A liquid polyester polyol and preparation method thereof

Abstract

The present invention discloses a liquid polyester polyol and a preparation method thereof. The method comprises: adding lactone, polyol, dibasic acid or anhydride, and a catalyst to a reactor under the protection of an inert atmosphere, reacting at 100 to 160° C. to obtain a liquid polyester polyol; or, adding lactone, polyol, dibasic acid or anhydride, a catalyst, and a solvent to a reactor under the protection of an inert atmosphere, reacting at 100 to 160° C., and removing the solvent to obtain a liquid polyester polyol; wherein the catalyst is (2-hydroxybenzyl) diarylphosphine oxide. The key to the present invention is the dual catalytic effect of (2-hydroxybenzyl) diarylphosphine oxide on polycondensation and ring-opening polymerization, so that polycondensation and ring-opening polymerization are carried out simultaneously. In addition, the innovation of the method is that a certain amount of dibasic acid structural units are introduced into the easily crystallized polylactone chain through polycondensation to destroy the crystallization of the polylactone chain, thereby obtaining a liquid polyester polyol that is convenient for industrial application.

Description

Technical Field

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

[0002] Polyester polyols are one of the main raw materials for polyester polyurethanes. They can be divided into aliphatic polyols and aromatic polyols according to whether they contain benzene rings. Among them, aliphatic polyols are mainly adipic acid-based polyester diols. Polyester polyols include conventional polyester polyols and polylactone polyols, which contain ester groups or carbonate groups. The polyester polyols usually referred to are polyester polyols obtained by polycondensation reactions of dicarboxylic acids and diols. The preparation of polyester polyols generally adopts an intermittent synthesis method, which mainly includes two polycondensation stages. In the first stage, small molecule polyols (such as ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, etc.) are reacted with dibasic acids (terephthalic acid, adipic acid, etc.) or acid anhydrides (phthalic anhydride, etc.) at 140-200°C in the presence of a catalyst (generally one or more of titanium, tin, bismuth, zirconium, and antimony). The top temperature of the distillation tower is controlled at 100-102°C. After most of the by-product water generated is distilled off at normal pressure, the temperature is maintained at 200-230°C for 1-2 hours. At this time, the acid value is generally reduced to 20-30 mg KOH / g. In the second stage, vacuum is drawn and the vacuum degree is gradually increased. Trace amounts of water and excess diol compounds are removed by decompression to allow the reaction to proceed in the direction of generating low-acid polyester polyols. Inert gases such as nitrogen can also be continuously introduced to remove water. Azeotropic solvents such as toluene can also be added to the reaction system, and the generated water can be slowly removed with a water separator when the toluene refluxes. The structural units in the polymer chain can be well controlled by synthesizing polyester polyols through polycondensation, so that the properties (liquid or solid) and properties of the resulting products can be easily adjusted. However, due to the difficulty in accurately controlling the degree of reactivity in the polycondensation process, this method usually results in differences in various parameters such as hydroxyl value, acid value, moisture, viscosity, and molecular weight in different batches of products. In the downstream polyurethane synthesis process, these parameters must be measured each time, which is very cumbersome.

[0003] In contrast, polylactone polyols are obtained by ring-opening polymerization of lactone monomers with small molecule polyols (such as ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, etc.) as initiators under the action of metal or organic catalysts. Because ring-opening polymerization is a chain-type active polymerization, the various parameters of the obtained polylactone polyols, such as hydroxyl value, acid value, moisture, viscosity, molecular weight and molecular weight distribution, can be precisely controlled. However, due to the large differences in the reactivity between different lactones, it becomes difficult to adjust the structural units in polylactone polyols by copolymerizing different monomers. Usually, the polylactone polyols obtained by ring-opening polymerization are solid and must be heated when taken out of the container, which is time-consuming and energy-consuming and increases the pretreatment cost. In summary, it is of great practical significance to develop a preparation method that can precisely control the properties and characteristics of polyester polyols at the same time. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a liquid polyester polyol and a preparation method thereof, aiming to solve the problem that the polyester polyol prepared by the existing ring-opening polymerization method is in a solid state and must be heated when taken out of the container, which is time-consuming and energy-consuming and increases the pretreatment cost.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a liquid polyester polyol, comprising the steps of:

[0007] Under the protection of an inert atmosphere, lactone, polyol, dibasic acid or anhydride, and a catalyst are added to a reactor, and the reaction is carried out at 100 to 160° C. to obtain a liquid polyester polyol;

[0008] Alternatively, under the protection of an inert atmosphere, lactone, polyol, dibasic acid or anhydride, catalyst, and solvent are added to a reactor, and the reaction is carried out at 100 to 160° C. to obtain a liquid polyester polyol;

[0009] Wherein, the catalyst is (2-hydroxybenzyl) diaryl phosphine oxide, and the structural formula of the (2-hydroxybenzyl) diaryl phosphine oxide is as follows:

[0010] Ar represents an aromatic ring or a substituted aromatic ring.

[0011] Optionally, the catalyst is (2-hydroxybenzyl)diphenylphosphine oxide.

[0012] Optionally, the lactone is one or more of β-butyrolactone, δ-valerolactone, ε-caprolactone, carbonate, and lactide.

[0013] Optionally, the polyol is one or more of ethylene glycol, propylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, PTMEG diol, PEO diol, glycerol, pentaerythritol, PTMEG polyol, and PEO polyol.

[0014] Optionally, the dibasic acid is an aliphatic dibasic acid or an aromatic dibasic acid.

[0015] Optionally, the solvent is one or more of benzene, toluene and xylene.

[0016] Optionally, the molar ratio of the lactone, the polyol and the dibasic acid is (3-30):1:(0.4-0.7);

[0017] Alternatively, the molar ratio of the lactone, the polyol and the acid anhydride is (3-30):1:(0.4-0.7).

[0018] Optionally, the mass ratio of the catalyst to the lactone is (1-5):100.

[0019] Optionally, the reactor is a reaction kettle with a fractionation device, and during the reaction at 100-160°C, the top temperature of the fractionation device is controlled within the range of 100-102°C; after the step of reacting at 100-160°C is completed, the step further includes: controlling the top temperature of the fractionation device within the range of 135-140°C.

[0020] A liquid polyester polyol is prepared by the method described in the present invention.

[0021] Beneficial effects: The present invention provides a method for preparing a liquid polyester polyol, specifically a new method and an organic catalyst system for preparing a liquid polyester polyol by combining polycondensation with ring-opening polymerization, wherein various parameters such as hydroxyl value, acid value, water content, viscosity, molecular weight and molecular weight distribution can be accurately controlled. In the present invention, solution or bulk polymerization is adopted, (2-hydroxybenzyl) diarylphosphine oxide is used as a catalyst, small molecule polyols (such as ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, etc.) are used as initiators, lactone is used as a ring-opening monomer, dibasic acid or anhydride is used as a condensation monomer, polycondensation is combined with ring-opening polymerization, and liquid polyester polyol is synthesized at a high conversion rate at 100 to 160°C and under the protection of an inert atmosphere. This synthesis method is efficient, simple in process, and has a high conversion rate of lactone monomers. The synthesized liquid polyester polyol has the characteristics of good yellowing resistance and hydrolysis resistance, and can overcome the disadvantage that traditional process products are easy to age under the residual metal catalyst. It is a new method for preparing liquid polyester polyol in a green and efficient manner. The liquid polyester polyol prepared by the present invention does not have the problems of product aging and biological toxicity caused by catalyst residues, and is particularly suitable for preparing polyurethane materials for use in the medical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a general reaction formula diagram for preparing liquid polyester polyols based on the embodiment of the present invention, which uses (2-hydroxybenzyl) diarylphosphine oxide as a catalyst, a polyol as an initiator, a lactone as a ring-opening monomer, and a dibasic acid or anhydride as a condensation monomer, combined with polycondensation and ring-opening polymerization. DETAILED DESCRIPTION

[0023] The present invention provides a liquid polyester polyol and a preparation method thereof. To make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] The embodiment of the present invention provides a method for preparing a liquid polyester polyol, which comprises the steps of:

[0025] Under the protection of an inert atmosphere, lactone, polyol, dibasic acid or anhydride, and a catalyst are added to a reactor, and the reaction is carried out at 100 to 160° C. to obtain a liquid polyester polyol;

[0026] Alternatively, under the protection of an inert atmosphere, lactone, polyol, dibasic acid or anhydride, catalyst, and solvent are added to a reactor, and the reaction is carried out at 100 to 160° C. to obtain a liquid polyester polyol;

[0027] Wherein, the catalyst is (2-hydroxybenzyl) diaryl phosphine oxide, and the structural formula of the (2-hydroxybenzyl) diaryl phosphine oxide is as follows:

[0028] Ar represents an aromatic ring or a substituted aromatic ring.

[0029] In this embodiment, solution or bulk polymerization is adopted, (2-hydroxybenzyl) diarylphosphine oxide is used as a catalyst, small molecule polyols (such as ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, etc.) are used as initiators, lactone is used as a ring-opening monomer, dibasic acid or anhydride is used as a condensation monomer, polycondensation is combined with ring-opening polymerization, and liquid polyester polyols are synthesized at a high conversion rate under the protection of an inert atmosphere (such as nitrogen or argon, etc.) at 100 to 160°C. The general polymerization reaction formula is as follows: Figure 1 shown.

[0030] The key of the present embodiment is the dual catalytic effect of acidic (2-hydroxybenzyl) diarylphosphine oxide on polycondensation and ring-opening polymerization, so that polycondensation and ring-opening polymerization are carried out simultaneously. In addition, the bright spot of the method is to introduce a certain amount of diacid structural units in the easily crystallized polylactone chain by polycondensation to destroy the crystallization of the polylactone chain, thereby obtaining a liquid polyester polyol that is convenient for industrial application. In addition, the present embodiment overcomes the shortcoming that traditional process products are easily aged under the residual metal catalyst, and is a new method for preparing liquid polyester polyol in a green and efficient manner. The liquid polyester polyol prepared by the present embodiment does not have the product aging and biological toxicity problems caused by the residual metal catalyst, and is particularly suitable for preparing polyurethane materials for medical fields.

[0031] In this embodiment, the reaction of combining polycondensation and ring-opening polymerization using (2-hydroxybenzyl) diarylphosphine oxide as a catalyst, a polyol as an initiator, a lactone as a ring-opening monomer, and a dibasic acid or anhydride as a condensation monomer is carried out in a solution or bulk polymerization manner, involving several components such as a catalyst, an initiator, a lactone, a dibasic acid or anhydride, and a solvent (if necessary).

[0032] In this embodiment, the catalyst is (2-hydroxybenzyl) diarylphosphine oxide, and Ar in the structural formula represents an aromatic ring or a substituted aromatic ring. Further, Ar represents a benzene ring or a benzene ring substituted by a substituent with electron-withdrawing properties such as halogen, trifluoromethyl or nitro. In addition to the (2-hydroxybenzyl) diphenylphosphine oxide in the specific embodiments below, derivatives and analogs with various substituted groups are applicable to this embodiment. Further, the catalyst is (2-hydroxybenzyl) diphenylphosphine oxide.

[0033] In one embodiment, the polyol may be a small molecule dihydric or higher alcohol, such as ethylene glycol, propylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, PTMEG diol, PEO diol, glycerol, pentaerythritol, PTMEG polyol, PEO polyol, etc. One or more.

[0034] In one embodiment, the lactone is one or more of ε-caprolactone (ε-CL), β-butyrolactone (β-BL), δ-valerolactone (δ-VL), etc. In addition, carbonates, lactides, etc. and their derivatives or analogs are applicable to this embodiment.

[0035] In one embodiment, the dibasic acid may be an aliphatic dibasic acid, such as glutaric acid, adipic acid, sebacic acid, and their derivatives, or an aromatic dibasic acid, such as phthalic anhydride, cyclohexanedicarboxylic anhydride, and the like.

[0036] In one embodiment, the molar ratio of the lactone, polyol and dibasic acid is (3-30):1:(0.4-0.7);

[0037] Alternatively, the molar ratio of the lactone, polyol and anhydride is (3-30):1:(0.4-0.7). Within the above range, the molecular weight of the polymer can be controlled between hundreds and thousands, and a non-crystallized polyester polyol product can be obtained.

[0038] In one embodiment, the mass ratio of the catalyst to the lactone is (1-5):100.

[0039] The conditions for carrying out the polymerization reaction in this example are described below.

[0040] The polymerization implementation method of this embodiment can be bulk polymerization or solution polymerization. When bulk polymerization is adopted, the polymerization system only involves lactone monomer, dibasic acid or acid anhydride, (2-hydroxybenzyl) diaryl phosphine oxide and polyol initiator. When solution polymerization is adopted, the reaction system includes lactone monomer, dibasic acid or acid anhydride, (2-hydroxybenzyl) diaryl phosphine oxide, polyol initiator and solvent. The solvent can be selected from azeotropic solvents with water, and benzene, toluene, xylene and the like can be preferably used. When solution polymerization is adopted, the concentration of lactone monomer is preferably 2.0 to 4.0 mol / L.

[0041] In the polymerization reaction, each component is added to the reactor at the beginning of the polymerization to carry out the polymerization reaction.

[0042] In the polymerization reaction of this embodiment, the lactone monomer is quantitatively converted. According to the molar ratio of the monomer and the initiator, that is, the change of the feed ratio, the molecular weight of the polymer can be controlled between hundreds and thousands. The polymerization reaction is completed within several to tens of hours (such as 2 to 20 hours), and the molecular weight distribution can be controlled between 1.1 and 1.6.

[0043] The polymerization reaction described in this embodiment is carried out under an inert gas such as nitrogen or argon, usually nitrogen protection. The reaction temperature can be selected from 100 to 160°C, which can be appropriately selected according to the degree of control of the polymerization, for example, bulk polymerization can be preferably in the range of 150 to 160°C, and solution polymerization can be preferably in the range of 130 to 160°C.

[0044] The reactor of this embodiment can be a reactor with a fractionation device (such as a fractionation tower). During the reaction at 100-160°C, the temperature at the top of the fractionation device is controlled within the range of 100-102°C to remove the moisture generated during the reaction. After the step of reacting at 100-160°C is completed, the step further includes: continuing stirring for 2-6 hours and controlling the temperature at the top of the fractionation device within the range of 135-140°C to continue removing moisture.

[0045] That is to say, the polymerization reaction described in this embodiment involves the use of a fractionation device such as a fractionation tower to remove the moisture generated by the reaction, and a two-stage dehydration operation of first normal pressure and then reduced pressure is adopted. The first stage: under normal pressure, the temperature at the top of the fractionation tower is controlled in the range of 100 to 102°C during the reaction at 100 to 160°C to remove the moisture generated during the reaction; the second stage: under reduced pressure (the reactor is reduced pressure to 100 to 150 mbar), the temperature at the top of the fractionation device is controlled in the range of 135 to 140°C during the reaction process of continuing to stir for 2 to 6 hours to continue to remove moisture and small molecules. When solution polymerization is adopted, the solvent-water mixture can be removed in the first stage, and the solvent, residual moisture and small molecules can be removed in the second stage.

[0046] Determination of monomer conversion, molecular weight and molecular weight distribution in this example:

[0047] The conversion of monomers was determined by nuclear magnetic resonance spectrometry (BRUKER ASCEND™ 400, Bruker Biospin GmbH Rheinstetten, Germany). n ) and molecular weight distribution were determined by gel permeation chromatography (Tosoh HLC-8320GPC) equipped with two TSKgel SuperMultipore HZ-M columns and parallax and UV detectors. The measurement conditions were: measurement temperature, 40°C; flow rate, 0.35 mL·min -1; Mobile phase, THF; Sample concentration, 0.2wt%; Internal standard, styrene standard sample.

[0048] An embodiment of the present invention provides a liquid polyester polyol, wherein the liquid polyester polyol is prepared by the method described in the embodiment of the present invention.

[0049] The present invention will be further described below through several specific embodiments.

[0050] Example 1: Under nitrogen protection, add 228.3g of ε-CL, 41.7g of neopentyl glycol, 29.2g of adipic acid, and 2.3g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 160°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water for 4 hours at 160°C and normal pressure. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 2 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 2,130g / mol, and the molecular weight distribution is 1.26.

[0051] Example 2: Under nitrogen protection, add 228.3g of ε-CL, 41.7g of neopentyl glycol, 11.7g of adipic acid, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 160°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water for 3 hours at 160°C and normal pressure. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 2 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 1,380g / mol, and the molecular weight distribution is 1.32.

[0052] Example 3: Under nitrogen protection, add 228.3g of ε-CL, 69.5g of neopentyl glycol, 48.7g of adipic acid, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 160°C, control the temperature at the top of the fractionation tower at 100-102°C, and continue to evaporate water for 2 hours at 160°C and normal pressure. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the temperature at the top of the fractionation tower at 135-140°C, and continue stirring for 1.5 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 820g / mol, and the molecular weight distribution is 1.58.

[0053] Example 4: Under nitrogen protection, add 228.3g of ε-CL, 10.4g of neopentyl glycol, 7.3g of adipic acid, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 160°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water for 4 hours at 160°C and normal pressure. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 3 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 8,520g / mol, and the molecular weight distribution is 1.33.

[0054] Example 5: Under nitrogen protection, add 228.3g of ε-CL, 58.5g of 2,2,4-trimethyl-1,3-pentanediol, 29.2g of adipic acid, and 2.3g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor with a fractionation device, heat to 160°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water for 4 hours at 160°C and normal pressure. After the viscosity of the system increases, decompress the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 2 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 2,670g / mol, and the molecular weight distribution is 1.30.

[0055] Example 6: Under nitrogen protection, add 228.3g of ε-CL, 41.7g of neopentyl glycol, 59.2g of phthalic anhydride, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 160°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water for 3 hours at 160°C and normal pressure. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 2 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 3,210g / mol, and the molecular weight distribution is 1.43.

[0056] Example 7: Under nitrogen protection, add 228.3g of ε-CL, 41.7g of neopentyl glycol, 40.5g of sebacic acid, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor equipped with a fractionation device, heat to 150°C, control the top temperature of the fractionation tower at 100-102°C, and continue to evaporate water at 150°C and normal pressure for 5 hours. After the viscosity of the system increases, reduce the pressure of the reactor to 100-150mbar, control the top temperature of the fractionation tower at 135-140°C, and continue stirring for 3 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 2,920g / mol, and the molecular weight distribution is 1.35.

[0057] Example 8: Under nitrogen protection, add 200.2g of δ-VL, 57.8g of 1,4-cyclohexanedimethanol, 29.2g of adipic acid, and 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide to a reactor with a fractionation device, heat to 150°C, control the temperature at the top of the fractionation tower at 100-102°C, and continue to evaporate water for 6 hours at 150°C and normal pressure. After the viscosity of the system increases, the reactor is decompressed to 100-150mbar, the temperature at the top of the fractionation tower is controlled at 135-140°C, and stirring is continued for 2 hours to remove water and small molecules. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 3,160g / mol, and the molecular weight distribution is 1.47.

[0058] Example 9: Under nitrogen protection, add 228.3g of ε-CL, 41.7g of neopentyl glycol, 29.2g of adipic acid, 4.6g of (2-hydroxybenzyl) diphenylphosphine oxide, and 500mL of toluene to a reactor equipped with a fractionation device, heat to 140°C, control the temperature at the top of the fractionation tower at 100-102°C, and heat at 140°C and normal pressure for 4 hours to continuously evaporate the toluene-water mixture. After the viscosity of the system increases, decompress the reactor to 100-150mbar, control the temperature at the top of the fractionation tower at 135-140°C, and continue stirring for 2 hours to remove toluene, residual water and small molecular substances. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 2,350g / mol, and the molecular weight distribution is 1.19.

[0059] Example 10: Under nitrogen protection, add 228.3g of ε-CL, 58.5g of 2,2,4-trimethyl-1,3-pentanediol, 59.2g of phthalic anhydride, 5.0g of (2-hydroxybenzyl) diphenylphosphine oxide, and 800mL of xylene to a reactor with a fractionation device, heat to 140°C, control the top temperature of the fractionation tower at 100-102°C, and heat at 140°C and normal pressure for 5 hours to continuously evaporate the xylene-water mixture. After the viscosity of the system increases, the reactor is decompressed to 100-150mbar, the top temperature of the fractionation tower is controlled at 135-140°C, and stirring is continued for 2 hours to remove xylene, residual water and small molecular substances. Cool to obtain a liquid polyester diol product. The number average molecular weight of the product measured by gel permeation chromatography (GPC) in THF solvent is 2,820g / mol, and the molecular weight distribution is 1.22.

[0060] In summary, the present invention provides a liquid polyester polyol and a preparation method thereof, specifically providing a new method and an organic catalyst system for preparing liquid polyester polyols by combining polycondensation with ring-opening polymerization, wherein various parameters such as hydroxyl value, acid value, water content, viscosity, molecular weight and molecular weight distribution can be accurately controlled. In the present invention, solution or bulk polymerization is adopted, (2-hydroxybenzyl) diarylphosphine oxide is used as a catalyst, small molecule polyols (such as ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, etc.) are used as initiators, lactone is a ring-opening monomer, dibasic acid or anhydride is a condensation monomer, polycondensation is combined with ring-opening polymerization, and liquid polyester polyols are synthesized at a high conversion rate at 100 to 160° C. and under the protection of an inert atmosphere. This synthesis method is efficient, simple in process, and has a high conversion rate of lactone monomers. The synthesized liquid polyester polyol has the characteristics of good yellowing resistance and hydrolysis resistance, and can overcome the disadvantage that traditional process products are easy to age under the residual metal catalyst. It is a new method for preparing liquid polyester polyols in a green and efficient manner. The liquid polyester polyol prepared by the present invention does not have the problems of product aging and biological toxicity caused by catalyst residues, and is particularly suitable for preparing polyurethane materials for use in the medical field.

[0061] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a liquid polyester polyol, characterized in that: Includes steps: Under the protection of an inert atmosphere, lactone, polyol, dibasic acid and a catalyst are added into a reactor, and reacted at 100 to 160° C. to obtain a liquid polyester polyol; Alternatively, under the protection of an inert atmosphere, lactone, polyol, dibasic acid, catalyst, and solvent are added to a reactor, and reacted at 100 to 160° C. to obtain a liquid polyester polyol; Wherein, the catalyst is (2-hydroxybenzyl) diaryl phosphine oxide, and the structural formula of the (2-hydroxybenzyl) diaryl phosphine oxide is as follows: Ar represents an aromatic ring or a substituted aromatic ring; The molar ratio of the lactone, the polyol and the dibasic acid is (3-30):1:(0.4-0.7); The lactone is one or more of β-butyrolactone, δ-valerolactone, and ε-caprolactone; The polyol is one or more of ethylene glycol, propylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, trimethylolpropane, pentaerythritol, 1,4-butanediol, glycerol, PTMEG polyol, and PEO polyol; The dibasic acid is glutaric acid, glutaric acid derivatives, adipic acid, adipic acid derivatives, sebacic acid, sebacic acid derivatives, phthalic anhydride, cyclohexanedicarboxylic anhydride; The mass ratio of the catalyst to the lactone is (1-5):

100.

2. The method for preparing a liquid polyester polyol according to claim 1, characterized in that: The catalyst is (2-hydroxybenzyl)diphenylphosphine oxide.

3. The method for preparing a liquid polyester polyol according to claim 1, characterized in that: The solvent is one or more of benzene, toluene and xylene.

4. The method for preparing a liquid polyester polyol according to claim 1, characterized in that: The reactor is a reaction kettle with a fractionation device. During the reaction at 100-160°C, the top temperature of the fractionation device is controlled within the range of 100-102°C. After the step of reacting at 100-160°C is completed, the step further includes: controlling the top temperature of the fractionation device within the range of 135-140°C.

5. A liquid polyester polyol, characterized in that: The method is prepared by any one of claims 1 to 4.

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