A polyester polyol, its preparation and use

Abstract

The application provides a preparation method of polyester polyol, comprising the following steps: a) under inert gas protection, fatty acid ester, small molecule dihydric alcohol, small molecule diacid, catalyst A and stabilizer are added into a reaction kettle to perform esterification reaction, byproducts are removed by inert gas replacement during the reaction, after the acid value is less than 20 mg KOH / g, the byproducts are removed by continuous vacuum extraction, after the acid value is less than 2 mg KOH / g, an intermediate polyester polyol is obtained; b) under inert gas protection, the intermediate polyester polyol is added into the reaction kettle to perform ring-opening polymerization reaction with the addition of epoxide, acid anhydride and catalyst B, after the reaction is completed, unreacted epoxide and small molecule byproducts are removed by continuous vacuum extraction, and the polyester polyol is obtained after cooling. The preparation method adopts specific raw materials, specific process steps, conditions and parameters, realizes good overall interaction, and can prepare polyester polyols with various structures and narrow molecular weight distribution.

Description

Technical Field

[0001] This invention relates to the field of polyester polyol technology, and more specifically, to a polyester polyol, its preparation method, and its application. Background Technology

[0002] Polyester polyols have a high density of polar groups in their molecules, resulting in high cohesive strength, making them an important raw material for the synthesis of polyester-type polyurethanes. Polyurethane hot melt adhesives are a type of hot melt adhesive made primarily of polyurethane prepolymers, combined with various additives (such as catalysts, antioxidants, tackifiers, and fillers). Because they contain highly polar and chemically reactive isocyanate groups (-NCO) and urethane groups (-NHCOO-), they exhibit excellent chemical adhesion to various materials. Furthermore, the hydrogen bonding between the polyurethane and the bonded materials increases the polymeric cohesive force, thus strengthening the bond.

[0003] Currently, there are three main methods for synthesizing polyester polyols. First, the condensation polymerization of diols with diacids or diesters uses relatively inexpensive raw materials and is a traditional method for synthesizing polyester polyols. Second, ring-opening polymerization of lactones is an atom-economical synthetic route, but the cost of lactone monomers is relatively high, and the types of monomers available are limited. Third, ring-opening copolymerization of epoxides and cyclic anhydrides is not only atom-economical, but also uses a variety of epoxides and cyclic anhydrides, which are widely available and can produce polyester polyols with different structures. However, the polyester polyols prepared by these methods mostly have a wide molecular weight distribution and poor processing stability, resulting in poor performance of the final products made from polyester polyols, which cannot meet the needs of downstream applications. Summary of the Invention

[0004] In view of this, in order to expand the variety and specifications of polyester polyols, this invention combines the advantages of different preparation methods to make up for the shortcomings of a single preparation method, and prepares polyester polyols with richer structures and narrower molecular weight distribution.

[0005] This invention provides a method for preparing polyester polyols, comprising the following steps:

[0006] a) Under inert gas protection, fatty acid ester, small molecule diol, small molecule dicarboxylic acid, catalyst A and stabilizer are added to the reaction vessel to carry out esterification reaction. During the reaction, byproducts are removed by inert gas replacement. After the acid value is less than 20 mg KOH / g, byproducts are removed by continuous vacuuming. After the acid value is less than 2 mg KOH / g, intermediate polyester polyol is obtained.

[0007] b) Under inert gas protection, epoxide, acid anhydride and catalyst B are added to a reactor containing intermediate polyester polyol to carry out ring-opening polymerization. After the reaction is completed, unreacted epoxide and small molecule byproducts are removed by continuous vacuuming, and polyester polyol is obtained after cooling.

[0008] Preferably, the fatty acid esters mentioned in step a) are selected from one or more of castor oil, cottonseed oil, peanut oil, coconut oil, flaxseed oil, palm kernel oil, olive oil, corn oil, palm oil, jatropha oil, rapeseed oil, soybean oil, sunflower oil, herring oil, sardine oil, and tallow;

[0009] The small molecule diol is selected from one or more of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, 1,16-hexadecanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, nonaethylene glycol, hexaethylene glycol, and dodecaethylene glycol.

[0010] The small molecule dicarboxylic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, terephthalic acid, phthalic acid, isophthalic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedioic acid, and 1,16-hexadecanedicarboxylic acid;

[0011] The catalyst A is selected from one or more of the following: isopropyl titanate, n-butyl titanate, titanium glycolate, antimony trioxide, antimony acetate, antimony glycolate, germanium dioxide, stannous octoate, stannous chloride, dibutyltin dilaurate, and phosphotungstic acid.

[0012] The stabilizer is selected from one or more of hydroquinone, p-hydroxyanisole, 2,5-di-tert-butylhydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, methylhydroquinone, and 2,2,6,6-tetramethyl-4-hydroxypiperidine nitroxide radical.

[0013] Preferably, in step a), the mass ratio of fatty acid ester, small molecule diol, and small molecule diacid is (40-60):(10-30):(25-35); the amount of catalyst A is 5 ppm to 500 ppm of the total mass of the small molecule diol and the small molecule diacid; and the amount of stabilizer added is 0.02% to 1.5% of the mass of the small molecule diacid.

[0014] Preferably, the esterification reaction in step a) is carried out using a stepwise temperature increase:

[0015] First, raise the temperature to 130℃~150℃ and hold for 1h~2h; then raise the temperature to 170℃~190℃ and hold for 1h~3h; finally, continue to raise the temperature to 210℃~230℃ and hold for 1h~3h.

[0016] Preferably, the vacuum degree of the reactor is controlled to be -0.005 to -0.01 MPa during the continuous vacuuming process in step a).

[0017] Preferably, the epoxide in step b) is selected from one or more of ethylene oxide, propylene oxide, 1,2-epoxybutane, 1,2-epoxyhexane, C5-C20 α-olefin oxide, methyl epidecenoate, cyclohexene oxide, styrene oxide, epichlorohydrin, allyl glycidyl ether, n-butyl glycidyl ether, furfuryl glycidyl ether, phenyl glycidyl ether, and butyl glycidyl ether.

[0018] The anhydride is selected from one or more of the following: phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, 2,3-dichloromaleic anhydride, trifluoromethylmaleic anhydride, bromomaleic anhydride, 2,3-dibromomaleic anhydride, phenylmaleic anhydride, citraconic anhydride, itaconic anhydride, cis-5-norbornen-ex-2,3-dicarboxylic anhydride, and bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic anhydride;

[0019] The catalyst B is selected from one or more of the following: zinc-cobalt bimetallic cyanide complex, indium-cobalt bimetallic cyanide complex, zinc-iron bimetallic cyanide complex, nickel-cobalt bimetallic cyanide complex, zinc-cobalt bimetallic cyanide complex supported on a support, indium-cobalt bimetallic cyanide complex supported on a support, zinc-iron bimetallic cyanide complex supported on a support, and nickel-cobalt bimetallic cyanide complex supported on a support.

[0020] Preferably, the molar ratio of the anhydride to the epoxide in step b) is 1:(1-10); the amount of catalyst B is 100ppm to 500ppm of the total mass of the anhydride and the epoxide.

[0021] Preferably, the ring-opening polymerization reaction in step b) is carried out at a temperature of 20°C to 150°C, at a pressure equal to the autogenous pressure of the reaction, and for a time of 5 h to 24 h.

[0022] The present invention also provides a novel polyester polyol, which is prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides an application of polyester polyol in the preparation of polyurethane adhesives, wherein the polyester polyol is the novel polyester polyol described in the above technical solution.

[0024] This invention provides a polyester polyol, its preparation method, and its application. The preparation method includes the following steps: a) Under inert gas protection, fatty acid esters, small molecule diols, small molecule diacids, catalyst A, and stabilizers are added to a reaction vessel for esterification. During the reaction, byproducts are removed by inert gas displacement. After the acid value is less than 20 mg KOH / g, byproducts are removed by continuous vacuuming. After the acid value is less than 2 mg KOH / g, intermediate polyester polyol is obtained; b) Under inert gas protection, epoxides, acid anhydrides, and catalyst B are added to the reaction vessel containing the intermediate polyester polyol for ring-opening polymerization. After the reaction, unreacted epoxides and small molecule byproducts are removed by continuous vacuuming, and the polyester polyol is obtained after cooling. Compared with the prior art, the preparation method provided by this invention uses specific raw materials combined with specific process steps, conditions, and parameters to achieve better overall interaction, and can produce a variety of polyester polyols with different structures and narrow molecular weight distribution. At the same time, the preparation method is simple and easy to implement, requires no modification to the reaction device or equipment, saves energy and reduces emissions, is economical and environmentally friendly, and is suitable for large-scale industrial production.

[0025] Meanwhile, the preparation method provided by this invention combines the advantages of the polycondensation reaction of diols and diacids and the ring-opening reaction of epoxides and cyclic anhydrides. It has a wide variety of monomers available, is widely sourced and has low cost. It is not only atom-economical, but also has a wide variety of epoxides and cyclic anhydrides. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a method for preparing polyester polyols, comprising the following steps:

[0028] a) Under inert gas protection, fatty acid ester, small molecule diol, small molecule diacid, catalyst A and stabilizer are added to the reaction vessel and heated to 130℃~230℃ for esterification reaction. During the reaction, byproducts are removed by inert gas displacement. After the acid value is less than 20mg KOH / g, byproducts are removed by continuous vacuuming. After the acid value is less than 2mg KOH / g, intermediate polyester polyol is obtained.

[0029] b) Under inert gas protection, epoxide, acid anhydride and catalyst B are added to a reactor containing intermediate polyester polyol to carry out ring-opening polymerization. After the reaction is completed, unreacted epoxide and small molecule byproducts are removed by continuous vacuuming, and polyester polyol is obtained after cooling.

[0030] In this invention, fatty acid esters, small molecule diols, small molecule diacids, catalyst A, and stabilizers are first added to a reaction vessel under inert gas protection to carry out an esterification reaction. During the reaction, byproducts are removed by inert gas displacement (specifically, byproducts are removed by inert gas purging). When the acid value is less than 20 mg KOH / g, a vacuum is opened, and byproducts are removed by continuous vacuuming. When the acid value is less than 2 mg KOH / g, the intermediate polyester polyol is obtained.

[0031] To prevent the adverse effects of oxygen in the air during the polymerization process, an inert gas atmosphere is required. There are no particular limitations as long as it does not hinder the reaction. For example, a nitrogen atmosphere, argon atmosphere, or other inert gas atmosphere are preferred. This invention does not have any special limitations in this regard.

[0032] The preparation method provided by this invention has good versatility and is applicable to a variety of monomers.

[0033] In this invention, the fatty acid ester is preferably selected from one or more of castor oil, cottonseed oil, peanut oil, coconut oil, flaxseed oil, palm kernel oil, olive oil, corn oil, palm oil, jatropha oil, rapeseed oil, soybean oil, sunflower oil, herring oil, sardine oil, and tallow, and more preferably from at least one of castor oil, cottonseed oil, palm oil, and sunflower oil. This invention does not impose any special restrictions on the source of the fatty acid ester, and commercially available products well known to those skilled in the art can be used.

[0034] Through experiments, this invention has found that the above-mentioned fatty acid ester has a hydrophobic structure, and its introduction can improve the high temperature resistance, alkali resistance, wash resistance, and corrosion resistance of polyester polyols. At the same time, the glass transition temperature of the product is relatively low.

[0035] In this invention, the small molecule diol is preferably selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, 1,16-hexadecanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 2,4-diethyl-1,5-pentanediol, and 2,2,4-trimethyl-1,3-pentanediol. One or more of the following: diol, nonaethylene glycol, hexaethylene glycol, and dodecaethylene glycol; more preferably, at least one of the following: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, and 1,16-hexadecanediol; the present invention does not impose any special restrictions on the source of the small molecule diols, and commercially available products well known to those skilled in the art can be used.

[0036] In this invention, the small molecule dicarboxylic acid is preferably selected from one or more of succinic acid, glutaric acid, adipic acid, terephthalic acid, phthalic acid, isophthalic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedioic acid, and 1,16-hexadecanedicarboxylic acid, more preferably at least one of succinic acid, glutaric acid, adipic acid, terephthalic acid, phthalic acid, and isophthalic acid; this invention does not impose any special restrictions on the source of the small molecule dicarboxylic acid, and commercially available products well known to those skilled in the art can be used.

[0037] In this invention, catalyst A is preferably selected from one or more of isopropyl titanate, n-butyl titanate, titanium glycolate, antimony trioxide, antimony acetate, antimony glycolate, germanium dioxide, stannous octoate, stannous chloride, dibutyltin dilaurate, and phosphotungstic acid, more preferably from at least one of isopropyl titanate, n-butyl titanate, stannous octoate, stannous chloride, and dibutyltin dilaurate; this invention does not impose any special restrictions on the source of catalyst A, and commercially available products well known to those skilled in the art can be used.

[0038] The present invention has found through experiments that residual catalyst affects the preparation of downstream polyurethane. Therefore, for specific polyurethane material preparation fields, the above-mentioned suitable catalyst should be selected.

[0039] In this invention, the stabilizer is preferably selected from one or more of hydroquinone, p-hydroxyanisole, 2,5-di-tert-butylhydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, methylhydroquinone, and 2,2,6,6-tetramethyl-4-hydroxypiperidine nitroxide radical, more preferably p-benzoquinone, methylhydroquinone, hydroquinone, or 2-tert-butylhydroquinone. This invention does not impose any special restrictions on the source of the stabilizer; commercially available products well known to those skilled in the art can be used.

[0040] In this invention, the addition of the above-mentioned specific type of stabilizer can improve the stability of the material at high temperatures, thereby increasing the reaction temperature, shortening the reaction time, and preventing the product from being dull in color.

[0041] In this invention, the preferred mass ratio of the fatty acid ester, small molecule diol, and small molecule diacid is (40-60):(10-30):(25-35); the preferred amount of catalyst A is 5 ppm to 500 ppm of the total mass of the small molecule diol and the small molecule diacid; and the preferred amount of stabilizer is 0.02% to 1.5% of the mass of the small molecule diacid. Experiments have shown that when the amount of catalyst A exceeds the above range, it is difficult to obtain polyester polyols with a narrow molecular weight distribution, and the residue of catalyst A will affect the overall performance of downstream polyurethane products.

[0042] The present invention does not impose any special restrictions on the reactor, and any reactor capable of carrying out polymerization reactions, such as batch, semi-batch, or continuous reactors, which are well known to those skilled in the art, can be used.

[0043] In this invention, to ensure the rapid and complete progress of the reaction, the esterification reaction process preferably employs a step-by-step heating method:

[0044] First, raise the temperature to 130℃~150℃ and hold for 1h~2h; then raise the temperature to 170℃~190℃ and hold for 1h~3h; finally, continue to raise the temperature to 210℃~230℃ and hold for 1h~3h.

[0045] Through experiments, this invention has found that when the reaction temperature is too low, the reaction rate will slow down. However, when the reaction temperature is too high, coloring caused by transesterification and decomposition of the generated polymer will occur, making it difficult to obtain colorless, transparent polyester polyols with a narrow molecular weight distribution.

[0046] During the reaction, byproducts are removed by inert gas displacement (specifically, byert gas purging). Once the acid value is less than 20 mg KOH / g, a vacuum is applied, and byproducts are removed by continuous vacuuming until the acid value is less than 2 mg KOH / g, yielding the intermediate polyester polyol. When the vacuum is applied, it is preferably slowly reduced to a vacuum level of -0.005 MPa to -0.01 MPa over 0.5 to 2 hours. Experiments have shown that excessively rapid increases in vacuum can cause the release of small-molecule diols or oligomers, resulting in raw material waste.

[0047] In this invention, the vacuum degree of the continuously evacuated process control reactor is preferably -0.005MPa to -0.01MPa.

[0048] After obtaining the intermediate polyester polyol, the present invention adds epoxide, acid anhydride and catalyst B to a reaction vessel containing the intermediate polyester polyol under inert gas protection to carry out a ring-opening polymerization reaction. After the reaction is completed, unreacted epoxide and small molecule byproducts are removed by continuous vacuuming, and the polyester polyol is obtained after cooling.

[0049] In this invention, the limitation under inert gas protection is the same as in the above-described technical solution, and will not be repeated here.

[0050] In this invention, the epoxide is preferably selected from one or more of ethylene oxide, propylene oxide, 1,2-epoxybutane, 1,2-epoxyhexane, C5-C20 α-olefin oxide, methyl epidecenoate, cyclohexene oxide, styrene oxide, epichlorohydrin, allyl glycidyl ether, n-butyl glycidyl ether, furfuryl glycidyl ether, phenyl glycidyl ether, and butyl glycidyl ether, more preferably at least one of ethylene oxide, propylene oxide, and cyclohexene oxide; this invention does not have any special restrictions on the source of the epoxide, and commercially available products well known to those skilled in the art can be used.

[0051] In this invention, the anhydride is preferably selected from one or more of phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, 2,3-dichloromaleic anhydride, trifluoromethylmaleic anhydride, bromomaleic anhydride, 2,3-dibromomaleic anhydride, phenylmaleic anhydride, citraconic anhydride, itaconic anhydride, cis-5-norbornene-ex-2,3-dicarboxylic anhydride, and bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic anhydride, more preferably at least one of phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, and maleic anhydride; this invention does not impose any special restrictions on the source of the anhydride, and commercially available products well known to those skilled in the art can be used.

[0052] In this invention, catalyst B is preferably selected from one or more of the following: zinc-cobalt bimetallic cyanide complex, indium-cobalt bimetallic cyanide complex, zinc-iron bimetallic cyanide complex, nickel-cobalt bimetallic cyanide complex, supported zinc-cobalt bimetallic cyanide complex, supported indium-cobalt bimetallic cyanide complex, supported zinc-iron bimetallic cyanide complex, and supported nickel-cobalt bimetallic cyanide complex. In this invention, the preparation of the zinc-cobalt bimetallic cyanide complex can refer to the synthesis method described by Sun Xueke et al. in "Alternating Copolymerization of CarbonDioxide and Cyclohexene Oxide Catalyzed by Silicon Dioxide / Zn-CoIII Double Metal Cyanide Complex HybridCatalysts with a Nanolamellar Structure" (J. Polym. Sci. Part. A: Polym. Chem., 2008, 46, 3128); the synthesis methods of other bimetallic catalysts can all refer to the preparation method of zinc-cobalt bimetallic cyanide complex. Through experiments, this invention has found that the bimetallic cyanide complex prepared by the above process has a polycrystalline nanosheet structure; the catalyst with this nanostructure has a larger specific surface area and exhibits better catalytic activity in the system.

[0053] In this invention, the molar ratio of the acid anhydride to the epoxide is preferably 1:(1-10), more preferably 1:(3-6); the amount of catalyst B is preferably 100ppm to 500ppm of the total mass of the acid anhydride and epoxide, more preferably 150ppm to 350ppm of the total mass of the acid anhydride and epoxide. Experiments have shown that when the amount of catalyst B exceeds the above range, it is also difficult to obtain polyester polyols with a narrow molecular weight distribution. Furthermore, the residue of catalyst B limits the application of polyester polyols in downstream low-heavy-metal content applications.

[0054] In this invention, the temperature of the ring-opening polymerization reaction is preferably 20℃~150℃, more preferably 80℃~100℃, the pressure is preferably the reaction self-generated pressure, and the time is preferably 5h~24h, more preferably 10h~12h.

[0055] In this invention, during the ring-opening polymerization reaction, a vacuum is activated to remove unreacted epoxides and small molecule byproducts. The unreacted epoxides can also act as a solvent in the system, reducing the viscosity of the system. The reaction continues until the hydroxyl value and acid value reach the designed values ​​to obtain the target product. After cooling to below 80°C, the material is discharged to obtain the novel polyester polyol.

[0056] In this invention, after the reaction is completed, the reaction products can be separated and purified by methods such as filtration, distillation, crystallization, recrystallization, adsorption, column chromatography, or a combination of these methods. This invention does not have any particular limitations on this.

[0057] The preparation method provided by this invention utilizes specific raw materials combined with specific process steps, conditions, and parameters to achieve a good overall interaction. First, an intermediate polyester polyol is obtained through the esterification reaction of fatty acid ester, small molecule diol, small molecule diacid, catalyst A, and stabilizer. Then, a novel polyester polyol is obtained through the ring-opening polymerization reaction of epoxide, acid anhydride, and catalyst B. This method can produce a variety of polyester polyols with different structures and narrow molecular weight distributions. Furthermore, the preparation method is simple and easy to implement, requiring no modification to the reaction apparatus or equipment, saving energy and reducing emissions, and is economical and environmentally friendly, making it suitable for large-scale industrial production. In addition, the preparation method provided by this invention combines the advantages of the condensation reaction of diol and diacid and the ring-opening reaction of epoxide and cyclic anhydride, allowing for a wide variety of monomers with broad sources and low cost. It not only has atom economy but also offers a variety of epoxides and cyclic anhydrides.

[0058] The present invention also provides a novel polyester polyol, which is prepared by the preparation method described in the above technical solution.

[0059] In this invention, the acid value of the novel polyester polyol is preferably ≤10mg KOH / g, more preferably ≤5mg KOH / g, the hydroxyl value is preferably 20-200mg KOH / g, more preferably 30-170mg KOH / g, and the molecular weight distribution is preferably 1.05-1.4, more preferably 1.1-1.25.

[0060] The present invention also provides an application of polyester polyol in the preparation of polyurethane adhesives, wherein the polyester polyol is the novel polyester polyol described in the above technical solution.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) The preparation method of polyester polyol provided by the present invention is simple, safe and environmentally friendly, and the process steps are easy to operate. It can obtain a new type of polyester polyol with controllable hydroxyl value, viscosity and narrow molecular weight distribution on the basis of high feasibility of the scheme.

[0063] (2) The catalyst used in this invention is a commonly used homogeneous or heterogeneous catalyst in industry, which is relatively inexpensive; the prepared polyester has excellent color and is a white or translucent liquid or waxy solid at room temperature.

[0064] (3) The synthesis method of this invention has a wide variety of oxygen-containing monomers and the synthesis method has good universality. Therefore, the high molecular weight unsaturated polyesters prepared are rich in variety, which is conducive to expanding new applications of unsaturated polyesters.

[0065] This invention provides a polyester polyol, its preparation method, and its application. The preparation method includes the following steps: a) Under inert gas protection, fatty acid esters, small molecule diols, small molecule diacids, catalyst A, and stabilizers are added to a reaction vessel for esterification. During the reaction, byproducts are removed by inert gas displacement. After the acid value is less than 20 mg KOH / g, byproducts are removed by continuous vacuuming. After the acid value is less than 2 mg KOH / g, intermediate polyester polyol is obtained; b) Under inert gas protection, epoxides, acid anhydrides, and catalyst B are added to the reaction vessel containing the intermediate polyester polyol for ring-opening polymerization. After the reaction, unreacted epoxides and small molecule byproducts are removed by continuous vacuuming, and the polyester polyol is obtained after cooling. Compared with the prior art, the preparation method provided by this invention uses specific raw materials combined with specific process steps, conditions, and parameters to achieve better overall interaction, and can produce a variety of polyester polyols with different structures and narrow molecular weight distribution. At the same time, the preparation method is simple and easy to implement, requires no modification to the reaction device or equipment, saves energy and reduces emissions, is economical and environmentally friendly, and is suitable for large-scale industrial production.

[0066] Meanwhile, the preparation method provided by this invention combines the advantages of the polycondensation reaction of diols and diacids and the ring-opening reaction of epoxides and cyclic anhydrides. It has a wide variety of monomers available, is widely sourced and has low cost. It is not only atom-economical, but also has a wide variety of epoxides and cyclic anhydrides.

[0067] To further illustrate the present invention, detailed descriptions are provided below through the following embodiments. In the following embodiments / comparative examples of the present invention, the test methods involved are as follows: the hydroxyl value of the polyester polyol is determined according to the acetic anhydride-pyridine method of HG / T 2709-1995; the acid value of the polyester polyol is determined according to HGT2708-1995; the viscosity of the polyester polyol is determined using a rotational viscometer according to the standard GB / T2794-1995; and the polyester polyol is determined using a gel permeation chromatography system with THF as the eluent.

[0068] Example 1

[0069] Under inert gas protection, 500g castor oil, 280g diethylene glycol, 310g isophthalic acid, 95mg isopropyl titanate, and 310mg p-benzoquinone were added to a stainless steel reactor. The mixture was heated to 150℃, stirred at 150 rpm, and reacted for 1 hour. The temperature was then increased to 180℃ and reacted for 3 hours. Finally, the temperature was increased to 220℃ and reacted for 3 hours. During this process, byproducts were removed by inert gas purging. The degree of reaction was determined based on the amount of byproducts collected. Samples were taken when the acid value was less than 20mg. After KOH / g is applied, a vacuum is activated, and byproducts are removed by continuous vacuuming. The vacuum level of the reactor is controlled within the range of -0.005 to -0.01 MPa. Samples are taken, and the acid value is less than 2 mg KOH / g to obtain the intermediate polyester polyol. Then, under inert gas protection, 450 g of propylene oxide, 200 g of succinic anhydride, and 120 mg of zinc-cobalt bimetallic cyanide complex are added to the reactor containing the intermediate polyester polyol. The temperature is raised to 90 °C and reacted under autogenous pressure for 10 h. After the reaction is completed, the unreacted epoxides and small molecule byproducts are removed by vacuuming until the hydroxyl value and acid value reach the design values ​​to obtain the target product. The product is then cooled to below 80 °C and discharged to obtain the novel polyester polyol.

[0070] The polyester polyol obtained in Example 1 was tested and found to have an acid value of 1.5 mg KOH / g, a hydroxyl value of 120 mg KOH / g, a viscosity (80℃) of 1000 mPa·s, and a molecular weight distribution of 1.15.

[0071] Example 2

[0072] Under inert gas protection, 500g soybean oil, 280g hexanediol, 300g adipic acid, 105mg n-butyl titanate, and 600mg methylhydroquinone were added to a stainless steel reactor. The temperature was raised to 160℃, and stirring was started at 100 rpm for 1 hour. The temperature was then raised to 180℃ for 4 hours, and finally raised to 220℃ for 3 hours. During this process, byproducts were removed by inert gas displacement. The degree of reaction was judged based on the amount of byproducts collected. Once the acid value was less than 20mg KOH / g, a vacuum was applied, and byproducts were removed by continuous vacuuming. The vacuum degree of the reactor was controlled within the range of -0.005 to -0.01 MPa. Once the acid value was less than 2mg KOH / g, a sample was taken. KOH / g yields the intermediate polyester polyol; then, under inert gas protection, 450g propylene oxide, 200g succinic anhydride, and 120mg zinc-cobalt bimetallic cyanide complex are added to a reactor containing the intermediate polyester polyol. The mixture is heated to 90℃ and reacted under autogenous pressure for 12 hours. After the reaction, unreacted epoxides and small molecule byproducts are removed by vacuum until the hydroxyl value and acid value reach the designed values ​​to obtain the target product. The mixture is then cooled to below 80℃ and discharged to obtain the novel polyester polyol.

[0073] The polyester polyol obtained in Example 2 was tested and found to have an acid value of 1.5 mg KOH / g, a hydroxyl value of 120 mg KOH / g, a viscosity (80°C) of 1200 mPa·s, and a molecular weight distribution of 1.18.

[0074] Example 3

[0075] Under inert gas protection, 510g cottonseed oil, 260g hexanediol, 310g adipic acid, 95mg p-toluenesulfonic acid, and 930mg hydroquinone were added to a stainless steel reactor. The temperature was raised to 150℃, and stirring was started at 100 rpm for 1 hour. The temperature was then raised to 180℃ and reacted for 3 hours. Finally, the temperature was raised to 220℃ and reacted for 3 hours. During this process, byproducts were removed by inert gas displacement. The degree of reaction was judged based on the amount of byproducts collected. Once the acid value was less than 20mg KOH / g, a vacuum was opened, and byproducts were removed by continuous vacuuming. The vacuum degree of the reactor was controlled within the range of -0.005 to -0.01MPa. Once the acid value was less than 2mg KOH / g, a sample was taken. KOH / g yields the intermediate polyester polyol; then, under inert gas protection, 450g propylene oxide, 200g succinic anhydride, and 120mg zinc-cobalt bimetallic cyanide complex are added to a reactor containing the intermediate polyester polyol. The mixture is heated to 90℃ and reacted under autogenous pressure for 10 hours. After the reaction, unreacted epoxides and small molecule byproducts are removed by vacuum until the hydroxyl value and acid value reach the designed values ​​to obtain the target product. The mixture is then cooled to below 80℃ and discharged to obtain the novel polyester polyol.

[0076] The polyester polyol obtained in Example 3 was tested and found to have an acid value of 1.5 mg KOH / g, a hydroxyl value of 120 mg KOH / g, a viscosity (80℃) of 800 mPa·s, and a molecular weight distribution of 1.12.

[0077] Example 4

[0078] Under inert gas protection, 450g palm oil, 295g diethylene glycol, 310g adipic acid, 115mg dibutyltin dilaurate, and 1.53g 2-tert-butylhydroquinone were added to a stainless steel reactor. The temperature was raised to 150℃, and stirring was started at 100 rpm for 2 hours. The temperature was then raised to 180℃ for 3 hours, and finally raised to 220℃ for 3 hours. During this process, byproducts were removed by inert gas displacement. The degree of reaction was judged based on the amount of byproducts collected. Once the acid value was less than 20mg KOH / g, a vacuum was opened, and byproducts were removed by continuous vacuuming. The vacuum degree of the reactor was controlled within the range of -0.005 to -0.01MPa. Once the acid value was less than 2mg KOH / g, a sample was taken. KOH / g yields the intermediate polyester polyol; then, under inert gas protection, 450g propylene oxide, 200g succinic anhydride, and 120mg zinc-cobalt bimetallic cyanide complex are added to a reactor containing the intermediate polyester polyol. The mixture is heated to 90℃ and reacted under autogenous pressure for 10 hours. After the reaction, unreacted epoxides and small molecule byproducts are removed by vacuum until the hydroxyl value and acid value reach the designed values ​​to obtain the target product. The mixture is then cooled to below 80℃ and discharged to obtain the novel polyester polyol.

[0079] The polyester polyol obtained in Example 4 was tested and found to have an acid value of 1.3 mg KOH / g, a hydroxyl value of 100 mg KOH / g, a molecular weight distribution of 1.2, a viscosity (80℃) of 900 mPa·s, and a molecular weight distribution of 1.20.

[0080] Comparative Example 1

[0081] Under inert gas protection, 450g palm oil, 295g diethylene glycol, 310g adipic acid, 115mg dibutyltin dilaurate, and 1.53g 2-tert-butylhydroquinone were added to a stainless steel reactor. The mixture was heated to 150℃, stirred at 100 rpm, and reacted for 2 hours. The temperature was then increased to 180℃ and reacted for 3 hours. Finally, the temperature was increased to 220℃ and reacted for 3 hours. During this process, byproducts were removed by inert gas displacement. The degree of reaction was judged based on the amount of byproducts collected. Once the acid value was less than 20mg KOH / g, a vacuum was opened. By continuously evacuating the vacuum, byproducts were removed. The vacuum degree of the reactor was controlled within the range of -0.005 to -0.01MPa. Once the acid value was less than 2mg KOH / g, polyester polyol was obtained.

[0082] The polyester polyol obtained in Comparative Example 1 had a hydroxyl value of 110 mg KOH / g, but a wide molecular weight distribution of 2.95 and a viscosity (80℃) of 9000 mPa·s.

[0083] The results show that although the traditional polyester polyols prepared by polycondensation of diols and diacids can meet the target acid and hydroxyl values, their molecular weight distribution is too wide to meet the downstream application requirements for low molecular weight polyester polyols.

[0084] Comparative Example 2

[0085] Under inert gas protection, 450g of propylene oxide, 200g of succinic anhydride and 120mg of zinc-cobalt bimetallic cyanide complex were added to the reactor. The temperature was raised to 90℃ and the reaction was carried out under autogenous pressure for 10 hours. After the reaction was completed, the unreacted epoxides and small molecule byproducts were removed by vacuuming. However, the hydroxyl value and acid value of the product could not reach the design value to obtain the target product.

[0086] The polyester polyol obtained in Comparative Example 2 was tested and found to have a hydroxyl value of 10 mg KOH / g, an acid value of 0.5 mg KOH / g, a molecular weight distribution of 1.95, and a viscosity (80℃) of 18000 mPa·s.

[0087] The results show that the polyester polyol prepared by ring-opening polymerization of epoxide and acid anhydride alone lacks an intermediate as a chain transfer agent, and its hydroxyl value cannot meet the target hydroxyl value requirement, resulting in a higher molecular weight.

[0088] Comparative Example 3

[0089] Under inert gas protection, 500g castor oil, 280g diethylene glycol, 310g isophthalic acid, 500mg isopropyl titanate, and 310mg p-benzoquinone were added to a stainless steel reactor. The temperature was raised to 150℃, and stirring was started at 150 rpm for 1 hour. The temperature was then raised to 180℃ and reacted for 3 hours. Finally, the temperature was raised to 220℃ and reacted for 3 hours. During this process, byproducts were removed by inert gas displacement. The degree of reaction was determined based on the amount of byproducts collected. Samples were taken when the acid value was less than 20mg. After KOH / g is applied, a vacuum is activated. By continuously pumping vacuum, byproducts are removed. The vacuum level of the reactor is controlled within the range of -0.005 to -0.01 MPa. When the acid value is less than 2 mg KOH / g, the intermediate polyester polyol is obtained. Then, under inert gas protection, 450 g of propylene oxide, 200 g of succinic anhydride, and 920 mg of zinc-cobalt bimetallic cyanide complex are added to the reactor containing the intermediate polyester polyol. The temperature is raised to 90 °C and reacted under autogenous pressure for 10 h. After the reaction is completed, vacuum is applied to remove unreacted epoxides and small molecule byproducts until the hydroxyl value and acid value reach the design values ​​to obtain the target product. The product is then cooled to below 80 °C and discharged to obtain the polyester polyol.

[0090] The polyester polyol obtained in Comparative Example 3 was tested and found to have an acid value of 1.2 mg KOH / g, a hydroxyl value of 110 mg KOH / g, a molecular weight distribution of 2.15, and a viscosity (80℃) of 1000 mPa·s.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a polyester polyol, comprising the following steps: a) Under inert gas protection, fatty acid esters, small molecule diols, small molecule diacids, catalyst A, and stabilizers are added to a reaction vessel for esterification. During the reaction, byproducts are removed by inert gas displacement. After the acid value is less than 20 mg KOH / g, byproducts are removed by continuous vacuuming. After the acid value is less than 2 mg KOH / g, the intermediate polyester polyol is obtained. Catalyst A is isopropyl titanate, and the amount of catalyst A is 5 ppm to 500 ppm of the total mass of the small molecule diol and the small molecule diacid. The fatty acid esters in step a) are selected from one or more of castor oil, cottonseed oil, peanut oil, coconut oil, flaxseed oil, palm kernel oil, olive oil, corn oil, palm oil, jatropha oil, rapeseed oil, soybean oil, sunflower oil, herring oil, sardine oil, and tallow. b) Under inert gas protection, epoxide, acid anhydride and catalyst B are added to a reactor containing intermediate polyester polyol to carry out ring-opening polymerization. After the reaction is completed, unreacted epoxide and small molecule byproducts are removed by continuous vacuuming, and polyester polyol is obtained after cooling. The catalyst B is a zinc-cobalt bimetallic cyanide complex, and the amount of catalyst B used is 100 ppm to 500 ppm of the total mass of acid anhydride and epoxide.

2. The preparation method according to claim 1, characterized in that, The small molecule diol is selected from one or more of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, 1,16-hexadecanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, nonaethylene glycol, hexaethylene glycol, and dodecaethylene glycol. The small molecule dicarboxylic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, terephthalic acid, phthalic acid, isophthalic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedioic acid, and 1,16-hexadecanedicarboxylic acid; The stabilizer is selected from one or more of hydroquinone, p-hydroxyanisole, 2,5-di-tert-butylhydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, methylhydroquinone, and 2,2,6,6-tetramethyl-4-hydroxypiperidine nitroxide radical.

3. The preparation method according to claim 1, characterized in that, The mass ratio of fatty acid ester, small molecule diol, and small molecule diacid in step a) is (40~60):(10~30):(25~35); the amount of stabilizer added is 0.02%~1.5% of the mass of the small molecule diacid.

4. The preparation method according to claim 1, characterized in that, The esterification reaction described in step a) employs a stepwise temperature increase: First, raise the temperature to 130℃~150℃ and hold for 1h~2h; then raise the temperature to 170℃~190℃ and hold for 1h~3h; finally, continue to raise the temperature to 210℃~230℃ and hold for 1h~3h.

5. The preparation method according to claim 1, characterized in that, The continuous vacuuming process described in step a) controls the vacuum level of the reactor to be -0.005 to -0.01 MPa.

6. The preparation method according to claim 1, characterized in that, The epoxide mentioned in step b) is selected from one or more of ethylene oxide, propylene oxide, 1,2-epoxybutane, C5~C20 α-oxide olefins, methyl epidecenoate, cyclohexene oxide, epichlorohydrin, allyl glycidyl ether, furfuryl glycidyl ether, phenyl glycidyl ether, and butyl glycidyl ether. The anhydride is selected from one or more of phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, 2,3-dichloromaleic anhydride, trifluoromethylmaleic anhydride, bromomaleic anhydride, 2,3-dibromomaleic anhydride, phenylmaleic anhydride, citraconic anhydride, itaconic anhydride, cis-5-norbornene-ex-2,3-dicarboxylic anhydride, and bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic anhydride.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the acid anhydride to the epoxide in step b) is 1:(1~10).

8. The preparation method according to claim 1, characterized in that, The ring-opening polymerization reaction described in step b) is carried out at a temperature of 20°C to 150°C, at a pressure equal to the autogenous pressure of the reaction, and for a time of 5 to 24 hours.

9. A novel polyester polyol, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of a polyester polyol in the preparation of polyurethane adhesives, characterized in that, The polyester polyol is the novel polyester polyol described in claim 9.