A cyclodextrin compound-modified polyurethane elastomer and a method for preparing the same

Abstract

The present application relates to a cyclodextrin compound modified polyurethane elastomer and its preparation method, and belongs to the technical field of polymers. The main raw material composition and mass fraction of the cyclodextrin compound modified polyurethane are as follows: 44-46% of diisocyanate in A material, 54-56% of polyhydric alcohol; 70-74% of polyhydric alcohol in B material, 18-22% of polyether 330N polyhydric alcohol, and 4-8% of diol chain extender. The auxiliary raw material is a cyclodextrin compound, an indicator bromocresol blue, and a toluene solution of di-n-butylamine. The cyclodextrin compound modified polyurethane is a new type of polyurethane material with excellent mechanical properties. The cyclodextrin compound in the cyclodextrin compound modified polyurethane can provide many hydroxyl groups and form intermolecular hydrogen bonds with the polymer chain segments, thereby improving the mechanical properties of the polyurethane.

Description

Technical Field

[0001] This invention relates to a polyurethane elastomer modified with cyclodextrin compounds and its preparation method, belonging to the field of elastomer polymer technology. Background Technology

[0002] As an engineering plastic, polyurethane materials have received widespread attention and application in the automotive, aerospace, special operations, and military fields. Currently, polyurethane elastomers with excellent mechanical properties have not been extensively studied, which limits their application in the field of mechanics. To broaden the application range of polyurethane materials and improve their mechanical and impact resistance, fillers are added. Through sufficient contact between the fillers and the polyurethane chain segments, physical and chemical changes occur, altering the mechanical properties of the polyurethane material and expanding its application range in mechanical applications.

[0003] Most methods for modifying polyurethane elastomers using filler methods involve dispersing and compositing inorganic fillers (such as silica SiO2, carbon nanotubes, etc.). However, inorganic fillers occupy the space for polymer chain stacking, significantly reducing the damping value in the low-temperature region and leading to insufficient dispersion of inorganic fillers in the polyurethane elastomer matrix. Since the interaction force between inorganic fillers and the polyurethane elastomer matrix is ​​very small, adding more inorganic fillers can cause easy wear between the polyurethane elastomer matrix and inorganic fillers, resulting in poor material stability and brittleness of the polyurethane elastomer, i.e., deterioration of mechanical properties. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a polyurethane elastomer modified with cyclodextrin compounds and its preparation method. Due to the strong hydrogen bonding between cyclodextrin substances and the polar groups inside the polymer, the mechanical properties of the polyurethane material can be enhanced and its toughness increased while ensuring the mechanical properties of the polyurethane material itself.

[0005] The technical solution of this invention is:

[0006] A polyurethane elastomer modified with a cyclodextrin compound, wherein the polyurethane elastomer matrix is ​​modified with a cyclodextrin compound, the polyurethane elastomer matrix is ​​composed of hard segments and soft segments, and intermolecular hydrogen bonds are formed between the cyclodextrin compound and the hard segments and soft segments of the polyurethane elastomer matrix, respectively.

[0007] The structural formula of the polyurethane elastomer modified with cyclodextrin compounds is as follows:

[0008]

[0009] In this diagram, the dashed lines represent hydrogen bonds, and n is the number of structural units, which can be calculated from the molecular weight.

[0010] A method for preparing a polyurethane elastomer modified with a cyclodextrin compound, comprising curing component A, component B and a cyclodextrin compound, wherein the cyclodextrin compound is a white solid powder, including α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; the mass of the cyclodextrin compound is 0.5%-5.0% of the sum of the masses of component A and component B.

[0011] Based on the total mass of the raw materials used to prepare component A as 100%, the components of each raw material and their mass fractions are as follows:

[0012] Diisocyanate 44%–46%;

[0013] Polyols 54%–56%;

[0014] Based on the total mass of the raw materials used to prepare component B as 100%, the components and their mass fractions of each raw material are as follows:

[0015] Polyols 70%–74%;

[0016] Polyether 330N polyol (330N) 18%–22%;

[0017] Diol chain extenders: 4%–8%.

[0018] The diisocyanate is at least one of diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI);

[0019] The polypolyol is at least one of polytetrahydrofuran (PTMEG) with a molecular weight of 2000 and polytetrahydrofuran (PTMEG) with a molecular weight of 1000.

[0020] The molecular weight of the polyether 330N polyol is 4600-4800;

[0021] The diol chain extender is at least one of 1,4-butanediol (BDO), 1,3-propanediol (PDO), ethylene glycol (EG), and 1,5-pentanediol (PTDO).

[0022] A method for preparing a polyurethane elastomer modified with a cyclodextrin compound, comprising the following steps:

[0023] (1) The polyol in component A, the polyol, polyether 330N polyol (330N) in component B, and the diol chain extender are dehydrated. Then, under the protection of protective gas, the raw material diisocyanate and polyol in component A are mixed (stirred during mixing at a speed of 200 r / min), heated to 80-85℃, stirred for 4-5 h, and cooled to obtain a viscous polyurethane prepolymer.

[0024] (2) Under air-isolated conditions, the viscous polyurethane prepolymer obtained in step (1) is preheated to 40-50°C, and the polyol, polyether 330N polyol and diol chain extender in component B are preheated to 50-70°C.

[0025] (3) The cyclodextrin compound, the preheated viscous polyurethane prepolymer in step (2), the polyol, the polyether 330N polyol and the diol chain extender are stirred at 2000 r / min for 30-35s, poured into a polytetrafluoroethylene mold, and cured at 75-80℃ for 2-4h to obtain the cyclodextrin compound modified polyurethane elastomer.

[0026] In step (1), the isocyanate content of the obtained polyurethane prepolymer is determined by titration: the polyurethane prepolymer is added to isopropanol, heated and stirred at 45-55°C to dissolve, and a titration sample solution is obtained; then, the isocyanate content a in the prepolymer is obtained by titration using a toluene solution of bromocresol blue and di-n-butylamine as an indicator.

[0027] The ratio of the polyurethane prepolymer to isopropanol is 3-4 g: 500 mL;

[0028] The volume ratio of the titration sample solution to the toluene solution of di-n-butylamine is 2:0.5-1.5; the concentration of the toluene solution of di-n-butylamine is 0.00166 mol / L; and the titrating reagent used in the titration is 0.1 mol / L dilute hydrochloric acid.

[0029] The volume ratio of bromocresol blue to the titration sample solution is 0.8-1.2 g: 1000 mL;

[0030] The R-value of the polyurethane prepolymer is controlled between 6.4 and 6.6;

[0031] The mass relationship between the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender satisfies the following formula:

[0032] (m1×a%) / 42=R×((m2 / N1)×2+(m3 / N2)×3+(m4 / N3)×2)

[0033] In the formula, m1, m2, m3, and m4 represent the masses of the polyurethane prepolymer, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; N1, N2, and N3 represent the molecular weights of the polyol in component B, the polyol in component B, the polyether 330N polyol, and the diol chain extender, respectively; a represents the isocyanate content of the polyurethane prepolymer; R is the ratio of the total number of isocyanates to the total number of hydroxyl groups, where R = 1.04 to 1.06. The total number of isocyanates includes the number of isocyanates in diisocyanates in component A, and the total number of hydroxyl groups includes the number of hydroxyl groups in the polyol in component B, the polyether 330N polyol, and the diol chain extender.

[0034] Diisocyanate and polyol are mixed, heated to 80-85°C, and stirred for 4-5 hours to obtain viscous polyurethane prepolymer A.

[0035] After the reaction of material A was cooled to room temperature, isopropanol was added as a solvent in a 50°C water bath for 10 minutes to dissolve it, and then the isocyanate content in the prepolymer was obtained by titration.

[0036] Under air-isolated conditions, the viscous polyurethane prepolymer is preheated to 50°C, and the dehydrated B-component polypolyol, polyether 330N polyol and diol chain extender are preheated to 50-70°C.

[0037] The preheated raw material is stirred at 2000 r / min for 30-35 s, poured into a polytetrafluoroethylene mold, and cured at 75-80℃ for 2-4 h to obtain a polyurethane elastomer.

[0038] Beneficial effects

[0039] This invention provides a polyurethane elastomer modified with cyclodextrin compounds. The polyurethane elastomer is composed of two components, A and B. Taking the total mass of raw materials A and B as 100%, the components and their mass fractions in raw material A are as follows: diisocyanate substances 44%–46%, polypolyol 54%–56%; the components and their mass fractions in raw material B are as follows: polypolyol 70%–74%, polyether 330N polyol (330N) 18%–22%, and diol chain extender 4%–8%. The mass fraction settings can ensure the balance of -NCO groups and -OH groups in the polyurethane, giving the polyurethane excellent mechanical properties while ensuring its deformation ability.

[0040] This invention provides a polyurethane elastomer modified with cyclodextrin compounds. In the preparation of the polyurethane elastomer, the diisocyanate in component A contains isocyanate groups at both ends, and the polyol contains hydroxyl groups at both ends. After initial synthesis of the prepolymer, both can be stored for a long time at room temperature. Subsequently, different types of long-chain polymer segments (PTMG, PPG, etc.), crosslinking agents (such as 330N, etc.), and chain extenders (such as BDO, PDO, etc.) can be added according to different production needs. The above raw materials can polymerize at room temperature to produce polyurethane elastomer. After adding cyclodextrin, the elastomer can be dispersed and compounded to obtain the finished product. The method is simple, the experimental formula can be modified according to production needs, and it can be industrialized.

[0041] This invention provides a polyurethane elastomer modified with cyclodextrin compounds. In the preparation of the polyurethane elastomer, the reaction temperature of 80-85°C for prepolymer synthesis is an important condition for successful prepolymerization.

[0042] This invention provides a polyurethane elastomer modified with cyclodextrin compounds. In the preparation of this polyurethane elastomer, maintaining the preheating temperature of the prepolymer at 40–50°C is crucial for its preservation. At temperatures of 50–70°C, the prepolymer will undergo self-polymerization. The prepolymer is end-capped with isocyanate (-NCO) groups. At room temperature, it tends to polymerize with hydroxyl groups in the chain extenders and crosslinking agents of the main raw materials. This polymerization method promotes the forward reaction and accelerates the reaction rate.

[0043] This invention provides a polyurethane elastomer modified with cyclodextrin compounds. In the preparation of the polyurethane elastomer, it is necessary to control the isocyanate content of the prepolymer. Excessive isocyanate content will make it difficult to form the polyurethane structure and will not be able to obtain the polyurethane elastomer. Excessive hydroxyl groups in the main raw materials will reduce the mechanical properties of the polyurethane.

[0044] This invention relates to a cyclodextrin-modified polyurethane and its preparation method, belonging to the field of polymer technology. The main raw material composition and mass fraction of the cyclodextrin-modified polyurethane are as follows: Component A contains 44%–46% diisocyanate and 54%–56% polyol; Component B contains 70%–74% polyol, 18%–22% polyether 330N polyol (330N), and 4%–8% diol chain extender. Auxiliary raw materials include cyclodextrin compounds (α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, etc.), bromocresol blue indicator, and a toluene solution of di-n-butylamine. Cyclodextrin-modified polyurethane is a novel polyurethane material with excellent mechanical properties. The cyclodextrin compounds in the cyclodextrin-modified polyurethane can provide numerous hydroxyl groups, which can form intermolecular hydrogen bonds with the polymer chain, thereby improving the mechanical properties of the polyurethane. This invention also provides a method for preparing polyurethane modified with cyclodextrin compounds. The method involves introducing cyclodextrin compounds into a polyurethane system through filler dispersion and compounding to generate cyclodextrin-modified polyurethane materials. This method is simple, the experimental formulation can be modified according to production needs, and it can be industrialized. Furthermore, compared to inorganic fillers, organic fillers do not have a fixed rigid structure and can be well dispersed in the polyurethane elastomer matrix. Through the interaction of their own active groups with the groups inside the polymer material, they generate intermolecular chain segment frictional motion, thereby dissipating external energy and improving the mechanical properties and impact resistance of the composite material. Attached Figure Description

[0045] Figure 1 Infrared spectra of polyurethane samples (i.e., Examples 1 to 3) with added β-cyclodextrin at mass fractions of 0.5%, 1.0%, and 1.5%;

[0046] Figure 2 The mechanical property test results of polyurethane samples (i.e., Examples 1 to 3) with added β-cyclodextrin at mass fractions of 0.5%, 1.0%, and 1.5% are shown in the figure.

[0047] Figure 3 The results of dynamic thermomechanical analysis of the loss factor of polyurethane samples (i.e., Examples 1 to 3) with added β-cyclodextrin at mass fractions of 0.5%, 1.0%, and 1.5% are shown in the figure. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the present invention.

[0049] Example 1

[0050] In this embodiment, the molecular weight of polytetrahydrofuran is 2000, and the molecular weight of polyether 330N polyol is 4600.

[0051] 225g of diphenylmethane diisocyanate (MDI) and 275g of polytetrahydrofuran were added to a 500mL three-necked glass reactor and heated to 80℃. The raw materials were stirred at a rate of 200r / min to mix them evenly. After reacting for 4 hours, a polyurethane prepolymer was obtained.

[0052] Take 0.3995g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to fully dissolve it. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.86%.

[0053] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0054] Preheat the prepolymer titrated in step (2) to 50°C, and preheat the dehydrated main raw materials polytetrahydrofuran, polyether 330N polyol and 1,4-butanediol to 70°C.

[0055] Add 0.5% β-cyclodextrin, 44g polytetrahydrofuran from step (3), 10g polyether 330N polyol and 3.76g 1,4-butanediol to the container in sequence, then add 44.12g prepolymer and stir the solution at a stirring rate of 2000r / min for 30s; pour it into a polytetrafluoroethylene container and place it in an oven at 80℃ for 2h to cure, thus obtaining polyurethane elastomer.

[0056] The addition of 0.5% β-cyclodextrin means that the mass of the added β-cyclodextrin is 0.5% of the total mass of components A and B;

[0057] The β-cyclodextrin / polyurethane structure is as follows: (dashed lines represent hydrogen bonds)

[0058]

[0059] Example 2

[0060] In this embodiment, the molecular weight of polytetrahydrofuran is 2000, and the molecular weight of polyether 330N polyol is 4750.

[0061] (1) Add 225g of diphenylmethane diisocyanate and 275g of polytetrahydrofuran to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0062] (2) Take 0.3970g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.97%.

[0063] The ratio of the mass (g) of bromocresol blue to the volume (mL) of sodium hydroxide solvent in the bromocresol blue indicator is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0064] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polytetrahydrofuran, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0065] (4) Add 1.0% β-cyclodextrin, 36.61g polytetrahydrofuran from step (3), 10.37g polyether 330N polyol and 3.74g 1,4-butanediol to the container in sequence, and then add 46.55g prepolymer. Stir the solution at a stirring rate of 2000r / min for 30s. Pour it into a polytetrafluoroethylene container and place it in an oven at 80℃ for curing for 4h to obtain polyurethane elastomer.

[0066] The addition of 1.0% β-cyclodextrin means that the mass of the added β-cyclodextrin is 1.0% of the total mass of components A and B.

[0067] Example 3

[0068] In this embodiment, the molecular weight of polytetrahydrofuran is 2000, and the molecular weight of polyether 330N polyol is 4800.

[0069] (1) Add 225g of diphenylmethane diisocyanate and 275g of polytetrahydrofuran to a 100mL three-necked flask, heat to 80℃, stir the raw materials at a rate of 200r / min to mix them evenly, and obtain polyurethane prepolymer after reacting for 4h.

[0070] (2) Take 0.4244g of the prepolymer obtained in step (1) and dissolve it in 50mL of isopropanol. Heat it at 50℃ for 10min to dissolve it completely. Add 4 drops of bromocresol blue indicator and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator. Titrate with 0.1mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 11.55%.

[0071] The ratio of the mass (g) of bromocresol blue in the indicator to the volume (mL) of the solvent sodium hydroxide is 1:1000, and the concentration of sodium hydroxide is 0.1 mol / L.

[0072] (3) Preheat the prepolymer titrated in step (2) to 50°C, and preheat the main raw materials polytetrahydrofuran, polyether 330N polyol and 1,4-butanediol after dehydration to 70°C.

[0073] (4) Add 1.5% β-cyclodextrin, 36.01g polybutanediol from step (3), 9.91g polyether 330N polyol and 3.74g 1,4-butanediol to the container in sequence, and then add 44.15g prepolymer. Stir the solution at a stirring rate of 2000r / min for 30s. Pour it into a polytetrafluoroethylene container and place it in an oven at 80℃ for 2h to cure, thus obtaining polyurethane elastomer.

[0074] The 1.5% β-cyclodextrin refers to the β-cyclodextrin added being 1.5% of the sum of the masses of components A and B.

[0075] The final products prepared in Examples 1-3 were subjected to infrared spectroscopy testing, and the results are as follows: Figure 1 As shown, it can be concluded that, compared to the polyurethane elastomer matrix, the infrared spectrum of the final product in Example 1 at 3300 cm⁻¹ is significantly different. -1 The broad and blunt peaks indicate that they correspond to the positions of intermolecular hydrogen bonds, further suggesting that the cyclodextrin compound forms intermolecular hydrogen bonds with the interior of the polyurethane.

[0076] Tensile tests were performed on the final products prepared in Examples 1-3. The test conditions were as follows: using a 500N mechanical sensor, selecting small test samples of 4mm × 50mm, and conducting the tests at a tensile rate of 200mm / min. The results are as follows. Figure 2 As shown, the mechanical properties of the polyurethane samples after physical blending with cyclodextrin compounds and subsequent heat treatment (approximately 18 MPa for 0.5% β-cyclodextrin, approximately 21 MPa for 1.0% β-cyclodextrin, and approximately 19 MPa for 1.5% β-cyclodextrin) are improved by 50%, 75%, and 58% respectively compared to the mechanical properties of the polyurethane elastomer matrix (approximately 12 MPa). This indicates that the polyurethane modified by physical blending with cyclodextrin compounds can be used as a type of polyurethane elastomer, significantly improving the mechanical properties of polyurethane. Dynamic thermomechanical analysis was performed on the final products prepared in Examples 1-3. The test conditions were controlled at a heating rate of 5 K / min, a frequency of 10 Hz, and a heating temperature range of -75℃ to 100℃. The results are as follows. Figure 3 As shown, the peak value (i.e., glass transition temperature Tg) in Example 2 is larger, indicating that it is more rigid and stronger. The internal filler cyclodextrin and polyurethane system are in full contact and form more hydrogen bonds, which improves the mechanical properties of the polyurethane sample.

[0077] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polyurethane elastomer modified with a cyclodextrin compound, characterized in that: The steps of this method include: Step (1): 225g of diphenylmethane diisocyanate (MDI) and 275g of polytetrahydrofuran were added to a 500mL three-necked glass reactor and heated to 80℃. The raw materials were stirred at a rate of 200r / min to make them evenly mixed. After reacting for 4 hours, polyurethane prepolymer was obtained. Step (2): Dissolve 0.3995g of the polyurethane prepolymer obtained in step (1) in 50mL of isopropanol, heat at 50℃ for 10min to fully dissolve, add 4 drops of bromocresol blue indicator, and then add 25mL of di-n-butylamine toluene solution to completely dissolve the indicator; titrate with 0.1mol / L dilute hydrochloric acid to find that the isocyanate content in the prepolymer is 12.86%; The ratio of the mass of bromocresol blue to the volume of the solvent sodium hydroxide in the bromocresol blue indicator is 1:1000, and the concentration of the sodium hydroxide is 0.1 mol / L. Step (3): Preheat the prepolymer titrated in step (2) to 50°C, and preheat the polytetrahydrofuran, polyether 330N polyol and 1,4-butanediol to 70°C; the molecular weight of polytetrahydrofuran is 2000, and the molecular weight of polyether 330N polyol is 4600. Step (4): Add 0.5% β-cyclodextrin, 44g polytetrahydrofuran from step (3), 10g polyether 330N polyol and 3.76g 1,4-butanediol to the container in sequence, then add 44.12g prepolymer and stir the solution at a stirring rate of 2000r / min for 30s; pour it into a polytetrafluoroethylene container and place it in an oven at 80℃ for 2h to cure, thus obtaining polyurethane elastomer; The β-cyclodextrin with a mass fraction of 0.5% means that the mass of the added β-cyclodextrin is 0.5% of the total mass of components A and B.

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