Environment-friendly flame-retardant silicone rubber as well as production process and application thereof

Abstract

The invention discloses environment-friendly flame-retardant silicone rubber as well as a production process and application thereof, and belongs to the technical field of silicone rubber. Chitosan, ammonium polyphosphate, magnesium hydroxide and thermotropic liquid crystal macromolecules are added into a rubber raw material according to different sequences and proportions; the characteristic that chitosan can be used as a carbon source and the combination acting force of chitosan and other inorganic materials are fully utilized, so that a carbon layer is rapidly formed in the combustion process, the combustion reaction is prevented, and molten thermotropic liquid crystal macromolecules are added into the silicone rubber in the vulcanization process, so that the flame retardant property and the mechanical property of the silicone rubber are remarkably improved. According to the silicone rubber prepared by the method, the flame retardant property of the silicone rubber is efficiently improved by utilizing an environment-friendly and non-toxic flame-retardant material and an organic and inorganic combination effect, the silicone rubber can be used for preparing a fireproof rubber protection material, and the application field is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber, and in particular relates to an environmentally friendly flame-retardant silicone rubber and a production process and application thereof. Background Art

[0002] Silicone rubber is widely used in the fields of wires and cables, aerospace, electronic appliances, etc. due to its excellent weather resistance, electrical properties, compression set, water vapor resistance, non-toxicity and odorlessness. It is a very important synthetic rubber. Although the initial decomposition temperature of silicone rubber is very high, once ignited, it will continue to burn and release a large amount of smoke and heat, which greatly limits the application range of silicone rubber. Therefore, the flame retardant research of silicone rubber has attracted much attention.

[0003] The flame retardant effect of silicone rubber can be solved from three aspects: lowering the temperature of the combustion system, isolating the oxygen of the combustion system, and inhibiting or delaying the decomposition of combustibles in the combustion system. At present, halogen-containing flame retardants release harmful gases at high temperatures, which are harmful to human health and the environment. With the continuous improvement of the country's environmental protection requirements, halogen-based flame retardants are subject to more and more restrictions. Halogen-free flame retardants mainly include nitrogen-phosphorus flame retardants, silicon-based flame retardants, sulfonate flame retardants and inorganic flame retardants. Commonly used flame retardants for silicone rubber include platinum-containing compounds, metal hydroxides and silicates, but they all have different problems. For example, platinum-containing compound flame retardants are not only expensive, but also unstable in flame retardant performance due to their small addition amount. Metal hydroxides need to be added in large amounts to achieve a good flame retardant effect when used alone, which often deteriorates the mechanical properties of silicone rubber. The flame retardant mechanism of silicates is ceramic flame retardancy, which often requires a very high ceramic temperature and a high addition amount. These problems limit the application and development of flame-retardant silicone rubber. Summary of the invention

[0004] Based on the above problems, the purpose of the present invention is to provide an environmentally friendly flame-retardant silicone rubber and its production process and application, so as to improve the flame retardant properties of the silicone rubber while having good mechanical properties.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The present invention provides an environmentally friendly flame-retardant silicone rubber, comprising the following raw materials in parts by weight:

[0007] 60-80 parts of silicone rubber, 10-15 parts of hydroxy silicone oil, 1.5-3.0 parts of chitosan, 1.5-3.0 parts of ammonium polyphosphate, 1.5-3.0 parts of magnesium hydroxide, 1-3 parts of thermotropic liquid crystal polymer, 25-35 parts of white carbon black and 0.5-1 part of vulcanizing agent;

[0008] The silicone rubber has a vinyl content of 0.15-0.35% and a polymerization degree of 5000-10000.

[0009] Preferably, the deacetylation degree of the chitosan is 80-90%;

[0010] Preferably, the thermotropic liquid crystal polymer is A950, B950 and One of RD501;

[0011] Preferably, the vulcanizing agent is one of dipentadienyl vulcanizing agent and di-tert-butyl peroxide.

[0012] The present invention also provides a production process of environmentally friendly flame-retardant silicone rubber, comprising the following steps:

[0013] S1, adding chitosan, ammonium polyphosphate and magnesium hydroxide into a mixer, and mixing them uniformly to obtain a mixture;

[0014] S2, put the silicone rubber and hydroxy silicone oil into a mixer, add the mixture three times, add the same amount of mixture each time, and stir and mix thoroughly after each addition;

[0015] S3, putting the thermotropic liquid crystal polymer into a melting machine to melt and obtain a molten thermotropic liquid crystal polymer;

[0016] After S4 and S2 are mixed, a vulcanizing agent and a molten thermotropic liquid crystal polymer are added, and the mixture is transferred to a kneader and stirred under nitrogen protection;

[0017] S5. The rubber material after being processed by the kneading machine is transferred to the filtering rubber machine for filtration;

[0018] S6. The filtered rubber material is left to stand for 12 hours and then re-refined to obtain a sheet product.

[0019] Thermotropic liquid crystal polymers have a high melting point and have liquid fluidity after melting. They can be better mixed with silicone rubber materials, are self-flaming retardant, self-extinguishing in flames, do not drip in flames, and do not produce toxic smoke. Adding a small amount can improve the mechanical properties of rubber materials.

[0020] Preferably, the temperature of the mixer is set at 80-100°C.

[0021] Preferably, the temperature of the kneader is set at 150-180°C.

[0022] Preferably, the filter screen specification of the rubber filter is 100-200 mesh.

[0023] The present invention also provides an application of environmentally friendly flame-retardant silicone rubber, and the silicone rubber is used to prepare fireproof rubber protective materials.

[0024] Beneficial effects of the present invention:

[0025] By adding chitosan, ammonium polyphosphate and magnesium hydroxide to silicone rubber, while ensuring that no toxic gas is generated, the flame retardant properties of the material are enhanced. Chitosan can form a carbon layer during the combustion process. The amino groups of chitosan react with the groups of ammonium polyphosphate to dehydrate, releasing a large amount of ammonia and water vapor to expand the carbon layer, blocking the entry of heat and oxygen, and effectively preventing the combustion. The adsorption of chitosan on magnesium hydroxide makes it more dispersed. Magnesium hydroxide can also promote the dehydration of chitosan, absorb heat to inhibit chain reactions, and magnesium hydroxide, chitosan and ammonium polyphosphate work synergistically to achieve excellent flame retardant effects. Thermotropic liquid crystal polymers have a high limiting oxygen index and are easy to form microfibers "in situ" in the polymer matrix under the action of a force field, which improves the mechanical properties of silicone rubber while hindering heat conduction in the material. Adding thermotropic liquid crystal polymers to silicone rubber can further improve the flame retardant properties. DETAILED DESCRIPTION

[0026] 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.

[0027] Example 1

[0028] This embodiment provides an environmentally friendly flame-retardant silicone rubber, comprising the following raw materials in parts by weight:

[0029] 80 parts of silicone rubber, 15 parts of hydroxy silicone oil, 1.5 parts of chitosan, 3 parts of ammonium polyphosphate, 3 parts of magnesium hydroxide, 1 part of A950, 35 parts of white carbon black and 1 part of dipentadienyl vulcanizing agent;

[0030] The production process of the above-mentioned environmentally friendly flame-retardant silicone rubber is as follows:

[0031] S1, adding chitosan with a deacetylation degree of 80%, ammonium polyphosphate and magnesium hydroxide into a mixer, and mixing them uniformly to obtain a mixture;

[0032] S2, put the silicone rubber raw rubber (polymerization degree 5000-10000) with a vinyl content of 0.15-0.35% and hydroxy silicone oil into a mixer, set the mixer temperature to 100°C, add the mixture three times, add the same amount of the mixture each time, and stir and mix thoroughly after each addition;

[0033] S3. A950 is put into a melting machine to melt to obtain a molten thermotropic liquid crystal polymer;

[0034] After S4 and S2 are mixed, a dipentadienyl vulcanizing agent and a molten thermotropic liquid crystal polymer are added, and the mixture is transferred to a kneader, the kneader temperature is set to 180°C, and the mixture is stirred under nitrogen protection;

[0035] S5. The rubber material after being processed by the kneading machine is transferred to a rubber filter with a filter screen specification of 200 mesh for filtration;

[0036] S6. The filtered rubber material is left to stand for 12 hours and then re-refined into sheets to obtain a protective shell for electrical equipment.

[0037] Example 2

[0038] The difference from the embodiment is that the dosage of chitosan, ammonium polyphosphate and magnesium hydroxide is adjusted to: 3 parts of chitosan, 1.5 parts of ammonium polyphosphate, and 3 parts of magnesium hydroxide. The other steps are the same as in embodiment 1.

[0039] Example 3

[0040] The difference from the embodiment is that the dosage of chitosan, ammonium polyphosphate and magnesium hydroxide is adjusted to: 3 parts of chitosan, 3 parts of ammonium polyphosphate, and 1.5 parts of magnesium hydroxide. The other steps are the same as in embodiment 1.

[0041] Example 4

[0042] The difference from the embodiment is that The dosage of A950 was adjusted to 2.5 parts, and the other steps were the same as in Example 1.

[0043] Example 5

[0044] The difference from the embodiment is that The dosage of A950 was adjusted to 3 parts, and the other steps were the same as in Example 1.

[0045] Example 6

[0046] This embodiment provides an environmentally friendly flame-retardant silicone rubber, comprising the following raw materials in parts by weight:

[0047] 60 parts of silicone rubber, 10 parts of hydroxy silicone oil, 1.5 parts of chitosan, 3 parts of ammonium polyphosphate, 3 parts of magnesium hydroxide, A9501 part, white carbon black 25 parts and di-tert-butyl peroxide 0.5 parts;

[0048] The production process of the above-mentioned environmentally friendly flame-retardant silicone rubber is as follows:

[0049] S1, adding chitosan with a deacetylation degree of 90%, ammonium polyphosphate and magnesium hydroxide into a mixer, and mixing them uniformly to obtain a mixture;

[0050] S2, put the silicone rubber raw rubber (polymerization degree 5000-10000) with a vinyl content of 0.15-0.35% and hydroxy silicone oil into a mixer, set the mixer temperature to 80°C, add the mixture three times, add the same amount of the mixture each time, and stir and mix thoroughly after each addition;

[0051] S3. A950 is put into a melting machine to melt to obtain a molten thermotropic liquid crystal polymer;

[0052] After S4 and S2 are mixed, di-tert-butyl peroxide and molten thermotropic liquid crystal polymer are added, and the mixture is transferred into a kneader, the kneader temperature is set to 170°C, and the mixture is stirred under nitrogen protection;

[0053] S5. The rubber material after being processed by the kneading machine is transferred to a rubber filter with a filter screen specification of 200 mesh for filtration;

[0054] S6. The filtered rubber material is left to stand for 12 hours and then re-refined into sheets to obtain a protective shell for electrical equipment.

[0055] Example 7

[0056] This embodiment provides an environmentally friendly flame-retardant silicone rubber, comprising the following raw materials in parts by weight:

[0057] 70 parts of silicone rubber, 13 parts of hydroxy silicone oil, 1.5 parts of chitosan, 3 parts of ammonium polyphosphate, 3 parts of magnesium hydroxide, B9501 part, white carbon black 30 parts and di-tert-butyl peroxide 0.8 parts;

[0058] The production process of the above-mentioned environmentally friendly flame-retardant silicone rubber is as follows:

[0059] S1, adding chitosan with a deacetylation degree of 85%, ammonium polyphosphate and magnesium hydroxide into a mixer, and mixing them uniformly to obtain a mixture;

[0060] S2, put the silicone rubber raw rubber (polymerization degree 5000-10000) with a vinyl content of 0.15-0.35% and hydroxy silicone oil into a mixer, set the mixer temperature to 90°C, add the mixture three times, add the same amount of the mixture each time, and stir and mix thoroughly after each addition;

[0061] S3. B950 is put into a melting machine to melt to obtain a molten thermotropic liquid crystal polymer;

[0062] After S4 and S2 are mixed, di-tert-butyl peroxide and molten thermotropic liquid crystal polymer are added, and the mixture is transferred into a kneader, the kneader temperature is set to 150°C, and the mixture is stirred under nitrogen protection;

[0063] S5. The rubber material after being processed by the kneading machine is transferred to a rubber filter with a filter screen specification of 200 mesh for filtration;

[0064] S6. The filtered rubber material is left to stand for 12 hours and then re-refined into sheets to obtain a protective shell for electrical equipment.

[0065] Comparative Example 1

[0066] Different from Example 1, chitosan, ammonium polyphosphate and magnesium hydroxide are not added to the silicone rubber raw material of this comparative example, step S1 is omitted in the corresponding production process, adding the mixture is omitted in S2, and the other steps are the same as in Example 1.

[0067] Comparative Example 2

[0068] Different from Example 1, the silicone rubber raw material of this comparative example does not contain A950, in the corresponding production process, step S3 is omitted, and the addition of molten thermotropic liquid crystal polymer is omitted in S4, and the other steps are the same as those in Example 1.

[0069] Comparative Example 3

[0070] Different from Example 1, chitosan, ammonium polyphosphate, magnesium hydroxide and A950, in the corresponding production process, steps S1 and S3 are omitted, adding the mixture is omitted in S2, adding the molten thermotropic liquid crystal polymer is omitted in S4, and the other steps are the same as in Example 1.

[0071] The performance of the products prepared in Example 1 to Example 7 and Comparative Example 1 to Comparative Example 3 was tested, and the results are shown in Table 1.

[0072] The flame retardant grade test refers to the method B of GB / T 10707-2008 Rubber Combustion Performance Determination Standard: vertical combustion method.

[0073] The smoke density test refers to "GB / T 8323.2-2008 Plastic smoke generation Part 2: Single chamber method for determination of smoke density test method".

[0074] The Shore hardness test refers to GB T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1 Shore durometer method (Shore hardness) standard and adopts Shore A type durometer indentation test.

[0075] The tensile strength and elongation at break test refer to GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, in combination with Example 1 and Comparative Examples 1-3, the addition of chitosan, ammonium polyphosphate, magnesium hydroxide and thermotropic liquid crystal polymer can effectively improve the flame retardant and smoke suppression properties of silicone rubber and prevent the combustion reaction from proceeding. In Examples 1-3, the proportions of chitosan, ammonium polyphosphate and magnesium hydroxide are different. When the proportion of chitosan is high, due to its synergistic effect on other materials, the flame retardant and smoke suppression properties are significantly improved. When the proportion of magnesium hydroxide is reduced, the hardness of silicone rubber is slightly reduced. When the proportion of ammonium polyphosphate is high, the smoke suppression effect is better. In Examples 4 and 5, the proportion of thermotropic liquid crystal polymer increases, and its mechanical properties are significantly improved. In Examples 6-7, the raw rubber content is reduced. Since the proportion of other materials will increase, the hardness and elasticity of silicone rubber are affected, and the mechanical properties are not as good as in Example 1.

[0079] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly flame-retardant silicone rubber, characterized in that: The following raw materials are included by mass: 60-80 parts of silicone rubber, 10-15 parts of hydroxy silicone oil, 1.5-3.0 parts of chitosan, 1.5-3.0 parts of ammonium polyphosphate, 1.5-3.0 parts of magnesium hydroxide, 1-3 parts of thermotropic liquid crystal polymer, 25-35 parts of white carbon black and 0.5-1 part of vulcanizing agent; The silicone rubber has a vinyl content of 0.15-0.35% and a polymerization degree of 5000-10000.

2. The environmentally friendly flame-retardant silicone rubber according to claim 1, characterized in that: The deacetylation degree of the chitosan is 80-90%.

3. The environmentally friendly flame-retardant silicone rubber according to claim 1, characterized in that: The thermotropic liquid crystal polymer is A950, B950 and One of the RD501.

4. The environmentally friendly flame-retardant silicone rubber according to claim 1, characterized in that: The vulcanizing agent is one of dipentadienyl vulcanizing agent and di-tert-butyl peroxide.

5. A production process of environmentally friendly flame-retardant silicone rubber according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, adding chitosan, ammonium polyphosphate and magnesium hydroxide into a mixer, and mixing them uniformly to obtain a mixture; S2, put the silicone rubber and hydroxy silicone oil into a mixer, add the mixture three times, add the same amount of mixture each time, and stir and mix thoroughly after each addition; S3, putting the thermotropic liquid crystal polymer into a melting machine to melt and obtain a molten thermotropic liquid crystal polymer; After S4 and S2 are mixed, a vulcanizing agent and a molten thermotropic liquid crystal polymer are added, and the mixture is transferred to a kneader and stirred under nitrogen protection; S5. The rubber material after being processed by the kneading machine is transferred to the filtering rubber machine for filtration; S6. The filtered rubber material is left to stand for 12 hours and then re-refined to obtain a sheet product.

6. The production process of an environmentally friendly flame-retardant silicone rubber according to claim 5, characterized in that: The temperature of the mixer was set at 80-100°C.

7. The production process of an environmentally friendly flame-retardant silicone rubber according to claim 5, characterized in that: The temperature of the kneader was set at 150-180°C.

8. The production process of an environmentally friendly flame-retardant silicone rubber according to claim 5, characterized in that: The filter screen specification of the rubber filter is 100-200 meshes.

9. An application of environmentally friendly flame-retardant silicone rubber, characterized in that: The environmentally friendly flame-retardant silicone rubber as described in claims 1-4 is used to prepare fireproof rubber protective materials.

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