A method for mass production of polythiol and polythiol prepared therefrom

Abstract

This application provides a method for mass-producing polythiols. This method uses carbon dioxide instead of the highly toxic and dangerous H2S gas commonly used in the prior art, making the production process safer and more environmentally friendly. By optimizing the type of reaction catalyst, the content of the reactants, and the process, the reaction efficiency, product purity, and the thiol content of the polythiols are further improved. Furthermore, by optimizing different types of stabilizers and their content, the stability of the polythiols is enhanced. This method offers a stable production process, controllable process, minimal side reactions, high production efficiency, and low cost, and can be used for the stabilized and large-scale production of polythiols.

Description

Technical Field

[0001] The present invention relates to the field of C08G65 / 00, and in particular to a method for mass-producing polythiol and polythiol prepared therefrom. Background Art

[0002] Polymer capillaries have two or more -SH end groups, which form thiol ions under the promotion of tertiary amines, exhibiting excellent rapid curing properties and have become a commonly used low-temperature, rapid curing agent for epoxy resins. However, the methods for preparing polymer capillaries in the prior art mainly include the sodium hydrosulfide nucleophilic method (polyether-type polymer capillaries), esterification reaction (polyester-type polymer capillaries), thiourea method, unsaturated double bond addition method, etc. Among them, polyester-type polymer capillaries prepared by esterification reaction are unstable and easily react with accelerators when used as curing agents, resulting in structural changes and failure. The thiourea method and unsaturated double bond addition method require the selection of suitable initiators and initiation methods, resulting in unstable process control and high costs, making it impossible to mass-produce polymer capillaries. The sodium hydrosulfide nucleophilic method is the most common and industrially produced method, but it has obvious drawbacks: 1. Side reactions are difficult to control, resulting in a decrease in the active -SH content in the polymer capillaries product; 2. The use of highly toxic and explosive H2S gas can easily cause safety accidents; 3. The reaction process is sensitive to oxides and alkaline conditions, causing corrosion to equipment and requiring strict requirements on the material of the reactor.

[0003] Chinese patent CN109180926A discloses a method for preparing a polyether-type polythiol compound. The technical solution involves reacting a polyether polyol with epichlorohydrin to produce a chlorinated polyether, followed by preparing the polyether-type polythiol under the catalysis of a phase transfer catalyst and H2S gas. However, the technical solution still fails to avoid the use of hazardous H2S gas, and the -SH content in the prepared product is also relatively low. Chinese patent CN109880075B discloses a method for preparing a high-thiol polythiol curing agent. The method increases the amount of H2S in the reaction system to control the occurrence of process side reactions, and further improves production efficiency by optimizing the catalyst and reaction time. Although the thiol content in the product is increased, the polythiol is unstable during storage and is prone to internal crosslinking or deterioration.

[0004] Therefore, it is of practical significance to develop a production method for polythiols that is safe, environmentally friendly, and can achieve stable and large-scale production with high product stability. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention conducts research from three technical aspects: raw material optimization, process control, and product modification research. The present invention first provides a method for mass production of polythiol, comprising the following steps:

[0006] S1. Under the action of catalyst A, a polyol is reacted with a halide of propylene oxide to prepare a halide;

[0007] S2, under the action of catalyst B, reacting the halide in S1, sodium hydrosulfide solution and a certain amount of reaction gas to obtain a primary product of polythiol;

[0008] S3. Extraction and acidification treatment are performed to remove residual sodium hydrosulfide in the initial polythiol product. The pH of the system is adjusted to 4-6, and then a stabilizer is added and mixed. The system is then evaporated and concentrated to obtain the finished product.

[0009] Furthermore, in step S1, the polyol may be selected from at least one of saturated aliphatic hydrocarbon polyols or polyether polyols; preferably, polyether polyols.

[0010] Furthermore, the hydroxyl value of the polyether polyol is 300-700 mg KOH / g.

[0011] In a preferred embodiment, the polyether polyol has a hydroxyl value of 350-450 mg KOH / g.

[0012] Furthermore, the halogenated epoxypropane is selected from epichlorohydrin and / or epibromohydrin.

[0013] Furthermore, the molar ratio of the polyol to the halogenated propylene oxide is (1-10):1; preferably (2-8):1.

[0014] Furthermore, the catalyst A is selected from one or more of potassium hydroxide, DMC bimetallic catalyst, tetrabutylammonium bromide, boron trifluoride, boron trifluoride ethyl etherate, boron trifluoride ethyl etherate complex, tin tetrachloride, titanium tetrachloride, zinc chloride, and zinc perchlorate.

[0015] In a preferred embodiment, when the catalyst A is boron trifluoride ethyl ether, the reaction efficiency is better and the -SH content in the prepared polythiol is also higher, because boron trifluoride ethyl ether has higher selectivity for epoxy bonds and can effectively open the epoxy group and react it with the polyol; however, the present invention has found in research that after the addition of boron trifluoride ethyl ether, the viscosity of the system increases significantly, and when the content is too high, gelation may even occur.

[0016] Furthermore, when the catalyst A is boron trifluoride ethyl ether, the mass ratio of boron trifluoride ethyl ether to polyether polyol is 1:(80-200); preferably 1:(80-150), which can effectively improve the reaction yield and the -SH content of the product.

[0017] Furthermore, in step S1, the reaction temperature is 100-120° C., the reaction time is 4-8 h, and the stirring speed is 200-600 rpm.

[0018] Furthermore, the concentration of the sodium hydrosulfide solution in step S2 is 15-45 wt.%, preferably 25-45 wt.%.

[0019] Furthermore, the molar ratio of sodium hydrosulfide to halogenated propylene oxide in the sodium hydrosulfide solution is (1-5):1; preferably (2.7-4.5):1.

[0020] Furthermore, the amount of the catalyst B is 0.2-15 wt.% of the halide; preferably 0.5-10 wt.%.

[0021] Furthermore, the catalyst B is an amine catalyst, preferably any one or more selected from pentamethyldiethylenetriamine, DMP-30, bis(2-dimethylaminoethyl) ether, and tributylamine.

[0022] Preferably, the catalyst B is pentamethyldiethylenetriamine.

[0023] Furthermore, the reaction gas is carbon dioxide; the present application unexpectedly discovered that when the reaction gas is carbon dioxide, it reacts with sodium hydrosulfide under specific conditions to generate a quantitative amount of hydrogen sulfide in the reactor, which has the equivalent effect of inhibiting side reactions, can achieve equivalent environmentally friendly replacement of raw materials, and improve the safety and environmental friendliness of the production process.

[0024] Furthermore, the source of the carbon dioxide includes but is not limited to pure carbon dioxide gas, industrial waste gas containing carbon dioxide, etc., or a mixture of several of them.

[0025] Furthermore, in step S2, carbon dioxide gas is introduced to the reaction system to a pressure of 0.3-5 MPa, preferably 0.3-2 MPa. Increasing the amount of carbon dioxide introduced can effectively suppress the occurrence of side reactions and increase the -SH content in the product. However, after reaching a certain level, the increase in -SH becomes less obvious when the amount of carbon dioxide is increased. In addition, as the ambient pressure increases, the reaction conditions become more stringent.

[0026] Furthermore, in step S2, the reaction temperature is 90-120° C., the reaction time is 4-8 h, and the stirring speed is 200-600 rpm.

[0027] Furthermore, in step S3, the extracting liquid is a mixed solution of an organic solvent and water, and the amount of the solution is 1-2.5 times the mass of the initial polythiol product.

[0028] Furthermore, the organic solvent in the mixed solution is selected from one or a combination of n-butanol, propanol, glycerol, ethyl acetate, cyclopentane, and acetone; the mass ratio of the organic solvent to water is (0.5-3):1; preferably (0.5-1.5):1.

[0029] The present application has found that the viscosity of the prepared polythiol product increases after long-term storage. In particular, in actual use, in order to achieve a rapid curing effect, the product is combined with an amine accelerator and the viscosity of the mixed system increases significantly after storage. The inventors speculate that the reason is that thiols are prone to generate free radicals in the presence of amine substances. Oxygen in the environment will combine with the free radicals to form peroxides, which further exacerbate the generation of such free radicals. The accumulated RS· forms disulfide bonds, causing continuous chain growth, thereby continuously increasing the viscosity of the system, slowing the curing rate, and even causing excessive cross-linking to form a crust, resulting in a slower reaction time and a decrease in the thiol content in the product. Therefore, while controlling the amount of amine catalyst in S2, it is necessary to construct a further preventive plan for the system to improve the storage stability of the product.

[0030] Furthermore, the stabilizer is selected from one or a combination of thiodipropionates, phosphites, and hindered phenols.

[0031] Furthermore, the stabilizer accounts for 0.3-5% of the mass of the finished polythiol product; more preferably 0.5-3%; and even more preferably 0.5-1%.

[0032] Further, the stabilizer is selected from at least one of dilauryl thiodipropionate, ditridecyl thiodipropionate, ditetradecyl thiodipropionate, dioctadecanol thiodipropionate, diphenyl phosphite, diisooctyl diphenyl phosphite, tetraphenyldipropylene glycol diphosphite, triphenyl phosphite, diisodecyl pentaerythritol diphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and 4,4'-thiobis(3-methyl-6-tert-butylphenol).

[0033] Furthermore, the stabilizer includes thiodipropionate and hindered phenol substances.

[0034] In a preferred embodiment, the stabilizer is a combination of dioctadecyl thiodipropionate and 2,6-di-tert-butyl-4-methylphenol, with a mass ratio of (0.5-5):1.

[0035] Preferably, the mass ratio of dioctadecanol thiodipropionate to 2,6-di-tert-butyl-4-methylphenol is (0.5-3):1.

[0036] More preferably, the mass ratio of dioctadecanol thiodipropionate to 2,6-di-tert-butyl-4-methylphenol is (0.5-1.5):1.

[0037] Furthermore, the pressure of the evaporation concentration process is -0.05 to -0.5 MPa, and the concentration temperature is 60-85°C.

[0038] Secondly, the present invention also provides a polythiol prepared according to the above method; the polythiol can be used in the low-temperature rapid curing process of adhesives (such as epoxy resin adhesives) due to its high purity and high thiol content.

[0039] Beneficial effects

[0040] The present invention provides a method for mass-producing polythiols. First, in the method, carbon dioxide is used instead of the highly toxic and dangerous H2S gas commonly used in the prior art, making the production process safer and more environmentally friendly. Second, the present invention further improves the reaction efficiency, product purity and the thiol content of the polythiols by optimizing the type of reaction catalyst, the content of the reactants and the process. In addition, the present invention optimizes different types of stabilizers and their contents, further improving the production reaction speed and the stability of the polythiols product. The method has a stable production process, a controllable process, few side reactions, high production efficiency and low cost, and can be used for the stabilization and large-scale production of polythiols. The polythiols prepared by the method have high purity and thiol content and excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the polythiol prepared in Example 1 DETAILED DESCRIPTION

[0042] Example

[0043] Example 1

[0044] This embodiment provides a method for mass production of polythiol, comprising the following steps:

[0045] S1. Add 10 kg of polyether polyol (BD-824) and 100 g of boron trifluoride ether to a glass reactor and stir at a stirring speed of 400 rpm. After heating to 110 ° C, slowly add 1 kg of epichlorohydrin using a constant pressure addition funnel. Turn on the coil cooling water to control the temperature and keep it at 110 ° C. After reacting for 5 hours, cool and stand to obtain a polyether chloride.

[0046] S2, 10kg of the chloride of the polyether obtained in step 1, 6kg of a 32wt.% aqueous solution of sodium hydrosulfide and 100g of pentamethyldiethylenetriamine were added to the autoclave with stirring at a stirring speed of 400rpm, and then vacuumed for 5min under -0.099MPa to remove the air in the autoclave, and 1.0MPa of carbon dioxide was introduced for pressurization; the system was heated to 100°C and reacted for 5h; after the reaction was completed, the temperature was lowered to 25°C, the pressure was released to remove the gas in the autoclave, and nitrogen was blown with it for 30min;

[0047] S3. Add 20 kg of a mixture of n-butanol and water (mass ratio of 1:1) into the autoclave through a flow meter for extraction and dissolution, remove unreacted sodium hydrosulfide in the system through an automatic liquid separation device in a mixing and settling tank, and then add 1 L of 0.1 mol / L hydrochloric acid for acidification to remove residual sodium hydrosulfide; adjust the pH of the system to 5, add 70 g of a stabilizer and mix evenly, then separate the aqueous phase through a mixing and settling tank, and pump the organic phase into an evaporator through a metering pump, and concentrate at -0.099 MPa and 70°C to obtain a polythiol product; wherein the stabilizer is a combination of dioctadecyl thiodipropionate and 2,6-di-tert-butyl-4-methylphenol in a mass ratio of 1:1.

[0048] Example 2

[0049] This embodiment provides a method for mass production of polythiol, comprising the following steps:

[0050] S1. Add 9.875 kg of polyether polyol (H5021) and 125 g of boron trifluoride ether to a glass reactor and stir at a stirring speed of 200 rpm. After heating to 120 ° C, slowly add 0.8 kg of epichlorohydrin using a constant pressure addition funnel. Turn on the coil cooling water temperature control to maintain the temperature at 120 ° C. After reacting for 4 hours, cool and stand to obtain a chloride of polyether;

[0051] S2. Add 10 kg of the polyether chloride obtained in step 1, 5.23 kg of a 25 wt.% aqueous sodium hydrosulfide solution, and 537 g of pentamethyldiethylenetriamine to the autoclave with stirring at 300 rpm. Vacuum the autoclave at -0.099 MPa for 5 minutes to remove air. Add 0.3 MPa of carbon dioxide to increase the pressure. Raise the temperature to 120°C and allow the reaction to proceed for 4 hours. Upon completion of the reaction, cool the autoclave to 25°C, release the pressure, and purge the autoclave with nitrogen for 30 minutes.

[0052] S3. Add 25 kg of a mixture of n-butanol and water (mass ratio is 2:1) into the autoclave through a flow meter for extraction and dissolution, remove the unreacted sodium hydrosulfide in the system through an automatic liquid separation device in a mixing and settling tank, and then add 0.5 L of 0.1 mol / L hydrochloric acid for acidification to remove the residual sodium hydrosulfide; adjust the pH of the system to 4, add a stabilizer and mix well, then separate the aqueous phase through a mixing and settling tank, and pump the organic phase into an evaporator through a metering pump, and concentrate at -0.05 MPa and 85 ° C to obtain a polythiol product; wherein the stabilizer is a combination of dioctadecyl thiodipropionate and 2,6-di-tert-butyl-4-methylphenol, and the mass ratio is 1.5:1.

[0053] Example 3

[0054] This embodiment provides a method for mass production of polythiol, comprising the following steps:

[0055] S1. Add 10 kg of polyether polyol (H9211) and 100 g of boron trifluoride ether to a glass reactor and stir at a stirring speed of 500 rpm. After heating to 100 ° C, slowly add 1 kg of epichlorohydrin using a constant pressure addition funnel. Turn on the coil cooling water temperature control to maintain the temperature at 100 ° C. After reacting for 7 hours, cool and stand to obtain polyether chloride;

[0056] S2. Add 10 kg of the chloride of the polyether obtained in step 1, 6 kg of a 45 wt.% aqueous sodium hydrosulfide solution, and 80 g of pentamethyldiethylenetriamine to the autoclave. Stir at 500 rpm and evacuate at -0.099 MPa for 5 minutes to remove air from the autoclave. Then, introduce 2 MPa of carbon dioxide to increase the pressure. Raise the temperature to 90°C and react for 7 hours. After the reaction is complete, cool the autoclave to 25°C, release the pressure, and purge the autoclave with nitrogen for 30 minutes.

[0057] S3. Add 22 kg of a mixture of n-butanol and water (mass ratio of 1:1) into the autoclave through a flow meter for extraction and dissolution, remove the unreacted sodium hydrosulfide in the system through an automatic liquid separation device in a mixing and settling tank, and then add 1.5 L of 0.1 mol / L hydrochloric acid for acidification to remove the residual sodium hydrosulfide; adjust the pH of the system to 6 and add a stabilizer to mix evenly, then separate the aqueous phase through a mixing and settling tank, and pump the organic phase into an evaporator through a metering pump, and concentrate at -0.5 MPa and 60°C to obtain a polythiol product; wherein the stabilizer is a combination of dioctadecyl thiodipropionate and 2,6-di-tert-butyl-4-methylphenol, and the mass ratio is 0.5:1.

[0058] Comparative Example 1

[0059] The method is basically the same as Example 1, except that the amount of carbon dioxide introduced is 0 MPa, and this embodiment is filled at normal pressure.

[0060] Comparative Example 2

[0061] The method is basically the same as Example 1, except that the amount of carbon dioxide introduced is 2 MPa, and this embodiment is a high-pressure filling.

[0062] Comparative Example 3

[0063] The process is basically the same as that of Example 1, except that no stabilizer is added in step S3.

[0064] Comparative Example 4

[0065] The process is basically the same as that in the embodiment, except that: Step S2 is as follows: 8.78 kg of the chloride of the polyether obtained in Step 1, 6 kg of a 32 wt.% aqueous sodium hydrosulfide solution and 132 g of pentamethyldiethylenetriamine are added into the autoclave and stirred.

[0066] Comparative Example 5

[0067] This embodiment provides a commercially available polyether thiol product, model number of which is Japan Toray QE-340.

[0068] Comparative Example 6

[0069] This embodiment provides a commercially available polyester thiol product, model 405 thiol.

[0070] The epichlorohydrin is a conventional commercial product, industrial grade, with a purity of >99.5%; the sodium hydrosulfide is a commercial product, in yellow liquid state; the carbon dioxide is a commercial product, with a purity of 99.9%; the n-butanol is a commercial product, with a purity of ≥99.0%; and the hydrochloric acid is a commercial product, with a concentration of 30 wt.%.

[0071] Performance testing method:

[0072] 1. Stability Test: Take 200g of the thiol sample from each example, add 20g of DMP-30 accelerator, and stir at 500rpm for 10 minutes until homogeneous. Then divide the sample into two equal portions: one at 25°C and the other at 70°C. After 5 days, remove the sample and cool it to 25°C by self-heating, and then test it under the same conditions. Due to the characteristics of thiols, they hardly react with epoxy resins without the addition of accelerators. Therefore, in product applications, they are usually combined with appropriate accelerators and prepared in advance to achieve rapid curing. Therefore, storage stability testing requires the addition of accelerators to test stability in the application. According to HJ / T 60-2000 "Determination of Sulfide in Water - Iodine-Based Method", the thiol content of the mixed samples of the examples and accelerators was measured after 5 days of storage at 25°C and 70°C.

[0073] 2. Gel time test method: Take 10g of commercially available E-51 epoxy resin and 10g of the sample after stability test in each example, stir evenly within 1 minute, and record the gel coagulation time, which is the gel time.

[0074] 3. Viscosity: The measurement temperature is 25℃ and it is carried out in accordance with GB / T 22235-2008.

[0075] Performance test results:

[0076] The test results are shown in Table 1.

[0077] Table 1

[0078]

[0079]

Claims

1. A method for mass production of polythiol, characterized in that: The following steps are involved: S1. Under the action of catalyst A, a polyol is reacted with a halide of propylene oxide to prepare a halide; S2, under the action of catalyst B, reacting the halide in S1, sodium hydrosulfide solution and a certain amount of reaction gas to obtain a primary product of polythiol; S3, extracting and acidifying to remove residual sodium hydrosulfide in the initial polythiol product, adjusting the pH of the system to 4-6, adding a stabilizer and mixing, and then evaporating and concentrating the system to obtain the finished product; The polyol is selected from at least one of a saturated aliphatic hydrocarbon polyol or a polyether polyol; The reaction gas is carbon dioxide; the carbon dioxide gas is introduced to make the pressure of the reaction system 0.3-2MPa; The stabilizer is a combination of dioctadecyl thiodipropionate and 2,6-di-tert-butyl-4-methylphenol, and the mass ratio of dioctadecyl thiodipropionate to 2,6-di-tert-butyl-4-methylphenol is (0.5-5):1; The catalyst A is boron trifluoride ethyl ether, and the mass ratio of boron trifluoride ethyl ether to polyether polyol is 1: (80-200); The amount of the catalyst B is 0.2-15 wt.% of the halide; The catalyst B is an amine catalyst, selected from any one or more of pentamethyldiethylenetriamine, DMP-30, bis(2-dimethylaminoethyl) ether, and tributylamine.

2. The method according to claim 1, characterized in that The molar ratio of the polyol to the halogenated propylene oxide is (1-10):

1.

3. The method according to claim 1, characterized in that The molar ratio of sodium hydrosulfide to propylene oxide halide in the sodium hydrosulfide solution is (1-5):

1.

4. polythiol prepared according to the method described in any one of claims 1 to 3.

5. The polythiol according to claim 4, characterized in that The polythiol is used in the curing process of the adhesive.

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