Thermostable toughened polyformaldehyde and preparation method thereof

Abstract

The preparation method comprises the following steps: firstly, grafting polyether amine on the surfaces of inorganic nanoparticles, compounding the polyether amine with polyamide with flexible long-chain alkyl and a polyformaldehyde matrix, and preparing the heat-stable toughened polyformaldehyde by taking isocyanate as a reactive compatibilizer, through the reaction of isocyanate groups with polyether amine amino groups, polyamide amino groups and polyformaldehyde terminal hydroxyl groups, the interface interaction and compatibility among the components are improved, and inorganic nanoparticles and polyamide molecules are promoted to be uniformly dispersed in a polyformaldehyde matrix; the polyformaldehyde / flexible polyamide / flexible polyether amine molecular entangled network and the nano cross-linked network between the polyformaldehyde / flexible polyamide / flexible polyether amine molecular entangled network and the inorganic nano particles are formed, the reinforcing and toughening effects on a polyformaldehyde matrix are achieved, and the effect of the polyamide formaldehyde absorbent is achieved by utilizing the reaction of polyamide amido and formaldehyde generated by degradation of polyformaldehyde; meanwhile, the inorganic nanoparticles also have the effect of absorbing formic acid generated by degradation of the polyformaldehyde, so that the thermal stability of the polyformaldehyde is favorably improved.

Description

Technical Field

[0001] The invention relates to a heat-stable toughened polyoxymethylene and a preparation method thereof, and belongs to the field of polymer material processing. Background Art

[0002] Polyoxymethylene (POM) is a 2 -O-] as the main chain, unbranched, high melting point, high density, high crystallinity thermoplastic engineering plastics, with excellent mechanical properties, creep resistance, fatigue resistance, wear resistance, self-lubricating and chemical resistance, etc., is the closest to metal among engineering plastics, can be used to replace non-ferrous metals and alloy products such as copper, aluminum, zinc, etc., and is widely used in the fields of electronics, automobiles, light industry, machinery, chemicals, building materials, etc.; however, due to its special molecular structure, polyoxymethylene is easily degraded under the action of heat, oxygen, etc., and its thermal stability is the worst among existing polymer materials, and its high crystallinity makes it easy to generate larger spherulites during the molding process, with high notch sensitivity and low impact toughness.

[0003] During the thermal oxidative degradation of polyformaldehyde, the formaldehyde produced by its depolymerization is easily oxidized into formic acid, which promotes its random acidolysis reaction, accelerates its molecular degradation, and greatly deteriorates its performance. Various nitrogen-containing compounds such as dicyandiamide, urea, and melamine are commonly used in industry to capture formaldehyde. However, this type of formaldehyde absorber has a low molecular weight, especially melamine, which can also sublime, making it easy to volatilize and lose during high-temperature processing and application of polyformaldehyde, making it difficult to exert its efficient removal effect on formaldehyde degradation products in the matrix and reducing the stabilization effect. Summary of the invention

[0004] In view of the above problems, the present invention provides a thermally stable toughened polyoxymethylene and a preparation method thereof. The technical solution is as follows: A heat-stable toughened polyoxymethylene is prepared by the reaction of polyoxymethylene, polyamide, antioxidant and coupling-treated inorganic nanoparticles under the action of a compatibilizer.

[0005] The inorganic nanoparticles subjected to coupling treatment are any one of nano-montmorillonite, nano-calcium carbonate, nano-wollastonite or talc subjected to polyetheramine coupling treatment.

[0006] The polyamide is any one of polyundecalactam or polylaurolactam. The polyetheramine is any one of amino-terminated polyoxypropylene ether with a molecular weight of 200-1000 g / mol or amino-terminated polyoxyethylene ether with a molecular weight of 200-1000 g / mol.

[0007] The antioxidant is any one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, N,N'-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hexanediamine, octadecyl-(4-hydroxy-3,5-di-tert-butylphenyl)propionate, triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate or 2,6-di-tert-butyl-4-methylphenol.

[0008] The compatibilizer is isocyanate.

[0009] The compatibilizer is any one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate or isophorone diisocyanate.

[0010] The present invention also provides a method for preparing a heat-stable toughened polyoxymethylene, comprising the following steps: (1) Coupling treatment of inorganic nanoparticles: Dispersing inorganic nanoparticles in water, adding polyetheramine to dissolve and disperse at room temperature, filtering, washing, and drying the product to constant weight to obtain coupling-treated inorganic nanoparticles; (2) Preparation of heat-stable toughened polyoxymethylene: The polyoxymethylene, antioxidant, polyamide and coupling-treated inorganic nanoparticles are uniformly mixed, melt-kneaded, and isocyanate is added at the same time, and extrusion granulation is performed to obtain a heat-stable toughened polyoxymethylene material.

[0011] The mass fractions of the raw materials in step (1) are: 0.1-20 parts of inorganic nanoparticles, 0.05-10 parts of polyetheramine, and 10-2000 parts of water; the mass fractions of the raw materials in step (2) are: 100 parts of polyoxymethylene, 0.05-5 parts of antioxidant, 0.1-10 parts of polyamide, 0.1-20 parts of coupling-treated inorganic nanoparticles, and 0.1-10 parts of isocyanate.

[0012] In step (1), ultrasonic dispersion treatment is performed for 20-200 minutes. In step (2), during extrusion granulation, the screw speed is 100-300 rpm and the barrel temperature is 150-230°C.

[0013] The present invention aims at the research and development of high-performance polyoxymethylene, and provides a heat-stable toughened polyoxymethylene and a preparation method thereof, which has the following beneficial effects: The polyetheramine containing a flexible chain is grafted onto the surface of the inorganic nanoparticles through hydrogen bonding with oxygen-containing groups such as hydroxyl groups on the surface of the inorganic nanoparticles, and is compounded with a polyamide having a flexible long-chain alkyl group and a polyformaldehyde matrix. Isocyanate is used as a reactive compatibilizer, and the interface effect and compatibility between the components are improved through the reaction of the isocyanate group with the amino group of the polyetheramine, the amino group of the polyamide and the terminal hydroxyl group of the polyformaldehyde, so as to promote the uniform dispersion of the inorganic nanoparticles and the polyamide molecules in the polyformaldehyde matrix, thereby forming a polyformaldehyde / flexible polyamide / flexible polyetheramine molecular entanglement network and a nano-crosslinking network between the polyamide and the inorganic nanoparticles, thereby exerting a reinforcing and toughening effect on the polyformaldehyde matrix.

[0014] Polyamide has a polyamine structure, and its amine group can react with formaldehyde produced by the degradation of polyformaldehyde molecules, thereby playing the role of a formaldehyde absorber. It has a high molecular weight and is not easy to volatilize and lose during high-temperature processing, storage, transportation and use of polyformaldehyde. It has excellent stability, thus effectively solving the problem of commonly used industrial formaldehyde absorbers such as melamine having low molecular weight and easy migration, which reduces the thermal stability effect.

[0015] Inorganic nanoparticles such as organic montmorillonite, nano-calcium carbonate, nano-wollastonite, and talc have a certain alkalinity and can absorb formic acid produced by the degradation of polyformaldehyde. The amino groups on the grafted polyetheramine molecules can also absorb formaldehyde, which is beneficial to improving the thermal stability of polyformaldehyde.

[0016] The heat-stable toughened polyformaldehyde prepared by the present invention can increase its thermal degradation temperature by 20-30°C relative to ordinary polyformaldehyde base materials, improve its impact strength by 20-30%, and maintain a relatively high tensile strength when the amount of polyamide used is 1 part and the amount of inorganic nanoparticles treated by coupling is 0.5-2 parts. DETAILED DESCRIPTION

[0017] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0018] Example 1 Disperse 0.5 parts of nano-montmorillonite in 50 parts of deionized water, add 1 part of amino-terminated polyoxypropylene ether with a molecular weight of 900 g / mol, dissolve at room temperature, stir evenly, use ultrasonic dispersion for 60 minutes, filter the product, wash with distilled water, and dry at 90°C for 8 hours to constant weight; 100 parts of polyoxymethylene, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (i.e., Irganox 1010), 1 part of polylaurolactam (nylon 12), and 0.5 parts of coupling-treated nano-montmorillonite are added into a high-speed mixer and mixed evenly. The mixture is melt-kneaded by a twin-screw extruder, and 1 part of toluene diisocyanate is fed from the side of the extruder. The mixture is extruded and granulated at a screw speed of 200 rpm and a barrel temperature of 170-190°C to obtain a heat-stable toughened polyoxymethylene material.

[0019] Example 2 Disperse 1 part of nano calcium carbonate in 200 parts of deionized water, add 5 parts of amino-terminated polyoxyethylene ether with a molecular weight of 1000 g / mol, dissolve at room temperature, stir evenly, use ultrasonic dispersion for 100 minutes, filter the product, wash with distilled water, and dry at 90°C for 8 hours to constant weight; 100 parts of polyoxymethylene, 0.3 parts of triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (i.e., Irganox 245), 2 parts of polyundecanoic acid amide (nylon 11), and 1 part of coupling-treated nano-calcium carbonate are added into a high-speed mixer and mixed evenly. The mixture is melt-kneaded by a twin-screw extruder, and 3 parts of diphenylmethane diisocyanate are fed from the side of the extruder. The mixture is extruded and granulated at a screw speed of 180 rpm and a barrel temperature of 160-200°C to obtain a heat-stable toughened polyoxymethylene material.

[0020] Example 3 Disperse 3 parts of nano-wollastonite in 400 parts of deionized water, add 3 parts of amino-terminated polyoxypropylene ether with a molecular weight of 600 g / mol, dissolve and stir evenly at room temperature, disperse by ultrasonic for 30 min, filter the product, wash with distilled water, and dry at 90°C for 8 h to constant weight; 100 parts of polyoxymethylene, 1 part of octadecyl propionate (i.e., Irganox 1076), 3 parts of polyundecanoic acid (nylon 11), and 3 parts of coupling-treated wollastonite are added into a high-speed mixer and mixed evenly. The mixture is melt-kneaded by a twin-screw extruder, and 5 parts of isophorone diisocyanate are added from the side of the extruder for feeding. The mixture is extruded and granulated at a screw speed of 150 rpm and a barrel temperature of 165-200°C to obtain a heat-stable toughened polyoxymethylene material.

[0021] Example 4 Disperse 3 parts of talc powder in 300 parts of deionized water, add 7 parts of 800 g / mol molecular weight amino-terminated polyoxyethylene ether, dissolve at room temperature, stir evenly, disperse by ultrasonic for 80 min, filter the product, wash with distilled water, and dry at 90°C for 8 h to constant weight; 100 parts of polyoxymethylene, 0.5 parts of 2,6-di-tert-butyl-4-methylphenol (i.e., BHT(264)), 5 parts of polylaurolactam (nylon 12), and 2 parts of coupling-treated talc are added into a high-speed mixer and mixed evenly. The mixture is melt-kneaded by a twin-screw extruder, and 8 parts of hexamethylene diisocyanate are fed from the side of the extruder. The mixture is extruded and granulated at a screw speed of 250 rpm and a barrel temperature of 160-190°C to obtain a heat-stable toughened polyoxymethylene material.

Claims

1. A heat-stable toughened polyoxymethylene, characterized in that: The composite is prepared by reacting polyoxymethylene, polyamide, antioxidant and coupling-treated inorganic nanoparticles under the action of a compatibilizer.

2. The heat-stable toughened polyoxymethylene according to claim 1, characterized in that: The inorganic nanoparticles subjected to coupling treatment are any one of nano-montmorillonite, nano-calcium carbonate, nano-wollastonite or talc subjected to polyetheramine coupling treatment.

3. The heat-stable toughened polyoxymethylene according to claim 1, characterized in that: The polyamide is any one of polyundecalactam or polylaurolactam.

4. The heat-stable toughened polyoxymethylene according to claim 2, characterized in that: The polyetheramine is any one of amino-terminated polyoxypropylene ether with a molecular weight of 200-1000 g / mol or amino-terminated polyoxyethylene ether with a molecular weight of 200-1000 g / mol.

5. The heat-stable toughened polyoxymethylene according to claim 1, characterized in that: The antioxidant is any one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, N,N'-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hexanediamine, octadecyl-(4-hydroxy-3,5-di-tert-butylphenyl)propionate, triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate or 2,6-di-tert-butyl-4-methylphenol.

6. The heat-stable toughened polyoxymethylene according to claim 1, characterized in that: The compatibilizer is isocyanate.

7. The heat-stable toughened polyoxymethylene according to claim 6, characterized in that: The compatibilizer is any one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate or isophorone diisocyanate.

8. A method for preparing a heat-stable toughened polyoxymethylene according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Coupling treatment of inorganic nanoparticles: Dispersing inorganic nanoparticles in water, adding polyetheramine to dissolve and disperse, filtering, washing, and drying the product to a constant weight to obtain coupling-treated inorganic nanoparticles; (2) Preparation of heat-stable toughened polyoxymethylene: The polyoxymethylene, antioxidant, polyamide and coupling-treated inorganic nanoparticles are uniformly mixed, melt-kneaded, and isocyanate is added at the same time, and extrusion granulation is performed to obtain a heat-stable toughened polyoxymethylene material.

9. The heat-stable toughened polyoxymethylene according to claim 8, characterized in that: The mass fractions of the raw materials in step (1) are: 0.1-20 parts of inorganic nanoparticles, 0.05-10 parts of polyetheramine, and 10-2000 parts of water; the mass fractions of the raw materials in step (2) are: 100 parts of polyoxymethylene, 0.05-5 parts of antioxidant, 0.1-10 parts of polyamide, 0.1-20 parts of coupling-treated inorganic nanoparticles, and 0.1-10 parts of isocyanate.

10. The heat-stable toughened polyoxymethylene according to claim 8, characterized in that: In step (1), ultrasonic dispersion treatment is performed for 20-200 minutes. In step (2), during extrusion granulation, the screw speed is 100-300 rpm and the barrel temperature is 150-230°C.