Anti-aging elastic thermal insulation material and preparation method thereof

Abstract

The invention relates to the technical field of thermal insulation materials, and provides an anti-aging elastic thermal insulation material and a preparation method thereof. An anti-aging elastic thermal insulation material comprises, by weight, 25-30 parts of nitrile rubber, 20-25 parts of polyvinyl chloride, 10-15 parts of a filler, 3-5 parts of a foaming agent, 3-5 parts of epoxidized soybean oil, 1-3 parts of stearic acid, 2-4 parts of chlorinated paraffin, 1-2 parts of polyethylene glycol, 4-6 parts of a vulcanizing agent and 3-5 parts of an auxiliary agent, and the auxiliary agent is composed of zinc oxide, an accelerant PZ and a symmetric disubstituted urea compound. By means of the technical scheme, the problem that in the prior art, due to the fact that the foaming process and the vulcanization process are not synchronous, the aging resistance of the heat insulation material is poor is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat insulation materials, and specifically, to an anti-aging elastic heat insulation material and a preparation method thereof. Background Art

[0002] Due to the combination of flexibility and heat insulation properties, elastic heat insulation materials have irreplaceable advantages in dynamic environments such as vibrating equipment and pipe deformation parts. However, traditional elastic heat insulation materials generally face the bottleneck of insufficient anti-aging performance. In the prior art, nitrile rubber and chlorinated polyethylene are often used as raw materials, and azodicarbonamide is used as a foaming agent to prepare heat insulation materials. However, the decomposition temperature of azodicarbonamide is usually around 190 - 210°C, and the vulcanization temperature of nitrile rubber is generally 150 - 180°C, resulting in asynchronous foaming and vulcanization processes, showing a phenomenon of delayed foaming. Delayed foaming means that the rubber matrix has completed vulcanization cross-linking, but the foaming agent has not fully decomposed to generate gas. At this time, foaming is difficult to expand due to the too high strength of the matrix, resulting in too small cell sizes, uneven distribution, and even pore rupture or cracks due to gas breaking through the matrix, seriously affecting the uniformity and stability of the cell structure of the material. The uneven cell structure will reduce the density of the material, making it easier for external oxygen, water vapor, and corrosive media to penetrate to the inside through the connected pores or cracks, accelerating the oxidative cleavage and hydrolysis reaction of rubber molecular chains, and seriously affecting the anti-aging performance of the heat insulation material.

[0003] Therefore, it is very necessary to propose an anti-aging elastic heat insulation material and a preparation method thereof. Summary of the Invention

[0004] The present invention proposes an anti-aging elastic heat insulation material and a preparation method thereof, which solves the problem of poor anti-aging performance of heat insulation materials caused by asynchronous foaming and vulcanization processes in related technologies.

[0005] The technical solution of the present invention is as follows: The present invention proposes an anti-aging elastic heat insulation material, which comprises the following raw material components in parts by weight: 25 - 30 parts of nitrile rubber, 20 - 25 parts of polyvinyl chloride, 10 - 15 parts of filler, 3 - 5 parts of foaming agent, 3 - 5 parts of epoxidized soybean oil, 1 - 3 parts of stearic acid, 2 - 4 parts of chlorinated paraffin, 1 - 2 parts of polyethylene glycol, 4 - 6 parts of vulcanizing agent, 3 - 5 parts of auxiliary agent, and the auxiliary agent is composed of zinc oxide, accelerator PZ, and a symmetric disubstituted urea compound.

[0006] As a further technical solution, the symmetric disubstituted urea compound includes one or more of N,N-dimethylurea, N,N-diethylurea, and N,N-diphenylurea, and preferably N,N-diphenylurea.

[0007] In the raw materials of the anti-aging elastic thermal insulation material of the present invention, the symmetric disubstituted urea compound reduces the decomposition activation energy of the foaming agent, adjusts the decomposition temperature of the foaming agent azodicarbonamide, making it more compatible with the vulcanization temperature of nitrile rubber, avoiding the defects of the cell structure caused by delayed foaming, reducing the damage to the material structure by stress concentration points. The symmetric disubstituted urea compound is preferably N,N-diphenylurea. In addition to playing the regulatory role of the symmetric disubstituted urea compound, its large phenyl side chains can hinder the attack of free radicals on the rubber molecular chain through steric hindrance effects. At the same time, the conjugated structure of the phenyl can effectively capture the active free radicals generated during the aging process, delaying the oxidation reaction process and further improving the anti-aging performance of the elastic thermal insulation material.

[0008] As a further technical solution, the mass ratio of the zinc oxide, accelerator PZ and symmetric disubstituted urea compound is 2:1:1.5 - 2.

[0009] In the raw materials of the anti-aging elastic thermal insulation material of the present invention, the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetric disubstituted urea compound with a mass ratio of 2:1:1.5 - 2. Under this proportional relationship, the balance between the foaming and vulcanization processes can be achieved, significantly improving the anti-aging performance of the elastic thermal insulation material. If the proportion of the symmetric disubstituted urea compound is too low, the decomposition temperature of the foaming agent is still significantly higher than the vulcanization temperature, and there will still be problems of delayed foaming, resulting in too small cell size and uneven distribution, destroying the uniformity and stability of the cell structure; if the proportion is too high, the decomposition temperature of the foaming agent will be too close to or lower than the starting vulcanization temperature, resulting in foaming ahead of vulcanization. At this time, the rubber matrix has not formed a cross-linking network with sufficient strength, and the gas generated by foaming is likely to escape or cause the matrix to expand out of control, resulting in cell rupture, collapse or uneven density, and even the appearance of hollow cells or perforations, forming thick and irregular cells, which also destroys the material structure and is not conducive to the anti-aging performance of the elastic thermal insulation material.

[0010] As a further technical solution, the filler includes one or more of talcum powder, carbon black, and calcium carbonate.

[0011] As a further technical solution, the filler is composed of talcum powder and carbon black with a mass ratio of 7 - 8:2. For example, it can be 7:2, 7.1:2, 7.2:2, 7.3:2, 7.4:2, 7.5:2, 7.6:2, 7.7:2, 7.8:2, 7.9:2, 8:2, and is preferably 7:2.

[0012] As a further technical solution, the foaming agent is azodicarbonamide.

[0013] In the raw materials of the anti-aging elastic heat-insulating material of the present invention, azodicarbonamide is used as the foaming agent. The decomposition products of azodicarbonamide are mainly nitrogen and carbon monoxide, and no toxic gases such as halogens and sulfur oxides are released. Moreover, compared with other foaming agents, azodicarbonamide is inexpensive, has a large gas production per unit mass, can reduce the dosage of the foaming agent per unit volume of the material, and further compress the production cost.

[0014] As a further technical solution, the vulcanizing agent is sulfur.

[0015] In the raw materials of the anti-aging elastic heat-insulating material of the present invention, sulfur is added as the vulcanizing agent. Sulfur can undergo a vulcanization reaction with high molecular polymers such as nitrile rubber and polyvinyl chloride, crosslinking the linear high molecular chains into a three-dimensional network structure. The crosslinking network formed by sulfur vulcanization has high stability, can inhibit the thermal oxidative degradation of high molecular chains in a high-temperature environment, and avoid the attenuation of mechanical properties caused by the rupture of molecular chains, thereby improving the anti-aging life.

[0016] The present invention also provides a preparation method of an anti-aging elastic heat-insulating material for preparing the above-mentioned anti-aging elastic heat-insulating material, which includes the following steps: S1. Mix the filler, foaming agent, vulcanizing agent and auxiliary agent to obtain Material I; S2. Mix nitrile rubber, polyvinyl chloride and Material I, add epoxidized soybean oil, stearic acid, chlorinated paraffin and polyethylene glycol, and obtain a rubber strip after internal mixing, open mixing and cutting the rubber; S3. The rubber strip is vulcanized and foamed to obtain the anti-aging elastic heat-insulating material.

[0017] As a further technical solution, in step S2, the internal mixing time is 15-20 min, for example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, and preferably 15 min.

[0018] As a further technical solution, in step S3, the vulcanization and foaming are carried out in three times, and the temperatures and times of the first vulcanization and foaming, the second vulcanization and foaming, and the third vulcanization and foaming are all different.

[0019] As a further technical solution, the temperature of the first vulcanization and foaming < the temperature of the second vulcanization and foaming < the temperature of the third vulcanization and foaming, and the time of the second vulcanization and foaming < the time of the first vulcanization and foaming < the time of the third vulcanization and foaming.

[0020] As a further technical solution, the temperature of the first vulcanization and foaming is 80-90 °C, for example, it can be 80 °C, 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, 89 °C, 90 °C, preferably 90 °C, and the time is 20-25 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, preferably 20 min; the temperature of the second vulcanization and foaming is 120-130 °C, for example, it can be 120 °C, 121 °C, 122 °C, 123 °C, 124 °C, 125 °C, 126 °C, 127 °C, 128 °C, 129 °C, 130 °C, preferably 120 °C, and the time is 10-15 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, preferably 10 min; the temperature of the third vulcanization and foaming is 140-160 °C, for example, it can be 140 °C, 142 °C, 145 °C, 148 °C, 150 °C, 152 °C, 155 °C, 158 °C, 160 °C, preferably 160 °C, and the time is 3-4 h, for example, it can be 3 h, 3.1 h, 3. h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h, 4 h, preferably 3.5 h.

[0021] In the preparation process of the anti-aging elastic heat-insulating material of the present invention, the vulcanization and foaming are carried out in three times. The temperature of the first vulcanization and foaming is relatively low and the time is moderate. At this stage, zinc oxide plays an active role, enhancing the molecular chain activity of nitrile rubber and laying the foundation for the subsequent vulcanization reaction. The symmetric disubstituted urea compound begins to mildly regulate the blowing agent azodicarbonamide, causing it to slowly decompose to produce a small amount of gas. During the slow heating process, the phenyl conjugate structure of the symmetric disubstituted urea compound first captures the residual free radicals in the system, inhibiting the initial oxidation reaction in advance and reducing the molecular chain damage in the initial stage of aging; the temperature of the second vulcanization and foaming is moderate and the time is short. The activity of accelerator PZ is significantly improved in this temperature range, accelerating the cross-linking reaction between the vulcanizing agent and the rubber molecular chain to form an initial network structure. The symmetric disubstituted urea compound further regulates the blowing agent to make its decomposition temperature match the vulcanization temperature, increasing the gas production rate, and the gas uniformly expands in the preliminarily cross-linked matrix to form fine closed pores; the temperature of the third vulcanization and foaming is high and the time is long. At this stage, zinc oxide and accelerator PZ cooperate to promote the complete vulcanization reaction, and the rubber matrix forms a high-strength network structure. The symmetric disubstituted urea compound stably controls the slow release of the remaining gas of the blowing agent at high temperature, filling the closed pore gaps and optimizing the pore uniformity. At the same time, its phenyl side chain covers the surface of the rubber molecular chain through steric hindrance effect, hindering the attack of free radicals; by combining the additive system with the three-stage vulcanization and foaming process, the present invention solves the core problem of the asynchronous foaming and vulcanization in the traditional process and further improves the anti-aging performance of the elastic heat-insulating material.

[0022] The working principle and beneficial effects of the present invention are as follows: Among the raw materials of the anti-aging elastic heat-insulating material of the present invention, the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetric disubstituted urea compound. The compounding of these three effectively solves the problem of asynchronous foaming and vulcanization, improves the cell structure, and enhances the anti-aging performance of the elastic heat-insulating material. In the prior art, when azodicarbonamide is used as the foaming agent and nitrile rubber is used as the raw material to prepare the heat-insulating material, there is generally a problem of asynchronous foaming process and vulcanization process, resulting in delayed foaming, which seriously affects the anti-aging performance of the heat-insulating material. In the present invention, the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetric disubstituted urea compound. Zinc oxide plays a basic activation role in the auxiliary agent system, improves the activity of rubber molecules, and creates conditions for the smooth progress of subsequent vulcanization reactions. Accelerator PZ has the characteristic of accelerating vulcanization reactions, can reduce the activation energy required for vulcanization reactions, and enables nitrile rubber to rapidly undergo vulcanization cross-linking reactions at relatively low temperatures. The symmetric disubstituted urea compound has a regulating effect on the decomposition of the foaming agent by reducing the decomposition activation energy of the foaming agent, and can cause azodicarbonamide to decompose and generate gas within a range closer to the vulcanization temperature of nitrile rubber, optimizing the foaming process. When these three components are combined into an auxiliary agent system, zinc oxide provides an activation basis, accelerator PZ accelerates vulcanization, and the symmetric disubstituted urea compound regulates foaming. The synergistic effect of the three effectively improves the problem of asynchronous foaming and vulcanization, promotes the formation of a uniform and stable cell structure, and enhances the anti-aging performance of the elastic heat-insulating material. Specific embodiments

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0024] In the following examples and comparative examples: Nitrile rubber: Model 3305E; Polyvinyl chloride: Model CPE-135A; Talc powder: The average particle size is 400 mesh; Carbon black: Model N220; Polyethylene glycol: Model PEG-1000.

[0025] Example 1 A preparation method of an anti-aging elastic heat-insulating material, comprising the following steps: S1. Mix 10 parts of filler, 3 parts of azodicarbonamide, 4 parts of sulfur and 3 parts of auxiliary agent to obtain Material I; S2. Mix 25 parts of nitrile rubber, 20 parts of polyvinyl chloride and Material I, add 3 parts of epoxidized soybean oil, 1 part of stearic acid, 2 parts of chlorinated paraffin and 1 part of polyethylene glycol, open mill after kneading for 15 min, and cut the rubber into strips after cutting; S3. Vulcanize and foam the rubber strips at 160 °C for 4 h to obtain an aging-resistant elastic heat-insulating material; The filler consists of talcum powder and carbon black with a mass ratio of 7:2; The auxiliaries consist of zinc oxide, accelerator PZ and N,N-dimethylurea with a mass ratio of 2:1:1.5.

[0026] Example 2 A preparation method of an aging-resistant elastic heat-insulating material, comprising the following steps: S1. Mix 12 parts of filler, 4 parts of azodicarbonamide, 5 parts of sulfur and 4 parts of auxiliaries to obtain Material I; S2. Mix 28 parts of nitrile rubber, 22 parts of polyvinyl chloride and Material I, add 4 parts of epoxidized soybean oil, 2 parts of stearic acid, 3 parts of chlorinated paraffin and 1.5 parts of polyethylene glycol, open mill after kneading for 15 min, and cut the rubber into strips after cutting; S3. Vulcanize and foam the rubber strips at 160 °C for 4 h to obtain an aging-resistant elastic heat-insulating material; The filler consists of talcum powder and carbon black with a mass ratio of 7:2; The auxiliaries consist of zinc oxide, accelerator PZ and N,N-dimethylurea with a mass ratio of 2:1:1.5.

[0027] Example 3 A preparation method of an aging-resistant elastic heat-insulating material, comprising the following steps: S1. Mix 15 parts of filler, 5 parts of azodicarbonamide, 6 parts of sulfur and 5 parts of auxiliaries to obtain Material I; S2. Mix 30 parts of nitrile rubber, 25 parts of polyvinyl chloride and Material I, add 5 parts of epoxidized soybean oil, 3 parts of stearic acid, 4 parts of chlorinated paraffin and 2 parts of polyethylene glycol, open mill after kneading for 15 min, and cut the rubber into strips after cutting; S3. Vulcanize and foam the rubber strips at 160 °C for 4 h to obtain an aging-resistant elastic heat-insulating material; The filler consists of talcum powder and carbon black with a mass ratio of 7:2; The auxiliaries consist of zinc oxide, accelerator PZ and N,N-dimethylurea with a mass ratio of 2:1:1.5.

[0028] Example 4 Compared with Example 1, the difference in Example 4 is that the auxiliaries consist of zinc oxide, accelerator PZ and N,N-dimethylurea with a mass ratio of 2:1:2.

[0029] Example 5 Compared with Example 4, Example 5 is different in that N,N-dimethylurea is replaced with an equal amount of N,N-diethylurea.

[0030] Example 6 Compared with Example 4, Example 6 is different in that N,N-dimethylurea is replaced with an equal amount of N,N-diphenylurea.

[0031] Example 7 Compared with Example 6, Example 7 is different in that step S3 is different. In this example, step S3 includes the following steps: The rubber strip is vulcanized and foamed at 90°C for 30 minutes and then vulcanized and foamed at 160°C for 3.5 hours to obtain the aging-resistant elastic heat insulation material.

[0032] Example 8 Compared with Example 6, Example 8 is different in that step S3 is different. In this example, step S3 includes the following steps: The rubber strip is vulcanized and foamed at 120°C for 30 minutes and then vulcanized and foamed at 160°C for 3.5 hours to obtain the aging-resistant elastic heat insulation material.

[0033] Example 9 Compared with Example 6, Example 9 is different in that step S3 is different. In this example, step S3 includes the following steps: The rubber strip is vulcanized and foamed at 90°C for 20 minutes, then vulcanized and foamed at 120°C for 10 minutes, and finally vulcanized and foamed at 160°C for 3.5 hours to obtain the aging-resistant elastic heat insulation material.

[0034] Example 10 Compared with Example 6, Example 10 is different in that step S3 is different. In this example, step S3 includes the following steps: The rubber strip is vulcanized and foamed at 90°C for 10 minutes, then vulcanized and foamed at 120°C for 20 minutes, and finally vulcanized and foamed at 160°C for 3.5 hours to obtain the aging-resistant elastic heat insulation material.

[0035] Comparative Example 1 Compared with Example 1, Comparative Example 1 is different in that the additive is composed of zinc oxide and accelerator PZ with a mass ratio of 2:1.

[0036] Comparative Example 2 Compared with Example 1, Comparative Example 2 is different in that the additive is composed of zinc oxide and N,N-dimethylurea with a mass ratio of 2:1.5.

[0037] Comparative Example 3 Compared with Example 1, Comparative Example 3 is different in that the additive is composed of accelerator PZ and N,N-dimethylurea with a mass ratio of 1:1.5.

[0038] Comparative Example 4 Compared with Example 1, the difference in Comparative Example 4 is that N,N-dimethylurea is replaced with an equal amount of N,N-dimethylthiourea.

[0039] Experimental Example 1 For the aging-resistant elastic thermal insulation materials prepared in Examples 1 to 10 and Comparative Examples 1 to 4, according to the test method specified in GB / T 17794-2021 "Flexible Cellular Rubber Thermal Insulation Products", the dimensional change rate of the test specimens was measured. The size of the test specimens was 1500 mm × 30 mm × 8000 mm, and the test conditions were 105 °C for 7 days.

[0040] The test results are shown in Table 1: Table 1 Performance test results of the aging-resistant elastic thermal insulation materials prepared in Examples 1 to 10 and Comparative Examples 1 to 4

[0041] As can be seen from Table 1, when the additives consist of zinc oxide, accelerator PZ and symmetric disubstituted urea compounds, and the temperature of the first vulcanization and foaming is 90 °C for 20 min, the temperature of the second vulcanization and foaming is 120 °C for 10 min, and the temperature of the third vulcanization and foaming is 160 °C for 3.5 h, the aging resistance of the elastic thermal insulation material can be further improved.

[0042] Experimental Example 2 1. Thermal conductivity: For the aging-resistant elastic thermal insulation material prepared in Example 1, according to the test method specified in GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method", the thermal conductivity of the test specimen was measured.

[0043] 2. Vacuum volume water absorption: For the aging-resistant elastic thermal insulation material prepared in Example 1, according to the test method specified in GB / T 17794-2021 "Flexible Cellular Rubber Thermal Insulation Products", the vacuum volume water absorption of the test specimen was measured.

[0044] 3. Moisture permeability: For the aging-resistant elastic thermal insulation material prepared in Example 1, according to the test method specified in GB / T 17794-2021 "Flexible Cellular Rubber Thermal Insulation Products", the moisture permeability of the test specimen was measured.

[0045] 4. Compression-recovery rate: For the aging-resistant elastic thermal insulation material prepared in Example 1, according to the test method specified in GB / T 17794-2021 "Flexible Cellular Rubber Thermal Insulation Products", the compression-recovery rate of the test specimen was measured.

[0046] The test results are shown in Table 2: Table 2 Performance test results of the aging-resistant elastic thermal insulation material prepared in Example 1

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An anti-aging elastic heat-insulating material, characterized in that, It comprises the following raw materials in parts by weight: 25 - 30 parts of nitrile rubber, 20 - 25 parts of polyvinyl chloride, 10 - 15 parts of filler, 3 - 5 parts of foaming agent, 3 - 5 parts of epoxidized soybean oil, 1 - 3 parts of stearic acid, 2 - 4 parts of chlorinated paraffin, 1 - 2 parts of polyethylene glycol, 4 - 6 parts of vulcanizing agent, 3 - 5 parts of auxiliary agent, and the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetric disubstituted urea compound.

2. The aging-resistant elastic heat-insulating material according to claim 1, wherein The symmetric disubstituted urea compound includes one or more of N,N - dimethylurea, N,N - diethylurea, and N,N - diphenylurea.

3. The aging-resistant elastic heat-insulating material according to claim 1, wherein, The mass ratio of the zinc oxide, accelerator PZ and symmetric disubstituted urea compound is 2:1:1.5 - 2.

4. An anti-aging elastic heat-insulating material according to claim 1, characterized in that, The filler includes one or more of talc powder, carbon black, and calcium carbonate.

5. An anti-aging elastic heat-insulating material according to claim 1, characterized in that, The foaming agent is azodicarbonamide, and the vulcanizing agent is sulfur.

6. A preparation method of an anti-aging elastic heat insulation material for preparing the anti-aging elastic heat insulation material according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1. Mix the filler, foaming agent, vulcanizing agent and auxiliary agent to obtain Material I. S2. Mix the nitrile rubber, polyvinyl chloride and Material I, add epoxidized soybean oil, stearic acid, chlorinated paraffin and polyethylene glycol, and obtain a rubber strip after internal mixing, open mixing and cutting the rubber. S3. The rubber strip is vulcanized and foamed to obtain an aging - resistant elastic heat - insulating material.

7. The preparation method of an anti-aging elastic heat insulation material according to claim 6, characterized in that, In step S2, the internal mixing time is 15 - 20 min.

8. The preparation method of an anti-aging elastic heat insulation material according to claim 6, wherein, In step S3, the vulcanization and foaming are carried out in three times, and the temperatures and times of the first - stage vulcanization and foaming, the second - stage vulcanization and foaming, and the third - stage vulcanization and foaming are all different.

9. The preparation method of an anti-aging elastic heat insulation material according to claim 8, characterized in that, The temperature of the first - stage vulcanization and foaming < the temperature of the second - stage vulcanization and foaming < the temperature of the third - stage vulcanization and foaming, and the time of the second - stage vulcanization and foaming < the time of the first - stage vulcanization and foaming < the time of the third - stage vulcanization and foaming.

10. The preparation method of an anti-aging elastic heat insulation material according to claim 8, characterized in that, The temperature of the first - stage vulcanization and foaming is 80 - 90 °C, and the time is 20 - 25 min; the temperature of the second - stage vulcanization and foaming is 120 - 130 °C, and the time is 10 - 15 min; the temperature of the third - stage vulcanization and foaming is 140 - 160 °C, and the time is 3 - 4 h.

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