Modified foam and preparation method thereof

Abstract

The invention provides modified foam and a preparation method thereof, and belongs to the technical field of polyurethane. The preparation method comprises the following steps: uniformly mixing polyether polyol, distilled water, silicone oil, diethanol amine and a flame retardant, adding an initiator and isocyanate, heating, stirring, reacting, foaming, heating, curing, taking out, and standing at room temperature, thereby obtaining the modified foam. By adding the prepared flame retardant, the flame retardance of the prepared modified foamed plastic can be obviously improved, the antibacterial effect of the modified foamed plastic can be obviously improved, the mechanical property of the foamed plastic can be improved to a certain extent, the preparation method is simple, the performance of the modified foamed plastic can be obviously improved, and the modified foamed plastic has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane, and in particular to a modified foam and a preparation method thereof. Background Art

[0002] Conductive foam generally consists of a foam body and a conductive shell covering the outer surface of the foam body. As a gap shielding material, conductive foam has the characteristics of light material, compressibility and conductivity. It is often used in gaps in electronic and electrical equipment to provide conductive connection and shielding. At present, the material of the foam body is mainly polyurethane or polyethylene. Through the foaming process, the foam body has the characteristics of compressibility and resilience. However, polyurethane or polyethylene has the defect of poor flame retardancy.

[0003] In order to improve the flame retardant performance of the conductive foam, a flame retardant layer is provided between the conductive shell and the foam body. For example, the invention with patent publication number CN115534456A discloses a flame retardant conductive foam, which is provided with a flame retardant layer inside the conductive cloth and between the flame retardant foams, and the flame retardant layer is prepared by coating the outer surface of the flame retardant foam with a flame retardant liquid in a layer-by-layer self-assembly manner. However, the above scheme still has the following defects: First, the setting of the flame retardant layer increases the overall size of the conductive foam, and as the design of electronic products becomes thinner and lighter, the gaps inside the product components become smaller and smaller. The size of the conductive foam obtained by this scheme is difficult to control below 0.3mm, and it is difficult to meet the filling of narrow gaps. Second, in order to ensure the flame retardant effect, the flame retardant layer needs to maintain a certain thickness. After actual testing, it is difficult to play a flame retardant role when the thickness of the flame retardant layer is small, and the flame retardant grade is reduced to UL94-HF2.

[0004] The Chinese invention patent with the patent publication number CN113462308A discloses a topological conductive foam material and a construction method thereof, wherein the topological foam material comprises the following raw materials by weight: 90-100 parts of polyethylene, 40-60 parts of carbon black, 30-50 parts of conductive cloth, 4-12 parts of polyethylene pyridine, 3-15 parts of chlorinated polyethylene, 3-8 parts of foaming agent, 0.5-3 parts of sensitizer, 0.5-6 parts of antioxidant, 0.3-4 parts of melamine, and 0.3-4 parts of melamine cyanurate. The purpose of the invention is to network the various properties of the conductive foam on the applied equipment through a topological connection method to improve the performance of the use. However, its flame retardant performance is poor, which limits its application range. Summary of the invention

[0005] The purpose of the present invention is to propose a modified foam and a preparation method thereof. By adding a prepared flame retardant, the flame retardancy of the prepared modified foam can be significantly improved, and its antibacterial effect can also be significantly improved. The mechanical properties of the foam can also be improved to a certain extent. The preparation method is simple, can significantly improve the performance of the modified foam, and has broad application prospects.

[0006] The technical solution of the present invention is achieved as follows: the present invention provides a method for preparing modified foam, comprising the steps of uniformly mixing polyether polyol, distilled water, silicone oil, diethanolamine and flame retardant, adding initiator and isocyanate, heating and stirring to react and foam, heating and maturing, taking out and placing at room temperature to obtain modified foam; the flame retardant is aluminum oxide microspheres surface-modified with tannic acid, the surface of which reacts with phosphorus oxychloride and hexachlorocyclotriphosphazene, and then chelates magnesium and iron elements to obtain the flame retardant.

[0007] As a further improvement of the present invention, the polyether polyol is at least one of polyoxypropylene glycol, polytetramethylene glycol, and tetramethylene glycol; the isocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; the silicone oil is silicone oil L580, and the initiator is stannous octoate or dibutyltin dilaurate.

[0008] As a further improvement of the present invention, the mass ratio of the polyether polyol, distilled water, silicone oil, diethanolamine, flame retardant, initiator and isocyanate is 100:3-4:1.3-1.8:0.2-0.4:3-5:0.8-1:37-45.

[0009] As a further improvement of the present invention, the temperature of the heating and stirring reaction foaming is 40-45°C, the time is 3-5 minutes, the temperature of the heating and aging is 65-75°C, the time is 2-4 hours, and the time of standing at room temperature is 12-20 hours.

[0010] As a further improvement of the present invention, the preparation method of the flame retardant is as follows: S1. Preparation of alumina microspheres: adding aluminum isopropoxide to ethanol, adding ammonia water to adjust the pH value of the solution, heating and stirring to react, centrifuging, washing, drying, calcining, ball milling, and obtaining alumina microspheres; S2. Preparation of modified alumina microspheres: adding alumina microspheres to water, adding tannic acid and a catalyst, heating and stirring to react, centrifuging, washing, drying, and obtaining modified alumina microspheres; S3. Preparation of flame-retardant modified alumina microspheres: adding modified alumina microspheres to toluene, adding phosphorus oxychloride and hexachlorocyclotriphosphazene under the protection of inert gas, dropping triethylamine, heating and stirring to react, centrifuging, washing, drying, and obtaining flame-retardant modified alumina microspheres; S4. Chelating metal ions: adding flame-retardant modified alumina microspheres to water, adding magnesium salt and iron salt, stirring to react, centrifuging, washing, drying, and obtaining a flame retardant.

[0011] As a further improvement of the present invention, the mass ratio of aluminum isopropoxide to ethanol in step S1 is 17-20:120-150, the pH value of the adjusted solution is 9-10, the temperature of the heated and stirred reaction is 45-55°C, the time is 3-5h, and the calcination temperature is 400-500°C, and the time is 1-3h.

[0012] As a further improvement of the present invention, the mass ratio of the alumina microspheres, tannic acid and catalyst in step S2 is 10:12-15:1-2, the catalyst is a Tris-HCl solution with a pH of 8.5-9.5, the temperature of the heating and stirring reaction is 40-50°C, and the time is 2-4h.

[0013] As a further improvement of the present invention, the mass ratio of the modified alumina microspheres, phosphorus oxychloride, hexachlorocyclotriphosphazene and triethylamine in step S3 is 100:12-15:8-12:5-7, and the temperature of the heating and stirring reaction is 90-100° C. and the time is 3-5 hours.

[0014] As a further improvement of the present invention, the mass ratio of the flame retardant modified alumina microspheres, magnesium salt and iron salt in step S4 is 100:3-5:1-3, the stirring reaction time is 20-40 minutes, the magnesium salt is magnesium chloride or magnesium nitrate, and the iron salt is at least one of ferric chloride, ferric nitrate or ferric sulfate.

[0015] The present invention further protects a modified foam obtained by the above-mentioned preparation method.

[0016] The invention has the following beneficial effects: the invention prepares a flame retardant, with alumina as a carrier, having high thermal stability and fire resistance, helping to improve the stability of the composite material at high temperature to a certain extent, and having high mechanical strength, and then the surface of the carrier is modified by tannic acid, with a large number of active groups such as carboxyl groups on the surface, reacting with phosphorus oxychloride and hexachlorocyclotriphosphazene, so that phosphorus oxychloride and hexachlorocyclotriphosphazene are grafted on the surface of the microsphere, and a flame retardant containing N and P is prepared, and when thermally decomposed, phosphoric acid, metaphosphoric acid and polyphosphoric acid and other substances can be generated, and a non-volatile protective film can be formed on the surface of the polymer material to isolate the air, thereby achieving a flame retardant effect, and after thermal decomposition, carbon dioxide, ammonia, nitrogen, water vapor and other non-combustible gases can be released, and these gases dilute the oxygen concentration in the combustion area, thereby inhibiting the continuation of combustion, and can also form a carbon layer. These reactions include the acid source providing the acid required for the esterification reaction, the carbon source providing the hydroxyl group or other groups, and the gas source providing the gas required for expansion and foaming. The water vapor and non-flammable gas produced during the reaction cause the system to expand and foam, forming a porous foam carbon layer, which further enhances the flame retardant effect. At the same time, N and P also have a synergistic effect.

[0017] The present invention further fixes the metal ions on the surface of the prepared flame-retardant modified alumina microspheres after complexing with metal ions. The introduction of metal ions can not only give play to the excellent catalytic carbonization ability of metal ions, but also take advantage of the high phosphorus content to play a flame retardant role, so as to achieve a better flame retardant effect, while giving the foam better properties, such as antibacterial and electrical conductivity. In addition, magnesium ions are easy to form magnesium oxide during combustion. MgO is an oxidant with flame retardant properties. When it contacts with fuel, it can effectively absorb the heat generated by combustion and form a protective layer to prevent the fuel from continuing to burn. Iron ions can absorb heat energy at high temperatures to prevent the combustion of materials, thereby playing a flame retardant effect, and the two have a synergistic effect.

[0018] The invention can significantly improve the flame retardancy of the prepared modified foam by adding the prepared flame retardant, significantly improve its antibacterial effect, and improve the mechanical properties of the foam to a certain extent. The preparation method is simple, can significantly improve the performance of the modified foam, and has broad application prospects. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0020] Preparation Example 1 Preparation of flame retardant Here’s how: S1. Preparation of alumina microspheres: 17 g of aluminum isopropoxide was added to 120 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9, heated to 45°C, stirred for 3 h, centrifuged, washed, dried, calcined at 400°C for 1 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 12 g of tannic acid and 1 g of a catalyst were added, the mixture was heated to 40° C., stirred for reaction for 2 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 8.5; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 12 g of phosphorus oxychloride and 8 g of hexachlorocyclotriphosphazene were added, and 5 g of triethylamine was added dropwise, heated to 90 ° C, stirred for 3 h, centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres; S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 3 g of magnesium chloride and 1 g of ferric chloride were added, and the mixture was stirred for 20 min, centrifuged, washed, and dried to obtain a flame retardant.

[0021] Preparation Example 2 Preparation of flame retardant Here’s how: S1. Preparation of alumina microspheres: 20 g of aluminum isopropoxide was added to 150 g of ethanol, and ammonia was added to adjust the pH value of the solution to 10, heated to 55°C, stirred for 5 h, centrifuged, washed, dried, calcined at 500°C for 1-3 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 15 g of tannic acid and 2 g of a catalyst were added, the mixture was heated to 50° C., stirred for 4 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9.5; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 15 g of phosphorus oxychloride and 12 g of hexachlorocyclotriphosphazene were added, and 7 g of triethylamine was added dropwise, heated to 100 ° C, stirred for 5 h, centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres; S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 5 g of magnesium nitrate and 3 g of ferric sulfate were added, and the mixture was stirred for 40 min, centrifuged, washed, and dried to obtain a flame retardant.

[0022] Preparation Example 3 Preparation of flame retardant Here’s how: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 13 g of phosphorus oxychloride and 10 g of hexachlorocyclotriphosphazene were added, 6 g of triethylamine was added dropwise, and the mixture was heated to 95° C. and stirred for 4 h. The mixture was centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres. S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 4 g of magnesium chloride and 2 g of ferric nitrate were added, and the mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0023] Comparative Preparation Example 1 Compared with Preparation Example 3, the difference is that step S2 is not performed.

[0024] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S1. Preparation of flame-retardant modified alumina microspheres: 100 g of alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 13 g of phosphorus oxychloride and 10 g of hexachlorocyclotriphosphazene were added, and 6 g of triethylamine was added dropwise, and the mixture was heated to 95° C. and stirred for 4 h. The mixture was centrifuged, washed, and dried to obtain flame-retardant modified alumina microspheres. S3. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 4 g of magnesium chloride and 2 g of ferric nitrate were added, and the mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0025] Comparative Preparation Example 2 Compared with Preparation Example 3, the difference is that phosphorus oxychloride is not added in step S3.

[0026] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; The catalyst is a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, 23 g of hexachlorocyclotriphosphazene was added under nitrogen protection, 6 g of triethylamine was added dropwise, heated to 95 ° C, stirred for 4 h, centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres; S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 4 g of magnesium chloride and 2 g of ferric nitrate were added, and the mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0027] Comparative Preparation Example 3 Compared with Preparation Example 3, the difference is that hexachlorocyclotriphosphazene is not added in step S3.

[0028] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, 23 g of phosphorus oxychloride was added under nitrogen protection, 6 g of triethylamine was added dropwise, heated to 95 ° C, stirred for 4 h, centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres; S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, 4 g of magnesium chloride and 2 g of ferric nitrate were added, and the mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0029] Comparative Preparation Example 4 Compared with Preparation Example 3, the difference is that step S3 is not performed.

[0030] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Chelating metal ions: 100 g of modified alumina microspheres were added to 500 mL of water, 4 g of magnesium chloride and 2 g of ferric nitrate were added, and the mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0031] Comparative Preparation Example 5 Compared with Preparation Example 3, the difference is that magnesium chloride is not added in step S4.

[0032] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 13 g of phosphorus oxychloride and 10 g of hexachlorocyclotriphosphazene were added, 6 g of triethylamine was added dropwise, and the mixture was heated to 95° C. and stirred for 4 h. The mixture was centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres. S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, and 6 g of ferric nitrate was added. The mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0033] Comparative Preparation Example 6 Compared with Preparation Example 3, the difference is that no ferric nitrate is added in step S4.

[0034] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: 100 g of modified alumina microspheres were added to 500 mL of toluene, and under nitrogen protection, 13 g of phosphorus oxychloride and 10 g of hexachlorocyclotriphosphazene were added, 6 g of triethylamine was added dropwise, and the mixture was heated to 95° C. and stirred for 4 h. The mixture was centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres. S4. Chelating metal ions: 100 g of flame retardant modified alumina microspheres were added to 500 mL of water, and 6 g of magnesium chloride was added. The mixture was stirred for 30 min, centrifuged, washed, and dried to obtain a flame retardant.

[0035] Comparative Preparation Example 7 Compared with Preparation Example 3, the difference is that step S4 is not performed.

[0036] The details are as follows: S1. Preparation of alumina microspheres: 18 g of aluminum isopropoxide was added to 135 g of ethanol, and ammonia was added to adjust the pH value of the solution to 9.5, heated to 50°C, stirred for 4 h, centrifuged, washed, dried, calcined at 450°C for 2 h, and ball-milled for 1 h to obtain alumina microspheres; S2. Preparation of modified alumina microspheres: 10 g of alumina microspheres were added to 200 mL of water, 13 g of tannic acid and 1.5 g of a catalyst were added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain modified alumina microspheres; the catalyst was a Tris-HCl solution with a pH of 9; S3. Preparation of flame retardant modified alumina microspheres: Add 100 g of modified alumina microspheres into 500 mL of toluene, add 13 g of phosphorus oxychloride and 10 g of hexachlorocyclotriphosphazene under nitrogen protection, add 6 g of triethylamine dropwise, heat to 95°C, stir to react for 4 hours, centrifuge, wash, and dry to obtain flame retardant modified alumina microspheres, which are flame retardants.

[0037] Example 1

[0038] The present embodiment provides a method for preparing a modified foam. 100 g of polyoxypropylene glycol N220, 3 g of distilled water, 1.3 g of silicone oil L580, 0.2 g of diethanolamine, and 3 g of the flame retardant prepared in Preparation Example 1 are mixed for 30 minutes, 0.8 g of stannous octoate and 37 g of toluene diisocyanate are added, the mixture is heated to 40° C., stirred to react and foam for 3 minutes, heated to 65° C., aged for 2 hours, taken out and placed at room temperature for 12 hours, and the modified foam is prepared.

[0039] Example 2

[0040] The present embodiment provides a method for preparing a modified foam. 100 g of polytetrahydrofuran diol 1000, 4 g of distilled water, 1.8 g of silicone oil L580, 0.4 g of diethanolamine, and 5 g of the flame retardant prepared in Preparation Example 2 are mixed for 30 minutes, 1 g of stannous octoate and 45 g of toluene diisocyanate are added, the mixture is heated to 45° C., stirred to react and foam for 5 minutes, heated to 75° C., aged for 4 hours, taken out and placed at room temperature for 12-20 hours, and the modified foam is prepared.

[0041] Example 3

[0042] The present embodiment provides a method for preparing a modified foam. 100 g of polytetramethylene glycol 1000, 3.5 g of distilled water, 1.6 g of silicone oil L580, 0.3 g of diethanolamine, and 4 g of the flame retardant prepared in Preparation Example 3 are mixed for 30 minutes, 0.9 g of dibutyltin dilaurate and 41 g of toluene diisocyanate are added, the mixture is heated to 42° C., stirred for foaming reaction for 4 minutes, heated to 70° C., aged for 3 hours, taken out and placed at room temperature for 16 hours, and the modified foam is prepared.

[0043] Comparative Examples 1-7 Compared with Example 3, the difference is that the flame retardants are prepared from Comparative Preparation Examples 1-7 respectively.

[0044] Comparative Example 8 Compared with Example 3, the difference is that no flame retardant is added.

[0045] The details are as follows: The present embodiment provides a method for preparing a modified foam. 100 g of polytetramethylene glycol 1000, 3.5 g of distilled water, 1.6 g of silicone oil L580, and 0.3 g of diethanolamine are mixed for 30 minutes, 0.9 g of dibutyltin dilaurate and 41 g of toluene diisocyanate are added, the mixture is heated to 42° C., stirred for foaming reaction for 4 minutes, heated to 70° C., aged for 3 hours, taken out and placed at room temperature for 16 hours, and the modified foam is obtained.

[0046] Test Example 1 The modified foams prepared in Examples 1-3 of the present invention and Comparative Examples 1-8 were tested using a functional mechanical testing instrument according to GB / T6669-2008 "Determination of permanent compression set of soft foams", GB / T 10807-2006 "Determination of hardness of soft polymeric foam materials (indentation method)" and GB / T 6344-2008 "Determination of tensile strength and elongation at break of soft foams". The samples to be tested were cut into rectangular blocks with a length, width and height of 50 mm × 50 mm × 25 mm, and 5 samples were tested in each group to test the mechanical properties of the prepared samples.

[0047] The results are shown in Table 1.

[0048] Table 1

[0049] It can be seen from the above table that the modified foams prepared in Examples 1-3 of the present invention have good mechanical properties.

[0050] Test Example 2 The modified foams prepared in Examples 1-3 of the present invention and Comparative Examples 1-8 were subjected to performance tests.

[0051] The limiting oxygen index (LOI) of the sample is tested: the test adopts GB / T2406-2008.

[0052] The combustion growth rate index and total heat release within 600s of the sample are tested in accordance with GB / T20284-2006.

[0053] The sample was cut into test samples with a size of 2mm×2mm×2mm. The positive and negative electrodes of the electrochemical workstation were connected with copper wires at both ends of the test sample. The single potential step chronoamperometry was called, and the measurement voltage was set to U=10V and the measurement time to 10s. After the current curve stabilized, the average value was taken to calculate the conductivity.

[0054] The sample was tested according to the test method 1 of GB21551.2-2010. Test bacteria: Escherichia coli (AATCC8099).

[0055] The results are shown in Table 2.

[0056] Table 2

[0057] It can be seen from the above table that the modified foams prepared in Examples 1-3 of the present invention have good flame retardancy and electrical conductivity.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified foam, characterized in that: The polyether polyol, distilled water, silicone oil, diethanolamine and flame retardant are uniformly mixed, an initiator and isocyanate are added, the mixture is heated and stirred to react and foam, the mixture is heated and aged, and the mixture is taken out and placed at room temperature to obtain a modified foam. The flame retardant is alumina microspheres surface-modified with tannic acid, the surface of which is reacted with phosphorus oxychloride and hexachlorocyclotriphosphazene, and then chelated with magnesium and iron elements to obtain the flame retardant. The mass ratio of the polyether polyol, distilled water, silicone oil, diethanolamine, flame retardant, initiator and isocyanate is 100:3-4:1.3-1.8:0.2-0.4:3-5:0.8-1:37-45.

2. The preparation method according to claim 1, characterized in that: The polyether polyol is at least one of polyoxypropylene glycol, polytetramethylene glycol, and tetramethylene glycol-oxypropylene copolymer glycol; the isocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; the silicone oil is silicone oil L580, and the initiator is stannous octoate or dibutyltin dilaurate.

3. The preparation method according to claim 1, characterized in that: The temperature of the heating and stirring reaction foaming is 40-45°C, the time is 3-5 minutes, the temperature of the heating and aging is 65-75°C, the time is 2-4 hours, and the time of standing at room temperature is 12-20 hours.

4. The preparation method according to claim 1, characterized in that: The flame retardant preparation method is as follows: S1. Preparation of alumina microspheres: adding aluminum isopropoxide to ethanol, adding ammonia water to adjust the pH value of the solution, heating and stirring to react, centrifuging, washing, drying, calcining, ball milling, and obtaining alumina microspheres; S2. Preparation of modified alumina microspheres: adding alumina microspheres to water, adding tannic acid and a catalyst, heating and stirring to react, centrifuging, washing, drying, and obtaining modified alumina microspheres; S3. Preparation of flame retardant modified alumina microspheres: The modified alumina microspheres were added to toluene, phosphorus oxychloride and hexachlorocyclotriphosphazene were added under inert gas protection, triethylamine was added dropwise, the reaction was heated and stirred, centrifuged, washed, and dried to obtain flame retardant modified alumina microspheres; S4. Chelating metal ions: adding flame retardant modified alumina microspheres into water, adding magnesium salt and iron salt, stirring to react, centrifuging, washing, and drying to obtain a flame retardant.

5. The preparation method according to claim 4, characterized in that: In step S1, the mass ratio of aluminum isopropoxide to ethanol is 17-20:120-150, the pH value of the adjusted solution is 9-10, the temperature of the heated stirring reaction is 45-55° C., the time is 3-5 hours, and the calcination temperature is 400-500° C., and the time is 1-3 hours.

6. The preparation method according to claim 4, characterized in that: The mass ratio of the alumina microspheres, tannic acid and catalyst in step S2 is 10:12-15:1-2, the catalyst is a Tris-HCl solution with a pH of 8.5-9.5, the temperature of the heating and stirring reaction is 40-50° C., and the time is 2-4 hours.

7. The preparation method according to claim 4, characterized in that: In step S3, the mass ratio of the modified alumina microspheres, phosphorus oxychloride, hexachlorocyclotriphosphazene, and triethylamine is 100:12-15:8-12:5-7, and the temperature of the heating and stirring reaction is 90-100° C. and the time is 3-5 hours.

8. The preparation method according to claim 4, characterized in that: The mass ratio of the flame retardant modified alumina microspheres, magnesium salt and iron salt in step S4 is 100:3-5:1-3, the stirring reaction time is 20-40 minutes, the magnesium salt is magnesium chloride or magnesium nitrate, and the iron salt is at least one of ferric chloride, ferric nitrate or ferric sulfate.

9. A modified foam obtained by the preparation method according to any one of claims 1 to 8.

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