Dimer acid polyester polyol as well as preparation method and application thereof

Abstract

The invention discloses dimer acid polyester polyol as well as a preparation method and application thereof, and belongs to the technical field of synthesis of polyester polyol. The method for preparing the dimer acid polyester polyol comprises the following steps: (1) putting dimer acid and polyol into a reaction container; (2) under a positive pressure condition, gradient heating is carried out, so that the dimer acid and the polyol are subjected to an esterification reaction, the pressure of the positive pressure condition is 0.05 MPa-0. 9 MPa, and the gradient heating comprises at least two heat preservation stages; and (3) carrying out condensation polymerization under a negative pressure condition to obtain the dimer acid polyester polyol. In the esterification stage, the raw materials react in a positive pressure maintaining and gradient heating manner, so that the esterification rate in the esterification stage can be greatly improved, the acid value of the materials is reduced as much as possible, the water yield in the later polycondensation stage is reduced, meanwhile, the moisture in the materials before the polycondensation reaction can be removed as much as possible, and the'pantothenic acid 'phenomenon can be effectively avoided; and the performance of the product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyester polyol synthesis, in particular to dimer acid polyester polyol and a preparation method and application thereof. Background Art

[0002] Polyurethane is an organic polymer material that can be used to produce synthetic leather, foam plastics, coatings, adhesives, rubber (elastomers) and fibers. Polyester polyols are one of the main raw materials for synthesizing polyurethane, and are usually formed by the condensation of dicarboxylic acids and polyols. Dimer acid polyester polyols synthesized with dimer acid as raw material have unique advantages over traditional polyester polyols, such as high hydrolysis resistance, low glass transition temperature, and excellent fluidity; compared with polyether polyols, dimer acid polyester polyols also have excellent heat resistance, low water absorption, excellent oxidation resistance and stability.

[0003] The synthesis of dimer acid polyester polyol is similar to that of ordinary polyester polyol, including the early esterification stage and the late polycondensation stage. If the esterification rate is too low and the water output is small after the early esterification stage, a large amount of water will be generated in the late polycondensation to supplement the product and reach a balance with the removed water, and the acid value will decrease slowly or no longer decrease, that is, the "pantothenic acid" phenomenon; if too much water remains in the material, it will also affect the late polycondensation stage, resulting in the "pantothenic acid" phenomenon; at the same time, the esterification stage is accompanied by the discharge of water, which will bring out some of the raw material polyols, resulting in insufficient polyols in the late polycondensation stage, and the hydroxyl end-capping of the polymer product cannot be performed, and the acid value will be difficult to decrease, resulting in the "pantothenic acid" phenomenon, which will affect the product performance. Summary of the invention

[0004] The present invention aims to alleviate or solve at least one of the above-mentioned problems to at least some extent.

[0005] In one aspect of the present invention, a method for preparing dimer acid polyester polyol is proposed. In some embodiments of the present invention, the method for preparing dimer acid polyester polyol comprises: (1) placing dimer acid and polyol in a reaction vessel; (2) increasing the temperature in a gradient under positive pressure to make the dimer acid and the polyol undergo an esterification reaction, wherein the pressure of the positive pressure condition is 0.05MPa~0.9MPa, and the gradient temperature increase includes at least two heat preservation stages; (3) performing a polycondensation reaction under negative pressure to obtain dimer acid polyester polyol. In the esterification stage, the raw materials are reacted by using positive pressure holding and gradient temperature increase, which can greatly improve the esterification rate in the esterification stage, reduce the acid value of the material as much as possible, reduce the water production in the later polycondensation stage, and also remove the moisture in the material before the polycondensation reaction as much as possible, which can effectively avoid the occurrence of "pantothenic acid" phenomenon and help improve the performance of the product.

[0006] In some embodiments of the present invention, the method for preparing the dimer acid polyester polyol satisfies at least one of the following conditions: the purity of the dimer acid ≥ 70%; the dimer acid includes hydrogenated dimer acid; the polyol includes one or more of 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, diethylene glycol, 1,5-pentanediol; the molar ratio of the dimer acid to the polyol is 1:(1~2); before gradient heating, the air in the reaction vessel is displaced with nitrogen, and the pressure in the reaction vessel is positive pressure.

[0007] In some embodiments of the present invention, in step (2), the pressure under the positive pressure condition is 0.2 MPa to 0.8 MPa.

[0008] In some embodiments of the present invention, the gradient heating includes the following steps: heating to 170°C to 190°C, holding for 1 h to 4 h, and then continuing to heat to 200°C to 220°C, and holding for 1 h to 4 h.

[0009] In some embodiments of the present invention, the gradient heating includes the following steps: (2-1) heating to the first temperature and holding for the first time, the first temperature is 140°C to 160°C, and the first time is 0.5 h to 2 h; (2-2) heating to the second temperature and holding for the second time, the second temperature is 170°C to 190°C, and the second time is 1 h to 4 h; (2-3) heating to the third temperature and holding for the third time, the third temperature is 200°C to 220°C, and the third time is 1 h to 4 h. Thus, by using the gradient heating method to hold at multiple temperatures, on the one hand, the esterification reaction can be completed in a shorter time; on the other hand, it can at least to a certain extent avoid problems such as the generation rate of water in the system being too fast, carrying away the polyol in the reaction vessel, resulting in excessive loss of polyol.

[0010] In some embodiments of the present invention, the polycondensation reaction is carried out under negative pressure by means of gradient decompression, including at least two pressure-holding stages. Thus, it is beneficial to cap the product, thereby being beneficial to improving the performance of the product.

[0011] In some embodiments of the present invention, the polycondensation reaction is carried out under negative pressure and includes the following steps: (3-1) reducing the pressure to a first pressure and maintaining the pressure for a fourth time, where the first pressure is -0.06 MPa to -0.04 MPa and the fourth time is 0.5 h to 2 h; (3-2) reducing the pressure to a second pressure and maintaining the pressure for a fifth time, where the second pressure is -0.08 MPa to -0.07 MPa and the fifth time is 1 h to 5 h; (3-3) reducing the pressure to a third pressure and maintaining the pressure for a sixth time, where the third pressure is -0.1 MPa to -0.09 MPa and the sixth time is 1 h to 5 h. Thus, gradually reducing the pressure can at least to some extent reduce or even avoid the phenomenon of foaming and flushing, and is conducive to obtaining a polyester polyol with a suitable relative molecular mass.

[0012] In some embodiments of the present invention, after the esterification reaction is completed and before the polycondensation reaction is carried out under negative pressure, the method for preparing the dimer acid polyester polyol further includes: adjusting the pressure in the reaction vessel to atmospheric pressure, introducing nitrogen, adding a stabilizer to the reaction vessel, and keeping the temperature for 20 to 40 min. Then, a catalyst is added to the reaction vessel and the temperature is kept for 20 to 40 min. Thus, it is conducive to shortening the reaction time and improving the performance of the product.

[0013] In some embodiments of the present invention, the method for preparing the dimer acid polyester polyol satisfies at least one of the following conditions: the stabilizer includes one or more of triphenyl phosphate, triethyl phosphate, triethyl methylphosphonate, triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, and distearyl pentaerythritol diphosphite; the molar ratio of the dimer acid to the stabilizer is 100: (0.004 to 0.04); the catalyst includes one or more of stannous octoate, stannous oxalate, p-toluenesulfonic acid, tetrabutyl titanate, stannous chloride, and dibutyltin dilaurate; the molar ratio of the dimer acid to the catalyst is 100: (0.01 to 0.04).

[0014] On the other hand, the present invention provides a dimer acid polyester polyol. In some embodiments of the present invention, the dimer acid polyester polyol is prepared by the method described above. The acid value of the dimer acid polyester polyol is 0.1 mg KOH / g to 2 mg KOH / g, the hydroxyl value is 55 mg KOH / g to 90 mg KOH / g, the water content is ≤ 0.1%, and the Gardner color number is 1 to 9. Thus, the dimer acid polyester polyol has a low acid value, a high hydroxyl value, less water, and a low color number, and has excellent performance.

[0015] In yet another aspect of the present invention, the present invention provides an application of the aforementioned dimer acid polyester polyol in the synthesis of polyurethane. The aforementioned dimer acid polyester polyol has excellent properties, and using it in the synthesis of polyurethane is beneficial to improving the properties of polyurethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 The flowchart showing the method for preparing dimer acid polyester polyol according to an embodiment of the present invention is presented; Figure 2 The schematic structural diagram of the apparatus used for preparing dimer acid polyester polyol in an embodiment of the present invention is shown.

[0017] Description of the reference numerals in the drawings: 1: reaction vessel; 2: raw materials; 3: first valve; 4: stirrer; 5: rupture disc; 6: safety valve; 7: pressure transmitter; 8: regulating valve; 9: pressure relief valve; 10: condenser; 11: condensate inlet; 12: condensate outlet; 13: nitrogen; 14: first collection tank; 15: vacuum pump; 16: second collection tank; 17: second valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described by referring to the drawings below are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0019] In one aspect of the present invention, the present invention provides a method for preparing dimer acid polyester polyol. In some embodiments of the present invention, referring to Figure 1 , the method for preparing dimer acid polyester polyol may include the following steps: (1) Place dimer acid and polyol in a reaction vessel.

[0020] In some embodiments of the present invention, the reaction vessel may be a reaction kettle. Dimer acid and polyol can be placed in the reaction kettle, and then the raw materials are reacted by adjusting the temperature, pressure, etc. in the reaction kettle.

[0021] In some embodiments of the present invention, the purity of dimer acid can be ≥70%. For example, the purity of dimer acid can be 70%, 80%, 95%, 98%, 99%, etc. When the purity of dimer acid is within the above range, it is beneficial to shorten the reaction time and improve the properties of the product.

[0022] In some embodiments of the present invention, the purity of the dimer acid can be 70% - 80%. In some other embodiments of the present invention, the purity of the dimer acid can be ≥95%.

[0023] It should be noted that in the present invention, the purity of the dimer acid refers to the mass content of the dimer acid in the dimer acid raw material.

[0024] In some embodiments of the present invention, the dimer acid can include hydrogenated dimer acid. The unsaturated double bonds in the molecular structure of the hydrogenated dimer acid are hydrogenated. Using the hydrogenated dimer acid to prepare polyester polyol is beneficial to improving the water resistance, thermal stability and flexibility at low temperature of the polyester polyol.

[0025] In some embodiments of the present invention, the polyol can include one or more of 1,4 - butanediol, 1,6 - hexanediol, 2 - methyl - 1,3 - propanediol, ethylene glycol, 1,2 - propanediol, 1,3 - propanediol, neopentyl glycol, diethylene glycol, 1,5 - pentanediol. The above - mentioned materials can all react with the dimer acid under certain conditions to form polyester polyol.

[0026] In some embodiments of the present invention, the molar ratio of the dimer acid to the polyol can be 1:(1 - 2). For example, the molar ratio of the dimer acid to the polyol can be 1:1, 1:1.2, 1:1.5, 1:1.7, 1:2, etc. Thus, it can promote the full reaction of the dimer acid and the polyol, reduce the amount of unreacted monomers, improve the utilization rate of raw materials and reduce production costs; and it is beneficial to obtain products that meet the requirements of acid value and hydroxyl value.

[0027] It should be noted that the number of moles of the dimer acid = the mass of the dimer acid raw material × purity / the relative molecular mass of the dimer acid.

[0028] (2) Under positive pressure conditions, increase the temperature in a gradient manner to carry out the esterification reaction between the dimer acid and the polyol.

[0029] In some embodiments of the present invention, the pressure under positive pressure conditions can be 0.05 MPa - 0.9 MPa, and the gradient temperature increase can include at least two heat - preservation stages.

[0030] Dimer acid and polyol undergo an esterification reaction at high temperature. Since dimer acid is a long-chain unsaturated dibasic acid containing 36 carbon atoms, the flexible molecular chain will wrap the carboxyl groups at the end positions, resulting in a large steric hindrance during the reaction. Under normal pressure conditions, when the dimer acid reacts with the hydroxyl groups on the polyol, the reaction rate is often slow, the reaction time is long, and the esterification rate is low. In the present invention, appropriately increasing the pressure in the reaction system is beneficial to the forward progress of the esterification reaction; however, too high a pressure will inhibit the forward reaction and is not conducive to improving the esterification reaction rate; therefore, the inventors have obtained the following conclusion through a large number of experimental studies: the positive pressure can be set to 0.05 MPa to 0.9 MPa to promote the esterification reaction.

[0031] In a closed gas-liquid phase equilibrium system, the amount of a certain component evaporating from the liquid phase to the gas phase per unit time is equal to the amount condensing from the gas phase to the liquid phase, and the partial pressure of the gas phase of this component reaches its saturated vapor pressure. When the partial pressure of the gas phase of this component is lower than the saturated vapor pressure, the amount evaporating from the liquid phase to the gas phase is greater than the amount condensing from the gas phase to the liquid phase, and the difference between this evaporation amount and the condensation amount increases with the increase in the difference between the partial pressure of the gas phase of this component and the saturated vapor pressure. The saturated vapor pressure of a certain component is related to the temperature of the reaction system and has little relationship with the internal environmental pressure of the system. In other words, the greater the difference between the partial pressure of the gas phase of a certain component and its saturated vapor pressure, the faster the evaporation rate of this component from the liquid phase to the gas phase. Therefore, in the present invention, appropriately increasing the pressure in the esterification reaction stage to promote the esterification reaction will not cause adverse effects.

[0032] It should be noted that the positive pressure is in the range of 0.05 MPa to 0.9 MPa, which means that during the reaction process, the pressure can vary within the range of 0.05 MPa to 0.9 MPa. For example, the pressure of the reaction system can be adjusted and controlled through a pressure regulating component so that the pressure of the reaction system is not lower than 0.05 MPa. During the reaction process, if more gas is generated, a part of the gas can be discharged to make the pressure not exceed 0.9 MPa. It also should be noted that the positive pressure refers to that the pressure in the reaction vessel is greater than the standard atmospheric pressure. For example, a positive pressure of 0.05 MPa means that the pressure in the reaction vessel is 0.05 MPa higher than the standard atmospheric pressure; the negative pressure in the following text refers to that the pressure in the reaction vessel is less than the standard atmospheric pressure.

[0033] In some embodiments of the present invention, the pressure under positive pressure conditions can be one of 0.05 MPa to 0.65 MPa, 0.1 MPa to 0.7 MPa, 0.15 MPa to 0.75 MPa, 0.2 MPa to 0.8 MPa, 0.25 MPa to 0.85 MPa, 0.3 MPa to 0.9 MPa.

[0034] In some specific embodiments, the pressure under positive pressure conditions can be 0.2 MPa to 0.8 MPa. Thus, it is beneficial to further increase the esterification rate and promote the forward progress of the esterification reaction.

[0035] In some embodiments of the present invention, before gradient heating, nitrogen can be used to displace the air in the reaction vessel and make the pressure in the reaction vessel positive pressure. The reaction is carried out under a nitrogen atmosphere, which can avoid problems such as oxidation of the materials in the reaction vessel and is beneficial to improving the performance of the product.

[0036] In some embodiments of the present invention, gradient heating may include the following steps: heating to 170°C to 190°C, holding for 1 h to 4 h, continuing to heat to 200°C to 220°C, and holding for 1 h to 4 h. By adopting two heating and holding stages, water can be generated at an appropriate rate in the initial stage of the esterification reaction, without taking away too many raw materials in the reaction system; it is beneficial to promote the forward progress of the esterification reaction and improve the esterification rate in the esterification reaction stage.

[0037] In some embodiments of the present invention, gradient heating includes the following steps: (2-1) heating to the first temperature and holding for the first time, the first temperature is 140°C to 160°C, and the first time is 0.5 h to 2 h; (2-2) heating to the second temperature and holding for the second time, the second temperature is 170°C to 190°C, and the second time is 1 h to 4 h; (2-3) heating to the third temperature and holding for the third time, the third temperature is 200°C to 220°C, and the third time is 1 h to 4 h.

[0038] In some embodiments of the present invention, the first temperature can be 140°C, 145°C, 150°C, 155°C, 160°C, etc., and the first time can be 0.5 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 2 h, etc.; the second temperature can be 170°C, 175°C, 180°C, 185°C, 190°C, etc., and the second time is 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, etc.; the third temperature can be 200°C, 205°C, 210°C, 215°C, 220°C, etc., and the third time can be 1 h, 2 h, 3 h, 3.5 h, 4 h, etc.

[0039] In the initial stage of the esterification reaction, the concentration of reactants in the system is relatively high. If the reaction temperature is too high, the reaction between monomers is very intense, the water generation rate in the system is very fast, and it will take away the polyol in the reaction system. The loss of polyol will cause the material ratio to be out of balance and affect the relative molecular mass of the polyester polyol; at the same time, if directly raised to a relatively high reaction temperature, it may also lead to an increase in side reactions. In the present invention, by setting multiple heating and holding stages, a relatively sufficient esterification reaction can be carried out in a shorter reaction time, and moreover, the loss of raw materials can be reduced and the utilization rate of raw materials can be improved.

[0040] For the heating rate in each stage, there is no special limitation in the present invention, and those skilled in the art can select and set according to the actual situation. In some embodiments of the present invention, the heating rate of 0.5 °C / min to 10 °C / min can be adopted for heating.

[0041] (3) Carry out polycondensation reaction under negative pressure conditions to obtain dimer acid polyester polyol.

[0042] During the reaction process, as the reaction proceeds, the concentration of reactant monomers gradually decreases, the viscosity of the polymer continuously increases, low molecular substances are not easily discharged, the degree of reversible reaction increases, and the forward reaction rate gradually slows down. Increasing the vacuum degree of the polycondensation system is a method to promote the polycondensation reaction to proceed in the forward reaction direction. Therefore, in the polycondensation reaction where low-boiling substances such as water are generated, the method of vacuum decompression can be considered to remove small molecule products, so that the equilibrium shifts in the direction favorable for the formation of high molecular products. In the present invention, by carrying out the polycondensation reaction under negative pressure conditions, the discharge of low molecular substances can be promoted, so that the polycondensation reaction proceeds in the forward direction to obtain a product with a lower water content.

[0043] During the polycondensation reaction process, the temperature is the same as the temperature in the last heat preservation stage of the esterification reaction. For example, if the temperature in the last stage of gradient heating is 200 °C - 220 °C, then the temperature during the polycondensation reaction process is also 200 °C - 220 °C.

[0044] In some embodiments of the present invention, the polycondensation reaction under negative pressure conditions can be carried out in a gradient decompression manner, including at least two pressure holding stages. The speed of vacuum decompression also has a great influence on the product quality of the polycondensation reaction. When starting to pump vacuum, the vacuum degree should not be too large, because there are many low molecular substances in the condensate in the kettle at the beginning of pumping vacuum. If the vacuum degree rises too fast, the phenomenon of foaming and material flushing is likely to occur. Therefore, in the present invention, the method of gradually increasing the vacuum degree is adopted to avoid the occurrence of flooding phenomenon.

[0045] In some embodiments of the present invention, the polycondensation reaction under negative pressure conditions includes the following steps: (3-1) Decompress to the first pressure and hold the pressure for the fourth time. The first pressure is -0.06 MPa to -0.04 MPa, and the fourth time is 0.5 h to 2 h; (3-2) Decompress to the second pressure and hold the pressure for the fifth time. The second pressure is -0.08 MPa to -0.07 MPa, and the fifth time is 1 h to 5 h; (3-3) Decompress to the third pressure and hold the pressure for the sixth time. The third pressure is -0.1 MPa to -0.09 MPa, and the sixth time is 1 h to 5 h.

[0046] In some embodiments of the present invention, the vacuum-assisted polycondensation reaction may include the following steps: First, reduce the pressure of the reaction system to -0.06 MPa, -0.05 MPa or -0.04 MPa, and keep the pressure for 0.5 h, 0.8 h, 1 h, 1.5 h or 2 h; then, continue to evacuate to reduce the pressure of the reaction system to -0.08 MPa or -0.07 MPa, and keep the pressure for 1 h, 2 h, 3 h, 4 h or 5 h; then reduce the pressure of the reaction system to -0.09 MPa or -0.1 MPa, and keep the pressure for 1 h, 2 h, 3 h, 4 h or 5 h. Thus, by setting multiple pressure reduction and pressure holding stages, the vacuum degree is not too large at the beginning, which can avoid the phenomenon of foaming and flushing materials, and is also conducive to removing small molecule products such as water, thereby improving the performance of the product.

[0047] In some embodiments of the present invention, the vacuum evacuation should not be started too early. If it is carried out too early, the unreacted polyol will be evacuated, changing the raw material ratio and affecting the relative molecular mass of the polyester polyol. In some embodiments of the present invention, sampling tests will be carried out during the reaction process, and vacuum evacuation can be started when the acid value of the system drops to a certain level.

[0048] In some embodiments of the present invention, after the esterification reaction is completed and before the polycondensation reaction is carried out under negative pressure, the method for preparing dimer acid polyester polyol may further include the following steps: adjust the pressure in the reaction vessel to atmospheric pressure, introduce nitrogen, add a stabilizer to the reaction vessel, and keep the temperature for 20 - 40 min (for example, after adding the stabilizer, it can be kept at 20 min, 25 min, 30 min, 35 min or 40 min), then, add a catalyst to the reaction vessel and keep the temperature for 20 - 40 min (for example, after adding the catalyst, it can be kept at 20 min, 25 min, 30 min, 35 min or 40 min). Adding a stabilizer can prevent the raw materials from being oxidized and also reduce the viscosity and chromaticity of the product; adding a catalyst can promote the reaction to proceed rapidly, thus shortening the reaction time.

[0049] In some embodiments of the present invention, when adjusting the pressure in the reaction vessel to atmospheric pressure and introducing nitrogen, the flow rate of nitrogen can be 2 L / min. Of course, the flow rate of nitrogen can also be adjusted according to the actual situation.

[0050] In some embodiments of the present invention, the stabilizer may include one or more of triphenyl phosphate, triethyl phosphate, triethyl methylphosphonate, triphenyl phosphite, tris(2,4 - di - tert - butylphenyl) phosphite, and distearyl pentaerythritol diphosphite. The above stabilizers can all play a role in preventing the raw materials from being oxidized to a certain extent, and can also reduce the viscosity and chromaticity of the product to a certain extent.

[0051] In some embodiments of the present invention, the molar ratio of dimer acid to stabilizer can be 100:(0.004 - 0.04). For example, the molar ratio of dimer acid to stabilizer can be 100:0.004, 100:0.008, 100:0.01, 100:0.02, 100:0.03 or 100:0.04. Thus, the added stabilizer can reduce side reactions during the synthesis of polyester polyol, which is beneficial to improving the purity and performance of the product.

[0052] In some embodiments of the present invention, the catalyst can include one or more of stannous octoate, stannous oxalate, p-toluenesulfonic acid, tetrabutyl titanate, stannous chloride, dibutyltin dilaurate. The above catalysts can accelerate the reaction rate during the synthesis of polyester polyol, thereby shortening the reaction time.

[0053] In some embodiments of the present invention, the molar ratio of dimer acid to catalyst can be 100:(0.01 - 0.04). For example, the molar ratio of dimer acid to catalyst can be 100:0.01, 100:0.02, 100:0.03 or 100:0.04. Thus, the added catalyst can increase the reaction rate and shorten the reaction time; adding the catalyst in accordance with the above ratio can avoid problems such as increased impurities and affecting the chromaticity of the product caused by excessive addition.

[0054] In some embodiments of the present invention, the Figure 2 shown device can be used to prepare dimer acid polyester polyol. In some embodiments, referring to Figure 2 , raw material 2 can be put into reaction vessel 1, and reaction vessel 1 can be a reaction kettle. Open the first valve 3 to displace the air in reaction vessel 1. Set the low pressure value of reaction vessel 1 to 0.2 MPa and the high pressure value to 0.8 MPa through pressure transmitter 7, and fill in nitrogen 13 to make the pressure in reaction vessel 1 reach 0.2 MPa; start stirring (using stirrer 4 for stirring) and heating, and slowly raise the temperature. The stirring speed can be 250 r / min. There are also bursting disc 5 and safety valve 6 connected to reaction vessel 1. Bursting disc 5 is a component that can automatically burst when the internal pressure of the device exceeds a certain limit, and can quickly release the pressure to prevent the device from exploding due to overpressure; safety valve 6 can also automatically open when the pressure in the device exceeds a certain limit to release the excess pressure and protect the safety of personnel and the device.

[0055] In some embodiments, when the temperature rises to a certain level, the water vapor produced by the esterification reaction of the raw materials gradually causes a significant increase in the pressure inside the reaction vessel 1; continue to raise the temperature to the first temperature and keep it warm. During this period, the generation of water vapor will cause the pressure inside the reaction vessel 1 to exceed the high pressure value of 0.8 MPa. At this time, the pressure relief valve 9 automatically opens, reducing the pressure inside the reaction vessel 1 to the low pressure value of 0.2 MPa; gradually raise the temperature to the second temperature and keep it warm. During this period, the generation of water vapor will cause the pressure inside the reaction vessel 1 to exceed the high pressure value of 0.8 MPa, and the pressure relief valve 9 automatically opens, reducing the pressure inside the reaction vessel 1 to the low pressure value of 0.2 MPa; gradually raise the temperature to the third temperature and keep it warm. During this period, the generation of water vapor will cause the pressure inside the reaction vessel 1 to exceed the high pressure value of 0.8 MPa, and the pressure relief valve 9 automatically opens, reducing the pressure inside the reaction vessel 1 to the low pressure value of 0.2 MPa. Close the pressure transmitter 7, relieve the pressure inside the reaction vessel 1 to atmospheric pressure, introduce nitrogen into the reaction vessel 1 at a flow rate of 2 L / min, add a stabilizer, keep it warm and stir for a period of time, then add a catalyst, keep it warm and stir for a period of time. Stop introducing nitrogen into the reaction vessel 1, open the vacuum pump 15, reduce the pressure, adjust the pressure inside the reaction vessel 1 to the first pressure, and keep it warm for a reaction period; adjust the pressure inside the reaction vessel 1 to the second pressure, and keep it warm for a reaction period; adjust the pressure inside the reaction vessel 1 to the third pressure, and keep it warm for a reaction period. If the acid value of the material inside the reaction vessel 1 > 2 mgKOH / g, continue the reaction. If the acid value of the material inside the reaction vessel 1 ≤ 2 mgKOH / g, close the vacuum pump 15, reduce the temperature inside the reaction vessel 1 to 100 °C or lower, and discharge and package the material.

[0056] During the reaction process, part of the material will enter the condenser 10. The temperature of the condensate inlet water 11 rises after passing through the condenser 10, forming the condensate outlet water 12, and the temperature of the material in the condenser 10 decreases. In the esterification stage, the pressure control includes pressure relief and pressure increase. When the pressure inside the reaction vessel 1 exceeds the set value, the pressure relief valve 9 opens for gas-phase pressure relief. When the pressure inside the reaction vessel 1 is lower than the set value, the first valve 3 opens to fill the reaction vessel 1 with nitrogen 13 for pressure increase. The material distilled out during the esterification stage enters the first collection tank 14. The polycondensation stage is a negative pressure operation process. In this stage, the pressure relief valve 9 opens. First, the reaction vessel 1 is evacuated to near the set pressure by the vacuum pump 15, then the pressure relief valve 9 is closed, and the vacuum degree inside the reaction vessel 1 is adjusted through the regulating valve 8 in the bypass to ensure the stability of the vacuum degree. The material distilled out during this stage enters the second collection tank 16. A plurality of second valves 17 are also provided in this device. The number and position of the second valves 17 can be adjusted according to the actual situation to better regulate and control the on-off of each pipeline.

[0057] Generally speaking, in the esterification stage of the present invention, after the reaction vessel is replaced with N2 and sealed, the temperature is raised in segments. The reaction vessel is connected to a pressure transmitter (with interlock settings, and when the pressure exceeds the set high value, it will be depressurized to the set low value). During this period, there are several automatic depressurizations, which can not only fully convert the reaction raw materials, but also completely discharge the water. The acid value is measured regularly during the reaction; in the polycondensation stage, the pressure transmitter is closed, and the polycondensation reaction is carried out by means of vacuum distillation to remove small molecule products and promote the forward reaction of the reaction. Further, by means of gradient decompression and segmented vacuum pumping, the material undergoes a polycondensation reaction, and the product is dimer acid polyester polyol, which has the characteristics of high hydrolysis resistance, low glass transition temperature, excellent fluidity, low water absorption, antioxidant property and stability. The preparation method of the present invention avoids the occurrence of pantothenic acid phenomenon, and the raw materials can be utilized to the greatest extent, which is green and safe.

[0058] In another aspect of the present invention, the present invention provides a dimer acid polyester polyol. In some embodiments of the present invention, the dimer acid polyester polyol is prepared by using the method described above. Thus, the dimer acid polyester polyol has a high purity and can be used for synthesizing polyurethane.

[0059] In some embodiments of the present invention, the acid value of the dimer acid polyester polyol can be 0.1mgKOH / g to 2mgKOH / g, the hydroxyl value can be 55mgKOH / g to 90mgKOH / g, the water content is ≤0.1%, and the Gardner color number can be 1 to 9. Thus, the dimer acid polyester polyol has excellent properties, high purity, low acid value, high hydroxyl value and low color number. When used for synthesizing polyurethane, the high purity and low acid value of the polyester polyol help to reduce side reactions, which is beneficial to improving the quality of polyurethane; the low color number of the polyester polyol means lighter color, which is beneficial to synthesizing a more transparent polyurethane product in appearance and can improve the market competitiveness of the product.

[0060] In still another aspect of the present invention, the present invention provides the application of the above-mentioned dimer acid polyester polyol in synthesizing polyurethane. The dimer acid polyester polyol prepared by using the method described above has high purity and excellent properties and can be used for synthesizing polyurethane.

[0061] The present invention will be described below through specific examples. Those skilled in the art can understand that the following specific examples are only for the purpose of illustration and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are commercially available. If the specific processing conditions and methods are not clearly described in the following examples, the conditions and methods known in the art can be used for processing.

[0062] Example 1 In this example,Figure 2 The device shown is used to prepare dimer acid polyester polyol.

[0063] 650 g of dimer acid (mass content ≥ 95%) and 157 g of 1,4-butanediol are put into reaction vessel 1 (reaction kettle). The first valve 3 is opened to displace the air in reaction vessel 1. The pressure transmitter 7 sets the low pressure value of reaction vessel 1 to 0.05 MPa and the high pressure value to 0.65 MPa. Nitrogen 13 is filled into reaction vessel 1 to make the pressure in reaction vessel 1 reach 0.05 MPa. Stirring and heating are started, and the temperature is slowly raised. The stirring speed is 250 r / min. After the temperature rises to 140 °C, the water vapor produced by the esterification reaction of the materials gradually makes the pressure in reaction vessel 1 increase significantly. The temperature is gradually raised to 160 °C and kept for 1 h. During this period, the generation of water vapor will make the pressure in reaction vessel 1 exceed the high pressure value of 0.65 MPa, and the pressure relief valve 9 will open automatically, and the pressure in reaction vessel 1 will drop to the low pressure value of 0.05 MPa. The temperature is gradually raised to 180 °C and kept for 2 h. During this period, the generation of water vapor will make the pressure in reaction vessel 1 exceed the high pressure value of 0.65 MPa, and the pressure relief valve 9 will open automatically, and the pressure in reaction vessel 1 will drop to the low pressure value of 0.05 MPa. The temperature is gradually raised to 200 °C and kept for 2 h. During this period, the generation of water vapor will make the pressure in reaction vessel 1 exceed the high pressure value of 0.65 MPa, and the pressure relief valve 9 will open automatically, and the pressure in reaction vessel 1 will drop to the low pressure value of 0.05 MPa.

[0064] The pressure transmitter 7 is closed, the pressure in reaction vessel 1 is released to atmospheric pressure, nitrogen is introduced into reaction vessel 1 at a flow rate of 2 L / min, 0.1 g of stabilizer triphenyl phosphate is added, and it is kept warm and stirred for 20 min. Then, 0.07 g of catalyst stannous octoate is added, and it is kept warm and stirred for 20 min.

[0065] The first valve 3 is closed, the nitrogen supply is stopped, the vacuum pump 15 is opened, the pressure in reaction vessel 1 is adjusted to -0.06 MPa, and it is kept warm and reacted for 45 min; the pressure in reaction vessel 1 is adjusted to -0.08 MPa, and it is kept warm and reacted for 1.5 h; the pressure in reaction vessel 1 is adjusted to -0.095 MPa, and it is kept warm and reacted for 1.5 h. If the acid value of the materials in reaction vessel 1 > 2 mgKOH / g, the reaction continues. If the acid value of the materials in reaction vessel 1 ≤ 2 mgKOH / g, the vacuum pump 15 is closed, the temperature in reaction vessel 1 drops to 100 °C, and the product is discharged and packaged.

[0066] Comparative Example 1 Put 650 g of dimer acid and 157 g of 1,4-butanediol into reaction vessel 1. Close pressure transmitter 7, open pressure relief valve 9, open first valve 3, and introduce nitrogen into reaction vessel 1 at a flow rate of 2 L / min. Start stirring and heating, and slowly raise the temperature with a stirring speed of 250 r / min.

[0067] After the temperature rises to 140 °C, the water vapor produced by the esterification reaction of the materials will be discharged through pressure relief valve 9. Gradually raise the temperature to 160 °C and hold for 1 h; gradually raise the temperature to 180 °C and hold for 2 h; gradually raise the temperature to 200 °C and hold for 2 h.

[0068] Add 0.1 g of stabilizer triphenyl phosphate, hold and stir for 20 min, then add 0.07 g of catalyst stannous octoate, hold and stir for 20 min.

[0069] Close first valve 3, stop introducing nitrogen, open vacuum pump 15, adjust the pressure in reaction vessel 1 to -0.06 MPa, and hold for 45 min; adjust the pressure in reaction vessel 1 to -0.08 MPa and hold for 1.5 h; adjust the pressure in reaction vessel 1 to -0.095 MPa and hold for 12 h. If the acid value of the materials in the reaction vessel > 2 mg KOH / g, continue the reaction. If the acid value of the materials in the reaction vessel ≤ 2 mg KOH / g, turn off the vacuum, lower the temperature in the reaction kettle to 100 °C, and discharge and package.

[0070] The differences between Examples 2 to 32, Comparative Examples 1 - 4 and Example 1 are recorded in Table 1, and other steps and parameters are the same as those in Example 1.

[0071] Table 1

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] It should be noted that the purity of the low-purity dimer acid in Comparative Example 3 is in the range of 70% - 80%.

[0079] The physical and chemical properties of the materials in each example and comparative example are recorded in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] As can be seen from Table 1 and Table 2, in Comparative Example 1, positive pressure holding conditions were not adopted during the esterification stage. In Comparative Example 2, although positive pressure holding conditions were adopted during the esterification stage, gradient temperature increase was not carried out. Compared with Comparative Example 1 and Comparative Example 2, after the esterification reaction in Examples 1 - 32, the acid value of the system was lower, the water content was lower, and the esterification rate was higher. Thus, it can be known that adopting positive pressure holding conditions and carrying out gradient temperature increase during the esterification stage can avoid the generation of pantothenic acid phenomenon and is beneficial to reducing the reaction time. At the same time, compared with the products of Comparative Example 1 and Comparative Example 2, the reaction products of Examples 1 - 32 have lower chromaticity and lower water content, which is more conducive to the application of the product dimer acid polyester polyol in the polyurethane industry.

[0084] The chromaticity of the product in Comparative Example 3 is relatively high because the purity of the raw materials in Comparative Example 3 is relatively low. Compared with other examples, the chromaticity of the product in Example 7 is relatively high because no stabilizer was added during the reaction process in Example 7, and a part of the raw materials may have been oxidized during the reaction process.

[0085] During the reaction of dimer acid and polyol, samples are taken at certain time intervals to measure the acid value of the materials in the reaction system at the current time point, and the reaction progress is judged by the change of the acid value. The change of the acid value (unit: mgKOH / g) of the materials in each example and comparative example during the reaction process is recorded in Table 3.

[0086] Table 3

[0087]

[0088] Samples are taken when the reaction temperature of the system rises to the first temperature (corresponding to Sample 1, and the subsequent samples are numbered Sample 2, Sample 3, etc. in sequence). In addition, samples are taken for testing after the end of each heat preservation stage of the esterification reaction, during the vacuum polycondensation stage, after the end of each pressure holding stage before the last pressure holding stage, and samples are taken for testing every 1.5 h during the last pressure holding stage.

[0089] It should be noted that in Comparative Example 3, due to the lower purity of the dimer acid raw material, the reaction time is longer and the hydroxyl value is lower compared with the examples.

[0090] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Additionally, it should be noted that in this specification, the terms "first", "second", "third", "fourth", "fifth", "sixth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0091] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a dimer acid polyester polyol, characterized in that, Comprising: (1) Placing the dimer acid and the polyol in a reaction vessel; (2) Under positive pressure conditions, increasing the temperature in a gradient manner to cause the dimer acid and the polyol to undergo an esterification reaction, wherein the pressure of the positive pressure conditions is 0.05 MPa to 0.9 MPa, and the gradient temperature increase includes at least two heat preservation stages; (3) Performing a polycondensation reaction under negative pressure conditions to obtain a dimer acid polyester polyol.

2. The method according to claim 1, wherein Satisfying at least one of the following conditions: The purity of the dimer acid ≥ 70%; The dimer acid includes hydrogenated dimer acid; The polyol includes one or more of 1,4 - butanediol, 1,6 - hexanediol, 2 - methyl - 1,3 - propanediol, ethylene glycol, 1,2 - propanediol, 1,3 - propanediol, neopentyl glycol, diethylene glycol, 1,5 - pentanediol; The molar ratio of the dimer acid to the polyol is 1:(1 - 2); Before the gradient temperature increase, replacing the air in the reaction vessel with nitrogen and making the pressure in the reaction vessel positive pressure.

3. The method according to claim 1, wherein In step (2), the pressure of the positive pressure conditions is 0.2 MPa to 0.8 MPa.

4. The method according to claim 1, characterized in that The gradient temperature increase includes the following steps: Heating to 170°C to 190°C, heat preserving for 1 h to 4 h, then continuing to heat to 200°C to 220°C, and heat preserving for 1 h to 4 h.

5. The method according to claim 1, characterized in that The gradient temperature increase includes the following steps: (2 - 1) Heating to the first temperature and heat preserving for the first time, the first temperature is 140°C to 160°C, and the first time is 0.5 h to 2 h; (2 - 2) Heating to the second temperature and heat preserving for the second time, the second temperature is 170°C to 190°C, and the second time is 1 h to 4 h; (2 - 3) Heating to the third temperature and heat preserving for the third time, the third temperature is 200°C to 220°C, and the third time is 1 h to 4 h.

6. The method according to any one of claims 1 to 5, characterized in that The polycondensation reaction under negative pressure conditions is carried out in a gradient pressure reduction manner, including at least two pressure holding stages.

7. The method according to claim 1, characterized in that, The polycondensation reaction under negative pressure conditions includes the following steps: (3 - 1) Reducing the pressure to the first pressure and holding the pressure for the fourth time, the first pressure is -0.06 MPa to -0.04 MPa, and the fourth time is 0.5 h to 2 h; (3 - 2) Reducing the pressure to the second pressure and holding the pressure for the fifth time, the second pressure is -0.08 MPa to -0.07 MPa, and the fifth time is 1 h to 5 h; (3 - 3) Reducing the pressure to the third pressure and holding the pressure for the sixth time, the third pressure is -0.1 MPa to -0.09 MPa, and the sixth time is 1 h to 5 h.

8. The method according to any one of claims 1 to 5 and 7, characterized in that After the esterification reaction is completed and before the polycondensation reaction is carried out under negative pressure conditions, the method further includes: adjusting the pressure in the reaction vessel to normal pressure, introducing nitrogen, adding a stabilizer to the reaction vessel, heat preserving for 20 - 40 min, and then adding a catalyst to the reaction vessel and heat preserving for 20 - 40 min.

9. The method according to claim 8, characterized in that, Satisfying at least one of the following conditions: The stabilizer includes one or more of triphenyl phosphate, triethyl phosphate, triethyl methylphosphonate, triphenyl phosphite, tris(2,4 - di - tert - butylphenyl) phosphite, distearyl pentaerythritol diphosphite; The molar ratio of the dimer acid to the stabilizer is 100:(0.004 - 0.04); The catalyst includes one or more of stannous octoate, stannous oxalate, p-toluenesulfonic acid, tetrabutyl titanate, stannous chloride, dibutyltin dilaurate; The molar ratio of the dimer acid to the catalyst is 100:(0.01 - 0.04).

10. A dimer acid polyester polyol, characterized in that, The dimer acid polyester polyol is prepared by the method described in any one of claims 1 - 9, and the acid value of the dimer acid polyester polyol is 0.1 mgKOH / g - 2 mgKOH / g, the hydroxyl value is 55 mgKOH / g - 90 mgKOH / g, the water content is ≤0.1%, and the Gardner color number is 1 - 9.

11. Use of the dimer acid polyester polyol according to claim 10 in the synthesis of polyurethane.

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