Cold-resistant PBT plastic and preparation method thereof

Abstract

The invention relates to a cold-resistant PBT plastic and a preparation method thereof, and belongs to the technical field of high polymer materials. The cold-resistant PBT plastic comprises the following components in parts by weight: 90-100 parts of PBT resin, 2-15 parts of a cold-resistant modifier, 5-25 parts of a modified flame retardant, 0.1-1 part of an antioxidant, 2-12 parts of a compatilizer and 0.1-2 parts of a lubricant, a polyurethane monomer in the cold-resistant modifier improves the impact resistance of the material; the Si-O bond of the product b is high in bond energy, long in bond length and excellent in low temperature resistance; the polyacrylate monomer is easy to slide and sticky and low in crosslinking degree; boron and phosphorus in the modified flame retardant are synergistic, a B-O-C carbon layer is formed at high temperature, flame-retardant gas is released, and smoke is reduced; in addition, a Si-O system prevents combustion products from escaping, thermal degradation is inhibited, low-smoke flame retardance is achieved, and the cold-resistant PBT plastic prepared by the invention not only has excellent low-temperature-resistant toughness and impact resistance, but also has a good flame-retardant effect.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a cold-resistant PBT plastic and a preparation method thereof. Background Art

[0002] With the advancement of science and technology and the vigorous development of industry, polybutylene terephthalate (PBT), as a thermoplastic engineering plastic with excellent comprehensive performance, is widely used in the fields of electronics and electrical, automotive industry, and household appliances due to its excellent heat resistance, chemical resistance and good processability.

[0003] However, in the face of the growing demand for extreme low temperature environments (below -40°C), ordinary PBT materials are not cold-resistant enough to meet the requirements of practical applications. In addition, PBT materials themselves have certain flammability. When a fire occurs, PBT plastics burn quickly and release a large amount of heat. It is difficult to extinguish itself during the combustion process, accompanied by thick smoke, which not only accelerates the spread of the fire, but also seriously threatens the safety of personnel and public property, and poses a risk to social stability that cannot be ignored. Therefore, the development of PBT plastics with excellent cold resistance and flame retardancy has important practical significance and application value. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a cold-resistant PBT plastic and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A cold-resistant PBT plastic comprises the following raw materials in parts by weight: 90-100 parts of PBT resin, 2-15 parts of cold-resistant modifier, 5-25 parts of modified flame retardant, 0.1-1 parts of antioxidant, 2-12 parts of compatibilizer, and 0.1-2 parts of lubricant; The antioxidant is antioxidant 412S; The compatibilizer is styrene-acrylonitrile-methacrylate glyceryl; The lubricant is polyethylene wax.

[0006] The cold-resistant modifier is prepared by the following method: Step A1: maleic anhydride, toluene and 5-amino-1-pentanol were mixed, stirred for reaction for 30 minutes, cyanuric chloride and tetrahydrofuran were added, stirred in an ice-water bath for 5 minutes, triethylamine was added, reacted for 10 minutes, washed, dried, filtered, and rotary evaporated to obtain product a; Further, the dosage ratio of maleic anhydride, toluene, 5-amino-1-pentanol, cyanuric chloride, tetrahydrofuran, and triethylamine is 2.47-2.96 g: 40-50 mL: 2 g: 3.06-4.01 g: 10 mL: 3.12-4.58 g; Step A2: 1,5-pentanediol and 1,6-hexamethylene diisocyanate were mixed, stirred at room temperature for 1 hour, and then product a was added and stirred at room temperature for 30 minutes to obtain a polyurethane monomer; Further, the mass ratio of 1,5-pentanediol, 1,6-hexamethylene diisocyanate, and product a is 2.25 g: 5-6.4 g: 0.8-1.2 g; Step A3: dodecylbenzenesulfonic acid and deionized water were mixed, the temperature was raised to 45°C, and the mixture was stirred evenly. Then, decamethylcyclopentasiloxane and 3-trimethoxysilane acrylate were slowly added dropwise, the mixture was mixed evenly, and the mixture was reacted for 3 hours. The mixture was cooled to room temperature to obtain product b. Furthermore, the dosage ratio of deionized water, decamethylcyclopentasiloxane, and 3-trimethoxysilane acrylate is 45 mL: 3-5 mol: 5-7 mol, and the dosage of dodecylbenzenesulfonic acid accounts for 1.4% of the total amount of deionized water in the system; Step A4: Ethyl acrylate, allyl methacrylate, sodium dodecyl sulfate, 0.05 g ammonium persulfate, sodium bicarbonate, deionized water and product b are mixed, the temperature is raised to 75°C, and the reaction is carried out for 30 minutes. Then, polyurethane monomer and 0.35 g ammonium persulfate are slowly added dropwise, and the reaction is carried out for 2 hours. Nitrogen is passed for protection, and the pH is adjusted to 8-10. The temperature is raised to 80°C, methyl methacrylate, hydroxyethyl acrylate and 0.1 g ammonium persulfate are added, and the reaction is carried out for 2.5 hours. After freezing, thawing and demulsification, and drying at 60°C for 12 hours, a cold-resistant modifier is obtained; Furthermore, the mass ratio of ethyl acrylate, allyl methacrylate, sodium dodecyl sulfate, sodium bicarbonate, deionized water, product b, polyurethane monomer, methyl methacrylate, and hydroxyethyl acrylate is 4-6g: 0.15-0.25g: 0.5g: 0.05g: 100g: 3g: 15-30g: 12-16g: 3g.

[0007] The modified flame retardant is prepared by the following method: Step B1: Mix glacial acetic acid and deionized water evenly, heat to 80°C, then drop methylvinyldimethoxysilane, control the dropping time to 15min, stir at 80°C for 2h, cool, filter, then add xylene and phenylboric acid, continue to react at 100°C for 5h, wash with water until neutral after the reaction, and vacuum filter to obtain an intermediate; Further, the dosage ratio of glacial acetic acid, deionized water, methylvinyldimethoxysilane, xylene, and phenylboric acid is: 20-30mL: 50mL: 1.5-2mol: 20-45mL: 1mol; Step B2: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, N,N-dimethylformamide and the intermediate are mixed, stirred at 150° C. for 9 hours, filtered, washed, and vacuum dried at 60° C. for 24 hours to obtain a modified flame retardant; Furthermore, the usage ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, N,N-dimethylformamide and the intermediate is 0.15-0.25 mol:40-60 mL:0.03-0.05 mol.

[0008] A cold-resistant PBT plastic and a preparation method thereof, specifically comprising the following steps: Step S1: adding the modified flame retardant and the antioxidant into a high-speed mixer, mixing at a speed of 200-500 r / min for 10-20 min, and then adding the lubricant, the compatibilizer and the cold-resistant modifier and mixing for 5-10 min to obtain a mixed material; Step S2: drying the PBT resin at 100-150°C for 2-3h, and then feeding the dried PBT resin and the mixed material into a twin-screw extruder for extrusion, cooling, and pelletizing to obtain a cold-resistant PBT plastic; wherein the temperature of the first zone of the twin-screw extruder is 180-210°C, the temperature of the second zone is 190-220°C, the temperature of the third zone is 190-220°C, the temperature of the fourth zone is 190-220°C, the head is 200-220°C, the main engine speed is 350-450r / min, and the pressure is 12-18MPa.

[0009] Beneficial effects of the present invention: The cold-resistant modifier prepared by the present invention firstly utilizes maleic anhydride and the amino group of 5-amino-1-pentanol to react to generate product a; then, utilizes the hydroxyl group of 1,5-pentanediol and the isocyanate bond of 1,6-hexamethylene diisocyanate to react to synthesize a polyurethane prepolymer, and the remaining isocyanate bond reacts with the hydroxyl group of product a to generate a polyurethane monomer; then, utilizes dodecylbenzene sulfonic acid to ionize H + , the decamethylcyclopentasiloxane is ring-opened to form a growth chain, which is then condensed with the hydrolyzable 3-trimethoxysilane acrylate to generate product b; finally, a polymer cold-resistant modifier is synthesized by grafting polyacrylate monomers. The polyurethane monomer in the cold-resistant modifier has the characteristics of high elasticity and high elongation. Its molecular chain is composed of alternating soft segments and hard segments. The soft segment uses 1,5-pentanediol to give the material good flexibility and extensibility, and the hard segment uses 1,6-hexamethylene diisocyanate to ensure the structural stability of the molecular chain and improve the impact resistance by forming hydrogen bonds and physical cross-linking points. This complementarity between soft and hard segments not only ensures the stability of the material, but also gives it excellent toughness. In addition, the Si-O bond formed by the opening of the decamethylcyclopentasiloxane in the product b has high bond energy and long bond length. It can remain stable at low temperatures and is not easy to break, thereby enhancing the low-temperature resistance of the modifier. At the same time, the added polyacrylate monomer has less intermolecular cross-linking, is easy to slide and sticky, and has good bonding properties. Therefore, the combined cold-resistant modifier has good low-temperature toughness and impact resistance.

[0010] The modified flame retardant prepared by the present invention firstly reacts the hydrolyzed silanol of methylvinyldimethoxysilane with the hydroxyl of phenylboronic acid under the action of glacial acetic acid to generate an intermediate; secondly, the carbon-carbon double bond of methylvinyldimethoxysilane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide flame retardant are combined to form a modified flame retardant. The flame retardant has a good flame retardant effect, forms a -Si-O- crosslinking system when degraded, effectively prevents the escape of combustion products and inhibits the thermal degradation of polymer materials, and realizes low smoke flame retardancy; the boron-based components are heated and dehydrated into carbon in the early stage of combustion, forming a glass-like protective layer to prevent the spread of combustion, and its aromatic boric acid group forms a boron oxygen network structure after being heated, which is further converted into a highly stable BOC carbon layer at high temperature, and at the same time, releases non-combustible gas to expand the carbon layer, forming a heat-insulating and oxygen-isolating barrier, which significantly improves the flame retardant performance; in addition, the combined use of boron and phosphorus not only enhances the flame retardant The hydrolysis stability of the agent is improved, and the flame retardant efficiency is improved through synergistic effect, which effectively reduces the generation of smoke. In particular, the phosphorus-nitrogen flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, as a phosphaphenanthrene compound with high thermal stability, can effectively flame retard in the condensed phase and the gas phase, promote the formation of a dense and continuous carbon layer, isolate oxygen and heat exchange, and further enhance the flame retardant effect; in addition, the modified flame retardant prepared by the present invention is halogen-free, which helps to reduce environmental pollution and damage to the ecosystem, is harmless to human health, and achieves sustainable development.

[0011] The cold-resistant PBT plastic prepared by the present invention not only has excellent low-temperature toughness and impact resistance, but also has good flame retardant properties, effectively inhibits the combustion process, prolongs the service life of the material, reduces the possibility of fire, and effectively protects human health. It can still maintain good toughness in extreme low-temperature environments, providing strong support for the innovation and development of various industries, making it have broad application prospects in the fields of automobiles, electronics, and household appliances. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0013] A cold-resistant PBT plastic and a preparation method thereof, specifically comprising the following steps: Step S1: weighing raw materials by weight, 90 parts of PBT resin, 2 parts of cold-resistant modifier (prepared in this embodiment), 5 parts of modified flame retardant (prepared in this embodiment), 0.1 parts of antioxidant, 2 parts of compatibilizer, and 0.1 parts of lubricant; adding the modified flame retardant and antioxidant 412S into a high-speed mixer, mixing at a speed of 200 r / min for 10 minutes, and then adding polyethylene wax, styrene-acrylonitrile-methacrylate hydroglycerol and cold-resistant modifier and mixing for 5 minutes to obtain a mixed material; Step S2: drying the PBT resin at 100° C. for 2 h, and then feeding the dried PBT resin and the mixed material into a twin-screw extruder, extruding, cooling, and pelletizing to obtain a cold-resistant PBT plastic; wherein the temperature of the first zone of the twin-screw extruder is 180° C., the temperature of the second zone is 190° C., the temperature of the third zone is 190° C., the temperature of the fourth zone is 190° C., the die head is 200° C., the main engine speed is 350 r / min, and the pressure is 12 MPa; The cold-resistant modifier is prepared by the following method: Step A1: 2.47 g of maleic anhydride, 40 mL of toluene and 2 g of 5-amino-1-pentanol were mixed, stirred for reaction for 30 min, then 3.06 g of cyanuric chloride and 10 mL of tetrahydrofuran were added, stirred in an ice-water bath for 5 min, 3.12 g of triethylamine was added, reacted for 10 min, washed, dried, filtered, and rotary evaporated to obtain product a; Step A2: 2.25 g of 1,5-pentanediol and 5 g of 1,6-hexamethylene diisocyanate were mixed, stirred at room temperature for 1 hour, and then 0.8 g of product a was added and stirred at room temperature for 30 minutes to obtain a polyurethane monomer; Step A3: dodecylbenzenesulfonic acid and 45 mL of deionized water were mixed, the temperature was raised to 45°C, and the mixture was stirred evenly. Then, 3 mol of decamethylcyclopentasiloxane and 5 mol of 3-trimethoxysilane acrylate were slowly added dropwise, the mixture was mixed evenly, and the mixture was reacted for 3 h. The mixture was cooled to room temperature to obtain product b. The amount of dodecylbenzenesulfonic acid used was 1.4% of the total amount of deionized water in the system. Step A4: 4g of ethyl acrylate, 0.15g of allyl methacrylate, 0.5g of sodium dodecyl sulfate, 0.05g of ammonium persulfate, 0.05g of sodium bicarbonate, 100g of deionized water and 3g of product b were mixed, the temperature was raised to 75°C, and after reacting for 30min, 15g of polyurethane monomer and 0.35g of ammonium persulfate were slowly added dropwise, and the reaction was continued for 2h. The mixture was protected by nitrogen and the pH was adjusted to 8. The mixture was heated to 80°C, 12g of methyl methacrylate, 3g of hydroxyethyl acrylate and 0.1g of ammonium persulfate were added, and the reaction was continued for 2.5h. The mixture was frozen, thawed and demulsified, and dried at 60°C for 12h to obtain a cold-resistant modifier; The modified flame retardant is prepared by the following method: Step B1: 20 mL of glacial acetic acid and 50 mL of deionized water were mixed evenly, heated to 80°C, and then 1.5 mol of methylvinyldimethoxysilane was added dropwise, and the addition time was controlled to be 15 min. The mixture was stirred at a constant temperature of 80°C for 2 h, cooled, filtered, and then 20 mL of xylene and 1 mol of phenylboric acid were added. The reaction was continued at 100°C for 5 h. After the reaction was completed, the mixture was washed with water until neutral, and vacuum filtered to obtain an intermediate. Step B2: 0.15 mol 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 40 mL N,N-dimethylformamide and 0.03 mol of the intermediate were mixed, stirred at 150° C. for 9 h, filtered, washed, and vacuum dried at 60° C. for 24 h to obtain a modified flame retardant. Example

[0014] A cold-resistant PBT plastic and a preparation method thereof, specifically comprising the following steps: Step S1: weighing raw materials by weight, 95 parts of PBT resin, 8 parts of cold-resistant modifier (prepared in this embodiment), 15 parts of modified flame retardant (prepared in this embodiment), 0.5 parts of antioxidant, 7 parts of compatibilizer, and 1.1 parts of lubricant; adding the modified flame retardant and antioxidant 412S into a high-speed mixer, mixing at a speed of 350 r / min for 15 minutes, and then adding polyethylene wax, styrene-acrylonitrile-methacrylate hydroglycerol and cold-resistant modifier and mixing for 7 minutes to obtain a mixed material; Step S2: drying the PBT resin at 125° C. for 2.5 h, and then feeding the dried PBT resin and the mixed material into a twin-screw extruder, extruding, cooling, and pelletizing to obtain a cold-resistant PBT plastic; wherein the temperature of the first zone of the twin-screw extruder is 195° C., the temperature of the second zone is 205° C., the temperature of the third zone is 205° C., the temperature of the fourth zone is 205° C., the die head is 210° C., the main engine speed is 400 r / min, and the pressure is 14 MPa; The cold-resistant modifier is prepared by the following method: Step A1: 2.71 g of maleic anhydride, 45 mL of toluene and 2 g of 5-amino-1-pentanol were mixed, stirred for reaction for 30 min, 3.48 g of cyanuric chloride and 10 mL of tetrahydrofuran were added, stirred in an ice-water bath for 5 min, 3.85 g of triethylamine was added, reacted for 10 min, washed, dried, filtered, and rotary evaporated to obtain product a; Step A2: 2.25 g of 1,5-pentanediol and 5.7 g of 1,6-hexamethylene diisocyanate were mixed, stirred at room temperature for 1 hour, and then 1 g of product a was added and stirred at room temperature for 30 minutes to obtain a polyurethane monomer; Step A3: dodecylbenzenesulfonic acid and 45 mL of deionized water were mixed, the temperature was raised to 45°C, and the mixture was stirred evenly. Then, 4 mol of decamethylcyclopentasiloxane and 6 mol of 3-trimethoxysilane acrylate were slowly added dropwise, the mixture was mixed evenly, and the mixture was reacted for 3 h. The mixture was cooled to room temperature to obtain product b. The amount of dodecylbenzenesulfonic acid used was 1.4% of the total amount of deionized water in the system. Step A4: 5g of ethyl acrylate, 0.2g of allyl methacrylate, 0.5g of sodium dodecyl sulfate, 0.05g of ammonium persulfate, 0.05g of sodium bicarbonate, 100g of deionized water and 3g of product b were mixed, the temperature was raised to 75°C, and after reacting for 30min, 22g of polyurethane monomer and 0.35g of ammonium persulfate were slowly added dropwise, and the reaction was continued for 2h. Nitrogen was passed through for protection, and the pH was adjusted to 9. The temperature was raised to 80°C, 14g of methyl methacrylate, 3g of hydroxyethyl acrylate and 0.1g of ammonium persulfate were added, and the reaction was continued for 2.5h. The mixture was frozen, thawed and demulsified, and dried at 60°C for 12h to obtain a cold-resistant modifier; The modified flame retardant is prepared by the following method: Step B1: 25 mL of glacial acetic acid and 50 mL of deionized water were mixed evenly, heated to 80°C, and then 1.7 mol of methylvinyldimethoxysilane was added dropwise, and the addition time was controlled to be 15 min. The mixture was stirred at a constant temperature of 80°C for 2 h, cooled, filtered, and then 33 mL of xylene and 1 mol of phenylboric acid were added. The reaction was continued at 100°C for 5 h. After the reaction was completed, the mixture was washed with water until neutral, and vacuum filtered to obtain an intermediate. Step B2: 0.20 mol 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 50 mL N,N-dimethylformamide and 0.04 mol of the intermediate were mixed, stirred at 150° C. for 9 h, filtered, washed, and vacuum dried at 60° C. for 24 h to obtain a modified flame retardant. Example

[0015] A cold-resistant PBT plastic and a preparation method thereof, specifically comprising the following steps: Step S1: weighing raw materials by weight, 100 parts of PBT resin, 15 parts of cold-resistant modifier (prepared in this embodiment), 25 parts of modified flame retardant (prepared in this embodiment), 1 part of antioxidant, 12 parts of compatibilizer, and 2 parts of lubricant; adding the modified flame retardant and antioxidant 412S into a high-speed mixer, mixing at a speed of 500 r / min for 20 minutes, and then adding polyethylene wax, styrene-acrylonitrile-methacrylate hydroglycerol and cold-resistant modifier and mixing for 10 minutes to obtain a mixed material; Step S2: drying the PBT resin at 150° C. for 2-3 hours, and then feeding the dried PBT resin and the mixed material into a twin-screw extruder for extrusion, cooling, and pelletizing to obtain a cold-resistant PBT plastic; wherein the temperature of the first zone of the twin-screw extruder is 210° C., the temperature of the second zone is 220° C., the temperature of the third zone is 220° C., the temperature of the fourth zone is 220° C., the die head is 220° C., the main engine speed is 450 r / min, and the pressure is 18 MPa; The cold-resistant modifier is prepared by the following method: Step A1: 2.96 g of maleic anhydride, 50 mL of toluene and 2 g of 5-amino-1-pentanol were mixed, stirred for reaction for 30 min, then 4.01 g of cyanuric chloride and 10 mL of tetrahydrofuran were added, stirred in an ice-water bath for 5 min, 4.58 g of triethylamine was added, reacted for 10 min, washed, dried, filtered, and rotary evaporated to obtain product a; Step A2: 2.25 g of 1,5-pentanediol and 6.4 g of 1,6-hexamethylene diisocyanate were mixed, stirred at room temperature for 1 hour, and then 1.2 g of product a was added and stirred at room temperature for 30 minutes to obtain a polyurethane monomer; Step A3: dodecylbenzenesulfonic acid and 45 mL of deionized water were mixed, the temperature was raised to 45°C, and the mixture was stirred evenly. Then, 5 mol of decamethylcyclopentasiloxane and 7 mol of 3-trimethoxysilane acrylate were slowly added dropwise, the mixture was mixed evenly, and the mixture was reacted for 3 h. The mixture was cooled to room temperature to obtain product b. The amount of dodecylbenzenesulfonic acid used was 1.4% of the total amount of deionized water in the system. Step A4: 6 g of ethyl acrylate, 0.25 g of allyl methacrylate, 0.5 g of sodium dodecyl sulfate, 0.05 g of ammonium persulfate, 0.05 g of sodium bicarbonate, 100 g of deionized water and 3 g of product b were mixed, the temperature was raised to 75°C, and after reacting for 30 min, 30 g of polyurethane monomer and 0.35 g of ammonium persulfate were slowly added dropwise, and the reaction was continued for 2 h. The mixture was protected by nitrogen and the pH was adjusted to 10. The mixture was heated to 80°C, 16 g of methyl methacrylate, 3 g of hydroxyethyl acrylate and 0.1 g of ammonium persulfate were added, and the reaction was continued for 2.5 h. The mixture was frozen, thawed and demulsified, and dried at 60°C for 12 h to obtain a cold-resistant modifier. The modified flame retardant is prepared by the following method: Step B1: 30 mL of glacial acetic acid and 50 mL of deionized water were mixed evenly, heated to 80°C, and then 2 mol of methylvinyldimethoxysilane was added dropwise, and the addition time was controlled to be 15 min. The mixture was stirred at a constant temperature of 80°C for 2 h, cooled, filtered, and then 45 mL of xylene and 1 mol of phenylboric acid were added. The reaction was continued at 100°C for 5 h. After the reaction was completed, the mixture was washed with water until neutral, and vacuum filtered to obtain an intermediate. Step B2: 0.25 mol 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 60 mL N,N-dimethylformamide and 0.05 mol of the intermediate were mixed, stirred at 150° C. for 9 h, filtered, washed, and vacuum dried at 60° C. for 24 h to obtain a modified flame retardant.

[0016] Comparative Example 1 This comparative example is a cold-resistant PBT plastic. The difference from Example 3 is that an equal amount of toughening agent S-2030 is used to replace the cold-resistant modifier prepared in Example 3, and the rest is the same.

[0017] Comparative Example 2 This comparative example is a cold-resistant PBT plastic. The difference from Example 3 is that an equal amount of modified flame retardant magnesium hydroxide is used to replace the modified flame retardant prepared in Example 3, and the rest are the same.

[0018] Performance test: The cold-resistant PBT plastics obtained in Examples 1-3 and Comparative Examples 1-2 were cut into standard test sizes, and subjected to bending strength tests at 25°C and -40°C respectively according to ASTM D790-2003 standard; placed in an oven at 23°C and -40°C for 4 hours, and subjected to notched impact strength tests according to ASTMD-256 standard; vertical burning performance was tested using GB / T2048-1996 plastic burning performance test method; the test results are shown in the following table: It can be seen from the test data in the table that the cold-resistant PBT plastic prepared in Example 1 still has more than 70% of the bending strength and impact resistance at room temperature at a temperature of -40°C, and has excellent low-temperature toughness. It can also be seen from the above table that the cold-resistant PBT plastic prepared in the present invention has a good flame retardant effect.

[0019] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing cold-resistant PBT plastic, characterized in that: The following steps are involved: Step S1: weighing raw materials by weight, 90-100 parts of PBT resin, 2-15 parts of cold-resistant modifier, 5-25 parts of modified flame retardant, 0.1-1 parts of antioxidant, 2-12 parts of compatibilizer, and 0.1-2 parts of lubricant; adding the modified flame retardant and antioxidant into a high-speed mixer, mixing at a speed of 200-500r / min for 10-20min, then adding the lubricant, compatibilizer and cold-resistant modifier and mixing for 5-10min to obtain a mixed material; Step S2: drying the PBT resin at 100-150°C for 2-3h, and then feeding the dried PBT resin and the mixed material into a twin-screw extruder for extrusion, cooling, and pelletizing to obtain a cold-resistant PBT plastic; wherein the temperature of the first zone of the twin-screw extruder is 180-210°C, the temperature of the second zone is 190-220°C, the temperature of the third zone is 190-220°C, the temperature of the fourth zone is 190-220°C, the head is 200-220°C, the main engine speed is 350-450r / min, and the pressure is 12-18MPa.

2. The method for preparing a cold-resistant PBT plastic according to claim 1, characterized in that: The cold-resistant modifier is prepared by the following method: Step A1: maleic anhydride, toluene and 5-amino-1-pentanol were mixed, stirred for reaction for 30 minutes, cyanuric chloride and tetrahydrofuran were added, stirred in an ice-water bath for 5 minutes, triethylamine was added, reacted for 10 minutes, washed, dried, filtered, and rotary evaporated to obtain product a; Step A2: 1,5-pentanediol and 1,6-hexamethylene diisocyanate were mixed, stirred at room temperature for 1 hour, and then product a was added and stirred at room temperature for 30 minutes to obtain a polyurethane monomer; Step A3: dodecylbenzenesulfonic acid and deionized water were mixed, the temperature was raised to 45°C, and the mixture was stirred evenly. Then, decamethylcyclopentasiloxane and 3-trimethoxysilane acrylate were slowly added dropwise, the mixture was mixed evenly, and the mixture was reacted for 3 hours. The mixture was cooled to room temperature to obtain product b. Step A4: Ethyl acrylate, allyl methacrylate, sodium dodecyl sulfate, 0.05 g ammonium persulfate, sodium bicarbonate, deionized water and product b are mixed, the temperature is raised to 75°C, and the reaction is carried out for 30 minutes. Then, polyurethane monomer and 0.35 g ammonium persulfate are slowly added dropwise, and the reaction is carried out for 2 hours. Nitrogen protection is passed, the pH is adjusted to 8-10, the temperature is raised to 80°C, methyl methacrylate, hydroxyethyl acrylate and 0.1 g ammonium persulfate are added, and the reaction is carried out for 2.5 hours. After freezing, thawing and demulsification, and drying at 60°C for 12 hours, a cold-resistant modifier is obtained.

3. The method for preparing a cold-resistant PBT plastic according to claim 2, characterized in that: In step A1, the usage ratio of maleic anhydride, toluene, 5-amino-1-pentanol, cyanuric chloride, tetrahydrofuran and triethylamine is 2.47-2.96 g: 40-50 mL: 2 g: 3.06-4.01 g: 10 mL: 3.12-4.58 g.

4. The method for preparing a cold-resistant PBT plastic according to claim 2, characterized in that: In step A2, the mass ratio of 1,5-pentanediol, 1,6-hexamethylene diisocyanate, and product a is 2.25 g: 5-6.4 g: 0.8-1.2 g.

5. The method for preparing a cold-resistant PBT plastic according to claim 2, characterized in that: In step A3, the usage ratio of deionized water, decamethylcyclopentasiloxane, and 3-trimethoxysilane propyl acrylate is 45 mL: 3-5 mol: 5-7 mol, and the usage of dodecylbenzenesulfonic acid accounts for 1.4% of the total amount of deionized water in the system.

6. The method for preparing a cold-resistant PBT plastic according to claim 2, characterized in that: In step A4, the mass ratio of ethyl acrylate, allyl methacrylate, sodium dodecyl sulfate, sodium bicarbonate, deionized water, product b, polyurethane monomer, methyl methacrylate, and hydroxyethyl acrylate is 4-6g: 0.15-0.25g: 0.5g: 0.05g: 100g: 3g: 15-30g: 12-16g: 3g.

7. The method for preparing a cold-resistant PBT plastic according to claim 1, characterized in that: The modified flame retardant is prepared by the following method: Step B1: Mix glacial acetic acid and deionized water evenly, heat to 80°C, then drop methylvinyldimethoxysilane, control the dropping time to 15min, stir at 80°C for 2h, cool, filter, then add xylene and phenylboric acid, continue to react at 100°C for 5h, wash with water until neutral after the reaction, and vacuum filter to obtain an intermediate; Step B2: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, N,N-dimethylformamide and the intermediate are mixed, stirred at 150° C. for 9 hours, filtered, washed, and vacuum dried at 60° C. for 24 hours to obtain a modified flame retardant.

8. The method for preparing cold-resistant PBT plastic according to claim 7, characterized in that: In step B1, the usage ratio of glacial acetic acid, deionized water, methylvinyldimethoxysilane, xylene and phenylboric acid is: 20-30mL: 50mL: 1.5-2mol: 20-45mL: 1mol.

9. The method for preparing a cold-resistant PBT plastic according to claim 7, characterized in that: In step B2, the usage ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, N,N-dimethylformamide and the intermediate is 0.15-0.25 mol:40-60 mL:0.03-0.05 mol.

10. The method for preparing cold-resistant PBT plastic according to claim 1, characterized in that: The antioxidant is antioxidant 412S, the compatibilizer is styrene-acrylonitrile-methacrylate glycerol, and the lubricant is polyethylene wax. A cold-resistant PBT plastic, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

Images