Preparation method of halogen-free flame-retardant latex

Abstract

The invention discloses a preparation method of halogen-free flame-retardant latex, which belongs to the technical field of latex, and comprises the following steps: S1, adding deionized water, butadiene, acrylonitrile, methacrylic acid, a compound emulsifier and tert-dodecanethiol into a polymerization kettle, uniformly stirring, then vacuumizing, replacing with nitrogen, adding an initiator, and continuing polymerization reaction; s2, adding the flame retardant and a small amount of tert-dodecanethiol again, adjusting the reaction temperature, and continuing the polymerization reaction; and S3, when the polymerization conversion rate reaches 75-80%, adding a terminator to stop the reaction, and degassing to obtain the halogen-free flame-retardant latex. The special flame retardant is doped into the latex, so that the latex can be endowed with efficient halogen-free flame retardant property, the interaction force between the flame retardant and the latex can be improved, the durability of the flame retardant effect can be improved, the mechanical strength and the waterproof property of a latex finished product can be improved to a certain extent, and the flame-retardant latex has very important application significance.

Description

Technical Field

[0001] The invention belongs to the technical field of latex, and in particular relates to a method for preparing halogen-free flame-retardant latex. Background Art

[0002] Carboxylated nitrile latex is a kind of high molecular weight white emulsion made of acrylonitrile, butadiene, methacrylic acid and other additives through emulsion polymerization. This emulsion has good film-forming properties, tensile strength and elongation at break, and is now mainly used in the production of nitrile labor protection gloves and disposable medical examination gloves without lining.

[0003] With the continuous development of the economy, the requirements of various industries for labor protection products are gradually increasing. It is necessary to have some high-strength flame-retardant carboxyl nitrile latex gloves to meet the requirements of different users. In order to improve the flame retardancy of carboxyl nitrile latex in the prior art, some flame retardants are mostly mixed into it. This method has the following technical defects: 1. It is difficult for the flame retardant to be evenly dispersed in the latex, which affects the flame retardant performance; 2. After the finished gloves are made, the flame retardant will migrate as the use time increases, affecting the durability of the flame retardant effect. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a halogen-free flame retardant latex. By adding a special flame retardant into the latex, not only can the latex be given high-efficiency halogen-free flame retardant properties, but also the interaction between the flame retardant and the latex can be improved, the durability of the flame retardant effect can be improved, and the mechanical strength and waterproof performance of the latex product can be improved to a certain extent, which has very important application significance.

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

[0006] A method for preparing a halogen-free flame retardant latex comprises the following steps:

[0007] S1. Add deionized water, butadiene, acrylonitrile, methacrylic acid, composite emulsifier and tert-dodecyl mercaptan into a polymerization kettle and stir evenly, then evacuate and replace with nitrogen, add initiator, adjust the temperature to 8-10°C, and continue the polymerization reaction for 6-8h;

[0008] S2, add flame retardant and a small amount of tert-dodecyl mercaptan again, adjust the reaction temperature to 5-6°C, and continue the polymerization reaction for 3-4h;

[0009] S3. When the polymerization conversion rate reaches 75%-80%, a terminator is added to stop the reaction, and degassing is performed to obtain a halogen-free flame retardant latex.

[0010] Furthermore, the raw materials in step S1 are calculated in parts by weight as follows: 70-80 parts of deionized water, 60-75 parts of butadiene, 25-32 parts of acrylonitrile, 4-6 parts of methacrylic acid, 6-10 parts of composite emulsifier, 1.5-2.5 parts of tert-dodecyl mercaptan, and 0.8-1.2 parts of initiator.

[0011] Furthermore, the composite emulsifier is a mixture of sodium alkylbenzene sulfonate and fatty alcohol polyoxyethylene ether, and the mass ratio of the two is 4-5:2.

[0012] Furthermore, the initiator is diisopropylbenzene hydroperoxide.

[0013] Furthermore, the amount of tert-dodecyl mercaptan added in step S2 is half of the amount of tert-dodecyl mercaptan added in step S1; and the amount of flame retardant added in step S2 is 1 / 10 of the mass of butadiene.

[0014] Furthermore, the terminator in step S3 is sodium nitrite, and the amount added is 1 / 3-1 / 2 of the mass of the initiator.

[0015] Furthermore, the flame retardant is prepared by the following steps:

[0016] A1. Add hexachlorocyclotriphosphazene and acetonitrile to a three-necked flask equipped with a condenser, then drop triethylamine into the three-necked flask, stir at room temperature for 3 hours, and after the hexachlorocyclotriphosphazene is completely dissolved, slowly add 3-(4-nitrophenyl)-1-propanol at reflux temperature, then raise the temperature to 70°C, and reflux the mixture for 8 hours. After the reaction is completed, wash away the residual solvent and impurities with DMSO, filter while hot, and distill under reduced pressure to obtain an intermediate;

[0017] The usage ratio of hexachlorocyclotriphosphazene, triethylamine and 3-(4-nitrophenyl)-1-propanol is 0.01 mol:8 g:0.08 mol;

[0018] Under the action of triethylamine, the P-Cl on the hexachlorocyclotriphosphazene molecule reacts with the -OH on 3-(4-nitrophenyl)-1-propanol. The reaction process is as follows:

[0019]

[0020] A2, the intermediate and toluene are added to a reactor, a palladium-carbon catalyst is added, the air in the reactor is evacuated under reduced pressure, and then hydrogen is introduced, and a reduction reaction is carried out under a pressure of 2 atm for 3 hours. After the reaction is completed, the reaction is filtered, and the filtrate is evaporated under reduced pressure to remove toluene to obtain a flame retardant;

[0021] The amount of palladium carbon catalyst added was 20 μg / g of the intermediate mass;

[0022] The -NO2 on the intermediate molecule is reduced to -NH2 under the action of hydrogen to obtain a flame retardant. The structural formula of the flame retardant is shown below;

[0023]

[0024] From the molecular structure point of view, the flame retardant obtained is a dendritic structure, with a PN heterocycle located in the center and branch chains located around the heterocycle. The PN heterocycle is a halogen-free PN synergistic flame retardant component with excellent flame retardant properties. The ends of the branch chains located around are -NH2 groups. The -NH2 groups have high reactivity with the -COOH groups on methacrylic acid and can act as a cross-linking agent during the latex polymerization process. It can not only enhance the interaction between the flame retardant and the latex itself and prevent precipitation and migration, but also, as a cross-linking agent, it can enhance the mechanical strength and waterproof properties of the latex after molding.

[0025] Beneficial effects of the present invention:

[0026] The invention not only can impart high-efficiency halogen-free flame retardant properties to the latex by adding a special flame retardant into the latex, but also can enhance the interaction between the flame retardant and the latex, enhance the durability of the flame retardant effect, and can enhance the mechanical strength and waterproof properties of the finished latex product to a certain extent, thus having very important application significance. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the 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.

[0028] Example 1

[0029] Preparation of flame retardant:

[0030] A1. Add 0.01 mol of hexachlorocyclotriphosphazene and 60 mL of acetonitrile to a three-necked flask equipped with a condenser, then drop 8 g of triethylamine into the three-necked flask, stir at room temperature for 3 h, and after the hexachlorocyclotriphosphazene is completely dissolved, slowly add 0.08 mol of 3-(4-nitrophenyl)-1-propanol at reflux temperature, then raise the temperature to 70° C., reflux the mixture for 8 h, and after the reaction is completed, wash away the residual solvent and impurities with DMSO, filter while hot, and distill under reduced pressure to obtain an intermediate;

[0031] A2. Add 30 g of the intermediate and 80 mL of toluene into a reactor, add 600 μg of palladium-carbon catalyst, evacuate the air in the reactor under reduced pressure, then introduce hydrogen, and carry out reduction reaction at a pressure of 2 atm for 3 hours. After the reaction is completed, filter, and remove toluene from the filtrate by rotary evaporation under reduced pressure to obtain a flame retardant.

[0032] Example 2

[0033] A method for preparing a halogen-free flame retardant latex comprises the following steps:

[0034] S1. Add 70g of deionized water, 60g of butadiene, 25g of acrylonitrile, 4g of methacrylic acid, 6g of composite emulsifier (a mixture of 4g of sodium alkylbenzene sulfonate and 2g of fatty alcohol polyoxyethylene ether), and 1.55g of tert-dodecyl mercaptan into a polymerization kettle and stir evenly. Then evacuate and replace with nitrogen. Add 0.8g of diisopropylbenzene hydroperoxide, adjust the temperature to 8-10°C, and continue the polymerization reaction for 6h.

[0035] S2, adding 6 g of the flame retardant prepared in Example 1 and 0.75 g of tert-dodecyl mercaptan again, adjusting the reaction temperature to 5-6° C., and continuing the polymerization reaction for 3 h;

[0036] S3. When the polymerization conversion rate reaches 75%-80%, 0.27g of sodium nitrite is added to stop the reaction, and degassing is performed to obtain a halogen-free flame retardant latex.

[0037] Example 3

[0038] A method for preparing a halogen-free flame retardant latex comprises the following steps:

[0039] S1. Add 75g of deionized water, 70g of butadiene, 29g of acrylonitrile, 5g of methacrylic acid, 8g of composite emulsifier (a mixture of 5.7g of sodium alkylbenzene sulfonate and 2.3g of fatty alcohol polyoxyethylene ether), and 2g of tert-dodecyl mercaptan into a polymerization kettle, stir evenly, then evacuate and replace with nitrogen, add 1g of diisopropylbenzene hydroperoxide, adjust the temperature to 8-10°C, and continue the polymerization reaction for 7h;

[0040] S2, adding 7g of the flame retardant prepared in Example 1 and 1g of tert-dodecyl mercaptan again, adjusting the reaction temperature to 5-6°C, and continuing the polymerization reaction for 3.5h;

[0041] S3. When the polymerization conversion rate reaches 75%-80%, 0.4 g of sodium nitrite is added to stop the reaction, and degassing is performed to obtain a halogen-free flame retardant latex.

[0042] Example 4

[0043] A method for preparing a halogen-free flame retardant latex comprises the following steps:

[0044] S1. Add 80g of deionized water, 75g of butadiene, 32g of acrylonitrile, 6g of methacrylic acid, 10g of a composite emulsifier (a mixture of 6.6g of sodium alkylbenzene sulfonate and 3.4g of fatty alcohol polyoxyethylene ether), and 2.5g of tert-dodecyl mercaptan into a polymerization kettle, stir evenly, then evacuate and replace with nitrogen, add 1.2g of diisopropylbenzene hydroperoxide, adjust the temperature to 8-10°C, and continue the polymerization reaction for 8h;

[0045] S2, adding 7.5 g of the flame retardant prepared in Example 1 and 1.25 g of tert-dodecyl mercaptan again, adjusting the reaction temperature to 5-6° C., and continuing the polymerization reaction for 4 h;

[0046] S3. When the polymerization conversion rate reaches 75%-80%, 0.6g of sodium nitrite is added to stop the reaction, and degassing is performed to obtain a halogen-free flame retardant latex.

[0047] Comparative Example 1

[0048] The latex is obtained by replacing the flame retardant in Example 2 with an equal amount of hexachlorocyclotriphosphazene and keeping the other raw materials and the preparation process unchanged.

[0049] The latex in Examples 2 to 4 and Comparative Example 1 were respectively prepared into unlined thin gloves with a thickness of 0.15 mm, and the performance of the gloves was tested in accordance with GB 10213-2006 "Disposable Medical Rubber Examination Gloves";

[0050] Cut the gloves into appropriate sizes and perform tensile properties test according to GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0051] Cut the gloves into standard samples, pick up the sample with tweezers and move it over the flame to make it burn, then move the burning sample out of the flame, and record the self-extinguishing time after the sample is moved out of the flame to test its flame retardancy;

[0052] The measured results are shown in the following table:

[0053]

[0054]

[0055] From the above test results, it can be seen that the addition of flame retardants in this application can not only give the latex excellent flame retardant properties, but also improve its flame retardant durability and enhance the mechanical properties of the molded gloves.

[0056] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a halogen-free flame retardant latex, characterized in that: The following steps are involved: S1. Add deionized water, butadiene, acrylonitrile, methacrylic acid, composite emulsifier and tert-dodecyl mercaptan into a polymerization kettle and stir evenly, then evacuate and replace with nitrogen, add initiator, adjust the temperature to 8-10°C, and continue the polymerization reaction for 6-8h; S2, add flame retardant and a small amount of tert-dodecyl mercaptan again, adjust the reaction temperature to 5-6°C, and continue the polymerization reaction for 3-4h; S3. When the polymerization conversion rate reaches 75%-80%, a terminator is added to stop the reaction, and degassing is performed to obtain a halogen-free flame retardant latex.

2. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The raw materials in step S1 are calculated in parts by weight as follows: 70-80 parts of deionized water, 60-75 parts of butadiene, 25-32 parts of acrylonitrile, 4-6 parts of methacrylic acid, 6-10 parts of composite emulsifier, 1.5-2.5 parts of tert-dodecyl mercaptan, and 0.8-1.2 parts of initiator.

3. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The composite emulsifier is a mixture of sodium alkylbenzene sulfonate and fatty alcohol polyoxyethylene ether, and the mass ratio of the two is 4-5:

2.

4. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The initiator is diisopropylbenzene hydroperoxide.

5. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The amount of tert-dodecyl mercaptan added in step S2 is half of the amount of tert-dodecyl mercaptan added in step S1.

6. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The amount of flame retardant added in step S2 is 1 / 10 of the mass of butadiene.

7. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The terminator in step S3 is sodium nitrite, and the amount added is 1 / 3-1 / 2 of the mass of the initiator.

8. The method for preparing a halogen-free flame retardant latex according to claim 1, characterized in that: The flame retardant is prepared by the following steps: A1. Add hexachlorocyclotriphosphazene and acetonitrile to a three-necked flask equipped with a condenser, then drop triethylamine into the three-necked flask, stir at room temperature for 3 hours, and after the hexachlorocyclotriphosphazene is completely dissolved, slowly add 3-(4-nitrophenyl)-1-propanol at reflux temperature, then raise the temperature to 70°C, and reflux the mixture for 8 hours. After the reaction is completed, wash away the residual solvent and impurities with DMSO, filter while hot, and distill under reduced pressure to obtain an intermediate; A2. Add the intermediate and toluene into a reactor, add a palladium-carbon catalyst, evacuate the air in the reactor under reduced pressure, then introduce hydrogen, and carry out a reduction reaction at a pressure of 2 atm for 3 hours. After the reaction is completed, filter, and evaporate the filtrate under reduced pressure to remove toluene to obtain a flame retardant.

9. The method for preparing a halogen-free flame retardant latex according to claim 8, characterized in that: In step A1, the usage ratio of hexachlorocyclotriphosphazene, triethylamine and 3-(4-nitrophenyl)-1-propanol is 0.01 mol:8 g:0.08 mol.

10. The method for preparing a halogen-free flame retardant latex according to claim 8, characterized in that: The amount of palladium carbon catalyst added in step A2 is 20 μg / g of the intermediate mass.

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