A polyurethane controlled release fertilizer coating material containing furandicarboxylic acid based on renewable raw materials, its use and products

Abstract

The present application relates to the technical field of controlled-release fertilizer coating materials, in particular to a polyurethane controlled-release fertilizer coating material containing furandicarboxylic acid based on renewable raw materials, application and product thereof. The present application first introduces furan ring structural units into the polyurethane controlled-release fertilizer coating material, which is prepared by crosslinking reaction of a bio-based polyester polyol product containing furandicarboxylic acid (hereinafter referred to as Bio-FDCA) based on furandicarboxylic acid obtained from renewable raw materials and isocyanate. The present application specifically selects bio-based furandicarboxylic acid and organic acid, and synthesizes a specific polyester polyol with small molecule alcohols. The raw materials, including Bio-FDCA, adipic acid, vegetable fatty acid, acetic acid, glycerol, 1,4-butanediol, diethylene glycol and other small molecule alcohol acids, are all derived from biological sources, which significantly improves the biomass ratio and is safe and environmentally friendly. The formula design of the present application can improve the performance of the film material with a lower furandicarboxylic acid ratio, thereby effectively controlling the cost and having high market value.

Description

Technical Field

[0001] This invention belongs to the field of controlled-release fertilizer technology, and particularly relates to the field under IPC classification number C05G3 / 40. More specifically, it relates to a polyurethane controlled-release fertilizer coating material containing furan dicarboxylic acid based on renewable raw materials, and its applications and products. Background Technology

[0002] Polymer polyols are one of the key raw materials determining the performance of polyurethane materials. Commercially available polyester polyols are almost all prepared by dehydration and polycondensation of simple adipic acid and small-molecule polyols under vacuum and high-temperature conditions. Polyurethane products based on this structure possess excellent properties such as high mechanical strength, oil resistance, heat resistance, and aging resistance. However, they also have significant shortcomings in hydrolysis resistance, salt spray resistance, and resistance to alternating damp heat differences. To improve these properties, the industry commonly introduces small proportions of ortho-, meta-, and terephthalic acids (phenylene ring dicarboxylic acids) into the system. The addition of aromatic structures not only increases the rigidity of the molecular backbone, further improving the mechanical properties of polyurethane products, but also improves the water resistance and other properties of the material due to steric hindrance and crystallization factors. However, because the hydrophobicity is not strong enough after the introduction of phthalic acid, the release period of the prepared polyester polyols is relatively short when used in controlled-release fertilizers, thus limiting the application of polyester polyols in downstream controlled-release fertilizer products.

[0003] Bio-based polyester polyols are novel materials manufactured using renewable biomass as raw materials through biological, chemical, and physical methods. With the emergence of bio-based materials, the demands for low-carbon and environmentally friendly production, as well as diversified market consumption needs, can be simultaneously met, making bio-based materials a new choice. Bio-based materials offer numerous advantages, including being green and low-carbon, energy-saving and environmentally friendly, and using renewable raw materials. They also possess excellent biodegradability and have a wide range of applications.

[0004] Chinese patent document CN 116515079 A discloses a bio-based polyurethane controlled-release fertilizer coating material and a polyurethane controlled-release fertilizer. The coating material is prepared by crosslinking a bio-based 1,5-pentanediisocyanate complex with a bio-based polyol. The bio-based polyol is formed by ring-opening polymerization of epoxidized fatty acid esters, lactic acid, and a bio-based alcohol. The bio-based acid used in this patent is lactic acid. Lactic acid molecules have a small molecular weight and contain certain polar functional groups, exhibiting some hydrophilicity. Although it becomes hydrophobic after esterification with the bio-based alcohol and esterification catalyst, the hydrophobicity is weak. Therefore, when used as a coating for slow-release fertilizers, the thickness needs to be increased to improve the hydrophobicity and extend the slow-release period, resulting in higher costs.

[0005] Chinese patent CN115873200A discloses another type of bio-based polyol for preparing controlled-release fertilizers, which is obtained by liquefying biomass materials such as starch or straw. However, its preparation process is complex, the biomass content is low, and the controlled-release period can only reach 60 days under low coating rate. Further extending the controlled-release period can only be achieved by increasing the coating rate, which will lead to an increase in production costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polyurethane controlled-release fertilizer coating material containing furan dicarboxylic acid based on renewable raw materials, which is highly biodegradable, environmentally friendly and safe, has strong hydrophobicity, good sealing properties, and is suitable for mass production.

[0007] On the other hand, the present invention also aims to provide an application of the above-mentioned polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials.

[0008] On the other hand, another objective of the present invention is to provide a product obtained by the above-described application.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials, characterized in that the polyurethane controlled-release fertilizer coating material comprises The structural unit is obtained by crosslinking one or more polyester polyols prepared from furan dicarboxylic acid based on renewable raw materials with one or more isocyanates.

[0010] This invention introduces a furan ring structure into a polyurethane coating material system for the first time. Compared with the aromatic structure of benzene ring introduced in traditional methods, the furan ring has superior water resistance, which is beneficial to prolonging the release period of the coated controlled-release fertilizer. Furthermore, this invention preferentially uses furan dicarboxylic acid prepared from renewable raw materials as the source of furan ring, which not only improves the performance of the membrane material but also increases its biomass content, resulting in higher biocompatibility and ecological safety.

[0011] Preferably, the infrared spectrum of the polyurethane controlled-release fertilizer coating material is in the range of 1598-1600 cm⁻¹. -1 1220-1225cm -1 1070-1075cm -1 818-823 cm -1 764-768 cm -1 There is a characteristic peak at this location.

[0012] The polyurethane controlled-release fertilizer coating material of the present invention is obtained by crosslinking a polyester polyol based on bio-FDCA (Bio-FDCA), a renewable raw material, with an isocyanate. As can be seen from the infrared spectrum, the polyurethane controlled-release fertilizer coating material of the present invention exhibits characteristic absorptions of bio-FDCA, such as 1598-1600 cm⁻¹. -1 The stretching vibration peak of the furan ring C=C is located at 1220-1225 cm⁻¹. -1 There is a C=O stretching vibration of the ester group directly attached to the furan ring, 1070-1075 cm⁻¹. -1 The point represents the stretching vibration of COC on the furan ring, 818-823 cm. -1 764-768 cm -1 The CH out-of-plane bending vibrations corresponding to the benzene or furan rings in isocyanates, with 764-768 cm⁻¹ -1 The characteristic absorption at this location is mainly generated by the out-of-plane bending vibration of CH on the furan ring. Therefore, this invention uses a polyurethane coating material made from Bio-FDCA raw material at 764-768 cm⁻¹. -1 The characteristic absorption peak intensity is significantly greater than 818-823 cm⁻¹. -1 Place.

[0013] Preferably, the raw materials for preparing the polyester polyol include Bio-FDCA, one or more organic mono- or dicarboxylic acids, one or more polyols, and a catalyst.

[0014] The Bio-FDCA used in this invention is prepared from renewable raw materials such as furfural, furoic acid, furan, hexonic acid, fructose, glucose, and diethylene glycol.

[0015] Preferably, the raw materials for preparing the polyester polyol, by weight, include 4-40 parts of Bio-FDCA, 17-55 parts of organic mono- or dicarboxylic acid, 30-60 parts of polyol, and 0.05-0.2 parts of catalyst.

[0016] Preferably, the organic monocarboxylic or dicarboxylic acid is selected from one or more of the following: adipic acid, succinic acid, glutaric acid, sebacic acid, oleic acid, and acetic acid.

[0017] Preferably, the plant oleic acid is selected from one or more of oleic acid, linoleic acid, erucic acid, ricinoleic acid, soybean oleic acid, rapeseed oleic acid, arachidic acid, sunflower seed oleic acid, and palmitic acid.

[0018] Preferably, the polyol is selected from one or more of the following: diethylene glycol, butylene glycol, propylene glycol, pentanediol, hexanediol, diethylene glycol, and glycerol.

[0019] The ingredients used in this invention, including Bio-FDCA, organic monocarboxylic or dicarboxylic acids, and polyols, are all of biological origin or prepared from biologically derived materials.

[0020] Preferably, the catalyst is any one of organotitanate catalysts, organotin catalysts, and zinc acetate; more preferably, the organotitanate catalyst is any one of isopropyl titanate and tetrabutyl titanate; and the organotin catalyst is any one of dibutyltin oxide and dibutyltin dilaurate.

[0021] Preferably, the polyester polyol is prepared from Bio-FDCA, adipic acid, diethylene glycol, glycerol, and a catalyst; More preferably, the raw materials for preparing the polyester polyol, by weight, include 10-30 parts of Bio-FDCA, 17-40 parts of adipic acid, 35-60 parts of diethylene glycol, 0-20 parts of glycerol, and 0.05-0.2 parts of catalyst.

[0022] Preferably, the polyester polyol is prepared from Bio-FDCA, adipic acid, vegetable oleic acid, acetic acid, glycerol and a catalyst; More preferably, the raw materials for preparing the polyester polyol, by weight, include 10-20 parts of Bio-FDCA, 5-15 parts of adipic acid, 40-45 parts of vegetable oleic acid, 2-10 parts of acetic acid, 30-45 parts of glycerol, and 0.05-0.2 parts of catalyst.

[0023] Preferably, the polyester polyol is prepared from Bio-FDCA, adipic acid, butanediol, propylene glycol, and a catalyst; More preferably, the raw materials for preparing the polyester polyol, by weight, include 10-15 parts of Bio-FDCA, 40-50 parts of adipic acid, 33-38 parts of butanediol, 17-22 parts of propylene glycol, and 0.05-0.2 parts of catalyst.

[0024] Preferably, the amount of Bio-FDCA used is 4 to 40% by mass percentage of the polyester polyol.

[0025] More preferably, the amount of Bio-FDCA used is 10-30%; more preferably, the amount of Bio-FDCA used is 10-20%.

[0026] Preferably, the viscosity of the polyester polyol is 500~30000 mPa·s at 25°C.

[0027] More preferably, the viscosity of the polyester polyol is 1500~15000 mPa·s at 25°C.

[0028] Preferably, the polyester polyol is prepared by the following method: The raw materials are added to the reaction vessel, a catalyst is added, and the mixture is heated under reflux. After the reaction is completed, vacuum distillation is carried out until the acid value of the system drops below 2.0 mgKOH / g and the water mass fraction drops below 0.1%. The mixture is then cooled and discharged to obtain the final product.

[0029] Specifically, the polyester polyol is obtained by heating furanyl dicarboxylic acid, adipic acid, diethylene glycol, glycerol and catalyst based on renewable raw materials to 150~170℃ and refluxing for 5~10 hours, then heating to 200~240℃ and refluxing until the acid value drops below 5.0mgKOH / g, then cooling to 180~220℃ and vacuum distilling until the acid value drops below 2.0mgKOH / g and the water content is below 0.1%, and then cooling and discharging. The polyester polyol has a viscosity of 4000~10000 mPa·s and a hydroxyl value of 150~350mgKOH / g. Alternatively, the polyester polyol is obtained by: esterifying vegetable oleic acid, acetic acid, and glycerol at 160-240°C until the acid value drops below 10 mg KOH / g to obtain vegetable oleic acid glyceride; then adding furanyl dicarboxylic acid, adipic acid, and a catalyst based on renewable raw materials; heating to 150-170°C and refluxing for 5-10 hours; then heating to 200-240°C and refluxing until the acid value drops below 5.0 mg KOH / g; then cooling to 180-220°C and vacuum distilling until the acid value drops below 2.0 mg KOH / g and the water content is below 0.1%; and finally cooling and discharging the product. The polyester polyol has a viscosity of 7000-10000 mPa·s and a hydroxyl value of 200-400 mg KOH / g. Alternatively, the polyester polyol is prepared by heating furanyl dicarboxylic acid, adipic acid, butanediol, propylene glycol, and a catalyst based on renewable raw materials to 150-170°C and refluxing for 5-10 hours, then heating to 200-240°C and refluxing until the acid value drops below 5.0 mg KOH / g, then cooling to 180-220°C and vacuum distilling until the acid value drops below 2.0 mg KOH / g and the moisture content is below 0.1%, and then cooling and discharging. The polyester polyol has a viscosity of 4000-8000 mPa·s and a hydroxyl value of 200-400 mg KOH / g.

[0030] Preferably, the isocyanate has two or more isocyanate groups.

[0031] Preferably, the isocyanate comprises petroleum-based or bio-based polymethylene polyphenyl polyisocyanate; more preferably, it is selected from one or more of petroleum-based diphenylmethane diisocyanate (MDI), bio-based diphenylmethane diisocyanate, toluene diisocyanate (TDI), terephthalic diisocyanate, isophthalic dimethyl diisocyanate (XDI), cyclohexane diisocyanate (CHDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI); More preferably, the bio-based MDI is synthesized from bio-based aniline.

[0032] Preferably, the molar ratio of the hydroxyl groups of the polyester polyol to the NCO groups of the isocyanate is 1 to 1.05:1.

[0033] Another aspect of the present invention provides a method for applying the above-mentioned polyurethane controlled-release fertilizer coating material containing furan dicarboxylic acid based on renewable raw materials, the steps of which include: spraying and coating the polyester polyol and the isocyanate onto the surface of granular fertilizer, and crosslinking them in situ on the surface of the granular fertilizer to form a film, thereby obtaining polyurethane controlled-release fertilizer.

[0034] Preferably, the polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials accounts for 2 to 6% of the weight of the particles.

[0035] More preferably, the weight of the polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials accounts for 2 to 4% of the weight of the particles.

[0036] In another aspect, the present invention provides a product obtained by the above-described application method, wherein the product is a polyurethane-coated controlled-release fertilizer.

[0037] Compared with the prior art, the present invention has the following beneficial effects: 1. The polyurethane controlled-release fertilizer coating material of the present invention is a bio-based material with good biocompatibility, easy degradation, high ecological safety, green and environmentally friendly, which meets the development requirements of green chemistry and will not cause soil pollution.

[0038] 2. This invention innovatively designs a highly hydrophobic polyester polyol. In the system of this invention, only a small amount of Bio-FDCA needs to be added to significantly improve the hydrophobic sealing performance of the polyurethane material prepared by it. Thus, while extending the slow-release cycle of controlled-release fertilizer, it also takes into account the cost and has practical industrialization value.

[0039] 3. The polyester polyol synthesized by this invention has a suitable viscosity and can be used to form a film through an in-situ crosslinking process with isocyanate on the surface of fertilizer particles. It has excellent operability and is suitable for industrial-scale production.

[0040] 4. The polyurethane controlled-release fertilizer coating material of the present invention has good hydrophobicity and air tightness, as well as high strength and toughness. When coating fertilizer particles, a lower coating rate can be used, that is, a lower amount can achieve a controlled-release effect comparable to existing products on the market, further reducing the cost of using bio-based materials. 5. This invention is the first to apply Bio-FDCA to the field of controlled-release fertilizer coating materials, constructing a new bio-based controlled-release fertilizer coating material system that can effectively replace existing bio-based controlled-release fertilizers. Attached Figure Description

[0041] Figure 1 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Example 1; Figure 2 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Example 2; Figure 3 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Example 3; Figure 4 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Example 5; Figure 5 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Example 7; Figure 6 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Comparative Example 1; Figure 7 Infrared spectra of polyester polyol (top) and polyurethane controlled-release fertilizer coating material (bottom) in Comparative Example 2; Figure 8 This is a magnified view of the characteristic peaks of the infrared spectrum of the polyurethane controlled-release fertilizer coating material in Example 1; Figure 9 These are photographs of polyester polyol samples; where 1-7 correspond to the polyester polyols of Examples 1, 2, 3, 5, 7, and Comparative Examples 1 and 2, respectively. Figure 10 The images show photos of cured polyurethane film samples, where ag corresponds sequentially to the cured polyurethane films of the polyurethane controlled-release fertilizer coating materials of Examples 1, 2, 3, 5, 7, and Comparative Examples 1 and 2. Detailed Implementation

[0042] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention. Example

[0043] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 11 parts Bio-FDCA, 39 parts adipic acid, 40 parts diethylene glycol, 12 parts glycerol, and 0.1 parts zinc acetate catalyst. The isocyanate is petroleum-based MDI, purchased from Wanhua Chemical's PM-200.

[0044] The polyester polyol in this embodiment is prepared through the following steps: According to the above weight proportions, Bio-FDCA, adipic acid, diethylene glycol, and glycerol were added to a reaction vessel, along with a catalyst. The mixture was heated to 150°C and refluxed for 6 hours, then heated to 200°C and refluxed for another 6 hours. The acid value was monitored, and the reaction was stopped when the acid value dropped below 5.0 mg KOH / g. The mixture was then cooled to 180°C for vacuum distillation, with the vacuum level controlled at -0.065 MPa, until the acid value dropped below 2.0 mg KOH / g and the moisture content was below 0.1%. The mixture was then cooled and discharged to obtain the polyester polyol.

[0045] This embodiment also provides a method for applying the above-mentioned polyurethane controlled-release fertilizer coating material containing furan dicarboxylic acid based on renewable raw materials. The steps include: weighing 1 kg of granular urea with a particle size of 2.00~4.75 mm, adding it to a high-efficiency coating machine and heating it to 65°C; weighing the polyester polyol and isocyanate prepared in this embodiment, dividing them into four equal parts, each part containing 3.28 g of polyester polyol and 1.97 g of isocyanate, wherein the molar ratio of the hydroxyl groups of the polyester polyol to the NCO groups of the isocyanate is approximately 1:1. Each time, one part polyester polyol and one part isocyanate are mixed and sprayed onto the surface of granular urea. The polyurethane controlled-release fertilizer coating material crosslinks in situ on the surface of the granular urea to form a film. After mixing evenly, the next feeding is carried out. After repeating 4 times, it is cured for 5 minutes. 0.2% of the total mass of the mixture is added with paraffin to prevent adhesion. The mixture is cooled to 20°C and discharged to obtain polyurethane-coated controlled-release fertilizer. The amount of polyurethane controlled-release fertilizer coating material used is 2.1 wt% of the polyurethane-coated controlled-release fertilizer (coating rate).

[0046] This embodiment also provides a polyurethane-coated controlled-release fertilizer obtained by the above application method. Example

[0047] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 20 parts Bio-FDCA, 26 parts adipic acid, 27.25 parts diethylene glycol, 16 parts glycerol, and 0.05 parts dibutyltin dilaurate catalyst. The isocyanate is petroleum-based MDI, purchased from Wanhua Chemical's PM-200.

[0048] The preparation method of polyester polyol and the application method of polyurethane controlled-release fertilizer coating material in this embodiment are the same as in Example 1, except that each part of polyester polyol is 2.89g and each part of isocyanate is 2.36g. Example

[0049] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 30 parts Bio-FDCA, 17 parts adipic acid, 56 parts diethylene glycol, and 0.05 parts dibutyltin dilaurate catalyst. The isocyanate is bio-based MDI, purchased from BASF.

[0050] The preparation method of polyester polyol and the application method of polyurethane controlled-release fertilizer coating material in this embodiment are the same as in Example 1, except that each part of polyester polyol is 3.31g and each part of isocyanate is 1.94g. Example

[0051] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 5 parts Bio-FDCA, 48 parts adipic acid, 43 parts diethylene glycol, and 0.05 parts dibutyltin dilaurate catalyst. The isocyanate is petroleum-based MDI, purchased from Wanhua Chemical's PM-200.

[0052] The preparation method of polyester polyol and the application method of polyurethane controlled-release fertilizer coating material in this embodiment are the same as in Example 1, except that each part of polyester polyol is 3.80g and each part of isocyanate is 1.45g. Example

[0053] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 11.7 parts Bio-FDCA, 12 parts adipic acid, 41 parts soybean oleic acid, 6.7 parts acetic acid, 32.5 parts glycerol, and 0.1 parts zinc acetate catalyst. The isocyanate is petroleum-based MDI, purchased from Wanhua Chemical's PM-200.

[0054] The polyester polyol in this embodiment is prepared through the following steps: S1. Add soybean oleic acid, acetic acid and glycerol to the reaction vessel according to the above weight parts, heat to 220℃ to carry out the esterification reaction, monitor the acid value, and after the acid value drops to below 10mgKOH / g, cool down and discharge the material to obtain a yellow transparent viscous liquid, which is vegetable oleic acid glyceride, for later use; S2. Add the appropriate amount of Bio-FDCA and adipic acid to the vegetable oleic acid glyceride obtained in step S1, add the catalyst, heat to 170℃ and reflux for 5 hours, then raise the temperature to 220℃ and continue reflux for 6 hours; detect the acid value, and when the acid value drops below 5.0 mg KOH / g, stop the reaction, cool to 200℃ and perform vacuum distillation, controlling the vacuum degree at -0.065 MPa, until the acid value drops below 2.0 mg KOH / g and the water content is below 0.1%, then cool down and discharge the material to obtain the polyester polyol.

[0055] The application method of the polyurethane controlled-release fertilizer coating material in this embodiment is the same as in Example 1, except that each part of polyester polyol is 3.34g and each part of isocyanate is 1.91g. Example

[0056] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 17 parts Bio-FDCA, 10 parts adipic acid, 42 parts soybean oleic acid, 2.2 parts acetic acid, 44 parts glycerol, and 0.1 parts zinc acetate catalyst. The isocyanate is bio-based MDI, purchased from BASF.

[0057] The preparation method of the polyester polyol and the application method of the polyurethane controlled-release fertilizer coating material in this embodiment are the same as in Example 5, except that each part of polyester polyol is 2.79g and each part of isocyanate is 2.46g. Example

[0058] This embodiment provides a polyurethane controlled-release fertilizer coating material containing furanyl dicarboxylic acid based on renewable raw materials. The raw materials for its preparation include polyester polyol and isocyanate. The polyester polyol, by weight, comprises 11 parts Bio-FDCA, 45 parts adipic acid, 34 parts butanediol, 19 parts propylene glycol, and 0.1 parts zinc acetate catalyst. The isocyanate is petroleum-based MDI, purchased from Wanhua Chemical's PM-200.

[0059] The polyester polyol in this embodiment is prepared through the following steps: According to the above weight proportions, Bio-FDCA, adipic acid, butanediol, and propylene glycol are added to a reaction vessel, along with a catalyst. The mixture is heated to 150°C and refluxed for 4 hours, then heated to 200°C and refluxed for another 6 hours. The acid value is monitored, and the reaction is stopped when the acid value drops below 5.0 mg KOH / g. The mixture is then cooled to 180°C for vacuum distillation, with the vacuum level controlled at -0.065 MPa, until the acid value drops below 2.0 mg KOH / g and the moisture content is below 0.1%. The mixture is then cooled and discharged to obtain polyester polyol.

[0060] The application method of the polyurethane controlled-release fertilizer coating material in this embodiment is the same as in Embodiment 1.

[0061] Comparative Example 1 This comparative example provides a polyurethane controlled-release fertilizer coating material, the raw materials of which include polyester polyol and isocyanate; wherein the polyester polyol is prepared according to the method described in Example 5 of patent CN 113512172A, and the isocyanate is MDI, purchased from Wanhua Chemical's PM-200.

[0062] This comparative example also provides a method for applying the above-mentioned polyurethane controlled-release fertilizer coating material. The method is the same as in Example 1, except that each part of polyester polyol is 3.36g and each part of isocyanate is 1.89g.

[0063] Comparative Example 2 This comparative example provides a polyurethane controlled-release fertilizer coating material, the raw materials for which include polyester polyol and isocyanate; wherein the polyester polyol is polyether MN700 purchased from Lanxing Dongda, and the isocyanate is MDI, purchased from Wanhua Chemical PM-200.

[0064] This comparative example also provides a method for applying the above-mentioned polyurethane controlled-release fertilizer coating material. The method is the same as in Example 1, except that each part of polyester polyol is 3.32g and each part of isocyanate is 1.93g.

[0065] Performance testing 1. Infrared characterization The test samples of the polyurethane coating material used in the infrared standard were prepared by the following method: the polyester polyols and isocyanates of each example and comparative example were mixed with each other according to the weight ratio in the corresponding application method, and uniformly coated on the surface of a glass plate. The mixture was then cured at 60°C for 5 minutes to obtain a polyurethane film.

[0066] The polyester polyols of each embodiment and comparative example were thinly coated onto quartz plates and detected by ATR infrared spectroscopy. The corresponding polyurethane films were cut into 1cm × 1cm slices, and their infrared spectra were measured. The results are as follows: Figure 1-7 As shown.

[0067] 2. Viscosity test The viscosity of the polyester polyols in each embodiment was tested according to the standard method of GB / T12008.7-2010, and the results are recorded in Table 1.

[0068] 3. Hydroxyl value determination The hydroxyl value of the polyester polyols in each example was determined according to the phthalic anhydride method in accordance with GB / T12008.3-2009 standard, and the results are recorded in Table 1.

[0069] 4. Release cycle test Under conditions of 25°C, the release cycle of coated urea in Examples 1-7 and Comparative Examples 1-2 was tested using the static water extraction method. The release rate at 24 hours was taken as the initial release rate, and the number of days required for the cumulative nutrient release rate to reach 80% was taken as the release period. The results are recorded in Table 1.

[0070] Table 1 Polyol viscosity (mPa·s) 4350 8630 6440 8410 9480 7750 4230 / / Hydroxyl value of polyols (mgKOH / g) 248.1 339.3 243.6 157.9 236.6 366.4 249.3 266.9 240.4 Initial release rate (%) 0.92 0.87 0.58 1.23 0.15 0.21 0.77 0.36 3.6 Release period (days) 60 63 72 44 82 85 66 76 35 The results show that the polyurethane controlled-release fertilizer coating material prepared from the polyester polyol containing renewable furanyl dicarboxylic acid of this invention has superior controlled-release performance and a high bio-based carbon content. Considering cost factors, the system of this invention can still achieve a release period of 60 days or even more than 80 days, even with a low amount of furanyl dicarboxylic acid.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials, characterized in that, The polyurethane controlled-release fertilizer coating contains The structural unit is obtained by cross-linking one or more polyester polyols prepared from furan dicarboxylic acid based on renewable raw materials with one or more isocyanates; The polyester polyol is prepared from one of the following three raw material combinations: (1) prepared from furanyl dicarboxylic acid, adipic acid, diethylene glycol, glycerol and catalyst based on renewable raw materials; (2) prepared from furanyl dicarboxylic acid, adipic acid, vegetable oleic acid, acetic acid, glycerol and catalyst based on renewable raw materials; (3) prepared from furanyl dicarboxylic acid, adipic acid, butanediol, propylene glycol and catalyst based on renewable raw materials; The amount of furanyl dicarboxylic acid based on renewable raw materials is 4-40% by mass percentage of the polyester polyol. The resulting product has a viscosity of 4000~10000 mPa·s and a hydroxyl value of 150~400 mgKOH / g, making it suitable for spraying and coating on the surface of granular fertilizer and cross-linking into a film in situ.

2. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The infrared spectrum of the polyurethane controlled-release fertilizer coating is in the range of 1598-1600 cm⁻¹. -1 1220-1225 cm -1 1070-1075cm -1 818-823 cm -1 764-768 cm -1 There is a characteristic peak at this location.

3. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The raw materials for preparing the polyester polyol, by weight, include 4-40 parts by weight of furanyl dicarboxylic acid based on renewable raw materials, 17-55 parts by weight of adipic acid and other organic mono- or dicarboxylic acids, and 30-55 parts by weight of polyol.

4. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The polyester polyol is obtained by heating furanyl dicarboxylic acid, adipic acid, diethylene glycol, glycerol and catalyst based on renewable raw materials to 150~170℃ and refluxing for 5~10 hours, then heating to 200~240℃ and refluxing until the acid value drops below 5.0mgKOH / g, then cooling to 180~220℃ and vacuum distilling until the acid value drops below 2.0mgKOH / g and the moisture content is below 0.1%, and then cooling and discharging. The polyester polyol has a viscosity of 4000~10000 mPa·s and a hydroxyl value of 150~350mgKOH / g.

5. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The polyester polyol is obtained by esterification of vegetable oleic acid, acetic acid, and glycerol at 160-240°C until the acid value drops below 10 mg KOH / g to obtain vegetable oleic acid glyceride. Then, furanyl dicarboxylic acid, adipic acid, and a catalyst based on renewable raw materials are added and heated to 150-170°C for reflux reaction for 5-10 hours. Then, the temperature is raised to 200-240°C for reflux reaction until the acid value drops below 5.0 mg KOH / g. After cooling to 180-220°C, vacuum distillation is carried out until the acid value drops below 2.0 mg KOH / g and the moisture content is below 0.1%. The polyester polyol has a viscosity of 7000-10000 mPa·s and a hydroxyl value of 200-400 mg KOH / g.

6. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The polyester polyol is obtained by heating furan dicarboxylic acid, adipic acid, butanediol, propylene glycol, and a catalyst based on renewable raw materials to 150-170°C and refluxing for 5-10 hours, then heating to 200-240°C and refluxing until the acid value drops below 5.0 mg KOH / g, then cooling to 180-220°C and vacuum distilling until the acid value drops below 2.0 mg KOH / g and the moisture content is below 0.1%, and then cooling and discharging. The polyester polyol has a viscosity of 4000-8000 mPa·s and a hydroxyl value of 200-400 mg KOH / g.

7. The polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials according to claim 1, characterized in that, The isocyanate is selected from one or more of the following: petroleum-based or bio-based polymethylene polyphenyl polyisocyanate, petroleum-based diphenylmethane diisocyanate, bio-based diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, isophthalic dimethyl diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

8. A method for applying a polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials, as described in any one of claims 1-7, characterized in that, The steps include: spraying the polyester polyol and the isocyanate onto the surface of the granular fertilizer, and cross-linking them in situ on the surface of the granular fertilizer to form a film, thereby obtaining a polyurethane controlled-release fertilizer.

9. The application method according to claim 8, characterized in that, The weight of the polyurethane controlled-release fertilizer coating containing furanyl dicarboxylic acid based on renewable raw materials accounts for 2-6% of the weight of the granular fertilizer.

10. A product obtained by the application method according to claim 8 or 9, characterized in that, The product is a polyurethane-coated controlled-release fertilizer.

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