021105994

There is 1 page of claims only.

Claims (11)

1. A polyoxymethylene composite material, which is characterized in that it comprises the following components by weight: Polyoxymethylene 70-95 parts; SEBS 5-20 parts; SEBS is modified by acid or amine.

2. The polyoxymethylene composite material according to claim 1, which is characterized in that the acid modified SEBS contains carboxylic acid functional groups; The amine modified SEBS contains amino groups.

3. The polyoxymethylene composite material according to claim 2, which is characterized in that the acid value of the SEBS is 5-15 (mg CH 30Na /g).

4. The polyoxymethylene composite material according to claim 1, which is characterized in that the acid modification method is by bromination or acetylation, a bromine or acetyl group is connected to the para position of the benzene ring, and then acidified with acid or oxidized by acetyl group to obtain carboxylic acid functional group; The amine modification method is to introduce nitro into the para position of the benzene ring in SEBS, and then convert nitro into amino through reduction reaction; Preferably, SEBS is amine modified.

5. The polyoxymethylene composite material according to claim 4, which is characterized in that firstly, SEBS is graftedwith GMA, and then the GMA branch chain is acid modified.

6. The polyoxymethylene composite material according to any one of claims 1-3, which is characterized in that the weight average molecular weight of the SEBS is 30000-100000, wherein the styrene segment accounts for 10-40% of the total segment molecular weight.

7. The polyoxymethylene composite material according to claim 1, which is characterized in that the polyoxymethylene is at least one of homopolyoxymethylene or copolymerized polyoxymethylene; The melting index of the polyoxymethylene is 2 ~ 28g / 10min (190°C/2.16KG).

8. The polyoxymethylene composite material according to claim 1, which is characterized in that it further comprises 0.5-1.2 parts of formaldehyde absorbent by weight; The formaldehyde absorbent is selected from at least one of magnesium oxide, magnesium hydroxide, alumina and aluminum hydroxide.

9. The polyoxymethylene composite material according to claim 1, which is characterized in that it further comprises 0.1-10 parts of auxiliaryagent byweight; The auxiliary agent is selected from at least one of antioxidant, lubricant, heat stabilizer and UV absorption additive.

10. The preparation method of the polyoxymethylene composite material according to claim 9, which is characterized in that it comprises the following steps: adding polyoxymethylene, SEBS and auxiliary agent into a high-speed mixer to mix evenly, and then obtaining the polyoxymethylene composite material through screw extrusion and granulation; The temperature range of the screw is 120-200 °C, and the rotating speed is 250-500 rpm.

11. The use of SEBS as a matting agent in polyoxymethylene is characterized in that it includes the following components by weight: 70-95 parts of polyoxymethylene; 5-20 parts of SEBS; SEBS is modified by acid or amine.