Sodium silicate flame retardant and preparation method thereof

Abstract

The invention discloses a sodium silicate flame retardant and a preparation method thereof, and relates to the technical field of flame retardants, the preparation method of the sodium silicate flame retardant comprises the following steps: adding an organic solvent and sodium silicate into a reaction container, adding 1, 3, 5-tris [3-(trimethoxysilyl) propyl]-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-triketone after the sodium silicate is uniformly dispersed, and stirring for 1-2 hours; heating to a reflux state, carrying out a heat preservation reaction in the reflux state, filtering a reaction solution after the reaction is finished, and carrying out vacuum drying on filter residues to obtain a sodium silicate flame retardant; the sodium silicate is subjected to surface modification, on one hand, the original flame retardant property of the sodium silicate can be efficiently utilized, and on the other hand, the sodium silicate can be endowed with certain plasticizing property, so that the sodium silicate has the dual effects of flame retardance and plasticizing, and the market competitiveness of the sodium silicate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardants, and in particular to a sodium silicate flame retardant and a preparation method thereof. Background Art

[0002] Sodium silicate is widely used as a flame retardant in the fields of textiles, papermaking, plastics and rubber. Its flame retardant mechanism includes the following aspects:

[0003] 1. Heat absorption and cooling: The silicate ions in sodium silicate can absorb a large amount of heat, and its heat capacity is much higher than that of water of the same mass. When encountering a fire source, the silicate will absorb the heat in the combustion process, lower the local temperature, make the material less likely to burn, and thus interrupt the heat chain reaction process of the fire.

[0004] 2. Forming a heat-insulating layer: When heated, sodium silicate will quickly dehydrate into amorphous silica gel, forming a glassy heat-insulating layer on the surface of the material. This layer of gel has a low thermal conductivity, which can block the conduction of heat into the material and play a good role in heat insulation.

[0005] 3. Dilute combustible gas: Sodium silicate will release silicon dioxide and water vapor at high temperature. These gases will dilute the concentration of combustible gas, reduce its flammability and inhibit the spread of fire.

[0006] 4. Sealing material surface: Under high temperature conditions, the sodium silicate solution will polymerize to form a layer of glass film, covering the surface of the combustible material, cutting off the contact between the material and oxygen in the air, preventing continuous combustion, and playing a role of sealing and isolation.

[0007] 5. Absorb free radicals: A large number of free radicals will be produced in the early stage of material combustion to promote the continued reaction. Silicate can absorb free radicals, inhibit the chain propagation of the combustion reaction, and slow down the spread of fire.

[0008] 6. Strengthen material structure: Under high temperature conditions, sodium silicate solution will penetrate into the pores of the material and polymerize and solidify, thereby enhancing the structural strength of the cellulose material and improving its fire resistance.

[0009] Although sodium silicate can be used as a flame retardant to improve the flame retardant properties of materials, it is hygroscopic and easily absorbs moisture in the air. When the absorbed moisture exceeds a certain amount, sodium silicate will agglomerate or undergo hydrolysis, affecting its effect on improving the flame retardant properties of the material. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a sodium silicate flame retardant and a preparation method thereof. The flame retardant has both flame retardant and plasticizing functions, and can improve the mechanical properties of the material while improving the flame retardant properties of the material.

[0011] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0012] One of the purposes of the present invention is to provide a method for preparing a sodium silicate flame retardant. The method comprises the following steps: adding an organic solvent and sodium silicate into a reaction container, adding 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione after the sodium silicate is evenly dispersed, heating the container to a reflux state, and keeping the temperature under the reflux state for reaction. After the reaction is completed, filtering the reaction solution, and vacuum drying the filter residue to obtain the sodium silicate flame retardant.

[0013] In a further technical solution, the reaction container is dried before use to remove moisture in the reaction container. For the reaction bottle, oven drying, hot air drying, organic solvent (acetone or anhydrous ethanol) drying can be used; for the reaction kettle, hot air drying, air flow drying or vacuum drying can be used.

[0014] In a further technical solution, the sodium silicate is dried before use, which can be done by oven drying or vacuum drying, in order to remove free water and adsorbed water in the sodium silicate.

[0015] In a further technical solution, the organic solvent is toluene. The boiling point of toluene is about 110°C. The residual toluene in the product can be removed by vacuum drying during post-treatment, and toluene has good compatibility with 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0016] In a further technical solution, the organic solvent and 3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione are dehydrated before use, and a desiccant dehydration method can be used. The desiccant includes molecular sieves, silica gel, anhydrous calcium chloride, anhydrous magnesium sulfate, etc.

[0017] The present invention performs a drying treatment on the reaction container, the reaction solvent and the reaction raw materials, so that the reaction is carried out under anhydrous conditions. Under anhydrous conditions, the siloxane group in the molecular structure of 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione directly reacts with the surface hydroxyl group of sodium silicate to generate -Si-O-Si- bonds, thereby realizing the surface modification of sodium silicate and simultaneously realizing the combination of inorganic silicon material and organic silicon material, so that sodium silicate can have the performance of plasticizer and the flame retardant effect of sodium silicate will not be reduced.

[0018] In a further technical solution, the sodium silicate is dispersed by mechanical stirring, magnetic stirring or ultrasonic treatment. Since sodium silicate is insoluble in organic solvents, in order to increase the contact area between sodium silicate and 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, mechanical stirring, magnetic stirring or ultrasonic treatment can be used to promote the uniform dispersion of sodium silicate in organic solvents.

[0019] In a further technical solution, the mass ratio of the sodium silicate to 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione is (1.5-2):1. The amount of 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione needs to be controlled so as to improve the flame retardant and plasticizing properties of the sodium silicate while controlling the preparation cost.

[0020] In a further technical solution, the amount of the organic solvent is 2 to 3 times the mass of 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. If the amount of the organic solvent is too small, it will affect the mass transfer and heat transfer effect during the reaction, resulting in insufficient contact between the reaction raw materials and excessively high local temperature; if the amount of the organic solvent is too large, it will not only increase the preparation cost, but also increase the energy consumption input for recovering the organic solvent.

[0021] In a further technical solution, the vacuum drying temperature is 60-70° C. The residual toluene on the filter residue can be removed by vacuum drying.

[0022] The second object of the present invention is to provide a sodium silicate flame retardant prepared by the above-mentioned preparation method.

[0023] The beneficial effects of the present invention are as follows: the present invention uses 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione to perform surface modification on sodium silicate, which can, on the one hand, efficiently utilize the original flame retardant properties of sodium silicate, and on the other hand, can also give sodium silicate certain plasticizing properties, so that sodium silicate has the dual effects of flame retardancy and plasticization, thereby improving the market competitiveness of sodium silicate. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0025] The reaction bottles and sodium silicate in the following examples and comparative examples were oven dried before use, with the oven temperature set at 120° C. and the drying time set at 12 h; toluene and 3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione were dehydrated using activated molecular sieves before use, and the molecular sieve was activated by high-temperature calcination at a temperature of 350° C.

[0026] Example 1

[0027] Add 200g toluene and 150g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g 1,3,5-tri[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, raise the temperature to reflux, and keep the reaction at reflux for 12h. After the reaction is completed, filter the reaction liquid, dry the filter residue in vacuum at 70°C, ball mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0028] Example 2

[0029] Add 200g toluene and 180g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g 1,3,5-tri[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, raise the temperature to reflux, and keep the reaction at reflux for 12h. After the reaction is completed, filter the reaction solution, dry the residue in vacuum at 70°C, ball mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0030] Example 3

[0031] Add 200g toluene and 200g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g 1,3,5-tri[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, raise the temperature to reflux, and keep the reaction at reflux for 12h. After the reaction is completed, filter the reaction solution, dry the filter residue in vacuum at 70°C, ball mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0032] Example 4

[0033] Add 300g toluene and 180g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g 1,3,5-tri[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, raise the temperature to reflux, and keep the reaction at reflux for 5h. After the reaction is completed, filter the reaction solution, dry the residue in vacuum at 70°C, ball-mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0034] Example 5

[0035] Add 300g toluene and 180g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g 1,3,5-tri[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, raise the temperature to reflux, and keep the reaction at reflux for 8h. After the reaction is completed, filter the reaction liquid, dry the filter residue in vacuum at 70°C, ball mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0036] Comparative Example 1

[0037] The method of Example 1 is followed, except that the 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione in Example 1 is replaced by γ-aminopropyltriethoxysilane (silane coupling agent APTS).

[0038] Add 200g toluene and 150g sodium silicate to the reaction bottle. After the sodium silicate is evenly dispersed, add 100g γ-aminopropyltriethoxysilane, raise the temperature to reflux, and keep the reaction under reflux for 12h. After the reaction is completed, filter the reaction liquid, dry the filter residue in vacuum at 70°C, ball mill, and pass through an 800-mesh sieve to obtain a sodium silicate flame retardant.

[0039] The sodium silicate flame retardants obtained in Examples 1 to 5 and Comparative Example 1 were used to prepare polyvinyl chloride (PVC) composite materials, and sodium silicate without surface modification was used as a blank control. The flame retardant properties and tensile properties of the prepared PVC composite materials were tested. The test results are shown in Table 1.

[0040] Preparation method of PVC composite material: PVC resin (Xinjiang Tianye SG-3), sodium silicate flame retardant, anatase titanium dioxide, polyethylene wax and antioxidant 1010 are added to a high-speed mixer in a weight ratio of 100:15:5:1.5:1, mixed evenly, melted and plasticized in a double-roll mill at 165°C, and injection molded at 165°C and 550MPa, and made into strip specimens according to GB / T 17037.1-2019.

[0041] Test oxygen index according to GB / T 2406.2-2009;

[0042] The tensile properties are tested according to GB / T 1040.1-2018.

[0043] Table 1

[0044] Oxygen index / % Tensile strength / MPa Elongation at break / % Example 1 31.2 24.7 325 Example 2 32.8 22.3 310 Example 3 33.5 19.6 274 Example 4 30.4 20.9 287 Example 5 31.9 21.5 298 Comparative Example 1 25.2 17.0 236 Sodium silicate 26.3 15.4 212

[0045] As can be seen from Table 1, Examples 1 to 5 of the present invention use 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione to modify the surface of sodium silicate, which can not only significantly improve the mechanical properties of the PVC composite material, but also make the PVC composite material have excellent flame retardant properties. Although the use of γ-aminopropyltriethoxysilane instead of 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione can also achieve surface modification of sodium silicate, it cannot substantially improve the mechanical properties of the PVC composite material.

[0046] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a sodium silicate flame retardant, characterized in that: An organic solvent and sodium silicate are added to a reaction container, and after the sodium silicate is evenly dispersed, 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione is added, the temperature is raised to a reflux state, and the reaction is kept under reflux. After the reaction is completed, the reaction liquid is filtered, and the filter residue is vacuum dried to obtain a sodium silicate flame retardant.

2. The preparation method according to claim 1, characterized in that: The reaction container was dried before use.

3. The preparation method according to claim 1, characterized in that: The sodium silicate is dried before use.

4. The preparation method according to claim 1, characterized in that: The organic solvent is toluene.

5. The preparation method according to claim 1, characterized in that: The organic solvent and 3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione are treated to remove water before use.

6. The preparation method according to claim 1, characterized in that: The sodium silicate is dispersed by mechanical stirring, magnetic stirring or ultrasonic treatment.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the sodium silicate to 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione is (1.5-2):

1.

8. The preparation method according to claim 1, characterized in that: The amount of the organic solvent used is 2 to 3 times the mass of 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

9. The preparation method according to claim 1, characterized in that: The vacuum drying temperature is 60-70°C.

10. A sodium silicate flame retardant prepared by the preparation method according to any one of claims 1 to 9.