A method for preparing fully biodegradable bio-based polyols using starch

Abstract

This invention addresses the problem of incomplete degradation of existing biomass polyols by providing a method for preparing fully biodegradable bio-based polyols from starch, belonging to the field of refined biomass utilization technology. This method uses epoxidized soybean oil as a starch liquefaction agent and tartaric acid as a catalyst for starch degradation. Since epoxidized soybean oil, starch, and tartaric acid are all biomass, this method prepares fully biodegradable bio-based polyols, achieving a starch-to-polyol conversion rate of over 99.5% and a biodegradability rate of over 99% for the resulting bio-based polyols.

Description

Technical Field

[0001] This invention belongs to the field of biomass fine utilization technology, specifically relating to a method for preparing fully biodegradable bio-based polyols using starch. Background Technology

[0002] Polyurethane materials are widely used in various industries, but the main raw materials for producing polyurethane, polyols and isocyanates, are derived from petrochemical resources. Due to the increasing scarcity of petrochemical resources and rising oil prices in recent years, the production cost of polyurethane has also increased. Furthermore, a large amount of polyurethane cannot be degraded or recycled, causing environmental pollution. Replacing petroleum-based raw materials with bio-based products has become an important direction for the development of polyurethane materials. Compared with petroleum-based polyols, biomass polyols reduce energy consumption by more than 20%, non-renewable resource consumption by more than 60%, and greenhouse gas emissions by more than 30%.

[0003] Starch not only possesses the characteristics of a renewable resource, but its composition is also relatively simple, containing a large number of hydroxyl groups in its molecular chain, making it suitable as a raw material for the production of polyols. Starch liquefaction is an important route for converting starch into liquid polyols. For example, CN201710354087.6 discloses a method for preparing starch-based polyether polyols, using a mixed solution of polyethylene glycol 200 and glycerol as raw materials and starch as raw materials, reacting under hydrothermal conditions to prepare polyether polyols. CN202410827809.5 discloses a cesium chloride molecular sieve catalyst and its application in the preparation of bio-based polyether polyols. First, a cesium chloride molecular sieve catalyst is prepared, and then, using corn starch as raw material and a mixture of polyethylene glycol 200 and glycerol as a liquefying agent, bio-based polyether polyols are prepared using the cesium chloride molecular sieve catalyst. The liquefying agent used in the above starch liquefaction mainly uses polyethylene glycol. As a petroleum-based product, polyethylene glycol is non-degradable, and the produced polyols do not meet the requirements for complete biodegradability. The preparation of polyols from epoxidized soybean oil has been reported, but the price of epoxidized soybean oil is three times that of starch, resulting in high costs. Therefore, there is an urgent need to develop new methods for preparing bio-based polyether polyols to achieve complete biodegradability and reduce production costs. Summary of the Invention

[0004] This invention aims to address the problem that existing biomass polyols cannot be completely degraded by providing a method for preparing fully biodegradable bio-based polyols using starch. This method uses epoxidized soybean oil as a starch liquefaction agent and tartaric acid as a catalyst to degrade starch. Epoxidized soybean oil, starch, and tartaric acid are all biomass. The method prepares fully biodegradable bio-based polyols, achieving a starch-to-polyol conversion rate of over 99.5% and a biodegradability rate of over 99% for the resulting bio-based polyols.

[0005] The technical solution of the present invention is: a method for preparing fully biodegradable bio-based polyols using starch, characterized in that starch, epoxidized soybean oil and L-tartaric acid are stirred and mixed evenly, the reaction mixture is heated at 70-90°C for 3-5 hours, and then the temperature is raised to 120-140°C for 2-4 hours. After the reaction is completed, the liquid is distilled under reduced pressure to remove water, thereby obtaining the bio-based polyol.

[0006] Furthermore, the mass ratio of starch, epoxidized soybean oil and L-tartaric acid is 100-80:200-300:5-10.

[0007] Furthermore, the starch is at least one of corn starch, tapioca starch, and potato starch.

[0008] Furthermore, the epoxidized soybean oil has an epoxy value of ≥6.0%.

[0009] Furthermore, the vacuum distillation dehydration specifically involves dehydrating the reaction product under reduced pressure at 105~115℃ and -0.07~-0.09MPa until the water content of the product is less than 0.1%.

[0010] The technical principle of this invention is as follows: First, the hydroxyl groups in L-tartaric acid are used to open the ring of epoxidized soybean oil to form soybean oil polyols, which serve as liquefying agents for starch. Then, the acidic hydrolysis of the carboxyl groups in tartaric acid degrades the starch, transforming it from a solid to a liquid state and converting it into small-molecule polyhydroxy compounds, forming fully biodegradable bio-based polyols. Specifically, tartaric acid (2,3-dihydroxysuccinic acid) contains two carboxyl groups and two hydroxyl groups, existing in three stereoisomers: levorotatory, dextrorotatory, and meso. This invention uses levorotatory tartaric acid (L-tartaric acid). Under acidic catalysis (the hydrogen ions of L-tartaric acid), the epoxy groups of epoxidized soybean oil are attacked and opened by the hydroxyl groups of L-tartaric acid, generating ether bonds and a new secondary hydroxyl group. This achieves grafting, chain extension, compatibilization, and increases the hydroxyl value, forming a polyether polyol. Simultaneously, it can also serve as a liquefying agent for the conversion of starch into starch polyols, because the large number of secondary hydroxyl groups after ring opening can form hydrogen bonds with the starch hydroxyl groups, disrupting the starch crystalline region → starch swelling, softening, and liquefaction. Starch can be degraded by esterification with the carboxyl group of L-tartaric acid. Then, the remaining carboxyl group can be used to introduce hydroxyl groups by ring-opening with the epoxy group of epoxidized soybean oil to prepare starch-based polyols with stable structure, excellent compatibility, and direct application in polyurethane.

[0011] The beneficial effects of this invention are as follows: 1. This invention utilizes three biomass components—epoxidized soybean oil, starch, and tartaric acid—to prepare a fully biodegradable bio-based polyol, achieving a starch-to-polyol conversion rate of over 99.5% and a biodegradability rate of over 99% for the bio-based polyol product.

[0012] 2. The bio-based polyol prepared by this invention has a cost that is more than 30% lower than that of soybean oil polyol (the cost of this invention is about 12 yuan / kg, while the cost of soybean oil polyol is about 18 yuan / kg).

[0013] 3. The reaction conditions of this invention are mild, the operation method is simple, the cost is low, and it is completely biodegradable, making it a complete replacement for petroleum resources and a green process route. It also reduces carbon dioxide emissions, is environmentally friendly, and is conducive to industrial production. Detailed Implementation

[0014] The present invention will be further described in conjunction with the embodiments.

[0015] Example 1: Add 80g of corn starch to 200g of epoxidized soybean oil and 5g of L-tartaric acid and stir to mix. Heat the reaction mixture at 70°C for 3 hours, then raise the temperature to 120°C and react for 3 hours. After the reaction is completed, dehydrate the reaction mixture under reduced pressure at 110°C and -0.08MPa until the water content of the product is less than 0.1%, thus obtaining a fully biodegradable bio-based polyol.

[0016] Example 2: Add 85g of cassava starch to 210g of epoxidized soybean oil and 6g of L-tartaric acid and stir to mix. Heat the reaction mixture at 80℃ for 4 hours, then raise the temperature to 120℃ and react for 4 hours. After the reaction is completed, dehydrate the reaction mixture under reduced pressure at 110℃ and -0.08MPa until the water content of the product is less than 0.1%, thus obtaining a fully biodegradable bio-based polyol.

[0017] Example 3: Add 90g of potato starch to 220g of epoxidized soybean oil and 7g of L-tartaric acid and stir to mix. Heat the reaction mixture at 85℃ for 4 hours, then raise the temperature to 130℃ and react for 2 hours. After the reaction is completed, dehydrate the reaction mixture under reduced pressure at 110℃ and -0.08MPa until the water content of the product is less than 0.1%, thus obtaining a fully biodegradable bio-based polyol.

[0018] Example 4: Add 95g of corn starch to 230g of epoxidized soybean oil and 8g of L-tartaric acid and stir to mix. Heat the reaction mixture at 90℃ for 5 hours, then raise the temperature to 140℃ and react for 4 hours. After the reaction is completed, dehydrate the reaction mixture under reduced pressure at 110℃ and -0.08MPa until the water content of the product is less than 0.1%, thus obtaining a fully biodegradable bio-based polyol.

[0019] Example 5: 100g of corn starch was added to 300g of epoxidized soybean oil and 10g of L-tartaric acid and stirred. The reaction mixture was heated at 90℃ for 5 hours, and then the temperature was increased to 135℃ for 3 hours. After the reaction was completed, the reaction mixture was dehydrated under reduced pressure at 110℃ and -0.08MPa until the water content of the product was less than 0.1%, thus obtaining a fully biodegradable bio-based polyol.

[0020] The fully biodegradable bio-based polyols from Examples 1-5 were tested, and the experimental results are shown in Table 1 below.

[0021] The hydroxyl value was determined according to the method in Part III of GB / T 12008 "Plastics - Polyether Polyols", the acid value was determined according to the method in Part V of GB / T 12008 "Plastics - Polyether Polyols", and the moisture content was determined according to the method specified in GB / T 22313-2008.

[0022] The conversion rate of starch to polyols (starch liquefaction rate) was determined according to the following method: Add 20 mL of a mixed solution of dioxane and water (dioxane to water mass ratio 6:4) and 2.0 g of the liquefaction product to a beaker. Place the beaker in an 80°C water bath and stir for 20 min, then cool to room temperature. Filter through a Buchner funnel and wash with the mixed solution of dioxane and water until the filtrate is colorless. After filtration, place the residue in a watch glass and dry in a 105°C oven for 4 h. Weigh the residue of the liquefaction product. The liquefaction rate is calculated using the following formula: Residue percentage (%) = (Mass of residue / Mass of liquefied product taken) × 100% Liquefaction rate (%) = 100% - Residue rate (%) The biodegradability was determined according to GB / T 19277.1-2025 Determination of final aerobic biodegradability of materials under controlled composting conditions, using the method for determining the released carbon dioxide, Part 1: General method.

[0023] Table 1: Results of bio-based polyol index determination in Examples 1-5 (fully biodegradable)

[0024] As can be seen from the test results in Table 1, the fully biodegradable bio-based polyols meet the standard of GB / T 12008 "Plastic Polyether Polyols". The conversion rate (starch liquefaction rate) of the starch-to-polyols reaches more than 99.5%, and the biodegradation rate of the bio-based polyols reaches more than 90%.

[0025] Example 6: (Preparation of rigid polyurethane material from the product) 100g of the fully degraded biomass polyol prepared in Example 1, 4g of deionized water, 0.4g of silicone oil L-580 and 0.6g of dibutyltin dilaurate were stirred at high speed for 15s to ensure thorough mixing. 120g of isocyanate (TDI) was added and stirred at high speed for another 20s. The mixture was then poured into a polytetrafluoroethylene mold and allowed to foam freely. After foaming, the mold was placed in an oven at 40°C for 24h to obtain polyurethane foam.

[0026] The rigid polyurethane foam was subjected to performance testing: the compressive strength was 0.15 MPa, and the average apparent density was 32 kg / m³. 3 The thermal conductivity is 0.020 m·K. This means that the rigid polyurethane foam prepared using the fully biodegradable biomass polyol of this invention meets the requirements of the national standard GB-T26689-2024.

[0027] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing fully biodegradable bio-based polyols using starch, characterized in that, Starch, epoxidized soybean oil and L-tartaric acid are stirred and mixed evenly. The reaction mixture is heated at 70-90℃ for 3-5 hours, and then the temperature is raised to 120-140℃ for 2-4 hours. After the reaction is completed, the liquid is distilled under reduced pressure to remove water, and the bio-based polyol is obtained.

2. The method for preparing fully biodegradable bio-based polyols using starch as described in claim 1, characterized in that, The mass ratio of starch, epoxidized soybean oil and L-tartaric acid is 100-80:200-300:5-10.

3. The method for preparing fully biodegradable bio-based polyols using starch as described in claim 1, characterized in that, The starch is at least one of corn starch, tapioca starch, and potato starch.

4. The method for preparing fully biodegradable bio-based polyols using starch as described in claim 1, characterized in that, The epoxidized soybean oil has an epoxy value of ≥6.0%.

5. The method for preparing fully biodegradable bio-based polyols using starch as described in claim 1, characterized in that, The vacuum distillation dehydration specifically involves dehydrating the reaction product under reduced pressure at 105~115℃ and -0.07~-0.09MPa until the water content of the product is less than 0.1%.

6. The method for preparing fully biodegradable bio-based polyols from starch according to any one of claims 1-5, characterized in that, The biodegradability rate reaches over 99%.

7. The method for preparing fully biodegradable bio-based polyols from starch according to any one of claims 1-5, characterized in that, The conversion rate of starch to polyols reaches over 99.5%.

8. The bio-based polyol prepared by the method of any one of claims 1-5.

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