Preparation method and application of multi-sulfur polymer

Abstract

The invention provides a preparation method and application of a multi-sulfur polymer. The preparation method comprises the following steps: mixing a dichloro intermediate and a sodium polysulfide aqueous solution, and carrying out condensation polymerization in a formed mixed system to prepare a polysulfide polymer; an organic solvent exists in the mixed system, and the organic solvent is selected from C6-C9 aromatic hydrocarbons. According to the preparation method disclosed by the invention, salt after condensation polymerization can be quickly and efficiently separated, so that the quality of liquid polysulfide rubber obtained during cracking of the polysulfide polymer is improved, and the production efficiency of a production device is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer preparation technology, and relates to a method for preparing polysulfide polymers and their applications. Background Technology

[0002] Liquid polysulfide rubber is widely used in aircraft oil-phase sealants, rocket propellant adhesives, construction, automobiles, railways, insulating glass, and shipbuilding due to its ease of application and excellent oil resistance, ozone resistance, and low-temperature performance after vulcanization and curing.

[0003] The production method of liquid polysulfide rubber is as follows: sodium polysulfide aqueous solution and dichloro intermediate undergo condensation reaction in an aqueous phase with dispersant to obtain polysulfide polymer emulsion. The emulsion is washed with water 3-4 times to remove excess inorganic salts such as sodium polysulfide until the washed latex is neutral. The washed polysulfide polymer is then reacted with sodium hydrosulfide and sodium sulfite to obtain pyrolysis products. The pyrolysis products are then acidified to obtain liquid polysulfide rubber.

[0004] The emulsion obtained from the polycondensation reaction needs to be washed to remove unreacted sodium polysulfide and other inorganic salts before proceeding to the next reaction. Because the emulsion contains emulsifiers and the polysulfide polymer particles are small (approximately 50 μm), water and latex separation is difficult after adding washing water, and the separated aqueous phase is on the upper layer. Therefore, it is necessary to extend the standing time. Even after standing for 12 hours, the water content in the lower latex layer still exceeds 65 wt%. Furthermore, the presence of water on the upper layer increases the operational difficulty during production. Existing technologies disclose the addition of flocculants to the emulsion, but this still suffers from the disadvantage of a long separation time. It also increases the risk of polysulfide polymer agglomeration in the emulsion, making the cracking reaction difficult. Additionally, the presence of flocculants in the product can result in insoluble matter suspended in the final liquid polysulfide rubber product, affecting product quality. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for preparing polysulfide polymers. This method can achieve rapid and efficient separation of salts after polycondensation reaction, thereby improving the quality of liquid polysulfide rubber obtained during the pyrolysis of the polysulfide polymer and greatly improving the production efficiency of the production equipment.

[0006] Specifically, the technical solution of the present invention is as follows:

[0007] A method for preparing a polysulfide polymer, the method comprising: mixing a dichloro intermediate and an aqueous solution of sodium polysulfide, and carrying out a polycondensation reaction in the formed mixture to prepare the polysulfide polymer; wherein the mixture contains an organic solvent selected from C6-C9 aromatic hydrocarbons.

[0008] According to an embodiment of the present invention, after the polycondensation reaction is completed, the mixture is allowed to stand and separate into an oil phase and an aqueous phase, wherein the oil phase includes the polysulfide polymer. Specifically, after the polycondensation reaction is completed, the mixture is allowed to stand and separate into two phases: the upper layer is an oil phase containing the polysulfide polymer, and the lower layer is an aqueous phase containing inorganic salts.

[0009] According to an embodiment of the present invention, the preparation method further includes: collecting the oil phase to obtain an organic solution of the polysulfide polymer.

[0010] Preferably, the organic solution of the polysulfide polymer can be further washed with water to obtain an organic solution of the polysulfide polymer that does not contain inorganic salts.

[0011] According to an embodiment of the present invention, the aqueous phase contains inorganic salts at a concentration of 20-40% wt. Further, the inorganic salts include unreacted sodium polysulfide and byproduct sodium chloride, etc.

[0012] According to an embodiment of the present invention, the dichloro intermediate has the structure Cl-R-Cl, where R is selected from alkylene (e.g., C1-C5 alkylene) and -R 11 -OR 12 - or -R 2 -OR 3 -OR 2 -;

[0013] Among them, R 11 and R 12 They may be the same or different, and are independently selected from C1-C5 alkylene groups (e.g., methylene, ethylene, propylene);

[0014] R 2 and R 3 They may be the same or different, and are independently selected from C1-C5 alkylene groups (e.g., methylene, ethylene).

[0015] For example, the dichloro intermediate is dichloroethyl formaldehyde, also known as bis(2-chloroethoxy)methane. Specifically, the dichloroethyl formaldehyde can be prepared from chloroethanol and paraformaldehyde according to known methods.

[0016] According to an embodiment of the present invention, the organic solvent is selected from at least one or a mixture of two or more of benzene, toluene, xylene, ethylbenzene, trimethylbenzene, etc.

[0017] According to an embodiment of the present invention, in the mixed system, the volume ratio of the organic solvent to the sodium polysulfide aqueous solution is 1-2:1, for example, 1:1, 1.5:1, etc.

[0018] According to an embodiment of the present invention, the sodium polysulfide aqueous solution comprises sodium polysulfide and water, wherein the mass fraction of sodium polysulfide is 1-50 wt%, for example, 10 wt%, 20 wt%, 30 wt%, or 40 wt%.

[0019] According to an embodiment of the present invention, the sodium polysulfide is prepared by reacting sodium sulfide and sulfur using a known method.

[0020] According to an embodiment of the present invention, the sulfur index of the sodium polysulfide is 1-5, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, or 5.0. The inventors have discovered that when the sulfur index of the sodium polysulfide meets the requirements of the present invention, the weight-average molecular weight of the polysulfide polymer obtained by the preparation method of the present invention can be controlled. For example, when the sulfur index of the sodium polysulfide is the same, the weight-average molecular weight of the polysulfide polymer obtained by the polycondensation reaction is also substantially the same.

[0021] According to an embodiment of the present invention, during the polycondensation reaction, a dispersant and / or a crosslinking agent may optionally be added to the reaction system.

[0022] Preferably, the dispersant is selected from at least one of sulfonate anionic surfactants, potassium (disproportionated) rosinate, and tetraalkyl ammonium halides. Further, the sulfonate anionic surfactant is selected from at least one of alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, alkyl succinate sulfonates, alkyl diphenyl ether sulfonates, and naphthalene sulfonic acid formaldehyde condensates; for example, at least one of sodium dibutylnaphthalene sulfonate, sodium butylnaphthalene sulfonate, and sodium diisopropylnaphthalene sulfonate. Further, the tetraalkyl ammonium halide is, for example, tetramethylammonium bromide.

[0023] Preferably, the crosslinking agent is selected from one or a mixture of two or more of 1,1,1-trichloropropane, 1,2,3-trichloropropane, 1,2,3-tribromopropane, 1,3-dichloro-2-(chloromethyl)-2-methylpropane, tetrabromoethane, etc.

[0024] According to an embodiment of the present invention, during the polycondensation reaction, other auxiliaries may be added to the reaction system, such as alkalis and / or dispersing agents. Preferably, the alkali is selected from inorganic alkalis, such as at least one selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate, etc. Preferably, the dispersing agent is selected from water-soluble magnesium salts, and the water-soluble magnesium salt is selected from water-soluble magnesium salts known in the art, such as at least one selected from magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, etc.

[0025] According to an embodiment of the present invention, when the crosslinking agent is added, the molar ratio of the dichloro intermediate (the dichloro intermediate has the definition described above, for example, dichloroethyl formaldehyde) to the crosslinking agent is 1:0.01 to 0.4, for example, 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.2, 1:0.3 or 1:0.4.

[0026] According to an embodiment of the present invention, the molar ratio of the sodium polysulfide to the dichloro intermediate (the dichloro intermediate has the definition described above, for example, dichloroethyl formaldehyde) is 1-1.4:1, for example, 1.1:1, 1.2:1, 1.3:1 or 1.4:1.

[0027] According to an embodiment of the present invention, the temperature of the polycondensation reaction is 60-120°C, for example, 60, 70, 80, 90, 100, 105, 110, 115 or 120°C.

[0028] According to an embodiment of the present invention, the polycondensation reaction takes 2-6 hours, for example, 3 hours. Preferably, the polycondensation reaction time refers to the reaction time after mixing is completed.

[0029] According to an embodiment of the present invention, in the preparation method, during the polycondensation reaction, the dichloro intermediate is added dropwise to an aqueous solution of sodium polysulfide in the presence of an organic solvent. Specifically, this means: dissolving the dichloro intermediate in an organic solvent to form an organic solution of the dichloro intermediate, and then adding (e.g., dropwise) the organic solution of the dichloro intermediate to the aqueous solution of sodium polysulfide; or, first forming a mixture of the aqueous solution of sodium polysulfide and the organic solvent, and then adding (e.g., dropwise) the dichloro intermediate to the mixture.

[0030] According to an embodiment of the present invention, since the reaction between the dichloro intermediate and sodium polysulfide is highly exothermic, it is necessary to control the reaction rate between the dichloro intermediate and sodium polysulfide. For example, the dichloro intermediate or an organic solution of the dichloro intermediate is added dropwise (e.g., at a dropping rate of 0.001-0.015 mol / min) to the sodium polysulfide aqueous solution to maintain the above-mentioned reaction temperature. Exemplarily, the dichloro intermediate is dichloroethyl formaldehyde, and its dropping rate is 0.001-0.015 mol / min, for example, 0.001 mol / min, 0.005 mol / min, or 0.01499 mol / min.

[0031] According to an embodiment of the present invention, the pH of the organic solution of the polysulfide polymer obtained by the above preparation method of the present invention is not greater than 8.5, for example, 8.

[0032] According to an embodiment of the present invention, the solid content in the organic solution of the polysulfide polymer obtained by the above preparation method of the present invention is not greater than 30 wt%, for example, 25 wt%, 20 wt%, 16.7 wt%, or 10 wt%.

[0033] According to an embodiment of the present invention, the polysulfide polymer obtained by the above preparation method of the present invention has a weight-average molecular weight of 20,000-100,000, for example 58,500.

[0034] According to an embodiment of the present invention, the inorganic substances such as unreacted sodium polysulfide and by-product sodium chloride remaining in the aqueous phase obtained by the preparation method can be used as raw materials for preparing aqueous solutions of polysulfides. Sodium polysulfide aqueous solutions can be prepared by adding sodium sulfide and sulfur in a stoichiometric ratio known in the art, or sodium chloride can be recovered through wastewater treatment.

[0035] The present invention also provides a polysulfide polymer, which is obtained by the above preparation method.

[0036] According to an embodiment of the present invention, the weight-average molecular weight of the polysulfide polymer is 20,000-100,000, for example, 58,500.

[0037] According to an embodiment of the present invention, the pH of the organic solution of the polysulfide polymer is not greater than 8.5, for example, 8.

[0038] According to an embodiment of the present invention, the solid content in the organic solution of the polysulfide polymer is not greater than 30 wt%, for example, 25 wt%, 20 wt%, 16.7 wt%, or 10 wt%.

[0039] The present invention also provides the application of the above-mentioned polysulfide polymer in the preparation of liquid polysulfide rubber.

[0040] Beneficial effects

[0041] This invention provides a method for preparing a polysulfide polymer, which involves polycondensing a dichloro intermediate and an aqueous solution of sodium polysulfide in an organic solvent to obtain the polysulfide polymer. The polysulfide polymer obtained by the polycondensation reaction is directly dissolved in the organic solvent. After the reaction is completed, the phases are separated, wherein the oil phase contains the polysulfide polymer, while the inorganic salts are aggregated in the aqueous phase. This method enables rapid and efficient separation of the salts after the polycondensation reaction, thereby improving the quality of the liquid polysulfide rubber obtained during the pyrolysis of the polysulfide polymer and greatly improving the production efficiency of the production equipment.

[0042] Compared with the known emulsion polymerization process for preparing polysulfide polymers, the present invention simplifies the preparation steps, shortens the production time, improves the utilization rate of production equipment, and greatly reduces the output of industrial wastewater. Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0044] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0045] Example 1

[0046] (1) Preparation of 20wt% sodium polysulfide aqueous solution: It is prepared by reacting sodium sulfide and sulfur in an aqueous phase in an equimolar ratio according to a known method, with a sulfur index of 2.0.

[0047] (2) Preparation of dichloroethyl formaldehyde, chemical name bis(2-chloroethoxy)methane, prepared by chloroethanol and paraformaldehyde according to known methods, and the content of dichloroethyl formaldehyde obtained by gas chromatography analysis is 99.0%.

[0048] (3) The preparation method of polysulfide polymers is as follows:

[0049] Add 1010g of sodium polysulfide aqueous solution (sodium polysulfide content 20wt%, sodium polysulfide 1.836mol) and 0.6g of separating powder (sodium dibutylnaphthalenesulfonate, 0.002mol) to a 3L glass reaction flask, stir, and heat to 90℃.

[0050] A mixture containing 260.2 g of dichloroethyl formaldehyde (1.499 mol), 1500 ml of toluene, and 4.4 g of 1,1,1-trichloropropane (0.03 mol) was added dropwise to the above-mentioned sodium polysulfide aqueous solution under stirring. The reaction temperature was maintained at 90°C, and the addition was completed in about 100 minutes. Stirring was continued at 90°C to carry out the polycondensation reaction. Gas chromatography was used for monitoring and analysis. After about 3 hours, the dichloroethyl formaldehyde reaction was complete, yielding the polysulfide polymer. Stirring was stopped, and the reaction solution was allowed to stand for 0.5 hours to separate into layers, resulting in a light yellow oil phase on top and a brownish-red aqueous phase on the bottom. 1570 g of the light yellow oil phase was separated, which was the organic solution of the polysulfide polymer, with a solid content of 16.7 wt%. The polysulfide polymer was concentrated in the oil phase, and the pH of the oil phase was 8.0. 1006 g of the aqueous phase was separated, which contained the byproduct sodium chloride, and was reserved for later use.

[0051] The weight-average molecular weight of the polysulfide polymer obtained in this embodiment was found to be 58,500.

[0052] Since the emulsion of the polysulfide polymer prepared in this embodiment has a pH of 8.0, it can be directly contacted with an aqueous solution of a pyrolysis agent (such as sodium bisulfite) and pyrolyzed and acidified according to methods known in the art to prepare liquid polysulfide rubber.

[0053] Example 2

[0054] (1) Take 1006g of the aqueous phase obtained by standing and separating in Example 1 as raw material, add sodium sulfide and sulfur to it, and prepare sodium polysulfide aqueous solution according to step (1) of Example 1. Filter to obtain sodium polysulfide aqueous solution with sulfur index of 2.0.

[0055] (3) The preparation method of the polysulfide polymer in this embodiment is the same as that in Example 1, except that: the sodium polysulfide aqueous solution in this embodiment is used as the raw material, and the other steps are the same as those in Example 1 (3). The polycondensation reaction time is 3.3 hours (i.e., gas chromatography monitoring shows that after 3.3 hours of reaction, the dichloro intermediate is completely reacted).

[0056] The polysulfide polymer was obtained. Stirring was stopped, and the reaction solution was allowed to stand for 0.5 hours to separate into layers. The upper layer was a light yellow oil phase, and the lower layer was a brownish-red aqueous phase. 1575g of the upper light yellow oil phase was separated, which was the organic solution of the polysulfide polymer. The solid content was 16.6wt%, and the polysulfide polymer was concentrated in the oil phase. The pH of the oil phase was 8.2, which was basically the same as in Example 1.

[0057] The weight-average molecular weight of the polysulfide polymer obtained in this embodiment was found to be 51080, which is basically the same as that of the polysulfide polymer in Example 1.

[0058] Comparative Example 1

[0059] Conventional industrial preparation methods:

[0060] The preparation of the aqueous solution of sodium polysulfide and dichloroethyl formaldehyde is the same as in Example 1.

[0061] The preparation method of polysulfide polymer is as follows: Add 1010g of sodium polysulfide solution (20wt%, 1.836mol), 14.3g of sodium hydroxide (0.350mol), and 0.6g of separating powder (0.002mol) to a 3L glass reaction flask and stir. Heat to 60℃. Add 170g (0.175mol) of 10% magnesium chloride aqueous solution dropwise over approximately 20 minutes. A brownish-red sodium polysulfide solution with magnesium hydroxide suspended in the solution is obtained in the reaction flask. Then heat to 90℃.

[0062] A mixture of 260.2 g of dichloroethyl formaldehyde (1.499 mol) and 4.4 g of 1,1,1-trichloropropane (0.03 mol) was added dropwise to the above-mentioned sodium polysulfide solution containing suspended magnesium hydroxide while stirring. The reaction temperature was maintained at 90 °C, and the addition was completed in about 100 minutes. Stirring was continued at 90 °C, and gas chromatography was used for monitoring and analysis. After about 2.5 hours, the reaction of dichloroethyl formaldehyde was complete. Stirring was stopped, yielding 606.5 g of a light yellow aqueous emulsion.

[0063] Add 600 ml of pure water to the above yellowish-brown aqueous emulsion, stir for 5 minutes, and allow it to stand for separation. After about 8 hours, phase separation basically stopped, yielding a lower yellowish-brown aqueous emulsion and an upper brownish-red aqueous phase. 744 g of the lower aqueous emulsion was obtained, with a solid content of 35 wt% and a pH of 13.

[0064] The lower water emulsion was washed three times, each time with 600 ml of water. After stirring and standing, the water emulsion was separated into layers. The stirring time for each wash was 5 minutes and the standing time was 8 hours. The pH of the emulsion layers after the three washes were 11, 9.5 and 8.0, respectively. Finally, 740 g of polysulfide polymer emulsion was obtained, with a solid content of 35.2 wt% and a weight average molecular weight of 75,000 for the polysulfide polymer.

[0065] In Comparative Example 1, the upper brownish-red aqueous phase was obtained by washing the aqueous emulsion and then separating the phases. Since the lower layer is an aqueous emulsion, it contains at least 60% water, and therefore also contains a significant amount of unreacted sodium polysulfide and sodium chloride, a byproduct of the reaction. The concentrations of unreacted sodium polysulfide and sodium chloride in the upper aqueous phase are much lower than those in the aqueous phase of Example 1, making it unsuitable for reuse as a raw material for preparing sodium polysulfide solution. Furthermore, to thoroughly wash away the inorganic matter in the lower aqueous emulsion, multiple and large-volume washings are required, which also generates a large amount of low-concentration inorganic salt industrial wastewater.

[0066] As can be seen from Example 1 and Comparative Example 1, in order to obtain polysulfide polymer reactants with the same pH, the preparation method of the present invention takes a total of 4 hours to prepare polysulfide polymers; while the conventional industrial method of Comparative Example 1 requires at least 32 hours for post-processing after the polycondensation reaction alone (such as the time for settling and washing). Moreover, because the polysulfide polymer product in Comparative Example 1 needs to be washed repeatedly until pH=8, approximately 2262 ml of additional industrial wastewater is generated.

[0067] Therefore, when using the preparation method of this application to prepare polysulfide polymers, not only can the process operation time be greatly saved, but the amount of industrial wastewater generated can also be reduced.

[0068] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polysulfide polymer, characterized in that, The preparation method includes: mixing a dichloro intermediate and an aqueous solution of sodium polysulfide, and carrying out a polycondensation reaction in the formed mixed system to prepare a polysulfide polymer; characterized in that the mixed system contains an organic solvent, wherein the organic solvent is selected from C6-C9 aromatic hydrocarbons.

2. The preparation method according to claim 1, characterized in that, After the polycondensation reaction is completed, the mixture is allowed to stand and separate into an oil phase and an aqueous phase, the oil phase containing the polysulfide polymer. Preferably, after the polycondensation reaction is completed, the mixture is allowed to stand and separate into two phases: the upper phase is an oil phase containing polysulfide polymers, and the lower phase is an aqueous phase containing inorganic salts. Preferably, the preparation method further includes: collecting the oil phase to obtain an organic solution of the polysulfide polymer.

3. The preparation method according to claim 1 or 2, characterized in that, The dichloro intermediate has the structure Cl-R-Cl, where R is selected from alkylene groups or -R... 11 -OR 12 - or -R 2 -OR 3 -OR 2 -; Among them, R 11 and R 12 They may be the same or different, and are independently selected from C1-C5 alkylene groups; R 2 and R 3 They may be the same or different, and are independently selected from C1-C5 alkylene groups.

4. The preparation method according to any one of claims 1-3, characterized in that, In the mixed system, the volume ratio of the organic solvent to the sodium polysulfide aqueous solution is 1-2:

1.

5. The preparation method according to any one of claims 1-4, characterized in that, The sodium polysulfide aqueous solution comprises sodium polysulfide and water, wherein the mass fraction of sodium polysulfide is 1-50 wt%. Preferably, the sodium polysulfide has a sulfur index of 1-5. Preferably, the molar ratio of sodium polysulfide to dichloride intermediate is 1-1.4:

1.

6. The preparation method according to any one of claims 1-5, characterized in that, The temperature of the polycondensation reaction is 60-120℃. Preferably, the polycondensation reaction takes 2-6 hours. Preferably, in the preparation method, during the polycondensation reaction, the dichloro intermediate is added dropwise to an aqueous solution of sodium polysulfide in the presence of an organic solvent.

7. A polysulfide polymer, characterized in that, The polysulfide polymer is obtained by the preparation method according to any one of claims 1-6.

8. The polysulfide polymer according to claim 7, characterized in that, The weight-average molecular weight of the polysulfide polymer is 20,000-100,000.

9. The polysulfide polymer according to claim 7 or 8, characterized in that, The pH of the organic solution of the polysulfide polymer is not greater than 8.

5. Preferably, the solid content in the organic solution of the polysulfide polymer is no more than 30 wt%.

10. The use of the polysulfide polymer according to any one of claims 7-9 in the preparation of liquid polysulfide rubber.