Transparent hose based on efficient light-aging-resistant material and preparation method of transparent hose

Abstract

The invention relates to modified nano zinc oxide and application thereof, a thermoplastic polyurethane elastomer composition, a thermoplastic polyurethane elastomer sizing material and a transparent hose. The preparation method comprises the following steps: firstly, modifying the surfaces of nano zinc oxide particles by using a silane coupling agent, and then calcining in an air atmosphere to form an inorganic matter coating layer containing Si-O-Si bonds on the surfaces of the nano zinc oxide particles so as to reduce the photocatalytic property of zinc oxide. Secondly, the modified nano-zinc oxide particles and an isocyanate coupling agent are jointly used for the formula of the thermoplastic polyurethane elastomer, so that an effective ultraviolet shielding effect on a polyurethane main chain is achieved, and the yellowing resistance of the thermoplastic polyurethane elastomer is greatly improved. Meanwhile, hydroxyl exists on the surface of the modified nano-zinc oxide, so that cross-linking sites can be formed, and the tensile strength and wear resistance of the thermoplastic polyurethane elastomer can be improved after the modified nano-zinc oxide reacts with an isocyanate coupling agent.

Description

Technical Field

[0001] The invention belongs to the technical field, and particularly relates to a modified nano zinc oxide and application thereof, a thermoplastic polyurethane elastomer composition, a thermoplastic polyurethane elastomer rubber and a transparent hose. Background Art

[0002] Thermoplastic polyurethane elastomer is a multifunctional material between plastic and rubber. Its polymer molecular weight is composed of flexible segments and rigid segments. It has rubber elasticity at low temperatures and can be plasticized and formed after the temperature is increased. Compared with conventional engineering plastics, it has excellent strength, wear resistance and biocompatibility. Its performance can be adjusted within a fairly wide range as needed. The processing methods that can be selected are diverse and its application fields are very wide. Among them, transparent thermoplastic polyurethane materials have more important practical value in the application of pipes than non-transparent thermoplastic polyurethane materials. However, in general, transparent polyurethane reduces the crystallization ability of the hard segment to improve the transparency of the material, resulting in a certain degree of decrease in its mechanical strength. In order to improve the mechanical strength, aromatic isocyanate monomers are selected as the raw materials for synthesizing thermoplastic polyurethane molecular chains, and aromatic structural units are introduced into them. The π electron systems in these aromatic structures easily absorb ultraviolet energy and trigger a series of complex photochemical reactions, resulting in yellowing of thermoplastic polyurethane elastomers, that is, the ultraviolet light aging resistance of thermoplastic polyurethane elastomers is reduced.

[0003] On the other hand, thermoplastic polyurethane elastomers are polar polymer materials, especially polyester polyurethanes containing ester bonds in their molecular chains, which are very easy to absorb moisture from the air during use. After water molecules penetrate into the air, they easily undergo hydrolysis reactions with polar groups such as carbamate bonds, ester bonds, urea bonds, etc., causing degradation of the polymer molecular chains, resulting in a decrease in mechanical strength properties, and thermoplastic polyurethane elastomers are difficult to use as pipes in underwater applications.

[0004] In order to solve the above problems, the prior art proposes a method for inorganic / organic hybrid composite reinforced thermoplastic polyurethane elastomer, by modifying inorganic materials such as nano-silicon dioxide, zinc oxide, cerium oxide, etc., reducing the surface energy of inorganic particles and increasing their compatibility with the thermoplastic polyurethane main chain, thereby obtaining an inorganic / organic hybrid thermoplastic polyurethane elastomer with better mechanical strength, water resistance and aging resistance.

[0005] As for nano zinc oxide, as a green and environmentally friendly light stabilizer, it is non-toxic, highly thermally stable, and has strong ultraviolet light absorption. It can not only increase mechanical strength, water resistance and aging resistance, but also significantly improve resistance to ultraviolet light aging. However, the problem is that it has certain photocatalytic properties and is prone to produce free radicals after absorbing ultraviolet light. If it is directly added to the resin, it will cause photocatalytic destruction of the polymer molecular chain and shorten the service life of the resin. Therefore, it is urgent to find a method for surface modification of nano zinc oxide to avoid the generation of free radicals after absorbing ultraviolet light, which will cause damage to the main chain of the polymer. Summary of the invention

[0006] In view of the defects of the prior art, the present invention proposes a modified nano zinc oxide, which forms a Si-O-Si inorganic coating layer on the surface of the nano zinc oxide to reduce the photocatalytic activity of zinc oxide itself and inhibit the propagation of free radicals, thereby improving the yellowing resistance of the thermoplastic polyurethane elastomer, and at the same time can also improve the mechanical strength, water resistance and aging resistance of the thermoplastic polyurethane elastomer.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, a modified nano zinc oxide is obtained by first surface-modifying the nano zinc oxide with a silane coupling agent and then calcining it.

[0009] The average particle size of the nano zinc oxide is 30 to 80 nm; the silane coupling agent includes at least one siloxane group connected by a Si-O bond and a silane group connected by a Si-C bond; preferably, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH-570).

[0010] The surface modification comprises: mixing the nano zinc oxide and the silane coupling agent at room temperature to 60° C., and then cooling to room temperature and standing for aging for 24-72 hours.

[0011] The calcination treatment comprises: calcining the nano zinc oxide surface-modified by the silane coupling agent in an air atmosphere at a temperature of 500-600° C. for 2-4 hours.

[0012] In the second aspect, the modified nano zinc oxide described above is used as a high-efficiency light-resistant material in thermoplastic polyurethane elastomer.

[0013] In a third aspect, a thermoplastic polyurethane elastomer (TPE) composition comprises: a thermoplastic polyurethane elastomer, the modified nano zinc oxide described above, a coupling agent containing isocyanate, an ultraviolet absorber and an antioxidant.

[0014] Wherein, the thermoplastic polyurethane elastomer is selected from: any one or a combination of polyester thermoplastic polyurethane elastomer, polyether thermoplastic polyurethane elastomer or polycarbonate thermoplastic polyurethane elastomer; preferably, the thermoplastic polyurethane elastomer is selected from: polyether thermoplastic polyurethane elastomer.

[0015] Further, the thermoplastic polyurethane elastomer composition may also include any one or a combination of ethylene propylene diene monomer (EDPM) or polyolefin elastomer (TPO);

[0016] Preferably, the polyolefin elastomer (TPO) is selected from: any one or a combination of ethylene-octene copolymer (POE) synthesized using a metallocene catalyst, thermoplastic dynamic vulcanizate (TPV) prepared by dynamic vulcanization, or ethylene-octene block copolymer (OBC).

[0017] Among them, the coupling agent containing isocyanate is selected from compounds containing at least 2 isocyanate groups per molecule. Preferably, the coupling agent containing isocyanate is selected from aliphatic isocyanate compounds or isocyanate compounds containing Si-O bonds. More preferably, the coupling agent containing isocyanate is selected from isocyanate compounds containing Si-O bonds.

[0018] Further, the coupling agent containing isocyanate is selected from an isocyanate compound containing a Si-O bond obtained by a hydrosilylation reaction of 3-isopropyl-dimethylbenzyl isocyanate (TMI) and a hydrogen-containing linear silane or a hydrogen-containing cyclic silane;

[0019] Preferably, the hydrogen-containing linear silane is methyltri(dimethylsiloxy)silane (T3H), and the hydrogen-containing cyclic silane is tetramethylcyclotetrasiloxane (D4H).

[0020] Wherein, the antioxidant is selected from hindered phenol antioxidants; preferably, the antioxidant is selected from any one or a combination of antioxidant 1010 or antioxidant 1076;

[0021] Among them, the ultraviolet absorber is selected from any one or a combination of benzophenone ultraviolet absorbers, hindered amine ultraviolet absorbers or hindered benzoate ultraviolet absorbers; preferably, the ultraviolet absorber is selected from any one or a combination of two of light stabilizer 531 or light stabilizer 2908.

[0022] Furthermore, the thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 85-95% of thermoplastic polyurethane elastomer, 1-10% of the modified nano zinc oxide described above, 0.1-2% of coupling agent containing isocyanate, 0.1-2% of ultraviolet absorber and 0.1-2% of antioxidant;

[0023] Or, the thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 65-85% of thermoplastic polyurethane elastomer, 5-25% of EPDM rubber, 1-10% of the modified nano zinc oxide mentioned above, 0.1-2% of coupling agent containing isocyanate, 0.1-2% of ultraviolet absorber and 0.1-2% of antioxidant;

[0024] Or, the thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 65-85% of thermoplastic polyurethane elastomer, 5-25% of polyolefin elastomer, 1-10% of the modified nano zinc oxide mentioned above, 0.1-2% of coupling agent containing isocyanate, 0.1-2% of ultraviolet absorber and 0.1-2% of antioxidant;

[0025] Preferably, the amount of the modified nano zinc oxide described above is 3.0-5.0%;

[0026] Preferably, the amount of the isocyanate-containing coupling agent is 0.5-1.5 wt %.

[0027] In a fourth aspect, a thermoplastic polyurethane elastomer compound is prepared by mixing the thermoplastic polyurethane elastomer composition described above and then extruding it.

[0028] Furthermore, the specific steps of extrusion molding after mixing include: first mixing the modified nano zinc oxide with the coupling agent component, then adding other components to mix, and then adding the mixture into an extruder for extrusion and granulation to obtain a thermoplastic polyurethane elastomer rubber compound.

[0029] Preferably, the temperature of the extruder is controlled in multiple stages, and the temperature from the feed port to the die head is set to 100-150°C.

[0030] In a fifth aspect, a transparent hose is prepared by extrusion molding of the thermoplastic polyurethane elastomer compound described above.

[0031] The beneficial effects of the present invention are as follows: the surface of the nano zinc oxide particles is modified by using a silane coupling agent containing Si-C bonds, and then calcined in an air atmosphere, the organic part of the coupling agent is thermally decomposed and an inorganic coating layer containing Si-O-Si bonds is formed on the surface of the nano zinc oxide particles, the photocatalytic activity of the zinc oxide itself is reduced, the propagation of free radicals is inhibited, and the nano zinc oxide is prevented from generating free radicals to destroy the molecular chain of the polymer.

[0032] In the thermoplastic polyurethane elastomer formula, the modified nano zinc oxide particles are used together with the isocyanate coupling agent to form chemical bonds through reaction, thereby enhancing the bonding effect of the nano zinc oxide on the polymer matrix, thereby playing an effective UV shielding role on the polyurethane main chain, thereby greatly improving the resistance to UV light aging and yellowing of the thermoplastic polyurethane elastomer. At the same time, the hydroxyl groups on the surface of the modified nano zinc oxide can form cross-linking sites, which can improve the tensile strength and wear resistance of the thermoplastic polyurethane elastomer after reacting with the isocyanate coupling agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Thermogravimetric curves of KH570 modified nano zinc oxide particles of Example 1 (red line) and Example 2 (blue line).

[0034] Figure 2 Transmission electron micrograph of the nano zinc oxide particle raw material (a) and the modified nano zinc oxide particles prepared in Example 1 (b).

[0035] Figure 3 Schematic diagram of the hydrolysis process of KH570 silane coupling agent (a), the reaction process with the surface of nano zinc oxide particles (b), and the calcination process of KH570 modified nano zinc oxide particles (c). DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] If the specific experimental conditions are not specified in the examples, they are usually based on the conventional conditions in the field or the conditions recommended by the reagent company; the materials, reagents, etc. used in the examples can be purchased through commercial channels unless otherwise specified.

[0039] Example 1

[0040] Preparation of modified nano zinc oxide particles: 62.68 g (0.77 mol) of nano zinc oxide with a purity of 99 wt% and an average particle size of 30 to 80 nm (Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) was dispersed in a mixed solution of 7.92 g of water (0.44 mol) and 25.30 g of anhydrous ethanol (0.55 mol) using a disperser, and 26 g (0.11 mol) of a modifier γ-methacryloxypropyltrimethoxysilane (KH570, Jiangxi Hongbai New Materials Co., Ltd.) was added after stirring at room temperature for 1 hour. The temperature was raised to 50° C. for reaction for 2 hours, and then the temperature was lowered to room temperature for aging for 48 hours. The solution was not stirred during the aging process, and then centrifuged at a speed of 6000 rpm to obtain the modified nano zinc oxide particles after the reaction, and the temperature was further raised to 500° C. in an air atmosphere for further calcination for 3 hours, thereby removing the organic part of the modifier KH570, and at the same time, hydroxyl groups were formed as cross-linking sites under the action of oxygen.

[0041] Example 2

[0042] On the basis of Example 1, the amount of nano zinc oxide was changed to 57.0 g (0.7 mol), and the rest of the preparation method was the same as Example 1.

[0043] Example 3

[0044] On the basis of Example 1, the calcination temperature was changed to 550° C. and 3 hours, and the rest of the preparation method was the same as Example 1.

[0045] Example 4

[0046] Preparation of coupling agent: 50 mL of toluene was used to dissolve 26.86 g (0.1 mol) of the raw material methyl tris (dimethylsiloxy) silane and placed in a three-necked flask, and 0.4 g of Karstedt catalyst, 62.33 g of 3-isopropyl-α, α-dimethylbenzyl isocyanate (TMI, 0.31 mol) and 50 mL of toluene solvent were added dropwise to the flask, and the reaction temperature was controlled to 90°C, and the addition was completed within 1 hour, and the reaction was continued to be maintained at this temperature for 2 hours. After the reaction was completed, the solvent toluene and the remaining unreacted monomers were removed by reduced pressure distillation at 0.01 MPa and 60°C, and finally 85.4 g of colorless liquid was obtained. The chemical structure of the coupling agent prepared in Example 4 is as follows:

[0047]

[0048] Example 5

[0049] Preparation of coupling agent: 24.05g (0.1mol) of raw material tetramethylcyclotetrasiloxane was dissolved in 50mL toluene and placed in a three-necked flask. 0.5g of Karstedt catalyst, 84.53g of 3-isopropyl-α,α-dimethylbenzyl isocyanate (TMI, 0.42mol) and 50mL toluene solvent were added dropwise to the flask. The reaction temperature was controlled to 85°C, and the addition was completed within 1 hour. The reaction was continued at this temperature for 2 hours. After the reaction was completed, the solvent toluene and the remaining unreacted monomers were removed by reduced pressure distillation at 0.01MPa and 60°C, and 105.9g of colorless liquid was finally obtained. The chemical structure of the coupling agent prepared in Example 5 is as follows:

[0050]

[0051] Example 6

[0052] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 93% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 4.0% of the modified nano zinc oxide of Example 1, 1.0% of the coupling agent of Example 4, 1% of the ultraviolet absorber (light stabilizer 531: light stabilizer 2908, compounded in a mass ratio of 3:1), and 1wt% of the antioxidant (antioxidant 1010: antioxidant 1076, compounded in a mass ratio of 3:1).

[0053] Example 7

[0054] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 16% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of the modified nano zinc oxide of Example 2, 1.0% of the coupling agent of Example 4, 1% of an ultraviolet absorber (light stabilizer 531:light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of an antioxidant (antioxidant 1010:antioxidant 1076 compounded in a mass ratio of 3:1).

[0055] Example 8

[0056] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 16% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of the modified nano zinc oxide of Example 3, 1.0% of the coupling agent of Example 4, 1% of an ultraviolet absorber (light stabilizer 531:light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of an antioxidant (antioxidant 1010:antioxidant 1076 compounded in a mass ratio of 3:1).

[0057] Example 9

[0058] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 94% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 3.5% of the modified nano zinc oxide of Example 1, 0.5% of the coupling agent of Example 5, 1% of the ultraviolet absorber (light stabilizer 531: light stabilizer 2908 in a mass ratio of 3:1), and 1wt% of the antioxidant (antioxidant 1010: antioxidant 1076 in a mass ratio of 3:1).

[0059] Example 10

[0060] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 17% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 3.5% of the modified nano zinc oxide of Example 2, 0.5% of the coupling agent of Example 5, 1% of an ultraviolet absorber (light stabilizer 531:light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of an antioxidant (antioxidant 1010:antioxidant 1076 compounded in a mass ratio of 3:1).

[0061] Embodiment 11

[0062] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 17% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 3.5% of modified nano zinc oxide of Example 3, 0.5% of coupling agent of Example 5, 1% of ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0063] Example 12

[0064] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 69% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 24% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of the modified nano zinc oxide of Example 2, 1.0% of the coupling agent of Example 5, 1% of an ultraviolet absorber (light stabilizer 531:light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of an antioxidant (antioxidant 1010:antioxidant 1076 compounded in a mass ratio of 3:1).

[0065] Embodiment 13

[0066] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 93% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 4.0% of the modified nano zinc oxide of Example 1, 1.0% of the coupling agent WANNATE HB-100 biuret isocyanate, 1% of the ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of the antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0067] Embodiment 14

[0068] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 16% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of modified nano zinc oxide of Example 2, 1.0% of coupling agent WANNATE HB-100 biuret isocyanate, 1% of ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0069] Embodiment 15

[0070] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 93% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 4.0% of the modified nano zinc oxide of Example 1, 1.0% of the coupling agent Desmodur N3300 HDI trimer, 1% of the ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of the antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0071] Example 16

[0072] The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 16% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of modified nano zinc oxide of Example 2, 1.0% of coupling agent Desmodur N3300 HDI trimer, 1% of ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0073] Comparative Example 1

[0074] Thermoplastic polyurethane elastomer rubber is composed of the following components in mass percentage: TPU WANTHANE WHT-8190 (Shore hardness 90A) 77%, EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125℃) 16%, unmodified nano zinc oxide (Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) 4.0%, coupling agent of Example 4 1.0%, ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1) 1%, and antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1) 1wt%.

[0075] Comparative Example 2

[0076] Thermoplastic polyurethane elastomer rubber is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 17% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of modified nano zinc oxide of Example 2, 1% of ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0077] Comparative Example 3

[0078] Thermoplastic polyurethane elastomer rubber is composed of the following components in percentage by mass: TPU WANTHANE WHT-8190 (Shore hardness 90A) 79%, EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C) 18%, coupling agent of Example 3 1.0%, ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1) 1%, antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1) 1wt%.

[0079] Comparative Example 4

[0080] Preparation of modified nano zinc oxide particles: No calcination step was performed, and KH570 modified nano zinc oxide was used alone, and centrifuged at 6000 rpm to obtain the particles. The rest of the preparation method was the same as in Example 1.

[0081] Thermoplastic polyurethane elastomer rubber is composed of the following components in percentage by mass: 77% of TPU WANTHANE WHT-8190 (Shore hardness 90A), 16% of EPDM rubber NORDEL 3640 (ethylene segment mass 55wt%, Mooney viscosity 40ML1+4at125°C), 4.0% of modified nano zinc oxide prepared in Comparative Example 4, 1.0% of coupling agent in Example 3, 1% of ultraviolet absorber (light stabilizer 531: light stabilizer 2908 compounded in a mass ratio of 3:1), and 1wt% of antioxidant (antioxidant 1010: antioxidant 1076 compounded in a mass ratio of 3:1).

[0082] Preparation method of thermoplastic polyurethane elastomer rubber compound: weigh the raw materials of each component according to the weight ratio, put the polyether thermoplastic polyurethane elastomer into an oven and bake it at 100°C for 2 hours, add the modified nano zinc oxide and coupling agent components into a mixer in advance and mix them for 5 minutes, then add other components and mix them for another 30 minutes, then add them into a twin-screw extruder for granulation, adjust the feeding speed to 20rpm and the twin-screw speed to 50rpm, and the temperature is controlled in multiple stages, and is set to 110±2, 120±2, 140±2, 145±2, 135±2, 130±2, and 120±2°C from the feeding port to the die head, respectively.

[0083] Test Section

[0084] Thermogravimetric analysis was performed on the KH570 modified nano zinc oxide particles before calcination in Examples 1 and 2. The sampling amount was 20±2 mg. The heating rate of the thermogravimetric analysis was 10°C / min, and the heating range was from room temperature to 800°C. The results are as follows: Figure 1 shown.

[0085] Appearance test of modified nano zinc oxide particles: The samples were prepared on a copper mesh by the dispersion-dropping method, and the appearance of KH570 modified nano zinc oxide particles before calcination and modified nano zinc oxide particles after calcination at 500°C were observed using a transmission electron microscope (TEM). The results are as follows: Figure 2 shown.

[0086] The structural characterization and verification of the coupling agent were performed using H NMR spectroscopy ( 1 H-NMR) and carbon spectrum ( 13 C-NMR) was used to test the coupling agents prepared in Examples 4 and 5. Deuterated acetone was selected as the solvent, and the chemical shifts and the corresponding molecular segments were recorded. The results are listed in Table 1.

[0087] The physical and mechanical properties of thermoplastic polyurethane elastomer compounds include tensile strength and elongation at break, wherein the tensile strength and elongation at break are tested according to ASTM D412.

[0088] Aging resistance test of thermoplastic polyurethane elastomer rubber: Place the rubber in an oven at 113±2℃ and test the residual tensile strength and elongation at break after aging for 168 hours.

[0089] Hydrolysis resistance test of thermoplastic polyurethane elastomer rubber: Place the rubber in a water bath at 80±1℃ and measure the residual tensile strength and elongation at break after 168 hours of immersion.

[0090] The yellowing resistance test of thermoplastic polyurethane elastomer rubber refers to the standard HG / T 3862-2006. The rubber is irradiated by ultraviolet light at 50°C for 12 hours, and the yellowing index YI is tested under standard C light source to obtain the ΔYI before and after ultraviolet light irradiation. ΔYI less than 1.5 is grade 0 without discoloration.

[0091] The wear resistance of thermoplastic polyurethane elastomer compounds is tested according to the method of GB / T 9867-2008, and the wear mass loss values ​​of different samples are calculated accordingly.

[0092] The test data of Examples 6-16 and Comparative Examples 1-4 are recorded in Table 2.

[0093] Results of TGA testing Figure 1It can be seen that the KH570 modified nano zinc oxide prepared in Example 1 (red line) and Example 2 (blue line) after drying at 120°C, began to lose weight significantly when heated to about 150°C, and a weight loss step appeared at about 500°C. The weight loss curve was slightly smoothed and then fell again, and stopped losing weight at about 600°C. From 150°C to 500°C, a small amount of solvent in the KH570 modified nano zinc oxide evaporated, and the organic part of KH570 decomposed and volatilized. From 500°C to 600°C, the dehydration condensation between the silanols in the inorganic part of KH570 caused weight loss, thereby forming a Si-O-Si shell on the surface of the nano zinc oxide (the reaction process is as shown in FIG. Figure 3 As shown). Therefore, the calcination temperature of KH570 modified nano zinc oxide is selected to be 500 to 600°C, so as to ensure that the organic side chain of KH570 is thermally decomposed and oxidized to form Si-OH in an air atmosphere.

[0094] Table 1

[0095]

[0096] The structural characterization of the coupling agents of Examples 4 and 5 in Table 1 shows that the coupling agents contain reactive isocyanate groups -N=C=O. Furthermore, the difference from conventional commercially available aliphatic isocyanate curing agents is that the silane segments are introduced into the coupling agents of Examples 4 and 5 through a hydrosilylation reaction.

[0097] It can be seen from Table 2 that the modified nano zinc oxide combined with the coupling agent containing isocyanate group can significantly improve the yellowing resistance of thermoplastic polyurethane elastomer. After the surface of nano zinc oxide is modified by silane coupling agent, a Si-O-Si layer is formed on its surface, which retains the UV blocking effect of zinc oxide. The residual hydroxyl groups on the surface can further undergo cross-linking reaction with isocyanate, thereby firmly connecting with the main chain of polyurethane and playing a UV shielding role on the main chain, thereby improving the yellowing resistance.

[0098] Table 2

[0099]

[0100] In addition, the modified nano zinc oxide and the coupling agent containing isocyanate groups can also increase the crosslinking degree of thermoplastic polyurethane elastomer, improve tensile strength and wear resistance, and the corresponding elongation is reduced. Due to the presence of hydroxyl groups on the surface of the modified nano zinc oxide, it can be used as a crosslinking site for the molecular chain, thereby improving the aging resistance and hydrolysis resistance of the thermoplastic polyurethane elastomer.

[0101] From the test results of Examples 6-12 and Examples 13-16, Examples 4 and 5 prepared isocyanate coupling agents containing Si-O segments through hydrosilylation reaction. Compared with Examples 13-16 using carbon chain isocyanate coupling agents, Examples 6-12 using coupling agents prepared by Examples 4 and 5 have significantly better yellowing resistance and higher elongation at break under conditions of similar tensile strength. On the one hand, this is because Examples 4 and 5 introduce highly sterically hindered isocyanates into the coupling agents through TMI monomers. Such isocyanates have low activity and are more difficult to react with moisture in the air. On the other hand, the coupling agents prepared by Examples 4 and 5 contain Si-O segments and have poor compatibility with conventional hydrocarbon polymer main chains. Such isocyanate coupling agents containing Si-O segments have poor compatibility with the polyurethane main chain and form a microphase separation structure, which is beneficial to increasing the mechanical strength, aging resistance and hydrolysis resistance of thermoplastic polyurethane elastomers.

[0102] In the formula of Comparative Example 1, unmodified nano zinc oxide is used to replace the modified nano zinc oxide. Due to the limited hydroxyl groups on the surface of zinc oxide, the degree of crosslinking between the zinc oxide and the polyurethane molecular chain is slightly lower than that of Example 7, resulting in a slight decrease in tensile strength and an increase in elongation at break. At the same time, the nano zinc oxide used in Comparative Example 1 has not been coated and modified with a silane coupling agent, and still retains its photocatalytic properties. It is easy to generate free radicals under the action of ultraviolet light to cause the degradation of the polyurethane molecular chain. Therefore, the thermoplastic polyurethane elastomer of Comparative Example 1 has worse yellowing resistance, wear resistance, aging resistance and hydrolysis resistance.

[0103] In the formula of Comparative Example 2, a cross-linkable coupling agent containing isocyanate is not used, and the modified nano zinc oxide is not connected to the molecular chain of polyurethane through isocyanate. The modified nano zinc oxide has poor compatibility with the main chain of carbon-based polyurethane due to the presence of a layer of Si-O-Si shell, and lacks a highly reactive isocyanate coupling agent to couple the two. Therefore, compared with Example 7, the tensile strength of the thermoplastic polyurethane elastomer prepared in Comparative Example 2 is significantly reduced, the elongation at break is significantly higher, and the yellowing resistance, wear resistance, aging resistance and hydrolysis resistance are worse.

[0104] The formula of Comparative Example 3 does not use modified nano zinc oxide, and only uses an isocyanate-containing coupling agent to partially cross-link the polyurethane molecular chains. The lack of nano zinc oxide as an inorganic light stabilizer and a cross-linking site for the elastomer results in that the thermoplastic polyurethane elastomer prepared in Comparative Example 3 has worse yellowing resistance, wear resistance, aging resistance and hydrolysis resistance than Example 7.

[0105] The formulation of Comparative Example 4 only uses KH570 coupling agent to modify the surface of nano zinc oxide, and does not undergo a calcination step. KH570 can only undergo hydrolysis and condensation reaction with the hydroxyl groups on the surface of zinc oxide, but its organic part is not decomposed by calcination, and the silanol groups do not condense at high temperature to form a dense Si-O-Si layer. Therefore, compared with Example 7, the thermoplastic polyurethane elastomer prepared in Comparative Example 4 has worse yellowing resistance, wear resistance, aging resistance and hydrolysis resistance.

[0106] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to perform equivalent replacements on parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A modified nano zinc oxide, characterized in that: The surface of the nanostructured zinc oxide is modified by firstly using a silane coupling agent and then calcined; The average particle size of the nano zinc oxide is 30-80 nm; the silane coupling agent comprises at least one siloxane group connected by a Si-O bond and a silane group connected by a Si-C bond; The surface modification comprises: mixing nano zinc oxide and silane coupling agent at room temperature to 60° C., and then cooling to room temperature and standing for aging for 24-72 hours; The calcination treatment comprises: calcining the nano zinc oxide surface-modified by the silane coupling agent in an air atmosphere at a temperature of 500-600° C. for 2-4 hours.

2. Use of the modified nano zinc oxide as claimed in claim 1 as a high-efficiency light-resistant material in thermoplastic polyurethane elastomer.

3. A thermoplastic polyurethane elastomer composition, characterized in that: The thermoplastic polyurethane elastomer composition comprises: a thermoplastic polyurethane elastomer, the modified nano zinc oxide according to claim 1, a coupling agent containing isocyanate, an ultraviolet absorber and an antioxidant; Wherein, the thermoplastic polyurethane elastomer is selected from: any one or a combination of polyester thermoplastic polyurethane elastomer, polyether thermoplastic polyurethane elastomer or polycarbonate thermoplastic polyurethane elastomer; Wherein, the isocyanate-containing coupling agent is selected from compounds containing at least 2 isocyanate groups per molecule; Wherein, the antioxidant is selected from hindered phenol antioxidants; The ultraviolet absorber is selected from any one or a combination of benzophenone ultraviolet absorbers, hindered amine ultraviolet absorbers or hindered benzoate ultraviolet absorbers.

4. The thermoplastic polyurethane elastomer composition according to claim 3, characterized in that The isocyanate-containing coupling agent is selected from aliphatic isocyanate compounds or isocyanate compounds containing Si—O bonds.

5. The thermoplastic polyurethane elastomer composition according to claim 3, characterized in that: The isocyanate-containing coupling agent is selected from isocyanate compounds containing Si—O bonds.

6. The thermoplastic polyurethane elastomer composition according to claim 3, characterized in that: The thermoplastic polyurethane elastomer composition further comprises any one or a combination of two of EPDM rubber or polyolefin elastomer; Preferably, the polyolefin elastomer is selected from: any one or a combination of ethylene-octene copolymer synthesized using a metallocene catalyst, a thermoplastic dynamic vulcanizate prepared using a dynamic vulcanization method, or an ethylene-octene block copolymer.

7. The thermoplastic polyurethane elastomer composition according to claim 3, characterized in that: The thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 85-95% of thermoplastic polyurethane elastomer, 1-10% of the modified nano zinc oxide described above, 0.1-2% of a coupling agent containing isocyanate, 0.1-2% of an ultraviolet absorber and 0.1-2% of an antioxidant; Or, the thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 65-85% of thermoplastic polyurethane elastomer, 5-25% of EPDM rubber, 1-10% of the modified nano zinc oxide mentioned above, 0.1-2% of coupling agent containing isocyanate, 0.1-2% of ultraviolet absorber and 0.1-2% of antioxidant; Or, the thermoplastic polyurethane elastomer composition is composed of the following components in percentage by mass: 65-85% of thermoplastic polyurethane elastomer, 5-25% of polyolefin elastomer, 1-10% of the modified nano zinc oxide mentioned above, 0.1-2% of coupling agent containing isocyanate, 0.1-2% of ultraviolet absorber and 0.1-2% of antioxidant.

8. A thermoplastic polyurethane elastomer compound, prepared by mixing and then extruding the thermoplastic polyurethane elastomer composition according to any one of claims 3 to 7.

9. The thermoplastic polyurethane elastomer compound according to claim 8, characterized in that: The specific steps of the mixing and extrusion molding include: first mixing the modified nano zinc oxide with the coupling agent component, then adding other components to mix, and then adding the mixture into an extruder for extrusion and granulation.

10. A transparent hose, prepared by extrusion molding of the thermoplastic polyurethane elastomer compound according to any one of claims 8 to 9.

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