Halogen-free bio-based flame-retardant polyester polyol, and preparation method and application thereof

Abstract

The application discloses a kind of halogen-free bio-based flame-retardant polyester polyols, by sik and monobasic acid, dibasic acid mixed preparation, using the cyclic structure of sik and its three functional degree hydroxyl structure can prepare the crosslinking degree moderate polyester polyols, the flame-retardant polyester polyols prepared in V-0 grade flame-retardant test shows excellent, also reduce the dependence on toxic flame retardant;In addition, the cyclic structure of sik and high nitrogen content help material form more dense crosslinking network after forming, give material better tensile strength and heat resistance, mechanical properties and flame-retardant effect are considered simultaneously.Part of trimethylolpropane can be used to replace sik, and cost and performance are considered.The application also provides an application of halogen-free bio-based flame-retardant polyester polyols, which is mixed with isocyanate to prepare polyurethane material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flame-retardant materials, and particularly relates to a halogen-free bio-based flame-retardant polyester polyol and a preparation method and application thereof. BACKGROUND

[0002] Traditional flame-retardant technology mainly relies on external flame retardants, such as halogen compounds (bromine series, chlorine series) or phosphate ester flame retardants. Although these flame retardants can effectively improve the flame-retardant performance of materials, their use has brought serious environmental and health hazards. Halogen-based flame retardants release toxic gases (such as dioxins and hydrogen halides) during combustion, which not only harm human health but also have long-term negative effects on the ecological system.

[0003] With the increasingly stringent international environmental protection regulations, many countries and regions have begun to restrict the use of halogen-based flame retardants, which has promoted the research, development and application of halogen-free and additive-free flame-retardant materials. Bio-based polyols have gradually become important candidate materials to replace traditional petrochemical-based polyols due to their renewability and environmental friendliness. In addition, bio-based polyols are mainly derived from renewable resources such as plant oils, starch and cellulose, and their preparation process has low carbon emissions, which is in line with the concept of low-carbon economy and green chemistry promoted globally. Currently, bio-based polyols have been increasingly widely used in the fields of chemical industry and material science, especially in the polyurethane (PU) industry. However, polyurethane materials generally have high flammability, which limits their widespread use in application fields such as construction, transportation, electronic equipment and other fields requiring high flame-retardant performance. Therefore, developing bio-based polyol materials with high efficient flame-retardant performance has become an important direction of current research.

[0004] CN115785370A discloses a bio-based polyol and a preparation method of a bio-based flame-retardant polyurethane, which includes the following steps: reacting allyl phosphoric acid diethyl ester with 3-mercapto-1,2-propanediol to prepare a phosphorus-containing flame-retardant polyol, and reacting plant oil with 3-mercapto-1,2-propanediol to prepare a bio-based polyol; and reacting the phosphorus-containing flame-retardant polyol, the bio-based polyol and diisocyanate to prepare the bio-based flame-retardant polyurethane. However, the polyurethane elastomer prepared from this bio-based polyol has poor mechanical properties.

[0005] CN117402312A discloses a bio-based flame-retardant polyol, specifically relates to a castor oil-based flame-retardant microcellular polyurethane elastomer and a preparation method thereof. The invention uses castor oil as raw material, and prepares the flame-retardant castor oil polyol through the synthesis route of epoxidation and ring-opening. The castor oil flame-retardant polyol grafted with DOPO is applied to the field of polyurethane elastomers, and part of the conventional chain extender is replaced by part of the terminal hydroxyl organosilicon chain extender. Through the synergistic effect of the terminal hydroxyl organosilicon chain extender and the castor oil flame-retardant polyol at a certain proportion, the prepared polyurethane elastomer has excellent flame-retardant performance and mechanical properties, and good resilience. However, this flame-retardant polyol needs to add a large amount of polyol to play a flame-retardant effect, and the prepared polyurethane has low bio-based content and poor mechanical properties.

[0006] In summary, the introduction of flame-retardant elements or flame-retardant agents (such as phosphorus or nitrogen) changes the molecular structure of the polyol, and the flame-retardant agent destroys and increases the brittleness of the material. Especially for polyol materials with high flame-retardant performance, the crosslinking degree of the molecules or the rigidity of the molecular chains is too high, which makes the material perform poorly in mechanical properties such as impact and tensile. Therefore, it is still a focus of technical optimization to achieve an ideal balance between flame-retardant performance and mechanical properties. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a halogen-free bio-based flame-retardant polyester polyol and a preparation method thereof, which is prepared from tris(2-hydroxyethyl) isocyanurate (sike) and bio-based monobasic acid and dibasic acid, to solve the problems of insufficient environmental protection, high cost, and unbalanced flame-retardant performance and mechanical properties of existing flame-retardant materials.

[0008] First part:

[0009] A halogen-free bio-based flame-retardant polyester polyol, comprising at least one of formula I and formula II,

[0010]

[0011] wherein R1 is a C2-C17 hydrocarbon group; R2 is a C2-C16 alkyl group; R3 is a C3-C5 alkyl group or a C2-C8 alkyl group with an ester group, wherein the ester group is R1COO-; l is an integer from 2 to 7, m is an integer from 2 to 7, and n is an integer from 1 to 7. Preferably, l is 2 or 3, m is 2 or 3, and n is 1 or 2.

[0012] Tris(2-hydroxyethyl) isocyanurate (SEPPIC) has a cyclic structure itself, which endows it with excellent thermal insulation, thermal stability and mechanical properties. The high nitrogen content of SEPPIC can generate inert gas nitrogen and water during combustion, greatly preventing the continuation of the combustion reaction and enhancing the self-retardant property of the material; moreover, the cyclic structure of SEPPIC can also effectively block heat transfer, further improving the flame retardant performance of the material.

[0013] Meanwhile, the cyclic structure of SEPPIC and its trifunctional hydroxyl structure can prepare polyester polyols with moderate crosslinking degree (as shown in Formula I), which take into account both mechanical properties and flame retardant effect. The cyclic structure of SEPPIC and the high nitrogen content help the material to form a more compact crosslinking network after forming, endowing the material with better tensile strength and heat resistance; the three-hydroxyl structure of SEPPIC significantly enhances the mechanical properties of polyester polyols, especially in key properties such as elasticity and toughness.

[0014] In addition, since SEPPIC itself provides a strong flame-retardant mechanism, the bio-based polyester polyol in the present application does not require additional chemical flame retardants, which not only reduces the use of toxic substances, but also avoids the impact of additives on the mechanical properties of the material. Therefore, the flame retardant performance and mechanical properties of the present application can remain stable and consistent, and are particularly suitable for application scenarios with high requirements for flame retardant and mechanical properties, such as building materials and automotive interiors.

[0015] Second part:

[0016] A preparation method of a halogen-free bio-based flame-retardant polyester polyol as described in the first part, comprising the following steps:

[0017] Mixing SEPPIC and monobasic acid with a molar ratio of 1:(0.4-1.3), adding a first catalyst, vacuumizing, reacting at a temperature of 180-240℃ for 3-16h, then adding dibasic acid to continue reacting for 3-16h, the molar ratio of the amount of dibasic acid added to SEPPIC being (0.2-0.9):1, to obtain Formula I of the halogen-free bio-based flame-retardant polyester polyol; the first catalyst includes at least one of tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, titanate, tetrabutyl zirconate, tetraisopropyl zirconate, dibutyltin dilaurate and antimony zinc oxide.

[0018] The present application introduces nitrogen elements in the molecular structure, which will generate nitrogen and water during combustion, endowing the material with self-retardant property. Experimental results show that the prepared flame-retardant polyester polyol performs excellently in V-0 level flame retardant test, while maintaining high mechanical properties. This invention not only reduces the flammability of the material, but also reduces the dependence on toxic flame retardants, meeting the needs of sustainable development, and has good application prospects in high-demand fields such as building and automotive interiors; when synthesizing polyester polyols, too low temperature does not cause reaction, and too high temperature will cause product decomposition.

[0019] A method for preparing the halogen-free bio-based flame-retardant polyester polyol as described in the first part, comprising the following steps:

[0020] The sebacic acid and the small molecule polyol are blended in a molar ratio of 1:(0.1-1.5) to obtain a blend A, then the blend A and a monobasic acid are mixed in a molar ratio of 1:(0.4-1.3), a first catalyst is added, vacuum is drawn, and reaction is carried out at a temperature of 180-240℃ for 3-16h, then a dibasic acid is added for further reaction for 3-16h, the molar ratio of the amount of the dibasic acid added to the blend A is (0.2-0.9):1, to obtain the halogen-free bio-based flame-retardant polyester polyol of Formula II; the small molecule polyol includes at least one of 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, glycerol, trimethylolpropane, trimethylolethane, sorbitol, and pentaerythritol; the first catalyst includes at least one of tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, titanate, tetrabutyl zirconate, tetraisopropyl zirconate, dibutyl tin dilaurate, and antimony zinc oxide.

[0021] In order to reduce the production cost, part of the sebacic acid is replaced by a small molecule polyol, and in the embodiments of the present application, trimethylolpropane (TMP) is used to replace the sebacic acid. TMP and sebacic acid both have three functional hydroxyl groups, can react with organic acids, and TMP can also reduce the viscosity of the flame-retardant polyol, facilitating subsequent construction. The flame-retardant performance and mechanical performance of the bio-based flame-retardant polyester polyol (as shown in Formula II) prepared by block blending of sebacic acid and TMP through covalent bond still remain at a high level, achieving a balance between cost and performance.

[0022] As a preferred solution, the monobasic acid includes at least one of dodecanoic acid, acetic acid, butyric acid, hexanoic acid, decanoic acid, linoleic acid, linolenic acid, oleic acid, and stearic acid; the dibasic acid includes at least one of pimelic acid, glutaric acid, pivalic acid, a ring-opening product of maleic anhydride, azelaic acid, sebacic acid, 2,5-furandicarboxylic acid, terephthalic acid, dimer acid, adipic acid, and sebacic acid. More preferably, the monobasic acid is selected from oleic acid and stearic acid, and the dibasic acid is selected from adipic acid and sebacic acid. The use of bio-based oleic acid and stearic acid improves the bio-based content of the product, reduces the use of petrochemical-based materials, and reduces carbon emissions. Compared with stearic acid and oleic acid, i.e. compared with alkanoic acid and alkenoic acid, the elongation at break of the prepared flame-retardant polyester polyol is increased, the breaking stress is high, and the flame-retardant effect is not affected. The use of bio-based adipic acid and sebacic acid improves the bio-based content of the product, reduces the use of petrochemical-based materials, and reduces carbon emissions; as the carbon chain of the dibasic acid becomes longer, the elongation at break of the flame-retardant polyester polyol is increased, the breaking stress is decreased, the overall flexibility is increased, and the flame-retardant effect is not affected.

[0023] As a preferred solution, the diacid is added when the acid value is less than 3 mg KOH / g, and then the reaction is stopped when the acid value is less than 3 mg KOH / g and the hydroxyl value reaches 40-70 mg KOH / g. If the acid value and hydroxyl value content are too high or too low, the obtained polyester polyol will cause poor mechanical properties and poor flame retardant properties in the subsequent synthesis of polyurethane.

[0024] Third part:

[0025] A polyurethane material prepared from the halogen-free bio-based flame-retardant polyester polyol of the first part.

[0026] Fourth part:

[0027] A method for preparing a polyurethane material as described in the third part, comprising the following steps:

[0028] Mixing the first polyol with isocyanate and reacting at 50-90°C for 1-3h to obtain a polyurethane prepolymer;

[0029] Mixing the polyurethane prepolymer with the second polyol, adding a second catalyst, stirring and mixing, and reacting at 60-120°C for 10-16h to obtain a polyurethane material;

[0030] The first polyol includes a halogen-free bio-based flame-retardant polyester polyol; the molar ratio of the hydroxyl group in the first polyol to the NCO group in the isocyanate is 1:(1-1.3); the second catalyst includes at least one of organic tin, organic amine, organic mercury and organic bismuth; the content of sike is ≥12wt.%, wherein the content of sike refers to the weight percentage of the raw material sike involved in the preparation reaction of the halogen-free bio-based flame-retardant polyester polyol in the weight of the polyurethane material.

[0031] In the synthesis of polyurethane prepolymer, too low temperature will cause slow reaction and increase cost, too high temperature will cause violent polymerization, too short time will not fully polymerize, and too long time will increase cost; in the synthesis of polyurethane material, too low temperature will cause slow reaction and increase cost, too high temperature will cause poor mechanical properties and poor flame retardant properties of the product, too low time will cause poor performance of the product, and too high time will increase cost.

[0032] As a preferred solution, the isocyanate includes at least one of Wanhua Chemical PM200, isophorone diisocyanate (IPDI) and 4,4ˋ-diphenyl methane diisocyanate (MDI). It is commonly used in industry, has good yellowing resistance and low price.

[0033] As a preferred solution, the second catalyst is added in an amount of 0.001-0.1wt.% of the polyurethane prepolymer.

[0034] As a preferred solution, the second polyol includes at least one of 1,4-butanediol (BDO), ethylene glycol (EG), diethylene glycol (DEG), 1,3-propanediol (PDO), and 2-methyl-1,3-propanediol (MPDO), and the molar ratio of the polyurethane prepolymer to the polyol is 1:1-1.3. The second polyol with small molecules is used as a chain extender of the polyurethane. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 IR characterization chart of FR01, TMP-polyol and FR01-b-TMP-2;

[0036] Figure 2 Stress-strain curve chart of samples 1-9;

[0037] Figure 3 Stress-strain curve chart of samples 10-11;

[0038] Figure 4 Stress-strain curve chart of samples 12-14;

[0039] Figure 5 Stress-strain curve chart of samples 15-16;

[0040] Figure 6 Stress-strain curve chart of samples 17-19;

[0041] Figure 7 Stress-strain curve chart of samples 13 and 20. DETAILED DESCRIPTION

[0042] A preparation method of a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0043] A seco and a monobasic acid with a molar ratio of 1:(0.4-1.3) are mixed, a first catalyst is added, vacuum is extracted, and reaction is carried out at a temperature of 180-240℃ for 3-16h. When the acid value is lower than 3mg KOH / g, a dibasic acid is added to continue the reaction for 3-16h. The molar ratio of the added amount of the dibasic acid to the seco is (0.2-0.9):1. When the acid value is lower than 3mg KOH / g and the hydroxyl value reaches 40-70mg KOH / g, the reaction is ended to obtain the halogen-free bio-based flame-retardant polyester polyol (as shown in Formula I). The first catalyst includes at least one of tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, titanate, tetrabutyl zirconate, tetraisopropyl zirconate, dibutyl tin dilaurate, and antimony zinc oxide.

[0044]

[0045] The sec and monomer polyol is blended with a molar ratio of 1:(0.1-1.5) to obtain a blend A, then the blend A and a monobasic acid are mixed with a molar ratio of 1:(0.4-1.3), a first catalyst is added, vacuum is drawn, and the reaction is carried out at a temperature of 180-240°C for 3-16h, when the acid value is less than 3mg KOH / g, a dibasic acid is added to continue the reaction for 3-16h, the molar ratio of the dibasic acid addition amount to the blend A is (0.2-0.9):1, when the acid value is less than 3mg KOH / g and the hydroxyl value reaches 40-70mg KOH / g, the reaction is ended to obtain the halogen-free bio-based flame-retardant polyester polyol (as shown in Formula II). The monomer polyol includes at least one of 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, glycerol, trimethylolpropane, trimethylolethane, sorbitol, and pentaerythritol; and the first catalyst includes at least one of tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, titanium ester, tetrabutyl zirconate, tetraisopropyl zirconate, dibutyl tin dilaurate, and antimony zinc oxide.

[0046]

[0047] wherein R1 is a C2-C17 hydrocarbon group; R2 is a C2-C16 alkyl group; R3 is a C3-C5 alkyl group or a C2-C8 alkyl group with an ester group attached, wherein the ester group is R1COO-; I is an integer from 2 to 7, m is an integer from 2 to 7, and n is an integer from 1 to 7. Preferably, I is 2 or 3, m is 2 or 3, and n is 1 or 2.

[0048] A method for preparing a polyurethane material, comprising the following steps:

[0049] The halogen-free bio-based flame-retardant polyester polyol is mixed with isocyanate, and the reaction is carried out at 50-90°C for 1-3h to obtain a polyurethane prepolymer;

[0050] The polyurethane prepolymer is mixed with a polyol, a second catalyst is added, and the mixture is stirred and reacted at 60-120°C for 10-16h to obtain a polyurethane material;

[0051] wherein the halogen-free bio-based flame-retardant polyester polyol, based on hydroxyl groups, the isocyanate, based on NCO groups, the molar ratio of the hydroxyl groups to the NCO groups is 1:1.05; the second catalyst comprises at least one of dibutyltin dilaurate, dibutyltin dioctoate, organotin trichloride, triethylenediamine, dimethylaminoethanol, N-methylmorpholine, bis[2-(dimethylamino)ethyl]ether, phenylmercury acetate, phenylmercury sulfate, bismuth bis(2-ethylhexanoate), tris(2-ethylhexanoate) bismuth, and bismuth-zinc complex catalyst; the sebacic acid content is ≥12 wt.%, wherein the sebacic acid content refers to the weight percentage of the raw material sebacic acid involved in the preparation reaction of the halogen-free bio-based flame-retardant polyester polyol in the weight of the polyurethane material.

[0052] The isocyanate comprises at least one of Wanhua Chemical PM200, isophorone diisocyanate (IPDI), and 4,4'-diphenylmethane diisocyanate (MDI); the second catalyst is added in an amount of 0.1-1.0 wt.% of the polyurethane prepolymer; the polyol comprises at least one of 1,4-butanediol (BDO), ethylene glycol (EG), diethylene glycol (DEG), 1,3-propanediol (PDO), and 2-methyl-1,3-propanediol (MPDO), and the molar ratio of the polyurethane prepolymer to the polyol is 1:1-1.3.

[0053] Example 1

[0054] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0055] Mixing 187.5 g of vegetable oil acid and 173.4 g of sebacic acid, adding tetrabutyl titanate as a catalyst, vacuumizing, and reacting at a temperature of 180-240°C for 3-16 h; then adding 67.8 g of adipic acid, continuing vacuumizing, and reacting for 3-16 h to prepare a halogen-free bio-based flame-retardant polyester polyol FR01; after the reaction is completed, the acid value and the hydroxyl value are measured, and after the requirements are met, the product is packaged.

[0056] The FR01 is characterized by infrared spectroscopy (FTIR) analysis, and the characterization results are shown in FIG. 1. Figure 1 In the spectrum, the characteristic absorption peak of the carbonyl group (C=O) appears in the range of 1650-1780 cm-1, indicating that the esterification reaction of the hydroxyl groups and the carboxylic acid groups in the raw materials has occurred. At the same time, a wide peak absorption is observed in the characteristic range of 3200-3600 cm-1 of the terminal hydroxyl group, further proving that the hydroxyl functional groups are retained at both ends of the polyol molecules. This result confirms the completion of the esterification reaction and the characteristic structure of the polyol, and the structural formula of the FR01 is shown as Formula I.

[0057]

[0058]

[0059] In addition, the end point of the reaction is determined by hydroxyl value and acid value titration method. The experimental results show that, with the progress of the reaction, the acid value gradually decreases, and the hydroxyl value gradually increases, and finally both are close to the theoretical design value, further verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0060] Example 2

[0061] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0062] Mix 187.5g of plant oil acid and 173.4g of seco, add titanium tetrabutoxide as catalyst, vacuumize, react at a temperature of 180-240℃ for 3-16h, then add 93.8g of sebacic acid, continue vacuumizing, react for 3-16h to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-Dec, after the reaction is completed, measure the acid value and hydroxyl value, and after meeting the requirements, perform packaging.

[0063] The end point of the reaction is determined by hydroxyl value and acid value titration method. The experimental results show that, with the progress of the reaction, the acid value gradually decreases, and the hydroxyl value gradually increases, and finally both are close to the theoretical design value, verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0064] Example 3

[0065] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0066] Mix 188.8g of stearic acid and 173.4g of seco, add titanium tetrabutoxide as catalyst, vacuumize, react at a temperature of 180-240℃ for 3-16h, then add 67.8g of adipic acid, continue vacuumizing, react for 3-16h to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-Stc, after the reaction is completed, measure the acid value and hydroxyl value, and after meeting the requirements, perform packaging.

[0067] The end point of the reaction is determined by hydroxyl value and acid value titration method. The experimental results show that, with the progress of the reaction, the acid value gradually decreases, and the hydroxyl value gradually increases, and finally both are close to the theoretical design value, verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0068] Example 4

[0069] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0070] Mix 187.5 g of vegetable oil acid, 86.7 g of secco and 44.4 g of TMP, add tetrabutyl titanate as catalyst, vacuumize, react at a temperature of 180-240°C for 3-16 h, then add 67.8 g of adipic acid, continue vacuumizing, react for 3-16 h to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-b-TMP-1. After the reaction is completed, the acid value and the hydroxyl value are determined, and after meeting the requirements, the product is packaged.

[0071] The end point of the reaction is determined by hydroxyl value and acid value titration method. The experimental results show that as the reaction proceeds, the acid value gradually decreases, and the hydroxyl value gradually increases, and finally both are close to the theoretical design value, further verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0072] Example 5

[0073] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0074] Mix 187.5 g of vegetable oil acid, 86.7 g of secco and 44.4 g of TMP, add tetrabutyl titanate as catalyst, vacuumize, react at a temperature of 180-240°C for 3-16 h, then add 67.8 g of adipic acid, continue vacuumizing, react for 3-16 h to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-b-TMP-1. After the reaction is completed, the acid value and the hydroxyl value are determined, and after meeting the requirements, the product is packaged.

[0075] The FR01-b-TMP-2 is characterized by infrared spectrum (FTIR) analysis, and the characterization results are shown in Figure 1 In the spectrum, the characteristic absorption peak of carbonyl (C=O) appears in the range of 1650-1780 cm-1, indicating that the esterification reaction has occurred between the hydroxyl groups and the carboxylic acid groups in the raw materials. At the same time, a wide peak absorption is observed in the characteristic range of 3200-3600 cm-1 of the terminal hydroxyl group, further proving that the hydroxyl functional groups are retained at both ends of the polyol molecule. This result confirms the completion of the esterification reaction and the characteristic structure of the polyol, and the structure of FR01-b-TMP-2 is shown in formula II.

[0076]

[0077] In addition, the end point of the reaction is determined by hydroxyl value and acid value titration method. The experimental results show that as the reaction proceeds, the acid value gradually decreases, and the hydroxyl value gradually increases, and finally both are close to the theoretical design value, further verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0078] Example 6

[0079] A method for preparing a halogen-free bio-based flame-retardant polyester polyol, comprising the following steps:

[0080] 187.5g of vegetable oleic acid, 60.7g of cyproconazole and 57.9g of TMP were mixed, and tetrabutyl titanate was added as a catalyst. The mixture was then vacuumed and reacted at 180-240℃ for 3-16 hours. Then, 67.8g of adipic acid was added, and the mixture was vacuumed again and reacted for another 3-16 hours to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-b-TMP-3. After the reaction was completed, the acid value and hydroxyl value were measured. If the requirements were met, the mixture was packaged.

[0081] The endpoint of the reaction was determined by titration using hydroxyl and acid values. Experimental results showed that as the reaction proceeded, the acid value gradually decreased while the hydroxyl value gradually increased, eventually approaching the theoretical design values, further verifying the completion of the esterification reaction and the formation of the polyol structure.

[0082] Example 7

[0083] A method for preparing a halogen-free bio-based flame-retardant polyester polyol includes the following steps:

[0084] 75.1g of vegetable oleic acid, 69.4g of saccharide, and 35.9g of BDO were mixed, and tetrabutyl titanate was added as a catalyst. The mixture was then vacuum-sealed and reacted at 180–240°C for 3–16 hours. Then, 67.8g of adipic acid was added, and the mixture was vacuum-sealed again for another 3–16 hours to finally prepare halogen-free bio-based flame-retardant polyester polyol FR01-b-BDO-4. After the reaction was completed, the acid value and hydroxyl value were measured, and the mixture was packaged after meeting the requirements.

[0085] The endpoint of the reaction was determined by titration using hydroxyl and acid values. Experimental results showed that as the reaction proceeded, the acid value gradually decreased while the hydroxyl value gradually increased, eventually approaching the theoretical design values, further verifying the completion of the esterification reaction and the formation of the polyol structure.

[0086] Comparative Example 1

[0087] A method for preparing the polyol TMP-polyol includes the following steps:

[0088] 187.5g of vegetable oleic acid and 89.1g of TMP were mixed, and tetrabutyl titanate was added as a catalyst. The mixture was then vacuumed and reacted at 180-240℃ for 3-16 hours. Then, 67.8g of adipic acid was added, and the mixture was vacuumed again for another 3-16 hours to finally prepare the polyol TMP-polyol. After the reaction was completed, the acid value and hydroxyl value were measured. Once the requirements were met, the mixture was packaged.

[0089] TMP-polyol was characterized by Fourier transform infrared spectroscopy (FTIR), and the characterization results are as follows: Figure 1The characteristic absorption peak of carbonyl (C=0) appeared in the range of 1650-1780 cm"1in the spectrum, indicating that the esterification reaction of hydroxyl and carboxylic acid groups in the raw material had occurred. At the same time, a broad peak absorption was observed in the characteristic range of 3200-3600 cm"1of the terminal hydroxyl group, further proving that the hydroxyl functional group was retained at both ends of the polyol molecule. This result confirmed the completion of the esterification reaction and the formation of the characteristic structure of the polyol.

[0090] In addition, the end point of the reaction was determined by hydroxyl value and acid value titration method. The experimental results showed that as the reaction proceeded, the acid value gradually decreased, while the hydroxyl value gradually increased, and finally both approached the theoretical design value, further verifying the completion of the esterification reaction and the formation of the structure of the polyol.

[0091] A method for preparing a polyurethane material, comprising the following steps:

[0092] Take 4.5 g TMP-polyol polyol, 1.4 g PM200, mix at 80°C for 2h, to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g BDO, add 0.06 wt.% organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 1.

[0093] Comparative Example 2

[0094] A method for preparing a polyurethane material, comprising the following steps:

[0095] Take 1.1 g FR01 polyol prepared in Example 1, 3.6 g TMP-polyol polyol prepared in Comparative Example 1, 1.4 g PM200, mix at 80°C for 2h, to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g BDO, add 0.06 wt.% organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 2.

[0096] Comparative Example 3

[0097] A method for preparing a polyurethane material, comprising the following steps:

[0098] Take 1.96 g FR01 polyol prepared in Example 1, 2.9 g TMP-polyol polyol prepared in Comparative Example 1, 1.4 g PM200, mix at 80°C for 2h, to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g BDO, add 0.06 wt.% organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 3.

[0099] Comparative Example 4

[0100] A method of making a polyurethane material, comprising the steps of:

[0101] Take 2.2 g of FR01 polyol prepared in Example 1, 2.7 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 4.

[0102] Example 8

[0103] A method of making a polyurethane material, comprising the steps of:

[0104] Take 2.5 g of FR01 polyol prepared in Example 1, 2.5 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 5.

[0105] Example 9

[0106] A method of making a polyurethane material, comprising the steps of:

[0107] Take 2.8 g of FR01 polyol prepared in Example 1, 2.3 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 6.

[0108] Example 10

[0109] A method of making a polyurethane material, comprising the steps of:

[0110] Take 3.4 g of FR01 polyol prepared in Example 1, 1.8 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 7.

[0111] Example 11

[0112] A process for preparing a polyurethane material comprising the steps of:

[0113] Take 5.6 g of FR01 polyol prepared in Example 1, 1.4 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 9.

[0114] Example 12

[0115] A process for preparing a polyurethane material comprising the steps of:

[0116] Take 5.6 g of FR01 polyol prepared in Example 1, 1.4 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 9.

[0117] Example 13

[0118] A process for preparing a polyurethane material comprising the steps of:

[0119] Take 5.8 g of FR01-Dec polyol prepared in Example 2, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 10.

[0120] Example 14

[0121] A process for preparing a polyurethane material comprising the steps of:

[0122] Take 5.7 g of FR01-Stc polyol prepared in Example 3, 1.4 g of PM200, mix, react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 11.

[0123] Example 15

[0124] A process for preparing a polyurethane comprising the steps of:

[0125] Take 5 g of FR01-b-TMP-1 polyol prepared in Example 4, 1.4 g of PM200, mix and react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, and add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 12.

[0126] Example 16

[0127] A method for preparing a polyurethane material, comprising the steps of:

[0128] Take 4.9 g of FR01-b-TMP-2 polyol prepared in Example 5, 1.4 g of PM200, mix and react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, and add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 13.

[0129] Comparative Example 5

[0130] A method for preparing a polyurethane material, comprising the steps of:

[0131] Take 4.8 g of FR01-b-TMP-3 polyol prepared in Example 6, 1.4 g of PM200, mix and react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, and add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 14.

[0132] Example 17

[0133] A method for preparing a polyurethane material, comprising the steps of:

[0134] Take 2.5 g of FR01 polyol prepared in Example 1, 2.5 g of TMP-polyol polyol prepared in Comparative Example 1, 1.2 g of isophorone diisocyanate (IPDI), mix and react at 80 °C for 2 h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, and add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16 h to obtain sample 15.

[0135] Example 18

[0136] A method for preparing a polyurethane material, comprising the steps of:

[0137] Take 2.5 g of FR01 polyol prepared in Example 1, 2.5 g of TMP-polyol polyol prepared in Comparative Example 1, 1.3 g of 4,4'-diphenyl methane diisocyanate (MDI), react at 80°C for 2h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 16.

[0138] Comparative Example 6

[0139] A method for preparing a polyurethane material, comprising the following steps:

[0140] Take 5.4 g of FR01 polyol prepared in Example 1, 3.5 g of TMP-polyol polyol prepared in Comparative Example 1, 1.4 g of PM200, mix, react at 80°C for 2h to obtain a polyurethane prepolymer, then add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 17.

[0141] Comparative Example 7

[0142] A method for preparing a polyurethane, comprising the following steps:

[0143] Take 4.3 g of FR01 polyol prepared in Example 1, 2.7 g of PM200, mix, react at 80°C for 2h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.1 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 18.

[0144] Comparative Example 8

[0145] A method for preparing a polyurethane material, comprising the following steps:

[0146] Take 1.8 g of FR01 polyol prepared in Example 1, 1.3 g of PM200, mix, react at 80°C for 2h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.3 g of BDO, add 0.06 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 19.

[0147] Example 19

[0148] A method for preparing a polyurethane, comprising the following steps:

[0149] Take 4.5 g of FR01-b-BDO-4 polyol prepared in Example 7, 1.4 g of PM200, mix and react at 80℃ for 2h to obtain a polyurethane prepolymer, then mix the obtained polyurethane prepolymer with 0.2 g of BDO, add 0.6 wt.% of organic tin catalyst, blend in a high-speed blender, pour into a mold, and cure for 10-16h to obtain sample 20.

[0150] Take samples 1-20 for flame retardant test and mechanical property test, the stress-strain curve of the mechanical property test is as shown in Figures 2-7 and Table 1, and the flame retardant properties and mechanical properties of samples 1-20 are shown in Table 1. Among them, the test standard of flame retardant is GB / T2408-2021, and the test standard of mechanical property is GB / T 528-2009. The expected flame retardant properties of the PU prepared by the application reach V-0 level, the Young's modulus reaches 1.4MPa, the breaking stress reaches 2.9MPa, the elongation at break reaches 120%, and the toughness reaches 2.5MJ / m 3 .

[0151] Table 1 Flame retardant properties and mechanical properties of samples 1-20

[0152]

[0153] As shown in Figure 2 , samples 1-9 are PUs prepared by physically mixing FR01 and TMP-polyol. With the increase of the content of polyol FR01, the flame retardant effect of the prepared PU product gradually increases, and the tensile strength and elongation at break gradually increase. Therefore, when FR01 and TMP-polyol are physically blended to prepare PU, in order to make the PU flame retardant effect reach V0 level, the content of secco in the PU product is 15 wt.%.

[0154] As shown in Figure 3 , sample 10 shows that when the diacid in FR01 is changed from adipic acid to sebacic acid, i.e. the length of the carbon chain is lengthened, the elongation at break of the prepared PU increases, the breaking stress decreases, the overall flexibility of the PU increases, the mechanical properties meet the requirements and the flame retardant effect is not affected. Sample 11 shows that when the monobasic acid in FR01 is changed from oleic acid to stearic acid, the elongation at break of the prepared PU increases, the breaking stress is high, the overall mechanical properties are improved and the flame retardant effect of the PU is not affected. Therefore, the diacid and monobasic acid in FR01 have universality, and other homologous acids can be used to replace them without affecting the flame retardant effect of the PU prepared from FR01.

[0155] As shown in Figure 4As shown, samples 12-14 are PUs prepared from block polyols (i.e., cyclic acid and TMP are covalently bonded) in FR01 by replacing part of the cyclic acid with TMP. As the cyclic acid content in the polyol FR01 decreases, the flame retardancy, tensile strength, and elongation at break of the resulting PU products gradually decrease. Furthermore, regarding the flame retardancy, for PUs prepared by block blending cyclic acid and TMP in FR01 through covalent bonding, the lower limit of the cyclic acid mass fraction in the PU product is 12 wt.% to achieve a V0 flame retardancy rating.

[0156] like Figure 5 As shown, samples 15-16 were prepared using FR01 as the soft segment and IPDI and MDI as the isocyanate, respectively. The flame retardant effect of the PU prepared with IPDI was unaffected, its tensile strength decreased but its elongation at break increased, and its overall mechanical properties met the requirements. Similarly, the flame retardant effect of the PU prepared with MDI was unaffected, its tensile strength increased but its elongation at break decreased, and its overall mechanical properties met the requirements. It can be seen that, using FR01 as the soft segment, the mechanical properties of PUs prepared with different isocyanates are affected by the type of isocyanate, but the overall mechanical properties all meet the requirements, and the flame retardant effect is unaffected.

[0157] like Figure 6 As shown, samples 17-19 are PU samples with FR01 as the soft segment or FR01 and TMP-polyol as the soft segment and PM200 and BDO as the hard segment. Although the sac content is greater than 15 wt.%, the flame retardant effect and elongation at break of the PU decrease as the hard segment content increases. To achieve a V0 flame retardant rating and meet the mechanical property requirements, the hard segment content in the PU should not be too high.

[0158] like Figure 7 As shown, compared with sample 13, sample 20 uses 1,4-butanediol (BDO) to partially replace cyproheptad, and the structure of the resulting flame-retardant polyester polyol has R3 as an alkyl group (as shown in Formula II). The PU product prepared using this flame-retardant polyester polyol can also achieve a V-0 flame retardant rating, its overall mechanical properties meet the requirements, and its elongation at break is significantly improved.

[0159] In summary, the saccharide and hard segment content in PU samples directly determine the flame retardant effect. The saccharide content needs to be greater than 12 wt.%, and the hard segment content cannot be too high. The overall mechanical properties are affected by monobasic acid, dibasic acid, and isocyanate.

[0160] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A halogen-free bio-based flame-retardant polyester polyol, having a structure as shown in Formula I, Formula I wherein R 1 is a C 2-C 17 hydrocarbon group; R 2 is a C 2-C 16 alkyl group; and l is an integer from 2 to 7. 2.A method for preparing the halogen-free bio-based flame-retardant polyester polyol of claim 1, comprising the following steps: mixing sebacic acid and monobasic acid in a molar ratio of 1:(0.4-1.3), adding a first catalyst, vacuumizing, and reacting at a temperature of 180-240℃ for 3-16 h, then adding dibasic acid to continue reacting for 3-16 h, the amount of the dibasic acid added being in a molar ratio of (0.2-0.9):1 to the sebacic acid, to obtain the halogen-free bio-based flame-retardant polyester polyol of Formula I; the first catalyst comprising at least one of tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, tetrabutyl zirconate, tetraisopropyl zirconate, dibutyl tin dilaurate, and antimony zinc oxide.

3. The process for the preparation of a halogen-free bio-based flame retardant polyester polyol according to claim 2, characterized in that, The monobasic acid comprises at least one of dodecanoic acid, acetic acid, butyric acid, hexanoic acid, decanoic acid, linoleic acid, linolenic acid, oleic acid, and stearic acid; and the dibasic acid comprises at least one of pimelic acid, glutaric acid, pivalic acid, a ring-opening product of maleic anhydride, azelaic acid, sebacic acid, adipic acid, and decanedioic acid.

4. The process for the preparation of a halogen-free bio-based flame retardant polyester polyol according to claim 2, characterized in that, When the acid value is less than 3 mg KOH / g, the dibasic acid is added, and then when the acid value is less than 3 mg KOH / g and the hydroxyl value reaches 40-70 mg KOH / g, the reaction is ended.

5. A process for the preparation of a polyurethane material, characterized in that, comprising the following steps: mixing a first polyol with isocyanate and reacting at 50-90℃ for 1-3 h to obtain a polyurethane prepolymer; mixing the polyurethane prepolymer with a second polyol, adding a second catalyst, stirring and mixing, and reacting at 60-120℃ for 10-16 h to obtain a polyurethane material; wherein the first polyol comprises the halogen-free bio-based flame-retardant polyester polyol of claim 1; the molar ratio of the first polyol calculated based on hydroxyl groups to the isocyanate calculated based on NCO groups is 1:(1-1.3); the second catalyst comprises at least one of organic tin, organic amine, organic mercury, and organic bismuth; and the sebacic acid content is ≥15 wt.%, wherein the sebacic acid content refers to the percentage of the weight of sebacic acid used in the preparation of the halogen-free bio-based flame-retardant polyester polyol in the weight of the polyurethane material.

6. The method of claim 5, wherein the polyurethane material is prepared by reacting the polyol, the polyisocyanate, and the chain extender. 5 The isocyanate comprises at least one of Wanhua Chemical PM200, isophorone diisocyanate, and 4,4'-diphenylmethane diisocyanate.

7. The method for preparing the polyurethane material according to claim 5, characterized in that, The second catalyst is added in an amount of 0.001-0.1 wt.% of the polyurethane prepolymer.

8. The method for preparing polyurethane according to claim 5, characterized in that, The second polyol comprises at least one of 1,4-butanediol, ethylene glycol, diethylene glycol, 1,3-propanediol, and 2-methyl-1,3-propanediol, and the molar ratio of the polyurethane prepolymer to the second polyol is 1:1-1.

3.

9. A polyurethane material, characterized by, prepared by the method of any one of claims 5-8.

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