Preparation method of high-temperature-resistant flame-retardant liner and liner thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a preparation method of a high-temperature-resistant flame-retardant liner and the liner thereof.The preparation method comprises the following steps that hydrotalcite is pretreated, hydrotalcite is dispersed in methylbenzene to be subjected to ultrasonic treatment, a silane coupling agent is added, and the hydrotalcite is pretreated; loading a phosphorus-nitrogen compound, dropwise adding a nitrogen-phosphorus compound mixed solution into the modified hydrotalcite, reacting for 4-8 hours to form a phosphorus-nitrogen-silicon compound, and loading the phosphorus-nitrogen-silicon compound on the surface of the hydrotalcite; blending: mixing the modified hydrotalcite and an EVA matrix according to a ratio, feeding the mixture into an internal mixer for blending, and feeding the mixture into an open mill for open milling after blending to obtain a master batch; molding processing is conducted, specifically, the master batch is placed in a mold to be subjected to foaming treatment for 3-5 h, a foamed sheet is obtained, the foamed sheet is fed into a slicer to be sliced and cut, and the high-temperature-resistant flame-retardant gasket is obtained. The high-temperature-resistant flame-retardant gasket prepared by the invention has high-temperature-resistant environment and flame-retardant capability, reduces smoke and meets the environmental protection requirement.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a method for preparing a high temperature resistant flame retardant liner and the liner. Background Art

[0002] EVA is an ethylene-vinyl acetate copolymer, which has certain flexibility and processing properties. Due to the introduction of polar side groups on the molecular chain, the branching degree of the polymer is increased, thereby reducing the regularity of the polymer molecular chain, and then reducing the crystallinity of the polymer, making EVA have good elasticity, flexibility and other mechanical properties, and can be used as a gasket. The gasket used in electronic devices, cable sheaths or building materials needs to be flexible, high temperature resistant and flame retardant at the same time, but the high temperature resistance and flame retardancy of EVA materials are difficult to meet actual needs.

[0003] Common additive flame retardants can be divided into halogen flame retardants and halogen-free flame retardants. Among them, halogen-free flame retardants are the preferred flame retardants because they are more environmentally friendly. Among halogen-free flame retardants, inorganic hydroxide series, phosphorus flame retardants and intumescent flame retardants are common, among which aluminum hydroxide and magnesium hydroxide are common flame retardants. They have three functions of filler, flame retardant and smoke suppressant, but they have disadvantages such as low flame retardant efficiency and poor compatibility with the group. Generally, the addition amount needs to reach 50-60% to obtain a good flame retardant effect, which has a great impact on the mechanical properties of polymer materials.

[0004] Therefore, there is a need for a method for preparing a liner with a small amount of additives and good high temperature resistance and flame retardant effects and a product thereof. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a high temperature resistant flame retardant pad and the pad thereof, aiming to solve the problem in the prior art of lacking a pad that is resistant to high temperatures and has good flame retardant effects.

[0006] To achieve the above object, the present invention provides a method for preparing a high temperature resistant flame retardant liner, the method comprising the following steps:

[0007] pre-treating the hydrotalcite by dispersing the hydrotalcite in toluene, ultrasonically treating the hydrotalcite, and adding a silane coupling agent to pre-treat the hydrotalcite;

[0008] Loading phosphorus and nitrogen compounds, adding a nitrogen and phosphorus compound mixture to the modified hydrotalcite, reacting for 4 to 8 hours, forming phosphorus and nitrogen silicon compounds and loading them on the surface of the hydrotalcite;

[0009] Blending: mixing the modified hydrotalcite and the EVA matrix according to a proportion, and sending them into an internal mixer for blending, and then sending them into an open mixer for open mixing to obtain a masterbatch;

[0010] Molding processing, placing the masterbatch in a mold for foaming treatment for 3 to 5 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0011] Furthermore, the step of pre-treating the hydrotalcite by dispersing the hydrotalcite in toluene, ultrasonically treating the hydrotalcite, and adding a silane coupling agent to pre-treat the hydrotalcite further includes:

[0012] Calcine the hydrotalcite at 350-400°C for 2-4 hours to remove water between the hydrotalcite layers;

[0013] The hydrotalcite is dispersed in toluene and subjected to ultrasonic treatment for 0.5 to 2 hours, and a silane coupling agent is added. The temperature is raised to reflux temperature, and the reaction is continued with stirring for 6 to 8 hours to obtain a pretreated hydrotalcite.

[0014] Furthermore, the step of dispersing the hydrotalcite in toluene and subjecting it to ultrasonic treatment for 0.5 to 2 hours, adding a silane coupling agent, heating it to reflux temperature, and continuously stirring and reacting for 6 to 8 hours to obtain the pretreated hydrotalcite also includes:

[0015] The silane coupling agent and ethanol were mixed in a volume ratio of 9:1, and the pH was adjusted to 4-5, and stirred for hydrolysis at 50°C for 1 hour to generate silanol;

[0016] The hydrotalcite after removing the interlayer water is added to the hydrolyzed silane coupling agent solution and ultrasonically dispersed for 0.5 to 2 hours;

[0017] Passing nitrogen gas, reacting at reflux temperature for 6 to 8 hours under nitrogen atmosphere, so that the silane coupling agent condenses with the hydroxyl groups on the surface of the hydrotalcite;

[0018] The hydrotalcite was centrifuged and washed with ethanol. After washing, it was sent to a drying room and dried at 80° C. to obtain pretreated hydrotalcite.

[0019] Furthermore, the step of loading the phosphorus-nitrogen compound, adding a nitrogen-phosphorus compound mixture to the modified hydrotalcite and reacting for 4 to 8 hours to form a phosphorus-nitrogen-silicon compound and loading it on the surface of the hydrotalcite, further includes:

[0020] The pretreated hydrotalcite was cooled to 30°C, and a diphenyl chlorophosphonate solution and a triethylamine-toluene mixture were added dropwise, and the mixture was reacted for 4 to 8 hours to generate phosphorus nitrogen silicon compounds, which were loaded on the surface of the hydrotalcite;

[0021] The solid-liquid separation was carried out, and the hydrotalcite was washed with ethanol, and then sent to a drying room to be dried at 60° C. for 24 to 48 hours to obtain a modified hydrotalcite modified with phosphorus nitrogen silicon intercalation.

[0022] Furthermore, the blending step of mixing the modified hydrotalcite and the EVA matrix in proportion, feeding them into an internal mixer for blending, and then feeding them into an open mixer for open mixing to obtain a masterbatch may also include:

[0023] The EVA matrix was fed into an internal mixer, plasticized at 130-150°C for 2-3 minutes, and the modified hydrotalcite was added in batches according to the proportion;

[0024] Add antioxidant and lubricant, mix until the torque of the internal mixer is stable, and maintain for 6 to 8 minutes;

[0025] After the mixing is completed, take out the rubber material, and crush it into particles after it cools to room temperature;

[0026] The granular rubber material is fed into an open mixing mill and repeatedly mixed for 3 to 5 minutes. The roller distance of the open mixing mill is adjusted to the target thickness. The smooth rubber material is cut and rolled into a sheet to obtain a masterbatch.

[0027] The present invention also discloses a high temperature resistant flame retardant liner, which is prepared by the high temperature resistant flame retardant liner preparation method described in any one of the above technical solutions.

[0028] Furthermore, the high temperature resistant flame retardant liner is prepared from the following raw materials in parts by weight: 100 to 150 parts of EVA matrix; 10 to 30 parts of modified hydrotalcite; 0.5 to 1 part of antioxidant; and 0.5 to 1 part of lubricant.

[0029] Further, the silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethyl(ethyl)oxysilane, the antioxidant is one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl, tris[2,4-di-tert-butylphenyl]phosphite; the lubricant is one or more of stearic acid, zinc stearate, polyethylene wax, glyceryl monostearate

[0030] In the present invention, the flame retardant property and thermal stability of the EVA material are significantly improved by modifying the hydrotalcite, and the addition amount is significantly lower than the addition amount of the flame retardant in the prior art (50-60%), while maintaining good mechanical properties. With the increase of the amount of the modified hydrotalcite, the flame retardant property and thermal stability can be further improved. The liner prepared by the EVA material disclosed in the present invention can be applied to the fields of electronic devices, cable sheaths or building materials. The addition amount of the modified hydrotalcite as a flame retardant is small and the high temperature resistance and flame retardant effects are good. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0032] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0033] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0034] It is understandable that hydrotalcites (LDHs) themselves have interlayer controllability, and can be made flame retardant by intercalating phosphorus and nitrogen compounds. The phosphorus element as an acid source can promote the formation of the carbon layer, the nitrogen element as a gas source releases inert gas, and the silicon element enhances the stability of the carbon layer. The combined effect of the three can improve the flame retardant efficiency.

[0035] The silane coupling agent involved in the present invention is: γ-aminoethylaminopropyltrimethoxysilane (KH-792), which is a bisaminosilane coupling agent and has significant advantages in improving the interfacial compatibility between fillers and polymer matrices. Doping hydrotalcite in EVA material and using KH-792 as a silane coupling agent can form a chemical bond with the surface of hydrotalcite, and at the same time produce a strong interaction with the polar groups (such as vinyl acetate units) in the EVA matrix. Strong interfacial compatibility helps to evenly disperse hydrotalcite in the EVA matrix, reduce filler agglomeration, thereby improving the mechanical properties of the material, and can also participate in the carbonization reaction to form a dense carbon layer, thereby enhancing the flame retardant properties of the material and improving the limiting oxygen index (LOI) and vertical combustion rating (UL-94) of the EVA material. The specific structure is as follows:

[0036]

[0037] In the present invention, an amino-containing silane coupling agent is used to react with hydrotalcite to generate a phosphorus-nitrogen-silicon compound, and the modified hydrotalcite is then doped into an EVA matrix to obtain a high-temperature-resistant and flame-retardant EVA material with excellent thermal stability, and the material is then prepared into a liner for use in electronic devices, cable sheaths or building materials.

[0038] It can be understood that in the mixing process of the EVA matrix and the modified hydrotalcite in the present invention, the selection of antioxidants and lubricants is also relatively important. The antioxidant is used to prevent the EVA from thermal oxidation degradation due to high temperature and shearing during the processing, and to maintain the stability of the material properties; the lubricant is used to improve the processing fluidity of EVA, reduce the phenomenon of sticking to the roller and the mold, and improve the dispersibility of the filler.

[0039] The present invention also discloses specific application examples 1-3 and EVA pads of control examples 1-2 of the prior art for performance comparison experiments, which are as follows:

[0040] Embodiment 1:

[0041] Raw materials (by weight):

[0042] 1. 100 parts of EVA resin (VA content 28%);

[0043] 2. 10 parts of modified hydrotalcite;

[0044] 3. Antioxidant: 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0045] 4. Antioxidant tris[2,4-di-tert-butylphenyl]phosphite 0.2 parts;

[0046] 5. Lubricant zinc stearate 0.5 parts;

[0047] 6. 0.5 parts of lubricant polyethylene wax.

[0048] Preparation steps:

[0049] S1, calcining the hydrotalcite at 350°C for 2h to remove the interlayer water of the hydrotalcite, and mixing the silane coupling agent and ethanol in a volume ratio of 9:1, adjusting the pH to 4, stirring and hydrolyzing at 50°C for 1h to generate silanol; then dispersing the hydrotalcite after removing the interlayer water in toluene and adding the hydrolyzed silane coupling agent solution, and ultrasonically dispersing for 0.5h; after the ultrasonic dispersion is completed, nitrogen is introduced, and the temperature is raised to the reflux temperature (110°C) in a nitrogen atmosphere to react for 6h, so that the silane coupling agent condenses with the surface hydroxyl groups of the hydrotalcite; centrifugation is performed, and the hydrotalcite is repeatedly washed with ethanol for at least three times, and after washing, it is sent to a drying room and dried at 80°C to obtain pre-treated hydrotalcite;

[0050] S2, cooling the pretreated hydrotalcite to 30°C, adding diphenyl chlorophosphonate solution and triethylamine-toluene mixed solution dropwise, reacting for 4 hours to generate phosphorus nitrogen silicon compound, and loading it on the surface of the hydrotalcite, then performing solid-liquid separation, washing the hydrotalcite with ethanol, and sending it into a drying room to dry at 60°C for 24 hours to obtain phosphorus nitrogen silicon intercalation modified hydrotalcite;

[0051] S3, the EVA matrix is ​​sent to the internal mixer, plasticized at 130 ° C for 2 minutes, modified hydrotalcite, antioxidant and lubricant are added in batches according to the proportion, mixed until the torque of the internal mixer is stable, maintained for 6 minutes, the rubber is taken out after the mixing is completed, and the rubber is crushed into granules after the rubber is cooled to room temperature, and the granular rubber is sent to the open mill, repeatedly turned over for 3 minutes, the roller distance of the open mill is adjusted to the target thickness, the flat rubber is cut, and rolled into a sheet to obtain a masterbatch;

[0052] S4, molding processing, placing the masterbatch in a mold for foaming treatment for 3 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0053] Embodiment 2:

[0054] Raw materials (by weight):

[0055] 1. EVA resin (VA content 28%) 150 parts;

[0056] 2. 30 parts of modified hydrotalcite;

[0057] 3. Antioxidant: 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0058] 4. Antioxidant tris[2,4-di-tert-butylphenyl]phosphite 0.5 parts;

[0059] 5. Lubricant zinc stearate 0.5 parts;

[0060] 6. 0.5 parts of lubricant polyethylene wax.

[0061] Preparation steps:

[0062] S1, calcining the hydrotalcite at 400°C for 4h to remove the interlayer water of the hydrotalcite, and mixing the silane coupling agent and ethanol in a volume ratio of 9:1, adjusting the pH to 5, stirring and hydrolyzing at 50°C for 1h to generate silanol; then dispersing the hydrotalcite after removing the interlayer water in toluene and adding the hydrolyzed silane coupling agent solution, and ultrasonically dispersing for 2h; after the ultrasonic dispersion, nitrogen is introduced, and the temperature is raised to the reflux temperature (110°C) in a nitrogen atmosphere to react for 8h, so that the silane coupling agent condenses with the surface hydroxyl groups of the hydrotalcite; centrifugation is performed, and the hydrotalcite is repeatedly washed with ethanol for at least three times, and after washing, it is sent to a drying room and dried at 80°C to obtain a pretreated hydrotalcite;

[0063] S2, cooling the pretreated hydrotalcite to 30°C, adding diphenyl chlorophosphonate solution and triethylamine-toluene mixed solution dropwise, reacting for 4 hours to generate phosphorus nitrogen silicon compound, and loading it on the surface of the hydrotalcite, then performing solid-liquid separation, washing the hydrotalcite with ethanol, and sending it into a drying room to dry at 60°C for 24 hours to obtain phosphorus nitrogen silicon intercalation modified hydrotalcite;

[0064] S3, the EVA matrix is ​​sent to the internal mixer, plasticized at 130 ° C for 2 minutes, modified hydrotalcite, antioxidant and lubricant are added in batches according to the proportion, mixed until the torque of the internal mixer is stable, maintained for 6 minutes, the rubber is taken out after the mixing is completed, and the rubber is crushed into granules after the rubber is cooled to room temperature, and the granular rubber is sent to the open mill, repeatedly turned over for 3 minutes, the roller distance of the open mill is adjusted to the target thickness, the flat rubber is cut, and rolled into a sheet to obtain a masterbatch;

[0065] S4, molding processing, placing the masterbatch in a mold for foaming treatment for 3 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0066] Embodiment 3:

[0067] Raw materials (by weight):

[0068] 1. EVA resin (VA content 28%) 120 parts;

[0069] 2. 22 parts of modified hydrotalcite;

[0070] 3. Antioxidant: 0.4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0071] 4. Antioxidant tris[2,4-di-tert-butylphenyl]phosphite 0.3 parts;

[0072] 5. Lubricant zinc stearate 0.3 parts;

[0073] 6. 0.6 parts of lubricant polyethylene wax.

[0074] Preparation steps:

[0075] S1, calcining the hydrotalcite at 350°C for 2h to remove the interlayer water of the hydrotalcite, and mixing the silane coupling agent and ethanol in a volume ratio of 9:1, adjusting the pH to 4, stirring and hydrolyzing at 50°C for 1h to generate silanol; then dispersing the hydrotalcite after removing the interlayer water in toluene, adding the hydrolyzed silane coupling agent solution, and ultrasonically dispersing for 1h; after the ultrasonic dispersion, nitrogen is introduced, and the temperature is raised to the reflux temperature (110°C) under a nitrogen atmosphere to react for 7h, so that the silane coupling agent condenses with the surface hydroxyl groups of the hydrotalcite; centrifuging, and repeatedly washing the hydrotalcite with ethanol for at least three times, and after washing, sending it to a drying room and drying it at 80°C to obtain pretreated hydrotalcite;

[0076] S2, cooling the pretreated hydrotalcite to 30°C, adding diphenyl chlorophosphonate solution and triethylamine-toluene mixed solution dropwise, reacting for 4 hours to generate phosphorus nitrogen silicon compound, and loading it on the surface of the hydrotalcite, then performing solid-liquid separation, washing the hydrotalcite with ethanol, and sending it into a drying room to dry at 60°C for 24 hours to obtain phosphorus nitrogen silicon intercalation modified hydrotalcite;

[0077] S3, the EVA matrix is ​​sent to the internal mixer, plasticized at 130 ° C for 2 minutes, modified hydrotalcite, antioxidant and lubricant are added in batches according to the proportion, mixed until the torque of the internal mixer is stable, maintained for 6 minutes, the rubber is taken out after the mixing is completed, and the rubber is crushed into granules after the rubber is cooled to room temperature, and the granular rubber is sent to the open mill, repeatedly turned over for 3 minutes, the roller distance of the open mill is adjusted to the target thickness, the flat rubber is cut, and rolled into a sheet to obtain a masterbatch;

[0078] S4, molding processing, placing the masterbatch in a mold for foaming treatment for 3 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0079] Comparative Example 1:

[0080] Raw materials (by weight):

[0081] 1. 100 parts of EVA resin (VA content 28%);

[0082] 2. Flame retardant magnesium hydroxide 10 parts;

[0083] 3. Antioxidant: 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0084] 4. Antioxidant tris[2,4-di-tert-butylphenyl]phosphite 0.2 parts;

[0085] 5. 0.5 parts of zinc stearate;

[0086] 6. 0.5 parts of polyethylene wax.

[0087] Preparation steps:

[0088] S1. The EVA matrix is ​​sent to an internal mixer, plasticized at 130°C for 2 minutes, and flame retardant magnesium hydroxide, antioxidant, and lubricant are added in batches according to the proportion, and mixed until the torque of the internal mixer is stable, and maintained for 6 minutes. After the mixing is completed, the rubber material is taken out, and the rubber material is crushed into granules after cooling to room temperature. The granular rubber material is sent to an open mixer, repeatedly turned over for 3 minutes, and the roller distance of the open mixer is adjusted to the target thickness. The flat rubber material is cut and rolled into a sheet to obtain a masterbatch;

[0089] S4, molding processing, placing the masterbatch in a mold for foaming treatment for 3 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0090] Comparative Example 2:

[0091] Raw materials (by weight):

[0092] 1. 100 parts of EVA resin (VA content 28%);

[0093] 2. 10 parts of unmodified hydrotalcite;

[0094] 3. Antioxidant: 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0095] 4. Antioxidant tris[2,4-di-tert-butylphenyl]phosphite 0.2 parts;

[0096] 5. 0.5 parts of zinc stearate;

[0097] 6. 0.5 parts of polyethylene wax.

[0098] Preparation steps:

[0099] S1. The EVA matrix was fed into an internal mixer and plasticized at 130° C. for 2 min. Unmodified hydrotalcite, antioxidant and lubricant were added in batches according to the proportion, and the mixture was mixed until the torque of the internal mixer was stable and maintained for 6 min. After the mixing was completed, the rubber was taken out, and the rubber was crushed into granules after the rubber was cooled to room temperature. The granular rubber was fed into an open mixer and repeatedly refining for 3 min. The roller distance of the open mixer was adjusted to the target thickness, and the flat rubber was cut and rolled into a sheet to obtain a masterbatch.

[0100] S4, molding processing, placing the masterbatch in a mold for foaming treatment for 3 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

[0101] The present invention also discloses a performance comparison experiment to detect the thermal stability and flame retardant effect of the high temperature resistant flame retardant liner disclosed in the present invention. The present invention prepares the high temperature resistant flame retardant liner in Examples 1-3 and Comparative Examples 1 and 2 as standard test specimens, and conducts a comparative test on the limiting oxygen index (LOI), vertical combustion (UL-94), thermogravimetric analysis, tensile properties and other material properties. The specific experimental steps are as follows:

[0102] 1. Limiting oxygen index test:

[0103] S1. Cut each group of examples into standard test strips with a length of 80 mm, a width of 6 mm, and a thickness of 3 mm. Prepare 5 strips for each group of examples and control examples.

[0104] S2. Turn on the oxygen and nitrogen gas sources of the limiting oxygen index instrument and adjust the flow meter so that the oxygen and nitrogen mixture ratio reaches the initial value (such as 20% oxygen);

[0105] S3, ignite a propane flame with a flame height of 20 mm and calibrate the limiting oxygen index instrument;

[0106] S4. Fix the specimen vertically in the specimen holder, with the top end at least 50 mm away from the top of the combustion tube;

[0107] S5, ignite the top of the sample, observe the combustion situation, and adjust the oxygen concentration according to the burning time of the sample until the lowest oxygen concentration at which the sample burns within 3 minutes is found;

[0108] S6. Record the LOI value of each group of splines, and take the average value of the five splines in each group of embodiments as the final result.

[0109] 2. Vertical combustion (UL-94) test:

[0110] S1. Cut each group of examples into standard test strips with a length of 125 mm, a width of 13 mm, and a thickness of 3 mm. Prepare 5 strips for each group of examples and control examples.

[0111] S2. Turn on the vertical combustion tester and adjust the flame height to a blue flame of 20 mm;

[0112] S3. Fix the specimen vertically in the specimen holder, with the top end at least 10 mm away from the top of the combustion tube;

[0113] S4, ignite the bottom of the spline, keep the flame on for 10 seconds and then remove the flame;

[0114] S5. Record the burning time of the sample, whether the dripping material ignites the cotton, the burning length and other data;

[0115] S6, repeat the ignition for the second time and record the data;

[0116] S7. Determine the UL-94 grade (V-0, V-1, V-2, no grade) of the sample according to the burning time and the dripping situation.

[0117] 3. Thermogravimetric analysis (TGA) test:

[0118] S1. Cut each group of examples into small pieces, take 5 mg of small pieces as one sample, and prepare 3 samples for each group of examples and control examples;

[0119] S2, use Al2O3 standard sample to calibrate the thermogravimetric analyzer;

[0120] S3, placing the sample in a TGA sample pan, and heating the sample from room temperature to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere;

[0121] S4. Record the mass-temperature curve of the sample, and read the initial decomposition temperature (T5%, the temperature at which the weight loss is 5% mass) and the maximum decomposition temperature (T max , the temperature at which the rate of weight loss is maximum);

[0122] 4. Tensile performance test:

[0123] S1. Cut each group of examples into standard dumbbell-shaped strips with a length of 150 mm, a width of 10 mm, and a thickness of 2 mm. Prepare 5 strips for each group of examples.

[0124] S2. Calibrate the load sensor and displacement sensor of the universal material testing machine;

[0125] S3. Fix the specimen in the fixture of the testing machine, ensure that the specimen and the fixture are aligned, set the tensile rate to 50 mm / min, and start the test;

[0126] S4, recording the stress-strain curve of the spline until the spline breaks, reading the tensile strength (maximum stress) and elongation at break (strain at break) from the stress-strain curve and recording them;

[0127] The performance comparison experiment is shown in the following table:

[0128] Table 1 Performance comparison test data

[0129]

[0130]

[0131] Experimental conclusion:

[0132] The LOI of Examples 1-3 is significantly higher than that of the control example, and the UL-94 grade reaches V-1 or V-0, indicating that the modified hydrotalcite significantly improves the flame retardancy of EVA, while the flame retardancy of Control Example 1 (conventional flame retardant) and Control Example 2 (unmodified hydrotalcite) are poor. max The tensile strength and elongation at break of Examples 1-3 are slightly lower than those of Control Example 1, but higher than those of Control Example 2, indicating that the modified hydrotalcite maintains good mechanical properties while improving flame retardancy.

[0133] In combination with all the above embodiments, the flame retardant properties and thermal stability of the EVA material are significantly improved by modifying the hydrotalcite in the present invention, while maintaining good mechanical properties. With the increase in the amount of modified hydrotalcite, the flame retardant properties and thermal stability can be further improved. The gasket prepared by the EVA material disclosed in the present invention can be applied to the fields of electronic devices, cable sheaths or building materials. The modified hydrotalcite added as a flame retardant is small and has good high temperature resistance and flame retardant effects.

[0134] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant flame retardant liner, characterized in that: The following steps are involved: pre-treating the hydrotalcite by dispersing the hydrotalcite in toluene, ultrasonically treating the hydrotalcite, and adding a silane coupling agent to pre-treat the hydrotalcite; Loading phosphorus and nitrogen compounds, adding a nitrogen and phosphorus compound mixture to the modified hydrotalcite, reacting for 4 to 8 hours, forming phosphorus and nitrogen silicon compounds and loading them on the surface of the hydrotalcite; Blending: mixing the modified hydrotalcite and the EVA matrix according to a proportion, and sending them into an internal mixer for blending, and then sending them into an open mixer for open mixing to obtain a masterbatch; Molding processing, placing the masterbatch in a mold for foaming treatment for 3 to 5 hours to obtain a foamed sheet, and sending the foamed sheet to a sheet cutting machine for sheet cutting to obtain a high temperature resistant flame retardant pad.

2. The method for preparing a high temperature resistant flame retardant liner according to claim 1, characterized in that: The step of pre-treating the hydrotalcite by dispersing the hydrotalcite in toluene, subjecting the hydrotalcite to ultrasonic treatment, and adding a silane coupling agent to pre-treat the hydrotalcite also includes: Calcine the hydrotalcite at 350-400°C for 2-4 hours to remove water between the hydrotalcite layers; The hydrotalcite is dispersed in toluene and subjected to ultrasonic treatment for 0.5 to 2 hours, and a silane coupling agent is added. The temperature is raised to reflux temperature, and the reaction is continued with stirring for 6 to 8 hours to obtain a pretreated hydrotalcite.

3. The method for preparing a high temperature resistant flame retardant liner according to claim 2, characterized in that: The step of dispersing the hydrotalcite in toluene and subjecting it to ultrasonic treatment for 0.5 to 2 hours, adding a silane coupling agent, heating it to reflux temperature, and continuously stirring and reacting for 6 to 8 hours to obtain the pretreated hydrotalcite also includes: The silane coupling agent and ethanol were mixed in a volume ratio of 9:1, and the pH was adjusted to 4-5, and stirred for hydrolysis at 50°C for 1 hour to generate silanol; The hydrotalcite after removing the interlayer water is added to the hydrolyzed silane coupling agent solution and ultrasonically dispersed for 0.5 to 2 hours; Passing nitrogen gas, reacting at reflux temperature for 6 to 8 hours under nitrogen atmosphere, so that the silane coupling agent condenses with the hydroxyl groups on the surface of the hydrotalcite; The hydrotalcite was centrifuged and washed with ethanol. After washing, it was sent to a drying room and dried at 80° C. to obtain pretreated hydrotalcite.

4. The method for preparing a high temperature resistant flame retardant liner according to claim 1, characterized in that: The step of loading the phosphorus-nitrogen compound, adding a nitrogen-phosphorus compound mixture to the modified hydrotalcite and reacting for 4 to 8 hours to form a phosphorus-nitrogen-silicon compound and loading it on the surface of the hydrotalcite, further includes: The pretreated hydrotalcite was cooled to 30°C, and a diphenyl chlorophosphonate solution and a triethylamine-toluene mixture were added dropwise, and the mixture was reacted for 4 to 8 hours to generate phosphorus nitrogen silicon compounds, which were loaded on the surface of the hydrotalcite; The solid-liquid separation was carried out, and the hydrotalcite was washed with ethanol, and then sent to a drying room to be dried at 60° C. for 24 to 48 hours to obtain a modified hydrotalcite modified with phosphorus nitrogen silicon intercalation.

5. The method for preparing a high temperature resistant flame retardant liner according to claim 3, characterized in that: The blending comprises mixing the modified hydrotalcite and the EVA matrix in proportion, feeding them into an internal mixer for blending, and then feeding them into an open mixer for open mixing to obtain a masterbatch, and further comprising: The EVA matrix was fed into an internal mixer and plasticized at 130-150°C for 2-3 minutes, and the modified hydrotalcite was added in batches according to the proportion; Add antioxidant and lubricant, mix until the torque of the internal mixer is stable, and maintain for 6 to 8 minutes; After the mixing is completed, take out the rubber material, and crush it into particles after it cools to room temperature; The granular rubber material is fed into an open mixing mill and repeatedly mixed for 3 to 5 minutes. The roller distance of the open mixing mill is adjusted to the target thickness. The smooth rubber material is cut and rolled into a sheet to obtain a masterbatch.

6. A high temperature resistant flame retardant liner, characterized in that: The high temperature resistant flame retardant liner is prepared by the high temperature resistant flame retardant liner preparation method according to any one of claims 1 to 5.

7. The high temperature resistant flame retardant gasket according to claim 6, characterized in that: The high temperature resistant flame retardant liner is prepared from the following raw materials in parts by mass: 100-150 parts of EVA matrix; 10-30 parts of modified hydrotalcite; 0.5-1 part of antioxidant; and 0.5-1 part of lubricant.

8. The high temperature resistant flame retardant gasket according to claim 7, characterized in that: The silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethyl(ethyl)oxysilane, the antioxidant is one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl, and tris[2,4-di-tert-butylphenyl]phosphite; the lubricant is one or more of stearic acid, zinc stearate, polyethylene wax, and glyceryl monostearate.

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