A method for synthesizing polycarbonate polyol containing carbamate structure in the main chain

Abstract

The invention belongs to the technical field of preparation of polycarbonate polyols, and in particular to a method for synthesizing polycarbonate polyols containing carbamate structures in the main chain. The present invention first adds cyclic carbonate to an autoclave, and evacuates to a system without air and carbon dioxide under stirring, then adds a small molecule polyamine, stirs evenly, then adds epoxide and a double metal cyanide catalyst, then passes carbon dioxide until the pressure reaches 0.5-5.0MPa, warms the reactor to 50-120°C, and continues to add carbon dioxide until the pressure reaches 1.0-10MPa, and isothermal reaction is performed for 0.5-100h. The main chain of the polycarbonate carbamate polyol prepared by the production process of the present invention contains a carbamate structure, and the molecule contains not only a carbonate structure, but also a carbamate structure, and when used to prepare polyurethane, a polyurethane with excellent mechanical properties can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of polycarbonate polyols, and particularly relates to a method for synthesizing a polycarbonate polyol with a main chain containing a carbamate structure. Background Art

[0002] Polyurethane is a widely used polymer, which is widely used in the fields of foam plastics, elastomers, coatings, adhesives, etc. Polyurethane is obtained by the reaction of isocyanate and polyol. Among them, carbon dioxide polymer polyol is a newly developed polyurethane raw material, which is formed by polymerization of carbon dioxide and propylene oxide, ethylene oxide, etc. under the catalyst of small molecule alcohol initiator. Its molecule contains carbonate group and ether group. Since the hydrolysis product of carbonate group is carbonic acid, it will not continue to catalyze hydrolysis, so that carbon dioxide polymer polyol type polyurethane has excellent hydrolysis resistance. At the same time, the carbonate bond and ether bond in carbon dioxide polymer polyol can interact with each other to form intramolecular and intermolecular hydrogen bonds, which has a great influence on the physical properties of polyurethane products. Moreover, with the increase of carbonate content in carbon dioxide polymer polyol, the mechanical properties of polyurethane products also increase. In addition, since this polyol uses carbon dioxide as the main raw material, it can achieve carbon fixation, which is of great significance to carbon peak and carbon neutrality, and therefore has received widespread attention.

[0003] At present, the research of preparing polycarbonate polyol with direct copolymerization of carbon dioxide and epoxide is more, and related research adopts double metal cyanide catalyst catalytic preparation more.Such as US4500704, US1747983A, CN103547368A, CN1032010C, CN103429637A, CN103403060A, CN101928390A, CN101623656A, "double metal cyanide complex catalysis epoxide and CO2 copolymerization research" (Zhejiang University doctoral dissertation, Chen Shang, 2004) and other patents or papers have announced solid or liquid double metal cyanide catalysts of different structures respectively, for catalytic carbon dioxide, epoxide copolymerization to prepare carbon dioxide polymer polyol, and part has entered industrialized production.But when using double metal catalyst to prepare carbon dioxide copolymer polyol, there are also some problems, affecting the large-scale application of this technology. These problems are mainly manifested in that when bimetallic catalysts or related processes are used to prepare polycarbonate polyols, a certain amount of by-product cyclic carbonates will be produced, and the content of the cyclic carbonates can account for 10-15% of the total product mass, resulting in a product yield of only 85-90%. Moreover, cyclic carbonate is a common chemical raw material and can be used as an electrolyte, a high-boiling point solvent, etc. However, cyclic carbonate has a relatively high boiling point. For example, ethylene carbonate formed by simple carbon dioxide and ethylene oxide has a boiling point of up to 248°C. Therefore, when separating cyclic carbonates, high temperature and high vacuum are required. During the high-temperature separation process, cyclic carbonates will decompose to produce small molecule diols. For example, when carbon dioxide and ethylene oxide are copolymerized to prepare carbon dioxide polymer polyols, the by-product ethylene carbonate produced and separated will contain trace amounts of ethylene glycol, diethylene glycol, triethylene glycol, etc., among which ethylene glycol has a boiling point of 197.3°C, diethylene glycol has a boiling point of 245°C, and triethylene glycol has a boiling point of 288°C. The boiling points of these diols are very similar to those of ethylene carbonate, especially diethylene glycol, whose boiling point is only 3°C different from that of ethylene carbonate, making it difficult to completely remove them by conventional separation processes, requiring a more complex distillation process. The purification and separation of cyclic carbonates makes the production process of polycarbonate polyols more complicated and increases the investment cost. Therefore, it is very necessary to develop a production process of polycarbonate polyols with low by-products and high polyol yield.

[0004] When using carbon dioxide polymer polyol to prepare polyurethane, in order to improve the performance of the final product, the amount of isocyanate and chain extender small molecule alcohol can be increased, because isocyanate and small molecule alcohol can form a carbamate structure through addition reaction, thereby improving the mechanical properties of the product. However, this method requires increasing the amount of isocyanate. Isocyanate is mainly prepared by phosgene method, and its market price is about twice that of polyol all year round. Therefore, increasing the amount of isocyanate will lead to an increase in the cost of the product.

[0005] In recent years, a few studies have also developed other preparation and production processes for synthesizing polyether polyols containing carbamate. For example, Chinese invention patent CN115785431A reports a method for introducing carbamate into polyetheramine polyols to improve the mechanical properties of the finished product obtained when the polyols are used to synthesize polyurethane. The method is to use amino-terminated polyetheramines and cyclic carbonates to react, and then introduce carbamate structures into the end groups of polyols. Although this method can improve the mechanical properties of polyols when preparing polyurethanes, the actual application value is limited due to the complex production process and high production cost of amino-terminated polyols.

[0006] In summary, in order to further promote the research and industrialization of carbon dioxide polymer polyols, it is particularly important to develop a new, low-cost, low-by-product production process for polycarbonate polyols with a main chain containing a carbamate structure. Summary of the invention

[0007] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for preparing polycarbonate-urethane polyols, wherein the method uses carbon dioxide, epoxide, cyclic carbonate and polyamine as raw materials to prepare polyols containing polycarbonate-urethane in the main chain through in-situ polymerization. The method has low cost, low by-products and high polyol yield.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure, the method comprising the following steps:

[0010] S1, adding cyclic carbonate into a high-pressure reactor, removing air and carbon dioxide in the system, adding polyamine, stirring evenly, and further adding epoxide and catalyst;

[0011] S2, introduce carbon dioxide, and when the pressure in the reactor reaches 0.5-5.0 MPa, raise the temperature to 40-120°C, continue to introduce carbon dioxide until the pressure in the reactor reaches 1.0-10 MPa, and then react at a constant temperature for 0.5-100 hours;

[0012] S3. After the reaction is completed, the target product polycarbonate-urethane polyol and the by-product cyclic carbonate are separated under high vacuum, and the separated cyclic carbonate is directly used for the next reaction.

[0013] According to the needs, when the cyclic carbonate is added, a certain amount of small molecule polyol can be added as a molecular weight regulator. The small molecule polyol can be ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyether polyol, polyester polyol, etc., which are used to jointly regulate the molecular weight and functionality of the product.

[0014] The present invention provides a production process of polycarbonate polyols with low cost, low overall by-products and containing a carbamate structure. The process uses cyclic carbonate, polyamine, epoxide, carbon dioxide and the like as raw materials, and obtains a carbon dioxide-based polycarbonate polyol containing a carbamate structure by in-situ polymerization under the action of a catalyst. The cyclic carbonate produced by the polymerization of the process method can be directly used for the next kettle production after simple separation. Through the combined production of different products, the process can be made to have low by-products or no by-products as a whole, thereby improving the yield of the product polycarbonate polyol. Although the cyclic carbonate recovered by the present invention also contains a trace amount of small molecule diols, these small molecule diols themselves can be used as molecular weight regulators for the copolymerization of carbon dioxide epoxide to prepare polycarbonate polyols, so the cyclic carbonate recovered by the present invention can be used directly without complicated refining and separation. Therefore, the production process of the present invention solves the problems of the current carbon dioxide-based polycarbonate polyol production process being complicated, the production cost being high, the by-product being high, and the need for complicated refining and separation procedures.

[0015] In addition, the carbon dioxide-based polycarbonate polyol obtained by the process method of the present invention contains not only a large number of carbonate bonds and ether bonds, but also urethane bonds in its molecule, and when used to prepare polyurethane, the mechanical properties of the product can be greatly improved. This also solves the problem that the mechanical strength of the final polyurethane product is low due to the low carbonate content in the current carbon dioxide-based polycarbonate polyol.

[0016] Preferably, the cyclic carbonate is selected from ethylene carbonate, propylene carbonate, cyclohexyl carbonate or a mixture of several thereof.

[0017] Preferably, the polyamine is selected from one or a mixture of ethylenediamine, propylenediamine, butylenediamine, cyclohexanedimethylamine, hexylenediamine, o-phenylenediamine, p-phenylenediamine, polyethylenepolyamine, ethanolamine, diethanolamine, and diphenylamine.

[0018] Preferably, the epoxide is selected from one or a mixture of ethylene oxide, propylene oxide, cyclohexene oxide and butylene oxide.

[0019] Preferably, the catalyst is a catalyst capable of catalyzing the copolymerization of carbon dioxide epoxide, and the catalyst is selected from one or a mixture of bimetallic catalysts, organic boron catalysts, zinc carboxylate catalysts, and porphyrin catalysts.

[0020] Preferably, the mass ratio of the cyclic carbonate to the epoxide is 1-20:100.

[0021] Preferably, the mole number of the polyamine is the same as the mole number of the cyclic carbonate, calculated based on the mole number of amino groups.

[0022] Preferably, the mass ratio of the cyclic carbonate to the catalyst is 1-20:0.01-0.1.

[0023] The second aspect of the present invention provides a polycarbonate polyol having a main chain containing a carbamate structure obtained by the synthesis method described in the first aspect.

[0024] The third aspect of the present invention provides the use of the polycarbonate polyol having a urethane structure in the main chain as described in the second aspect in the preparation of polyurethane.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a method for preparing a polycarbonate-carbamate polyol having a carbamate structure in the main chain by in-situ polymerization, wherein a cyclic carbonate is first added to a high-pressure reactor, and vacuum is drawn under stirring conditions until there is no air and carbon dioxide in the system, and then a small molecule polyamine is added to the reactor, and after stirring evenly, an epoxide and a double metal cyanide catalyst are added, and then carbon dioxide is introduced, and when the pressure in the reactor reaches 0.5-5.0MPa, the reactor is heated to 50-120°C, and carbon dioxide is continuously added until the pressure in the reactor reaches 1.0-10MPa, and the reaction is carried out at a constant temperature for 0.5-100h, so that a polycarbonate polyol having a carbamate structure in the main chain can be obtained. In general, the present invention has the following advantages:

[0027] (1) The present invention discloses a low-cost, overall low-by-product production process for preparing polycarbonate-urethane polyols by in-situ polymerization. The cyclic carbonate by-product produced by the previous polymerization can be used for the next polymerization, so that the production process exhibits low by-products or no by-products, thereby greatly improving the yield of the main product polycarbonate polyol, thereby improving the target yield and improving the plant operation efficiency.

[0028] (2) Compared with the existing preparation technology of polycarbonate polyols, the method of the present invention does not require the investment in the construction of refining and separation equipment for cyclic carbonate by-products, thereby reducing production equipment investment and operating costs and improving corporate competitiveness.

[0029] (3) In the production process of carbon dioxide-based polycarbonate polyol, the present invention introduces an in-situ reaction of cyclic carbonate and polyamine on the basis of in-situ polymerization, introduces a carbamate structure into the polycarbonate polyol molecule, and then obtains a carbon dioxide-based polycarbonate polyol containing a carbamate structure. Since the present invention introduces a carbamate structure into the carbon dioxide polymer polyol, the mechanical properties of the product are improved when synthesizing polyurethane. It is well known that when preparing polyurethane, the hard segment (i.e., the carbamate segment) is the key to affecting the mechanical strength of the product. Since the polyol prepared by the present invention contains a carbamate segment in the molecule itself, when using it to prepare polyurethane with the same mechanical properties, the amount of isocyanate can be effectively reduced, thereby reducing the cost of the product and improving the market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 NMR spectrum of the polyol prepared in Example 1;

[0031] Figure 2 is the infrared spectrum of the polyol prepared in Example 1;

[0032] Figure 3 This is the infrared spectrum of the polyol prepared in Comparative Example 1. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0035] The unit "part" used in the following examples is weight unit (kg).

[0036] Example 1: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0037] (1) Open the feed valve of a 2L autoclave (Weihai Huixin Chemical Machinery Co., Ltd., model GHS-2L), add 9 parts of propylene carbonate into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring conditions, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0038] (2) Open the feed valve (liquid feed port) of the autoclave, add 2.65 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly and open the feed valve (solid feed port) of the autoclave, add 0.05 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on Copolymerization of Epoxides and CO2 Catalyzed by Double Metal Cyanide Complexes" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and after the pressure in the autoclave reaches 0.5 MPa, close the air inlet valve of the autoclave. Start heating, raise the temperature of the reactor to 50°C, open the carbon dioxide feed valve of the high-pressure reactor, continue to add carbon dioxide until the pressure in the reactor reaches 2.5MPa, close the carbon dioxide inlet valve of the high-pressure reactor, and react at a constant temperature for 36 hours.

[0039] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, evacuate under vacuum for 1 hour, and vacuum separate to obtain 10.2 parts of propylene carbonate.

[0040] (4) The discharge system of the autoclave was opened to obtain 133.2 parts of carbon dioxide polymer polyol containing a carbamate structure. The hydroxyl value was 37.8 as determined by hydroxyl titration test, and the molecular weight was 2961 as calculated based on the hydroxyl value.

[0041] Example 1 uses 9 parts of cyclic carbonate to generate 10.2 parts of cyclic carbonate. If the 9 parts of cyclic carbonate are all recovered, then according to Example 1, 133.2 parts of the target product are prepared, and the net amount of by-products produced is 1.2 parts, the net yield of by-products is 0.9%, and the yield of the main product polycarbonate polyol reaches 99.1%.

[0042] Example 2: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0043] (1) Open the feed valve of a 2L autoclave, add 13.6 parts of propylene carbonate into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0044] (2) Open the feed valve of the autoclave, add 4 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly, open the feed valve of the autoclave, add 0.1 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on the Copolymerization of Epoxide and CO2 Catalyzed by Double Metal Cyanide Complex" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and close the air inlet valve of the autoclave after the pressure in the autoclave reaches 1MPa. Start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5MPa, close the carbon dioxide feed valve of the autoclave, and react at constant temperature for 36 hours.

[0045] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, vacuum pump for 1 hour, and vacuum separate to obtain 16.2 parts of propylene carbonate.

[0046] (4) The discharge system of the autoclave was opened to obtain 124 parts of carbon dioxide polymer polyol containing a carbamate structure. The hydroxyl value was 55.9 as determined by hydroxyl titration test, and the molecular weight was 2002 as calculated based on the hydroxyl value.

[0047] Example 2 uses 13.6 parts of cyclic carbonate to generate 16.2 parts of cyclic carbonate. If the 13.6 parts of cyclic carbonate are all recovered, then according to Example 2, 124 parts of the target product are prepared, and the net amount of by-products produced is 2.6 parts, the net yield of by-products is 2.1%, and the yield of the main product polycarbonate polyol reaches 97.9%.

[0048] Example 3: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0049] (1) Open the feed valve of a 2L autoclave, add 17 parts of propylene carbonate recovered in Example 2 into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0050] (2) Open the feed valve of the autoclave, add 9.67 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly, open the feed valve of the autoclave, add 0.1 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on Copolymerization of Epoxide and CO2 Catalyzed by Double Metal Cyanide Complex" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and close the air inlet valve of the autoclave after the pressure in the autoclave reaches 0.5MPa. Start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5MPa, close the carbon dioxide feed valve of the autoclave, and react at constant temperature for 48h.

[0051] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, vacuum pump for 1 hour, and vacuum separate to obtain 20.5 parts of propylene carbonate.

[0052] (4) The discharge system of the autoclave was opened to obtain 137 parts of carbon dioxide polymer polyol containing a carbamate structure. The hydroxyl value thereof was 67.9 as determined by hydroxyl titration test, and the molecular weight thereof was calculated to be 1650 according to the hydroxyl value.

[0053] Example 3 uses 17 parts of cyclic carbonate to generate 20.5 parts of cyclic carbonate. Since all 17 parts of cyclic carbonate are recovered, 137 parts of target product are prepared according to Example 2. The net amount of by-products produced is 3.5 parts, the net yield of by-products is 2.5%, and the yield of the main product polycarbonate polyol reaches 97.5%.

[0054] Example 4: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0055] (1) Open the feed valve of a 2L autoclave, add 6 parts of propylene carbonate recovered in Example 3 into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0056] (2) Open the feed valve of the autoclave, add 1.76 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly, open the feed valve of the autoclave, add 0.05 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on the Copolymerization of Epoxide and CO2 Catalyzed by Double Metal Cyanide Complex" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and close the air inlet valve of the autoclave after the pressure in the autoclave reaches 0.5MPa. Start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5MPa, close the carbon dioxide feed valve of the autoclave, and react at constant temperature for 24 hours.

[0057] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, vacuum pump for 1 hour, and vacuum separate to obtain 5.1 parts of propylene carbonate.

[0058] (4) The discharge system of the autoclave was opened to obtain 133.2 parts of carbon dioxide polymer polyol containing a carbamate structure. The hydroxyl value was 24.7 as determined by hydroxyl titration test, and the molecular weight was 4529 as calculated based on the hydroxyl value.

[0059] Example 4 uses 6 parts of cyclic carbonate to generate 5.1 parts of cyclic carbonate. Since all 6 parts of cyclic carbonate are recovered, 133.2 parts of target product are prepared according to Example 4. The net amount of by-products produced is -0.9 parts, the net yield of by-products is -0.7%, and the yield of the main product polycarbonate polyol reaches 100.3%.

[0060] Example 5: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0061] (1) Open the feed valve of a 2L autoclave, add 30 parts of propylene carbonate recovered in Example 4 into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0062] (2) Open the feed valve of the autoclave, add 1.76 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly, open the feed valve of the autoclave, add 0.05 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on the Copolymerization of Epoxide and CO2 Catalyzed by Double Metal Cyanide Complex" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and close the air inlet valve of the autoclave after the pressure in the autoclave reaches 0.5MPa. Start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5MPa, close the carbon dioxide feed valve of the autoclave, and react at constant temperature for 24 hours.

[0063] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, vacuum pump for 1 hour, and vacuum separate to obtain 38.8 parts of propylene carbonate.

[0064] (4) The discharge system of the autoclave was opened, and 139.6 parts of carbon dioxide polymer polyol containing a carbamate structure were obtained after the discharge. The hydroxyl value thereof was 118 as determined by hydroxyl titration test, and the molecular weight thereof was calculated to be 949 based on the hydroxyl value.

[0065] Example 5 uses 30 parts of cyclic carbonate to generate 38.8 parts of cyclic carbonate. Since all 30 parts of cyclic carbonate are recovered, 139.6 parts of target product are prepared according to Example 5. The net amount of by-products produced is 8.8 parts, the net yield of by-products is 6.3%, and the yield of the main product polycarbonate polyol reaches 93.7%.

[0066] Example 6: A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure

[0067] (1) Open the feed valve of a 2L autoclave, add 13.6 parts of propylene carbonate and 1 part of dipropylene glycol into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0068] (2) Open the feed valve of the autoclave, add 4 parts of ethylenediamine into the autoclave, close the feed valve of the autoclave, stir evenly, open the feed valve of the autoclave, add 0.1 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper "Study on the Copolymerization of Epoxide and CO2 Catalyzed by Double Metal Cyanide Complex" (Zhejiang University Doctoral Dissertation, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and close the air inlet valve of the autoclave after the pressure in the autoclave reaches 1MPa. Start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5MPa, close the carbon dioxide feed valve of the autoclave, and react at constant temperature for 36 hours.

[0069] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, vacuum pump for 1 hour, and vacuum separate to obtain 16.7 parts of propylene carbonate.

[0070] (4) The discharge system of the autoclave was opened to obtain 123.1 parts of carbon dioxide polymer polyol containing a carbamate structure. The hydroxyl value thereof was 64 as determined by hydroxyl titration test, and the molecular weight thereof was calculated to be 1748 based on the hydroxyl value.

[0071] Example 2 uses 13.6 parts of cyclic carbonate to generate 16.7 parts of cyclic carbonate. If the 13.6 parts of cyclic carbonate are all recovered, then according to Example 2, 123.1 parts of target product are prepared, and the net amount of by-products produced is 3.1 parts, the net yield of by-products is 2.5%, and the yield of the main product polycarbonate polyol reaches 97.5%.

[0072] Comparative Example 1: Preparation method of conventional carbon dioxide polymer polyol

[0073] (1) Open the feed valve of a 2L autoclave, add 20 parts of polypropylene glycol 400 into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring conditions, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0074] (2) Open the feed valve of the autoclave, add 0.1 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper (Study on the Copolymerization of Epoxides and CO2 Catalyzed by Double Metal Cyanide Complexes (PhD Dissertation of Zhejiang University, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, and open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and after the pressure in the autoclave reaches 1 MPa, close the air inlet valve of the autoclave; start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5 MPa, close the carbon dioxide feed valve of the autoclave, and react at a constant temperature for 36 hours.

[0075] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, and vacuum pump for 1 hour to separate and obtain 15.3 parts of propylene carbonate.

[0076] (4) The discharge system of the autoclave was opened to obtain 146.1 parts of carbon dioxide polymer polyol. The hydroxyl value was 38.3 as determined by hydroxyl titration test, and the molecular weight was 2922 as calculated based on the hydroxyl value.

[0077] Comparative Example 1 generates 15.3 parts of cyclic carbonate, and according to the calculation of 146.1 parts of the target product prepared in Comparative Example 1, the net amount of by-products generated is 15.3 parts, the net yield of by-products is 10.5%, and the net yield of the main product is 89.5%.

[0078] Comparative Example 2: Preparation method of conventional carbon dioxide polymer polyol

[0079] (1) Open the feed valve of a 2L autoclave, add 30 parts of polypropylene glycol 400 into the autoclave, close the feed valve of the autoclave, start stirring, evacuate under stirring conditions, and flush with nitrogen, repeat several times to ensure that there is no air and carbon dioxide in the system.

[0080] (2) Open the feed valve of the autoclave, add 0.1 parts of double metal cyanide complex (DMC) catalyst (prepared according to the method described in the paper (Study on the Copolymerization of Epoxides and CO2 Catalyzed by Double Metal Cyanide Complexes (PhD Dissertation of Zhejiang University, Chen Shang, 2004)) into the autoclave, close the catalyst feed port, open the epoxide feed valve of the autoclave, and open the epoxide metering pump, add 100 parts of propylene oxide into the autoclave, close the epoxide feed valve of the autoclave, open the carbon dioxide feed valve of the autoclave, add carbon dioxide, and after the pressure in the autoclave reaches 1 MPa, close the air inlet valve of the autoclave; start heating, raise the temperature of the autoclave to 60°C, open the carbon dioxide feed valve of the autoclave, continue to add carbon dioxide until the pressure in the autoclave reaches 2.5 MPa, close the carbon dioxide feed valve of the autoclave, and react at a constant temperature for 48 hours.

[0081] (3) Open the pressure relief valve of the high-pressure reactor. After the pressure is released, heat the material to 140° C., then open the cooling device of the vacuum recovery system, and vacuum pump for 1 hour to separate and obtain 22.2 parts of propylene carbonate.

[0082] (4) The discharge system of the autoclave was opened to obtain 150.5 parts of carbon dioxide polymer polyol. The hydroxyl value was 55.8 as determined by hydroxyl titration test, and the molecular weight was 2007 as calculated based on the hydroxyl value.

[0083] Comparative Example 1 generates 22.2 parts of cyclic carbonate, and according to Comparative Example 1, 150.5 parts of the target product are prepared. The net amount of by-products generated is 22.2 parts, the net yield of by-products is 14.8%, and the net yield of the main product is 85.2.

[0084] Comparing the products of Comparative Example 1 and Example 1, it can be seen that the molecular weight of the target products of both are about 3000, wherein the net by-product generation of Example 1 is 0.9%, and the yield of the main product reaches 99.1%, while the net by-product generation of Comparative Example 1 is 10.5%, and the yield of the main product is 89.5%. At the same time, comparing Comparative Example 2 with Example 2, the molecular weight of their target products is about 2000, wherein the net by-product generation of Example 2 is 2.1%, and the yield of the main product is 97.9%, while the by-product generation of Comparative Example 2 is 14.8%, and the yield of the main product is 85.2%. Through the above comparison, it can be found that the method of the present invention can greatly improve the yield of the main product polycarbonate polyol.

[0085] Experimental example: Preparation performance test of polyols

[0086] (1) The polycarbonate-urethane polyol prepared in Example 1 was subjected to infrared and nuclear magnetic resonance tests.

[0087] Figure 1 In the NMR spectrum, a (7.0-7.2ppm) is the hydrogen peak on NH in the intramolecular carbamate, and b (2.9ppm) is the peak on CH2 between two carbamates (this peak is the same as the carbamate peak reported in the literature, see "Song Wenjian et al., Synthesis and Structural Characterization of a Carbamate Monomer, Chemical Industry Progress, 2011, 30: 322-324."). The a / b peak area ratio is 1:1.95, indicating that ethylenediamine generates carbamate, and the peak areas of the two carbamates and the two methylene groups in ethylenediamine are 1:2. c (4.6-5.0ppm) and f (3.8-4.3ppm) are hydrogen peaks on CH2 or CH adjacent to carbonate bonds, g (3.1-3.8ppm) is a hydrogen peak on CH2 or CH adjacent to ether bonds, e (4.5ppm) is a hydrogen peak on cyclic carbonate byproducts, h (1.3ppm) is a hydrogen peak on CH3 in cyclic carbonates, i is a hydrogen peak on CH3 in CH adjacent to carbonates, and j is a hydrogen peak on CH3 in CH adjacent to ether bonds. h is the peak of the solvent DMSO. The above NMR data show that after the reaction of ethylenediamine and cyclic carbonate, carbon dioxide propylene oxide copolymerization is successfully initiated to prepare low molecular weight polypropylene carbonate diol.

[0088] From the infrared spectra of Example 1 and Comparative Example 1 ( Figure 2 , Figure 3 ) It can be seen that there are obvious absorption peaks of carbonate at 1735, absorption peaks of cyclic carbonate at 1800, and absorption peaks of OH association at 3500, indicating that polycarbonate diol is generated. At the same time, a new absorption peak appears at 1530 in Example 1, which is the stretching vibration peak of NH. This peak is the same as the carbamate peak reported in the literature (see "Song Wenjian et al., Synthesis and Structural Characterization of a Carbamate Monomer, Chemical Industry Progress, 2011, 30: 322-324."), indicating that the product of Example 1 contains a carbamate structure.

[0089] (2) Effect of the polycarbonate-urethane polyol prepared in Example 1 on the performance of the finished polyurethane product

[0090] Add 1,4-butanediol as a chain extender (the amount is 10% of the amount of polyol) to the polyols obtained in Example 1-2 and Comparative Example 1-2, then add DMF and MDI to make a solution with a solid content of 70%, and control the molar ratio of isocyanate to polyol to 0.95, then react for 3 hours at 60°C, and gradually add DMF and MDI during the reaction process, so that the molar ratio of isocyanate to polyol is finally about 1.1, and the solid content of the system is 30±1wt%, to obtain a carbon dioxide polymer-based polyurethane solution. Then add 30±1wt% of resin to the obtained solution to prepare a premixed solution, and then dilute it with a DMF solution twice the total mass of the premixed solution to obtain a resin mixed solution. Finally, the resin mixed solution is introduced into a mold made of HDPE material, and after drying at 80°C in a blast drying oven for 48 hours to completely dry out the DMF solvent, a resin film with a thickness of 0.3±0.01mm is obtained.

[0091] The prepared 0.3 mm thick film was cut into square films with a side length of 2 cm and weighed to obtain m0. Subsequently, the film was completely immersed in toluene solvent at room temperature for 24 hours, taken out, dried with filter paper, and weighed to obtain m. Finally, the solvent absorption rate was calculated according to the following formula:

[0092] Solvent absorption rate = (m-m0) / m0%.

[0093] At the same time, the CMT4204 universal tensile testing machine of Meters Industrial Systems (China) Co., Ltd. was used to test the mechanical strength of the polyurethane film; the tensile properties were tested in accordance with the standard "GB / T13022-1991 Test method for tensile properties of plastic films" with a test speed of 200mm / min; and the hardness was tested using an LX-A Shore durometer in accordance with the standard "GBT 6031-1998 Determination of hardness of vulcanized rubber or thermoplastic rubber".

[0094] It can be clearly seen from Table 1 that compared with the polycarbonate polyols prepared in Comparative Examples 1 and 2, the carbon dioxide polymer polyols prepared in Examples 1 and 2 have greatly improved tensile strength, elongation at break, and solvent resistance of the polyurethane products prepared therefrom due to the presence of carbamate in the main chain, showing higher hardness, strength and better solvent resistance.

[0095] Table 1 Performance indicators of polyurethane finished products

[0096]

[0097] In summary, the polycarbonate-carbamate polyol with a carbamate structure in the main chain obtained by the production process of the present invention contains not only a carbonate structure but also a carbamate structure in its molecule, and when used to prepare polyurethane, a polyurethane with excellent mechanical properties can be obtained. At the same time, the method of the present invention has low cost, low by-products, and high polyol yield, which is conducive to large-scale production and promotion.

[0098] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure, characterized in that: The following steps are involved: S1, adding cyclic carbonate into a high-pressure reactor, removing air and carbon dioxide in the system, adding polyamine, stirring evenly, and further adding epoxide and catalyst; The mass ratio of the cyclic carbonate to the epoxide is 1-20:100, and the molar number of the polyamine is the same as the molar number of the cyclic carbonate based on the molar number of the amino group; S2, introduce carbon dioxide, and when the pressure in the reactor reaches 0.5-5.0 MPa, raise the temperature to 40-120°C, continue to introduce carbon dioxide until the pressure in the reactor reaches 1.0-10 MPa, and then react at a constant temperature for 0.5-100 hours; S3. After the reaction is completed, the target product polycarbonate-urethane polyol and the by-product cyclic carbonate are separated under high vacuum, and the separated cyclic carbonate is directly used for the next reaction.

2. The method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure according to claim 1, characterized in that: The cyclic carbonate is selected from ethylene carbonate, propylene carbonate, cyclohexyl carbonate or a mixture of the two or more thereof.

3. The method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure according to claim 1, characterized in that: The polyamine is selected from one or a mixture of ethylenediamine, propylenediamine, butylenediamine, cyclohexanedimethylamine, hexamethylenediamine, o-phenylenediamine, p-phenylenediamine, polyethylenepolyamine, and diphenylamine.

4. The method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure according to claim 1, characterized in that: The epoxide is selected from one or a mixture of ethylene oxide, propylene oxide, cyclohexene oxide and butylene oxide.

5. The method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure according to claim 1, characterized in that: The catalyst is selected from one or a mixture of double metal cyanide complex catalysts, organic boron catalysts, zinc carboxylate catalysts, and porphyrin catalysts.

6. The method for synthesizing a polycarbonate polyol having a main chain containing a carbamate structure according to claim 1, characterized in that: The mass ratio of the cyclic carbonate to the catalyst is 1-20:0.01-0.

1.

7. A polycarbonate polyol having a main chain containing a carbamate structure obtained by the synthesis method according to any one of claims 1 to 6.

8. Use of the polycarbonate polyol having a urethane structure in the main chain according to claim 7 in the preparation of polyurethane.

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