Preparation method of ultraviolet resistant thermoplastic polyurethane elastomer

Abstract

The invention belongs to the technical field of polyurethane elastomers, and discloses a method for preparing an ultraviolet-resistant thermoplastic polyurethane elastomer. Epichlorohydrin-modified graphene and benzophenone modifier are reacted to obtain benzophenone-modified graphene; and then reacted with polyol and diisocyanate to obtain an ultraviolet-resistant thermoplastic polyurethane elastomer. The compatibility and dispersibility between graphene and polyurethane elastomer are improved, the bonding strength between the two is enhanced, and the tensile strength and other mechanical properties of the polyurethane elastomer are improved. Benzophenone-modified graphene is chemically grafted into the polyurethane elastomer, so that the benzophenone anti-ultraviolet absorption group is uniformly dispersed in the elastomer matrix, and the ultraviolet resistance and yellowing resistance of the elastomer are significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane elastomers, in particular to a method for preparing an ultraviolet-resistant thermoplastic polyurethane elastomer. Background Art

[0002] Polyurethane elastomers have the advantages of high elasticity and strong shock-absorbing performance, and are widely used in the fields of shoemaking, medical equipment, construction materials, automobile manufacturing, etc. Traditional polyurethane elastomers have poor UV resistance. Under long-term exposure to sunlight and ultraviolet rays, yellowing will occur, affecting the appearance, mechanical and other properties of polyurethane elastomers. Benzophenone ultraviolet absorbers are functional additives that can absorb ultraviolet rays, convert ultraviolet light energy into heat energy and dissipate it, which can improve the material's anti-ultraviolet aging performance; the patent with authorization announcement number CN115304737B discloses a polyurethane elastomer for low-temperature resistant shoe materials and its preparation process, using 2,2'-dihydroxy-4-methoxybenzophenone with UV resistance as a polyol, introducing wear-resistant agents, toughening agents, grafting agents, etc. as additives, and the obtained polyurethane elastomer has good yellowing resistance, low-temperature resistance and other properties. However, the preparation method of the wear-resistant agent and toughening agent in the patent is relatively complicated, and the patent does not improve the hydrophilicity of the polyurethane elastomer.

[0003] Adding nanomaterials such as zinc oxide, titanium dioxide, and graphene to polyurethane elastomers can improve the mechanical strength and other properties of polyurethane elastomers. Graphene has a large specific surface area, high mechanical strength, strong thermal conductivity, and good electrochemical properties, and has important applications in polyurethane and other materials. However, graphene is prone to agglomeration and has poor compatibility with polyurethane, so organic modification of the graphene surface is a research hotspot. Summary of the invention

[0004] The technical problem solved by the invention is to provide a method for preparing an ultraviolet-resistant thermoplastic polyurethane elastomer, thereby solving the problems of low strength and poor ultraviolet-resistant aging performance of the polyurethane elastomer.

[0005] The technical solution adopted by the present invention is: a method for preparing an ultraviolet-resistant thermoplastic polyurethane elastomer:

[0006] Step S1: adding tetrahydrofuran and epichlorohydrin modified graphene into a reaction bottle, adding benzophenone modifier after stirring and dispersing, stirring and reacting, filtering, washing with ethanol, and drying to obtain benzophenone modified graphene;

[0007] Step S2: Add dried and dehydrated polyol and diisocyanate to the reaction bottle, stir and react at 70-85°C for 1.5-3h, then add benzophenone-modified graphene, stir and react for 1-2h, add the product to the preheated mold, demold after standing for 2h, place in a heating box, mature at 110-120°C for 24-36h, cool, and obtain a UV-resistant thermoplastic polyurethane elastomer.

[0008] Preferably, in step S1, the mass ratio of epichlorohydrin-modified graphene to benzophenone modifier is 100:(300-1500).

[0009] Preferably, in step S1, the reaction temperature is 40-65° C., and the reaction time is 6-18 h.

[0010] Preferably, in step S2, the mass of the benzophenone-modified graphene is 0.5-8% of the total mass of the polyol and the diisocyanate.

[0011] Preferably, the polyol is polytetramethylene ether diol, polybutylene adipate diol or polycaprolactone diol; and the diisocyanate is 4,4'-methylenebis(phenyl isocyanate) or toluene-2,4-diisocyanate.

[0012] Preferably, the preparation method of the benzophenone modifier is as follows: acetone or tetrahydrofuran or dichloromethane solvent is added to the reaction bottle, and the mass ratio of 2-hydroxy-4-acrylate-benzophenone (structural formula: ), D, L-cysteine, photoinitiator 2,2-dimethoxy-2-phenylacetophenone, nitrogen gas, irradiation under a 200-400W ultraviolet lamp, stirring reaction for 1-2h, rotary evaporation, washing with saturated sodium chloride solution, and then recrystallization in ethanol to obtain a benzophenone modifier. The structural formula is .

[0013] Preferably, the preparation method of epichlorohydrin modified graphene is: add a dispersion of N,N-dimethylformamide containing graphene oxide to a reaction bottle, add potassium iodide and epichlorohydrin, heat to 100°C, stir and react for 15 hours, filter, wash with N,N-dimethylformamide and water, and dry to obtain epichlorohydrin modified graphene. Potassium iodide is used to activate the hydroxyl and carboxyl groups of graphene oxide, and then react with the chlorine atoms of epichlorohydrin, thereby introducing epoxy groups on the graphene surface.

[0014] The technical effect produced by the present invention is as follows: the present invention carries out a thiol-ene reaction on 2-hydroxy-4-acrylate-benzophenone and D,L-cysteine ​​to obtain a benzophenone modifier; then the amino group of the benzophenone modifier is reacted with the epoxy group of epichlorohydrin-modified graphene to generate active hydroxyl groups and imine groups, thereby chemically modifying the 2-hydroxybenzophenone anti-ultraviolet absorber on the graphene surface to obtain benzophenone-modified graphene.

[0015] The present invention uses polytetramethylene ether diol, polybutylene adipate diol or polycaprolactone diol as diols, and 4,4'-methylenebis(phenyl isocyanate) or toluene-2,4-diisocyanate as diisocyanates to polymerize to obtain an isocyanate-terminated polyurethane prepolymer, the isocyanate groups of which can react with the active hydroxyl groups and imine groups of benzophenone-modified graphene, so that the graphene oxide is grafted onto the polyurethane elastomer, the compatibility and dispersibility between the graphene and the polyurethane elastomer are significantly improved, the bonding strength between the two is enhanced, the reinforcing effect of the graphene is fully exerted, and the tensile strength, elongation at break and tear strength of the polyurethane elastomer are significantly improved.

[0016] The present invention chemically grafts benzophenone-modified graphene into a polyurethane elastomer, so that the benzophenone anti-ultraviolet absorption group is evenly dispersed in the elastomer matrix, significantly improving the anti-ultraviolet and anti-yellowing properties of the elastomer. In addition, the benzophenone modifier contains a hydrophilic carboxyl group, which can reduce the water contact angle of the polyurethane elastomer film material and exhibit good hydrophilic properties. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the invention clearer, the present invention is further described in detail below in conjunction with examples. The content of the present invention will be further described below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments. The raw materials used in the embodiments and comparative examples are commercially available raw materials unless otherwise specified and can be purchased through commercial channels.

[0018] Add 200 mL of N,N-dimethylformamide dispersion containing 0.2 g of graphene oxide into the reaction bottle, add 6 g of potassium iodide and 40 mL of epichlorohydrin, heat to 100 ° C, stir and react for 15 hours, filter, wash with N,N-dimethylformamide and water in turn, and dry to obtain epichlorohydrin-modified graphene.

[0019] Example 1: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0020] (1) Add 250 mL of acetone solvent, 20 g of 2-hydroxy-4-acrylate-benzophenone, 9 g of D,L-cysteine, and 0.14 g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone to a reaction bottle, introduce nitrogen, irradiate under a 400 W ultraviolet lamp, stir and react for 1 h, rotary evaporate, wash with a saturated sodium chloride solution, and then recrystallize in ethanol to obtain a benzophenone modifier. The reaction formula is as follows:

[0021] .

[0022] (2) Add 500 mL of tetrahydrofuran and 1 g of epichlorohydrin-modified graphene to a reaction bottle, stir and disperse, then add 15 g of benzophenone modifier, stir and react at 60°C for 18 h, filter, wash with ethanol, and dry to obtain benzophenone-modified graphene.

[0023] (3) Add 40 mmol of dried and dehydrated polybutylene adipate diol 2000 and 90 mmol of 4,4'-methylenebis(phenyl isocyanate) into the reaction bottle, stir and react at 70°C for 2.5 hours to generate a terminal isocyanate polyurethane prepolymer; then add benzophenone-modified graphene, and control the mass of benzophenone-modified graphene to be 0.5% of the total mass of polycaprolactone diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir and react for 1 hour, add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 110°C for 36 hours, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0024] Example 2: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0025] (1) Add 250 mL of dichloromethane solvent, 20 g of 2-hydroxy-4-acrylate-benzophenone, 12 g of D,L-cysteine, and 0.14 g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone into a reaction bottle, introduce nitrogen, irradiate under a 200 W ultraviolet lamp, stir and react for 2 h, rotary evaporate, wash with a saturated sodium chloride solution, and then recrystallize in ethanol to obtain a benzophenone modifier.

[0026] (2) Add 500 mL of tetrahydrofuran and 1 g of epichlorohydrin-modified graphene to a reaction bottle, stir and disperse, then add 11 g of benzophenone modifier, stir and react at 40°C for 12 h, filter, wash with ethanol, and dry to obtain benzophenone-modified graphene.

[0027] (3) Add 40 mmol of dried and dehydrated polycaprolactone diol 2000 and 100 mmol of toluene-2,4-diisocyanate into the reaction bottle, stir and react at 80°C for 1.5 hours, then add benzophenone-modified graphene, and control the mass of benzophenone-modified graphene to be 2% of the total mass of polybutylene adipate diol 2000 and toluene-2,4-diisocyanate; stir and react for 1 hour, add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 120°C for 24 hours, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0028] Example 3: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0029] (1) Add 250 mL of tetrahydrofuran solvent, 20 g of 2-hydroxy-4-acrylate-benzophenone, 11 g of D,L-cysteine, and 0.08 g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone into a reaction bottle, introduce nitrogen, irradiate under a 400 W ultraviolet lamp, stir and react for 2 h, rotary evaporate, wash with a saturated sodium chloride solution, and then recrystallize in ethanol to obtain a benzophenone modifier.

[0030] (2) Add 300 mL of tetrahydrofuran and 1 g of epichlorohydrin-modified graphene to a reaction bottle, stir and disperse, then add 7 g of benzophenone modifier, stir and react at 65 °C for 6 h, filter, wash with ethanol, and dry to obtain benzophenone-modified graphene.

[0031] (3) Add 40 mmol of dried and dehydrated polytetramethylene ether diol 2000 and 100 mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction bottle, stir and react at 70°C for 3 h, then add benzophenone-modified graphene, and control the mass of benzophenone-modified graphene to be 5% of the total mass of polytetramethylene ether diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir and react for 2 h, add the product into a mold preheated to 110°C, place it for 2 h, then demould it, place it in a heating box, mature it at 120°C for 24 h, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0032] Example 4: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0033] (1) Add 300 mL of tetrahydrofuran solvent, 20 g of 2-hydroxy-4-acrylate-benzophenone, 9 g of D,L-cysteine, and 0.14 g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone into a reaction bottle, introduce nitrogen, irradiate under a 300 W ultraviolet lamp, stir and react for 1 h, rotary evaporate, wash with a saturated sodium chloride solution, and then recrystallize in ethanol to obtain a benzophenone modifier.

[0034] (2) Add 300 mL of tetrahydrofuran and 1 g of epichlorohydrin-modified graphene to a reaction bottle, stir and disperse, then add 3 g of benzophenone modifier, stir and react at 40°C for 12 h, filter, wash with ethanol, and dry to obtain benzophenone-modified graphene.

[0035] (3) Add 40 mmol of dried and dehydrated polytetramethylene glycol 2000 and 90 mmol of toluene-2,4-diisocyanate to the reaction bottle, stir and react at 85°C for 1.5 hours, then add benzophenone-modified graphene, and control the mass of benzophenone-modified graphene to be 8% of the total mass of polytetramethylene glycol 2000 and toluene-2,4-diisocyanate; stir and react for 2 hours, add the product to a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 120°C for 24 hours, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0036] Comparative Example 1: Preparation method of thermoplastic polyurethane elastomer:

[0037] (1) Add 40 mmol of dried and dehydrated polybutylene adipate diol 2000 and 90 mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction bottle, stir and react at 70°C for 2.5 hours to obtain an isocyanate-terminated polyurethane prepolymer; add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 110°C for 36 hours, and cool it to obtain a thermoplastic polyurethane elastomer.

[0038] Comparative Example 2: Preparation method of thermoplastic polyurethane elastomer:

[0039] (1) Add 40 mmol of dried and dehydrated polybutylene adipate diol 2000 and 90 mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction flask, stir and react at 70°C for 2.5 hours, then add graphene oxide, and control the mass of graphene oxide to be 0.5% of the total mass of polybutylene adipate diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir and react for 1 hour, add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 110°C for 36 hours, and cool it to obtain a thermoplastic polyurethane elastomer.

[0040] Comparative Example 3: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0041] (1) Add 40 mmol of dried and dehydrated polybutylene adipate diol 2000 and 90 mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction bottle, stir and react at 70°C for 2.5 hours, then add epichlorohydrin modified graphene, and control the mass of epichlorohydrin modified graphene to be 0.5% of the total mass of polybutylene adipate diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir and react for 1 hour, add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 110°C for 36 hours, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0042] Comparative Example 4: Preparation method of UV-resistant thermoplastic polyurethane elastomer:

[0043] (1) Add 40 mmol of dried and dehydrated polybutylene adipate diol 2000 and 90 mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction bottle, stir at 70°C for 2.5 hours, then add benzophenone modifier, and control the mass of benzophenone modifier to be 0.5% of the total mass of polybutylene adipate diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir and react for 1 hour, add the product into a mold preheated to 110°C, place it for 2 hours, then demould it, place it in a heating box, mature it at 110°C for 36 hours, and cool it to obtain a UV-resistant thermoplastic polyurethane elastomer.

[0044] The cured polyurethane elastomer was placed at room temperature for 7 days. The tensile stress-strain properties were tested according to GB / T 528-2009. The tear strength was tested according to GB / T 529-2008. The test results are shown in the following table.

[0045] Table 1: Test results of various embodiments and comparative examples

[0046]

[0047] As shown in Table 1, compared with Comparative Example 1, the polyurethane elastomers of Examples 1 to 4 are added with benzophenone-modified graphene. When the amino group of the benzophenone modifier reacts with the epoxy group of the epichlorohydrin-modified graphene, active hydroxyl groups and imine groups are generated (the reaction mechanism is ), which can react with the isocyanate group of the terminal isocyanate polyurethane prepolymer, thereby grafting graphene oxide to the polyurethane elastomer, significantly improving the compatibility and dispersibility between graphene and the polyurethane elastomer, enhancing the bonding strength between the two, giving full play to the reinforcing effect of graphene, and significantly improving the tensile strength, elongation at break and tear strength of the polyurethane elastomer.

[0048] Compared with Example 1, Comparative Example 2 adds ordinary unmodified graphene oxide, the hydroxyl activity of which is poor on the surface, the reaction activity with the terminal isocyanate polyurethane prepolymer is low, the compatibility with the polyurethane elastomer is poor, and the reinforcement effect is not good, resulting in the tensile strength, elongation at break and tear strength of the polyurethane elastomer being lower than those in Example 1.

[0049] Comparative Example 3 adds epichlorohydrin-modified graphene. After the graphene oxide is organically modified with epichlorohydrin, it has good compatibility with the polyurethane elastomer. The tensile strength, elongation at break and tear strength of the polyurethane elastomer are higher than those of Comparative Example 1. However, it does not contain active hydroxyl groups, epoxy groups and the like, and is difficult to react with the terminal isocyanate polyurethane prepolymer, resulting in a lower bonding strength between the graphene and the polyurethane elastomer, and lower mechanical properties than those of Example 1.

[0050] In Comparative Example 4, graphene was not added, and the mechanical properties of the polyurethane elastomer were lower than those in Example 1.

[0051] The polyurethane elastomer was placed in a light bulb type yellowing resistance test box and exposed to light for 12 hours with a wavelength of 253nm and a radiation intensity of 0.75 W / m 2 After illumination, a colorimeter is used to detect the L, a, and b values ​​of the sample before and after illumination. The color difference value △E is calculated; the larger the △E, the greater the degree of yellowing and the worse the anti-ultraviolet aging performance.

[0052] △E=(△L 2 +△a 2 +△b 2 ) 1 / 2 △L is the difference in brightness before and after illumination, △a is the difference in red and green before and after illumination, and △b is the difference in yellow and blue before and after illumination.

[0053] Take Example 1 as an example: add 40mmol of dried and dehydrated polybutylene adipate diol 2000 and 90mmol of 4,4'-methylenebis(phenyl isocyanate) into a reaction bottle, stir at 70°C for 2.5h, then add benzophenone-modified graphene, and control the mass of benzophenone-modified graphene to be 0.5% of the total mass of polycaprolactone diol 2000 and 4,4'-methylenebis(phenyl isocyanate); stir the reaction for 1h, add the product to a mold preheated to 110°C, cast into a film, demold after standing for 2h, place in a heating box, mature at 110°C for 36h, cool, and obtain an ultraviolet-resistant thermoplastic polyurethane elastomer film material.

[0054] The water contact angle of the membrane material was tested according to the GB / T 30693-2014 method.

[0055] The test results are shown in the following table.

[0056] Table 2: Test results of various embodiments and comparative examples

[0057]

[0058] As shown in Table 2, the color difference ΔE of the polyurethane elastomers of Examples 1 to 4 is only 0.75-2.74%, which is much lower than that of Comparative Example 1. This is because the 2-hydroxybenzophenone anti-ultraviolet absorption group is modified on the surface of the benzophenone-modified graphene, and the benzophenone-modified graphene is chemically grafted into the polyurethane elastomer, so that the benzophenone anti-ultraviolet absorption group is uniformly dispersed in the elastomer matrix, which significantly improves the anti-ultraviolet and anti-yellowing properties of the elastomer. In addition, the benzophenone modifier contains a hydrophilic carboxyl group, which can reduce the water contact angle of the polyurethane elastomer film material and show good hydrophilic properties.

[0059] The graphene of Comparative Examples 2 and 3 does not contain 2-hydroxybenzophenone anti-ultraviolet absorption groups, the color difference value ΔE of the polyurethane elastomer is large, and the anti-ultraviolet and anti-yellowing properties are poor.

[0060] Comparative Example 4 adds benzophenone modifier, which can also reduce the color difference value ΔE of the polyurethane elastomer, and has good UV resistance and yellowing resistance. It also reduces the water contact angle of the polyurethane elastomer film material, showing good hydrophilic properties.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing an ultraviolet-resistant thermoplastic polyurethane elastomer, characterized in that: The preparation method is: Step S1: adding tetrahydrofuran and epichlorohydrin modified graphene into a reaction bottle, adding benzophenone modifier after stirring and dispersing, stirring and reacting, filtering, washing, and drying to obtain benzophenone modified graphene; Step S2: adding dried and dehydrated polyol and diisocyanate to a reaction bottle, stirring and reacting at 70-85° C. for 1.5-3 hours, then adding benzophenone-modified graphene, stirring and reacting for 1-2 hours, adding the product to a preheated mold, demolding after standing for 2 hours, placing in a heating box, aging at 110-120° C. for 24-36 hours, cooling, and obtaining a UV-resistant thermoplastic polyurethane elastomer; The preparation method of the benzophenone modifier is as follows: adding a solvent, 2-hydroxy-4-acrylate-benzophenone, D,L-cysteine, and a photoinitiator 2,2-dimethoxy-2-phenylacetophenone into a reaction bottle, introducing nitrogen, irradiating under an ultraviolet lamp, stirring for reaction, rotary evaporation, washing with a saturated sodium chloride solution, and then recrystallizing in ethanol to obtain the benzophenone modifier; The mass ratio of the 2-hydroxy-4-acrylate-benzophenone, D,L-cysteine, and 2,2-dimethoxy-2-phenylacetophenone is 100: (45-60): (0.4-0.7); The preparation method of the epichlorohydrin modified graphene is as follows: adding a dispersion of N,N-dimethylformamide containing graphene oxide into a reaction bottle, adding potassium iodide and epichlorohydrin, heating to 100° C., stirring and reacting for 15 hours, filtering, washing, and drying to obtain epichlorohydrin modified graphene.

2. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: In the step S1, the mass ratio of epichlorohydrin modified graphene to benzophenone modifier is 100:(300-1500).

3. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: In the step S1, the reaction temperature is 40-65° C., and the reaction time is 6-18 hours.

4. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: In the step S2, the mass of the benzophenone-modified graphene is 0.5-8% of the total mass of the polyol and the diisocyanate.

5. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: The polyol is polytetramethylene ether diol, polybutylene adipate diol or polycaprolactone diol; the diisocyanate is 4,4'-methylenebis(phenyl isocyanate) or toluene-2,4-diisocyanate.

6. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: In the preparation method of the benzophenone modifier, the solvent is acetone, tetrahydrofuran or dichloromethane.

7. The method for preparing the UV-resistant thermoplastic polyurethane elastomer according to claim 1, characterized in that: In the preparation method of the benzophenone modifier, the power of the ultraviolet lamp is 200-400W, and the reaction time is 1-2h.

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