Self-char-forming auxiliary agent, preparation method thereof and application of self-char-forming auxiliary agent in thermal insulation material

Abstract

The invention relates to the technical field of thermal insulation materials, and particularly discloses a self-charring aid, a preparation method thereof and application of the self-charring aid in thermal insulation materials, the self-charring aid is of a nanosheet layer structure, and the self-charring aid is obtained by reacting phosphoric acid with a melamine solution and a cyanuric chloride solution. The material has excellent self-carbon formation and heat insulation performance, can solve the problems of high heat conductivity and the like of a traditional phenolic resin ablation carbon formation layer, and has the advantages of good ablation resistance, low heat conductivity and the like. The self-charring aid is used as a heat-insulating filler for preparing a polyurethane-based spraying heat-insulating material, has the advantages of high efficiency, high quality, low cost and the like, and can provide a new technical path for a heat-insulating ablative heat-insulating material of a solid engine.

Description

Technical Field

[0001] The invention relates to the technical field of thermal insulation and ablation-resistant materials for solid rocket engines, and in particular to a self-carbonizing auxiliary agent and a preparation method thereof and application thereof in thermal insulation materials. Background Art

[0002] Solid engine thermal insulation sleeve materials protect the shell from direct contact with gas, and have the functions of heat insulation, bonding and stress buffering. At present, the engine thermal insulation sleeve is made by compression molding of nitrile and EPDM rubber thermal insulation materials. Rubber compression molding is subject to vulcanization conditions. The vulcanization temperature is not easy to be too high, and the fluidity of the rubber is poor. There are problems such as poor molding quality stability, precision control and product qualification rate.

[0003] Insulation material formulas usually use phenolic resins, furfural resins, etc. as ablative resin additives to improve ablative performance, and flame retardants as additives for the void structure of the ablative carbon layer and the release of ablative heat. Some flame retardants also have their own carbon-forming properties. Intumescent flame retardants have the advantages of being halogen-free, low smoke, low toxicity, and no corrosive gas generation. They play a role in hindering heat and material transfer by decomposing and absorbing heat, and forming a porous intumescent carbon layer. When used in insulation materials, the voids in the carbon layer can be regulated to reduce the thermal conductivity of the insulation material. Traditional intumescent flame retardant systems require 2-3 flame retardant materials to achieve an intumescent flame retardant effect. For example, traditional intumescent flame retardants often need to be compounded with ammonium polyphosphate to achieve an intumescent flame retardant effect. However, this compound system has defects such as insufficient thermal stability, easy migration of ammonium polyphosphate in the polymer, and weakening of the mechanical properties of the polymer.

[0004] CN117534970 A discloses a three-in-one expansion-type functional nanofiller, which is obtained by reacting a carbon-containing organic acid aqueous solution with piperazine and a metal ion aqueous solution. However, when it is added to a polyurethane-based material, it will react with the polyurethane-based material and cannot play the role of ablation resistance. Summary of the invention

[0005] The present invention provides a self-carbonizing auxiliary agent and a preparation method thereof and application in thermal insulation materials. The self-carbonizing auxiliary agent has the advantages of high nitrogen content, high carbonization rate, good compatibility, simple preparation, special structure and the like. The self-carbonizing auxiliary agent is applied to polyurethane-based spray thermal insulation sleeve materials, can reduce the weakening effect of flame retardants on the mechanical properties of polymer resin materials, and has the advantages of low thermal conductivity, ablation-resistant thermal insulation, high molding efficiency and the like.

[0006] The technical solution of the present invention is to provide a self-carbonizing auxiliary agent, which has a nano-sheet structure and is obtained by reacting phosphoric acid with a melamine solution and a cyanuric chloride solution; the chemical structure is as follows: .

[0007] Optionally, it satisfies at least one of the following conditions: the phosphoric acid is at least one of phytic acid, phosphoric acid and adenosine triphosphate; the melamine solution is an aqueous solution of melamine and Na2CO3; and the cyanuric chloride solution is a solution of cyanuric chloride and acetone.

[0008] Optionally, the molar ratio of phosphoric acid to melamine solution and cyanuric chloride solution is 0.5~1:2~2.5:1.

[0009] The present invention also relates to a method for preparing the self-carbonizing auxiliary agent, comprising the following steps: S1, cyanuric chloride solution and melamine solution are evenly mixed under protective atmosphere and low temperature conditions to obtain a mixed liquid a; S2, mixing phosphoric acid with water to prepare a mixed liquid b; S3, adding the mixed liquid b dropwise into the mixed liquid a and mixing evenly, centrifugally washing after the reaction, drying and grinding the filter cake to obtain the carbon-forming auxiliary agent.

[0010] Optionally, the low temperature condition in S1 is 10°C~20°C, and the mixing time is 5min~10min.

[0011] Optionally, the mixed liquid b in S3 is added dropwise to the mixed liquid a, and the mixing reaction time is 0.5-1 h.

[0012] The present invention also relates to the use of the self-carbonizing auxiliary agent as a heat-insulating filler when preparing a polyurethane-based spray heat-insulating material.

[0013] Optionally, the polyurethane-based spray insulation material includes the following components in percentage by mass: spray resin: 40% to 70%, thermal insulation filler: 10% to 30%, reinforcing agent: 5% to 10%, plasticizer: 10% to 20%, and fiber filler: 5% to 15%.

[0014] Optionally, the polyurethane-based spray insulation material meets at least one of the following conditions: the spray resin is one or more of polyurethane resin, polyurethane urea resin and polyurea resin; the reinforcing agent is one or both of fumed silica and precipitated silica; the plasticizer is one or more of diphenyl octyl phosphate, toluene diphenyl phosphate and tricresyl phosphate; the fiber filler is one or more of glass fiber, aramid fiber and carbon fiber. The particle size of the fiber filler is 100 mesh to 400 mesh.

[0015] Optionally, when preparing the polyurethane-based spray insulation material, each raw material is added to the spray resin in proportion, mixed and then sprayed. The spraying pressure is 1000psi~2000psi, and the temperature of the spray slurry is 40℃~70℃.

[0016] The present invention has the following beneficial effects: The present invention adopts phosphoric acid, melamine solution and cyanuric chloride solution to react to prepare a three-in-one expandable functional self-carbonizing auxiliary agent. The self-carbonizing auxiliary agent does not react with components A and B of a polyurethane-based resin, and has the advantages of low chlorine residue, high carbonization amount, good foaming effect, high thermal stability, and not easy to hydrolyze. In addition, it has little or no damage to the mechanical properties of insulation materials. When applied in the field of insulation layers, it can reduce the expansion cavity structure of the ablated carbon layer and reduce the thermal conductivity.

[0017] The self-carbonizing auxiliary agent prepared by the present invention can be used as a flame retardant filler for polyurethane-based spray insulation materials to replace traditional phenolic resins, etc., and can have both low thermal conductivity and ablation resistance. It can solve the problem of thermal protection safety risks caused by the excessively high thermal conductivity of the rubber insulation sleeve material ablated into carbon during engine operation, and achieve the characteristics of low thermal conductivity throughout the life cycle of the polyurethane-based spray insulation sleeve from the main body to the ablation working environment. In addition, the insulation material adopts a spraying manufacturing process, which can realize the mass production and high-quality production of solid engine insulation sleeves, and has significant cost, quality and process manufacturing advantages compared to rubber-based insulation sleeve materials and compression molding processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scanning electron microscope image of the carbon-forming aid prepared in Example 1. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified.

[0021] The self-carbonizing auxiliary agent of the present invention is obtained by reacting phosphoric acid with melamine solution and cyanuric chloride solution; specifically, the phosphoric acid is at least one of phytic acid, phosphoric acid and adenosine triphosphate; the melamine solution is an aqueous solution of melamine and Na2CO3; and the cyanuric chloride solution is a solution of cyanuric chloride and acetone. The molar ratio of phosphoric acid to melamine solution and cyanuric chloride solution is (0.5-1):(1.5-2.5):1.

[0022] The specific preparation method is shown in the following examples.

[0023] Example 1 Preparation method of trinity expansion type self-carbonizing auxiliary agent (1) Add 35 g (0.19 mol) of cyanuric chloride into 300 mL of acetone to dissolve; add 40 g (0.317 mol) of melamine and 12.5 g of Na2CO3 into 100 mL of deionized water at 80°C.

[0024] (2) The aqueous solution of melamine and Na2CO3 prepared above was added dropwise into a three-necked flask containing cyanuric chloride acetone solution at a rate of 2 drops / s through a constant pressure dropping funnel, while nitrogen was introduced, and the polymerization reaction was carried out in a water bath at 10°C for 6 hours to form a mixed liquid a.

[0025] (3) Dissolve 92.4 g (0.14 mol) of phytic acid in 200 mL of pure water, stir with a glass rod and set aside. Record the mixed liquid as b. (4) Adding the mixed liquid b dropwise into the mixed liquid a, mechanically stirring at room temperature for 1.0 hour, to obtain a solution containing the target product; (5) The solid product was centrifuged, washed, dried and ground to obtain a self-carbonized functional filler powder. The centrifugal condition was 3000 r / min for 2 min; the washing condition was to use hot deionized water and acetone to wash the solid product 5 times; the drying condition was to vacuum dry at 90-100 °C for about 48 hours to constant weight. The obtained product was tested by scanning electron microscopy, and the results are shown in Figure 1 , which presents a clear nanosheet structure.

[0026] The schematic diagram of its chemical structure design and synthesis is shown below .

[0027] Example 2 Preparation method of trinity expansion type self-carbonizing auxiliary agent (1) Add 36 g of cyanuric chloride into 300 mL of acetone to dissolve; add 50 g of melamine and 12.6 g of Na2CO3 into 100 mL of deionized water at 80°C.

[0028] (2) The aqueous solution of melamine and Na2CO3 prepared above was added dropwise into the three-necked flask containing the cyanuric chloride acetone solution at a rate of 2 drops / s through a constant pressure dropping funnel, while nitrogen was introduced, and the polymerization reaction was carried out in a water bath at 10°C for 6 hours to form a mixed liquid a.

[0029] (3) Dissolve 13.8 g (0.14 mol) of phosphoric acid in 200 mL of pure water, stir with a glass rod and set aside. Record the mixed liquid as b. (4) Adding the mixed liquid b dropwise into the mixed liquid a, mechanically stirring at room temperature for 1.0 hour, to obtain a solution containing the target product; (5) The solid product was centrifuged, washed, dried, and ground to obtain a self-carbonized functional filler powder. The centrifugal condition was 2000 r / min for 1 min; the washing condition was using hot deionized water and acetone to wash the solid product 4 times; the drying condition was vacuum drying at 90-100 °C for about 24 hours to constant weight.

[0030] Example 3 Preparation method of trinity expansion type self-carbonizing auxiliary agent (1) Add 35 g of cyanuric chloride into 300 mL of acetone to dissolve; add 40 g of melamine and 12.5 g of Na2CO3 into 100 mL of deionized water at 80°C.

[0031] (2) The aqueous solution of melamine and Na2CO3 prepared above was added dropwise into the three-necked flask containing the cyanuric chloride acetone solution at a rate of 2 drops / s through a constant pressure dropping funnel, while nitrogen was introduced, and the polymerization reaction was carried out in a water bath at 10°C for 6 hours to form a mixed liquid a.

[0032] (3) Dissolve 71 g of adenosine triphosphate in 200 mL of pure water, stir with a glass rod and set aside, record as solution b; (4) Adding the mixed liquid b dropwise into the mixed liquid a, mechanically stirring at room temperature for 0.5 hours, to obtain a solution containing the target product; (5) The solid product was centrifuged, washed, dried, and ground to obtain a self-carbonized functional filler powder. The centrifugal condition was 2500 r / min for 2 min; the washing condition was using hot deionized water and acetone to wash the solid product 3 times; the drying condition was vacuum drying at 90-100 °C for about 24 hours to constant weight.

[0033] Example 4 Preparation method of trinity expansion type self-carbonizing auxiliary agent (1) Add 35 g of cyanuric chloride into 300 mL of acetone to dissolve; add 45 g of melamine and 12.5 g of Na2CO3 into 100 mL of deionized water at 80°C.

[0034] (2) The aqueous solution of melamine and Na2CO3 prepared above was added dropwise into the three-necked flask containing the cyanuric chloride acetone solution at a rate of 2 drops / s through a constant pressure dropping funnel, while nitrogen was introduced, and the polymerization reaction was carried out in a water bath at 10°C for 6 hours to form a mixed liquid a.

[0035] (3) Dissolve 89 g of adenosine triphosphate in 200 mL of pure water, stir with a glass rod and set aside, record as solution b; (4) Adding the mixed liquid b dropwise into the mixed liquid a, mechanically stirring at room temperature for 0.5 hours, to obtain a solution containing the target product; (5) The solid product was centrifuged, washed, dried, and ground to obtain a self-carbonized functional filler powder. The centrifugation condition was 2500 r / min for 2 min; the washing condition was to use hot deionized water and acetone to wash the solid product 3 times; the drying condition was to vacuum dry at 90-100 °C for about 24 hours to constant weight. The self-carbonizing additive prepared in Examples 1-4 of the present invention is used in the preparation of a polyurethane thermal insulation sleeve as a thermal insulation filler. The specific formula is shown in Table 1 below, and the following percentages are weight percentages.

[0036] Table 1

[0037] At the same time, the following comparative example is set.

[0038] Comparative Example 1 Based on Example 5, the mass of the thermal insulation filler is replaced by a mixture of ammonium polyphosphate, pentaerythritol and melamine (the mass ratio of the three is 3:1:1).

[0039] Comparative Example 2 Based on Example 6, the heat insulating filler was replaced by a mixture of triazine carbon-forming foaming agent and ammonium polyphosphate (mass ratio 1:4).

[0040] Comparative Example 3 Based on Example 8, the heat insulating filler is replaced with phenolic resin.

[0041] The materials of Examples 5 to 9 and Comparative Examples 1 to 3 were mixed to prepare slurries, and then sprayed to prepare the thermal insulation sleeve. The spraying pressure and slurry temperature were controlled as shown in Table 2.

[0042] Table 2

[0043] The prepared insulation sleeve was tested. The room temperature mechanical property test was in accordance with GB / T 528, the oxygen-acetylene wire ablation rate test was in accordance with GJB 323A, and the thermal conductivity test was in accordance with GB / T 10294. The specific properties are shown in Table 3 below.

[0044] Table 3

[0045] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A self-charring auxiliary agent, characterized in that: The self-carbonizing additive is a nano-sheet structure, which is obtained by reacting phosphoric acid with melamine solution and cyanuric chloride solution; the chemical structure is as follows: 。 2. The self-carbonizing auxiliary agent according to claim 1, characterized in that: It satisfies at least one of the following conditions: the phosphoric acid is at least one of phytic acid, phosphoric acid and adenosine triphosphate; the melamine solution is an aqueous solution of melamine and Na2CO3; and the cyanuric chloride solution is a solution of cyanuric chloride and acetone.

3. The self-charring auxiliary agent according to claim 1, characterized in that: The molar ratio of phosphoric acid to melamine solution and cyanuric chloride solution is 0.5~1:1.5~2.5:

1.

4. The method for preparing the self-carbonizing auxiliary agent according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, cyanuric chloride solution and melamine solution are evenly mixed under protective atmosphere and low temperature conditions to obtain a mixed liquid a; S2, mixing phosphoric acid with water to prepare a mixed liquid b; S3, adding the mixed liquid b dropwise into the mixed liquid a and mixing evenly, centrifugally washing after the reaction, drying and grinding the filter cake to obtain the carbon-forming auxiliary agent.

5. The preparation method according to claim 4, characterized in that: The low temperature condition in S1 is 10℃~20℃, and the mixing time is 5min~10min.

6. The preparation method according to claim 4, characterized in that: The mixed liquid b in S3 is added dropwise to the mixed liquid a, and the mixing reaction time is 0.5~1h.

7. Use of the self-carbonizing auxiliary agent according to any one of claims 1 to 3 or the self-carbonizing auxiliary agent obtained by the preparation method according to any one of claims 4 to 6 as a thermal insulation filler in the preparation of polyurethane-based spray insulation materials.

8. The use according to claim 7, characterized in that: The polyurethane-based spray insulation material comprises the following components in percentage by mass: spray resin: 40%-70%, heat insulation filler: 10%-30%, reinforcing agent: 5%-10%, plasticizer: 10%-20%, fiber filler: 5%-15%.

9. The use according to claim 8, characterized in that: The polyurethane-based spray insulation material meets at least one of the following conditions: the spray resin is one or more of polyurethane resin, polyurethane urea resin and polyurea resin; the reinforcing agent is one or both of fumed silica and precipitated silica; the plasticizer is one or more of diphenyl octyl phosphate, toluene diphenyl phosphate and tricresyl phosphate; the fiber filler is one or more of glass fiber, aramid fiber and carbon fiber.

10. The use according to claim 8, characterized in that: When preparing the polyurethane-based spray insulation material, each raw material is added to the spray resin in proportion, mixed and then sprayed. The spraying pressure is 1000psi~2000psi, and the temperature of the spray slurry is 40℃~70℃.

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