Aging-resistant elastic thermal insulation material and preparation method thereof

Abstract

The present invention relates to the technical field of thermal insulation materials and discloses an aging-resistant elastic thermal insulation material and a preparation method thereof. The aging-resistant elastic thermal insulation material comprises the following raw materials by weight: 25-30 parts nitrile rubber, 20-25 parts polyvinyl chloride, 10-15 parts filler, 3-5 parts foaming agent, 3-5 parts epoxidized soybean oil, 1-3 parts stearic acid, 2-4 parts chlorinated paraffin, 1-2 parts polyethylene glycol, 4-6 parts vulcanizing agent, and 3-5 parts auxiliary agent, wherein the auxiliary agent comprises zinc oxide, an accelerator PZ, and a symmetrical disubstituted urea compound. This technical solution solves the problem of poor aging resistance of thermal insulation materials in related technologies, which is caused by the asynchronous foaming and vulcanization processes.

Description

Technical Field

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

[0002] Elastic thermal insulation materials have irreplaceable advantages in dynamic environments such as vibrating equipment and pipeline deformation areas due to their flexibility and thermal insulation properties. However, traditional elastic thermal insulation materials generally face the bottleneck of insufficient aging resistance. In the prior art, thermal insulation materials are often prepared using nitrile rubber and chlorinated polyethylene as raw materials, and azodicarbonamide as a foaming agent. 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 the foaming process and the vulcanization process being out of sync, resulting in a delayed foaming phenomenon. Delayed foaming refers to the rubber matrix having completed vulcanization and cross-linking, but the foaming agent has not yet fully decomposed to produce gas. At this time, the foaming will be difficult to expand due to the excessive strength of the matrix, resulting in small pore size and uneven distribution, and even pores or cracks caused by gas breaking through the matrix, seriously affecting the uniformity and stability of the material's pore structure. The uneven pore structure will reduce the material's density, making it easier for external oxygen, water vapor, and corrosive media to penetrate into the interior through the connecting pores or cracks, accelerating the oxidation, breakage, and hydrolysis reaction of the rubber molecular chain, and seriously affecting the aging resistance of the thermal insulation material.

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

[0004] The present invention provides an aging-resistant elastic thermal insulation material and a preparation method thereof, which solves the problem in the related art that the thermal insulation material has poor aging resistance due to the asynchrony between the foaming process and the vulcanization process.

[0005] The technical solution of the present invention is as follows: The present invention proposes an aging-resistant elastic thermal insulation material, comprising the following component 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, and 3-5 parts of auxiliary agent, wherein the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetrical disubstituted urea compound.

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

[0007] In the raw materials of the aging-resistant elastic thermal insulation material of the present invention, the symmetrical disubstituted urea compound reduces the decomposition activation energy of the foaming agent and adjusts the decomposition temperature of the foaming agent azodicarbonamide to make it more compatible with the vulcanization temperature of the nitrile rubber, thereby avoiding pore structure defects caused by foaming hysteresis and reducing the damage to the material structure caused by stress concentration points. The symmetrical disubstituted urea compound is preferably N,N-diphenylurea. In addition to exerting the regulating effect of the symmetrical disubstituted urea compound, its large phenyl side chain can hinder the attack of free radicals on the rubber molecular chain through the steric hindrance effect. At the same time, the conjugated structure of the phenyl group can effectively capture the active free radicals generated during the aging process, delay the oxidation reaction process, and further improve the aging resistance of the elastic thermal insulation material.

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

[0009] In the raw materials of the aging-resistant elastic thermal insulation material of the present invention, the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetrical disubstituted urea compound in a mass ratio of 2:1:1.5~2. Under this ratio, a balance between the foaming and vulcanization processes can be achieved, and the aging resistance of the elastic thermal insulation material can be significantly improved. If the ratio of the symmetrical 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 a problem of delayed foaming, resulting in small and uneven cell size and damage to the uniformity and stability of the cell structure; if the ratio is too high, the decomposition temperature of the foaming agent will be too close to or lower than the vulcanization starting temperature, resulting in foaming ahead of vulcanization. At this time, the rubber matrix has not yet formed a cross-linked network of sufficient strength, and the gas generated by foaming is easy to escape or cause the matrix to expand out of control, causing cell rupture, collapse or uneven density, and even hollow bubbles or perforations to form coarse and irregular cells, which also destroys the material structure and is not conducive to the aging resistance of the elastic thermal insulation material.

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

[0011] As a further technical solution, the filler is composed of talc powder and carbon black in a mass ratio of 7 to 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, preferably 7:2.

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

[0013] Among the raw materials of the aging-resistant elastic thermal insulation material of the present invention, azodicarbonamide is used as a 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. In addition, compared with other foaming agents, azodicarbonamide is low in price and has a large gas production per unit mass, which can reduce the amount of foaming agent used per unit volume of material and further reduce production costs.

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

[0015] Sulfur is added as a vulcanizing agent to the raw materials of the aging-resistant elastic thermal insulation material of the present invention. Sulfur can undergo a vulcanization reaction with high molecular polymers such as nitrile rubber and polyvinyl chloride, cross-linking linear polymer chains into a three-dimensional network structure. The cross-linked network formed by sulfur vulcanization has high stability and can inhibit the thermal oxidative degradation of the polymer chains under high temperature environments, avoiding the attenuation of mechanical properties due to molecular chain breakage, thereby improving the aging resistance life.

[0016] The present invention also provides a method for preparing an aging-resistant elastic thermal insulation material, which comprises the following steps:

[0017] S1, mixing filler, foaming agent, vulcanizing agent and additives to obtain material I;

[0018] S2, mixing nitrile rubber, polyvinyl chloride and material I, adding epoxidized soybean oil, stearic acid, chlorinated paraffin and polyethylene glycol, and obtaining rubber strips after internal mixing, open mixing and rubber cutting;

[0019] S3. The rubber strip is vulcanized and foamed to obtain an aging-resistant elastic thermal insulation material.

[0020] As a further technical solution, in step S2, the banburying time is 15 to 20 minutes, for example, it can be 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, or 20 minutes, preferably 15 minutes.

[0021] As a further technical solution, in step S3, the vulcanization and foaming are carried out three times, and the temperature and time of the first vulcanization and foaming, the second vulcanization and foaming, and the third vulcanization and foaming are all different.

[0022] As a further technical solution, the temperature of the primary vulcanization foaming is less than the temperature of the secondary vulcanization foaming and less than the temperature of the tertiary vulcanization foaming, and the time of the secondary vulcanization foaming is less than the time of the primary vulcanization foaming and less than the time of the tertiary vulcanization foaming.

[0023] As a further technical solution, the temperature of the primary vulcanization foaming is 80-90°C, for example, 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 20-25min, for example, 20min, 21min, 22min, 23min, 24min, 25min, preferably 20min; the temperature of the secondary vulcanization foaming is 120-130°C, for example, 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, The temperature of the three-stage vulcanization 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 3-4h, for example, it can be 3h, 3.1h, 3.h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, preferably 3.5h.

[0024] During the preparation process of the aging-resistant elastic thermal insulation material of the present invention, vulcanization and foaming are carried out three times. The temperature of the first vulcanization and foaming is low and the time is moderate. During this stage, zinc oxide plays an active role, enhances the molecular chain activity of the nitrile rubber, and lays the foundation for the subsequent vulcanization reaction. The symmetrical disubstituted urea compound begins to slightly adjust the foaming agent azodicarbonamide, causing it to slowly decompose and produce a small amount of gas. During the slow heating process, the phenyl conjugated structure of the symmetrical disubstituted urea compound first captures the residual free radicals in the system, inhibits the initial oxidation reaction in advance, and reduces 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 the accelerator PZ is significantly improved in this temperature range, which accelerates the cross-linking reaction between the vulcanizer and the rubber molecular chain to form an initial network structure. The compound further adjusts the foaming agent so that its decomposition temperature matches the vulcanization temperature, the gas production rate is increased, and the gas expands evenly in the matrix that has been preliminarily cross-linked to form small closed cells; the temperature of the tertiary vulcanization foaming is higher and the time is longer. During this stage, zinc oxide and the accelerator PZ work together to promote the complete vulcanization reaction, and the rubber matrix forms a high-strength network structure. The symmetrical disubstituted urea compound stably controls the slow release of the remaining gas of the foaming agent at high temperature, fills the closed cell gaps and optimizes the uniformity of the foam cells. At the same time, its phenyl side chain is covered on the surface of the rubber molecular chain through the steric hindrance effect, hindering free radical attacks; the present invention solves the core problem of the asynchronous foaming and vulcanization in the traditional process by combining the auxiliary agent system with the three-stage vulcanization foaming process, and further improves the aging resistance of the elastic thermal insulation material.

[0025] The working principle and beneficial effects of the present invention are:

[0026] The raw materials of the aging-resistant elastic thermal insulation material of the present invention include additives consisting of zinc oxide, an accelerator PZ, and a symmetrically disubstituted urea compound. The combination of these three effectively solves the problem of asynchronous foaming and vulcanization, improves the cell structure, and enhances the aging resistance of the elastic thermal insulation material. In the prior art, when using azodicarbonamide as a foaming agent and nitrile rubber as a raw material to prepare thermal insulation materials, the foaming and vulcanization processes are often asynchronous, resulting in delayed foaming and seriously affecting the aging resistance of the thermal insulation material. In the present invention, the auxiliary agent consists of zinc oxide, accelerator PZ and symmetrical 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 the subsequent vulcanization reaction. Accelerator PZ has the characteristic of accelerating the vulcanization reaction and can reduce the activation energy required for the vulcanization reaction, so that the nitrile rubber can quickly undergo a vulcanization and cross-linking reaction at a relatively low temperature. The symmetrical disubstituted urea compound has a regulating effect on the decomposition of the foaming agent by reducing the decomposition activation energy of the foaming agent, so that azodicarbonamide can be decomposed and gasified within a range closer to the vulcanization temperature of the nitrile rubber, thereby optimizing the foaming process. When these three components are combined into the auxiliary agent system, zinc oxide provides an activation basis, accelerator PZ accelerates vulcanization, and the symmetrical disubstituted urea compound regulates foaming. The three components work synergistically to effectively improve the problem of asynchronous foaming and vulcanization, promote the formation of a uniform and stable foam structure, and improve the aging resistance of the elastic thermal insulation material. DETAILED DESCRIPTION

[0027] 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 embodiments described 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 making any creative efforts are within the scope of protection of the present invention.

[0028] In the following examples and comparative examples:

[0029] Nitrile rubber: model 3305E;

[0030] Polyvinyl chloride: Model CPE-135A;

[0031] Talc: average particle size is 400 mesh;

[0032] Carbon black: Model N220;

[0033] Polyethylene glycol: Model PEG-1000.

[0034] Example 1

[0035] A method for preparing an aging-resistant elastic thermal insulation material comprises the following steps:

[0036] S1. Mix 10 parts of filler, 3 parts of azodicarbonamide, 4 parts of sulfur and 3 parts of additive to obtain material I;

[0037] S2, 25 parts of nitrile rubber, 20 parts of polyvinyl chloride and material I were mixed, 3 parts of epoxidized soybean oil, 1 part of stearic acid, 2 parts of chlorinated paraffin and 1 part of polyethylene glycol were added, and the mixture was mixed for 15 minutes and then opened for refining. The rubber was cut to obtain a rubber strip;

[0038] S3, the rubber strip is vulcanized and foamed at 160°C for 4 hours to obtain an aging-resistant elastic thermal insulation material;

[0039] The filler consists of talc and carbon black in a mass ratio of 7:2;

[0040] The additive consists of zinc oxide, accelerator PZ and N,N-dimethylurea in a mass ratio of 2:1:1.5.

[0041] Example 2

[0042] A method for preparing an aging-resistant elastic thermal insulation material comprises the following steps:

[0043] S1. Mix 12 parts of filler, 4 parts of azodicarbonamide, 5 parts of sulfur and 4 parts of additive to obtain material I;

[0044] S2, 28 parts of nitrile rubber, 22 parts of polyvinyl chloride and material I were mixed, 4 parts of epoxidized soybean oil, 2 parts of stearic acid, 3 parts of chlorinated paraffin and 1.5 parts of polyethylene glycol were added, and the mixture was mixed for 15 minutes and then opened for refining. The rubber was cut to obtain a rubber strip;

[0045] S3, the rubber strip is vulcanized and foamed at 160°C for 4 hours to obtain an aging-resistant elastic thermal insulation material;

[0046] The filler consists of talc and carbon black in a mass ratio of 7:2;

[0047] The additive consists of zinc oxide, accelerator PZ and N,N-dimethylurea in a mass ratio of 2:1:1.5.

[0048] Example 3

[0049] A method for preparing an aging-resistant elastic thermal insulation material comprises the following steps:

[0050] S1. Mix 15 parts of filler, 5 parts of azodicarbonamide, 6 parts of sulfur and 5 parts of additive to obtain material I;

[0051] S2, 30 parts of nitrile rubber, 25 parts of polyvinyl chloride and material I were mixed, 5 parts of epoxidized soybean oil, 3 parts of stearic acid, 4 parts of chlorinated paraffin and 2 parts of polyethylene glycol were added, and the mixture was mixed for 15 minutes and then opened for refining. The rubber was cut to obtain a rubber strip;

[0052] S3, the rubber strip is vulcanized and foamed at 160°C for 4 hours to obtain an aging-resistant elastic thermal insulation material;

[0053] The filler consists of talc and carbon black in a mass ratio of 7:2;

[0054] The additive consists of zinc oxide, accelerator PZ and N,N-dimethylurea in a mass ratio of 2:1:1.5.

[0055] Example 4

[0056] Compared with Example 1, Example 4 is different in that the auxiliary agent consists of zinc oxide, accelerator PZ and N,N-dimethylurea in a mass ratio of 2:1:2.

[0057] Example 5

[0058] Compared with Example 4, Example 5 is different in that N,N-dimethylurea is replaced by an equal amount of N,N-diethylurea.

[0059] Example 6

[0060] Compared with Example 4, Example 6 is different in that N,N-dimethylurea is replaced by an equal amount of N,N-diphenylurea.

[0061] Example 7

[0062] Compared with Example 6, the difference of Example 7 is that step S3 is different. In this embodiment, 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 an aging-resistant elastic insulation material.

[0063] Example 8

[0064] Compared with Example 6, Example 8 is different in that step S3 is different. In this embodiment, 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 an aging-resistant elastic insulation material.

[0065] Example 9

[0066] Compared with Example 6, the difference of Example 9 is that step S3 is different. In this embodiment, 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 an aging-resistant elastic insulation material.

[0067] Example 10

[0068] Compared with Example 6, the difference of Example 10 is that step S3 is different. In this embodiment, 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 an aging-resistant elastic insulation material.

[0069] Comparative Example 1

[0070] Compared with Example 1, the difference in Comparative Example 1 is that the auxiliary agent consists of zinc oxide and accelerator PZ in a mass ratio of 2:1.

[0071] Comparative Example 2

[0072] Compared with Example 1, Comparative Example 2 is different in that the auxiliary agent consists of zinc oxide and N,N-dimethylurea in a mass ratio of 2:1.5.

[0073] Comparative Example 3

[0074] Compared with Example 1, Comparative Example 3 is different in that the auxiliary agent consists of accelerator PZ and N,N-dimethylurea in a mass ratio of 1:1.5.

[0075] Comparative Example 4

[0076] Compared with Example 1, Comparative Example 4 is different in that N,N-dimethylurea is replaced by an equal amount of N,N-dimethylthiourea.

[0077] Experimental Example 1

[0078] The aging-resistant elastic thermal insulation materials prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were tested for dimensional change rate of the specimens according to the test method specified in GB / T 17794-2021 "Flexible Foam Rubber Insulation Products". The size of the specimens was 1500 mm × 30 mm × 8000 mm, and the test conditions were 105°C for 7 days.

[0079] The test results are shown in Table 1:

[0080] 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

[0081]

[0082] As can be seen from Table 1, when the additive consists of zinc oxide, accelerator PZ and symmetrical disubstituted urea compound, and the temperature of the first vulcanization foaming is 90°C and the time is 20 min, the temperature of the second vulcanization foaming is 120°C and the time is 10 min, and the temperature of the third vulcanization foaming is 160°C and the time is 3.5 h, the aging resistance of the elastic thermal insulation material can be further improved.

[0083] Experimental Example 2

[0084] 1. Thermal conductivity: The thermal conductivity of the aging-resistant elastic thermal insulation material prepared in Example 1 was tested according to the test method specified in GB / T 10295-2008 "Thermal insulation materials - Determination of steady-state thermal resistance and related properties - Heat flow meter method".

[0085] 2. Vacuum volume water absorption rate: The vacuum volume water absorption rate of the sample of the aging-resistant elastic thermal insulation material prepared in Example 1 was tested according to the test method specified in GB / T 17794-2021 "Flexible Foam Rubber Insulation Products".

[0086] 3. Moisture permeability: The moisture permeability of the sample of the aging-resistant elastic thermal insulation material prepared in Example 1 was tested according to the test method specified in GB / T 17794-2021 "Flexible Foam Rubber Insulation Products".

[0087] 4. Compression rebound rate: The compression rebound rate of the sample of the aging-resistant elastic thermal insulation material prepared in Example 1 was tested according to the test method specified in GB / T 17794-2021 "Flexible foam rubber insulation products".

[0088] The test results are shown in Table 2:

[0089] Table 2 Performance test results of the aging-resistant elastic thermal insulation material prepared in Example 1

[0090]

[0091] The above are only 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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An aging-resistant elastic thermal insulation material, characterized in that: The invention 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, and 3-5 parts of auxiliary agent, wherein the auxiliary agent is composed of zinc oxide, accelerator PZ and symmetrical disubstituted urea compound, and the symmetrical disubstituted urea compound is N,N'-diphenylurea; The preparation method of the aging-resistant elastic thermal insulation material comprises the following steps: S1, mixing filler, foaming agent, vulcanizing agent and additives to obtain material I; S2, mixing nitrile rubber, polyvinyl chloride and material I, adding epoxidized soybean oil, stearic acid, chlorinated paraffin and polyethylene glycol, and obtaining rubber strips after internal mixing, open mixing and rubber cutting; S3, the rubber strip is vulcanized and foamed to obtain an aging-resistant elastic thermal insulation material; In step S3, the vulcanization and foaming are carried out three times, the temperature of the first vulcanization and foaming is 80-90°C, the time is 20-25 minutes, the temperature of the second vulcanization and foaming is 120-130°C, the time is 10-15 minutes, and the temperature of the third vulcanization and foaming is 140-160°C, the time is 3-4 hours.

2. The aging-resistant elastic thermal insulation material according to claim 1, characterized in that: The mass ratio of the zinc oxide, the accelerator PZ and the symmetrical disubstituted urea compound is 2:1:1.5-2.

3. The aging-resistant elastic thermal insulation material according to claim 1, characterized in that: The filler includes one or more of talc, carbon black, and calcium carbonate.

4. The aging-resistant elastic thermal insulation material according to claim 1, characterized in that: The foaming agent is azodicarbonamide, and the vulcanizing agent is sulfur.

5. The aging-resistant elastic thermal insulation material according to claim 1, characterized in that: In step S2, the mixing time is 15 to 20 minutes.

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