A pipe sheath foamed material and a method for manufacturing the same

Abstract

The invention discloses a kind of pipeline sheath foamed material, it is made of including the following weight parts of component: ethylene-propylene rubber 50~70 parts, polyethylene 30~50 parts, reinforcing filling system 40~60 parts, plasticizer 20~40 parts, active agent 3~5 parts, accelerator system 2~4 parts, crosslinking agent 2~4 parts, anti-aging system 5~10 parts, foaming system 5~10 parts;Ethylene-propylene rubber and polyethylene total amount is 100 weight parts, the reinforcing filling system is carbon black and magnesium hydroxide are used together.The invention adds proper amount of magnesium hydroxide in conventional ethylene-propylene foamed material formula and uses carbon black together, anti-aging agent 445 and anti-aging agent 3100 are used together, and accelerator M and dithio amino salt accelerator are used together, proper amount of linear structure polyethylene and ethylene-propylene rubber are used together, improve the softness, strength and aging resistance of foamed material, meet different environmental use requirements.

Description

Technical Field

[0001] This invention belongs to the field of rubber materials and relates to a pipeline sheath foaming material and its preparation method. Background Technology

[0002] To extend the service life of hoses such as air conditioning pipes and water pipes, a flexible foam sheath needs to be installed. The flexible foam sheath not only protects the hose from long-term damage caused by light, heat, and force, preventing breakage and aging, but also provides sound insulation and vibration damping. It is a commonly used method in the industry; therefore, the uniformity and density of the foam, its strength, and its aging resistance are extremely important.

[0003] "The Influence of AC / OBSH Combination on the Foaming Properties of EPDM Rubber, Special Rubber Products, 2022, 43(04): 1-5, 20" This study used EPDM rubber (EPDM) as the matrix and azodicarbonamide (AC) and 4,4'-oxobis(benzenesulfonyl)hydrazine (OBSH) as foaming agents to prepare EPDM foam materials and investigated the influence of different AC / OBSH ratios on their properties. The results showed that with the increase of OBSH content in the composite foaming agent AC / OBSH, the vulcanization speed of the compound accelerated, the cell size decreased, the cell distribution became more uniform, and the mechanical properties were correspondingly improved. This study mainly introduced the main properties of OBSH in the combination of two foaming agents, focusing on the change in the amount of OBSH after the AC / OBSH combination, which increased the vulcanization speed and prepared foam materials with small cell size and uniform cell distribution. However, in the field of rubber materials, the performance of foaming agents does not solely depend on the properties of the foaming agent itself, nor solely on the performance resulting from the combined use of multiple foaming agents. Rather, it is easily influenced by the properties of various raw materials within the rubber or rubber-plastic composite material, thus exhibiting multi-directional characteristics. For example, firstly, the foaming temperatures of foaming agents AC and OBSH within the material are highly susceptible to changes caused by the vulcanization system. Simply increasing the amount of foaming agent or adjusting the component ratio within the composite foaming system to adjust the foaming speed cannot achieve a matching foaming speed with the vulcanization speed. Secondly, the dispersion temperature and uniformity of the raw materials within the material, including the foaming agent, affect the foaming efficiency and uniformity of foaming agents AC and OBSH. Thirdly, a mismatch between the foaming speed and the vulcanization speed within the material can easily lead to air leakage during foaming or cross-linking of the material during foaming, preventing further foaming. Therefore, simply increasing the amount of foaming agent or adjusting the component ratio within the composite foaming system to improve foaming efficiency and reduce material density is insufficient, and adding foaming agents to EPDM rubber has limitations.

[0004] "The Influence of Modified AC on the Structure and Foaming Properties of EPDM Sponge Rubber, Special Rubber Products, 2023, 44(01): 7-11, 29" uses ethylene propylene diene monomer (EPDM) rubber as the base rubber and silica as the nucleating agent to compare and investigate the effects of silica chemically modified foaming agent AC and physically modified foaming agent AC on the properties of EPDM foam materials. When silica particles are used as nucleating agents, in addition to providing a large number of nucleation sites for bubble nucleation in the foaming system, they can also have a certain barrier effect on gas, so as to make the foaming agent AC less prone to agglomeration and moisture absorption, and to produce EPDM sponge products with more uniform cell structure. This scheme tends to use silica particles to nucleate and improve the foaming structure, and improve the gas leakage phenomenon during the foaming process. Firstly, in the field of materials, nucleation requires free electrons, and the presence of free electrons will affect the dispersion and uniformity of raw materials within the rubber. Secondly, even if the nucleating agent is stable within the compound, during vulcanization, the foaming agent decomposes to produce gas. The material will either foam or not foam, because when the material foams, it is ultimately the rubber or rubber-plastic matrix that foams, while the various raw materials such as fillers, plasticizers, and vulcanizing agents do not foam. Since it is the rubber or rubber-plastic matrix that foams, the nucleation of silica particles cannot completely block the gas. Matching the vulcanization rate and foaming rate of the rubber material is the best technical solution for blocking the gas.

[0005] In summary, the key to solving the problems of softness, strength, and aging resistance of foamed materials lies in: how to improve the uniformity of foaming agent dispersion, how to improve foaming efficiency, and how to maintain the stability of the anti-aging system during the foaming process. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing foam materials and provide a pipe sheath foam material. By adding an appropriate amount of magnesium hydroxide and carbon black, antioxidant 445 and antioxidant 3100, accelerator M and dithioamino salt accelerator, and an appropriate amount of linear polyethylene and ethylene propylene rubber to the conventional ethylene propylene foam material formula, the flexibility, strength and aging resistance of the foam material are improved, meeting the requirements of different environments.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A pipe sheath foam material, which is made of components comprising the following parts by weight:

[0009]

[0010] The total amount of ethylene propylene rubber and polyethylene is 100 parts by weight, and the amount of ethylene propylene rubber shall not be less than the amount of polyethylene.

[0011] The reinforcing filler system is a combination of carbon black and magnesium hydroxide.

[0012] Preferably, the pipe sheath foam material is made of components comprising the following parts by weight:

[0013]

[0014]

[0015] The ethylene propylene rubber mentioned is EPDM rubber, with a vinyl content of 25% to 50% and a Mooney viscosity of 50 to 100 (mL). 1+4 (100℃), the content of the third monomer ENB is 5% to 10%.

[0016] The polyethylene mentioned is linear low-density polyethylene (LLDPE), a copolymer of ethylene and a small amount of α-olefin, with a density of 0.9–0.94 g / cm³. 3 .

[0017] The weight ratio of carbon black to magnesium hydroxide is 2:1 to 4:1, preferably 3:1 to 3.5:1.

[0018] The carbon black is at least one of semi-reinforcing carbon black N774 or carbon black N990.

[0019] The plasticizer is environmentally friendly paraffin oil 2280, which has the advantages of stable molecular weight, extremely low volatility, low VOC emissions, and high flash point (318℃).

[0020] The activator is a combination of zinc oxide and stearic acid; the weight ratio of zinc oxide to stearic acid is 2:1 to 4:1, preferably 4:1.

[0021] The accelerator system is a blend of accelerator M and dithioamino salt accelerator; the weight ratio of accelerator M to dithioamino salt accelerator is 1:1 to 1:2, preferably 1:1.

[0022] The dithioamino salt accelerator is at least one of accelerator EZ and accelerator PX, preferably a combination of accelerator EZ and accelerator PX in a weight ratio of 1:1 to 1:2.

[0023] The crosslinking agent is sulfur particles S-80.

[0024] The anti-aging system is composed of antioxidant 445 and antioxidant 3100 used together, and the weight ratio of antioxidant 445 to antioxidant 3100 is 2:1 to 4:1, preferably 2:1.

[0025] The foaming system is a combination of foaming agent OBSH (4,4'-oxobisbenzenesulfonylhydrazine) and foaming agent AC (azodicarbonamide); the weight ratio of foaming agent OBSH to foaming agent AC is 1:1 to 1:2.

[0026] Another object of the present invention is to provide a method for preparing the aforementioned pipe sheath foam material, comprising the following steps:

[0027] Step (1): First stage of mixing to prepare masterbatch: Preheat the internal mixer to 55℃~75℃, add polyethylene, ethylene propylene rubber, activator and antioxidant, mix, and raise the plug twice; then add carbon black and plasticizer, mix, and raise the plug twice; add the foaming agent and magnesium hydroxide blend, mix, and raise the plug twice. When the temperature of the rubber compound reaches 135℃~145℃, discharge the material, roll out the sheet from the open mill, cool it with air, and obtain the masterbatch sheet. Let it stand for more than 8 hours.

[0028] Step (2) Two-stage mixing preparation of compounded rubber: Add masterbatch rubber sheet, raise the bolt twice, then add accelerator and crosslinking agent, mix, raise the bolt twice, wait for the rubber temperature to reach 105℃~115℃, discharge, pass through the open mill twice, adjust the roller gap to 6~8mm, after the rubber material wraps around the roller, output rubber strip, blow air to cool, obtain compounded rubber strip, and let it stand for more than 24 hours;

[0029] Step (3): The mixed rubber strip is extruded to obtain a semi-finished product. The semi-finished product enters the microwave drying tunnel for foaming and vulcanization to obtain pipeline foam sheath material.

[0030] In step (1), the foaming agent and magnesium hydroxide are first blended to obtain a blend, and then the materials are added for mixing.

[0031] The total mixing time for a single-stage masterbatch compound is generally 8 to 10 minutes.

[0032] In step (2), the total mixing time for the two-stage mixing process is generally 6 to 8 minutes.

[0033] In step (3), the vulcanization foaming is as follows: the semi-finished product passes sequentially through oven 1, oven 2, oven 3 and oven 4. The temperature of oven 1 is 220-240℃, the temperature of oven 2 is 220-240℃, the temperature of oven 3 is 190-220℃, and the temperature of oven 4 is 190-220℃. The total vulcanization foaming time in the oven is 15-18 minutes. The vulcanization foaming pressure is atmospheric pressure. The vulcanization foaming is carried out with or without microwave. When the microwave is started, the microwave power is 2-3kW.

[0034] Preferably, the production of the pipeline foam sheath material is a continuous production process, including: continuous feeding and extrusion molding of the mixed rubber strip to obtain a semi-finished product, the semi-finished product entering the microwave drying tunnel through rotating rollers for foaming vulcanization, cooling, dimensional inspection and winding operations to obtain the pipeline foam sheath product.

[0035] The room temperature physical properties of the pipe sheath foaming material described in this invention meet the following requirements:

[0036]

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The present invention adds an appropriate amount of magnesium hydroxide and carbon black together. During the mixing process, magnesium hydroxide is lubricating, and the foaming agent and carbon black are evenly dispersed. During the vulcanization process, magnesium hydroxide is weakly alkaline and can absorb the inorganic acidic substances containing sulfur and nitrogen that affect the foaming efficiency and vulcanization efficiency generated during the vulcanization process. This improves the uniformity of the crosslinking density of the material and the uniformity of the foaming density of the material, thereby effectively improving the strength of the material.

[0039] (2) In this invention, a high molecular weight amine antioxidant 445 and a solubilizing antioxidant 3100 are used together. Antioxidant 3100 assists antioxidant 445 to be uniformly dispersed on the molecular chain of rubber material. The stability of antioxidant 445 and the relative activity of low molecular weight antioxidant 3100 produce a synergistic anti-aging effect, which can improve the aging resistance of the material and improve the long-lasting anti-aging performance of the material.

[0040] (3) This invention uses linear low-density polyethylene and EPDM rubber together. The linear polyethylene improves the single structure of the molecular chain of EPDM material. During mixing, the linear polyethylene can reduce the molecular friction of EPDM rubber and improve the dispersion uniformity of the foaming agent. During vulcanization, polyethylene participates in molecular cross-linking to improve the strength of the foaming material and participates in foaming to improve the dispersion uniformity of the foaming gas, thereby effectively reducing the material density and improving the material softness.

[0041] (4) In this invention, the accelerator M is used in combination with dithioamino salt accelerator. First, the dithioamino salt accelerator increases the foaming speed and vulcanization speed to a high speed at the same time. Then, by adding an appropriate amount of accelerator M and magnesium hydroxide, the foaming speed and vulcanization speed are adjusted to achieve a stable matching speed, which reduces the amount of foaming agent and energy consumption, effectively reduces the material density and hardness, and improves the material's softness.

[0042] (5) In the preparation of masterbatch by mixing, the internal mixer is preheated to 55℃~75℃ before feeding and mixing, and the discharge temperature is controlled at 135℃~145℃. The foaming agent OBSH, foaming agent AC and magnesium hydroxide are mixed and then fed. At the same time, in the preparation of compound by two-stage vulcanization, the mixture is mixed until the temperature of the rubber compound reaches 105℃~115℃ before being discharged. By controlling the process parameters, the present invention effectively improves the dispersion uniformity of foaming materials and the dispersion uniformity between various compounds in the material.

[0043] (6) The present invention controls the vulcanization foaming process parameters, improves the optimal matching between foaming efficiency and vulcanization efficiency, improves vulcanization efficiency and foaming efficiency, and improves the physical properties of materials. Detailed Implementation

[0044] The technical solution of the present invention will be further illustrated by using examples.

[0045] Example 1

[0046] Table 1. Formulation of pipe sheath foam material (parts by weight) for Example 1

[0047]

[0048]

[0049] Note: Magnesium hydroxide, white amorphous powder, content ≥80%, passing through 325 mesh ≥99%, moisture ≤1.5%.

[0050] A pipe sheath foam material, the composition and weight parts of which are shown in Table 1, is prepared according to the following method:

[0051] Step (1): Preparation of masterbatch through mixing: After preheating the internal mixer to 60°C, add LLDPE, EPDM 6950C, zinc oxide, stearic acid and antioxidant, mix and press twice; then add semi-reinforcing carbon black N774 and paraffin oil 2280, mix and press twice; mix foaming agent OBSH, foaming agent AC and magnesium hydroxide, then add the mixture of foaming agent OBSH, foaming agent AC and magnesium hydroxide, mix and press twice, wait for the rubber compound temperature to reach 135°C, discharge the material, the whole mixing process lasts 8 minutes; the open mill produces sheets, blow air to cool, and obtain masterbatch sheets, which are then left to stand for 24 hours;

[0052] Step (2) Two-stage mixing preparation of compounded rubber: Add masterbatch rubber sheet, raise the bolt twice, then add accelerator and crosslinking agent S-80, mix, raise the bolt twice, wait for the rubber temperature to reach 105℃, discharge the material, the whole mixing process lasts for 6 minutes; pass through the open mill twice, adjust the roller gap to 6-8mm, after the rubber material wraps around the roller, the rubber strip is discharged, blow air to cool, and the compounded rubber strip is obtained. The compounded rubber strip is left to stand for 24 hours;

[0053] Step (3): The equipment is ventilated and ventilated, and the temperature and speed of each working unit are set. After the temperature reaches the specified requirements, the equipment is started and the material is continuously fed and extruded into shape. The semi-finished product enters the microwave drying tunnel through the rotating roller and is foamed and vulcanized under normal pressure and without turning on the microwave. After cooling out of the box, the size is checked and the winding is carried out to continuously produce foamed sheath products.

[0054] The vulcanization foaming process is as follows: the temperature of drying tunnel No. 1 is 225℃, and the vulcanization time is 4 minutes; the temperature of drying tunnel No. 2 is 225℃, and the vulcanization time is 4 minutes; the temperature of drying tunnel No. 3 is 215℃, and the vulcanization time is 4 minutes; the temperature of drying tunnel No. 4 is 215℃, and the vulcanization time is 4 minutes; the entire vulcanization process in the drying tunnels takes 16 minutes.

[0055] Comparative Example 1a

[0056] A pipe sheath foam material, the composition and weight parts of which are shown in Table 1, was prepared according to the method of Example 1.

[0057] Comparative Example 1b

[0058] A pipe sheath foam material, the composition and weight parts of which are shown in Table 1, was prepared according to the method of Example 1.

[0059] Comparative Example 1c

[0060] A pipe sheath foam material, the composition and weight parts of which are shown in Table 1, was prepared according to the method of Example 1.

[0061] Comparative Example 1d

[0062] A pipe sheath foam material, the composition and weight parts of which are shown in Table 1, was prepared according to the method of Example 1.

[0063] The properties of the pipe sheath foam materials prepared in Example 1 and the four comparative examples are shown in Table 2.

[0064] Table 2. Performance of the pipe sheath foam material in Example 1

[0065]

[0066] The performance analysis led to the following conclusions:

[0067] (1) Hardness and density reflect foaming efficiency and crosslinking density uniformity, while strength and elongation reflect vulcanization efficiency. From the room-temperature physical properties such as hardness and density, it can be found that the foaming efficiency and vulcanization efficiency of the pipe sheath foaming material of this invention (Example 1) reach the highest levels. Although the density and hardness are the lowest, the material strength and elongation are not inferior at all, reaching a high level, indicating that the sheath foaming material has excellent softness and strength. Among the four comparative examples, Comparative Example 1a and Comparative Example 1d have relatively low density and hardness, while Comparative Example 1b and Comparative Example 1c have relatively high density and hardness. This shows that whether the material foaming is uniform and the foaming speed of the foaming agent is not synchronized with the vulcanization speed mainly affect the material hardness and density, and secondarily affect the material strength and elongation, ultimately leading to poor softness of the foamed material.

[0068] (2) From the high-temperature resistance and ozone sulfidation resistance of the materials, it can be found that: In Example 1, the pipe sheath foam materials prepared by Comparative Examples 1a, 1b, and 1c all showed small changes in hardness, elongation, and strength, indicating stable performance; while the foam material of Comparative Example 1d showed larger changes in hardness, elongation, and strength, with the largest relative performance fluctuation. This indicates that the anti-aging agents in the pipe sheath foam material of the present invention work synergistically to improve the aging resistance of the foam sheath material.

[0069] Example 2

[0070] Table 3. Formulation of pipe sheath foam material (parts by weight) in Example 2

[0071] Components Example 2 Comparative Example 2a Comparative Example 2b Comparative Example 2c EPDM rubber 6950C 70 30 70 70 LLDPE 30 70 30 30 Semi-reinforcing carbon black N774 40 40 20 40 Magnesium hydroxide 20 20 40 20 Paraffin oil 2280 30 30 30 30 Zinc oxide 3 3 3 3 stearic acid 1 1 1 1 Accelerator M 1 1 1 2 Accelerator EZ 0.5 0.5 0.5 0.5 Accelerator PX 0.5 0.5 0.5 0.5 Crosslinking agent S-80 3 3 3 3 Anti-aging agent 445 6 6 6 6 Anti-aging agent 3100 3 3 3 3 foaming agent OBSH 5 5 5 5 foaming agent AC 5 5 5 5

[0072] A pipe sheath foam material, the composition and weight parts of which are shown in Table 3, is prepared by the same method as in Example 1.

[0073] Comparative Example 2a

[0074] A pipe sheath foam material, the composition and weight parts of which are shown in Table 3, was prepared according to the method of Example 2.

[0075] Comparative Example 2b

[0076] A pipe sheath foam material, the composition and weight parts of which are shown in Table 3, was prepared according to the method of Example 2.

[0077] Comparative Example 2c

[0078] A pipe sheath foam material, the composition and weight parts of which are shown in Table 3, was prepared according to the method of Example 2.

[0079] The properties of the pipe sheath foam materials prepared in Example 2 and the four comparative examples are shown in Table 4.

[0080] Table 4. Performance of Pipe Sheath Foaming Material in Example 2

[0081]

[0082] The performance analysis led to the following conclusions:

[0083] From the room-temperature physical properties such as hardness and density, it can be found that the foaming efficiency and vulcanization efficiency of the pipe sheath foaming material of the present invention (Example 2) are both optimally combined, and the density, hardness, strength, and elongation properties reach a high level, indicating that the sheath foaming material has excellent flexibility and strength. Comparative Example 2a has too high a polyethylene content, resulting in a significant decrease in performance; Comparative Example 2b has too high a magnesium hydroxide content, resulting in a significant decrease in strength and a relatively high density; Comparative Example 2c has too high an accelerator M content, leading to a mismatch between the vulcanization rate and the foaming rate, resulting in relatively high density and hardness. Therefore, the asynchronous foaming rate and vulcanization rate of the foaming agent affect the material's hardness and density, ultimately leading to poor flexibility of the foamed material, and the vulcanization efficiency and reinforcing materials affecting the material's strength.

[0084] Example 3

[0085] This embodiment examines the effects of three preparation processes on the properties of foamed materials.

[0086] The pipe sheath foam material is made of the following components in parts by weight:

[0087] 50 parts by weight of EPDM 6950C, 50 parts by weight of LLDPE, 35 parts by weight of semi-reinforcing carbon black N774, 10 parts by weight of magnesium hydroxide, 20 parts by weight of paraffin oil 2280, 2.8 parts by weight of zinc oxide, 0.7 parts by weight of stearic acid, 1.5 parts by weight of accelerator M, 0.75 parts by weight of accelerator EZ, 0.75 parts by weight of accelerator PX, 2 parts by weight of S-80, 6 parts by weight of antioxidant 445, 3 parts by weight of antioxidant 3100, 3.5 parts by weight of foaming agent OBSH, and 5 parts by weight of foaming agent AC.

[0088] It was prepared according to the following method:

[0089] Step (1): First stage of mixing to prepare masterbatch: After the internal mixer is preheated to 60°C, LLDPE, EPDM 6950C, zinc oxide, stearic acid and antioxidant are added and mixed, and the plug is raised twice; then semi-reinforcing carbon black N774 and paraffin oil 2280 are added and mixed, and the plug is raised twice; the foaming agent OBSH, foaming agent AC and magnesium hydroxide are mixed together, and then the mixture of foaming agent OBSH, foaming agent AC and magnesium hydroxide is added and mixed, and the plug is raised twice. When the temperature of the rubber compound reaches 135°C, the material is discharged. The entire mixing process lasts for 10 minutes, and the masterbatch sheet is left to stand for 24 hours.

[0090] Step (2) Two-stage mixing to prepare compounded rubber: Add masterbatch rubber sheet, raise the bolt twice, then add accelerator and crosslinking agent S-80, mix, raise the bolt twice, mix for 8 minutes, at which time the rubber temperature reaches 115℃, pass through the open mill twice, after the rubber material with a roller gap of 6-8mm wraps around the roller, the rubber strip is discharged, cooled by blowing air, and the compounded rubber strip is obtained. The compounded rubber strip is left to stand for 24 hours.

[0091] Step (3): The equipment is ventilated and ventilated, and the temperature and speed of each working unit are set. After the temperature reaches the specified requirements, the equipment is started and the material is continuously fed and extruded into shape. The semi-finished product enters the microwave drying tunnel through the rotating roller and is foamed and vulcanized under normal pressure and without turning on the microwave. After cooling out of the box, the size is checked and the winding is carried out to continuously produce foamed sheath products.

[0092] The vulcanization foaming process is as follows: the temperatures of drying tunnel 1, drying tunnel 2, drying tunnel 3, and drying tunnel 4 are shown in Table 5; the vulcanization time in drying tunnel 1, drying tunnel 2, drying tunnel 3, and drying tunnel 4 is 4 minutes and 20 seconds, and the entire drying tunnel vulcanization process takes 17 minutes and 20 seconds.

[0093] Table 5. Process Parameters

[0094]

[0095] The properties of foamed materials prepared by different processes are shown in Table 6.

[0096] Table 6. Properties of foamed materials prepared by different processes

[0097]

[0098]

[0099] Based on performance data analysis, the following conclusions were drawn:

[0100] The room-temperature physical properties of the foamed materials, such as hardness and density, reveal that the preparation method of this invention (process 1) achieves the highest levels of foaming and vulcanization efficiency, resulting in the best overall performance in terms of density, hardness, strength, and elongation. The foamed sheath material exhibits both good softness and strength. In contrast, the foamed materials prepared using processes 2 and 3 show higher density and hardness, with slight variations in strength and elongation. This is directly related to the preparation methods, indicating that the foaming and vulcanization rates are not synchronized, leading to higher hardness and density, ultimately resulting in relatively poorer softness.

Claims

1. A pipe sheath foam material, characterized in that: It is made from components comprising the following parts by weight: 50-70 parts by weight of ethylene propylene rubber; 30-50 parts by weight of polyethylene; 40-60 parts by weight of reinforcing filler system; Plasticizer 20-40 parts by weight; 3-5 parts by weight of surfactant; The accelerator system consists of 2 to 4 parts by weight; Crosslinking agent 2-4 parts by weight; Anti-aging system: 5-10 parts by weight; 5-10 parts by weight of foaming system; The total amount of ethylene propylene rubber and polyethylene is 100 parts by weight; the ethylene propylene rubber is EPDM rubber, and the vinyl content of the EPDM rubber is 25% to 50%, ML 1+4 The Mooney viscosity at 100°C is 50–100, and the content of the third monomer ENB is 5%–10%; the polyethylene is linear low-density polyethylene. The reinforcing filler system is a mixture of carbon black and magnesium hydroxide; the weight ratio of carbon black to magnesium hydroxide is 2:1 to 4:

1. The accelerator system is a blend of accelerator M and dithioamino salt accelerator; the weight ratio of accelerator M to dithioamino salt accelerator is 1:1 to 1:2; the dithioamino salt accelerator is a combination of accelerator EZ and accelerator PX with a weight ratio of 1:1 to 1:

2. The anti-aging system is a combination of antioxidant 445 and antioxidant 3100; The foaming system is a combination of foaming agents OBSH and AC.

2. The pipe sheath foam material according to claim 1, characterized in that: The weight ratio of carbon black to magnesium hydroxide is 3:1 to 3.5:1; the carbon black is at least one of semi-reinforcing carbon black N774 or carbon black N990.

3. The pipe sheath foam material according to claim 1, characterized in that: The plasticizer is environmentally friendly paraffin oil 2280; the activator is a combination of zinc oxide and stearic acid; the weight ratio of zinc oxide to stearic acid is 2:1 to 4:1; and the crosslinking agent is sulfur S-80.

4. The pipe sheath foam material according to claim 1, characterized in that: The weight ratio of the accelerator M to the dithioamino salt accelerator is 1:

1.

5. The pipe sheath foam material according to claim 1, characterized in that: The weight ratio of antioxidant 445 to antioxidant 3100 is 2:1 to 4:

1.

6. The pipe sheath foam material according to claim 1, characterized in that: The weight ratio of the foaming agent OBSH to the foaming agent AC is 1:1 to 1:

2.

7. A method for preparing the pipe sheath foam material according to claim 1, characterized in that: Includes the following steps: Step (1): First stage of mixing to prepare masterbatch: Preheat the internal mixer to 55℃~75℃, add polyethylene, ethylene propylene rubber, activator and antioxidant, mix, and raise the plug twice; then add carbon black and plasticizer, mix, and raise the plug twice; add the foaming agent and magnesium hydroxide blend, mix, and raise the plug twice. When the temperature of the rubber compound reaches 135℃~145℃, discharge the material, roll out the sheet from the open mill, cool it with air, and obtain the masterbatch sheet. Let it stand for more than 8 hours. Step (2) Two-stage mixing preparation of compounded rubber: Add masterbatch rubber sheet, raise the bolt twice, then add accelerator and crosslinking agent, mix, raise the bolt twice, wait for the rubber temperature to reach 105℃~115℃, discharge, pass through the open mill twice, adjust the roller gap to 6~8mm, after the rubber material wraps around the roller, output rubber strip, blow air to cool, obtain compounded rubber strip, and let it stand for more than 24 hours; Step (3): The mixed rubber strip is extruded to obtain a semi-finished product. The semi-finished product enters the microwave drying tunnel for foaming and vulcanization to obtain pipeline foam sheath material.

8. The method for preparing the pipeline sheath foam material according to claim 7, characterized in that: In step (3), the foaming vulcanization is as follows: the semi-finished product passes through oven 1, oven 2, oven 3 and oven 4 in sequence. The temperature of oven 1 is 220-240℃, the temperature of oven 2 is 220-240℃, the temperature of oven 3 is 190-220℃, and the temperature of oven 4 is 190-220℃. The total time for foaming vulcanization in the oven is 15-18 minutes.

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