Special high-temperature-resistant composite additive for PPR (polypropylene random copolymer) pipe and preparation method thereof

Abstract

The invention relates to the field of PPR pipe aids, in particular to a special high-temperature-resistant composite aid for a PPR pipe and a preparation method of the special high-temperature-resistant composite aid, which are used for solving the problems that an existing PPR pipe high-temperature-resistant aid is large in addition amount, high in cost and incapable of achieving a good high-temperature-resistant effect. Under the synergistic effect of the heat-resistant enhancer, the modified heat-resistant filler, the modified heat-conducting filler, the nucleating agent and the antioxidant, the composite additive can significantly improve the high-temperature resistance of the PPR pipe at a low addition amount, and also can enhance the mechanical properties of the PPR pipe; under the action of the compound antioxidant, the oxidative degradation of the PPR pipe at high temperature is effectively inhibited, the high temperature resistance of the PPR pipe is further improved, the service life of the PPR pipe is remarkably prolonged, the maintenance and replacement cost of the PPR pipe in the use process is reduced, and the preparation method is simple to operate, easy to control and suitable for industrial production. The method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the field of PPR pipe additives, and particularly to a special high-temperature resistant composite additive for PPR pipes and a preparation method thereof. Background Art

[0002] Due to advantages such as corrosion resistance, long service life, and convenient installation, PPR pipes have been widely used in fields such as building water supply and drainage, urban and rural water supply and drainage, urban gas transmission, power and optical cable sheaths, and industrial fluid transmission. However, PPR pipes themselves have the defect of poor high-temperature resistance. In a high-temperature environment, the mechanical properties of PPR pipes will drop sharply, and problems such as deformation and cracking are likely to occur, which greatly limits their application in high-temperature scenarios.

[0003] To improve the high-temperature resistance of PPR pipes, currently, the method of adding various additives to PPR pipes is mainly adopted. However, the existing high-temperature resistant additives have a large addition amount, which will seriously affect the comprehensive performance of PPR pipes. Not only is the cost high, but also a good high-temperature resistant effect cannot be achieved, and the actual use requirements cannot be met. Therefore, it is of great practical significance to develop a special high-temperature resistant composite additive for PPR pipes and a preparation method thereof. Summary of the Invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide a special high-temperature resistant composite additive for PPR pipes and a preparation method thereof, which solves the problems that the existing high-temperature resistant additives for PPR pipes have a large addition amount, seriously affect the comprehensive performance of PPR pipes, have a high additive cost, and cannot achieve a good high-temperature resistant effect and cannot meet the actual use requirements.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A special high-temperature resistant composite additive for PPR pipes, comprising the following components in parts by weight: 20 - 25 parts of heat-resistant enhancer, 7 - 15 parts of modified heat-resistant filler, 11 - 23 parts of modified heat-conducting filler, 10 - 12 parts of nucleating agent, and 9 - 13 parts of antioxidant; Among them, the heat-resistant enhancer is prepared by the following steps: Step a1: Add p-hydroxybenzaldehyde, triethylamine, and ethyl acetate into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 20 - 30 min under the conditions of a temperature of -5 - 0 °C and a stirring rate of 200 - 300 r / min. Then, while stirring, gradually add a phenyl dichlorophosphate solution dropwise, controlling the dropping rate at 1 - 2 drops / s. After the addition is complete, raise the temperature to 25 - 30 °C and continue stirring and reacting for 2 - 3 h. Then, raise the temperature to 40 - 45 °C and continue stirring and reacting for 8 - 10 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filtrate with saturated brine and distilled water 2 - 3 times in sequence, then dry it with anhydrous sodium sulfate, and then perform vacuum filtration again. Rotate-evaporate the filtrate to remove the solvent to obtain a dialdehyde intermediate; Step a2: Add 2-amino-1,3,4-thiadiazole and N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 20 - 30 min under the conditions of a temperature of 25 - 30 °C and a stirring rate of 200 - 300 r / min. Then, add the dialdehyde intermediate and raise the temperature to 80 - 85 °C and continue stirring and reacting for 8 - 10 h. Then, add DOPO and continue stirring and reacting for 10 - 15 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filter cake with absolute ethanol and distilled water 2 - 3 times in sequence, and then place it in a vacuum drying oven and dry it at a temperature of 80 - 85 °C for 2 - 3 h to obtain a heat-resistant enhancer.

[0006] As a further scheme of the present invention: The dosage ratio of the p-hydroxybenzaldehyde, triethylamine, ethyl acetate, and phenyl dichlorophosphate solution in step a1 is 22 mmol: 25 - 30 mmol: 50 - 55 mL: 20 - 22 mL.

[0007] As a further scheme of the present invention: The phenyl dichlorophosphate solution in step a1 is a solution formed by dissolving phenyl dichlorophosphate in ethyl acetate according to 10 mmol: 20 mL.

[0008] As a further scheme of the present invention: The dosage ratio of the 2-amino-1,3,4-thiadiazole, N,N-dimethylformamide, dialdehyde intermediate, and DOPO in step a2 is 20 mmol: 60 - 70 mL: 10 mmol: 20 mmol.

[0009] As a further scheme of the present invention: The modified heat-resistant filler is prepared by the following steps: Add alumina and ethanol solution into a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 10 - 15 min under the condition that the ultrasonic frequency is 30 - 40 kHz. Then adjust the pH to 5 - 6 with acetic acid, and continue to ultrasonically disperse for 8 - 10 min. Then add silane coupling agent KH-792 and stir and react for 20 - 30 min under the conditions that the temperature is 25 - 30 °C and the stirring rate is 200 - 300 r / min. Then raise the temperature to 80 - 85 °C and continue to stir and react for 5 - 6 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with distilled water 2 - 3 times, and then place it in a vacuum drying oven and dry for 2 - 3 h under the condition that the temperature is 90 - 100 °C to obtain the modified heat-resistant filler.

[0010] As a further scheme of the present invention: the dosage ratio of the alumina, the ethanol solution and the silane coupling agent KH-792 is 10 g : 60 - 70 mL : 0.7 - 2.5 g.

[0011] As a further scheme of the present invention: the volume fraction of the ethanol solution is 80 - 85%; the average particle size of the alumina is 5 μm.

[0012] As a further scheme of the present invention: the modified thermal conductive filler is prepared by the following steps: Add aluminum nitride, absolute ethanol and deionized water into a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 30 - 40 min under the condition that the ultrasonic frequency is 30 - 40 kHz. Then adjust the pH to 4 - 5 with acetic acid, and then add titanate coupling agent LD-144 and stir and react for 5 - 10 min under the conditions that the temperature is 25 - 30 °C and the stirring rate is 200 - 300 r / min. Then raise the temperature to 80 - 85 °C and continue to stir and react for 4 - 5 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with distilled water 2 - 3 times, and then place it in a vacuum drying oven and dry for 3 - 5 h under the condition that the temperature is 70 - 80 °C to obtain the modified thermal conductive filler.

[0013] As a further scheme of the present invention: the dosage ratio of the aluminum nitride, the absolute ethanol, the deionized water and the titanate coupling agent LD-144 is 5 g : 80 - 90 mL : 10 - 15 mL : 0.6 - 2.2 g.

[0014] As a further scheme of the present invention: the average particle size of the aluminum nitride is 2 μm.

[0015] As a further scheme of the present invention: a preparation method of a high-temperature resistant composite auxiliary for PPR pipes comprises the following steps: Step 1: Weigh 20 - 25 parts of heat-resistant enhancer, 7 - 15 parts of modified heat-resistant filler, 11 - 23 parts of modified heat-conducting filler, 10 - 12 parts of nucleating agent, and 9 - 13 parts of antioxidant by weight, and set aside. Step 2: Add the heat-resistant enhancer, modified heat-resistant filler, modified heat-conducting filler, nucleating agent, and antioxidant into a high-speed mixer, and stir and mix for 10 - 20 min under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0016] As a further scheme of the present invention: The nucleating agent is ADK STAB NA-11 nucleating agent.

[0017] As a further scheme of the present invention: The antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2.

[0018] Beneficial effects of the present invention: A high-temperature resistant composite additive special for PPR pipes and a preparation method thereof according to the present invention obtain a high-temperature resistant composite additive special for PPR pipes by stirring and mixing a heat-resistant enhancer, a modified heat-resistant filler, a modified heat-conducting filler, a nucleating agent, and an antioxidant; the composite additive, under the heat-resistant structure network jointly formed by the heat-resistant enhancer and the modified heat-resistant filler, the heat dissipation effect of the modified heat-conducting filler, the crystallization-promoting effect of the nucleating agent, and the antioxidant effect of the antioxidant, can significantly improve the high-temperature resistance of PPR pipes at a low addition amount, and can also enhance the mechanical properties of PPR pipes, and effectively inhibits the oxidative degradation of PPR pipes at high temperatures under the action of the composite antioxidant, further improving the high-temperature resistance of PPR pipes, and significantly extending the service life of PPR pipes, reducing the maintenance and replacement costs of PPR pipes during use. Moreover, the preparation method is simple to operate, easy to control, and suitable for large-scale industrial production.

[0019] In the process of preparing a high-temperature resistant composite additive special for PPR pipes, a heat-resistant enhancer was first prepared. First, p-hydroxybenzaldehyde and phenyl dichlorophosphate were reacted, and the hydroxyl group on p-hydroxybenzaldehyde reacted with the chlorine atom on phenyl dichlorophosphate to obtain a bis-aldehyde intermediate. Then, 2-amino-1,3,4-thiadiazole and the bis-aldehyde intermediate reacted, and the amino group on 2-amino-1,3,4-thiadiazole reacted with the aldehyde group on the bis-aldehyde intermediate to form a Schiff base structure. Then, it reacted with DOPO, and the Schiff base structure underwent an addition reaction with the P-H on DOPO to introduce the DOPO structure, obtaining the heat-resistant enhancer. The molecular structure of this heat-resistant enhancer contains a large number of cyclic structures, endowing it with excellent high-temperature stability. Moreover, the molecular structure of the heat-resistant enhancer also contains a large amount of organic phosphorus, nitrogen, and sulfur, further enhancing its high-temperature resistance and endowing it with excellent flame retardant and fire prevention properties. Therefore, adding the heat-resistant enhancer to PPR pipes can significantly improve the high-temperature resistance of PPR pipes.

[0020] In the process of preparing a high-temperature resistant composite additive special for PPR pipes, a modified heat-resistant filler was also prepared. Alumina was modified with silane coupling agent KH-792 to obtain the modified heat-resistant filler. Alumina is an inorganic material with a high melting point and good chemical stability. After modification, the dispersibility of alumina can be greatly improved, avoiding its agglomeration and enabling it to be evenly dispersed in PPR pipes, so as to fully exert its strengthening effect. At high temperatures, alumina can absorb and disperse heat, reducing the accumulation of heat inside the pipes, thereby lowering the temperature of the pipes, and then endowing the modified heat-resistant filler with heat-resistant properties. Therefore, adding the modified heat-resistant filler to PPR pipes can cooperate with the heat-resistant enhancer to further improve the high-temperature resistance of PPR pipes.

[0021] In the process of preparing a high-temperature resistant composite additive special for PPR pipes, a modified heat-conducting filler was also prepared. Aluminum nitride was modified with titanate coupling agent LD-144 to obtain the modified heat-conducting filler. Aluminum nitride has excellent heat-conducting properties. After modification, the dispersibility of aluminum nitride can be greatly improved, avoiding its agglomeration and enabling it to be evenly dispersed in PPR pipes, so as to fully exert its strengthening effect. When the modified heat-conducting filler is evenly dispersed in PPR pipes, it can form a heat-conducting channel inside the PPR pipes, enabling heat to be transferred quickly, making the temperature distribution inside the pipes more uniform, reducing the temperature gradient, and reducing the generation of thermal stress, thereby improving the high-temperature resistance of PPR pipes and also improving the mechanical properties of PPR pipes to a certain extent. Detailed implementation methods

[0022] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. Example 1

[0023] This embodiment is a preparation method of a special high-temperature resistant composite additive for PPR pipes, including the following steps: Step S1: Add 22 mmol of p-hydroxybenzaldehyde, 25 mmol of triethylamine, and 50 mL of ethyl acetate into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 20 min at a temperature of -5°C and a stirring rate of 200 r / min. Then, while stirring, gradually dropwise add a solution of 20 mL of phenyl dichlorophosphate dissolved in ethyl acetate according to 10 mmol:20 mL, control the dropping rate at 1 drop / s. After the dropping is completed, continue to stir and react at a temperature of 25°C for 2 h, and then continue to stir and react at a temperature of 40°C for 8 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filtrate with saturated brine and distilled water twice in sequence, then dry it with anhydrous sodium sulfate, and then perform vacuum filtration. Rotate and evaporate the filtrate to remove the solvent to obtain a bis-aldehyde intermediate; Step S2: Add 20 mmol of 2-amino-1,3,4-thiadiazole and 60 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube. Pass in nitrogen for protection. Stir and react for 20 min at a temperature of 25°C and a stirring rate of 200 r / min. Then add 10 mmol of the bis-aldehyde intermediate and continue to stir and react at a temperature of 80°C for 8 h. Then add 20 mmol of DOPO and continue to stir and react for 10 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filter cake with absolute ethanol and distilled water twice in sequence, and then place it in a vacuum drying oven and dry it at a temperature of 80°C for 2 h to obtain a heat resistance enhancer; Step S3: Add 10 g of alumina with an average particle size of 5 μm and 60 mL of an ethanol solution with a volume fraction of 80% into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse for 10 min under the condition of an ultrasonic frequency of 30 kHz, then adjust the pH to 5 with acetic acid, then continue ultrasonic dispersion for 8 min, then add 0.7 g of silane coupling agent KH-792 and stir and react for 20 min under the conditions of a temperature of 25 °C and a stirring rate of 200 r / min. Then raise the temperature to 80 °C and continue stirring and reacting for 5 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate twice with distilled water, and then place it in a vacuum drying oven and dry for 2 h under the condition of a temperature of 90 °C to obtain a modified heat-resistant filler; Step S4: Add 5 g of aluminum nitride, 80 mL of absolute ethanol, and 10 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse for 30 min under the condition of an ultrasonic frequency of 30 kHz, then adjust the pH to 4 with acetic acid, then add 0.6 g of titanate coupling agent LD-144 with an average particle size of 2 μm and stir and react for 5 min under the conditions of a temperature of 25 °C and a stirring rate of 200 r / min. Then raise the temperature to 80 °C and continue stirring and reacting for 4 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate twice with distilled water, and then place it in a vacuum drying oven and dry for 3 h under the condition of a temperature of 70 °C to obtain a modified thermal conductive filler; Step S5: Weigh 20 parts of heat-resistant enhancer, 7 parts of modified heat-resistant filler, 11 parts of modified thermal conductive filler, 10 parts of nucleating agent, and 9 parts of antioxidant by weight for standby; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S6: Add the heat-resistant enhancer, modified heat-resistant filler, modified thermal conductive filler, nucleating agent, and antioxidant into a high-speed mixer and stir and mix for 10 min under the conditions of a temperature of 25 °C and a stirring rate of 800 r / min to obtain a high-temperature resistant composite additive special for PPR pipes. Example 2

[0024] This example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Add 22 mmol of p-hydroxybenzaldehyde, 28 mmol of triethylamine, and 52 mL of ethyl acetate into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir and react for 25 min at a temperature of -3°C and a stirring rate of 250 r / min. Then, while stirring, gradually add dropwise a phenyl dichlorophosphate solution formed by dissolving 21 mL of phenyl dichlorophosphate in ethyl acetate according to 10 mmol:20 mL, control the dropping rate at 1 drop / s. After the dropping is complete, continue to stir and react for 2.5 h at a temperature raised to 28°C. After the dropping is complete, continue to stir and react for 9 h at a temperature raised to 42°C. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filtrate with saturated brine and distilled water twice in sequence, then dry it with anhydrous sodium sulfate, and then perform vacuum filtration again. Rotate and evaporate the filtrate to remove the solvent to obtain a dialdehyde intermediate; Step S2: Add 20 mmol of 2-amino-1,3,4-thiadiazole and 65 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas pipe. Introduce nitrogen for protection. Stir and react for 25 min at a temperature of 28°C and a stirring rate of 250 r / min. Then add 10 mmol of the dialdehyde intermediate and continue to stir and react for 9 h at a temperature raised to 82°C. Then add 20 mmol of DOPO and continue to stir and react for 12 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filter cake with absolute ethanol and distilled water twice in sequence, and then place it in a vacuum drying oven and dry it for 2.5 h at a temperature of 82°C to obtain a heat-resistant enhancer; Step S3: Add 10 g of alumina with an average particle size of 5 μm and 65 mL of an ethanol solution with a volume fraction of 82% into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse for 12 min under the condition of an ultrasonic frequency of 35 kHz, then adjust the pH to 5.5 with acetic acid, and then continue to ultrasonically disperse for 9 min. Then add 1.6 g of silane coupling agent KH-792 and stir and react for 25 min at a temperature of 28°C and a stirring rate of 250 r / min. Then continue to stir and react for 5.5 h at a temperature raised to 82°C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with distilled water twice, and then place it in a vacuum drying oven and dry it for 2.5 h at a temperature of 95°C to obtain a modified heat-resistant filler; Step S4: Add 5 g of aluminum nitride, 85 mL of absolute ethanol, and 12 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Under the condition of an ultrasonic frequency of 35 kHz, ultrasonically disperse for 35 min. Then adjust the pH to 4.5 with acetic acid. After that, add 1.4 g of titanate coupling agent LD-144 with an average particle size of 2 μm and stir and react for 8 min under the conditions of a temperature of 28°C and a stirring rate of 250 r / min. Then raise the temperature to 82°C and continue to stir and react for 4.5 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate twice with distilled water, and then place it in a vacuum drying oven and dry it for 4 h under the condition of a temperature of 75°C to obtain the modified thermal conductive filler; Step S5: Weigh 22 parts by weight of heat-resistant enhancer, 11 parts of modified heat-resistant filler, 17 parts of modified thermal conductive filler, 11 parts of nucleating agent, and 11 parts of antioxidant, and set aside; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S6: Add the heat-resistant enhancer, modified heat-resistant filler, modified thermal conductive filler, nucleating agent, and antioxidant into a high-speed mixer and stir and mix for 15 min under the conditions of a temperature of 28°C and a stirring rate of 1000 r / min to obtain a high-temperature resistant composite additive special for PPR pipes. Example 3

[0025] This example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Add 22 mmol of p-hydroxybenzaldehyde, 30 mmol of triethylamine, and 55 mL of ethyl acetate into a three-necked flask equipped with a stirrer, a thermometer, and a constant pressure dropping funnel. Stir and react for 30 min under the conditions of a temperature of 0°C and a stirring rate of 300 r / min. Then, while stirring, gradually dropwise add a dichlorophenyl phosphate solution formed by dissolving 22 mL of dichlorophenyl phosphate in ethyl acetate according to 10 mmol:20 mL, control the dropping rate at 2 drops / s. After the dropping is completed, raise the temperature to 30°C and continue to stir and react for 3 h. After the dropping is completed, raise the temperature to 45°C and continue to stir and react for 10 h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, wash the filtrate three times with saturated brine and distilled water in sequence, then dry it with anhydrous sodium sulfate, then vacuum filter, and rotate and evaporate the filtrate to remove the solvent to obtain a dialdehyde intermediate; Step S2: Add 20 mmol of 2-amino-1,3,4-thiadiazole and 70 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a gas guide tube. Introduce nitrogen for protection. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then add 10 mmol of the dialdehyde intermediate and continue to stir and react for 10 h under the condition of heating to 85 °C. Then add 20 mmol of DOPO and continue to stir and react for 15 h. After the reaction is completed, cool the reaction product to room temperature. Then perform vacuum filtration. Wash the filter cake with absolute ethanol and distilled water three times each. Then place it in a vacuum drying oven and dry it at a temperature of 85 °C for 3 h to obtain a heat resistance enhancer; Step S3: Add 10 g of alumina with an average particle size of 5 μm and 70 mL of an ethanol solution with a volume fraction of 85% into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse for 15 min under the condition of an ultrasonic frequency of 40 kHz. Then adjust the pH to 6 with acetic acid. Then continue to ultrasonically disperse for 10 min. Then add 2.5 g of the silane coupling agent KH-792 and stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then continue to stir and react for 6 h under the condition of heating to 85 °C. After the reaction is completed, cool the reaction product to room temperature. Then centrifuge. Wash the precipitate with distilled water three times. Then place it in a vacuum drying oven and dry it at a temperature of 100 °C for 3 h to obtain a modified heat-resistant filler; Step S4: Add 5 g of aluminum nitride, 90 mL of absolute ethanol, and 15 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse for 40 min under the condition of an ultrasonic frequency of 40 kHz. Then adjust the pH to 5 with acetic acid. Then add 2.2 g of the titanate coupling agent LD-144 with an average particle size of 2 μm and stir and react for 10 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then continue to stir and react for 5 h under the condition of heating to 85 °C. After the reaction is completed, cool the reaction product to room temperature. Then centrifuge. Wash the precipitate with distilled water three times. Then place it in a vacuum drying oven and dry it at a temperature of 80 °C for 5 h to obtain a modified thermal conductive filler; Step S5: Weigh 25 parts of the heat resistance enhancer, 15 parts of the modified heat-resistant filler, 23 parts of the modified thermal conductive filler, 12 parts of the nucleating agent, and 13 parts of the antioxidant by weight and set aside; the nucleating agent is the ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S6: Add the heat-resistant enhancer, modified heat-resistant filler, modified thermal conductive filler, nucleating agent, and antioxidant into a high-speed mixer, and stir and mix for 20 min under the conditions of a temperature of 30°C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0026] Comparative Example 1: This comparative example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Weigh 12 parts by weight of a nucleating agent and 13 parts by weight of an antioxidant for standby; the nucleating agent is ADK STABNA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S2: Add the nucleating agent and antioxidant into a high-speed mixer, and stir and mix for 20 min under the conditions of a temperature of 30°C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0027] Comparative Example 2: This comparative example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Add 22 mmol of p-hydroxybenzaldehyde, 30 mmol of triethylamine, and 55 mL of ethyl acetate into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel, stir and react for 30 min under the conditions of a temperature of 0°C and a stirring rate of 300 r / min, and then gradually add dropwise a dichlorophenyl phosphate solution formed by dissolving 22 mL of dichlorophenyl phosphate in ethyl acetate according to 10 mmol:20 mL while stirring, control the dropping rate at 2 drops / s, continue to stir and react for 3 h under the condition of heating to 30°C after the dropping is completed, continue to stir and react for 10 h under the condition of heating to 45°C after the dropping is completed, cool the reaction product to room temperature after the reaction is completed, then carry out vacuum filtration, wash the filtrate with saturated brine and distilled water 3 times in sequence, then dry with anhydrous sodium sulfate, then carry out vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain a dialdehyde intermediate; Step S2: Add 20 mmol of 2-amino-1,3,4-thiadiazole and 70 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a gas pipe. Introduce nitrogen for protection. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then add 10 mmol of the dialdehyde intermediate and continue to stir and react for 10 h under the condition of heating to 85 °C. Then add 20 mmol of DOPO and continue to stir and react for 15 h. After the reaction is completed, cool the reaction product to room temperature, then carry out vacuum filtration. Wash the filter cake with absolute ethanol and distilled water three times respectively. Then place it in a vacuum drying oven and dry it for 3 h under the condition of a temperature of 85 °C to obtain a heat resistance enhancer; Step S3: Weigh 25 parts of the heat resistance enhancer, 12 parts of the nucleating agent and 13 parts of the antioxidant by weight for standby; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010 and antioxidant 1330 in a mass ratio of 3:1:2; Step S4: Add the heat resistance enhancer, the nucleating agent and the antioxidant into a high-speed mixer, and stir and mix for 20 min under the conditions of a temperature of 30 °C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0028] Comparative Example 3: This comparative example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Add 10 g of alumina with an average particle size of 5 μm and 70 mL of an ethanol solution with a volume fraction of 85% into a three-necked flask equipped with a stirrer and a thermometer. Carry out ultrasonic dispersion for 15 min under the condition of an ultrasonic frequency of 40 kHz. Then adjust the pH to 6 with acetic acid, and then continue ultrasonic dispersion for 10 min. Then add 2.5 g of silane coupling agent KH-792 and stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then continue to stir and react for 6 h under the condition of heating to 85 °C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with distilled water three times. Then place it in a vacuum drying oven and dry it for 3 h under the condition of a temperature of 100 °C to obtain a modified heat-resistant filler; Step S2: Weigh 15 parts of the modified heat-resistant filler, 12 parts of the nucleating agent and 13 parts of the antioxidant by weight for standby; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010 and antioxidant 1330 in a mass ratio of 3:1:2; Step S3: Add the modified heat-resistant filler, nucleating agent, and antioxidant into a high-speed mixer, and stir and mix them for 20 min under the conditions of a temperature of 30°C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0029] Comparative Example 4: This comparative example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Add 5 g of aluminum nitride, 90 mL of absolute ethanol, and 15 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer, ultrasonically disperse them for 40 min under the condition of an ultrasonic frequency of 40 kHz, then adjust the pH to 5 with acetic acid, then add 2.2 g of titanate coupling agent LD-144 with an average particle size of 2 μm and stir and react for 10 min under the conditions of a temperature of 30°C and a stirring rate of 300 r / min, then continue to stir and react for 5 h under the condition of heating to 85°C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with distilled water 3 times, and then place it in a vacuum drying oven and dry it for 5 h under the condition of a temperature of 80°C to obtain a modified heat-conducting filler; Step S2: Weigh 23 parts of the modified heat-conducting filler, 12 parts of the nucleating agent, and 13 parts of the antioxidant by weight and set aside; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S3: Add the modified heat-conducting filler, nucleating agent, and antioxidant into a high-speed mixer, and stir and mix them for 20 min under the conditions of a temperature of 30°C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0030] Comparative Example 5: This comparative example is a preparation method of a high-temperature resistant composite additive special for PPR pipes, including the following steps: Step S1: Weigh 25 parts of polyphosphoric acid, 15 parts of alumina, 23 parts of aluminum nitride, 12 parts of the nucleating agent, and 13 parts of the antioxidant by weight and set aside; the nucleating agent is ADK STAB NA-11 nucleating agent; the antioxidant is a mixture of antioxidant 168, antioxidant 1010, and antioxidant 1330 in a mass ratio of 3:1:2; Step S2: Add polyphosphoric acid, alumina, aluminum nitride, nucleating agent, and antioxidant into a high-speed mixer, and stir and mix them for 20 min under the conditions of a temperature of 30°C and a stirring rate of 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

[0031] Performance Test The high-temperature resistant composite additives special for PPR pipes in Examples 1-3 and Comparative Examples 1-5 were added to random copolymer polypropylene resin (PP RP2400 from Korea Petrochemical) at an addition amount of 1.6 wt%, and then added to a twin-screw extruder. Melting extrusion molding was carried out under the conditions that the temperature of the first zone was 170 °C, the temperature of the second zone was 190 °C, the temperature of the third zone was 210 °C, the temperature of the fourth zone was 230 °C, the temperature of the die head was 240 °C, and the screw speed was 250 r / min. After water cooling and cutting, PPR pipe samples with a diameter of 20 mm, a wall thickness of 2.8 mm, and a length of 200 mm were obtained.

[0032] The thermal conductivity analyzer LW-9389 was used to analyze the thermal conductivity and test the thermal conductivity of the PPR pipe samples. The simultaneous thermal gravimetric and high-temperature differential thermal analyzer SDT2960 was used to conduct high-temperature thermogravimetric analysis and test the 5% thermal weight loss temperature of the PPR pipe samples.

[0033] The test results are shown in the following table:

[0034] Referring to the data in the above table, by comparing Examples 1-3 and Comparative Examples 1-5, it can be known that adding heat-resistant enhancers, modified heat-resistant fillers, and modified thermal conductive fillers can significantly improve the high-temperature resistance performance of PPR pipes.

[0035] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0036] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by this application, they should all belong to the protection scope of the present invention.

Claims

1. A special high-temperature resistant composite additive for PPR pipes, characterized in that, Comprising the following components in parts by weight: 20 - 25 parts of heat-resistant enhancer, 7 - 15 parts of modified heat-resistant filler, 11 - 23 parts of modified heat-conducting filler, 10 - 12 parts of nucleating agent, and 9 - 13 parts of antioxidant; Among them, the heat-resistant enhancer is prepared by the following steps: Step a1: Stir and react p-hydroxybenzaldehyde, triethylamine, and ethyl acetate, then dropwise add a solution of phenyl dichlorophosphate while stirring. After the addition is complete, continue stirring and reacting. After the reaction ends, cool the reaction product, then perform vacuum filtration. Wash and dry the filtrate, then perform vacuum filtration again, and rotary evaporate the filtrate to obtain a dialdehyde intermediate; Step a2: Stir and react 2-amino-1,3,4-thiadiazole and N,N-dimethylformamide, then add the dialdehyde intermediate and continue stirring and reacting, then add DOPO and continue stirring and reacting. After the reaction ends, cool the reaction product, then perform vacuum filtration. Wash and dry the filter cake to obtain the heat-resistant enhancer.

2. The special high-temperature resistant composite additive for PPR pipes according to claim 1, characterized in that, The dosage ratio of p-hydroxybenzaldehyde, triethylamine, ethyl acetate, and the phenyl dichlorophosphate solution in step a1 is 22 mmol:25 - 30 mmol:50 - 55 mL:20 - 22 mL.

3. A special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 1, characterized in that, The phenyl dichlorophosphate solution in step a1 is a solution formed by dissolving phenyl dichlorophosphate at 10 mmol:20 mL in ethyl acetate.

4. The special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 1, characterized in that The dosage ratio of 2-amino-1,3,4-thiadiazole, N,N-dimethylformamide, the dialdehyde intermediate, and DOPO in step a2 is 20 mmol:60 - 70 mL:10 mmol:20 mmol.

5. A special high-temperature resistant composite additive for PPR pipes according to claim 1, characterized in that, The modified heat-resistant filler is prepared by the following steps: Ultrasonically disperse alumina and an ethanol solution, then adjust the pH with acetic acid, then add silane coupling agent KH-792 and stir and react. After the reaction ends, cool the reaction product, then centrifuge, wash and dry the precipitate to obtain the modified heat-resistant filler.

6. The special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 5, characterized in that The dosage ratio of alumina, the ethanol solution, and silane coupling agent KH-792 is 10 g:60 - 70 mL:0.7 - 2.5 g; the volume fraction of the ethanol solution is 80 - 85%; the average particle size of the alumina is 5 μm.

7. A special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 1, characterized in that, The modified heat-conducting filler is prepared by the following steps: Ultrasonically disperse aluminum nitride, absolute ethanol, and deionized water, then adjust the pH with acetic acid, then add titanate coupling agent LD-144 and stir and react. After the reaction ends, cool the reaction product, then centrifuge, wash and dry the precipitate to obtain the modified heat-conducting filler.

8. The special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 7, characterized in that, The dosage ratio of aluminum nitride, absolute ethanol, deionized water, and titanate coupling agent LD-144 is 5 g:80 - 90 mL:10 - 15 mL:0.6 - 2.2 g; the average particle size of the aluminum nitride is 2 μm.

9. A preparation method of a high-temperature resistant composite auxiliary agent special for PPR pipes, characterized in that, Comprising the following steps: Step one: Weigh 20 - 25 parts of heat-resistant enhancer, 7 - 15 parts of modified heat-resistant filler, 11 - 23 parts of modified heat-conducting filler, 10 - 12 parts of nucleating agent, and 9 - 13 parts of antioxidant in parts by weight for standby; Step 2: Add the heat resistance enhancer, modified heat-resistant filler, modified thermal conductive filler, nucleating agent and antioxidant into a high-speed mixer, and stir and mix for 10 - 20 min under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1200 r / min to obtain a high-temperature resistant composite additive special for PPR pipes.

10. The preparation method of a special high-temperature resistant composite auxiliary agent for PPR pipes according to claim 9, characterized in that, The nucleating agent is ADK STAB NA-11 nucleating agent; The antioxidant is a mixture of antioxidant 168, antioxidant 1010 and antioxidant 1330 in a mass ratio of 3:1:2.

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