Modified bio-based polyether polyols and their preparation methods

Abstract

This invention discloses modified bio-based polyether polyols and their preparation methods, relating to the field of polyether polyol technology. The invention modifies the molecular structure of epoxy greases by grafting, introducing triazine ring compounds for ring-opening modification, and simultaneously combining other initiators to increase its functionality, thereby increasing the degree of crosslinking of its molecular structure during application. After epoxide alkane polymerization modification and molecular weight adjustment, modified bio-based polyether polyols with appropriate hydroxyl values ​​and viscosities are obtained.

Description

Technical Field

[0001] This invention relates to the field of polyether polyol technology, specifically to modified bio-based polyether polyols and their preparation methods. Background Technology

[0002] In the field of polymer materials, polyether polyols are the core raw materials for polyurethane synthesis, and their performance and source directly determine the application value and environmental friendliness of downstream products. Traditional petroleum-based polyether polyols rely on non-renewable fossil resources, while bio-based polyether polyols have become a focus of industry research and development due to their advantages such as renewable raw materials (derived from natural resources such as vegetable oils and sugars), low carbon footprint, and good biocompatibility.

[0003] Currently, bio-based polyether polyols have been partially applied in fields such as flexible polyurethane foams (e.g., furniture, automotive seats), coatings, and adhesives. For example, Wanhua Chemical's WANOL® FB340 & 350 series of bio-based polyether polyols, with a bio-based content exceeding 50%, can reduce carbon emissions by 30-50%, meeting the flexible foam industry's requirements for material flexibility and environmental friendliness. However, in rigid foam fields such as building insulation, mining reinforcement, and road infrastructure repair, where stringent requirements for material strength, rigidity, and thermal stability are imposed, the application of bio-based polyether polyols still faces significant technical bottlenecks.

[0004] (1) Limited molecular structure leads to insufficient strength: Most existing bio-based polyether polyols use vegetable oils such as castor oil and epoxidized soybean oil as initiators. Their molecular chains are mainly composed of long-chain fatty acid structures with low functionality. The crosslinking density of the polyurethane rigid foam formed by downstream polymerization is insufficient, which cannot provide the compressive strength, impact strength and dimensional stability required for rigid foam products.

[0005] (2) Performance and bio-based content are difficult to balance: Some studies have introduced petroleum-based high-functionality initiators (such as sucrose and sorbitol) to increase the degree of crosslinking, but this will lead to a significant decrease in bio-based content and lose the environmental advantages of bio-based materials; if the amount of vegetable oil is simply increased to ensure the bio-based content, the rigidity and heat distortion temperature of rigid foam products will be further reduced due to the excessive flexibility of the molecular chain.

[0006] (3) Lack of flame retardant performance: There are mandatory requirements for the flame retardancy of polyurethane rigid foam in fields such as building insulation and mining. Existing bio-based polyether polyol molecules lack flame retardant active groups, requiring the addition of a large amount of flame retardants (such as halogenated flame retardants and phosphorus-based flame retardants), which not only increases costs but may also lead to the deterioration of the mechanical properties of the products and environmental risks (such as the release of toxic gases when halogenated flame retardants are burned).

[0007] In summary, the key issue that urgently needs to be addressed in the field of bio-based polyether technology is how to simultaneously improve the crosslinking ability and flame retardant properties of bio-based polyether polyols through molecular structure design and regulation while ensuring a high bio-based content, so as to meet the application requirements of rigid polyurethane foam in high-strength and high-rigidity fields. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a modified bio-based polyether polyol and its preparation method. The method involves grafting modification of the molecular structure of epoxy oil, introducing triazine ring compounds for ring-opening modification, and combining other initiators to increase its functionality, thereby increasing the degree of crosslinking of its molecular structure in application. After modification by epoxy alkane polymerization, the molecular weight is adjusted to obtain a modified bio-based polyether polyol with appropriate hydroxyl value and viscosity.

[0009] The technical solution of this invention is as follows:

[0010] On the one hand, the present invention provides a method for preparing modified bio-based polyether polyols, comprising the following steps:

[0011] S1. Triazine ring compound, epoxy grease, small molecule polyol, and catalyst are added to the reactor. Under a nitrogen atmosphere, the temperature is raised to 60-70℃ and maintained for 2-3 hours. Then, the temperature is controlled to 70-90℃, and the mixture is degassed under vacuum to obtain a polymer intermediate. The triazine ring compound consists of highly imino-modified melamine and methylguanidine, with methylguanidine accounting for 6.9-8.1% of the total mass of the triazine ring compound.

[0012] S2 is heated to 90-125℃, and epoxy alkane is added dropwise to the reactor to carry out the polymerization reaction. During the dropwise addition, the pressure is controlled to be <0.4MPa and the temperature to be 90-125℃. After the dropwise addition is completed, the reaction is continued under internal pressure at 0.2-0.4MPa for 2-3 hours. The epoxy grease, triazine ring compound, small molecule polyol, catalyst and epoxy alkane account for 51.5-55%, 7.5-20.5%, 13-18.5%, 0.8-1.7% and 13-21% of their total mass, respectively.

[0013] After the S3 internal pressure reaction is complete, the temperature is lowered to 85-90℃, nitrogen bubbling is performed, and the material is cooled and discharged to obtain the modified bio-based polyether polyol.

[0014] Preferably, in step S1, the epoxidized oil is epoxidized soybean oil.

[0015] Preferably, in step S1, the small molecule polyol is two of sorbitol, glycerol, and sucrose.

[0016] Preferably, in step S1, the catalyst is triethylamine or a 40 wt.% aqueous solution of dimethylamine.

[0017] Preferably, in step S1, vacuum bubbling degassing is performed for 1.5-2.5 hours.

[0018] Preferably, in step S2, the epoxide is propylene oxide.

[0019] On the other hand, the present invention provides a modified bio-based polyether polyol, which is prepared by the above-described method for preparing modified bio-based polyether polyol.

[0020] Preferably, the modified bio-based polyether polyol has a bio-based content of 65% or more.

[0021] This invention, through innovative molecular design and process optimization, prepares modified bio-based polyether polyols and corresponding polyurethane products, which have the following significant advantages compared to existing technologies:

[0022] 1. This invention uses epoxidized soybean oil (a bio-based raw material) as the main initiator, combined with bio-based small molecule polyols such as sorbitol and glycerol. Simultaneously, it strictly controls the proportion of epoxy oil in the raw materials, ensuring that the bio-based content of the final product is consistently above 65%, significantly higher than existing bio-based polyether polyols used in rigid foam. This results in lower carbon emissions compared to traditional petroleum-based rigid foam polyether polyols, meeting environmental protection and sustainable development requirements. Furthermore, this invention introduces triazine ring compounds, utilizing the amino groups on the triazine ring to undergo a ring-opening grafting reaction with the epoxy groups of the epoxy oil under a catalyst. This introduces nitrogen-containing heterocyclic structures into the molecular chain, significantly enhancing molecular functionality. Then, through epoxide alkane polymerization, the molecular weight distribution is controlled, increasing the crosslinking density of the downstream polyurethane rigid foam. According to performance test results, the compressive strength of the polyurethane rigid foam prepared using the modified bio-based polyether polyol of this invention reaches 42.7-48 MPa, a significant improvement over traditional petroleum-based polyurethane rigid foam, fully meeting the strength requirements of rigid foam applications such as building insulation and mining reinforcement.

[0023] 2. This invention innovatively grafts a triazine ring structure into the polyether polyol molecular chain. The CN and NH bonds in the triazine ring undergo an endothermic decomposition reaction during combustion, releasing inert gases (such as NH3). Simultaneously, a dense char layer is formed to block oxygen and heat transfer, endowing the polyether polyol with "built-in flame retardant" properties. Test results show that the flame retardant performance of rigid polyurethane foam prepared using the modified bio-based polyether polyol of this invention is significantly improved compared to traditional petroleum-based rigid polyurethane foam; moreover, no additional halogenated flame retardants are required, avoiding the release of toxic gases (such as HCl and HBr) during combustion, while also reducing the negative impact of flame retardants on the mechanical properties of the product.

[0024] 3. This invention ensures the triazine ring grafting reaction and the epoxy alkane polymerization reaction are complete and controllable through stepwise temperature and pressure control. The hydroxyl value of the product is stable at 345-355 mgKOH / g, and the viscosity is controlled at 1177-2463 mPa·s, meeting the needs of large-scale industrial production. Furthermore, the modified bio-based polyether polyol of this invention is not only suitable for rigid polyurethane foam, but can also be adapted to the different requirements for hydroxyl value and viscosity in polyurethane elastomers, adhesives, and other fields by adjusting the degree of epoxy alkane polymerization, thus broadening the application scenarios of bio-based polyether polyols. At the same time, the raw materials (epoxidized soybean oil, triazine ring compounds, etc.) are all industrially mass-produced products, resulting in low procurement costs. The process requires no special equipment and is easily adapted to existing polyether polyol production facilities, demonstrating good industrialization prospects. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0026] Example 1

[0027] The preparation method of the modified bio-based polyether polyol in this embodiment includes the following steps:

[0028] S1 Add 40g of triiminotrimethoxymelamine, 3g of methylguanidine, 300g of epoxidized soybean oil, 70g of sucrose, 30g of glycerol, and 8g of 40wt.% dimethylamine aqueous solution to the reactor. After leak testing and replacement, the reactor is heated to 60℃ under a nitrogen atmosphere and kept at this temperature for 2 hours. Then, the temperature is controlled to 70℃ and degassed under vacuum for 1.5 hours to obtain a polymer intermediate.

[0029] After S2 is degassed, the temperature is increased. When the temperature reaches 90℃, the propylene oxide valve is opened, and 101.8g of propylene oxide is added dropwise to initiate the polymerization reaction. During the dropwise addition, the pressure is controlled at <0.4MPa, and the temperature is controlled within the range of 90-125℃. After the dropwise addition is completed, the internal pressure reaction is continued for 2 hours while maintaining the pressure within the range of 0.2-0.4MPa.

[0030] After the S3 internal pressure reaction is completed, the temperature is reduced to 90℃, and nitrogen is bubbled for 1 hour before cooling and releasing the material to obtain modified bio-based polyether polyol 1, with a hydroxyl value of 345mgKOH / g and a viscosity of 1580mPa·s.

[0031] Example 2

[0032] The preparation method of the modified bio-based polyether polyol in this embodiment includes the following steps:

[0033] S1. Add 80g of triiminotrimethoxymelamine, 7g of methylguanidine, 450g of epoxidized soybean oil, 100g of sorbitol, 25g of glycerol, and 7g of 40wt.% dimethylamine aqueous solution to the reactor. After leak testing and purging, heat to 70℃ under nitrogen atmosphere, maintain the temperature for 3h, then control the temperature to 90℃ and degas under vacuum for 2.5h to obtain polymer intermediate.

[0034] After S2 is degassed, the temperature is increased. When the temperature reaches 125℃, the propylene oxide valve is opened, and 175g of propylene oxide is added dropwise to initiate the polymerization reaction. During the dropwise addition, the pressure is controlled at <0.4MPa, and the temperature is controlled within the range of 90-125℃. After the dropwise addition is completed, the internal pressure reaction is continued for 3 hours while maintaining the pressure within the range of 0.2-0.4MPa.

[0035] After the S3 internal pressure reaction is completed, the temperature is reduced to 85℃, and nitrogen is bubbled for 2 hours before cooling and releasing the material to obtain modified bio-based polyether polyol 2 with a hydroxyl value of 355mgKOH / g and a viscosity of 1177mPa·s.

[0036] Example 3

[0037] The preparation method of the modified bio-based polyether polyol in this embodiment includes the following steps:

[0038] S1. Add 90g of triiminotrimethoxymelamine, 7g of methylguanidine, 250g of epoxidized soybean oil, 50g of sucrose, 15g of glycerol, and 8g of triethylamine to the reactor. After leak testing and replacement, heat the reactor to 65°C under a nitrogen atmosphere and maintain the temperature for 2.5h. Then, control the temperature to 80°C and degas under vacuum for 1.5h to obtain a polymer intermediate.

[0039] After S2 is degassed, the temperature is increased to 105℃. Then, the propylene oxide valve is opened, and 63g of propylene oxide is added dropwise to initiate the polymerization reaction. During the dropwise addition, the pressure is controlled at <0.4MPa, and the temperature is controlled within the range of 90-125℃. After the dropwise addition is completed, the internal pressure reaction is continued for 2.5h, controlled within the range of 0.2-0.4MPa.

[0040] After the S3 internal pressure reaction is completed, the temperature is reduced to 90℃, and nitrogen is bubbled for 1.5 hours before cooling and releasing the material to obtain modified bio-based polyether polyol 3, with a hydroxyl value of 351 mg KOH / g and a viscosity of 2463 mPa·s.

[0041] Comparative Example 1

[0042] The preparation method of the bio-based polyether polyol of Comparative Example 1 includes the following steps:

[0043] In step S1, 265g of sucrose, 222g of glycerol, and 15g of triethylamine were added to the reactor. After leak testing and purging, the temperature was raised to 80°C, and the propylene oxide valve was opened, allowing 686g of propylene oxide to be added dropwise into the reactor. Then, 20g of triethylamine was added, and the temperature was raised to 106°C. Afterward, the propylene oxide valve was opened, and 1000g of propylene oxide was added dropwise into the reactor for internal pressure polymerization for 2 hours. Subsequently, the mixture was degassed at 105°C for 1 hour, and the resulting product was a light yellow transparent liquid, polyether polyol A, with a hydroxyl value of 356mgKOH / g and a viscosity of 1140mPa·s.

[0044] Comparative Example 2

[0045] The preparation method of the bio-based polyether polyol of Comparative Example 2 includes the following steps:

[0046] In step S1, 265g of sucrose, 222g of glycerol, 955g of epoxidized soybean oil, and 15g of dimethylamine were added to the reactor. After leak testing and purging, the reactor was heated to 80°C, and the propylene oxide valve was opened, allowing 340g of propylene oxide to be added dropwise into the reactor. Then, 7g of triethylamine was added, and the reactor was heated to 106°C. The propylene oxide valve was then opened, and 413g of propylene oxide was added dropwise into the reactor for internal pressure polymerization for 2 hours. Subsequently, the mixture was degassed at 105°C for 1 hour, and the resulting product was a light yellow transparent liquid, polyether polyol B, with a hydroxyl value of 345mgKOH / g and a viscosity of 1546mPa·s.

[0047] Comparative Example 3

[0048] The difference from Example 1 is that in step S1, the amount of triiminotrimethoxymelamine compound added is 43g, and methylguanidine is not added.

[0049] Comparative Example 4

[0050] The difference from Example 1 is that the amount of triiminotrimethoxymelamine added is 60g, the amount of methylguanidine added is 5g, the amount of epoxidized soybean oil added is 300g, the amount of sucrose added is 50g, the amount of glycerol added is 40g, the amount of 40wt.% dimethylamine aqueous solution added is 8g, and the amount of propylene oxide added is 74g.

[0051] The performance of the bio-based polyether polyols prepared in Examples 1-3 and Comparative Examples 1-4 was tested: hydroxyl value and viscosity were tested according to GB / T 12008 Plastics Polyether Polyols; the bio-based content was the percentage of bio-based raw materials in the total raw materials. The test results are shown in Table 1.

[0052] Table 1 Performance test results of bio-based polyether polyols prepared in Examples 1-3 and Comparative Examples 1-4

[0053]

[0054] As can be seen from Table 1, the bio-based polyether polyol prepared in Comparative Example 1, as a rigid foam polyether product commonly used in mining and road repair, has an extremely low bio-based content. This is because epoxidized soybean oil was not used in the raw materials, and only a small amount of bio-based small molecule polyols such as sucrose and glycerol were used, with the remainder mainly consisting of propylene oxide. As a result, the bio-based content is much lower than that in the examples, and the environmental advantages of bio-based materials are completely lost.

[0055] Although the bio-based content of Comparative Example 2 is close to that of Example 1, the lack of triazine ring compounds and the use of epoxidized soybean oil to provide the bio-based framework resulted in insufficient molecular functionality. The viscosity was similar to that of Example 1, but due to the lack of triazine ring structure, it could not improve the subsequent crosslinking density and did not have built-in flame retardant properties. It was merely a "simple bio-based polyether" and did not solve the core technical pain points in the rigid foam field.

[0056] The hydroxyl value of Comparative Example 3 was slightly lower than that of Example 1, reflecting an insufficient number of hydroxyl groups on the molecular chain. The absence of methylguanidine led to a decrease in the reactivity of the triazine ring compound, resulting in insufficient ring-opening grafting reaction with epoxy grease and a reduced amount of hydroxyl group formation; the viscosity was lower than that of Example 1, indicating insufficient cross-linking of the molecular chain; although the bio-based content was at a high level, the functionality of the triazine ring could not be fully utilized due to the absence of methylguanidine, limiting the subsequent strength improvement of the polyurethane product.

[0057] The hydroxyl value of Comparative Example 4 is too high, possibly due to an excessively high proportion of epoxy grease, resulting in an excessively high hydroxyl density on the molecular chain. This can lead to over-crosslinking in subsequent polymerization reactions, affecting the toughness of the product. The viscosity is higher than in Example 1, but because of the excessively high proportion of epoxy grease, the triazine ring structure in the molecular chain is relatively insufficient, failing to fully exert its crosslinking and flame-retardant effects, leading to a decline in the performance of the subsequent product.

[0058] Polyurethane products were prepared using the bio-based polyether polyols of Examples 1-3 and Comparative Examples 1-4. Component A consisted of 70g modified bio-based polyether polyol, 2g Momentive L6100 foam leveling agent, 1.5g lead isooctanoate catalyst, and 30g tris(2-chloroethyl) phosphate (TCEP). After thorough mixing, component A was obtained. Component B was polyphenylene polyisocyanate. Components A and B were mixed at a mass ratio of 1:1 at 25°C, stirred at 1000 rpm for 15 seconds, and then poured into a mold. After 15 minutes, the mold was opened, and polyurethane product samples were removed for performance testing.

[0059] The heat of reaction was tested according to "AQT-1089-2020 Polymer Materials for Strengthening Coal and Rock Mass in Coal Mines - Part 5: Maximum Reaction Temperature";

[0060] The compressive strength was tested according to GB / T 2567-2008 Test Method for Properties of Resin Castings;

[0061] The oxygen index was tested according to GB / T 2406.2-2009 Determination of Combustion Behavior by Oxygen Index Method for Plastics.

[0062] The test results are shown in Table 2:

[0063] Table 2 Performance test results of polyurethane product samples prepared in Examples 1-3 and Comparative Examples 1-4

[0064]

[0065] As shown in Table 2, Comparative Example 1, lacking the addition of triazine ring compounds and epoxy grease, resulted in excessively high heat of reaction in the prepared polyurethane product. This is because the bio-based polyether polyol prepared in Comparative Example 1 has high hydroxyl activity, leading to a rapid reaction between the hydroxyl groups and isocyanates, resulting in high heat of reaction. In contrast, the epoxy grease added in this invention exhibits reduced activity due to the position of the hydroxyl groups and the molecular chain, resulting in a lower heat of reaction when reacting with isocyanates. Furthermore, due to low molecular chain functionality and insufficient crosslinking density, the three-dimensional network structure of the rigid polyurethane foam is loose, unable to withstand external extrusion, and its compressive strength is far lower than that of the examples, failing to meet the strength requirements of rigid foam applications such as building insulation and mining reinforcement. Moreover, due to the lack of the nitrogen-containing heterocyclic structure of triazine ring compounds, there is a lack of an "inherent flame retardant" mechanism, requiring the addition of TCEP flame retardant. However, the molecular structure of petroleum-based polyethers has poor compatibility with flame retardants, resulting in poor flame retardant performance and an oxygen index lower than that of the examples.

[0066] Comparative Example 2, lacking the addition of a triazine ring compound, resulted in a polyurethane product with extremely poor compressive strength. This is because the absence of the triazine ring compound leads to insufficient functionality of the polyether polyol, resulting in extremely low crosslinking density during downstream polymerization. The resulting loose three-dimensional network structure of the rigid polyurethane foam significantly deteriorates its mechanical properties, making it completely unsuitable for the strength requirements of the rigid foam industry. Due to the lack of CN and NH bonds in the triazine ring compound, it cannot decompose and absorb heat during combustion, release inert gases, or form a dense char layer. Flame retardancy relies entirely on the external TCEP flame retardant, and the structure of the bio-based long-chain fatty acid actually reduces flame retardant efficiency, resulting in the lowest oxygen index among all samples. Furthermore, Comparative Example 2 exhibits a higher heat of reaction. This is because the flexibility of the bio-based long chain leads to an unstable polymerization rate, resulting in a higher heat release than the examples, although lower than Comparative Example 1, which may still affect the dimensional stability of the product.

[0067] Comparative Example 3, lacking the addition of methylguanidine, resulted in insufficient compressive strength in the prepared polyurethane product. This is because, although highly imino-modified melamine was added, the synergistic effect of methylguanidine was missing. Methylguanidine has a higher nitrogen content and stronger reactivity, which can further improve the grafting efficiency of triazine ring compounds and epoxy greases, increasing the crosslinking sites of the molecular chains. Therefore, although its compressive strength was higher than that of Comparative Examples 1-2, it still did not reach the 42.7 MPa of Example 1, failing to meet the high strength requirements of the rigid foam industry. In addition, the highly imino-modified melamine still provides a certain flame retardant effect, so the oxygen index is the same as that of Example 1. However, due to the lack of methylguanidine, the integrity of the flame retardant mechanism is insufficient, and the flame retardant performance will rapidly decline if the external flame retardant is subsequently removed.

[0068] In Comparative Example 4, the excessive epoxy grease content resulted in insufficient compressive strength of the prepared polyurethane product. This is because the high proportion of epoxy grease led to an excessive number of long-chain fatty acid structures in the molecular chain. Although the bio-based content met the standard, the flexibility of the long chains weakened the rigidity of the polyurethane rigid foam. Simultaneously, the relative proportion of triazine ring compounds decreased, limiting the improvement of crosslinking density, resulting in lower compressive strength than in Example 1. Furthermore, due to the insufficient relative proportion of triazine ring structures, the char layer formed during combustion was not dense enough, reducing the release of inert gases and resulting in a slightly lower flame-retardant effect than in Example 1.

Claims

1. A method for preparing modified bio-based polyether polyols, characterized in that, Includes the following steps: S1. Triazine ring compound, epoxy oil, small molecule polyol, and catalyst are added to the reactor. Under a nitrogen atmosphere, the temperature is raised to 60-70℃ and maintained for 2-3 hours. Then, the temperature is controlled to 70-90℃, and the mixture is degassed under vacuum to obtain a polymer intermediate. The triazine ring compound is a highly imino-modified melamine and methylguanidine, with methylguanidine accounting for 6.9-8.1% of the total mass of the triazine ring compound. The epoxy oil is epoxidized soybean oil. The small molecule polyol is two of sorbitol, glycerol, and sucrose. S2 is heated to 90-125℃, and epoxy alkane is added dropwise to the reactor to carry out the polymerization reaction. During the dropwise addition, the pressure is controlled to be <0.4MPa and the temperature to be 90-125℃. After the dropwise addition is completed, the reaction is continued under internal pressure at 0.2-0.4MPa for 2-3 hours. The epoxy grease, triazine ring compound, small molecule polyol, catalyst and epoxy alkane account for 51.5-55%, 7.5-20.5%, 13-18.5%, 0.8-1.7% and 13-21% of their total mass, respectively. After the S3 internal pressure reaction is complete, the temperature is lowered to 85-90℃, nitrogen bubbling is performed, and the material is cooled and discharged to obtain the modified bio-based polyether polyol.

2. The method for preparing the modified bio-based polyether polyol as described in claim 1, characterized in that, In step S1, the catalyst is triethylamine or a 40 wt.% aqueous solution of dimethylamine.

3. The method for preparing the modified bio-based polyether polyol as described in claim 1, characterized in that, In step S1, vacuum bubbling degassing is performed for 1.5-2.5 hours.

4. The method for preparing the modified bio-based polyether polyol as described in claim 1, characterized in that, In step S2, the epoxide alkane is propylene oxide.

5. A modified bio-based polyether polyol, characterized in that, It was prepared by the method for preparing modified bio-based polyether polyols as described in any one of claims 1-4.

6. The modified bio-based polyether polyol as described in claim 5, characterized in that, The modified bio-based polyether polyol has a bio-based content of over 65%.

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