Method for preparing long-chain binary primary alcohol for polyurethane by converting vegetable oleic acid methyl ester

Abstract

The invention discloses a method for preparing long-chain binary primary alcohol for polyurethane by converting vegetable oleic acid methyl ester, which comprises the following steps: (1) carrying out sulfydryl-alkene click reaction on methyl oleate from vegetable oil and sulfydryl ester to prepare vegetable oleic acid diester; (2) hydrazine hydrate and the product in the step (1) are used as raw materials, and vegetable oleic acid dihydrazide is prepared through hydrazinolysis reaction; and (3) taking 5-hydroxymethylfurfural and the product in the step (2) as raw materials, and preparing the long-chain binary primary alcohol for polyurethane through a ketone-hydrazine condensation reaction. The method has the advantages of easily available raw materials, low cost, mild reaction conditions, simplicity and convenience in operation and the like; the obtained binary primary alcohol not only has long carbon chain, large molecular weight and high bio-based content, but also shows reversible crosslinking characteristic due to the dynamic acylhydrazone bond. The binary primary alcohol can replace the traditional petroleum-based polyether or polyester glycol, and is used for producing polyurethane products with high bio-based content and self-repairing function, such as synthetic leather, coating, adhesive and the like.

Description

Technical Field

[0001] The present invention relates to a method for preparing long-chain dibasic primary alcohols for polyurethane from methyl oleate, belonging to the technical field of bio-based polyurethane materials. Background Art

[0002] As the fifth largest polymer material globally, polyurethane has an annual output of up to 38 million tons and is widely used in fields such as synthetic leather, coatings, adhesives, etc. However, its production mainly relies on petroleum-based polyether or polyester diols (molecular weight 500 - 4000 Da) as key raw materials. With the increasing depletion of petroleum resources and the intensifying fluctuations in raw material prices, its unsustainability issues have become increasingly prominent. Against this background, developing bio-based diols that can replace petroleum-based polyether or polyester diols not only has important economic value but also conforms to the trend of sustainable development.

[0003] The preparation of bio-based diols usually uses vegetable oils as raw materials and is mainly achieved through bioconversion and chemical conversion methods. The bioconversion method uses glycerol, a by-product of vegetable oil processing, as a raw material and obtains diols through fermentation and other means. However, the diols prepared by this method have the defects of short carbon chains and small molecular weights, and can only be used as polyurethane chain extenders, unable to effectively replace polyether or polyester diols, resulting in a low bio-based content of polyurethane products. The chemical conversion method uses the double bonds in vegetable oil triglycerides as reaction sites and prepares diols through ring-opening after epoxidation. Although it can obtain products with larger molecular weights (about 900 Da), it mainly consists of secondary hydroxyl groups with relatively low reactivity, and the functionality is limited by the number of double bonds in triglycerides, making it difficult to precisely control. Therefore, developing a new technology that can use vegetable oils as raw materials to prepare long-chain dibasic primary alcohols with a molecular weight greater than 500 Da and controllable functionality has become the key direction to break through the bottleneck of existing technologies and achieve efficient substitution of polyurethane biomass raw materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing long-chain dibasic primary alcohols for polyurethane from methyl oleate to overcome the deficiencies of the prior art. First, methyl oleate derived from vegetable oil is subjected to a thiol-ene click reaction with a thiol ester to prepare a vegetable oil-based diester; subsequently, the obtained vegetable oil-based diester and hydrazine hydrate are subjected to a hydrazinolysis reaction to generate a vegetable oil-based diacylhydrazine; finally, using aldehyde-ketone bio-based raw materials such as 5-hydroxymethylfurfural as substrates, a ketone-hydrazine condensation reaction is carried out with the vegetable oil-based diacylhydrazine to prepare long-chain dibasic primary alcohols for polyurethane.

[0005] A method for preparing long-chain dibasic primary alcohols for polyurethane from methyl oleate includes:

[0006] (1) Preparation of vegetable oil fatty acid-based diester: Weigh a certain amount of methyl vegetable oil fatty acid and ethyl 3-mercaptopropionate in a photoreaction tube according to a molar ratio of 1:1, and then add a photoinitiator accounting for 1.5% - 2.5% of the total weight of methyl vegetable oil fatty acid and ethyl 3-mercaptopropionate; under ultraviolet light irradiation, react at room temperature for 4 h;

[0007] (2) Preparation of vegetable oil fatty acid-based dihydrazide: First, dissolve the vegetable oil fatty acid-based diester in step (1) in a certain amount of ethanol solution, and then add hydrazine hydrate dropwise, controlling the molar ratio of the vegetable oil fatty acid-based diester to hydrazine hydrate to be 1:4, and reflux and react at 80 °C for 12 h; the finally obtained solution is subjected to rotary evaporation and drying treatment to obtain a milky white paste-like vegetable oil fatty acid-based dihydrazide;

[0008] (3) Preparation of long-chain dibasic primary alcohol for polyurethane: First, dissolve the vegetable oil fatty acid-based dihydrazide in step (2) in a certain amount of ethanol solution, and then add 5-hydroxymethylfurfural, controlling the molar ratio of the vegetable oil fatty acid-based dihydrazide to 5-hydroxymethylfurfural to be 1:2, and reflux and react at 80 °C for 4 h; finally, a yellow paste-like product is obtained through rotary evaporation and drying treatment.

[0009] The method for preparing long-chain dibasic primary alcohol for polyurethane by converting methyl vegetable oil fatty acid is characterized in that: the methyl vegetable oil fatty acid used in this method can be sourced from one or more of olive oil, camellia seed oil, rapeseed oil, and peanut oil.

[0010] The method for preparing long-chain dibasic primary alcohol for polyurethane by converting methyl vegetable oil fatty acid is characterized in that: the ethyl 3-mercaptopropionate used in this method can be replaced by other mercapto esters, such as one or more of isopropyl 3-mercaptopropionate and isooctyl 3-mercaptopropionate.

[0011] The method for preparing long-chain dibasic primary alcohol for polyurethane by converting methyl vegetable oil fatty acid is characterized in that: the 5-hydroxymethylfurfural used in this method can be replaced by one or more other aldehyde-ketone-based bio-based raw materials, such as zingerone and syringaldehyde.

[0012] Compared with other technologies, the differences of the present invention are reflected in:

[0013] 1. The patent application with the publication number CN113735749B discloses a preparation method of a bio - based polyurethane - used dibasic primary alcohol with adjustable molecular weight. This method uses methyl oleate as the raw material and realizes the synthesis of the bio - based dibasic primary alcohol through the technical route of "Claisen condensation reaction → thiol - ene click reaction → bio - based dibasic primary alcohol". However, strong alkaline reagents such as sodium hydride are used in this process, bringing potential explosion risks and increasing the safety hazards in operation. In addition, no dynamic reversible chemical bonds are introduced into the molecular structure of the obtained dibasic primary alcohol, making it difficult to endow the polyurethane material with self - healing properties, thus limiting the durability and functionality of the material.

[0014] 2. The patent application with the publication number CN114805260A discloses a preparation method of a long - chain bio - based polyurethane - used dibasic primary alcohol. This method is based on biomass resources and realizes the preparation of the bio - based dibasic primary alcohol through the technical route of "Passerini three - component reaction → thiol - ene click reaction → bio - based dibasic primary alcohol". Nevertheless, the raw materials used in this method have relatively high costs, and the bio - based content of the product is relatively low, resulting in relatively high production costs. In addition, this method also fails to introduce dynamic reversible cross - linked bonds into the molecular structure, resulting in the inability of the prepared polyurethane material to achieve self - healing functions, thus restricting the durability of the product and the potential for further functional development.

[0015] In summary, although the existing preparation methods of long - chain bio - based dibasic primary alcohols for polyurethanes have their own characteristics, there are still obvious deficiencies, such as safety problems, relatively high production costs, and the problem of not introducing dynamic reversible cross - linked bond design into the molecular structure. These defects make it difficult for the obtained polyurethane materials to simultaneously possess self - healing functions and good recyclability. Therefore, developing a long - chain dibasic alcohol that can be efficiently prepared under mild conditions, has a high bio - based content, controllable functionality, and self - healing characteristics is the key direction for the practical application of bio - based polyurethane materials. Brief Description of the Drawings

[0016] Figure 1 It is the synthesis route for the conversion of methyl oleate involved in the present invention to prepare a long - chain dibasic alcohol for polyurethane.

[0017] Figure 2 It is the mass spectrometry characterization diagram of the intermediate synthesized in Example 1: vegetable oil acid - based diester.

[0018] Figure 3 It is the mass spectrometry characterization diagram of the intermediate synthesized in Example 1: vegetable oil acid - based dihydrazide.

[0019] Figure 4 It is the mass spectrometry characterization diagram of the product in Example 1: the long - chain dibasic alcohol prepared by the conversion of methyl oleate for polyurethane. Detailed Embodiments

[0020] The following describes in detail the specific implementation manners of the present invention in conjunction with specific embodiments. However, it should be understood that the protection scope of the present invention is not limited by the following embodiments. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention should still fall within the protection scope of the present invention. In addition, unless otherwise specified, each raw material used in the present invention can be obtained through market purchase.

[0021] Example 1

[0022] (1) Preparation of vegetable oil fatty acid-based diester: Weigh a certain amount of methyl vegetable oil fatty acid ester and ethyl 3-mercaptopropionate in a photoreaction tube according to a molar ratio of 1:1, and then add a photoinitiator accounting for 1.5% - 2.5% of the total weight of methyl vegetable oil fatty acid ester and ethyl 3-mercaptopropionate; under ultraviolet light irradiation, react at room temperature for 4 h;

[0023] (2) Preparation of vegetable oil fatty acid-based dihydrazide: First, dissolve the vegetable oil fatty acid-based diester in step (1) in a certain amount of ethanol solution, and then add hydrazine hydrate dropwise, controlling the molar ratio of the vegetable oil fatty acid-based diester to hydrazine hydrate to be 1:4, and reflux and react at 80 °C for 12 h; finally, the obtained solution is subjected to rotary evaporation and drying treatment to obtain a milky white paste-like vegetable oil fatty acid-based dihydrazide;

[0024] (3) Preparation of long-chain dibasic primary alcohol for polyurethane: First, dissolve the vegetable oil fatty acid-based dihydrazide in step (2) in a certain amount of ethanol solution, and then add 5-hydroxymethylfurfural, controlling the molar ratio of the vegetable oil fatty acid-based dihydrazide to 5-hydroxymethylfurfural to be 1:2, and reflux and react at 80 °C for 4 h; finally, after rotary evaporation and drying treatment, a yellow paste-like product can be obtained.

[0025] Example 2

[0026] (1) Preparation of vegetable oil fatty acid-based diester: Weigh a certain amount of methyl vegetable oil fatty acid ester and isopropyl 3-mercaptopropionate in a photoreaction tube according to a molar ratio of 1:1, and then add a photoinitiator accounting for 1.5% - 2.5% of the total weight of methyl vegetable oil fatty acid ester and isopropyl 3-mercaptopropionate; under ultraviolet light irradiation, react at room temperature for 4 h;

[0027] (2) Preparation of vegetable oil fatty acid-based dihydrazide: First, dissolve the vegetable oil fatty acid-based diester in step (1) in a certain amount of ethanol solution, and then add hydrazine hydrate dropwise, controlling the molar ratio of the vegetable oil fatty acid-based diester to hydrazine hydrate to be 1:4, and reflux and react at 80 °C for 12 h; finally, the obtained solution is subjected to rotary evaporation and drying treatment to obtain a milky white paste-like vegetable oil fatty acid-based dihydrazide;

[0028] (3) Preparation of long-chain dibasic primary alcohol for polyurethane: First, dissolve the vegetable oil fatty acid-based dihydrazide in step (2) in a certain amount of ethanol solution, then add syringaldehyde, control the molar ratio of vegetable oil fatty acid-based dihydrazide to syringaldehyde to be 1:2, and reflux and react at 80 °C for 4 h; finally, obtain a milky white paste-like product after rotary evaporation and drying treatment.

[0029] Example 3

[0030] (1) Preparation of vegetable oil fatty acid-based diester: Weigh a certain amount of methyl oleate and isooctyl 3-mercaptopropionate in a photoreaction tube according to a molar ratio of 1:1, and then add 1.5% - 2.5% of a photoinitiator based on the total weight of methyl oleate and isopropyl 3-mercaptopropionate; under ultraviolet light irradiation, react at room temperature for 4 h;

[0031] (2) Preparation of vegetable oil fatty acid-based dihydrazide: First, dissolve the vegetable oil fatty acid-based diester in step (1) in a certain amount of ethanol solution, then add hydrazine hydrate dropwise, control the molar ratio of vegetable oil fatty acid-based diester to hydrazine hydrate to be 1:4, and reflux and react at 80 °C for 12 h; finally, obtain a milky white paste-like vegetable oil fatty acid-based dihydrazide after rotary evaporation and drying treatment of the resulting solution;

[0032] (3) Preparation of long-chain dibasic primary alcohol for polyurethane: First, dissolve the vegetable oil fatty acid-based dihydrazide in step (2) in a certain amount of ethanol solution, then add syringaldehyde, control the molar ratio of vegetable oil fatty acid-based dihydrazide to syringaldehyde to be 1:2, and reflux and react at 80 °C for 4 h; finally, obtain a milky white paste-like product after rotary evaporation and drying treatment.

Claims

1. A method for preparing long-chain dihydric primary alcohol for polyurethane by converting vegetable oleic acid methyl ester, characterized in that The steps include: (1) Preparation of vegetable oleic acid diester: a certain amount of vegetable oleic acid methyl ester and ethyl 3-mercaptopropionate were weighed in a photoreaction tube at a molar ratio of 1:1, and then 1.5% to 2.5% of a photoinitiator was added based on the total weight of vegetable oleic acid methyl ester and ethyl 3-mercaptopropionate; the reaction was carried out at room temperature for 4 hours under ultraviolet light; (2) Preparation of vegetable oleic acid dihydrazide: firstly, the vegetable oleic acid diester in step (1) is dissolved in a certain amount of ethanol solution, and then hydrazine hydrate is added dropwise, the molar ratio of the vegetable oleic acid diester to the hydrazine hydrate is controlled to be 1:4, and the mixture is refluxed at 80° C. for 12 h; the resulting solution is subjected to rotary evaporation and drying to obtain a milky white paste of vegetable oleic acid dihydrazide; (3) Preparation of long-chain dihydric alcohol for polyurethane: First, the vegetable oil dihydrazide in step (2) is dissolved in a certain amount of ethanol solution, and then 5-hydroxymethylfurfural is added, and the molar ratio of vegetable oil dihydrazide to 5-hydroxymethylfurfural is controlled to be 1:2, and reflux reaction is carried out at 80°C for 4 hours; finally, a yellow paste product is obtained by rotary evaporation and drying.

2. The method for preparing long-chain dihydric primary alcohol for polyurethane by converting vegetable oleic acid methyl ester as claimed in claim 1, characterized in that: The vegetable oleic acid methyl ester used in the method can be derived from one or more of olive oil, camellia oil, rapeseed oil and peanut oil.

3. The method for preparing long-chain dihydric primary alcohol for polyurethane by converting vegetable oleic acid methyl ester as claimed in claim 1, characterized in that: The ethyl 3-mercaptopropionate used in the method can be replaced by other mercapto esters, such as one or more of isopropyl 3-mercaptopropionate, isooctyl 3-mercaptopropionate, etc.

4. The method for preparing long-chain dihydric primary alcohol for polyurethane by converting vegetable oleic acid methyl ester as claimed in claim 1, characterized in that: The 5-hydroxymethylfurfural used in the method can be replaced by one or more other aldehyde and ketone bio-based raw materials such as ginger ketone and syringaldehyde.

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