Method for producing aliphatic branched polyether polyol for polyurethane compositions

Abstract

FIELD: chemical industry.SUBSTANCE: invention relates namely to the technology of producing polyester polyols used in the production of polyurethane materials, including elastomers, adhesives, sealants, coatings and other polyurethane compositions. The method includes loading into a sealed reactor dimethyl adipate and dimethyl sebacate at a molar ratio of 65:35 to 72:28, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane at a molar ratio of 50 to 56: 32 to 40: 8 to 12, and carrying out transesterification at a temperature of 180 to 195°C in a nitrogen stream in the presence of zinc acetate in an amount of 0.03 to 0.08 wt.% of the total mass of monomers until at least 92% of the theoretically calculated amount of methanol is collected, followed by the introduction of tetrabutoxytitanium in an amount of 355 to 710 mg / kg of the total mass of monomers and carrying out polycondensation at a temperature of 218 to 226°C and absolute pressure from 8 to 15 kPa until the specified values of acid and hydroxyl number are achieved, after which triethyl phosphite is introduced into the reaction mass in an amount of 0.03 to 0.08 wt.% of the total mass of monomers and the product is cooled, while diethylene glycol, phthalic anhydride, isophthalic acid and terephthalic acid are not introduced into the reaction mixture.EFFECT: obtaining an aliphatic branched polyether polyol suitable for use in polyurethane compositions, with an acid number of no more than 1.0 mg KOH / g and a hydroxyl number from 55 to 75 mg KOH / g, as well as in increasing the controllability and reproducibility of the process due to the sequential implementation of transesterification and polycondensation stages with subsequent stabilization of the reaction mass.1 cl, 2 tbl, 3 ex

Description

[0001] The invention relates to the chemical industry, specifically to a technology for producing polyester polyols used in the production of polyurethane materials. The claimed method can be used to produce polyester polyols used in the production of elastomers, adhesives, sealants, protective and decorative coatings, as well as other polyurethane materials that require stable properties, processability, and reproducibility of the final product characteristics. The invention also relates to methods for producing polyester polyols based on aliphatic dicarboxylic components and polyhydric alcohols by performing transesterification and subsequent polycondensation stages in the presence of catalytic systems.

[0002] A method for producing polyester polyols and polyurethanes is known, disclosed in International Patent No. 2015185744, in which a polyester polyol is produced by reacting two dicarboxylic acids, one of which is succinic acid, with a diol, wherein the second dicarboxylic acid can be, in particular, sebacic acid. This solution relates to the production of polyester polyols for polyurethane materials and confirms the known approach based on the use of a mixture of aliphatic dicarboxylic components for the synthesis of polyester polyol.The disadvantage of this solution in relation to the stated problem is that it focuses primarily on the use of a system based on succinic acid and an aliphatic diol, while not disclosing a specific set of features associated with the production of an aliphatic branched polyether polyol based on dimethyl esters of dicarboxylic acids, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, and also not disclosing the claimed sequence of stages of transesterification and subsequent polycondensation using zinc acetate, tetrabutoxytitanium and subsequent phosphite deactivation of the catalytic system.

[0003] Also known is a polyester and a method for producing it, disclosed in U.S. Patent 3,182,041 A, which describes the production of polyesters based on adipic acid and various polyhydric alcohols, including neopentyl glycol and trimethylolpropane, and also separately provides examples of polyesters based on isosebacic acid, neopentyl glycol, and trimethylolpropane. This solution confirms the known use of aliphatic dicarboxylic acids in combination with neopentyl glycol and trimethylolpropane to produce branched polyester products.The disadvantage of this solution is that it does not disclose the production of polyether polyol for polyurethane compositions by transesterification of dimethyl esters of dicarboxylic acids followed by polycondensation in the claimed sequence of stages, does not provide for the use of 3-methyl-1,5-pentanediol in combination with neopentyl glycol and trimethylolpropane, and does not contain instructions on the controlled introduction of the zinc acetate / tetrabutoxytitanium catalytic system and final treatment with triethyl phosphite.

[0004] Also known is the technical solution disclosed in U.S. Patent 4,182,898 A, relating to stable polyester-polyester coprepolymers, in which suitable polyester polyols are indicated, in particular, adipates of neopentyl glycol and 1,6-hexanediol, as well as adipate of diethylene glycol, 1,6-hexanediol, neopentyl glycol and trimethylolpropane. This solution confirms the known use of aliphatic adipate polyester polyols containing neopentyl glycol and trimethylolpropane in polyurethane technology.The disadvantage of this solution is that it is focused primarily on the selection of a polyol component for the production of coprepolymers and does not disclose a specific method for synthesizing an aliphatic branched polyether polyol based on a mixture of dimethyl adipate and dimethyl sebacate using a strictly defined set of diol and triol components, and also does not disclose the claimed sequence of technological stages of transesterification, polycondensation and subsequent stabilization of the product.

[0005] A method for producing a polyester material is known, disclosed in patent 102964579 B, in which the polycondensation process is carried out through a transesterification step of dimethyl ester of a dicarboxylic acid with a diol in the presence of zinc acetate and tetrabutoxytitanium, followed by vacuum polycondensation. This solution confirms the known combination of zinc acetate and tetrabutoxytitanium as a catalytic system for transesterification processes and subsequent polycondensation of polyester materials.The disadvantage of this solution is that it relates to the production of a reinforced thermoplastic polyester elastomer and is not aimed at producing an aliphatic branched polyether polyol for polyurethane compositions; in addition, it uses a different raw material system and does not disclose the claimed set of components, including dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, and does not disclose the introduction of a phosphite compound after completion of polycondensation.

[0006] A method for producing polyesters is also known, disclosed in European Patent 2 083 035 A1, in which a phosphorus-containing compound is used to suppress the residual activity of a polycondensation catalyst and improve the color or heat resistance of the polyester. This solution confirms the known approach in which phosphorus-containing compounds are used after or in conjunction with polycondensation catalysts to stabilize the polyester product. A disadvantage of this solution is that it pertains to general issues of stabilizing polyester systems and does not disclose the claimed method for producing an aliphatic branched polyester polyol for polyurethane compositions using a specific feedstock system, a two-stage catalytic scheme, and the introduction of triethyl phosphite after achieving the specified acid and hydroxyl values.

[0007] The closest in technical essence to the claimed invention is the method for producing a polyester material disclosed in Chinese Patent 102964579 B, in which the polymer product is obtained by carrying out a stage of esterification or transesterification of dimethyl ester of a dicarboxylic acid with a low-molecular dihydric alcohol in the presence of a catalytic system comprising a titanium compound as the main catalyst and acetate as a promoter, followed by a stage of polycondensation under reduced pressure. In this solution, zinc acetate and a titanium compound are provided as catalytically active compounds, and polycondensation is carried out at a temperature of 220-260°C. This solution confirms the known nature of a two-stage process including the transesterification of dimethyl ethers in the presence of acetate and titanium catalysts and subsequent vacuum polycondensation.A drawback of the prototype is that it focuses on the production of a reinforced thermoplastic polyester elastomer, not an aliphatic branched polyether polyol for polyurethane composites. Furthermore, the prototype is focused on a different feedstock system and does not disclose the use of a combination of components including dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane. It does not provide for the production of a branched polyether polyol with a specified hydroxyl number. It also contains no instructions for completing the process by adding triethyl phosphite after achieving the desired product properties.Unlike the prototype, the claimed invention is aimed at obtaining an aliphatic branched polyether polyol for polyurethane compositions, obtained from a specifically selected mixture of aliphatic dimethyl esters of dicarboxylic acids, two diol components and a triol, with a certain sequence of stages of transesterification, polycondensation and subsequent stabilization of the reaction mass, which ensures the production of a product with specified values ​​​​of acid and hydroxyl number and expands the possibilities of its use in polyurethane technology.

[0008] The technical task of the claimed invention consists in developing a method for producing an aliphatic branched polyether polyol for polyurethane compositions based on aliphatic dimethyl esters of dicarboxylic acids, diol components and a triol, ensuring the production of a target product with specified values ​​of acid and hydroxyl number in a technologically stable and reproducible process mode.

[0009] The technical result achieved by implementing the claimed invention is the production of an aliphatic branched polyether polyol suitable for use in polyurethane compositions, with an acid number of no more than 1.0 mg KOH / g and a hydroxyl number from 55 to 75 mg KOH / g.

[0010] An additional technical result is an increase in the controllability and reproducibility of the process due to the sequential implementation of the transesterification and polycondensation stages in the presence of zinc acetate and tetrabutoxytitanium, followed by stabilization of the reaction mass with triethyl phosphite.

[0011] The essence of the claimed invention consists in developing a method for producing an aliphatic branched polyether polyol for polyurethane compositions by sequentially carrying out transesterification and polycondensation stages, followed by stabilization of the reaction mass. In accordance with the claimed invention, the method is carried out in a sealed reactor equipped with a stirrer, a column, a condenser, an inert gas supply system and a vacuum system, while dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane are loaded into the reactor in predetermined ratios. In the first stage, transesterification of these components is carried out by heating in a stream of inert gas in the presence of zinc acetate until at least 92% of the theoretically calculated amount of methanol is collected.After the transesterification stage is completed, tetrabutoxytitanium is added to the reaction mixture, and a polycondensation stage is carried out at elevated temperature and reduced absolute pressure until an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g are achieved. After the polycondensation is completed, triethyl phosphite is added to the reaction mixture, after which the product is cooled. In this case, diethylene glycol, phthalic anhydride, isophthalic acid, and terephthalic acid are not added to the reaction mixture. Due to the specified combination of features, an aliphatic branched polyester polyol suitable for use in polyurethane compositions with an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g is obtained under a technologically stable and reproducible process mode.

[0012] In accordance with the claimed invention, a method for producing an aliphatic branched polyether polyol for polyurethane compositions is carried out as follows: dimethyl adipate and dimethyl sebacate are loaded into a sealed reactor equipped with a stirrer, a column, a condenser, an inert gas supply system and a vacuum system at a molar ratio of 65:35 to 72:28, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane at a molar ratio of 50 to 56: 32 to 40: 8 to 12, wherein the total molar ratio of hydroxyl groups to ester groups of dimethyl ethers is set from 1.05 to 1.10: 1, then transesterification is carried out at a temperature of 180 to 195 ° C in a stream of nitrogen in the presence of acetate zinc in an amount from 0.03 to 0.08 wt.% based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane until at least 92% of the theoretically calculated amount of methanol is collected, after which tetrabutoxytitanium is introduced in an amount of 355 to 710 mg / kg based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane and polycondensation is carried out at a temperature of 218 to 226°C and an absolute pressure of 8 to 15 kPa until an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g are achieved, then triethyl phosphite is introduced into the reaction mass in an amount of 0.03 to 0.08 wt. % based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane and cool the product, while diethylene glycol, phthalic anhydride, isophthalic acid and terephthalic acid are not added to the reaction mixture.The total mass of monomers in the context of the present invention means the combined mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane.

[0013] According to the claimed invention, a method for producing an aliphatic branched polyether polyol for polyurethane compositions is carried out in a sealed reactor equipped with a stirrer, a column, a condenser, an inert gas supply system, and a vacuum system. Use of this reactor equipment enables the sequential transesterification and polycondensation stages under controlled temperature and gas-dynamic conditions, as well as the subsequent transfer of the process to a reduced absolute pressure mode without overloading the reaction mixture and without disrupting the homogeneity of the system. The presence of a stirrer ensures uniform distribution of the components throughout the reaction mixture and maintains homogeneity of the medium throughout the process. The presence of a column and condenser ensures the effective removal and condensation of volatile reaction products, primarily methanol formed during the transesterification stage.An inert gas supply system ensures that the first stage of the process is carried out under a nitrogen flow, which helps remove volatile products, reduces the likelihood of undesirable side processes, and stabilizes synthesis conditions. A vacuum system ensures the polycondensation stage is carried out at an absolute pressure of 8 to 15 kPa, necessary to remove low-molecular compounds and produce the target polyester polyol with the specified acid and hydroxyl values.

[0014] Dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane are used as starting components. These components are selected to produce an aliphatic branched polyether polyol suitable for use in polyurethane compositions for various purposes, including elastomers, adhesives, sealants, coatings, and other polyurethane materials. This combination of starting components ensures the formation of an aliphatic polyester structure containing branches while simultaneously ensuring the required reactivity, processability, and reproducibility of the final product properties.In this case, diethylene glycol, phthalic anhydride, isophthalic acid and terephthalic acid are not introduced into the reaction mixture, which eliminates the participation of these compounds in the formation of the structure of the final product and ensures the production of an aliphatic branched polyester polyol based on the claimed set of components.

[0015] Dimethyl adipate and dimethyl sebacate are used as dimethyl esters of aliphatic dicarboxylic acids involved in the formation of the polyester backbone. The use of dimethyl adipate introduces adipate fragments into the polyester structure, promoting the formation of an aliphatic polyester backbone with the required flexibility and reactivity. The use of dimethyl sebacate introduces longer aliphatic units, affecting the structure and properties of the resulting polyester chain. Using a mixture of dimethyl adipate and dimethyl sebacate, rather than dimethyl ether alone, allows for targeted control of the polyester product structure by combining aliphatic units of varying lengths, which is essential for achieving the desired combination of processing and performance characteristics of the resulting polyester polyol.In addition, the use of dimethyl esters of dicarboxylic acids allows the process to be carried out through a transesterification stage with the formation of methanol as a low molecular weight by-product removed from the reaction system during the synthesis.

[0016] Neopentyl glycol and 3-methyl-1,5-pentanediol are used as diol components. Neopentyl glycol promotes the formation of a polyester structure with the required chemical and technological stability and is a key component determining the structure and properties of the resulting polyester polyol. 3-Methyl-1,5-pentanediol is used as a second diol component, providing additional control over the polyester chain structure and the characteristics of the final product. The combined use of neopentyl glycol and 3-methyl-1,5-pentanediol allows for the formation of a polyester structure with specified characteristics, including the desired hydroxyl number, and also ensures the suitability of the resulting polyester polyol for interaction with isocyanate components in the production of polyurethane materials.The use of two different diol components in the claimed method allows for more flexible regulation of the composition and structure of the polyester matrix compared to systems based on the use of only one diol.

[0017] Trimethylolpropane is used as a trihydric alcohol, providing branching of the polyester structure. Adding trimethylolpropane to the reaction mixture results in the formation of a branched polyester polyol structure, which distinguishes the claimed product from linear polyester systems. The use of trimethylolpropane allows for the control of the functionality of the final polyester polyol, thereby affecting its suitability for use in polyurethane composites. The presence of triol in the system ensures the formation of an aliphatic branched polyester polyol, which is consistent with the essence of the claimed invention.

[0018] Dimethyl adipate and dimethyl sebacate are loaded into the reactor at a molar ratio of 65:35 to 72:28. This ratio range was selected to ensure the required polyester chain structure, maintain the aliphatic nature of the final product, and achieve the desired characteristics of the polyester polyol. Neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane are loaded at a molar ratio of 50 to 56: 32 to 40: 8 to 12. This range of diol to triol component ratios ensures the formation of a branched polyester structure while maintaining the ability to conduct the process in a technologically stable mode. With these ratios, a balance is achieved between polyester chain growth and branching, which is necessary to obtain the target polyester polyol with the desired characteristics.

[0019] The overall molar ratio of hydroxyl groups to dimethyl ether ester groups is set at a level from 1.05 to 1.10: 1. This range ensures the required ratio of functional groups in the reaction system, sufficient for the effective transesterification and subsequent polycondensation stages, as well as for obtaining the final polyester polyol with an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g. Setting the overall molar ratio of hydroxyl groups to dimethyl ether ester groups in the stated range also improves the reproducibility of the process and ensures the production of a product suitable for use in polyurethane compositions.

[0020] The process is carried out sequentially in two main stages, including transesterification and polycondensation. This sequential process ensures the step-by-step formation of the polyester structure, allows for the controlled removal of low-molecular-weight reaction byproducts, and creates conditions for producing an aliphatic branched polyester polyol with specified acid and hydroxyl values. Dividing the process into these stages also ensures greater controllability of the synthesis and reproducibility of the final product characteristics.

[0021] The first stage involves transesterification of the starting components at a temperature of 180 to 195°C in a stream of inert gas, preferably nitrogen, in the presence of zinc acetate. Zinc acetate is used in an amount of 0.03 to 0.08 wt.% based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane. The use of zinc acetate in the transesterification stage catalytically accelerates the exchange processes between dimethyl esters of aliphatic dicarboxylic acids and the hydroxyl-containing components of the reaction mixture, which facilitates the formation of intermediate polyester structures suitable for the subsequent polycondensation stage. Carrying out transesterification in a nitrogen stream ensures the removal of the resulting methanol from the reaction system, which helps shift the reaction equilibrium towards the formation of the target polyester product and maintain stable process conditions.

[0022] This step is accompanied by the distillation of methanol, which is formed as a result of the reaction of dimethyl esters of dicarboxylic acids with hydroxyl-containing components. Transesterification is carried out until at least 92% of the theoretically calculated amount of methanol is recovered. Achieving this level of methanol recovery indicates sufficient progress in the transesterification step and creates conditions for the subsequent effective polycondensation step. With a lower degree of methanol recovery, insufficient conversion of the initial ester components may persist in the reaction system, complicating further process progress and reducing the reproducibility of the final product characteristics. Therefore, achieving this level of methanol recovery is an essential condition for implementing the claimed method.

[0023] After the transesterification stage is complete, tetrabutoxytitanium is added to the reaction mixture in an amount of 355 to 710 mg / kg, based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane. Tetrabutoxytitanium acts as a catalyst in the polycondensation stage and ensures a further increase in the molecular weight of the polyester product by intensifying the condensation reactions of intermediate hydroxyl- and ester-containing compounds. The addition of tetrabutoxytitanium after the completion of the main part of the transesterification stage allows for the separation of catalytic functions by process stages and the implementation of polycondensation under conditions in which the reaction mixture already contains a sufficient amount of intermediate products capable of further polyester chain growth.

[0024] After the introduction of tetrabutoxytitanium, a polycondensation step is carried out at a temperature of 218 to 226°C and an absolute pressure of 8 to 15 kPa. Carrying out polycondensation under these temperature conditions and absolute pressure ensures the removal of low-molecular compounds from the reaction mixture and the further development of the polyester structure, forming the target aliphatic branched polyester polyol. The specified polycondensation step parameters are selected to ensure the efficient operation of the process while maintaining the technological stability of the reaction system and achieving the required final product properties.

[0025] Polycondensation is carried out until an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g are achieved. Achieving these values ​​indicates the production of a polyester polyol suitable for subsequent use in polyurethane compositions. The acid number, expressed in milligrams of potassium hydroxide per 1 g of product, characterizes the content of residual acid groups in the resulting polyester polyol, while the hydroxyl number, also expressed in milligrams of potassium hydroxide per 1 g of product, characterizes the content of hydroxyl groups that determine the product's reactivity with isocyanate components. Carrying out polycondensation until the specified acid and hydroxyl numbers are achieved ensures the production of a product with the characteristics necessary for its use in polyurethane technology.

[0026] After the polycondensation stage is complete, triethyl phosphite is added to the reaction mixture in an amount of 0.03 to 0.08 wt.%, based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane. Adding triethyl phosphite at the final stage of the process stabilizes the reaction mixture after the main stage of polyester structure formation is complete and facilitates the production of a final product with reproducible characteristics. After the addition of triethyl phosphite, the resulting product is cooled and discharged from the reactor.

[0027] When implementing the claimed method, diethylene glycol, phthalic anhydride, isophthalic acid, and terephthalic acid are not added to the reaction mixture. Excluding these components from the reaction mixture ensures the production of an aliphatic branched polyether polyol based specifically on the claimed combination of dimethyl esters of aliphatic dicarboxylic acids, diol components, and a triol. The absence of these compounds in the initial reaction mixture eliminates their contribution to the structure of the final product, thereby ensuring that the resulting polyether polyol complies with the essence of the claimed invention.

[0028] To confirm the viability of the claimed method for producing an aliphatic branched polyester polyol for polyurethane composites, pilot syntheses were conducted using the claimed combination of components and process steps, including transesterification, polycondensation, and subsequent stabilization of the reaction mixture. Conducting pilot syntheses under the claimed conditions confirmed the feasibility of producing the target aliphatic branched polyester polyol with the specified acid and hydroxyl numbers.

[0029] In all examples, the process was carried out in a sealed reactor equipped with a stirrer, column, condenser, nitrogen supply system, and vacuum system. Dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol, and trimethylolpropane were used as starting components. Diethylene glycol, phthalic anhydride, isophthalic acid, and terephthalic acid were not added to the reaction mixture. In the first stage, transesterification was carried out under a nitrogen stream in the presence of zinc acetate with methanol distilled off. After completion of the transesterification stage, tetrabutoxytitanium was added to the reaction mixture, and polycondensation was carried out under reduced absolute pressure. After achieving the required acid and hydroxyl numbers, triethyl phosphite was added to the reaction mixture, after which the product was cooled and discharged.

[0030] Example 1. Dimethyl adipate and dimethyl sebacate were loaded into a reactor at a molar ratio of 68:32, and neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane were loaded at a molar ratio of 53:36:11. The total molar ratio of hydroxyl groups to ester groups of dimethyl ethers was set at 1.08:1. Transesterification was carried out at a temperature of 190°C in a nitrogen stream in the presence of zinc acetate in an amount of 0.05 wt. % based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane until 94% of the theoretically calculated amount of methanol was collected. After this, tetrabutoxytitanium was introduced into the reaction mass in an amount of 568 mg / kg based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, and polycondensation was carried out at a temperature of 222°C and an absolute pressure of 10 kPa until an acid number of 0.8 mg KOH / g and a hydroxyl number of 64 mg KOH / g were achieved.After completion of the polycondensation, triethyl phosphite was added to the reaction mass in an amount of 0.05 wt.% based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, the product was cooled and unloaded.

[0031] Example 2. Dimethyl adipate and dimethyl sebacate were loaded into a reactor at a molar ratio of 72:28, and neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane were loaded at a molar ratio of 56:32:12. The total molar ratio of hydroxyl groups to ester groups of dimethyl ethers was set at 1.10:1. Transesterification was carried out at a temperature of 195°C in a nitrogen stream in the presence of zinc acetate in an amount of 0.08 wt. % based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane until 92% of the theoretically calculated amount of methanol was collected. After this, tetrabutoxytitanium was introduced into the reaction mass in an amount of 710 mg / kg based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, and polycondensation was carried out at a temperature of 226°C and an absolute pressure of 8 kPa until an acid number of 0.9 mg KOH / g and a hydroxyl number of 58 mg KOH / g were achieved.After completion of the polycondensation, triethyl phosphite was added to the reaction mass in an amount of 0.08 wt.% based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, the product was cooled and unloaded.

[0032] Example 3. Dimethyl adipate and dimethyl sebacate were loaded into a reactor at a molar ratio of 65:35, and neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane were loaded at a molar ratio of 50:40:10. The total molar ratio of hydroxyl groups to ester groups of dimethyl ethers was set at 1.05:1. Transesterification was carried out at a temperature of 180°C in a nitrogen stream in the presence of zinc acetate in an amount of 0.03 wt. % based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane until 93% of the theoretically calculated amount of methanol was collected. After completion of the transesterification, tetrabutoxytitanium was introduced into the reaction mass in an amount of 355 mg / kg based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, and polycondensation was carried out at a temperature of 218°C and an absolute pressure of 15 kPa until an acid number of 1.0 mg KOH / g and a hydroxyl number of 72 mg KOH / g were achieved.After completion of the polycondensation, triethyl phosphite was added to the reaction mass in an amount of 0.03 wt.% based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane, the product was cooled and unloaded.

[0033] Table 1 - Composition and modes of implementation of the method

[0034] Parameter Example 1 Example 2 Example 3 Molar ratio of dimethyl adipate: dimethyl sebacate 68:32 72:28 65:35 Molar ratio of neopentyl glycol: 3-methyl-1,5-pentanediol: trimethylolpropane 53:36:11 56:32:12 50:40:10 The overall molar ratio of hydroxyl groups to ester groups of dimethyl ethers 1,08:1 1,10:1 1,05:1 Transesterification temperature, °C 190 195 180 Zinc acetate, wt. % based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane 0,05 0,08 0,03 Methanol recovery, % of theoretically calculated amount 94 92 93 Tetrabutoxytitanium, mg / kg based on the total mass of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane 568 710 355 Polycondensation temperature, °C 222 226 218 Absolute pressure, kPa 10 8 15 Acid number of the final product, mg KOH / g 0,8 0,9 1,0 Hydroxyl number of the final product, mg KOH / g 64 58 72 Triethyl phosphite, wt. % based on the total weight of dimethyl adipate, dimethyl sebacate, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane 0,05 0,08 0,03

[0035] As follows from Table 1, the claimed method in Examples 1-3 is carried out within the claimed ranges, and in all cases an aliphatic branched polyether polyol is obtained, suitable for use in polyurethane compositions, with an acid number of no more than 1.0 mg KOH / g and a hydroxyl number from 55 to 75 mg KOH / g. The presented data confirm the possibility of implementing the claimed method with various ratios of the initial components and modes of carrying out the transesterification and polycondensation stages within the claimed ranges.

[0036] Table 2 - Properties of the obtained polyester polyol

[0037] Indicator Example 1 Example 2 Example 3 Acid number, mg KOH / g 0,8 0,9 1,0 Hydroxyl number, mg KOH / g 64 58 72 Dynamic viscosity at 25°C, mPa s 4200 4600 3900 Color, units according to Hazen 90 105 95 Mass fraction of volatile substances, % 0,25 0,30 0,28 Residual methanol content, wt.% 0,03 0,04 0,03

[0038] As shown in Table 2, all examples yielded an aliphatic branched polyester polyol with an acid value of no more than 1.0 mg KOH / g and a hydroxyl value of 55 to 75 mg KOH / g. The obtained values ​​for dynamic viscosity, color, mass fraction of volatile matter, and residual methanol content confirm the feasibility of implementing the claimed method to obtain a target product suitable for use in polyurethane composites. These data also confirm the reproducibility of the properties of the resulting polyester polyol when varying the composition of the starting components and process conditions within the claimed ranges.

[0039] The acid number of the resulting polyether polyol was determined titrimetrically and expressed as milligrams of potassium hydroxide per 1 g of product. The hydroxyl number was determined by acetylation followed by titration and expressed as milligrams of potassium hydroxide per 1 g of product. Dynamic viscosity was determined at 25°C using a rotational viscometer. Color was determined in Hazen units. The mass fraction of volatile substances was determined gravimetrically after holding a sample of the product at a given temperature until constant weight. The residual methanol content was determined by gas-liquid chromatography.

Claims

A method for producing an aliphatic branched polyether polyol for polyurethane compositions, characterized in that dimethyl adipate and dimethyl sebacate are loaded into a sealed reactor equipped with a stirrer, a column, a condenser, an inert gas supply system and a vacuum system at a molar ratio of 65:35 to 72:28, neopentyl glycol, 3-methyl-1,5-pentanediol and trimethylolpropane at a molar ratio of 50 to 56: 32 to 40: 8 to 12, wherein the total molar ratio of hydroxyl groups to ester groups of dimethyl ethers is set at 1.05 to 1.10: 1, then transesterification is carried out at a temperature of 180 to 195°C in a nitrogen stream in the presence of zinc acetate in an amount of 0.03 to 0.08 mass.% of the total mass of monomers until at least 92% of the theoretically calculated amount of methanol is collected, after which tetrabutoxytitanium is introduced in an amount of 355 to 710 mg / kg of the total mass of monomers and polycondensation is carried out at a temperature of 218 to 226°C and an absolute pressure of 8 to 15 kPa until an acid number of no more than 1.0 mg KOH / g and a hydroxyl number of 55 to 75 mg KOH / g are achieved, then triethyl phosphite is introduced into the reaction mass in an amount of 0.03 to 0.08 wt.% of the total mass of monomers and the product is cooled, while diethylene glycol, phthalic anhydride, isophthalic acid and terephthalic acid are not introduced into the reaction mixture.