A method for preparing a high-strength bio-based waterborne polyurethane

Abstract

The application discloses a kind of preparation methods of high-strength bio-based waterborne polyurethane, belong to polyurethane technical field.The weight parts of raw material include the following:40-50 parts bio-based polyol, 3-5 parts dimethylol propionic acid, 20-25 parts isocyanate, 2-6 parts modifier, 0.1-0.3 parts catalyst, 5-8 parts chain extender, 3-4 parts triethylamine, 5-10 parts nanocellulose, 60-80 parts deionized water.Nanocellulose can improve the mechanical strength of polyurethane;Modifier can improve the flame retardancy and mechanical strength of polyurethane, and has good stability, with long-term;Bio-based polyol is replaced by petroleum-based raw materials, and water is used as dispersion medium, green and environmentally friendly.Above all, the polyurethane prepared in the application has good flame retardancy and mechanical strength, and is environmentally friendly, and has important application value in the field of polyurethane technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane, and particularly relates to a preparation method of high-strength bio-based waterborne polyurethane. BACKGROUND

[0002] With the increasing global environmental awareness and the increasingly stringent regulations on volatile organic compound (VOC) emissions in various countries, traditional solvent-based polyurethane materials are facing severe challenges due to the release of a large amount of harmful organic solvents in the production and use process. As an environmentally friendly material, waterborne polyurethane (WPU) has the advantages of low toxicity, non-flammability, easy processing, etc., and gradually becomes a research hotspot in the field of polyurethane.

[0003] At present, the synthesis of commercial waterborne polyurethane mainly depends on petroleum-based raw materials such as polyether polyol, polyester polyol and isophorone diisocyanate. Such raw materials are not renewable, and their production process is accompanied by high carbon emissions. With the deepening of the "double carbon", the development of bio-based polyurethane materials has attracted widespread attention from academia and industry.

[0004] Bio-based polyols prepared from natural renewable resources such as castor oil, soybean oil and lignin, although to some extent, realize the sustainability of raw materials, but the lack of rigid segments in the molecular structure leads to the problems of low tensile strength and small modulus of the prepared waterborne polyurethane, which is difficult to meet the requirements of some high-strength application scenarios, and cannot fully play the advantages of environmental protection materials.

[0005] In addition, the flammability of waterborne polyurethane is also a problem that cannot be ignored. In the use process, its flammable characteristics are easy to cause fire accidents and other safety accidents, which brings potential threat to people's life and property safety, further limiting the application of bio-based waterborne polyurethane. In view of the above, it is urgent to invent a bio-based waterborne polyurethane with high strength and flame retardance to meet the application of high-end field. SUMMARY

[0006] The purpose of the present application is to overcome the defects of the prior art and provide a preparation method of high-strength bio-based waterborne polyurethane.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A preparation method of high-strength bio-based waterborne polyurethane, comprising the following steps:

[0009] A1, in a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, bio-based polyol and dimethylol propionic acid are added, vacuum dehydration is carried out to remove water to avoid water reacting with isocyanate and affecting the quality of the prepolymer; then isocyanate, modifier and catalyst are added, after uniform stirring, pre-polymerization is carried out, and the reaction is completed to obtain a prepolymer;

[0010] A2, a chain extender is added to the prepolymer, after stirring and reaction, a neutralizer triethylamine is added, secondary stirring and reaction are carried out to fully neutralize the carboxyl group, and an ionic polyurethane is obtained; the addition of the chain extender can further lengthen the molecular chain and increase the crosslinking density, at this time, the viscosity of the reaction system gradually increases;

[0011] A3, nanocellulose is dispersed in deionized water, after ultrasonic treatment for 20-30 min, the ionic polyurethane is added, and high-speed shearing emulsification is carried out to obtain a high-strength bio-based waterborne polyurethane.

[0012] Further, the raw materials are as follows according to weight parts: 40-50 parts of bio-based polyol, 3-5 parts of dimethylol propionic acid, 20-25 parts of isocyanate, 2-6 parts of modifier, 0.1-0.3 parts of catalyst, 5-8 parts of chain extender, 3-4 parts of triethylamine, 5-10 parts of nanocellulose and 60-80 parts of deionized water.

[0013] Further, the temperature of vacuum dehydration in step A1 is 100-110°C, and the time is 1-2h.

[0014] Further, the isocyanate in step A1 is diphenylmethane diisocyanate.

[0015] Further, the catalyst in step A1 is one of dibutyltin dilaurate, dibutyltin diacetate and stannous octoate.

[0016] Further, the temperature of pre-polymerization in step A1 is 80-85°C, and the time is 2-3h.

[0017] Further, the chain extender in step A2 is 1,4-butanediol.

[0018] Further, the temperature of stirring and reaction in step A2 is 50-60°C, and the time is 1-1.5h.

[0019] Further, the temperature of secondary stirring and reaction in step A2 is 40-50°C, and the time is 20-30 min.

[0020] Further, the speed of high-speed shearing in step A3 is 8000 rpm, and the time is 15 min.

[0021] Further, the modifier in step A1 is prepared by the following steps:

[0022] B1, pentaerythritol and boric acid are added to a three-necked round-bottom flask equipped with an electric stirrer, a thermometer and an oil-water separator, toluene is added as a water-carrying agent, and the temperature is slowly increased to 110-120 DEG C, the reaction is stirred under reflux until no liquid drops are generated in the water separator, the temperature is kept unchanged, and the reaction is continuously carried out for 2-3 h to ensure complete esterification, the reaction is completed, and the initial product is obtained after post-treatment;

[0023] B2, the initial product, 8-chloro-1-octanol, triethylamine and toluene are added to a three-necked flask equipped with an electric stirrer and a thermometer under nitrogen protection, heating is carried out until the temperature of the system reaches 70-80 DEG C, the reaction is continuously stirred during the reaction, and the reaction is kept for 10-12 h, the reaction is completed, and the modifier is obtained after post-treatment.

[0024] Further, in step B1, the amount ratio of pentaerythritol, boric acid and toluene is 13.6 g: 13.1-14.5 g: 50 mL.

[0025] Further, in step B2, the amount ratio of the initial product, 8-chloro-1-octanol, triethylamine and toluene is 18.6 g: 33.2-35.7 g: 20.5-21.3 g: 150 mL.

[0026] The preparation principle of the modifier is as follows: first, esterification reaction of pentaerythritol and boric acid is carried out to obtain an initial product; then, nucleophilic substitution reaction of the initial product and 8-chloro-1-octanol is carried out under the catalysis of triethylamine, and finally, the modifier is prepared, and it is particularly noted that the amount-of-substance ratio of pentaerythritol and boric acid should be controlled to be 1:2, the amount-of-substance ratio of the initial product and 8-chloro-1-octanol should also be controlled to be 1:2, and boric acid and 8-chloro-1-octanol need to be excessive to ensure complete reaction.

[0027] The reaction formula related to the preparation of the modifier is as follows:

[0028]

[0029] According to the reaction formula for preparing the modifier, the modifier prepared in the application has a pentaerythritol bisborate ester structure, which is a key structure for playing a flame-retardant role. At high temperature, the borate ester decomposes to generate boron oxide and water vapor, wherein the boron oxide can capture free radicals in the combustion chain reaction to inhibit flame propagation, and the water vapor can dilute the concentration of combustible gas to reduce the combustion temperature. This flame-retardant mechanism endows the base body with excellent flame-retardant performance. In addition, the modifier also has a long-chain alkyl structure, which can improve the mechanical strength of the base body to a certain extent. Finally, the modifier has two hydroxyl groups at the end, which can participate in the synthesis of polyurethane, so that the small molecular modifier is connected to the polyurethane macromolecular segment, thereby improving the long-term performance of the modifier.

[0030] The beneficial effects of the application are as follows:

[0031] 1、The application will be used as nanocellulose raw material, which can form a nanonetwork in situ to improve the mechanical strength of polyurethane;

[0032] 2、The self-made modifier improves the flame retardance and mechanical strength of polyurethane, has good stability and long-term performance;

[0033] 3、The application uses bio-based polyols to replace petroleum-based raw materials, reduces carbon emissions and meets the "double carbon" requirements;

[0034] 4、The application uses water as a dispersion medium, has no VOC emissions and meets environmental protection regulations

[0035] In summary, the application uses three technical paths of bio-based raw material selection, nanocomposite reinforcement and multifunctional modifier design to prepare a polyurethane that has flame retardance, mechanical strength and environmental protection, which has important application value in the field of polyurethane technology. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0037] Example 1

[0038] Preparation of the modifier:

[0039] B1, 13.6g of pentaerythritol and 13.1g of boric acid are added to a three-necked round-bottom flask equipped with an electric stirrer, a thermometer and an oil-water separator, 50mL of toluene is added as a water-carrying agent, and the temperature is slowly raised to 110℃, and the reaction is carried out under reflux stirring until no liquid drops are generated in the water separator, the temperature is kept unchanged, and the reaction is continued for 2h to ensure complete esterification, the reaction is completed, excess toluene is removed by reduced pressure distillation, the crude product is dissolved in ethyl acetate, and then washed with saturated saline water, and after standing and separating, the organic phase is taken and dried to obtain the initial product;

[0040] B2, 18.6g of the initial product, 33.2g of 8-chloro-1-octanol, 20.5g of triethylamine and 150mL of toluene are added to a three-necked flask equipped with an electric stirrer and a thermometer under nitrogen protection; heating until the system temperature reaches 70℃, continuously stirring during the reaction, keeping the temperature for 10h, the reaction is completed, the triethylamine hydrochloride is removed by filtration, the toluene is removed by reduced pressure distillation, and the crude product is recrystallized with ethanol / water (1:1) to obtain the modifier;

[0041] A preparation method of a high-strength bio-based waterborne polyurethane, comprising the following steps:

[0042] A1, in a four-mouth flask equipped with a stirrer, a thermometer and a reflux condenser, 40 g of castor oil-based polyol and 3 g of dimethylol propionic acid were added, vacuum dehydration was carried out at 100℃ for 1 h to remove water to avoid the influence of water on the quality of the prepolymer by reacting with isocyanate; then 20 g of diphenyl methane diisocyanate, 2 g of modifier and 0.1 g of dibutyl tin dilaurate were added, after uniform stirring, pre-polymerization was carried out at 80℃ for 2 h, the reaction was completed, and a prepolymer was obtained;

[0043] A2, 5 g of 1,4-butanediol was added to the prepolymer, after stirring at 50℃ for 1 h, the temperature was lowered, 3 g of neutralizer triethylamine was added, and secondary stirring reaction was carried out at 40℃ for 20 min to fully neutralize the carboxyl group, and an ionic polyurethane was obtained;

[0044] A3, 5 g of nanocellulose was dispersed in 60 g of deionized water, after ultrasonic treatment for 20 min, it was added into the ionic polyurethane, and after high-speed shearing emulsification at 8000 rpm for 15 min, a high-strength bio-based waterborne polyurethane was obtained.

[0045] Example Two

[0046] Preparation of modifier:

[0047] B1, 13.6 g of pentaerythritol and 14.5 g of boric acid were added to a three-mouth round-bottom flask equipped with an electric stirrer, a thermometer and an oil-water separator, 50 mL of toluene was added as a water-carrying agent, and the temperature was slowly raised to 120℃, and the reaction was carried out under stirring and reflux until no liquid drops were generated in the water separator, the temperature was kept unchanged, and the reaction was continued for 3 h to ensure complete esterification, the reaction was completed, excess toluene was removed by reduced pressure distillation, the crude product was dissolved in ethyl acetate, and was washed with saturated brine, after standing and separating, the organic phase was taken, and was dried to obtain a primary product;

[0048] B2, under nitrogen protection, 18.6 g of the primary product, 35.7 g of 8-chloro-1-octanol, 21.3 g of triethylamine and 150 mL of toluene were added to a three-mouth flask equipped with an electric stirrer and a thermometer; heating until the system temperature reaches 80℃, constantly stirring during the reaction, keeping the temperature for 12 h, the reaction is completed, removing the triethylamine hydrochloride by filtration, removing the toluene by reduced pressure distillation, recrystallizing the crude product with ethanol / water (1:1) to obtain the modifier;

[0049] A method for preparing a high-strength bio-based waterborne polyurethane, comprising the following steps:

[0050] A1, in a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 45 g of castor oil-based polyol and 4 g of dimethylol propionic acid were added, vacuum dehydration was carried out at 105°C for 1.5 h to remove water to avoid the influence of water reacting with isocyanate on the quality of the prepolymer; then 22.5 g of diphenyl methane diisocyanate, 4 g of modifier and 0.2 g of dibutyl tin diacetate were added, after uniform stirring, pre-polymerization was carried out at 85°C for 2.5 h, the reaction was completed, and a prepolymer was obtained;

[0051] A2, 7 g of 1,4-butanediol was added to the prepolymer, after stirring at 55°C for 1 h, the temperature was lowered, 3.5 g of neutralizer triethylamine was added, and secondary stirring reaction was carried out at 45°C for 25 min to fully neutralize the carboxyl group, and an ionic polyurethane was obtained;

[0052] A3, 7.5 g of nanocellulose was dispersed in 70 g of deionized water, after ultrasonic treatment for 25 min, it was added into the ionic polyurethane, and high-speed shear emulsification was carried out at 8000 rpm for 15 min, and a high-strength bio-based waterborne polyurethane was obtained.

[0053] Example Three

[0054] The difference between this example and Example Two is that in this example, a method for preparing a high-strength bio-based waterborne polyurethane comprises the following steps:

[0055] A method for preparing a high-strength bio-based waterborne polyurethane comprises the following steps:

[0056] A1, in a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 45 g of castor oil-based polyol and 4 g of dimethylol propionic acid were added, vacuum dehydration was carried out at 105°C for 1.5 h to remove water to avoid the influence of water reacting with isocyanate on the quality of the prepolymer; then 22.5 g of diphenyl methane diisocyanate, 4 g of modifier and 0.2 g of dibutyl tin diacetate were added, after uniform stirring, pre-polymerization was carried out at 85°C for 2.5 h, the reaction was completed, and a prepolymer was obtained;

[0057] A2, 7 g of 1,4-butanediol was added to the prepolymer, after stirring at 55°C for 1 h, the temperature was lowered, 3.5 g of neutralizer triethylamine was added, and secondary stirring reaction was carried out at 45°C for 25 min to fully neutralize the carboxyl group, and an ionic polyurethane was obtained;

[0058] A3, 7.5 g of nanocellulose was dispersed in 70 g of deionized water, after ultrasonic treatment for 25 min, it was added into the ionic polyurethane, and high-speed shear emulsification was carried out at 8000 rpm for 15 min, and a high-strength bio-based waterborne polyurethane was obtained.

[0059] Comparative Example One

[0060] The difference between the present comparative example and Example 2 is that, in the present comparative example, a bio-based waterborne polyurethane is prepared without adding a modifier.

[0061] Comparative Example 2

[0062] The difference between the present comparative example and Example 2 is that, in the present comparative example, a bio-based waterborne polyurethane is prepared by replacing the modifier with 4 g of tricetyl borate.

[0063] The mechanical properties and flame-retardant properties of Examples 1, 2, 3 and Comparative Examples 1, 2 are tested; the test methods used are as follows:

[0064] The hardness is determined according to the GB / T 6739-2022 standard;

[0065] The mass loss is determined according to the national standard GB 12441 "facade fire retardant coating", and the mass loss after 300 days of application of Examples 1, 2, 3 and Comparative Example 2 is determined according to the standard;

[0066] The results are shown in the following table:

[0067]

[0068] As can be seen from the above table, the bio-based waterborne polyurethane prepared in the present application has better mechanical properties and flame-retardant properties than the comparative examples, and the performance is long-lasting, which has important application value in the field of polyurethane technology.

[0069] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and it is intended to encompass all changes falling within the meaning and scope of the equivalent elements of the claims.

Claims

1. A process for the preparation of high strength bio-based waterborne polyurethane characterized in that, The method comprises the following steps: A1, vacuum dehydration of the bio-based polyol and dimethylol propionic acid, then adding isocyanate, modifier and catalyst, stirring uniformly, pre-polymerization, reaction completion, obtaining pre-polymer; A2, adding chain extender to the pre-polymer, stirring and reacting, then adding neutralizer triethylamine, secondary stirring and reacting, obtaining ionic polyurethane; A3, dispersing nanocellulose in deionized water, ultrasonic treatment, then adding ionic polyurethane, high-speed shearing and emulsifying, obtaining high-strength bio-based waterborne polyurethane; The modifier in step A1 is prepared by the following steps: B1, adding pentaerythritol and boric acid into a flask, then adding toluene, slowly heating to 110-120 DEG C, stirring and refluxing, until no liquid drops are generated in the water trap, keeping the temperature unchanged, continuing to react for 2-3h, reaction completion, obtaining initial product; B2, under nitrogen protection, adding the initial product, 8-chloro-1-octanol, triethylamine and toluene into a flask; stirring and warming at 70-80 DEG C for 10-12h, reaction completion, obtaining the modifier; The reaction formula for preparing the modifier is as follows: 。 2. A process for the preparation of a high strength bio-based waterborne polyurethane as claimed in claim 1, wherein, The ratio of the amount of pentaerythritol, boric acid and toluene in step B1 is 13.6g:13.1-14.5g:50mL.

3. A process for the preparation of a high strength bio-based waterborne polyurethane as claimed in claim 1, wherein, The ratio of the amount of initial product, 8-chloro-1-octanol, triethylamine and toluene in step B2 is 18.6g:33.2-35.7g:20.5-21.3g:150mL.

4. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The amount of each raw material is as follows: 40-50 parts of bio-based polyol, 3-5 parts of dimethylol propionic acid, 20-25 parts of isocyanate, 2-6 parts of modifier, 0.1-0.3 parts of catalyst, 5-8 parts of chain extender, 3-4 parts of triethylamine, 5-10 parts of nanocellulose, 60-80 parts of deionized water.

5. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The temperature for vacuum dehydration in step A1 is 100-110 DEG C, and the time is 1-2h.

6. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The catalyst in step A1 is one of dibutyltin dilaurate, dibutyltin diacetate and stannous octoate.

7. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The temperature for pre-polymerization in step A1 is 80-85 DEG C, and the time is 2-3h.

8. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The temperature for stirring and reacting in step A2 is 50-60 DEG C, and the time is 1-1.5h.

9. The method for preparing a high-strength bio-based waterborne polyurethane according to claim 1, characterized in that, The temperature for secondary stirring and reacting in step A2 is 40-50 DEG C, and the time is 20-30min.

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